Optical apparatus, lithographic apparatus,method for setting a target deformation, and production method for a mirror of a lithography system

Abstract

The present invention relates to an optical device (1) for a lithography system (100, 200), having at least one optical element (20) comprising an optical surface (3); and one or more actuators (4) for deforming the optical surface (3). According to the invention, the optical element (2) comprises a strain gauge device (5) for determining the deformation of the optical surface (3), wherein the strain gauge device (5) comprises: - at least one path length device (7) for generating a measurement spectrum (8) of a measurement radiation (9), wherein the path length device (7) comprises a grating device (7a) for the measurement radiation (9) and / or a resonant device (7c) for the measurement radiation (9); and / or - at least one waveguide (11); wherein the at least one waveguide (11) and / or the at least one grating device (7a) and / or the at least one resonant device (7c) are formed from a substrate element (10).

Description

[Technical Field] [Interactive Reference]

[0001] This application claims priority to German Patent Application No. DE 10 2021 205 426.9, filed on May 27, 2021, the entire contents of which are incorporated herein by reference and form part of this invention.

[0002] The present invention relates to an optical device for a lithography system, having at least one optical element having an optical surface and one or more actuators for deforming the optical surface.

[0003] The present invention is further related to a method for setting a target deformation of an optical surface of an optical element for a lithography system by means of one or more actuators.

[0004] Furthermore, the present invention relates to a lithography system, and more particularly to a projection exposure apparatus for semiconductor lithography, the projection exposure apparatus having an illumination system containing a radiation source and an optical unit containing at least one optical element.

[0005] Furthermore, the present invention relates to a method for manufacturing an optical element for a lithography system. [Previous Technology]

[0006] Multiple optical elements are known from the prior art for guiding and shaping radiation in a projection exposure apparatus. In these known optical elements, the surface of the optical element often guides and shapes multiple light waves incident on the optical element. Therefore, precise control of the shape of this surface is particularly advantageous in order to form a precise wavefront with desired characteristics.

[0007] Prior art has disclosed implementations of integrating such optical elements into such optical devices, wherein such optical devices have multiple actuators for generating forces in order to shape the optical surface that interacts with such light waves in a targeted manner.

[0008] According to known techniques, such as modeling, the effect of such actuators on the optical surface is predicted. However, the effects ignored in the modeling may weaken the predictive power of the model.

[0009] According to a drawback of such optical devices in the prior art, it is crucial to maintain the target deformation as accurately as possible to meet the ever-increasing demand for improved accuracy, while the known measurements for precisely setting the target deformation are insufficient. [Summary of the Invention]

[0010] The present invention is based on the purpose of developing an optical device that avoids the disadvantages of conventional technology, and in particular facilitates the precise shaping or precise setting of the target deformation of the optical surface.

[0011] According to the present invention, this object is achieved by an optical device having a plurality of features as described in claim 1.

[0012] The present invention is further based on the purpose of developing a method for setting the target deformation of an optical surface, avoiding the disadvantages of the prior art, and in particular facilitating the accurate and reliable shaping or precise setting of the target deformation of the optical surface.

[0013] This objective is achieved by a method having features as described in claim 17.

[0014] The present invention is also based on the purpose of developing a lithography system that avoids the disadvantages of conventional techniques, and in particular, it is advantageous for forming multiple precisely shaped wavefronts of a projected radiation.

[0015] According to the present invention, this object is achieved by a lithography system having the features described in claim 29.

[0016] In the optical device for a lithography system according to the present invention, at least one optical element having an optical surface and one or more actuators for deforming the optical surface are provided. The optical element includes a strain gauge device for determining the optical surface, wherein the strain gauge device includes...

[0016] - At least one path length device for generating a measurement spectrum of a measurement radiation, wherein the path length device includes a grating device for the measurement radiation and / or a resonant device for the measurement radiation, and / or

[0016] - At least one waveguide, of which

[0016] - The at least one waveguide and / or the at least one grating device and / or the at least one resonant device are formed from the substrate elements.

[0017] Within the scope of this invention, a strain system can also be understood to represent a contraction and / or a compression.

[0018] The strain gauge device includes at least one path length device for generating a measurement spectrum of a measurement radiation, wherein the path length device includes a grating device for the measurement radiation and / or a resonant device for the measurement radiation, wherein the at least one grating device and / or the at least one resonant device is formed from the substrate element.

[0019] The strain gauge device includes at least one waveguide, wherein the at least one waveguide is formed from the substrate element.

[0020] An advantage provided by the optical device according to the present invention is that the deformation of the optical surface can be monitored by the strain gauge device. Hereinafter, the strain gauge device is part of the optical element, and therefore information about the deformation of the optical surface can be collected and measured by the strain gauge device in the effective space and / or functional area close to the optical element, since the optical surface is part of the optical element.

[0021] In addition, the mechanical deformation of the optical surface is used to shape the optical surface and / or set a target deformation.

[0022] Monitoring the actual deformation of the optical surface or information about the actual deformation of the optical surface provides knowledge about the shape of the optical surface, and thus provides knowledge about its influence on the light or radiation guided and shaped by the optical surface, and thus at least indirectly provides information about the effect of the actuators configured to deform the optical surface at the optical surface.

[0023] In particular, the strain gauge device is designed such that the strain is measured within the optical surface and / or at a plurality of defined locations on the optical surface.

[0024] The strain gauge device includes a structure that is directly applied to or inside at least one optical element and / or optical unit, and can be used as a sensor to read an actual state of deformation of the optical element in terms of its optical effect. In particular, such structures allow for input coupling and / or guidance of light to the waveguides.

[0025] For example, at least one actuator may be in the form of a piezoelectric and / or electrostrictive actuator.

[0026] In an advantageous development of the optical device according to the invention, the strain gauge device is provided to determine a strain in at least one measurement region of the optical element, the at least one measurement region being configured such that a strain in the measurement region is determined by a deformation of the optical surface.

[0027] The relationship between the deformation of the optical surface and the strain of the measurement area should be as unique as possible, preferably a reciprocal relationship, such that the strain of the measurement area is determined by the deformation of the optical surface. Therefore, it is advantageous if the at least one measurement area is disposed in and / or on the optical element, such that a reciprocal relationship occurs. In this way, it is possible to determine particularly reliable information about the actual deformation of the optical surface from the strain of the at least one measurement area.

[0028] To achieve this, in the described embodiments, the strain gauge device is provided configured to determine the strain in the at least one measurement region. Therefore, the above embodiments generate an information flow regarding the actual deformation of the optical surface, which begins at the optical surface and reaches the strain in the measurement region, and from the strain in the measurement region to the strain gauge device. The reverse sequence generates an information flow regarding the deformation of the optical surface to be set, which begins at the at least one actuator and enters the deformation of the optical surface, preferably via the strain in the measurement region.

[0029] Within the scope of this invention, the measurement area should be understood as the area of ​​the optical device, in which the actual strain, particularly the change of the actual strain relative to an original strain, can be measured with sufficient accuracy.

[0030] In an advantageous development of the optical device according to the invention, the strain gauge device is provided to be at least partially disposed within the at least one measurement area.

[0031] It is advantageous for the strain gauge device to be configured in at least a partial solid configuration (preferably a complete solid configuration) within the at least one measurement region, because the strain and / or deformation in the at least one measurement region can be transferred to the strain gauge device by mechanical coupling. This is advantageous for providing immediate and direct access to the strain that is actually present throughout the measurement region to be inspected.

[0032] Alternatively or additionally, the strain gauge device is provided to be disposed at a distance from the measurement area and not configured to make physical contact with the measurement area. For example, the strain gauge device may include a camera that determines the strain of the measurement area by means of changes in the outer contour of the measurement area when the measurement area is strained. This strain gauge device will not be at least partially disposed within the at least one measurement area, but will ensure the flow of information related to the strain of the measurement area.

[0033] The optical element is provided to include a continuous and / or integrally formed optical surface, and in particular, the optical element is not a field mirror. Therefore, the optical surface can at least approximately form a freeform surface.

[0034] According to an embodiment of the present invention, the strain gauge device includes at least one path length device for generating a measurement spectrum of a measurement radiation.

[0035] To this end, the path length device is provided to display or have a unique strain-dependent reflection spectrum and / or a unique strain-dependent transmission spectrum.

[0036] If the strain gauge device is configured to generate a measurement spectrum of a measured radiation, this facilitates particularly precise and efficient signal evaluation within the strain gauge device. Firstly, information items or desired information can be recorded, especially through the particularly good transmission of a measured radiation; secondly, the spectrum or multiple spectral signals are ideally suited for accurate determination by measurement.

[0037] Particularly advantageous is that if the path length device provided for this purpose is configured to differently form multiple path lengths of different components of the measured radiation and / or to form multiple path differences between the different components of the measured radiation, it is preferable that some components of the measured radiation traveling different path lengths subsequently interfere. In this document and within the scope of the invention, the term path length device should not be construed as being limited to this effect only.

[0038] For example, the path length device can be formed by the change in refractive index within one of the optical media through which the measured radiation is processed. This produces a different optical path length for different components of the measured radiation.

[0039] The measuring radiation used within the scope of the present invention has a wavelength between 100 nm and 10000 nm, preferably between 300 nm and 3000 nm, and more preferably between 1500 nm and 1600 nm.

[0040] The at least one measurement spectrum is provided to have a wavelength of 100 nm to 10000 nm, preferably between 300 nm and 3000 nm, and more preferably between 1500 nm and 1600 nm.

[0041] The strain gauge device is provided to have a readout device for optical readout of the path length device.

[0042] The readout device is provided to include at least the following components:

[0042] - A measuring radiation source for generating the measuring radiation, which is radiated onto the path length device via the waveguide;

[0042] - A detection device, particularly a spectroscopic instrument, by means of the detection device, detects the measured radiation emitted and / or reflected by the at least one path length device and converts it into an electronic signal; and

[0042] - An evaluation computing device for performing multiple digital calculations.

[0043] In this case, the detection device can be configured to implement various different readout methods. For example, the detection device can be configured to perform spectroscopy and interferometry.

[0044] The spectroscopic method includes, in particular, conventional spectroscopic methods, dual-chamber spectroscopic methods and / or Pound-Drever-Hall locking methods.

[0045] The above-described readout method is provided for reading the measurement spectrum of the path length device and for converting the latter into a preferred digital electronic signal.

[0046] Alternatively or additionally, the readout device may include at least the following components:

[0046] - A tunable narrowband measurement radiation source for generating the measurement radiation in various narrowband wavelength ranges, thus enabling sweeping or scanning of a preferred wide wavelength band, the measurement radiation being radiated onto the path-length device via the waveguide; and

[0046] - A detection device, particularly a light-emitting diode, by means of which the measuring radiation emitted and / or reflected by at least one path-length device can be detected in a time-resolved manner and converted into an electronic signal; and

[0046] - An evaluation computing device for performing multiple digital calculations.

[0047] In addition, the readout device can be configured to implement an interferometric measurement method using an unbalanced Mach-Zehnder interferometer.

[0048] The optical and / or electronic devices required for this purpose can be implemented on both the optical surface of the optical element to be measured (preferably as a photonic integrated circuit) and / or as an external structure.

[0049] A further advantage of a path length device is that the optical path length can be affected by the geometry of the strain gauge device. In particular, it can provide a difference in the path length traversed by the component of the measured radiation when the path length device is tightened. Therefore, it is possible to draw conclusions about the existence of strain.

[0050] According to an embodiment of the present invention, the path length device includes a grating device for the measurement of radiation.

[0051] The path length difference between the different components of the measured radiation can be advantageously generated in a systematic and simple manner by means of the grating device (especially a grating).

[0052] In particular, the grating device can be a line grating, preferably formed by a change in refractive index. By systematically arranging regions with a high refractive index and a low refractive index in the form of intersecting lines, which is known as a line grating, a path length difference of many individual subcomponents of the measurement radiation can be obtained along a range of the grating device. In fact, not only are the two major halves of the measurement radiation exposed to different path lengths, but the measurement radiation is also divided into many components according to the grating length and the grating period. These components are allocated to two sets of refractive indices, thus producing two components of the measurement radiation with different path lengths.

[0053] According to an embodiment of the present invention, the path length device includes a resonant device for the measured radiation.

[0054] The advantage of a resonant device as a path length device is that the resonant frequency of the resonant device can depend on a geometric range of the resonant device. If the geometric range of the resonant device changes due to the strain of the measuring device, a particularly accurate conclusion about the actual strain can be drawn.

[0055] In an advantageous development of the optical device according to the invention, the optical element includes a substrate element on which the optical surface is disposed and / or formed, and the strain gauge device is at least partially disposed in and / or on the substrate element.

[0056] The substrate element may be formed as a solid and / or single body of the optical element, preferably made of glass and / or silicon oxide.

[0057] It is advantageous to find the optical elements of the substrate element below the optical surface, because the optical surface is advantageously stable against torsion and / or vibration.

[0058] In this case, it is particularly advantageous if the strain gauge device is at least partially disposed within and / or on the substrate element, and if the latter is mechanically tightly coupled to the optical surface.

[0059] For example, the optical surface is provided to be a pattern and / or a coating layer formed on the substrate element, and / or formed by the substrate element.

[0060] Therefore, the strain gauge device for measuring the strain of one of the substrate elements allows for accurate and reliable conclusions about the deformation of one of the optical surfaces.

[0061] If the strain gauge device is contained within the substrate element, the former can be mechanically coupled to the substrate element in a particularly tight manner, thus allowing for particularly accurate measurement of the strain of the substrate element. In contrast, the configuration of the strain gauge device on the substrate element is advantageous because it does not require altering the structure of the substrate element or the mechanical stability of the substrate element used to accommodate the strain gauge device, which is instead located outside the substrate element.

[0062] Conversely, it is advantageous to place the strain gauge device part within the substrate element, that is, some components of the strain gauge device are located outside the substrate element, so only some relevant components of the strain gauge device must be disposed in or on the substrate element.

[0063] It is advantageous to completely house the strain gauge device within or on the substrate element, as this can produce a particularly compact structure for one of the optical devices.

[0064] As an addition to or alternative to the path length device, the strain gauge device is provided to include a plurality of further active sensor structures.

[0065] In particular, the active sensor structure is provided as a chamber for measuring radiation, and a mode structure of the chamber is variable due to a strain in the measurement region.

[0066] According to an embodiment of the present invention, the path length device includes at least one waveguide.

[0067] The presence of at least one waveguide helps to provide the measurement radiation to the at least one path length device.

[0068] In this document, the at least one waveguide may be provided to include an optical fiber, an optical channel, and / or, in a purely embodiment, a free beam guide for measuring radiation. In this document, the embodiment of the path length device as a grating device is advantageous because the grating device can be formed as a refractive index change in the waveguide, thereby producing a particularly compact structure for one of the strain gauge devices. In particular, such an embodiment allows the path length device or the grating device to be disposed in a relevant region of the optical element, while the measuring radiation is transmitted via the at least one waveguide between such relevant regions of the optical element.

[0069] For example, the waveguide may include an optical channel that is monolithically integrated into the substrate element of the optical element.

[0070] Provides a plurality of path length devices configured along a single waveguide and / or a branch waveguide network.

[0071] In an advantageous development of the optical device according to the invention, the strain gauge device is provided to include a plurality of path length devices, and the at least one waveguide preferably sequentially guides the measurement radiation to the plurality of path length devices.

[0072] Such an embodiment facilitates the monitoring of multiple relevant regions of the optical element using only one waveguide.

[0073] The plurality of path length devices are provided to form a plurality of grating devices.

[0074] In an advantageous development of the optical device according to the invention, the at least one grating device is provided in the form of a fiber Bragg grating.

[0075] It is advantageous to form the at least one grating device as a fiber Bragg grating because strain changes in the grating device can be monitored particularly advantageously via the fiber Bragg grating. If the grating device is strained, a grating period of the fiber Bragg grating is changed, and therefore, the back-reflecting fiber bandwidth, in particular a center wavelength of the back-reflecting fiber bandwidth, changes based on the strain experienced by the fiber Bragg grating.

[0076] Furthermore, a notch in the transmission spectrum of the measured radiation transmitted through the fiber Bragg grating varies due to the strain of the fiber Bragg grating and varies based on the strain of the fiber Bragg grating. The notch is formed at the center wavelength position of the fiber bandwidth and is consistent with the width of the fiber bandwidth.

[0077] Furthermore, determining and analyzing the relative position of the reflection center wavelength and / or the relative position of the notch in the transmission spectrum allows for the determination of the grating period variation of the fiber Bragg grating and thus the mechanical and / or geometric strain experienced by the fiber Bragg grating.

[0078] The path length device is provided to form a simple fiber Bragg grating as along the waveguide.

[0079] Furthermore, the path length device has a complex geometry. In particular, the path length is formed as a π fiber Bragg grating and / or formed as a combination with the resonant device, especially with at least one ring resonator.

[0080] In addition, the path length device can be configured as a combination of a fiber Bragg grating and / or a π fiber Bragg grating and / or a two-dimensional resonant device and / or a three-dimensional resonant device.

[0081] In particular, the path length device is configured to selectively reflect and / or actively mimic measured radiation within a specific wavelength range and / or filter out said measured radiation within a specific wavelength range from the measured transmission spectrum.

[0082] In addition, the path length device is formed in such a way that the strain change and / or temperature change cause changes in the reflection and / or transmission spectrum.

[0083] The path length device is connected to a readout device (especially a spectrometer) via an optical connection (especially via a waveguide).

[0084] Therefore, the structure in the strain gauge device is provided in such a way that the refractive index change (in particular in the form of a Bragg grating and / or a fiber Bragg grating) is introduced into the waveguide along the propagation direction of the measured radiation.

[0085] The optical fiber having a Bragg grating is bonded to or into the optical element.

[0086] It is possible to fuse the optical fiber having the fiber Bragg grating into or onto the optical element, particularly into or onto the substrate element, by means of a low melting point welding glass and / or direct bonding technology.

[0087] The multiple fiber Bragg grating sensors used to measure the strain are well known in the art for monitoring purposes such as wind turbines, pipelines, bridges and buildings.

[0088] In an advantageous development of the optical device according to the invention, the at least one waveguide is provided in the form of an optical fiber.

[0089] These optical fibers, acting as waveguides, offer the advantage of reliable transmission of coupled radiation even when bent. These optical fibers are bent, particularly under strain caused by at least one actuator.

[0090] In addition, these optical fibers have low light loss or high light guiding efficiency in the light guiding range, and high quality optical fibers can be obtained at low cost.

[0091] At least one waveguide is provided to form an optical channel, in which the measurement radiation undergoes total internal reflection at each wall of the optical channel, resulting in guiding multiple light waves of the measurement radiation within the waveguide.

[0092] In an advantageous development of the optical device according to the invention, at least one waveguide and / or at least one grating device and / or at least one resonant device are provided to be formed from the substrate element.

[0093] An embodiment of the path length device of the substrate element, particularly an embodiment of at least one grating device and / or at least one resonant device, is advantageous because a tight mechanical coupling between the path length device and the substrate element can be directly obtained by this monolithic structure. Therefore, a strain of the substrate element can be advantageously determined accurately and reliably.

[0094] In this document, it is more advantageous if the at least one waveguide system is formed from the substrate element, preferably monolithically. This results in a particularly compact structure for the strain gauge device and / or the optical element.

[0095] The waveguide and / or the at least one path length device are monolithically manufactured in a special layer of the optical element.

[0096] In addition, the at least one waveguide and / or the at least one path length device are provided to be monolithically manufactured in the substrate element of the optical element.

[0097] Regarding adhesive-based integration methods, several monolithic manufacturing methods have advantages. In particular, when the adhesive is used for the long-term stability and function of the optical device, leakage, flow, volume change, and degassing of the adhesive can be avoided, especially on the optical surface if there is an optical coating, particularly in a lithography system.

[0098] Another advantage of the monolithic fabrication of at least one component of the strain gauge device is that it avoids stresses that may form when various materials interact, such as the material of the substrate element, the adhesive, and the optical fiber. For example, if the materials used have different coefficients of thermal expansion, such stresses may occur due to temperature changes during the interaction.

[0099] For example, such stresses may cause errors in the determined values ​​of the strain and / or the deformation of the optical surface in the measurement area. Furthermore, monolithic integration of the strain gauge device or the path length device in the waveguide and / or optical elements is advantageous because putting fewer different materials together reduces the possible stress and provides a more uniform coefficient of thermal expansion.

[0100] Furthermore, since the adhesive is removed, there will be no problems caused by the adhesive.

[0101] For example, from the production of such photonic integrated circuits and / or the writing of such waveguides in glass or glass-ceramic substrates, there are known to be a number of possible methods for monolithic fabrication.

[0102] To form some components of the strain gauge device and / or the at least one waveguide and / or the at least one path length device, these components can be manufactured by direct writing with a localized change in refractive index. Specifically, the localized change in refractive index can be formed by:

[0102] - A write radiation, such as in a UV spectral range and / or using an ultrashort laser pulse, preferably having a pulse duration of several femtoseconds; and / or

[0102] - Multiple ion beams; and / or

[0102] - Multiple electron beams.

[0103] Furthermore, in the manufacture of such components of the strain gauge device, for example, lithography techniques such as exposure, development, etching or material application can be used to apply the at least one waveguide and / or the at least one path length device near the surface.

[0104] While these lithography techniques are particularly suitable for various regions close to the surface, these direct writing methods provide options for the at least one waveguide and / or the at least one path length device constructed in three dimensions, particularly for monolithic fabrication. In particular, this can be performed far below a surface of the optical element, especially below the optical surface.

[0105] The structures, such as the at least one waveguide and / or the at least one path length device, are manufactured at a depth greater than 10 μm, preferably greater than 100 μm, more preferably greater than 1 mm, and particularly preferably greater than 10 mm.

[0106] For a strain measurement near the surface, the structure, such as the at least one waveguide and / or the at least one path length device, can be fabricated at a depth between 5 μm and 20 μm, preferably 10 μm.

[0107] The substrate element is provided to be formed of SiO2-TiO2 glass. This glass has a very low coefficient of thermal expansion, and is therefore particularly suitable for fabricating the substrate element below the optical surface.

[0108] In an advantageous development of the optical device according to the present invention, a plurality of measurement regions of the strain gauge device may be formed at different depths in the substrate element and / or at least one of the plurality of measurement regions may be disposed in a strain neutral plane of the substrate element.

[0109] This strain gauge device has only one measurement area.

[0110] Measuring the strain coefficient of the substrate element at different depths allows for particularly accurate conclusions about the actual deformation and / or strain present on the substrate element as a whole. This allows for particularly accurate prediction of the deformation actually experienced by the surface.

[0111] In order to separate the effects of mechanical strain caused by the at least one actuator and / or strain and deformation caused by external influences (e.g., temperature changes), it is advantageous that at least one of the plurality of measurement regions of the strain gauge device is disposed in the strain neutral plane of the substrate element. Under isotropic expansion that may be caused by, for example, temperature changes, the strain neutral plane undergoes expansion, while remaining unchanged when actuated by the at least one actuator.

[0112] The strain gauge device is provided to be configured to measure temperature changes and / or a temperature of the at least one measurement area.

[0113] The grating device is provided to have a temperature-dependent center wavelength or Bragg wavelength λB.

[0114] According to formula (1), the center wavelength is twice the product of the grating period Λ and the effective refractive index neff of the grating device.

[0114] λB=2neffΛ (1)

[0115] Equation (2) describes the situation where the center wavelength or Bragg wavelength λB is under strain, or the situation where the length l of the grating device is changed due to the strain, and the situation where the temperature T changes by a certain ΔT.

[0115]

[0116] It is obvious that even without strain caused by a force, that is, when Δl=0, the center wavelength or Bragg wavelength λB will change due to a change in temperature T, ΔT.

[0117] In the context of this invention, the strain-neutral plane should be understood to refer to a portion of the substrate element formed by a plurality of strain-neutral optical fibers. In particular, the term plane may also refer to a strain-neutral segment of the substrate element that is bent in space.

[0118] To separate the measurement of strain from the measurement of temperature, the measurement areas and / or the path length devices can be provided at different depths in the optical element. In particular, the strain gauge device can be designed to separate mechanical strain from thermal expansion, wherein the measurement areas or the active sensor structures are partially close to and partially away from the strain neutral plane of the strain neutral fiber or the optical element.

[0119] The following manufacturing method can be used for the purpose of configuring or forming such active sensor structures or such path length devices or such measurement areas near the strain neutral plane.

[0120] The waveguide and / or the path length device may be formed or attached to a greater depth in the optical element or the substrate element by means of a connection method, particularly close to the strain neutral surface, for example, optical contact bonding, particularly laser welding, adhesive bonding and / or connection with a low melting point glass, particularly a welding glass, since the waveguide or the path length device or the measurement area are formed after the two partial optical units are connected by the connection method.

[0121] If such active sensor structures are formed near the surface, they can also be formed by lithography, such as the method used in the fabrication of multiple photonic integrated wafers.

[0122] Furthermore, the active sensor structures can be directly written into the optical surface and / or the substrate element using high-energy, preferably pulsed light and / or multiple particle beams, to form the active sensor structures, particularly the waveguides, the path length devices, or their measurement regions. This is advantageous because of the direct monolithic form, thus creating a favorable tight mechanical coupling between the substrate element and the measurement region. Moreover, the path length device can be generated without significantly altering the mechanical performance of the substrate element beneath the optical surface.

[0123] In an advantageous development of the optical device according to the invention, in order to set a target strain of the measurement region by means of the at least one actuator, a closed-loop control device having a closed loop can be provided, wherein an actual strain of the measurement region determined by the strain gauge device is taken into account.

[0124] By using the closed loop in the closed loop control device, by taking into account information about the actual strain determined by the strain gauge device, the target strain in the measurement area can be achieved particularly reliably and accurately.

[0125] In this case, the coupling of the at least one waveguide or the at least one waveguide structure to a radiation source and / or a readout device, particularly a readout electronic device, such as in the form of a spectrometer, can be achieved by means of a free-beam optical unit, multiple glass structures for fusing the optical fiber to the substrate element, bonding a mechanical fiber holder to the optical element, particularly the substrate element and / or a photonic integrated wafer having a light source and / or a detector.

[0126] In an advantageous development of the optical device according to the invention, the closed-loop control device may be provided, which is configured to set the target deformation of the optical surface by means of the at least one actuator, while taking into account the actual strain of the measurement area determined by the strain gauge device.

[0127] Based on the accurate determination of the actual strain in the measurement area, the actual deformation of the optical surface can be inferred. For example, a modeling based on a finite element method can be provided for this purpose.

[0128] In this case, it is advantageous that the closed-loop control device is configured to set the target deformation of the optical surface by the at least one actuator based on the actual strain of the determined measurement area, wherein it can take into account a modeled relationship between the determined actual strain and the actual deformation of the actual optical surface.

[0129] For example, when a measurement area is located at a relative position to the optical surface, this modeling relationship can consist of the actual deformation of the optical surface that is directly identical to the actual strain of the measurement area.

[0130] The measurement area may be provided at least partially disposed in or on the optical surface, because this creates an advantageous identical relationship between the actual strain determined in the measurement area and the actual deformation of the optical surface, so that the target deformation system of the optical surface can be particularly easily set by the closed-loop control device and the at least one actuator based on the actual strain system of the determined measurement area.

[0131] The strain gauge device can be configured to monitor the shape behavior of the optical element. To this end, the strain of the measurement region to be measured can be provided, and an appropriate force can be provided to adjust the strain of the measurement region to a target value generated by the actuators in a closed loop.

[0132] In an advantageous development of the optical device according to the invention, the closed-loop control device may be provided to correct the deviation between the actual deformation and the target deformation of the optical surface caused by at least one temperature and / or strain.

[0133] In order to ensure and / or improve the performance of the optical element, it is advantageous for the optical surface to have a constant shape that varies with time as the target deformation pattern changes, especially during the intended use.

[0134] Advantageously, the deviation from the target deformation can be corrected by the optical device. During the intended use period, this deviation may occur due to mechanical deformation and / or temperature changes, for example, within the assembly range.

[0135] Advantageously, the closed-loop control device is configured to correct this deviation by means of the at least one actuator, thereby producing an advantageous high efficiency of one of the optical surfaces.

[0136] The strain gauge device can be implemented in such a way that, in addition to the strain, a temperature can also be measured in a plurality of measurement regions of the optical element.

[0137] In the case of the fiber Bragg grating known in the art, the changes in strain and temperature both lead to a change in the reflection and / or transmission measurement spectrum.

[0138] In order to separate the strain from the temperature, at least two path length devices can be provided closely configured together, the path length devices having different geometries such that the effect of a temperature change on the two path length devices is different from that of the strain.

[0139] To separate strain from temperature, at least two path-length devices can be closely configured together, having different strong mechanical couplings to the substrate element of the optical element. Therefore, the effect of strain on the two path-length devices is different.

[0140] To separate the strain from the temperature, a path length device can be placed in a birefringent waveguide, particularly in a polarization-maintaining fiber. In this case, the strain and temperature can be separated by a single readout in both polarization directions.

[0141] By means of this polarization-maintaining fiber, the effects of a temperature change on the deformation of the optical surface and the effects of strain and / or deformation of the optical element on the deformation of the optical surface can be separated or decoupled. This facilitates more precise and accurate control over the deformation or shaping of the optical surface, since the various factors affecting the shape of the optical surface can be treated and / or removed individually.

[0142] Separation of the effects caused by temperature is particularly advantageous because temperature variations on the optical surface, especially during use in EUV lithography systems, can represent one of the greatest disturbances related to deformation of the optical element. In particular, the temperature of the optical surface or the optical element can vary between 20°C and 40°C during operation.

[0143] In order to separate the temperature from the strain, multiple path length devices and multiple individual temperature sensors can be provided, through which multiple strain signals of the path length devices can be temperature corrected.

[0144] In order to separate the strain from the temperature, for example in the case of a ring resonator, a symmetry of the path length device that is damaged due to the strain can be provided, while maintaining the symmetry under a temperature change. Thus, the two measurements can be separated.

[0145] To separate the strain from the temperature, a plurality of path length devices can be arranged within the optical element, such that some path length devices are located close to the strain-neutral fiber, particularly the strain-neutral plane, while others are located away from the strain-neutral fiber. The signals from the path length devices close to the strain-neutral fiber are primarily affected by temperature changes, while the signals from the path length devices located away from the strain-neutral fiber are affected by both temperature and strain changes.

[0146] The effects of temperature and / or strain can be separated by a model or calibration, and both quantities can be determined. In particular, this method can also be used if it is necessary to determine information about temperature and strain, or simply to determine at least one of these two quantities.

[0147] Due to the increase in light output during use in a projection exposure apparatus, a thermal load may cause temperature-induced strain. This may cause deformation of the optical element. To compensate for this effect, it may be advantageous to use the optical device, in particular, in the form of a deformable lens.

[0148] The strain gauge device can be configured to determine the temperature-induced and strain-induced changes in the shape of the optical element. These two effects can be compensated for by the actuators, which is advantageous for using materials with a finite coefficient of thermal expansion or a larger coefficient of thermal expansion than known in the art. This can save costs.

[0149] In an advantageous development of the optical device according to the invention, a plurality of measurement areas can be provided on the optical element such that the deformation of the optical surface associated with one of the optical effects caused by the optical element is measurable.

[0150] Particularly advantageously, those deformations related to the optical effect of one of the optical elements can be corrected by the optical device. For example, the optical effect may include forming an image representation.

[0151] A plurality of strain gauge devices may be provided as part of the optical device. If a plurality of strain gauge devices are present, the plurality of strain gauge devices may be provided to share other components of the optical device.

[0152] A plurality of strain gauge devices and / or a plurality of path length devices may be fitted to the optical element in a manner capable of measuring shape changes of the optical element in relation to optical imaging. The multiple actuator forces required to compensate for shape changes may be determined by calibrating and / or analyzing models and / or numerical models and / or training neural networks.

[0153] Therefore, it may be advantageous if the measurement areas are arranged near an intersection of an optical axis and an optical surface in order to precisely and reliably control the shape or deformation of the area near the optical axis.

[0154] In an advantageous development of the optical device according to the invention, a computing device may be provided to determine an actual deformation of the optical surface and / or at least a suitable force of an actuator to set a target deformation of the optical surface based on the actual strain of the at least one measurement region determined in at least one measurement region.

[0155] In particular, the closed-loop control device and the computing device may be provided to form a unit, for example, in the form of a computer.

[0156] In order to determine the force that the actuator needs to apply to achieve the target deformation defined by one of the optical surfaces and / or the desired deformation, the mechanical properties of the optical surface and / or the substrate element optionally located below the optical surface can be considered, particularly in the form of a solid-state physical model. Such a computing device may be particularly advantageous for the optional complex calculations required for this.

[0157] Furthermore, the computing device can be configured to determine a model of the mechanical relationship between the actual strain in the at least one measurement region and the actual deformation of the optical surface.

[0158] The presence of a computing device is more advantageous because, under changing environmental conditions, such as increased temperature and / or changes in operating conditions, it may be necessary to re-perform basic calculations and / or model formation. In particular, calculations for multiple class models can be performed periodically.

[0159] In an advantageous development of the optical device according to the invention, a plurality of actuators, preferably all actuators, are provided, each assigned a measurement region, the measurement region including, preferably specifically including, an effective region corresponding to the actuator.

[0160] In the context of the present invention, the effective area of ​​the at least one actuator should be understood to refer to the area of ​​the optical device in which the strain caused by the at least one actuator can be measured with sufficient accuracy by the strain gauge device.

[0161] Preferably, each actuator system may have a single, preferably path-connected, effective region, wherein such effective regions, especially the effective regions of such adjacent actuators, may overlap.

[0162] In the context of the present invention, each actuator preferably has an effective area, wherein the measurement area is preferably assigned to the effective area of ​​the actuator.

[0163] If there are multiple actuators, it is advantageous to sample each effective region of such actuators, because such actuators can be driven individually in a manner related to the effect to obtain a precise form of the deformation of the optical surface.

[0164] Alternatively or additionally, a plurality of effective regions may be provided to fall within a measurement region, thereby enabling the actuators to be driven in groups, for example in an effect-dependent manner.

[0165] To this end, it is possible to combine individual measurement areas into a larger measurement area, which are virtually interconnected. For example, since the actuators are not driven individually but in groups, faster setup of the optical surface can be achieved.

[0166] In contrast, the individual actuation of these individual actuators allows for more precise actuation of the optical surface in terms of spatial detail.

[0167] At least one path length device and / or at least one strain gauge device may be set and configured for each actuator to primarily measure an effective area of ​​the corresponding actuator, wherein the measured effective area is at least approximately independent of a strain input of one or more adjacent actuators.

[0168] In particular, the measurement area may be configured in such a way that the measurement area is at least almost entirely subjected to the strain caused by the actuator whose effective area is allocated to the measurement area.

[0169] In an advantageous development of the optical device according to the invention, the strain and / or multiple vibrations of the optical surface that provide the at least one measurement area can be determined regularly (preferably continuously) by the strain gauge device.

[0170] The regularity (preferably continuously determined) of the actual strain of the at least one measurement area helps to monitor the actual deformation of the optical surface with almost no gap over time, and thus monitor the performance of the optical element.

[0171] In particular, it is possible to record the various dynamic changes of such deformations of the optical surface. For example, such vibrations of the optical surface include these dynamic changes.

[0172] Therefore, the strain gauge device is configured to regularly (preferably continuously) determine the strain and / or vibration of the optical surface in the at least one measurement area.

[0173] The strain gauge device may be provided to measure the vibrations of the optical element and / or the optical surface at a frequency between 0 Hz (static condition) and 1000 Hz, preferably between 1 Hz and 200 Hz. Such a frequency may have a particularly negative impact on the function of the optical element and can be avoided by the optical device.

[0174] To this end, the strain gauge device can be provided configured to measure the strain at measurement frequencies of 1 kHz to 100 kHz, preferably 3 kHz to 30 kHz, and particularly preferably 5 kHz to 20 kHz. Such measurement frequencies are suitable for measuring vibrations with particular reliability at the aforementioned frequencies.

[0175] The strain gauge device may be configured to monitor the vibration behavior of the optical element or the optical device. For this purpose, it is provided to continuously and / or rapidly measure the strain.

[0176] In an advantageous development of the optical device according to the invention, one or more measurement areas may be provided on and / or in the optical element, such that one or more vibration modes of the optical surface and / or the optical element are determinable.

[0177] When the at least one vibration mode is determined, an amplitude and / or a phase of the vibration mode can be determined. In particular, the entire vibration trajectory to be measured can be provided.

[0178] In order to measure one or more vibration modes of the optical surface and / or the optical element, it is advantageous to arrange one or more measurement areas in and / or on the optical element, as these areas experience multiple particularly strong strain signals during one of the vibrations on the optical surface. Therefore, such vibration modes with particularly high signal-to-noise ratios become identifiable.

[0179] It may be advantageous to provide the actual strain of the at least one measurement area to be determined by a sampling frequency corresponding to at least one Nyquist frequency associated with the vibration frequency of the vibration mode to be determined.

[0180] Therefore, it is advantageous to accurately and reliably determine the vibration of the optical surface and / or the optical element in the vibration mode to be examined.

[0181] When the optical unit is large and the inherent stiffness requirement of the optical unit remains unchanged, the total mass of the optical unit increases disproportionately, which may lead to increased costs. Therefore, the described embodiment of the optical device is particularly advantageous if the optical element is in the form of a thin mirror. Such natural vibrations of the thin mirror can be quenched by the optical device because it includes a strain gauge device that allows on-site measurement of the deformation of the optical surface and / or the thin mirror.

[0182] Therefore, one or more strain gauge devices and / or path length devices and / or measurement areas can be attached to or in the optical element to be measured, so that a finite number of vibration modes of one of the optical elements can be measured.

[0183] The present invention also relates to a method having the features described in claim 17.

[0184] In the method according to the present invention for setting a target deformation of an optical surface of an optical element of an optical element of a lithography system by means of one or more actuators, the actual deformation of the optical surface is determined by determining at least one actual strain in at least one measurement area of ​​the optical element.

[0185] According to the method of the present invention, the success of the effect of the at least one actuator on the optical surface can be directly verified by determining a mechanical effect, namely the actual strain of the at least one measurement area of ​​the optical element.

[0186] Thus, after setting the target deformation and the at least one actuator taking effect, a particularly accurate prediction of the actual deformation of the optical surface can be obtained, since the latter is based on multiple empirical measurements.

[0187] The shape of the optical surface can be determined by measuring the actual strain at multiple discrete sampling points, wherein the overall shape of the optical surface is determined by a model and / or an interpolation.

[0188] In this case, the sampling points that provide the strain measurement are formed by a plurality of measurement areas, which are preferably configured to be separate from each other.

[0189] In an advantageous development of the method according to the invention, the at least one measurement region can be selected such that the actual deformation of the optical surface can be derived from the actual strain.

[0190] If there is an elastic function relationship between the actual strain of the measurement region and the actual strain of the optical surface, it will be easier to verify the effect of the at least one actuator. For example, a significant mechanical coupling may be provided between the at least one measurement region and the optical surface, such that the strain and / or deformation of the at least one measurement region is at least indirectly transmitted to the optical surface.

[0191] Alternatively or additionally, the at least one measurement region may be provided to correspond to at least one clearly delimitable region of the optical surface, such that the actual deformation system of the clearly confined region of the optical surface can be modeled by the actual strain of the at least one measurement region.

[0192] In addition, it is possible to provide that the at least one measurement area is disposed in or on the optical surface, so that the actual deformation of the optical surface can be removed from the strain of the at least one measurement area particularly easily.

[0193] In an advantageous development of the method according to the invention, the strain gauge device may be provided in such a configuration that at least one measured spectrum is affected in the at least one path length device by the actual strain of the at least one measured region.

[0194] If the optical path length of a measured radiation changes due to the strain in the measurement region, the strain gauge device can be in the form of an optical device. In particular, if the measured spectrum of a path length device is affected by the actual strain, the measurement principle of the strain gauge device can be traced back to an interferometric measurement, which is advantageous for the accurate assessment of such strains, and in some areas even for the accurate assessment of mismatches.

[0195] The measured spectrum of the path length device should be understood as the spectrum reflected and / or transmitted by the measured radiation system in the direction of the wave.

[0196] In an advantageous development of the method according to the invention, the actual strain can be determined by detecting at least one measurement spectrum of at least one measurement radiation.

[0197] The radiation measurement can be in broadband or narrowband form.

[0198] By using a broadband measurement radiation, multiple measurement spectra and / or a single measurement spectrum can be measured in parallel over an advantageous wide spectral range.

[0199] The measurement spectrum can be detected by a scanning method, preferably by:

[0199] - A narrow-band measurement of radiation, where the radiation along the path length of the device has only a narrow wavelength range, particularly laser radiation, and

[0199] - The relative spectral position of this narrow wavelength range varies with time, for example by a tunable laser; therefore, it is preferable to scan or sweep a wide wavelength band.

[0199] - The intensity of transmitted and / or reflected radiation is measured synchronously with the change in the wavelength range, for example, by means of a time-resolved method of a light-emitting diode, and...

[0199] - The measurement spectrum in the preferred wide wavelength band is determined by comparing the detected intensity of the measurement radiation with the wavelength of the measurement radiation at different times.

[0200] This scanning method for determining the measurement spectrum is particularly reliable and accurate.

[0201] In particular, the use of this radiation measurement method allows the use of the optical detection method and / or readout method within the scope of this method.

[0202] In an advantageous development of the method according to the present invention, the path length device formed by a grating device and / or a resonant device can be provided.

[0203] These grating devices, or these gratings and / or these optical resonators, are particularly well-suited for determining very small path length differences among the various components of the measured radiation. If the actual strain in the measurement region changes, it may cause a change in the geometry of the grating device and / or the resonator, thereby altering the optical properties of the grating device and / or the resonator, particularly its resonant and / or reflective properties. This allows for very precise determination of the altered geometry and thus the actual strain present in the measurement region.

[0204] The grating device can be integrated into the resonant device. This can help to measure the strain more accurately.

[0205] In addition, the resonant device may include at least one ring resonator, which is at least partially formed by an optical fiber.

[0206] Furthermore, the ring resonator may be provided to be at least partially formed of an optical fiber, which includes at least one fiber Bragg grating. Therefore, the bandwidth of the optical fiber and / or the full width at half maximum of the notch can be reduced by up to 10 times.

[0207] In an advantageous development of the method according to the invention, the force of the at least one actuator can be provided based on the actual deformation determined by the optical surface, the force of the at least one actuator being determined by setting a target deformation of the optical surface, and preferably being determined and / or applied in a closed loop.

[0208] A suitable force of the at least one actuator used to obtain the desired target deformation can be set with particular precision based on the determined actual deformation of the optical surface, for example, by setting it empirically. In particular, the method avoids actuation of the optical surface purely based on a positive modeling of the effect of the force of the at least one actuator.

[0209] A correction term for the actuator position can be provided, which is calculated based on a determined quantity and its deviation from multiple target values ​​of the optical device. These corrections can be calculated in a manner that makes the deformation of the optical surface closer to the target deformation.

[0210] If the vibration behavior of the optical element is mild, the actuators can be provided in a manner that reduces the amplitude of each of the vibration frequencies associated with optical imaging or the optical effect of the optical element.

[0211] In an advantageous development of the method according to the invention, the actual strain can be determined in one or more measurement regions in the optical surface configuration and / or formed thereon at least one substrate element.

[0212] If one or more substrate elements are located below the optical surface, it is advantageous to arrange the measurement areas in the one or more substrate elements, because the actual strain of the underlying substrate element under the strong mechanical coupling between the optical surface and the underlying substrate element allows for particularly accurate conclusions about the actual deformation of the optical surface that actually exists.

[0213] In this case, the optical surface can be provided as a patterned and / or coated form on and / or in the substrate element, and / or the optical surface can be patterned by the substrate element itself. If the optical surface is formed as a coating on the substrate element, since the coating is adhered to the substrate element, it is advantageous to generate a strong mechanical coupling between the substrate element and the optical surface. As a result, it can be assumed that the actual deformation of the optical surface that actually exists can be modeled by determining the current actual strain of the measurement area.

[0214] In an advantageous improvement to the method according to the invention, it is possible to simultaneously determine the actual strain in a plurality of measurement regions.

[0215] By simultaneously determining the actual strain in multiple measurement areas, a favorable and comprehensive image of the strain and deformation of the optical element can be obtained.

[0216] The actual strain can be determined rapidly in time sequence, for example, using a multiple measurement method, across a plurality of measurement regions. In particular, the plurality of measurement regions can capture the actual strain on different spatial axes, preferably linearly independent spatial axes. Therefore, it is advantageous to measure the actual strain of the optical element in three-dimensional space.

[0217] This is even more applicable if the measurement areas are grouped, for example, into groups of three, wherein the three measurement areas in a group of three are oriented along the spatial axes. In this case, such a system of groups consisting of three measurement areas can be provided and uniformly arranged in or on the optical element, particularly in or on the substrate element.

[0218] In an advantageous improvement to the method according to the invention, a shift in the detection of the at least one measurement spectrum can be provided.

[0219] Such interferometric methods can advantageously and accurately determine the individual spectral shifts of the spectrum. Therefore, it is advantageous to trace the measurement of the actual strain back to the measurement of the shift of the at least one measured spectrum.

[0220] The path length device is designed such that a frequency shift of 1 pm to 1 nm under a strain caused by a intended use of the at least one actuator is more preferably 5 pm to 500 pm, and particularly preferably 20 pm to 100 pm.

[0221] The strain gauge device and / or the path length device may be designed such that a strain resolution of 1 am to 1 nm, preferably 5 am to 1 pm, and particularly preferably 0.5 fm to 50 fm.

[0222] In particular, a shift of the reflection center wavelength of the fiber bandwidth of the grating device to be detected and / or a relative position of the center wavelength of a notch in the transmission spectrum of the measured radiation to be detected by the grating device can be provided, wherein the grating device is in particular a fiber Bragg grating.

[0223] Reducing the correlation range of the measured spectrum to the bandwidth of the reflecting fiber and / or the center wavelength of the notch in the transmission spectrum helps to quickly and accurately determine the offset. Furthermore, the relative position of the center wavelength depends directly on a grating period of the grating device, and therefore on a geometric feature of the grating device, and consequently on the actual strain of the environment surrounding the grating device, which is mechanically decoupled from the grating device, i.e., the measurement area.

[0224] It may be advantageous to measure the actual strain simultaneously in multiple measurement areas, as this allows the deformation of the optical surface of at least one actuator to be controlled and formed in a targeted and coordinated manner.

[0225] By detuning the resonant frequencies and / or center wavelengths or Bragg wavelengths of the respective path-length devices, the measurement spectra of the respective path-length devices can be formed in a distinguishable manner. In particular, this allows multiple path-length devices to be read using a single waveguide or only a few waveguides.

[0226] A path length device that can provide one or more, preferably ten or more, preferably fifty or more, and especially preferably one hundred or more simultaneous and / or nearly simultaneous readings.

[0227] In an advantageous development of the method according to the invention, the actual strain of the at least one measurement area and / or the vibration of the optical surface can be determined by the strain gauge device, preferably continuously.

[0228] Determining the regularity (preferably continuous) of the actual strain is helpful for detecting such dynamic strains, such as such vibrations and / or such tremors of the optical surface. Therefore, a corrective behavior or a corrective shape of the optical surface can be verified and / or adjusted and / or actuated at multiple fixed intervals.

[0229] A continuous determination, that is, a determination with the best possible time resolution, has the advantage that even very brief changes in the actual strain can be detected and selectively corrected.

[0230] If the reaction time of the at least one actuator is insufficient to correct such a transient deviation between the actual strain and the target strain, it may still be advantageous to monitor or detect such deviation.

[0231] In an advantageous development of the method according to the invention, one or more vibration modes of the optical surface and / or the optical element can be provided for determination.

[0232] It is advantageous to detect the excitation of one or more vibration modes of the optical surface, especially to detect multiple inherent vibrations of the optical surface, because these vibration modes can be damped, especially actively damped, for example by the at least one actuator. Therefore, the degradation of the optical effect of the optical element can be reduced or prevented.

[0233] It is particularly advantageous to monitor one or more vibration modes in the case of a very thin substrate element, because an optical surface disposed on such a substrate element may tend to vibrate with a particularly large amplitude and in an unfavorable frequency range.

[0234] In an advantageous development of the method according to the invention, the actual strain can be provided in the relative actual strain in a plurality of measurement regions at different depths of the substrate element and / or in at least one of the plurality of measurement regions in the strain neutral plane of the substrate element.

[0235] Measuring the actual strain in different layers of the substrate element helps to provide a unified representation or to obtain the actual mechanical strain present in the substrate element.

[0236] Furthermore, if the at least one measurement area is disposed in the strain neutral plane of the substrate element, the temperature-induced effect on the strain of the entire substrate element can be distinguished or separated from those strains caused by mechanical deformation within the assembly range and / or mechanical strain caused by the at least one actuator.

[0237] The shape changes and / or vibrations and / or temperatures of the optical element determined by this method can be used in many different ways.

[0238] The failure of the optical device can be determined based on the determined actual strain and / or the determined actual deformation. If a failure occurs when using the optical device in the lithography system, it is possible to selectively terminate a current process of the lithography system and / or transfer the error to subsequent processing steps. In addition, to analyze the problem, a responsible party for notifying the machine can be provided.

[0239] The present invention also relates to a lithography system having the features described in claim 29.

[0240] The lithography system according to the invention (particularly a projection exposure apparatus for semiconductor lithography) comprises an illumination system having a radiation source and an optical unit containing at least one optical element. According to the invention, at least one optical device according to the invention is provided, wherein the at least one optical element is an optical element of the at least one optical device. Alternatively or additionally, at least one of these optical elements may include an optical surface, which can be deformed using the method according to the invention.

[0241] Within the scope of the present invention, a deformability by means of the method according to the present invention should be understood as referring to the adjustability of the deformation of the optical surface.

[0242] The advantage provided by the lithography system according to the present invention is that the optical effect of the optical element or the optical surface can be precisely controlled and precisely adjusted, so that a favorable high imaging quality can be obtained when using the projection exposure device.

[0243] In particular, the optical device is a projection lens suitable for an EUV projection exposure device.

[0244] This optical device is particularly suitable for an EUV projection exposure device and / or a DUV projection exposure device and / or a UV projection exposure device.

[0245] In particular, at least one of the optical components or mirrors of the projection exposure apparatus may be part of the optical apparatus.

[0246] The present invention also relates to a method for manufacturing an optical element for the lithography system having the features described in claim 30.

[0247] The method for manufacturing an optical element for a lithography system containing an optical surface, wherein the optical surface can be deformed by one or more actuators, wherein the optical element includes a strain gauge device for determining the deformation of the optical surface, wherein the strain gauge device includes at least one path length device for generating a measurement spectrum of the measurement radiation, wherein the path length device includes a grating device for the measurement radiation and / or a resonant device for the measurement radiation, and / or at least one waveguide, including forming the at least one waveguide and / or the at least one grating device and / or at least one resonant device constituted by the substrate element.

[0248] In a first embodiment of the present invention, if the strain gauge device includes at least one path length device for generating a measurement spectrum of measurement radiation, wherein the path length device includes a grating device for the measurement radiation and / or a resonant device for the measurement radiation, then the at least one grating device and / or the at least one resonant device may be formed from the substrate element.

[0249] In a second embodiment of the present invention, if the strain gauge device includes at least one waveguide, wherein the at least one waveguide may be formed by the substrate element.

[0250] In an advantageous development of the manufacturing method according to the present invention, the at least one waveguide and / or the at least one grating device and / or the at least one resonant device formed from the substrate element can be realized by direct writing through the local change of the refractive index.

[0251] In an advantageous development of the manufacturing method according to the invention, the local variation in refractive index can be formed by a writing radiation, for example in an ultraviolet spectral range and / or by using multiple ultrashort laser pulses (preferably having pulse durations of several femtoseconds, particularly 1 to 15 femtoseconds), and / or ion beams, and / or electron beams.

[0252] In an advantageous development of the manufacturing method according to the invention, the at least one waveguide and / or the at least one path length device can be coated near a surface using lithography techniques such as exposure, development, etching or applying material.

[0253] In an advantageous development of the manufacturing method according to the invention, the at least one waveguide and / or the at least one path length device is configured in three dimensions, particularly for monolithic manufacturing and / or far below a surface of the optical element, particularly below the optical surface.

[0254] It may be advantageous if at least one of the optical elements of the lithography system according to the invention is manufactured by the manufacturing method according to the invention or one of the plurality of developments thereof.

[0255] It may be advantageous if the optical element used in the method for setting the target deformation of the optical surface of an optical element according to the invention is manufactured by the manufacturing method according to the invention or one of the plurality of developments thereof.

[0256] The features described in connection with any of the various aspects of the present invention (particularly the features provided by the optical device according to the present invention, the method according to the present invention, the lithography system according to the present invention, or the manufacturing method according to the present invention) are also advantageous for use in other aspects of the present invention. Similarly, the advantages specified in connection with any aspect of the present invention are also to be understood in relation to other aspects of the present invention.

[0257] Furthermore, references to terms such as “containing,” “having,” or “with” do not exclude the fact that other features or steps are present. In addition, terms such as “a” or “the” that indicate multiple individual steps or features do not exclude a plurality of features or steps, and vice versa.

[0258] However, in a purely embodiment of the invention, the features introduced in this invention may also be provided in an exhaustive manner using the terms "contains," "has," or "has." Thus, one or more feature listings may be considered entirely within the scope of the invention, for example, when considered individually for each claim. For instance, the invention may comprise only the plurality of features as described in claim 1.

[0259] Designations such as "first" or "second" are primarily used to distinguish between features of relative apparatus or methods, and do not necessarily imply that the features need to be related to each other.

[0260] Several exemplary embodiments of the present invention will now be described in more detail with reference to the accompanying drawings.

[0261] The figures in each case show, in combination, a plurality of preferred embodiments of the various features of the present invention. The features of these exemplary embodiments can also be implemented with respect to other features of the same exemplary embodiments, and can be easily and therefore readily combined by those skilled in the art to form further expedient combinations and adjunct combinations with features of other exemplary embodiments.

[0262] In multiple diagrams, components with the same function have the same component number. [Simplified Explanation of the Diagram]

[0263] In the diagram:

[0264] Figure 1 shows a longitudinal section of an EUV projection exposure device;

[0265] Figure 2 shows a DUV projection exposure device;

[0266] FIG3 shows a cross-sectional schematic diagram through a possible embodiment of the optical device according to the present invention;

[0267] FIG3a shows a block diagram of an embodiment of the method according to the present invention;

[0268] FIG3b shows a schematic diagram of a possible embodiment of the optical element of the optical device according to the present invention;

[0269] FIG4 shows a schematic diagram of another possible embodiment of an optical element of the optical device according to the present invention;

[0270] FIG5 shows a schematic diagram of another possible embodiment of an optical element of the optical device according to the present invention;

[0271] FIG6 shows an isometric view of a possible embodiment of the optical device according to the present invention;

[0272] FIG7 shows an isometric view of another possible embodiment of the optical device according to the present invention;

[0273] FIG8 is a schematic diagram showing an enlarged isometric view of a possible embodiment of the path length device of the optical device according to the present invention;

[0274] Figure 9 shows a schematic diagram of a possible embodiment of a grating device;

[0275] Figure 10 shows a waveform of a possible measured spectrum of a grating device;

[0276] Figure 11 shows a schematic diagram of another possible embodiment of a grating device;

[0277] Figure 12 shows a schematic diagram of another possible embodiment of a grating device;

[0278] Figure 13 shows a schematic diagram of one possible embodiment of a resonant device;

[0279] Figure 14 shows another schematic diagram of one embodiment of a grating device;

[0280] Figure 15 shows a schematic diagram of another possible embodiment of a grating device;

[0281] Figure 16 shows a schematic diagram of another possible embodiment of the resonant device;

[0282] Figure 17 shows an isometric view of a possible embodiment of the optical device according to the present invention;

[0283] Figure 18 shows a possible integration schematic diagram of the strain gauge device in an optical element of the optical device according to the present invention; and

[0284] Figure 19 shows a schematic diagram of one possible manufacturing method of the strain gauge device.

Implementation Method

[0285] Referring to Figure 1, the basic elements of a lithography EUV projection exposure apparatus 100, as an example of a lithography system, are described below by way of example. The description of the basic structure and components of the EUV projection exposure apparatus 100 is not intended to be limiting.

[0286] An illumination system 101 of the EUV projection exposure apparatus 100 includes a radiation source 102 and an illumination optics unit 103 for illuminating an object field 104 in an object plane 105. Hereinafter, a photomask 106 disposed in the object field 104 is disclosed. The photomask 106 is supported by a photomask stage 107. The photomask stage 107 is movable by a photomask displacement driver 108, particularly along a scanning direction.

[0287] In Figure 1, a Cartesian xyz coordinate system is plotted to aid in interpretation. The x-direction system travels perpendicular to the plane of the diagram. The y-direction system extends horizontally, and the z-direction system extends vertically. In Figure 1, the scanning direction system extends along the y-direction. The z-direction system extends perpendicular to the object plane 105.

[0288] The EUV projection exposure apparatus 100 includes a projection optics unit 109. The projection optics unit 109 is used to image the object field 104 onto an image field 110 in an image plane 111. The image plane 111 travels parallel to the object plane 105. Alternatively, the angle between the object plane 105 and the image plane 111 may be different from 0°.

[0289] A structure on photomask 106 is imaged onto a photosensitive layer of wafer 112, and the wafer is disposed in the region of image field 110 in image plane 111. Wafer 112 is supported by wafer stage 113. Wafer stage 113 can be moved by a wafer displacement driver 114, particularly along the y-direction. The displacement of photomask 106 by photomask displacement driver 108 and the displacement of wafer 112 by wafer displacement driver 114 can occur synchronously with each other.

[0290] Radiation source 102 is an EUV radiation source. Radiation source 102 emits EUV radiation 115, which, in particular, is also referred to below as the radiation used or illumination radiation. In particular, the radiation used 115 has a wavelength in the range of 5 nm to 30 nm. Radiation source 102 may be a plasma source, such as an LPP source ("laser-generated plasma") or a GDPP source ("gas discharge-generated plasma"). It may also be a synchrotron-based radiation source. Radiation source 102 may be a free electron laser (FEL).

[0291] Illumination radiation 115 emitted from radiation source 102 is focused by a collector 116. The collector 116 may be a collector having one or more elliptical and / or hyperboloidal reflective surfaces. At least one reflective surface of the collector 116 may be irradiated by the illumination radiation 115 with tangential incidence (GI) at an angle of incidence greater than 45° or perpendicular incidence (NI) less than 45°. The collector 116 may be structured and / or coated, firstly to optimize its reflectivity to the radiation 115 used, and secondly to suppress incoming light.

[0292] Downstream of collector 116, illumination radiation 115 propagates through an intermediate focal point in an intermediate focal plane 117. Intermediate focal plane 117 may represent the separation between the radiation source module having radiation source 102 and collector 116 and illumination optical unit 103.

[0293] The illumination optical unit 103 includes a deflector 118 and a first facet 119 disposed downstream therein in the beam path. The deflector 118 may be a plane deflector, or alternatively, a mirror having a beam influence effect beyond a pure deflection effect. Alternatively or additionally, the deflector 118 may be in the form of a spectral filter that separates one of the wavelengths of light used in the illumination radiation 115 from an incoming light of a wavelength deviation. If the first facet 119 is disposed in a plane of the illumination optical unit 103 that is optically conjugate with the object plane 105 as a field plane, it is also referred to as a field facet. The first facet 119 includes a plurality of individual first facets 120, which are also referred to below as field facets. Only a few of these facets 120 are shown by way of illustration in FIG1.

[0294] The first facet 120 may be in the form of multiple macroscopic facets, particularly a rectangular facet or a facet having an outer contour with an arcuate outer contour or a portion of a circle. The first facet 120 may be in the form of multiple planar facets, or as a convex or concave curved facet.

[0295] For example, as known from patent DE 10 2008 009 600 A1, the first facet 120 itself can in each case be composed of a plurality of individual mirrors, particularly a plurality of micromirrors. The first facet 119 can in particular be formed as a microelectromechanical system (MEMS system). For more detailed information, please refer to patent DE 10 2008 009 600 A1.

[0296] Between the collector 116 and the deflector 118, the illumination radiation 115 extends horizontally, that is, along the y direction.

[0297] In the beam path of the illumination optical unit 103, a second facet mirror 121 is disposed downstream of the first facet mirror 119. If the second facet mirror 121 is disposed in a pupil plane of the illumination optical unit 103, it is also referred to as a pupil facet mirror. The second facet mirror 121 may also be disposed at a distance from the pupil plane of the illumination optical unit 103. In this case, the combination of the first facet mirror 119 and the second facet mirror 121 is also referred to as a specular reflector. Specular reflectors are known from patents US 2006 / 0132747 A1, EP 1 614 008 B1, and US 6,573,978.

[0298] The second facet 121 comprises a plurality of second facets 122. In the case of a pupil facet 121, the second facet 122 is also called a pupil facet.

[0299] The second facet 122 may also be a macroscopic facet, which may, for example, have a circular, rectangular or hexagonal perimeter, or may be a facet composed of multiple micromirrors. In this regard, see also patent DE 10 2008 009 600 A1.

[0300] The second facet 122 may have a planar or alternatively convex or concave reflective surface.

[0301] The illumination optical unit 103 thus forms a bifaceted system. This basic principle is also known as a fly-eye integrator.

[0302] It may be advantageous to not precisely position the second facet mirror 121 in a plane that is optically conjugate to the pupil plane of the projection optical unit 109.

[0303] With the help of the second facet mirror 121, each of the first facets 120 is imaged into the object field 104. The second facet mirror 121 is the last beam-shaping mirror, or in fact the last mirror of the illumination radiation 115 in the beam path upstream of the object field 104.

[0304] In another embodiment of the illumination optics unit 103 (not shown), a transfer optics unit that particularly facilitates imaging the first facet 120 into the object field 104 may be configured in the beam path between the second facet 121 and the object field 104. This transfer optics unit may have exactly one mirror, or alternatively two or more mirrors, which are arranged sequentially in the beam path of the illumination optics unit 103. In particular, the transfer optics unit may include one or two mirrors for perpendicular incidence (NI mirror, "perpendicular incidence" mirror) and / or one or two mirrors for tangential incidence (GI mirror, "tangential incidence" mirror).

[0305] In the embodiment shown in FIG1, the illumination optical unit 103 includes exactly three mirrors downstream of the collector 116, specifically a deflector 118, a field splitter 119, and a pupil splitter 121.

[0306] In another embodiment of the illumination optical unit 103, the deflector 118 may also be omitted, so the illumination optical unit 103 may have two mirrors downstream of the collector 116, in particular the first facet mirror 119 and the second facet mirror 121.

[0307] Imaging the first plane 120 onto the object plane 105 by means of the second plane 122 or by using the second plane 122 and the transfer optical unit is usually only an approximate imaging.

[0308] The projection optics unit 109 includes a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the EUV projection exposure apparatus 100.

[0309] In the example shown in Figure 1, the projection optics unit 109 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or any other number of mirrors M1 are also possible. Each of the penultimate mirror M5 and the last mirror M6 has a through-hole for illumination radiation 115. The projection optics unit 109 is a double-shielding optics unit. The projection optics unit 109 has an imaging-side numerical aperture greater than 0.5, and may also be greater than 0.6, for example, 0.7 or 0.75.

[0310] Each reflecting surface of these mirrors Mi can be implemented as a freeform surface without an axis of rotational symmetry. Alternatively, each reflecting surface of these mirrors Mi can be designed as an aspherical surface having exactly one axis of rotational symmetry of its shape. Like the mirrors of the illumination optics unit 103, these mirrors Mi can have a high-reflectivity coating for illumination radiation 115. These coatings can be designed as multilayer coatings, particularly having alternating molybdenum and silicon layers.

[0311] The projection optical unit 109 has a large object-image offset in the y direction between the y coordinate of the center of the object field 104 and the y coordinate of the center of the imaging field 110. In the y direction, this object-image offset can be approximately the same as the z distance between the object plane 105 and the imaging plane 111.

[0312] Specifically, the projection optical unit 109 may have a modified form. Specifically, it has different imaging ratios βx and βy in the x and y directions. Preferably, the two imaging ratios βx and βy of the projection optical unit 109 are (βx, βy) = (+ / -0.25, + / -0.125). A positive imaging ratio β refers to imaging without image inversion. A negative imaging ratio β refers to imaging with image inversion.

[0313] Therefore, the projection optical unit 109 is reduced in size in the x direction, that is, in the direction perpendicular to the scanning direction, by a ratio of 4:1.

[0314] The projection optical unit 109 causes the ratio in the y direction, i.e. in the scanning direction, to be reduced to 8:1.

[0315] Other imaging scales are also possible. Imaging scales with the same sign and the same absolute value in the x and y directions are also possible, for example, with an absolute value of 0.125 or 0.25.

[0316] The number of intermediate imaging planes in the x and y directions of the beam path between the object field 104 and the imaging field 110 may be the same, or may be different depending on the embodiment of the projection optical unit 109. Examples of projection optical units with different numbers of such intermediate images in the x and y directions are known from patent US 2018 / 0074303 A1.

[0317] In each case, at least one of the pupil planes 122 is assigned to at least one of the field planes 120 to form an illumination channel for illuminating the object field 104 in each case. In particular, this can produce illumination according to the Kohler principle. With the help of the field planes 120, the far field is decomposed into a plurality of object fields 104. The field planes 120 generate a plurality of intermediate focal images on the pupil planes 122 respectively assigned to them.

[0318] The field planes 120, which are respectively assigned to the pupil planes 122, are imaged onto the photomask 106 in a superimposed manner to illuminate the object field 104. The illumination of the object field 104 is particularly uniform. Preferably, it has a uniformity error of less than 2%. Field uniformity can be achieved by covering different illumination channels.

[0319] The illumination of the entrance pupil of the projection optical unit 109 can be geometrically defined by the arrangement of the pupil surfaces. The intensity distribution in the entrance pupil of the projection optical unit 109 can be set by selecting the illumination channels, in particular a subset of the pupil surfaces that guide the light. This intensity distribution is also called illumination setting.

[0320] The same better pupil uniformity in the region of multiple segments illuminated in a defined manner by the illumination pupil of one of the illumination optical units 103 can be achieved by redistributing the illumination channels.

[0321] The following describes other states and details of the illumination of the object field 104, especially the entrance pupil of the projection optical unit 109.

[0322] In particular, the projection optical unit 109 may have a concentric entrance pupil. The latter is accessible. It may also be inaccessible.

[0323] The incident pupil of the projection optics unit 109 cannot typically be accurately illuminated using the pupil plane mirror 121. When the projection optics unit 109 on the wafer 112 is imaged telecentrically from the center of the pupil plane mirror 121, the aperture rays typically do not intersect at a single point. However, it is possible to find a region where the distance between the paired aperture rays becomes minimal. This region represents a region in the real space of the incident pupil or its conjugate. In particular, this region has a finite curvature.

[0324] The projection optical unit 109 may have different entrance pupil positions for the tangential beam path and for the sagittal beam path. In this case, in particular, an imaging element of the optical element of the transfer optical unit should be disposed between the second facet mirror 121 and the mask 106. With the aid of this optical element, the different relative positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

[0325] In the element configuration of the illumination optical unit 103 shown in FIG1, the pupil facet 121 is disposed in a region conjugate with the incident pupil of the projection optical unit 109. The first facet 119 is disposed inclined relative to the object plane 105. The first facet 119 is disposed inclined relative to a configuration plane defined by the deflector 118.

[0326] The first facet mirror 119 is configured at an angle relative to a configuration plane defined by the second facet mirror 121.

[0327] Figure 2 shows an illustrative DUV projection exposure apparatus 200. The DUV projection exposure apparatus 200 includes an illumination system 201; a device known as a photomask platform 202 for receiving and precisely positioning a photomask 203 to determine subsequent structures on a wafer 204; a wafer support stage 205 for supporting, moving, and precisely positioning the wafer 204; and, in particular, an imaging device of a projection optics unit 206 having a plurality of optical elements, in particular lens elements 207, which are supported in a lens housing 209 of the projection optics unit 206 by a plurality of mounting members 208.

[0328] Various refractive, diffractive and / or reflective optical elements may be provided as alternatives to or in addition to the lens elements 207 shown, especially mirrors, prisms, end plates and the like.

[0329] The basic functional principle of the DUV projection exposure apparatus 200 is to provide conditions for imaging multiple structures introduced into the photomask 203 onto the wafer 204.

[0330] The illumination system 201 provides a projection beam 210 in the form of electromagnetic radiation, which is required for imaging the photomask 203 on the wafer 204. A laser, plasma source, or the like may be used as such a radiation source. The radiation is shaped in the illumination system 201 by means of such optical elements, such that the projection beam 210 has desired characteristics regarding diameter, polarization, wavefront shape, and the like when it is incident on the photomask 203.

[0331] An image of the photomask 203 is generated by the projection beam 210 and transferred from the projection optics unit 206 to the wafer 204 in a appropriately reduced form. In this case, the photomask 203 and the wafer 204 can move synchronously, such that some areas of the photomask 203 are almost continuously imaged onto the corresponding areas of the wafer 204 during a so-called scanning period.

[0332] An air gap between the last lens element 207 and the wafer 204 can optionally be replaced by a liquid medium having a refractive index greater than 1.0. For example, the liquid medium can be high-purity water. This structure is also known as immersion lithography and has an increased lithography resolution.

[0333] The use of this invention is not limited to use in projection exposure apparatuses 100 and 200, and is in particular not limited to the structures described. This invention is applicable to any lithography system, but is particularly applicable to projection exposure apparatuses having the described structures. This invention is also applicable to EUV projection exposure apparatuses having smaller imaging-side numerical apertures than those described in the context of FIG. 1 and unshielded mirrors M5 and / or M6. In particular, this invention is also applicable to EUV projection exposure apparatuses having imaging-side numerical apertures of 0.25 to 0.5, preferably 0.3 to 0.4, and particularly preferably 0.33. This invention and the following illustrative embodiments should not be construed as limiting a particular design. The following figures are shown by way of example and in a highly illustrative manner only.

[0334] FIG3 shows a schematic cross-sectional view of one possible embodiment of the optical device 1 according to the present invention.

[0335] The optical device 1 for a lithography system, particularly for projection exposure devices 100 and 200, preferably as shown in Figures 1 and 2, comprises at least one optical element 2 having an optical surface 3, and one or more actuators 4 for deforming the optical surface 3. The optical element 2 further comprises a strain gauge device 5 for determining the deformation of the optical surface 3.

[0336] In the exemplary embodiment shown in FIG3, the strain gauge device 5 is configured to determine the strain of at least one measurement region 6 of the optical element 2. In this case, the at least one measurement region 6 is configured such that a strain of the measurement region 6 is determined by the deformation of the optical surface 3.

[0337] In particular, the optical surface 3 and the measurement area 6 are mechanically coupled in the illustrated embodiment.

[0338] Furthermore, Figure 3 shows an embodiment of the optical device 1, wherein the strain gauge device 5 includes at least one path length device 7 for generating a measurement spectrum 8 (see Figure 9) of the measurement radiation 9.

[0339] Furthermore, in the exemplary embodiment of the optical device 1 shown in FIG3, the optical element 2 includes a substrate element 10, and the optical surface 3 is disposed or formed on the substrate element 10. In addition, the strain gauge device 5 is partially disposed within the substrate element 10.

[0340] In an alternative embodiment not described herein, the strain gauge device 5 may be provided entirely disposed in and / or on the substrate element 10.

[0341] Furthermore, FIG3 shows an embodiment of the optical device 1, wherein the strain gauge device 5 includes both a waveguide 11 and the path length devices 7. In the described exemplary embodiment, the path length device 7 is in the form of a grating device 7a. In the exemplary embodiment, a plurality of path length devices 7 are provided, each of which is preferably implemented as a grating device 7a.

[0342] In particular, in the exemplary embodiment shown in FIG3, the strain gauge device 5 includes at least one waveguide 11 and a plurality of path length devices 7, wherein the at least one waveguide 11 sequentially guides the measurement radiation 9 to the plurality of path length devices 7.

[0343] Figure 3 also shows an embodiment of the optical device 1, wherein the at least one grating device 7a is preferably in the form of a fiber Bragg grating 7b.

[0344] Furthermore, in the exemplary embodiment, at least one waveguide 11 is preferably in the form of an optical fiber 11a.

[0345] Furthermore, in the exemplary embodiment shown in FIG3, a preferred closed-loop control device 12 is provided to set a target strain in the measurement region 6 by means of at least an actuator 4. In this adjustment, the actual strain of the measurement region 6 determined by the strain gauge device 5 is taken into account.

[0346] In this exemplary embodiment, the closed-loop control device 12 is also configured to set a target deformation of the optical surface 3 by means of the actuator 4, while taking into account the actual strain of the measurement area 6 determined by the strain gauge device 5.

[0347] Furthermore, in the exemplary embodiment described, the closed-loop control device 12 is configured to correct the deviation between the actual deformation of the optical surface 3 and the target deformation caused by at least one temperature and / or strain.

[0348] Furthermore, FIG3 shows an embodiment of the optical device 1, wherein a plurality of measurement regions 6 are arranged on the optical element 2 such that the deformation of the optical surface 3 related to an optical effect caused by the optical element 2 is measurable.

[0349] Furthermore, in the exemplary embodiment of the optical device 1 described in FIG3, a computing device 13 is provided to determine the actual deformation of the optical surface 3 and at least the appropriate force of the actuator 4, for setting a target deformation of the optical surface 3 based on the actual strain determined by at least one measurement area 6.

[0350] Furthermore, in the exemplary embodiments described, each actuator 4 is assigned a corresponding measurement area 6, which actually only includes an effective area 14 corresponding to the actuator 4.

[0351] Furthermore, in the exemplary embodiment shown in FIG3, the optical device 1 is configured such that the strain of at least one measurement area 6 and / or the vibration of the optical surface 3 can be regularly determined, in particular by means of the high frequency generated by the strain gauge 5 and thus approximately continuous.

[0352] Furthermore, in the exemplary embodiment described in FIG3, a plurality of measurement regions 6 are arranged on and in the optical element 2 such that one or more vibration modes of the optical surface 3 and the optical element 2 are determinable.

[0353] The optical device 1 shown in Figure 3 is particularly suitable for performing a method for setting a target deformation of an optical surface 3.

[0354] In addition, the path length device 7 includes a grating device 7a for measuring radiation 9.

[0355] The exemplary embodiment of the optical device 1 described in FIG8 is particularly suitable for an embodiment type of performing the method, wherein the path length device 7 of the embodiment type is formed by a resonant device 7c.

[0356] Figure 3a shows a block diagram representation of the method.

[0357] In the method for setting the target deformation of the optical surface 3 of the optical element 2 of the lithography system, particularly the projection exposure apparatus 100, 200, by means of one or more actuators, at least one actual strain of at least one measurement area 6 of the optical element 2 is determined in a strain determination block 15, and thus the actual deformation of the optical surface 3 is determined in a deformation determination block 16.

[0358] Furthermore, in the exemplary embodiment of the method shown in FIG3a, at least one measurement region 6 is selected in a selection block 17 such that the actual deformation of the optical surface 3 can be derived from the actual strain in the deformation determination block 16. The effect of the selection block 17 on the derivation is illustrated by a dashed line, which is an arrow pointing between the strain determination block 15 and the deformation determination block 16.

[0359] In an exemplary embodiment of the method shown in FIG3a, the strain gauge device 5 provides the actual strain of at least one measurement area 6 to be regularly determined and the vibration of the optical surface 3, particularly at high frequency and preferably at least approximately continuously determined, by means of strain determination block 15 and / or deformation determination block 16.

[0360] In addition, one or more vibration modes of the optical surface 3 and / or optical element 2 to be determined in strain determination block 15 and / or deformation determination block 16 are provided.

[0361] Furthermore, in the described exemplary embodiment, the actual strain to be determined synchronously in a plurality of measurement regions 6 in the strain determination block 15 is provided.

[0362] In particular, the actual strain is determined in one or more measurement regions 6 of at least one substrate element 10 below the optical surface 3.

[0363] Furthermore, in an exemplary embodiment of the method shown in FIG3a, a force determining block 18 is provided to determine at least the force of actuator 4 required in deformation determining block 16 to set the target deformation of optical surface 3 based on the determined actual deformation of optical surface 3 in an adjustment block 19.

[0364] In particular, in the described exemplary embodiment, the field strength of the electric field to be applied to at least actuator 4 is provided in the force determination block 18.

[0365] According to the described exemplary embodiment, the force determined in the force determination block 18 is applied by at least one actuator 4.

[0366] Furthermore, in the exemplary embodiment shown in FIG3a, a closed loop is provided from the adjustment block 19 to the strain determination block 15. In the exemplary embodiment shown in FIG3a, the closed loop is illustrated by a solid arrow. The control loop is closed because it is actually closed by the effect obtained by the adjustment block 19 as measured by the strain determination block 15.

[0367] Starting from strain determination block 15, the new settings in adjustment block 19 can be realized sequentially through force determination block 18 and deformation determination block 16. Therefore, the closed loop can be operated as many times as desired, preferably in a conventional manner, to obtain a target deformation of the optical surface 3.

[0368] The exemplary embodiment of the optical device 1 depicted in FIG3 is particularly suitable for implementing the method, according to which the strain gauge device 5 is configured such that at least one measured spectrum 8 is affected by the actual strain of at least one measured region 6 in at least one path length device 7.

[0369] For the purpose of measuring at least one spectrometer 8, a spectrometer 20 is provided in the exemplary embodiment shown in FIG3.

[0370] For example, the spectroscopic instrument 20 can be used to determine the actual strain by detecting at least one measured spectrum 8 of at least one measured radiation 9, which is preferably broadband in the exemplary embodiment.

[0371] Alternatively or additionally, a narrow-band measurement radiation 9 may be coupled into a waveguide 11 and at least one measurement spectrum 8 may be determined by a scanning method by sweeping or scanning a sufficiently wide wavelength band.

[0372] In this process, the measurement radiation 9 is formed by a broadband measurement radiation source (not shown here).

[0373] Figure 3b shows an isometric rear view of the optical element 2, wherein the strain gauge device 5 includes an optical fiber 11a and a plurality of path length devices 7, the optical fiber 11a continuously guiding the measurement radiation 9 to the plurality of path length devices 7.

[0374] In the exemplary embodiment shown in FIG3b, optical fiber 11a is guided into a loop in substrate element 10.

[0375] In the described exemplary embodiment, each measurement region 6 of the path length devices 7 is disposed in the substrate element 10.

[0376] In another exemplary embodiment not described herein, the optical fiber 11a may be replaced by a different waveguide 11, for example by an optical channel.

[0377] Figure 4 shows an isometric rear view of another possible embodiment of the optical element 2 of the optical device 1.

[0378] In the described exemplary embodiment, each measurement region 6 of the path length device 7 is disposed in a strain neutral plane 21 of the substrate element 10.

[0379] Figure 5 shows a cross-sectional schematic diagram of the optical element 2, wherein the waveguide 11 or the optical fiber 11a is integrated into the substrate element 10. In this case, the optical fiber 11a or the waveguide 11 is inserted into a groove 22, and preferably embedded in a welding glass 23, and is therefore practically monolithically connected to the substrate element 10.

[0380] In particular, this article provides that the optical fiber 11a is removed from a plastic coating or the plastic coating is removed before it is embedded in the welding glass 23.

[0381] Figure 6 shows an isometric rear view of the optical device 1. For better visibility, the actuators 4 and optical elements 2 are shown in an exploded view, indicated by dashed lines.

[0382] Again, the waveguide 11 or optical fiber 11a is guided through the substrate element 10 in a serpentine, loop, or tortuous manner. In this case, the waveguide 11 or optical fiber 11a is sequentially guided to the path length devices 7, which are formed as a plurality of grating devices 7a, particularly as a plurality of fiber Bragg gratings 7b in the illustrated embodiment. The waveguide 11 can be connected to the spectroscopic instrument 20 (not shown in FIG. 6) via a connecting device 24.

[0383] Figure 7 shows an isometric rear view schematic diagram of another possible embodiment of the optical device 1. For better visibility, the actuators 4 and the optical elements 2 are shown in an exploded view, indicated by dashed lines. In this practical embodiment, the actuators 4 are mechanically coupled to the optical elements 2, particularly the substrate element 10.

[0384] In the exemplary embodiment shown in FIG7, a plurality of waveguides 11 or optical fibers 11a are provided.

[0385] In the exemplary embodiment shown in FIG7, a plurality of measurement regions 6 of the strain gauge device 5 are formed at different depths in the substrate element 10, and at least one of the plurality of measurement regions 6 is disposed in the strain neutral plane 21 of the substrate element 10.

[0386] The embodiment of the optical device 1 depicted in FIG7 is particularly suitable for performing an embodiment of a method according to which the relative actual strain in a plurality of measurement regions 6 is determined at different depths of the substrate element 10, and the actual strain in at least one of the plurality of measurement regions 6 is determined in the strain neutral plane 21 of the substrate element 10.

[0387] Figure 8 shows another schematic diagram of the optical device 1, in which a portion of the path length device 7 is depicted in an enlarged manner. For a representation of the optical device 1, refer particularly to the embodiment shown in Figure 6.

[0388] In the exemplary embodiment shown in FIG8, the path length device 7 includes a resonant device 7c for measuring radiation 9 and a plurality of waveguides 11.

[0389] In the illustrated embodiment, the resonant device 7c is formed in a filling layer 25, which in the illustrated embodiment is a silicon oxide filling layer for a planar surface. Furthermore, the resonant device 7c includes a ring resonator 26.

[0390] Figure 9 shows a schematic diagram of the fiber Bragg grating 7b in fiber 11a.

[0391] In this case, the optical fiber 11a is formed by a cladding layer 27, a core 28, and a plurality of line grating regions 29 disposed in the core 28. In this document, the line grating regions 29 have a different refractive index than the core 28.

[0392] On the left side, the measurement radiation 9 is coupled into the optical fiber 11a and guided by the optical fiber 11a to the fiber Bragg grating 7b. A portion of the measurement radiation 9 is reflected back at the fiber Bragg grating, while another portion of the measurement radiation 9 is transmitted via the fiber Bragg grating 7b.

[0393] The direction of propagation of the measured radiation 9 is indicated by the arrow.

[0394] Assign the displayed measurement spectrum 8 to the corresponding arrow.

[0395] In the measurement spectrum 8 and the similarly depicted input coupling spectrum 30, the measurement radiation 9 is coupled into the optical fiber 11a via it, and a wavelength is plotted on the horizontal wavelength axis 31. The intensity of the measurement radiation 9 in the corresponding spectral region is plotted on a vertical intensity axis 32.

[0396] It is evident here that when the measurement radiation 9 with a broadband input coupling spectrum 30 is coupled in, the reflected measurement spectrum 8 has only a narrow peak, while the transmitted measurement spectrum 8 has a narrow notch. The notch in the transmitted measurement spectrum 8 originates from a portion of the reflection of the measurement radiation 9. Therefore, the two measurement spectra 8 complement each other to form the input coupling spectrum 30.

[0397] The line grating gap 29a can be formed in such a manner that a phase shift of pi exists between the various portions of the measured radiation 9. For example, a Fabry-Perot chamber can be formed in this manner. The line grating gap 29a can be formed in such a manner that a sharp notch with a full width of 1 GHz to 3 GHz, preferably 2 GHz, appears at half its height in a frequency space.

[0398] Figure 10 shows a schematic diagram of a possible measurement spectrum 8. These wavelengths are plotted along the wavelength axis 31, while the reflectivity of the path length device is plotted on a reflectivity axis 33 (see, in this respect, the reflected component of the measurement radiation 9 in Figure 9).

[0399] Figure 11 shows a schematic diagram of an exemplary embodiment similar to the fiber Bragg grating 11b in Figure 9.

[0400] In this case, the line grating regions 29 have different refractive indices, which is illustrated by shading at different degrees of proximity. In this case, the refractive index of the line grating region 29 is different from that of the core 28. The reflected measurement spectrum appears below the fiber Bragg grating 7b, and its axis markings are similar to those in Figure 9.

[0401] Due to the refractive index variation between the linear grating regions 29 depicted in FIG11, for example, it can suppress the second maximum value in the measured spectrum 8.

[0402] Figure 12 shows a schematic diagram of another possible embodiment of the fiber Bragg grating 7b.

[0403] In this case, the line grating regions 29 are arranged in groups within the core 28, and these groups are spaced apart from each other. The spacing is chosen such that the components of the measurement radiation 9 reflected by each group have a phase shift pi. Therefore, these components of the measurement radiation 9 exhibit destructive interference, and in the representation of the measurement spectrum 8 shown below the line grating regions 29, a notch can be seen in the region of the reflection spectrum where the highest reflectivity is expected.

[0404] This is advantageous because the observable notch system is sharper than the plateau phase of the reflectance measurement spectrum 8 (refer to Fig. 11), and therefore can be detected more accurately.

[0405] This embodiment of the fiber Bragg grating 7b can also be called a one-pi fiber Bragg grating.

[0406] Figure 13 shows a schematic diagram of another embodiment of the path length device 7.

[0407] In this case, the measurement radiation 9 is fed into the waveguide 11 and coupled to a resonant device 7c in a coupling device 34, the resonant device 7c being formed as a ring resonator 26. In the described exemplary embodiment, the ring resonator 26 itself includes the waveguide 11, wherein the measurement radiation 9 is fed to a grating device 7a. The measurement radiation 9 reflected and / or transmitted by the grating device 7a is recoupled into the waveguide 11 by another coupling device 34, and the transmitted measurement spectrum 8 or the reflected measurement spectrum 8 on different sides of the waveguide 11 can be examined.

[0408] In particular, the grating device 7a can be formed as a fiber Bragg grating 7b and especially as a pi fiber Bragg grating.

[0409] Figure 14 shows another schematic diagram of the reflectance measurement spectrum 8 of the grating device 7a in a manner similar to that shown in Figure 11.

[0410] FIG15 shows a further schematic representation of the reflectance measurement spectrum 8 of a fiber Bragg grating 7b as an embodiment of a pi fiber Bragg grating, in a manner similar to that shown in FIG12.

[0411] Figure 16 shows a schematic diagram of an embodiment of the resonant device 7c. The resonant device 7c further includes a ring resonator 26. The diameter of the ring resonator 26 is indicated by a double-headed arrow. A waveguide 11 (through which light can be coupled to and / or coupled from the output of the ring resonator 26) guides the light along the ring resonator 26.

[0412] With the resonant device 7c shown, Figure 16 depicts a schematic transmission measurement spectrum 8 generated by the ring resonator 7c. These sharp notches appear at multiples of the wavelength of the measured radiation 9. The distance between these sharp notches is determined by the geometry and / or diameter of the ring resonator 26. If the geometry of the ring resonator 26 changes, these notches move together or separately. By measuring the distance between these notches, the diameter and / or geometry of the ring resonator 7c can be deduced.

[0413] Alternatively or additionally, the position or phase of one or more notches to be measured in the measurement spectrum 8 may be provided, preferably an absolute position or phase. Thus, the diameter and / or geometry of the ring resonator 7c can be derived particularly reliably and accurately.

[0414] FIG17 shows a perspective view of a possible embodiment of the optical device 1.

[0415] In this case, the optical fiber 11a is welded to the substrate element 10 by means of the welding glass 23.

[0416] Figure 18 shows another exemplary embodiment in which the optical fiber 11a is integrated into the substrate element 10, wherein the core 28 and cladding layer 27 of the optical fiber are again soldered to the substrate element 10 by means of the soldering glass 23. In this case, the fiber Bragg grating 7b is disposed in a groove 22 in the soldering glass 23 of the substrate element 10.

[0417] A protective coating (not depicted) and / or a sleeve (not depicted), such as a polymer sleeve, which may surround the core 28 and remove the coating 27 in the welding area, since high temperatures may cause damage to the protective coating and / or the sleeve.

[0418] The welding glass 23 can be processed at a temperature of 200°C to 500°C, preferably 350°C to 450°C, while the core 28 and / or cladding layer 27 of the optical fiber 11a preferably have a melting temperature of 1500°C to 1800°C.

[0419] can better provide that the refractive index change of the core 28 will not be damaged by the high temperature during melting or welding.

[0420] In this case, multiple femtosecond write grating devices 7a and / or fiber Bragg gratings 7b may be provided to be exposed to temperatures below 1100°C, preferably below 900°C, and more preferably below 800°C during melting or welding.

[0421] The femtosecond write grating device 7a and / or fiber Bragg grating 7b can be provided to withstand heat up to at least 800°C, preferably at least 900°C, and more preferably at least 1100°C during melting or welding.

[0422] In addition, multiple UV-written grating devices 7a and / or fiber Bragg gratings 7b can be exposed to temperatures below 800°C, preferably below 500°C, during melting or welding.

[0423] The UV-written grating devices 7a and / or fiber Bragg gratings 7b can be provided to withstand temperatures of at least 500°C, preferably at least 800°C, during melting or welding.

[0424] Figure 19 shows an embodiment of an apparatus 35 for manufacturing an optical device 1. In particular, the optical device 1 can be manufactured by the apparatus 35 in such a manner that at least one waveguide 11 and / or at least one grating device 7a and / or at least one resonant device 7c are formed from a substrate element 10.

[0425] The described apparatus 35 is configured to write a change in refractive index into an initial material of the substrate element 10 by means of high-energy writing radiation 36. By changing the radiation intensity of the writing radiation 36, the change in refractive index can be set for forming a line grating device 29. Therefore, a strain gauge device 5 or a portion thereof can be directly written into the substrate element 10 and / or the optical surface 3.

[0426] The optical device 1 is particularly suitable for an optical element of a mirror M4 and / or M5 formed as an EUV projection exposure device 100 according to FIG1.

[0427] The features mentioned in the exemplary embodiments of Figures 3 to 19 can also be implemented in other exemplary embodiments. In particular, a plurality of optical fibers configured in the optical element 2 in the manner described in Figures 5, 6, 7, 18 and / or 19 can also be used.

[0428] The embodiments described in the context of the optical device 1 and / or the method according to the present invention can also be regarded as disclosing the manufacturing method of the optical element 2 according to the present invention.

Claims

1. An optical device for a lithography system, comprising: a mirror, including: a substrate element; an optical surface supporting the substrate element; a strain gauge; an actuator for deforming the optical surface; and a closed-loop control device; wherein: The strain gauge device includes: (i) a path length device for generating a measurement spectrum of a measurement radiation; and (ii) a waveguide configured to guide the measurement radiation to the path length device; the path length device includes a grating device for the measurement radiation and / or a resonant device for the measurement radiation; the strain gauge device is configured to determine an actual strain in a measurement region of the mirror, which is determined based on the actual deformation of the optical surface; the path length device is at least partially disposed in the substrate element; the waveguide is at least partially disposed in the substrate element; the closed-loop control device includes a closed loop for setting a target strain in the measurement region by means of the actuator, wherein the actual strain in the measurement region determined by the strain gauge device is taken into account; the closed-loop control device is configured to correct for temperature-induced deviations between the actual deformation of the optical surface and the target deformation, and / or strain-induced deviations between the actual deformation of the optical surface and the target deformation; and the substrate element comprises SiO2-TiO2 glass.

2. The optical device as claimed in claim 1, wherein the strain gauge device is at least partially disposed within the at least one measurement area.

3. The optical device as claimed in claim 1, wherein the strain gauge device includes a plurality of path length devices, and the waveguide system is configured to guide the measurement radiation to the plurality of path length devices.

4. The optical device as claimed in claim 1, wherein the grating device comprises a fiber Bragg grating.

5. The optical device as claimed in claim 1, wherein at least one of the following is true: the optical device comprises a plurality of measurement regions at different depths in the substrate element; and / or the plurality of measurement regions are located in a strain neutral plane of the substrate element.

6. The optical device as claimed in claim 1, wherein the closed-loop control device sets the target strain of the measurement region by means of the actuator, wherein the actual strain of the measurement region determined by the strain gauge device is taken into account.

7. The optical device as claimed in claim 1, wherein the measurement region comprises a plurality of measurement regions located on the mirror and arranged on the mirror in such a way that the deformation of the optical surface related to the optical effect caused by the mirror is measurable.

8. The optical device as claimed in claim 1, wherein a computing device is provided to determine, from the determined actual strain in the measurement area, the actual deformation of the optical surface, and / or the appropriate force of the actuator for setting the target deformation of the optical surface.

9. The optical device as claimed in claim 1 further includes a plurality of actuators and a plurality of measurement regions, wherein each actuator is assigned to a measurement region, the measurement region including an effective area relative to the actuator.

10. The optical device as claimed in claim 1, wherein the strain gauge device is configured to regularly determine the strain of the measurement area and / or multiple vibrations of the optical surface.

11. The optical device as claimed in claim 1, wherein one or more measurement areas are disposed on and / or therein the mirror. This makes one or more vibration modes of the optical surface and / or the mirror determinable.

12. The optical device as claimed in claim 1, wherein the optical device is a projection object comprising at least five mirrors that penetrate the projection object along a beam path, and the mirror being a fourth mirror that penetrates the projection object along the beam path.

13. The optical device as claimed in claim 1, wherein the optical device is a projection object comprising at least five mirrors that penetrate the projection object along a beam path, and the mirror being a fifth mirror that penetrates the projection object along the beam path.

14. The optical device as claimed in claim 1, wherein the path length device includes a resonant device.

15. A photolithography apparatus, comprising: a radiation source; an optical unit including the optical device described in claim 1; wherein the photolithography apparatus is a semiconductor photolithography projection apparatus.

16. A method for setting a target deformation of an optical surface of a mirror using a lithography system with one or more actuators, comprising: determining an actual deformation of the optical surface by measuring at least one actual strain in at least one measurement area of ​​the mirror to be determined; wherein: The at least one measurement region is configured in such a way that the actual deformation of the optical surface can be derived from the actual strain; the actual strain is determined in one or more measurement regions of the optical surface supported by the at least one substrate element; the relative actual strain in the plurality of measurement regions is determined at different depths of the substrate element and / or the actual strain is determined in a strain-neutral plane of the substrate element in at least one of the plurality of measurement regions; and the substrate element comprises SiO2-TiO2 glass.

17. The method as described in claim 16, wherein the force system of at least one actuator that needs to set a target deformation of the optical surface is determined and / or implemented based on the determined actual deformation of the optical surface.

18. A method for manufacturing a mirror for a lithography system containing an optical surface, the mirror comprising a substrate element and an optical surface supported by the substrate element, wherein the optical surface is deformable by an actuator, wherein the mirror includes a strain gauge device for determining the deformation of the optical surface, wherein the strain gauge device includes at least one path length device for generating a measurement spectrum, the strain gauge device further including a waveguide configured to guide a measurement radiation to the path length device, wherein the path length device includes a grating device for the measurement radiation and / or a resonant device for the measurement radiation, the method comprising: the strain gauge device in the substrate element being directly written by a local change in the refractive index; wherein the substrate element comprises SiO2-TiO2 glass.

19. The manufacturing method as described in claim 18, wherein directly writing to the strain gauge device comprises using a laser pulse having a pulse duration of 1 to 15 femtoseconds.

20. The manufacturing method as described in claim 19, wherein the laser pulse is within an ultraviolet spectral range.

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