Method for detecting corrosion progress, method for operating an optical system and optical system

Abstract

The invention relates to a method for detecting corrosion progress (9) of a surface area (1a) to be examined of an additively manufactured component (1) of an optical arrangement (2), characterized by at least the following method steps: a) Selection of a sample (4) of the additively manufactured component (1), wherein the sample (4) has a surface area (4a) of the additively manufactured component (1) to be examined; b) Creating an initial characterization of the surface area (4a) by taking at least one image (5) of the surface area (4a) using an X-ray microscope; c) Introducing and leaving the sample (4) of the additively manufactured component (1) having the surface area (4a) in a selected corrosion medium (11); d) Creating a comparative characterization of the surface area (4a) by taking at least one further image (6) of the surface area (4a) using the X-ray microscope after the surface area (4a) has been left in the corrosion medium (11) for a defined period of time; and e) Evaluating the images (5, 6) of the initial characterization and the comparative characterization by means of a target-actual comparison (7), wherein the image (5) of the initial characterization represents the target state and the image (6) of the comparative characterization represents the actual state, and determining the corrosion progress (9).

Description

[0001] The present invention relates to a method for detecting corrosion progression of a surface of an additively manufactured component of an optical arrangement.

[0002] The present invention also relates to a method for operating an optical system, in particular a lithography system, preferably a projection exposure system.

[0003] The present invention further relates to an optical system, in particular a lithography system, preferably a projection exposure system.

[0004] Lithography, especially microlithography, is used to manufacture microstructured components such as integrated circuits or LCDs. The lithography process is carried out in a so-called projection exposure system, which comprises an illumination source, an illumination system, and a projection lens. The image of a mask (= reticle) illuminated by the illumination system is projected by the projection lens onto a substrate coated with a light-sensitive layer and arranged in the image plane of the projection lens in order to transfer the mask structure to the light-sensitive coating of the substrate.

[0005] The lithography systems known for this purpose are designed as EUV (extreme ultraviolet) or DUV (deep ultraviolet) projection exposure systems.

[0006] The optical elements used in lithography systems, especially projection exposure systems, serve to guide and shape radiation. Precise control of the surface shape is particularly advantageous for creating a precise wavefront with desired properties. The surface of the optical element can deviate from a desired shape, for example, if the energy introduced by the radiation leads to heating and thus distortion of the optical element.

[0007] It is known from the prior art to keep the optical element at a constant temperature, in particular to cool it.

[0008] For cooling optical elements that interact with radiation, heat sinks are known from the prior art. These heat sinks have at least one cooling channel for conducting a cooling medium. The cooling medium is in thermally conductive contact with the region of the optical element to be cooled, in particular an optical element bearing an optical surface, so that the heat sink can extract the energy introduced by the radiation from the optical element. This allows the optical element to be maintained at a constant temperature or brought to this temperature.

[0009] A generic method for detecting corrosion progression is known from DE 10 2019 216 301 A1.

[0010] DE 10 2019 216 301 A1 describes that it is particularly problematic that the EUV mirrors of EUV projection exposure systems experience heating and associated thermal expansion or deformation, particularly as a result of the absorption of the radiation emitted by the EUV source, which in turn can impair the imaging properties of the optical system.

[0011] According to DE 10 2019 216 301 A1, known approaches for dissipating heat loads from optical elements, in particular of a projection exposure system, include the use of heat sinks, in particular cooling channels, through which a cooling fluid such as water flows to dissipate heat and which are connected to an inlet and an outlet for the cooling fluid. In practice, however, the problem would arise that, depending on the structural design of these heat sinks (which can run, for example, on the back of the mirror or in a mechanical support structure), corrosion-related damage caused by the cooling fluid could occur within the cooling lines themselves and / or in the area of ​​flange connections, and could then lead to a reduction in the service life of the arrangement or assembly. In particular, when designing the arrangement or assembly,In an assembly consisting of separate components, the cooling fluid can overflow a gap between these components and cause corrosion-related leaks in the area of ​​the flange connections. In the case of corrosion-related leaks, coolant ingress into the respective optical system can result in serious damage.

[0012] DE 10 2019 216 301 A1 states that avoiding the corrosion-related problems described above is difficult in practice because, for example, the performance of ultrasonic measurements for corrosion detection in an EUV projection exposure system is ruled out due to the risk of layer detachment on the optical elements.

[0013] Special challenges arise when detecting corrosion progression on additively manufactured components. Determining the corrosion progression on the surface of additively manufactured components is difficult due to the layered structure and the typical roughness of the surface. The surface of the additively manufactured component may already be damaged due to the manufacturing process, particularly with defects in the form of channel-like holes that may have dimensions in the micrometer range. Determining system-dependent corrosion progression on such irregular surfaces of additively manufactured components, even when they have been post-processed, has proven particularly difficult in practice. Conventional methods for determining corrosion are not applicable because the defects on the surface are not evenly distributed and of the same depth. Defect measurement in a ground section, e.g.A flow test is not useful because it is unclear how extensive the initial damage to the surface of the additively manufactured component already was. The main question is whether the defects were already present initially, whether the depth of the defects has increased due to corrosion, or whether the entire defect occurred due to corrosion without any prior damage.

[0014] There are no known methods from the state of the art to non-destructively observe the corrosion progression of additively manufactured components and its temporal progression.

[0015] The known, standardized methods for determining corrosion progression or corrosion rate are either destructive (metallography to measure defect depth in a micrograph, electrochemical testing by applying voltage to the sample) or have high resolution limits, such as the method for determining mass loss or the determination of dissolved ions in the electrolyte. Furthermore, a macroscopic / microscopic examination of the surface is often performed. However, both electrochemical testing and macroscopic / microscopic examination can only provide a qualitative statement regarding corrosion (or its tendency to corrosion).

[0016] A further disadvantage of defect measurement in the ground section, in addition to the fact that the sample is destroyed and thus can only be analyzed at a specific time, is the fact that only very small sample sizes can be analyzed. Due to these disadvantages, statistical reliability can only be achieved by massively increasing the number of samples.

[0017] The present invention is based on the object of providing an advantageous method for detecting corrosion progression of a surface of an additively manufactured component of an optical arrangement.

[0018] This object is achieved according to the invention by the features of claim 1.

[0019] The present invention is further based on the object of providing a method for operating an optical system, in particular a lithography system, which makes it possible to take countermeasures in good time to prevent damage to the optical system by a cooling fluid escaping due to corrosion.

[0020] This object is achieved according to the invention by claim 13.

[0021] The present invention is also based on the object of providing an optical system, in particular a lithography system, in which damage caused by a cooling fluid escaping due to corrosion is largely avoided.

[0022] This object is achieved according to the invention by claim 15.

[0023] The method according to the invention for detecting corrosion progression of a surface of an additively manufactured component of an optical arrangement provides at least the following method steps: a) selecting a sample of the additively manufactured component, the sample comprising a surface area of ​​the additively manufactured component to be examined; b) creating an initial characterisation of the surface area by taking at least one image of the surface area using an X-ray microscope; c) introducing and leaving the sample of the additively manufactured component containing the surface area in a selected corrosion medium; d) creating a comparative characterisation of the surface area by taking at least one further image of the surface area using the X-ray microscope after the surface area has been left in the corrosion medium for a defined period of time; and e) Evaluating the images of the initial characterization and the comparative characterization by means of a target-actual comparison, whereby the image of the initial characterization represents the target condition and the image of the comparative characterization represents the actual condition, and determining the corrosion progress.

[0024] The method according to the invention enables the non-destructive determination of corrosion progression on additively manufactured surfaces, allowing the temporal change of the corrosion attack(s) to be observed. Due to the initial characterization, the method according to the invention can also be applied to previously damaged surfaces.

[0025] The method according to the invention enables non-destructive recording of the surface morphology for initial characterization or initial characterization of the sample. The initial characterization preferably takes place before exposure to the environment or before the sample of the additively manufactured component exhibiting the surface area is placed in a selected corrosion medium. However, the recording or initial characterization of the surface area (according to process step b)) can also take place after immersion or the introduction of the sample into the selected corrosion medium (according to process step c)), especially if this takes place relatively soon after immersion.

[0026] Process steps b) and c) therefore do not have to be carried out one after the other, but it can be provided in particular that process step b) is only carried out after the sample has been introduced into the selected corrosion medium.

[0027] In one embodiment of the invention, it can be provided that process step b) and / or process step d) takes place in situ, while the sample with the surface area to be examined is in the corrosion medium.

[0028] This means that both the X-ray microscope image for initial characterization and the X-ray microscope image for comparative characterization can be taken while the sample or the surface area to be examined is immersed in the selected corrosion medium. Taking the images in situ is particularly suitable if the vessel is sufficiently sealed. Regarding the initial characterization, it can be advantageous if only a few hours elapse between the sample being placed in the selected corrosion medium and the start of the measurement.

[0029] The method according to the invention provides that the sample or the surface area to be examined remains in the selected corrosion medium for a defined period of time. The corrosion medium can preferably be an electrolyte. The corrosion medium can, in particular, be a medium that can lead to corrosion in the additively manufactured component during its intended operation. The corrosion medium can, in particular, be a fluid, especially water.

[0030] The sample is preferably a suitable part of the additively manufactured component or the material from which the additively manufactured component is made. However, the sample can also be the entire additively manufactured component.

[0031] According to the invention, after the surface area has been left in the corrosion medium for a defined period of time, at least one further image of the surface area to be examined is taken using the X-ray microscope. By evaluating the images from the initial characterization and the comparative characterization using a target-actual comparison, for example, a visual comparison of the morphologies and a quantification of the removal / material loss due to corrosion, the corrosion progress can be determined and preferably visually displayed. The target-actual comparison is preferably performed using software; preferably, evaluation software associated with X-ray microscopy, in particular Visual Graphics, is used for this purpose.

[0032] The X-ray microscope used is preferably a high-resolution X-ray microscope, preferably an Xradia Versa X-ray microscope from Carl Zeiss Microscopy Deutschland GmbH.

[0033] Depending on the desired resolution, which largely depends on the expected corrosion attack, as well as the material used and its density, a "normal" CT may also be sufficient for creating the images. However, this is not preferred within the scope of the invention. The X-ray microscope used is preferably a high-resolution X-ray microscope.

[0034] It should be noted that, depending on the size of the additively manufactured component and the material used or the density, a flow test may also be performed instead of an immersion test. In the flow test, the cooling medium, for example, water, can be pumped through the sample or the additively manufactured component. However, this is preferably not provided for within the scope of the invention and is mentioned here only for the sake of completeness.

[0035] It is advantageous if the process steps c) to e) are carried out iteratively, whereby the target-actual comparison is preferably carried out based on a comparison of the recording of the initial characterization and the recording of the most recently created comparison characterization.

[0036] The iterative implementation of the process steps improves the data availability and thus enables an even better assessment of the corrosion progression and the determination of the corrosion mechanisms. Preferably, the target-actual comparison is performed based on a comparison of the initial characterization recording and the most recently created comparative characterization. In principle, however, it would also be possible to create a target-actual comparison based on the recording of one of the previous comparative characterizations, preferably the penultimate comparative characterization, which in this case represents the initial characterization, and the most recently created comparative characterization.

[0037] It is advantageous if the recordings of the initial characterization and the comparative characterization and / or the data of the target-actual comparison are statistically evaluated to generate a model for predicting the corrosion progression and / or the failure probability of the component and / or for determining the lifetime of the component.

[0038] It has proven particularly advantageous to statistically evaluate the obtained data and thus create so-called lifetime models or to use the data to predict the corrosion progression and / or the selection probability of the component. The method according to the invention can thus make an important contribution to corrosion risk assessment. Based on the data, it is possible to determine the corrosion mechanism and, particularly in the case of pitting corrosion, which occurs statistically and can therefore hardly or not at all be simulated, to determine the progression and, if applicable, the stable pitting growth.

[0039] According to the invention, it can further be provided that a CT overview scan is carried out of the sample by means of a CT scanner which has a lower resolution than the X-ray microscope, and the CT overview scan is used to locate the surface area to be examined before the image of the comparison characterization is created in the X-ray microscope.

[0040] It has proven advantageous to perform a CT overview scan, particularly before performing process step b). The CT overview scan can be performed in advance at a lower resolution in order to "re-locate" the exact positioning of the point or surface area to be observed in the high-resolution X-ray microscope. Accordingly, a CT overview scan can then be performed again before the image is taken using the X-ray microscope, particularly in connection with process step d), in order to re-locate the point or surface area to be examined, as described above.

[0041] It is advantageous if the sample is marked and the marking is used for identical clamping in the X-ray microscope and / or the CT scanner.

[0042] The marking can be done, for example, by scratching or by marking with a liquid-resistant or waterproof pen. This marking simplifies overlaying the images.

[0043] Within the scope of the method, it may be provided that sample areas not to be tested, such as cut edges, are masked. Within the scope of the method according to the invention, further process steps can be carried out analogously to other corrosion tests, for example, regarding cleaning and ensuring compliance with the selected conditions.

[0044] The contacting or fixing of the sample in the corrosion medium can generally be carried out using known devices or measures.

[0045] It has been found to be particularly advantageous in the context of the process according to the invention if, during process step c), the corrosion medium is set in motion, preferably by means of a stirring body arranged in the corrosion medium.

[0046] The stirring body can preferably be a so-called stirring fish.

[0047] It is advantageous if the surface area is facing the stirring body, ie that the surface area is arranged accordingly in the corrosion medium.

[0048] It may be advantageous if the corrosion medium is tempered and / or irradiated with UV radiation during process step c).

[0049] UV irradiation can prevent biocorrosion, potentially preventing the overlap of various corrosion mechanisms. A UV lamp can be used to irradiate the corrosion medium into which the sample is placed and left.

[0050] By controlling the temperature of the corrosion medium into which the sample is placed and left, realistic test conditions can be created.

[0051] Depending on the operating conditions, it may be advantageous to close or cover a container containing the corrosion medium into which the sample is introduced and left in process step c) with a cover, particularly a lid. This lid prevents the corrosion medium from evaporating, particularly when the corrosion medium is temperature-controlled. Covering the container with a lid may depend on the operating conditions.

[0052] It is advantageous if several samples with surface areas to be examined are left in the corrosion medium at the same time.

[0053] It is also advantageous if the scanning time for creating the image of the initial characterization and / or the image of the comparative characterization is 2 hours to 16 hours, preferably 8 hours to 12 hours, and / or the voxel size is 1 µm to 8 µm, preferably 1 µm to 5 µm, in particular 1 µm to 3 µm, preferably 2 µm.

[0054] It is advantageous if the size of the sample to be examined is at most 30 cm x 30 cm, preferably at most 10 cm x 10 cm, more preferably at most 3 cm x 3 cm and / or preferably at least 0.1 cm x 0.1 cm.

[0055] Within the scope of the method according to the invention, it is preferably provided that the additively manufactured component is made of a material with good thermal conductivity, in particular steel, stainless steel, titanium, aluminum or copper.

[0056] The achievable resolution depends on the material used and its density. The lighter or lower the density, the better the translucency and thus the resolution.

[0057] It is advantageous if the additively manufactured component is a heat sink, in particular a heat sink for an optical element, preferably for an optical element of a lithography system, in particular an EUV or DUV projection exposure system, particularly preferably for a mirror or a mirror arrangement with a plurality of mirror elements of an EUV projection exposure system.

[0058] The method according to the invention is particularly suitable for use in a heat sink for an optical element of an EUV projection exposure system, in particular for a mirror or a mirror arrangement.

[0059] In the context of the present invention, a combination of a heat sink and an optical element is also referred to as an optical arrangement. The optical element of the optical arrangement can preferably be an optical element of a lithography system, in particular an EUV or DUV projection exposure system. The optical element can in particular be a mirror or a mirror arrangement of an EUV projection exposure system. The heat sink serves to cool the optical element and is preferably flowed through by a cooling medium during operation of an optical system, in particular a lithography system, to cool the optical element.

[0060] The present invention also discloses a method for operating an optical system, in particular a lithography system, preferably a projection exposure system, wherein the optical system comprises an optical arrangement with at least one optical element and at least one heat sink produced by additive manufacturing through which a cooling medium can flow for cooling this optical element during operation of the optical system, wherein the method comprises the following steps: i) estimating a corrosion progression and / or the failure probability and / or the lifetime of the heat sink using a method according to any one of claims 1 to 12, wherein the additively manufactured component according to claims 1 to 12 is the heat sink; and ii) implementing a countermeasure to prevent damage to the optical system caused by cooling medium escaping from the heat sink due to corrosion in response to the assessment according to step i).

[0061] The method according to the invention for operating an optical system makes it possible to initiate a countermeasure in good time so that damage to the optical system is avoided based on an assessment after method step i).

[0062] Within the scope of the method according to the invention for operating an optical system, it can be provided that the implementation of the countermeasure comprises at least one of the following steps: - Replacing a component and / or the optical assembly and / or the heat sink of the optical system; - Sealing the heat sink; and / or - Setting or interrupting cooling operation of the optical system.

[0063] The present invention also relates to an optical system, in particular a lithography system, preferably a projection exposure system with at least one optical arrangement comprising an optical element and a heat sink, wherein a cooling medium for cooling the optical element can flow through the heat sink during operation of the optical system. It is provided that a corrosion progression and / or the failure probability and / or the service life of the heat sink is determined using the method according to the invention for detecting corrosion progression, wherein the additively manufactured component is the heat sink.

[0064] Such an optical system has proven particularly suitable for reducing or preventing damage caused by cooling medium escaping from the heat sink due to corrosion. The optical system can also be operated, in particular, according to the method according to claims 13 and 14.

[0065] Features described in connection with one of the subject matters of the invention, specifically the inventive method for detecting corrosion progression, the inventive method for operating an optical system, or the inventive optical system, can also be advantageously implemented for the other subject matters of the invention. Likewise, advantages mentioned in connection with one of the subject matters of the invention can also be understood to relate to the other subject matters of the invention.

[0066] In the following, embodiments of the invention are described in more detail with reference to the drawing.

[0067] The figures each show preferred embodiments in which individual features of the present invention are illustrated in combination with one another. Features of one embodiment can also be implemented independently of the other features of the same embodiment and can therefore be readily combined by a person skilled in the art to form further useful combinations and subcombinations with features of other embodiments.

[0068] In the figures, functionally identical elements are provided with the same reference numerals.

[0069] They show: Fig. 1 a schematic representation of an image showing an initial characterization of a surface area to be examined; Fig. 2 a schematic representation of an image showing a comparative characterization of the surface area to be examined after the surface area has been left in a corrosion medium for a defined period of time; Fig. 3 a target-actual comparison of the recordings according to the Fig. 1 and Fig. 2 with a representation of the change; Fig. 4 an exemplary representation of an experimental setup for immersion according to process step c); Fig. 5 a flow diagram for detecting corrosion progress of a surface area to be examined of an additively manufactured component, in particular a heat sink; Fig. 6 a schematic representation of an optical arrangement comprising an optical element and a heat sink, wherein the heat sink is an additively manufactured component; and Fig. 7 a highly simplified representation of an EUV projection exposure system.

[0070] The Fig. 1 to 5 show, by way of example, a method or method steps for detecting a corrosion progression of a surface 1a of an additively manufactured component 1 of an example in Fig. 6. The optical arrangement 2 can preferably be part of an exemplary Fig. 7. In the exemplary embodiment, the optical arrangement 2 comprises, in addition to the additively manufactured component 1, an optical element 3, which in the exemplary embodiment is preferably a mirror or a mirror arrangement with a plurality of mirror elements.

[0071] In the exemplary embodiment, the additively manufactured component 1 is a heat sink which serves to cool the optical element 3.

[0072] The additively manufactured component 1 is also referred to as heat sink 1 in the exemplary embodiment.

[0073] The surface 1a of the additively manufactured heat sink 1, the corrosion progression of which is to be detected, is in the embodiment (see Fig. 6) a surface 1a of a cooling channel 12 of the heat sink 1. The surface 1a of the cooling channel 12 of the heat sink 1 is subject to corrosion if, as provided in the exemplary embodiment, the cooling channel 12 is flowed through by a cooling medium for cooling the optical element 3 during operation of the optical system 100.

[0074] The method shown in the exemplary embodiment for detecting corrosion progress 9 of the surface 1a of the heat sink 1 of the optical arrangement 2 provides the following method steps.

[0075] To illustrate the procedural steps, please also refer to the Fig. 5.

[0076] In method step a), a sample 4 of the heat sink 1 is selected, wherein the sample 4 has a surface area 4a of the heat sink 1 to be examined.

[0077] In a method step b), an initial characterization of the surface region 4a is created by taking at least one image 5 of the surface region 4a using an X-ray microscope.

[0078] In a process step c), the sample 4 of the heat sink 1 is immersioned, ie the sample 4 is introduced into a selected corrosion medium 11 and left there.

[0079] In a method step d), a comparative characterization of the surface region 4a is created by taking at least one further image 6 of the surface region 4a using the X-ray microscope after the surface region 4a has been left in the corrosion medium 11 for a defined period of time.

[0080] In process step e), images 5 and 6 of the initial characterization and the comparative characterization are evaluated using a target-actual comparison 7, with image 5 of the initial characterization representing the target state and image 6 of the comparative characterization representing the actual state. From this, the corrosion progression 9 is then determined, also as part of process step e).

[0081] The Fig. 1 shows an exemplary image 5 of the initial characterization.

[0082] The Fig. Figure 2 shows an exemplary image 6 of the comparative characterization.

[0083] The Fig. 3 shows the target-actual comparison 7 of image 5 of the initial characterization and image 6 of the comparative characterization.

[0084] Again Fig. 1, the surface area 4a has various defects 8, for example in the form of channel-like holes. Fig. 1 one of the defects is designated by the reference numeral 8. In Fig. 1 shows the material of sample 4 of the heat sink 1 in dashed lines. The non-dashed areas represent Fig. 1 air or the defects.

[0085] The Fig. Figure 2 shows image 6 of surface area 4a, which was created using the same X-ray microscope according to process step d). It can be seen that the defect 8, which was already visible in image 5 according to Fig. 1, has since increased in size due to corrosion. The other defects are, compared to the representation in the Fig. 1, in Fig. 2 (exemplary) remained unchanged, ie these defects have not changed due to corrosion in the example.

[0086] To illustrate the corrosion progress, the target-actual comparison 7, which is shown in Fig. 3, the corrosion progress is highlighted in dotted lines and provided with the reference number 9.

[0087] The representation according to Fig. 3 results from comparing or superimposing images 5 and 6.

[0088] With the dashed line in Fig. 5 is intended to symbolize that the process steps c) to e) can be carried out iteratively, whereby the target-actual comparison in the exemplary embodiment is carried out based on a comparison of the recording 5 of the initial characterization and the recording 6 of the last created comparison characterization.

[0089] In a process step f), which is Fig. 5 is also shown, the images 5, 6 of the initial characterization and the comparative characterization and / or the data of the target-actual comparison 7 can be statistically evaluated to generate a model for predicting the corrosion progression 9 and / or the failure probability of the heat sink 1 and / or for determining the service life of the heat sink 1.

[0090] In the exemplary embodiment, a CT overview scan of the sample 4 can be performed using a CT scanner that has a lower resolution than the X-ray microscope. The CT overview scan can be used to locate the surface area 4a to be examined before the comparative characterization image 6 is created in the X-ray microscope. A CT overview scan can preferably be performed within the scope of method steps b) or d), preferably before these method steps are performed.

[0091] In the exemplary embodiment, it can be provided that the sample is marked and the marking is used for identical clamping in the X-ray microscope and / or the CT scanner.

[0092] In the exemplary embodiment, it can be provided that during method step c) the corrosion medium 11 is set in motion, preferably by a stirring body 10 arranged in the corrosion medium 11. The surface area 4a preferably faces the stirring body 10. The stirring body 10 can preferably be a stirrer. In the exemplary embodiment, it can optionally be provided that several samples 4 with surface areas 4a to be examined are left simultaneously in the corrosion medium 11. In this regard and also with regard to the stirring body 10, reference is made to the exemplary representation in Fig. 4.

[0093] It may be provided that a voltage is applied to accelerate the corrosion in process step c), but this is not preferable for realistic results.

[0094] In the exemplary embodiment, during process step c), the corrosion medium 11 may be irradiated with UV radiation. The UV radiation can be generated using a UV lamp (not shown in the exemplary embodiment) to prevent biocorrosion.

[0095] In the exemplary embodiment, in method step c) it can further be provided that the corrosion medium 11 is tempered in order to create realistic test conditions.

[0096] In the exemplary embodiment, it can also be provided that a Fig. 4 unspecified container in which the corrosion medium 11 is introduced, is covered or closed with a lid (not shown) in order to prevent the evaporation of the corrosion medium 11, in particular when it is tempered.

[0097] Process step b) and / or process step d) can be carried out in situ, while the sample 4 with the surface area 4a to be examined is in the corrosion medium 11. The representation in Fig. 5 is to be understood accordingly.

[0098] In the exemplary embodiment, it is provided that the scanning time for creating the image 5 of the initial characterization and / or the image 6 of the comparative characterization is 2 hours to 16 hours, preferably 8 hours to 12 hours, and / or the voxel size is 1 µm to 8 µm, preferably 1 µm to 5 µm, in particular 1 µm to 3 µm, preferably 2 µm.

[0099] In the exemplary embodiment, the heat sink 1 is made of a material with good thermal conductivity, particularly steel, stainless steel, titanium, aluminum, or copper. In principle, it can also be made of plastic, but this is not preferred for the implementation of the method.

[0100] In the exemplary embodiment, the heat sink 1 is in particular a heat sink for an optical element 3, preferably for an optical element 3 of a lithography system, as is illustrated by way of example with reference to the optical system 100.

[0101] The exemplary embodiment is also intended to disclose a method for operating an optical system 100, in particular a lithography system, preferably a projection exposure system. As already described above, the optical system 100 comprises an optical arrangement 2 with at least one optical element 3 and at least one heat sink 1, manufactured by additive manufacturing, through which a cooling medium can flow to cool this optical element 3 during operation of the optical system 100.

[0102] The method according to the invention for operating the optical system 100 comprises the following steps: i) estimating a corrosion progression 9 and / or the failure probability and / or the lifetime of the heat sink 1 using the method according to the invention for detecting the corrosion progression 9, and ii) Carrying out a countermeasure to prevent damage to the optical system 100 by cooling medium escaping from the heat sink 1 due to corrosion in response to the estimation according to method step i).

[0103] In the exemplary embodiment, the implementation of the countermeasure preferably involves the following steps: - Replacing a component and / or the optical arrangement 2 and / or the heat sink 1 of the optical system 100; - Sealing the heat sink 1; and / or - Setting or interrupting a cooling operation of the optical system 100.

[0104] The exemplary embodiment also serves to disclose an advantageous optical system 100, in particular a lithography system, preferably a projection exposure system with the optical arrangement 2 already described, comprising an optical element 3 and a heat sink 1, wherein a cooling medium for cooling the optical element 3 can flow through the heat sink 1 during operation of the optical system 100. It is provided that a corrosion progression 9 and / or the selection probability and / or the lifetime of the heat sink 1 is or will be determined using the method according to the invention.

[0105] The Fig. 7 shows, in a purely schematic representation, an example of an optical system 100, in particular a lithography system, based on an illustration of an EUV projection exposure system 100 operated with working light in the wavelength spectrum of extreme ultraviolet light (EUV radiation). The projection exposure system 100 has an illumination source 101, an illumination system 102, and a projection lens 103, with the aid of which the structures provided on a reticle 104 are imaged in a reduced manner onto a wafer 105 in order to generate micro- or nanostructures there via microlithographic processes. Elements of the EUV projection exposure system 100, such as mirrors, can become considerably heated by the EUV radiation, necessitating cooling. For this purpose, heat sinks 1, such as those described above, can be used.

[0106] A particularly advantageous EUV projection exposure system 100 and also a DUV projection exposure system is shown and described in WO 2022 / 248369 A1, in which particular reference is made to the explanations on the Fig. 1 and Fig. 2 is referred to. List of reference symbols 1 heat sink 1a surface 2 optical arrangement 3 optical element, mirror 4 Sample 4a Surface area 5 Recording of the initial characterization 6 Recording of the comparative characterization 7 Target-actual comparison 8 defects 9 Corrosion progress 10 stirring bodies, stirring fish 11 Corrosion medium 12 cooling channel 100 optical system, EUV projection exposure system 101 Lighting source 102 Lighting system 103 Projection lens 104 reticles 105 wafers QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2019 216 301 A1 [0009, 0010, 0011, 0012] WO 2022 / 248369 A1

[0106]

Claims

[1] Method for detecting corrosion progress (9) of a surface (1a) of an additively manufactured component (1) of an optical arrangement (2), characterized by at least the following procedural steps: a) selecting a sample (4) of the additively manufactured component (1), wherein the sample (4) has a surface area (4a) of the additively manufactured component (1) to be examined; b) creating an initial characterization of the surface area (4a) by taking at least one image (5) of the surface area (4a) using an X-ray microscope; c) introducing and leaving the sample (4) of the additively manufactured component (1) having the surface area (4a) in a selected corrosion medium (11); d) creating a comparative characterization of the surface area (4a) by taking at least one further image (6) of the surface area (4a) using the X-ray microscope after the surface area (4a) has been left in the corrosion medium (11) for a defined period of time; and e) evaluating the images (5, 6) of the initial characterization and the comparative characterization by means of a target-actual comparison (7), wherein the image (5) of the initial characterization represents the target state and the image (6) of the comparative characterization represents the actual state, and determining the corrosion progress (9). [2] Method according to claim 1, characterized by that the method steps c) to e) are carried out iteratively, wherein the target-actual comparison (7) is preferably carried out in each case based on a comparison of the recording (5) of the initial characterization and the recording (6) of the last created comparison characterization. [3] Method according to claim 1 or 2, characterized by that the recordings (5, 6) of the initial characterization and the comparative characterization and / or the data of the target-actual comparison (7) are statistically evaluated to generate a model for predicting the corrosion progression (9) and / or the failure probability of the component (1) and / or for determining the service life of the component (1). [4] Method according to claim 1, 2 or 3, characterized by that a CT overview scan of the sample (4) is carried out by means of a CT scanner which has a lower resolution than the X-ray microscope, and the CT overview scan is used to find the surface area (4a) to be examined before the image (6) of the comparative characterization is taken in the X-ray microscope. [5] Method according to one of claims 1 to 4, characterized bythat the sample (4) is marked and the marking is used for identical clamping in the X-ray microscope and / or the CT scanner. [6] Method according to one of claims 1 to 5, characterized by that during process step c) the corrosion medium (11) is set in motion, preferably by a stirring body (10) arranged in the corrosion medium (11). [7] Method according to one of claims 1 to 6, characterized by that during process step c) the corrosion medium (11) is tempered and / or irradiated with UV radiation. [8] Method according to one of claims 1 to 7, characterized by that several samples (4) with surface areas (4a) to be examined are left in the corrosion medium (11) at the same time. [9] Method according to one of claims 1 to 8, characterized bythat the process step b) and / or the process step d) takes place in situ, while the sample (4) with the surface area (4a) to be examined is in the corrosion medium (11). [10] Method according to one of claims 1 to 9, characterized by that the scanning time for creating the image (5) of the initial characterization and / or the image (6) of the comparative characterization is 2 hours to 16 hours, preferably 8 hours to 12 hours, and / or the voxel size is 1 µm to 8 µm, preferably 1 µm to 5 µm, in particular 1 µm to 3 µm, preferably 2 µm. [11] Method according to one of claims 1 to 10, characterized by that the additively manufactured component (1) is made of a material with good thermal conductivity, in particular steel, stainless steel, titanium, aluminum or copper. [12] Method according to one of claims 1 to 11, characterized bythat the additively manufactured component (1) is a heat sink, in particular a heat sink for an optical element (3), preferably for an optical element of an optical system 100, in particular a lithography system, preferably an EUV or DUV projection exposure system, particularly preferably for a mirror or a mirror arrangement with a plurality of mirror elements of an EUV projection exposure system. [13] Method for operating an optical system (100), in particular a lithography system, preferably a projection exposure system, wherein the optical system (100) comprises an optical arrangement (2) with at least one optical element (3) and at least one heat sink (1) produced by additive manufacturing through which a cooling medium can flow for cooling this optical element (3) during operation of the optical system (100), the method comprising the following steps: i) estimating a corrosion progression (9) and / or the failure probability and / or the lifetime of the heat sink (1) using a method according to one of claims 1 to 12, wherein the additively manufactured component (1) according to claims 1 to 12 is the heat sink (1); and ii) carrying out a countermeasure to prevent damage to the optical system (100) by cooling medium escaping from the heat sink (1) due to corrosion in response to the estimation according to method step i). [14] Method according to claim 13, characterized by that carrying out the countermeasure comprises at least one of the following steps: - replacing a component and / or the optical arrangement (2) and / or the heat sink (1) of the optical system (100); - Sealing the heat sink (1); and / or - Setting or interrupting a cooling operation of the optical system (100). [15] Optical system (100), in particular a lithography system, preferably a projection exposure system, with at least one optical arrangement (2) comprising an optical element (3) and a heat sink (1), wherein a cooling medium for cooling the optical element (3) can flow through the heat sink (1) during operation of the optical system (100), characterized by that a corrosion progression (9) and / or the failure probability and / or the service life of the heat sink (1) is determined using a method according to one of claims 1 to 12, wherein the additively manufactured component (1) according to claims 1 to 12 is the heat sink (1).

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