METHOD FOR EXAMINING A SUBSTRATE BODY FOR A COMPONENT OF A LITHOGRAPHING PLANT, SUBSTRATE BODY AND LITHOGRAPHING PLANT

Abstract

Method for examining a substrate body (108) for a component (102) of a lithography system (1), comprising the steps: a) Generating (S1) at least one marking (112) in an interior (114) of the substrate body (108), b) Emitting (S3) an ultrasound signal (134) and receiving an ultrasound signal (136) reflected at the at least one mark (112), and c) Determine (S4), spatially resolved, one or more parameters (P) of the substrate body (108) based on the received ultrasound signal (136).

Description

[0001] The present invention relates to a method for examining a substrate body for a component of a lithography system, such a substrate body and a lithography system with such a substrate body.

[0002] Microlithography is used to manufacture microstructured components, such as integrated circuits. The microlithography process is carried out using a lithography system, which includes an illumination system and a projection system. The image of a mask (reticule) illuminated by the illumination system is projected by the projection system onto a substrate, such as a silicon wafer, coated with a photosensitive layer (photoresist) and positioned in the image plane of the projection system. This transfers the mask structure onto the photosensitive coating of the substrate.

[0003] Driven by the pursuit of ever smaller structures in the fabrication of integrated circuits, EUV lithography systems are currently being developed that use light with a wavelength in the range of 0.1 nm to 30 nm, particularly 13.5 nm. Since most materials absorb light of this wavelength, such EUV lithography systems must use reflective optics, i.e., mirrors, instead of the refracting optics, i.e., lenses, used previously.

[0004] One problem that arises is that the mirrors heat up as a result of absorbing the radiation emitted by the EUV light source. This can lead to thermal deformation of the mirrors. Furthermore, an increase in temperature can also degrade any optical coating on the mirrors. Both thermal deformation of the mirrors and damage to their optical coatings can impair the imaging properties of the mirrors.

[0005] The image quality of projection systems in an EUV lithography system depends heavily on the quality of the mirror material. To minimize aberrations caused by mirror heating, a material with a very low coefficient of thermal expansion is used for the mirror substrate. Specifically, at the so-called zero-crossing temperature of the mirror material's coefficient of thermal expansion, deformation of the mirror material as a function of temperature increase is minimal and / or nonexistent. Variations in the coefficient of thermal expansion or the zero-crossing temperature within the mirror substrate volume have a direct impact on aberrations caused by mirror heating.

[0006] Against this background, one object of the present invention is to provide an improved method for examining a substrate body for a component of a lithography system.

[0007] According to a first aspect, a method for examining a substrate body for a component of a lithography system is proposed. The method comprises the following steps: a) Creating at least one mark in an interior of the substrate body, b) Emitting an ultrasound signal and receiving an ultrasound signal reflected at the at least one marker, and c) Determine, with spatial resolution, one or more parameters of the substrate body based on the received ultrasound signal.

[0008] This method allows for the simple, spatially resolved determination of one or more parameters that vary across the volume of the substrate body of a lithography system component. Specifically, at least one marker is created within the substrate body. This divides the substrate volume into multiple volume elements (voxels) with respect to the reflection of the ultrasound signal. The ultrasound signal, emitted from a top surface onto the substrate body, is reflected at a bottom surface opposite the top surface and thus contains information about the volume range of the substrate body traversed from the top surface to the bottom surface.Secondly, the ultrasound signal emitted from the top surface onto the substrate is reflected at the at least one marker and thus contains information about the volume range traversed from the top surface to the at least one marker. With exactly one marker, the substrate is therefore divided into exactly two volume elements: a first from the top surface to the marker and a second from the marker to the bottom surface. With multiple markers, the substrate is divided into multiple volume elements accordingly. For each volume element, one or more parameters can be determined separately based on the corresponding reflected ultrasound signal components, allowing the parameter(s) to be determined with spatial resolution.Consequently, with an increasing number of markers, the spatial resolution in determining the parameter(s) can be increased – especially if the markers are evenly distributed over the substrate body.

[0009] The lithography system (projection exposure system) can be an EUV lithography system. EUV stands for "Extreme Ultraviolet" and refers to a wavelength of the working light between 0.1 nm and 30 nm, particularly 13.5 nm. The lithography system can also be a DUV lithography system. DUV stands for "Deep Ultraviolet" and refers to a wavelength of the working light between 30 nm and 250 nm. The lithography system comprises an illumination system and a projection system. Specifically, the lithography system projects the image of a mask (reticule) illuminated by the illumination system onto a substrate, such as a silicon wafer, coated with a photosensitive layer (photoresist) and positioned in the image plane of the projection system, in order to transfer the mask structure onto the photosensitive coating of the substrate.

[0010] The component of the lithography system is, for example, an optical component, e.g., a mirror or a lens, or a mechanical component, e.g., a support or the like.

[0011] The component is preferably used in a projection optic of the projection exposure system. However, the component can also be used in a lighting system.

[0012] The substrate body is, in particular, a three-dimensional body. The substrate body is, in particular, a solid body. The one or more parameters of the substrate body determined in step c) of the method are, for example, parameters and / or properties of a material of the substrate body (i.e., material parameters or material properties). For example, the substrate body exhibits variations of the one or more parameters throughout its volume. These variations can be determined using the proposed method. In other words, the proposed method determines a spatially dependent distribution of the one or more parameters throughout the volume of the substrate body.

[0013] Based on one or more spatially resolved parameters of the substrate, the degree of inhomogeneity of that parameter can be determined. This allows for verification of the substrate's quality. For example, based on the determined degree of inhomogeneity of that parameter, the suitability of the substrate for a predetermined use in the lithography system can be verified.

[0014] As an example, one substrate material is titanium-doped glass, and in step c) a spatially resolved coefficient of thermal expansion of the substrate is determined. This means that a spatially dependent distribution of the coefficient of thermal expansion across the volume of the substrate is determined. If it is determined that the inhomogeneities of the coefficient of thermal expansion are smaller than a predetermined threshold, then it can be determined that the investigated substrate is suitable for use as a mirror substrate for a lithography system – for example, without further modification.If it is determined that the inhomogeneities of the coefficient of thermal expansion are greater than a predetermined threshold, then the substrate body and / or its surface can be appropriately treated based on the determined spatial distribution of the coefficient of thermal expansion in order to compensate for the determined inhomogeneities of the coefficient of thermal expansion.

[0015] The at least one marking indicates, for example, a change in the material of the substrate body. The at least one marking indicates, for example, one or more cracks in a material of the substrate body. The at least one marking indicates, for example, several cracks arranged within a substantially spherical volume in a material of the substrate body.

[0016] The fact that at least one marking is created inside the substrate body also means that it is placed and / or arranged inside the substrate body.

[0017] The at least one marking is generated exclusively within the substrate body, i.e., placed there. No markings are generated on the surface of the substrate body. In other words, the at least one marking is generated in step c) in such a way that the surface of the substrate body is free of the at least one marking.

[0018] The at least one marker is generated, for example, at at least one pre-determined position inside the substrate body. Furthermore, one or more parameters of the substrate body are determined based on the received ultrasound signal and, additionally, based on the pre-determined position. For example, based on the received ultrasound signal, the transit time of the ultrasound signal (e.g., to the at least one marker) is determined. Furthermore, based on the determined transit time and the pre-determined position of the at least one marker, the propagation speed of the ultrasound signal within the substrate body, specifically within each of the volume elements of the substrate body, is determined. Based on the determined propagation speed of the ultrasound signal, the one or more parameters can then be determined.

[0019] The ultrasound signal is transmitted and received, in particular, by an ultrasound sensor device. The received ultrasound signal is, in particular, an echo signal of the transmitted ultrasound signal. The received ultrasound signal exhibits, in particular, a reflection signal for each reflection (e.g., at the at least one marking and / or the bottom surface of the substrate).

[0020] The received ultrasound signal is, in particular, a time-dependent function. For example, the received ultrasound signal exhibits a time course corresponding to a sensor voltage output by the ultrasound sensor device. The sensor voltage indicates a received signal intensity, i.e., a detected sound pressure, as measured by the ultrasound sensor device. For each reflection, the received ultrasound signal exhibits, for example, an increase in the amplitude of the received signal intensity (i.e., a maximum and / or a peak in the received signal intensity as a function of time) as a corresponding echo signal. The associated time can thus be identified as the reception time of this echo signal. From this, the travel time can be determined.

[0021] The ultrasonic sensor device has, for example, an accuracy of 100 ns or less, 10 ns or less, 5 ns or less, 1 ns or less, and / or 0.1 ns (i.e., 100 ps) or less. In other words, the ultrasonic sensor device is designed to determine the transit time of the ultrasonic signal with the specified accuracy. However, the ultrasonic sensor device can also have a different accuracy with respect to time measurement.

[0022] The substrate body can be examined, for example, using an ultrasound signal as a longitudinal wave and / or as a transverse wave.

[0023] Longitudinal and transverse waves, for example, have different speeds, and these speeds can be converted into other quantities. For instance, the material property of elastic modulus can be determined from the speed of sound of a longitudinal wave. Similarly, the material property of shear modulus can be determined from the speed of sound of a transverse wave.

[0024] Whether a longitudinal or a transverse wave is generated by the ultrasound device depends on the direction of movement of a transducer within the device. If the transducer oscillates parallel to the direction of wave propagation, a longitudinal wave is formed. If the transducer oscillates perpendicular to the direction of wave propagation, a transverse wave is formed. A transverse wave can also be generated in the substrate by directing an ultrasound longitudinal wave at an angle other than 90°, i.e., not perpendicular, onto a surface of the substrate (e.g., at an angle of 45°). When the tilted ultrasound longitudinal wave then strikes the surface of the substrate, an ultrasound transverse wave is generated within the substrate.

[0025] The determination of the parameter(s) is carried out, for example, by a control unit.

[0026] The control unit can optionally be configured to process the received ultrasound signal in such a way as to extract signals with a low signal-to-noise ratio from the ultrasound signal. For example, the substrate body can be scanned (i.e., rasterized) with a measuring head of the ultrasound sensor device to detect an increase in the reflected signal as the measuring head approaches a marker and a decrease in the reflected signal as the measuring head moves away from the marker (synthetic aperture focusing technique, SAFT). However, other methods can also be used to extract signals with a low signal-to-noise ratio, such as pulse compression, in which an outgoing pulse is cross-correlated with the echo.

[0027] For example, the method is carried out using an examination device which includes a marking generation device for generating the at least one marking, the ultrasonic sensor device and the control device.

[0028] According to one embodiment, the at least one marking has at least one engraving.

[0029] The at least one marking exhibits, in particular, a local change in the material at the location of the corresponding marking. For example, the at least one marking exhibits a physical and / or chemical change in the material at the location of the corresponding marking.

[0030] According to another embodiment, the at least one marking is produced by means of laser engraving.

[0031] Laser engraving allows for the creation of at least one very small marking (e.g., 100 µm or smaller, 50 µm or smaller, 10 µm or smaller, and / or 1 µm or smaller). This enables virtually non-destructive examination of the substrate using this method.

[0032] In laser engraving, at least one marking is created, in particular, by heating a portion of the substrate material at a predetermined location within the substrate using a laser beam. The substrate material is heated locally in the area of ​​the focal point of the incident laser light. The power density of the laser beam can be so high at the point of marking that the material melts there. By using a highly focused laser beam, the heat input into the material can be significantly limited locally. If a pulsed laser beam is also used, the heat input into the material can be significantly limited in duration as well. Because the substrate material is only heated intensely locally at the point of marking, while adjacent areas of the material remain unheated, cracks and / or fractures occur in the material at the point of marking.

[0033] The laser beam used, for example, has a wavelength in the range of 380 nm to 1400 nm (visible light and near-infrared). The laser beam used, for example, has a wavelength in the range of 500 nm to 570 nm (green light). The laser beam used, for example, has a wavelength in the range of 780 nm to 1400 nm (near-infrared light). The laser beam used, for example, has a wavelength of 1030 nm. However, the laser beam used can also have a different wavelength.

[0034] The laser beam used is, for example, a pulsed laser beam. One pulse length is, for example, 6.5 ps. However, the pulse length of the laser beam used can also have a different value.

[0035] The applied laser beam is, for example, highly focused and therefore has a small laser spot size (i.e., a small beam cross-section) at the processing point (i.e., at the location of the marking). One can also say that the applied laser beam has a large divergence angle. The divergence angle is defined as the angle by which the laser beam spreads out in the far field, using the beam waist (which corresponds to the laser spot size at the processing point) as a reference. That is, the smaller the laser spot size at the processing point, the larger the divergence angle.

[0036] Due to the small laser spot size, a very high energy density can be provided at the location of the marking, while virtually no laser energy reaches neighboring locations.

[0037] Example values ​​for the laser spot size are 50 µm or smaller, 10 µm or smaller and / or 1 µm or smaller.

[0038] Example values ​​for the numerical aperture dependent on the divergence angle are 0.1 or greater, 0.5 or greater and / or 0.8 or greater.

[0039] According to another embodiment, a predetermined laser wavelength is used in the laser engraving process, and the substrate body is transparent to the predetermined laser wavelength.

[0040] For example, at least one marking can be created on a glass material and / or a transparent plastic (e.g. Plexiglas) using a laser wavelength in the visible spectral range.

[0041] For example, at least one marking on a silicon material (e.g., silicon single crystal) can be generated using a laser wavelength in the infrared spectral range. In particular, silicon is transparent to infrared light, although it is non-transparent (opaque) to visible light.

[0042] According to another embodiment, the size of the at least one marking is 100 µm or less, 50 µm or less, 30 µm or less, 10 µm or less, 5 µm or less and / or 1 µm or less.

[0043] Because the at least one mark generated inside the substrate body is very small, the substrate body can be examined virtually non-destructively using this method.

[0044] In embodiments, the size of the at least one marking is, for example, at least 1 µm and / or at least 5 µm, in order to enable detection of the at least one marking by means of ultrasound.

[0045] The size of the at least one marking is, for example, its maximum outer dimension. The at least one marking can, for example, have an essentially circular shape; in that case, its size is, for example, its diameter.

[0046] According to a further embodiment, several markings are created inside the substrate body, dividing it into multiple volume elements. Furthermore, the received reflected ultrasound signal has a corresponding reflected signal component for each marking. Finally, one or more parameters for each volume element are determined based on this reflected signal component.

[0047] This allows for an increase in spatial resolution when examining the substrate. Thus, the distribution of one or more parameters of the substrate can be determined with higher spatial resolution.

[0048] By way of example only, 100 or more markings, 500 or more markings and / or 1000 or more markings can be created in the substrate body.

[0049] In this context, “multiple markings” means, in particular, several of the at least one marking.

[0050] The multiple markings are arranged at a distance from each other.

[0051] The respective distance between the multiple markings defines, in particular, a spatial resolution when determining the parameter(s) in step S4. Specifically, the spatial resolution is greater the smaller the respective distance between the multiple markings.

[0052] A distance between two adjacent markings is, for example, 0.005 cm or more, 0.01 cm or more, 0.05 cm or more, 0.1 cm or more, 0.5 cm or more, 1 cm or more, 2 cm or more, and / or 3 cm or more. Additionally or instead, a distance between two adjacent markings is, for example, 3 cm or less, 2 cm or less, 1 cm or less, 0.5 cm or less, and / or 0.1 cm or less.

[0053] Furthermore, the size of each of the multiple markers can be many times smaller (e.g., 10 times or more, 50 times or more, and / or 100 times or more) than the distance between (e.g., each) two adjacent markers within the multiple markers. This facilitates the detection of the markers in the deeper layers of the substrate body using ultrasound in step S3.

[0054] Furthermore, the number of volume elements can be greater than the number of markings, for example, because a reflection of the emitted ultrasound signal also occurs on the bottom side of the substrate body, resulting in at least one additional volume element.

[0055] According to another embodiment, several markings are generated inside the substrate body, which are arranged accordingly at or adjacent to grid points of a regular three-dimensional grid.

[0056] By arranging the multiple markers evenly, the location-dependent distribution of one or more parameters can be determined more accurately.

[0057] An arrangement of multiple markings at grid points of a regular three-dimensional grid means, in particular, that the multiple markings are arranged at equal intervals from each other.

[0058] Some of the multiple markers may not be positioned precisely at the grid points of the grid, but rather adjacent to them. For example, some of the multiple markers may be positioned at an offset that is a multiple (e.g., two to ten times) of their size from the respective grid point. This facilitates detection with the ultrasound signal. In particular, the multiple markers may be arranged within the substrate body such that, when projected onto a plane perpendicular to an incident direction of the ultrasound signal, they are all spaced apart from one another.

[0059] According to a further embodiment, a position of the at least one marking is determined, and one or more parameters of the substrate body are determined based on the determined position, and The position of the at least one marking is determined based on the operating parameters of a laser when the at least one marking is generated, and / or The position of at least one marking is determined based on an optical measurement.

[0060] By determining the position of at least one marker, the speed of sound for the at least one marker can be determined from the determined position and a recorded transit time of the ultrasound signal.

[0061] The operating parameters of the laser when generating the at least one marking include, for example, a position of a laser head of the laser (for example, in three spatial directions spanning a three-dimensional space, and / or with respect to a rotation about the three spatial directions), a working distance of the laser from the at least one marking, a focusing degree of the laser (i.e., a divergence angle of the laser), a wavelength of the laser, or the like.

[0062] The optical measurement includes, for example, an interferometric measurement. The optical measurement is performed, for example, using one or more interferometers. The optical measurement is performed, in particular, before step c). Furthermore, the optical measurement can be performed before or after step b).

[0063] Optical measurement of the position of at least one marking allows for a more precise determination of its location. Consequently, one or more parameters of the substrate can be determined even more accurately (especially with higher spatial coordinate accuracy). For example, optical measurement of the position of at least one marking can be performed in addition to determining its position based on the laser's operating parameters.

[0064] As an example, an initial position determination for all markings of at least one marker can be carried out based on the laser's operating parameters. Furthermore, a second position determination can be performed for some of the markings (or alternatively for all of them) using optical measurement. Then, based on a comparison of the second position determination with the first, any systematic error in the first position determination can be identified and taken into account.

[0065] According to a further embodiment, a sound velocity in the substrate body is determined with spatial resolution based on the received ultrasound signal, and one or more parameters of the substrate body are determined based on the determined sound velocity.

[0066] The speed of sound within the substrate is determined based on the position of at least one marker and the measured transit time of the ultrasound signal to that marker. Specifically, the speed of sound within the volume element defined by each marker is determined based on the position of that marker and the measured transit time of the ultrasound signal upon reflection at that marker. Consequently, a location-dependent speed of sound can be determined for each of the at least one marker. From this location-dependent speed of sound, the location-dependent parameter(s) of the substrate can then be determined.

[0067] According to another embodiment, the substrate body material comprises glass, high-performance glass, titanium-doped glass, silicon and / or plastic.

[0068] High-performance glass is characterized by a material with a low (e.g., ultra-low) coefficient of thermal expansion. For example, the coefficient of thermal expansion of high-performance glass at a desired operating temperature lies within a range of ± 20 ppb / K (parts per billion per Kelvin), ± 15 ppb / K, ± 10 ppb / K, and / or ± 5 ppb / K. However, the coefficient of thermal expansion of high-performance glass can also lie within a different range. In such high-performance glass, changes in geometric shape and dimensions due to temperature variations occur only to a very small degree.

[0069] Examples of high-performance glass materials include titanium-doped glass, such as a TiO₂-SiO₂ glass material, where the ultra-low coefficient of thermal expansion is achieved by varying the TiO₂ concentration (e.g., a substrate material marketed by Corning Inc. under the name "ULE" for "Ultra-Low Expansion"). Another example of a high-performance glass is a Li₂O-Al₂O₃-SiO₂ glass-ceramic (marketed by Schott under the name "Zerodur") with a crystalline phase, where the ultra-low coefficient of thermal expansion is achieved by uniformly distributed nanocrystals in a residual glass phase.

[0070] For example, a silicon-containing substrate material could be a silicon single crystal used for mirror substrates. Silicon is particularly transparent to infrared light.

[0071] If the substrate body material is plastic, it could be, for example, Plexiglas or another plastic that is transparent to selected wavelengths of laser light.

[0072] According to another embodiment, one or more parameters of the substrate body have: one or more mechanical, thermal and / or acoustic parameters, and / or a coefficient of thermal expansion, a zero-crossing temperature, a modulus of elasticity, a shear modulus, a Poisson's ratio and / or an acoustic impedance.

[0073] The method can be used to determine all parameters (e.g. material parameters and / or material properties) of the substrate body that influence the propagation of sound and thus the speed of sound in a material of the substrate body.

[0074] The coefficient of thermal expansion indicates the change in the geometric shape and dimensions of a material when its temperature changes. For example, a linear coefficient of thermal expansion indicates the change in length of a material as a function of temperature.

[0075] The coefficient of thermal expansion is itself temperature-dependent, i.e., a temperature-dependent function. At its zero-crossing temperature (ZCT), the coefficient of thermal expansion exhibits a zero crossing in its temperature dependence, in the vicinity of which no or only negligible thermal expansion of the material occurs when the temperature changes.

[0076] The modulus of elasticity (Young's modulus) indicates the proportional relationship between applied stress and resulting strain during deformation of the substrate body in the case of linear-elastic behavior.

[0077] The shear modulus (shear modulus) indicates the relationship between applied shear stress and resulting shear strain (shear angle, slippage) in a linear-elastic structure.

[0078] The Poisson number describes the transverse contraction behavior of the substrate body.

[0079] As an example, one substrate material is titanium-doped glass, and in step c) a spatially resolved coefficient of thermal expansion of the substrate is determined. For titanium-doped glass, the coefficient of thermal expansion can be determined particularly from the speed of sound of the ultrasonic signal, since the speed of sound in the substrate depends on the titanium content.

[0080] Another example is that the substrate material is a glass-ceramic with a crystalline phase (e.g., "Zerodur") and a spatially resolved coefficient of thermal expansion of the substrate is determined in step c). For a glass-ceramic with a crystalline phase, the coefficient of thermal expansion can be determined based on the speed of sound of the ultrasonic signal because the speed of sound in the substrate depends on the presence of crystalline and amorphous phases.

[0081] According to another embodiment, step b) is performed using an ultrasonic microscope.

[0082] The substrate body can be scanned using an ultrasound microscope (Scanning Acoustic Microscope, SAM).

[0083] According to another embodiment, the component of the lithography system is a mirror of the lithography system, and the substrate body is a body of a mirror substrate of the mirror.

[0084] According to a second aspect, a substrate body for a component of a lithography system is proposed. The substrate body has at least one marking at at least one predetermined position inside the substrate body, wherein the at least one marking is configured to reflect an ultrasonic signal.

[0085] A third aspect is the proposal for a lithography system. This system includes a component with a substrate body as described above.

[0086] According to another aspect, a computer program product is proposed which includes instructions that, when executed by at least one computer, cause it to perform at least part of the procedure described above. For example, the computer program product is configured to receive the reflected ultrasound signal from an ultrasound sensor device. The computer program product is also configured, for example, to perform step c) of the procedure.

[0087] A computer program product, such as a computer program tool, can be provided or delivered, for example, as a storage medium such as a memory card, USB stick, CD-ROM, DVD, or as a downloadable file from a server on a network. This can be done, for example, in a wireless communication network by transmitting the corresponding file containing the computer program product or tool.

[0088] According to another aspect, an inspection device for examining a substrate body for a component of a lithography system is proposed. The inspection device comprises: a marking generation device as described above, an ultrasonic sensor device as described above, and a control device as described above.

[0089] The term "one" here is not necessarily to be understood as restricting the number to exactly one element. Rather, it can also refer to multiple elements, such as two, three, or more. Similarly, every other counter used here should not be interpreted as restricting the number to the exact number stated. Instead, numerical deviations, both higher and lower, are possible unless otherwise specified.

[0090] The embodiments and features described for the process apply accordingly to the proposed substrate body and the lithography system, and vice versa.

[0091] Other possible implementations of the invention also include combinations of features or embodiments described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In such cases, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0092] Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the exemplary embodiments of the invention described below. The invention will be explained in more detail below with reference to preferred embodiments and the accompanying figures. Fig. Figure 1 shows a schematic meridional section of a projection exposure system for EUV projection lithography according to one embodiment; Fig. Figure 2 shows an optical component of the projection exposure system. Fig. 1 according to one embodiment; Fig. Figure 3 shows a flowchart illustrating a method for examining a substrate body for a component of a projection exposure system according to one embodiment: Fig. 4 shows a substrate body of the component made of Fig. 2 according to an embodiment during a process step of the process from Fig. 3; Fig. 5 shows a substrate body of the component made of Fig. 2 according to one embodiment during the generation of markings; Fig. Figure 6 shows a marking of the substrate body made of Fig. 4 or Fig. 5 according to one embodiment; Fig. 7 shows a similar view Fig. 5, wherein volume elements associated with the markings are indicated; and Fig. 8 shows a similar view Fig. 7, illustrating an ultrasound examination of the markings.

[0093] In the figures, identical or functionally equivalent elements have been labelled with the same reference symbols, unless otherwise indicated. Furthermore, it should be noted that the representations in the figures are not necessarily to scale.

[0094] Fig. Figure 1 shows an embodiment of a projection exposure system 1 (lithography system), in particular an EUV lithography system. One embodiment of the illumination system 2 of the projection exposure system 1 has, in addition to a light or radiation source 3, an illumination optic 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a separate module from the rest of the illumination system 2. In this case, the illumination system 2 does not include the light source 3.

[0095] A reticule 7 arranged in the object field 5 is exposed. The reticule 7 is held by a reticule holder 8. The reticule holder 8 can be moved, particularly in a scanning direction, via a reticule displacement drive 9.

[0096] In the Fig. Figure 1 shows a Cartesian coordinate system with an x-direction x, a y-direction y, and a z-direction z. The x-direction x runs perpendicular to the plane of the drawing. The y-direction y runs horizontally, and the z-direction z runs vertically. The scan direction runs in the Fig. 1 along the y-direction y. The z-direction z runs perpendicular to the object plane 6.

[0097] The projection exposure system 1 comprises a projection optic 10. The projection optic 10 serves to image the object field 5 onto an image field 11 in an image plane 12. The image plane 12 is parallel to the object plane 6. Alternatively, an angle other than 0° between the object plane 6 and the image plane 12 is also possible.

[0098] A structure on the reticulum 7 is imaged onto a photosensitive layer of a wafer 13 located in the image plane 12 within the image field 11. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be moved, particularly along the y-direction y, via a wafer transfer drive 15. The movement of the reticulum 7 via the reticulum transfer drive 9 and of the wafer 13 via the wafer transfer drive 15 can be synchronized.

[0099] Light source 3 is an EUV radiation source. Light source 3 emits, in particular, EUV radiation 16, which is also referred to below as useful radiation, illumination radiation, or illumination light. The useful radiation 16 has a wavelength in the range between 5 nm and 30 nm. Light source 3 can be a plasma source, for example, an LPP source (Laser Produced Plasma) or a DPP source (Gas Discharged Produced Plasma). It can also be a synchrotron-based radiation source. Light source 3 can be a free-electron laser (FEL).

[0100] The illumination radiation 16 emanating from the light source 3 is focused by a collector 17. The collector 17 can be a collector with one or more ellipsoidal and / or hyperboloid reflective surfaces. The at least one reflective surface of the collector 17 can be illuminated by the illumination radiation 16 at grazing incidence (GI), i.e., with angles of incidence greater than 45°, or at normal incidence (NI), i.e., with angles of incidence less than 45°. The collector 17 can be structured and / or coated to optimize its reflectivity for the useful radiation and to suppress stray light.

[0101] After the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 can represent a separation between a radiation source module, comprising the light source 3 and the collector 17, and the illumination optics 4.

[0102] The illumination optics 4 comprise a deflecting mirror 19 and, downstream in the beam path, a first faceted mirror 20. The deflecting mirror 19 can be a planar deflecting mirror or, alternatively, a mirror with an effect that influences the beam shape beyond the mere deflection effect. Alternatively or additionally, the deflecting mirror 19 can be designed as a spectral filter that separates a useful wavelength of the illumination radiation 16 from stray light of a different wavelength. If the first faceted mirror 20 is arranged in a plane of the illumination optics 4 that is optically conjugate to the object plane 6 as the field plane, it is also referred to as a field faceted mirror. The first faceted mirror 20 comprises a plurality of individual first facets 21, which can also be referred to as field facets. Of these first facets 21, the following are in the Fig. 1 only some examples are shown.

[0103] The first facets 21 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or semicircular border contour. The first facets 21 can be designed as planar facets or alternatively as convexly or concavely curved facets.

[0104] As is known, for example, from DE 10 2008 009 600 A1, the first facets 21 can themselves each be composed of a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirror 20 can in particular be designed as a microelectromechanical system (MEMS system). For details, reference is made to DE 10 2008 009 600 A1.

[0105] Between the collector 17 and the deflecting mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction y.

[0106] In the beam path of the illumination optics 4, a second faceted mirror 22 is arranged downstream of the first faceted mirror 20. If the second faceted mirror 22 is arranged in a pupil plane of the illumination optics 4, it is also referred to as a pupil faceted mirror. The second faceted mirror 22 can also be arranged at a distance from a pupil plane of the illumination optics 4. In this case, the combination of the first faceted mirror 20 and the second faceted mirror 22 is also referred to as a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1, EP 1 614 008 B1, and US 6,573,978.

[0107] The second facet mirror 22 comprises a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

[0108] The second facets 23 can also be macroscopic facets, which may, for example, have round, rectangular, or hexagonal edges, or alternatively, facets composed of micromirrors. Reference is also made to DE 10 2008 009 600 A1 in this regard.

[0109] The second facets 23 can have planar or alternatively convex or concave curved reflective surfaces.

[0110] The illumination optics 4 thus form a double-faceted system. This basic principle is also known as a honeycomb condenser (English: Fly's Eye Integrator).

[0111] It can be advantageous not to arrange the second faceted mirror 22 exactly in a plane that is optically conjugate to a pupil plane of the projection optics 10. In particular, the second faceted mirror 22 can be arranged tilted relative to a pupil plane of the projection optics 10, as described, for example, in DE 10 2017 220 586 A1.

[0112] With the aid of the second faceted mirror 22, the individual first facets 21 are imaged into the object field 5. The second faceted mirror 22 is the last beam-shaping, or indeed the last, mirror for the illumination radiation 16 in the beam path before the object field 5.

[0113] In another embodiment of the illumination optics 4, not shown, a transmission optic can be arranged in the beam path between the second facet mirror 22 and the object field 5, which contributes in particular to imaging the first facets 21 into the object field 5. The transmission optic can have exactly one mirror, or alternatively two or more mirrors, arranged one behind the other in the beam path of the illumination optics 4. The transmission optic can, in particular, comprise one or two mirrors for normal incidence (NI mirrors) and / or one or two mirrors for grazing incidence (GI mirrors).

[0114] The lighting optics 4, in the version shown in the Fig. Figure 1 shows exactly three mirrors after the collector 17, namely the deflecting mirror 19, the first faceted mirror 20 and the second faceted mirror 22.

[0115] In a further embodiment of the lighting optics 4, the deflecting mirror 19 can also be omitted, so that the lighting optics 4 after the collector 17 can then have exactly two mirrors, namely the first faceted mirror 20 and the second faceted mirror 22.

[0116] The mapping of the first facets 21 by means of the second facets 23 or with the second facets 23 and a transmission optic into the object plane 6 is regularly only an approximate mapping.

[0117] The projection optics 10 comprise a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

[0118] In the Fig. In the example shown, the projection optics 10 comprise six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or any other number of mirrors Mi are also possible. The projection optics 10 is a doubly obscured optic. The penultimate mirror M5 and the last mirror M6 each have an aperture for the illumination radiation 16. The projection optics 10 has an image-side numerical aperture that is greater than 0.5 and can also be greater than 0.6, for example, 0.7 or 0.75.

[0119] The reflective surfaces of the mirrors Mi can be designed as freeform surfaces without an axis of rotational symmetry. Alternatively, the reflective surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflective surface shape. The mirrors Mi, like the mirrors of the illumination optics 4, can have highly reflective coatings for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

[0120] The projection optics 10 has a large object-image offset in the y-direction y between a y-coordinate of a center of the object field 5 and a y-coordinate of the center of the image field 11. This object-image offset in the y-direction y can be approximately as large as a z-distance between the object plane 6 and the image plane 12.

[0121] The projection optics 10 can be anamorphic. In particular, they have different magnifications βx, βy in the x and y directions. The two magnifications βx, βy of the projection optics 10 are preferably (βx, βy) = (+ / - 0.25, + / - 0.125). A positive magnification β indicates a projection without image inversion. A negative magnification β indicates a projection with image inversion.

[0122] The projection optics 10 thus lead to a reduction in the x-direction x, that is, in the direction perpendicular to the scan direction, in a ratio of 4:1.

[0123] The projection optics 10 lead to a reduction of 8:1 in the y-direction y, that is, in the scan direction.

[0124] Other magnification ratios are also possible. Magnification ratios with the same sign and absolute value in the x and y directions (x, y), for example with absolute values ​​of 0.125 or 0.25, are also possible.

[0125] The number of intermediate image planes in the x and y directions x, y in the beam path between the object field 5 and the image field 11 can be the same or, depending on the design of the projection optics 10, different. Examples of projection optics with different numbers of such intermediate images in the x and y directions x, y are known from US 2018 / 0074303 A1.

[0126] Each of the second facets 23 is assigned to exactly one of the first facets 21 to form an illumination channel for illuminating the object field 5. This can result, in particular, in illumination according to Köhler's principle. The far field is divided into a multitude of object fields 5 with the help of the first facets 21. The first facets 21 generate a plurality of images of the intermediate focus on the second facets 23 assigned to each of them.

[0127] The first facets 21 are each superimposed on a corresponding second facet 23 to illuminate the object field 5 on the reticle 7. The illumination of the object field 5 is particularly homogeneous. It preferably exhibits a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

[0128] The illumination of the entrance pupil of the projection optics 10 can be geometrically defined by arranging the second facets 23. By selecting the illumination channels, in particular the subset of the second facets 23 that carry light, the intensity distribution in the entrance pupil of the projection optics 10 can be adjusted. This intensity distribution is also referred to as the illumination setting or illumination pupil filling.

[0129] Another preferred pupil uniformity in the area of ​​defined illuminated sections of an illumination pupil of the illumination optics 4 can be achieved by a redistribution of the illumination channels.

[0130] Further aspects and details of the illumination of the object field 5 and, in particular, the entrance pupil of the projection optics 10 are described below.

[0131] The projection optics 10 can, in particular, have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

[0132] The entrance pupil of the projection optics 10 cannot always be illuminated exactly by the second faceted mirror 22. When the projection optics 10 image the center of the second faceted mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, a surface can be found where the pairwise determined separation of the aperture rays is minimized. This surface represents the entrance pupil or a surface conjugate to it in real space. In particular, this surface exhibits a finite curvature.

[0133] The projection optics 10 may have different entrance pupil positions for the tangential and sagittal beam paths. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second faceted mirror 22 and the reticle 7. This optical element can accommodate the different positions of the tangential and sagittal entrance pupils.

[0134] During the Fig. In the arrangement of the components of the illumination optics 4 shown in Figure 1, the second faceted mirror 22 is arranged in a plane conjugate to the entrance pupil of the projection optics 10. The first faceted mirror 20 is arranged tilted relative to the object plane 6. The first faceted mirror 20 is arranged tilted relative to an arrangement plane defined by the deflecting mirror 19. The first faceted mirror 20 is arranged tilted relative to an arrangement plane defined by the second faceted mirror 22.

[0135] Fig. Figure 2 shows an optical system 100 (e.g., a part of an optical system 100) with an optical component 102 according to one embodiment. The optical component 102 has a substrate 104 and an optically active surface 106. The substrate 104, in particular, has a three-dimensional substrate body 108. The optical component 102 is, for example, a mirror with a mirror substrate 104 and a reflective surface 106.

[0136] The optical system 100 is, for example, a projection optic 10 of the EUV lithography system 1 ( Fig. 1) However, the optical system 100 can also be, for example, an illumination optic 4 of the lithography system 1.

[0137] The optical component 102 is, for example, one of the mirrors M1 to M6 of the projection optics 10 ( Fig. 1) The optical component 102 can, for example, also be one of the mirrors 19, 20, 22 of the lighting optics 4 ( Fig. 1) be.

[0138] Although not shown in the figures, the optical component 102 could also be a mirror or a lens of a DUV lithography system.

[0139] Although not shown in the figures, component 102 can also be a mechanical component of the lithography system 1 instead of an optical component.

[0140] It is desirable to investigate component 102 with regard to mechanical, thermal and / or acoustic parameters.

[0141] For example, the optical component 102 can be irradiated with working light 16 (e.g. EUV light 16 of the lithography system 1, Fig. 1) and absorption of the working light 16 heat up. This can cause the optical component 102 to thermally deform. This thermal deformation can lead to imaging errors of the optical component 102 or of the optical system 100, which includes the optical component 102.

[0142] To reduce thermal deformation and associated imaging errors, high-quality substrate material 110 is used for the substrate 104, i.e., the substrate body 108. In particular, the material 110 of the substrate body 108 has a very low coefficient of thermal expansion ρ. Specifically, the material 110 has a zero-crossing temperature ZCT of the coefficient of thermal expansion ρ at which thermal deformation of the material 110 as a function of temperature increase is minimal and / or zero. The material 110 is, for example, titanium-doped glass.

[0143] Due to inhomogeneities in the material 110 of the substrate body 108 (e.g., an inhomogeneous distribution of titanium content), the coefficient of thermal expansion ρ and / or the zero-crossing temperature ZCT of the substrate 104 cannot be homogeneously distributed over the substrate body 108, but rather exhibit fluctuations Δρ, ΔZCT as a function of the location r of the substrate body 108. The location r of the substrate body 108 is, for example, a location in the three-dimensional space spanned by the directions x, y', and z'. A (e.g. mean) value of the coefficient of thermal expansion ρ or the zero-crossing temperature ZCT of the material 110, as well as the variations Δρ of the coefficient of thermal expansion ρ as a function of the location r or the variations ΔZCT of the zero-crossing temperature ZCT as a function of the location r, have a direct influence on imaging errors of the optical component 102.

[0144] The following refers to the Fig. Sections 3 to 8 describe a method for investigating a substrate body 108 for a component 102 of a lithography system 1 according to an embodiment. The method can be used to investigate any parameters of the substrate body 108 that influence the speed of sound.

[0145] In a first step S1 of the process, at least one marking 112 is created in an interior 114 of the substrate body 108, as shown in Fig. 4 illustrates.

[0146] The at least one marking 112, for example, has at least one engraving 116, e.g., a laser engraving. The at least one marking 112 is applied, for example, by means of a marking generation device 118 ( Fig. 5) generated.

[0147] The at least one marking 112 is produced, for example, in step S1 by means of laser engraving. In this case, the marking generation device 118 ( Fig. 5) a laser for emitting a laser beam 120. In laser engraving, for example, a highly focused laser beam 120 is used. The laser beam 120 has, for example, a large divergence angle α, which results in a strong focus on a small beam cross-section at the processing location 122.

[0148] The laser beam 120, focused on the respective processing location 122 inside 114 of the substrate body 108, causes the material 110 of the substrate body 108 to be heated intensely at the respective processing location 122. This results in a local change 124 at the respective processing location 122 ( Fig. 6) of the material 110 of the substrate body 108. The modification 124, for example, exhibits several cracks 126 in the material 110, some of which are in Fig. 6 are marked with a reference symbol. The changes 124, for example, are limited to an essentially circular area 128.

[0149] The at least one marking 112, for example, has a size G ( Fig. 6) of 100 µm or less, 50 µm or less, 30 µm or less and / or 10 µm or less. Due to the very small size G of the at least one marking 112, the method can also be described as quasi-non-destructive.

[0150] In laser engraving, for example, a laser beam 120 with a predetermined laser wavelength λ ( Fig. 5) applied. Furthermore, the substrate body 108, 208 is transparent, for example, for the predetermined laser wavelength λ.

[0151] For example, laser engraving uses a highly focused laser beam 120° with a large divergence angle α.

[0152] As in Fig. As illustrated in Figure 5, several markings 212 can also be created inside the substrate body 208 in step S1. Fig. Figure 5 shows the substrate body 208 during processing with the marking generation device 118. Eight markings 212 have already been generated as examples, some of which are provided with a reference mark. Regarding the substrate body 208 in Fig. As an example, a total of 24 markings 212 are provided. However, significantly more markings 212 (e.g., 500 or more and / or 1000 or more markings 212) can also be provided. The more markings 212 are generated, the greater the spatial resolution will be in the subsequent ultrasound examination in step S3.

[0153] The multiple markings 212 are, for example, spaced apart from each other, see distances A1, A2 between adjacent markings 212 in Fig. 7.

[0154] As in Fig. As shown in Figure 5, the multiple markings 212 can be arranged accordingly at grid points 216 of a regular three-dimensional grid 218. Fig. Four of the grid points 216 are marked with a reference symbol as examples.

[0155] Optionally, some of the multiple markings 212, 212' may not be positioned exactly at the grid points 216 of the grid 218, but rather shifted by a small offset B – as exemplified by marking 212' in Fig. Figure 5 illustrates this. This facilitates the detection of markings 212, 212' in subsequent step S3.

[0156] If exactly one marker 112 is created in step S1 ( Fig. 4), then the substrate body 108 is thereby subdivided into two volume elements 130 (130a, 130b) for the subsequent ultrasound examination in step S3.

[0157] If multiple markings 212 are created in step S1 ( Fig. 5, Fig. 7), then the substrate body 208 is thereby divided into several volume elements 230 for the subsequent ultrasound examination in step S3 ( Fig. 7) subdivided. In Fig. Figure 7 shows some of the volume elements 230, each with a reference symbol.

[0158] In step S1, a position C (first position C) of at least one marking 112, 212 can also be determined ( Fig. 4, Fig. 5) The position C of the at least one marking 112, 212 is determined, for example, based on working parameters (e.g. the divergence angle α, the laser wavelength λ and / or other setting parameters) of a laser 118 when generating the at least one marking 112, 212.

[0159] In an optional second step S2 of the procedure, the position D (second position D) of the at least one marking 112, 212 is determined based on an optical measurement. For example, the position D (second position D) of the at least one marking 112, 212 is determined based on an interferometric measurement using an interferometer 132 ( Fig. 5) determined. This allows the position C, D of at least one marking 112, 212 to be determined even more precisely.

[0160] Step S2 can be performed before or after step S3.

[0161] In a third step S3 of the procedure, the substrate body 108, 208 is examined using ultrasound. In particular, an ultrasound signal 134 ( Fig. 4) emitted and receives an ultrasound signal 136 reflected at the at least one mark 112. The ultrasound signal 134 is, for example, emitted by an ultrasound sensor device 138 ( Fig. 8), e.g. an ultrasound microscope 140, emitted and received.

[0162] In the example of Fig. 4. A marker 112 was created inside 114 of the substrate body 108. The ultrasonic signal 134 emitted by the ultrasonic sensor device 138 is reflected at a base 142 of the substrate body 108 (reflected ultrasonic signal 136 with signal component 136a). The ultrasonic signal 134 emitted by the ultrasonic sensor device 138 is also reflected at the marker 112 of the substrate body 108 (reflected ultrasonic signal 136 with signal component 136b). The ultrasonic signal component 136a reflected at the base 142 thus contains information about volume 130a. Furthermore, the ultrasonic signal component 136b reflected at the marker 112 contains information about volume 130b. In particular, signal component 136a contains information about the travel time from a surface of the substrate body 108 to the ground 142. Furthermore, signal component 136b contains information about the travel time from the surface to the marker 112.Subtracting the travel time of signal component 136b from the travel time of signal component 136a yields the travel time from marker 112 to the ground 142. Using the previously known distances between the surface and marker 112, as well as between marker 112 and ground 142, the speed of sound in volume 130a and volume 130b can now be determined.

[0163] In the example of Fig. 5, Fig. 7 and Fig. Several markings 212 were created inside 214 of the substrate body 208. The ultrasonic signal 234 emitted by the ultrasonic sensor device 138 is reflected at a base 242 of the substrate body 208. Furthermore, the ultrasonic signal 234 emitted by the ultrasonic sensor device 138 is reflected at each of the markings 212 of the substrate body 208 (reflected ultrasonic signal 236 with signal components 236a to 236c from the markings 212a-212c). The signal component 236a of the ultrasonic signal 236 reflected at marking 212a contains information about volume 230a. Likewise, the signal component 236b of the ultrasonic signal 236 reflected at marking 212b contains information about volume 230b. Furthermore, the signal component 236c of the ultrasound signal 236 reflected at the marker 212c contains information about the volume range 230c.The same applies to the remaining markings 212 and volume elements 230 (without reference signs) in . Fig. 8.

[0164] In Fig. 7 and Fig. For the sake of clarity, only three of the markings 212 (212a to 212c) and three of the volume elements 230 (230a to 230c) are provided with a reference symbol. Furthermore, in Fig. 8 the ultrasound signals 234, 236 are shown for only three of the markings 212 and provided with reference marks.

[0165] In a fourth step S4 of the procedure, one or more parameters P of the substrate body 108, 208 are determined with spatial resolution based on the received ultrasound signal 136, 236.

[0166] In particular, in step S4 the received ultrasound signal 136, 236 is combined with the several reflected signal components 136a, 136b ( Fig. 4) or 236a to 236c ( Fig. 8) evaluated. The received ultrasound signal 136, 236 is, for example, transmitted by the ultrasound sensor device 138 to a control device 144 ( Fig. 8) transmitted. The received ultrasound signal 136, 236 is analyzed and evaluated, for example, by the control unit 144. The control unit 144 is configured, for example, to determine the respective signal propagation time based on the ultrasound signal 136, 236 with the several reflected signal components 136a, 136b or 236a to 236c. Taking into account the pre-determined position C, D of the corresponding marker 112, 212, a sound velocity V (Va to Vc in Fig. 8) for each volume element 130, 230 individually. Then, one or more parameters P of the substrate body 108, 208 are determined based on the determined speed of sound V (Va to Vc). Thus, one or more parameters P (Pa to Pc) of the substrate body 108, 208 can be determined for each volume element 130, 230 (i.e., 130a to 130b in Fig. 4 or 230a to 230c in Fig. 8) be determined separately. For illustrative purposes only, a coefficient of thermal expansion ρ is given as a parameter Pa to Pc for each volume element 230 in Fig. 8 determined. However, one or more other parameters of the substrate body 208 can also be determined in step S4 - in addition to or instead of the coefficient of thermal expansion ρ.

[0167] The optical system 100 and / or component 102 can, for example, also be used in a DUV lithography system.

[0168] Although the present invention has been described using exemplary embodiments, it can be modified in many ways. REFERENCE MARK LIST 1 Projection exposure system 2 Lighting system 3 light source 4 Lighting optics 5 object field 6 Object level 7 reticles 8 label holders 9 Reticle displacement drive 10 Projection optics 11 Image field 12 Image plane 13 wafers 14 wafer holders 15 wafer transfer drive 16 Lighting radiation 17 Collector 18 Intermediate focus plane 19 deflecting mirrors 20 first faceted mirror 21 first facet 22 second faceted mirror 23 second facet 100 optical system 102 components 104 Mirror substrate 106 area 108 substrate bodies 110 material 112 Mark 114 Inner 116 Engraving 118 Marking generating device 120 laser beam 122 Processing location 124 Change 126 Riss 128 area 130 volume element 130a, 130b Volume element 132 Interferometer 134 Ultrasound signal 136 Ultrasound signal 136a, 136b Signal component 138 Ultrasonic sensor device 140 Ultrasound microscope 142 Floor 144 Control unit 208 substrate bodies 212, 212' marker 212a-212c Marking 214 Inner 216 grid point 218 grids 230 volume element 230a-230c Volume element 234 Ultrasound signal 236 Ultrasound signal 236a-236c signal component 242 Floor α angle Δρ Variation coefficient of thermal expansion ΔZCT variation zero-crossing temperature λ wavelength ρ coefficient of thermal expansion A1 distance A2 distance B Offset Position C Ca- CC position D Position Size G M1-M6 mirrors P Parameter Pa-Pc Parameter r place S1-S4 Process step V Speed ​​of sound Va-Vc Speed ​​of sound ZCT zero-crossing temperature QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] DE 10 2008 009 600 A1 [0104, 0108] US 2006 / 0132747 A1

[0106] EP 1 614 008 B1

[0106] US 6,573,978

[0106] DE 10 2017 220 586 A1

[0111] US 2018 / 0074303 A1

[0125]

Claims

[1] Method for examining a substrate body (108) for a component (102) of a lithography system (1), comprising the steps: a) Generating (S1) at least one marking (112) in an interior (114) of the substrate body (108), b) Emitting (S3) an ultrasound signal (134) and receiving an ultrasound signal (136) reflected at the at least one mark (112), and c) Determine (S4), spatially resolved, one or more parameters (P) of the substrate body (108) based on the received ultrasound signal (136). [2] Method according to claim 1, wherein the at least one marking (112) has at least one engraving (116). [3] Method according to claim 1 or 2, wherein the at least one marking (112) is produced by laser engraving. [4] Method according to claim 3, wherein a predetermined laser wavelength (λ) is used in the laser engraving and the substrate body (108) is transparent to the predetermined laser wavelength (λ). [5] Method according to any one of claims 1 to 4, wherein a size (G) of the at least one marking (112) is 100 µm or less, 50 µm or less, 30 µm or less, 10 µm or less, 5 µm or less and / or 1 µm or less. [6] Method according to any one of claims 1 to 5, wherein inside (214) the substrate body (208) several of the markings (212, 212a-212c) are created, which divide the substrate body (208) into several volume elements (230, 230a-230c), the received reflected ultrasound signal (236) for each marker (212, 212a-212c) has a corresponding reflected signal component (236a-236c), and one or more parameters (P, Pa-Pc) for each volume element (230, 230a-230c) are determined based on the corresponding reflected signal component (236a-236c). [7] Method according to any one of claims 1 to 6, wherein several of the markings (212) are produced inside (214) the substrate body (208) which are arranged accordingly at or adjacent to lattice points (216) of a regular three-dimensional lattice (218). [8] Method according to any one of claims 1 to 7, wherein a position (C, D) of which at least one mark (112) is determined, and one or more parameters (P) of the substrate body (108) are determined based on the determined position (C, D), and the position (C) of the at least one marking (112) is determined based on operating parameters (α, λ) of a laser (118) when generating the at least one marking (112), and / or the position (D) of the at least one marking (112) is determined based on an optical measurement. [9] Method according to any one of claims 1 to 8, wherein a sound velocity (V) in the substrate body (108) is determined with spatial resolution based on the received ultrasound signal (136), and one or more parameters (P) of the substrate body (108) are determined based on the determined sound velocity (V). [10] Method according to any one of claims 1 to 9, wherein a material (110) of the substrate body comprises glass, high-performance glass, titanium-doped glass, silicon and / or plastic. [11] Method according to any one of claims 1 to 10, wherein one or more parameters (P) of the substrate body (108) have: one or more mechanical, thermal and / or acoustic parameters, and / or a coefficient of thermal expansion (ρ), a zero crossing temperature (ZCT), a modulus of elasticity, a shear modulus, a Poisson's ratio and / or an acoustic impedance. [12] Method according to any one of claims 1 to 11, wherein step b) is carried out using an ultrasonic microscope (140). [13] Method according to any one of claims 1 to 12, wherein the component (102) of the lithography system (1) is a mirror (M1-M6) of the lithography system (1), and the substrate body (108) is a body of a mirror substrate (104) of the mirror (M1-M6). [14] Substrate body (108) for a component (102) of a lithography system (1), comprising at least one marking (112) at at least one predetermined position (C) in an interior (114) of the substrate body (108), wherein the at least one marking (112) is configured to reflect an ultrasound signal (134). [15] Lithography system (1) comprising a component (102) comprising a substrate body (108) according to claim 14.

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