Method for manufacturing an optical component, optical component and system of semiconductor technology

Abstract

The invention relates to a method for manufacturing an optical component, preferably a mirror, in particular an EUV mirror (Mi), comprising: providing at least two sub-bodies (25, 26), preferably made of a glass material, and joining the at least two sub-bodies (25, 26) to form the optical component by creating at least one joining surface (29), preferably by high-temperature bonding. In the method, the optical component is reshaped, in particular curved, during high-temperature bonding. The invention also relates to an optical component, preferably a mirror (Mi), manufactured by the method, and to a semiconductor technology system comprising at least one such optical component.

Description

Background of the invention

[0001] The invention relates to a method for manufacturing an optical component, preferably a mirror, in particular an EUV mirror, comprising: providing at least two sub-bodies, preferably made of at least one glass material, and joining the at least two sub-bodies to form the optical component by creating at least one joining surface, preferably by high-temperature bonding. The invention also relates to an optical component manufactured by the method and to a semiconductor technology system comprising at least one such optical component.

[0002] Optical components, particularly mirrors in a projection system, located within an EUV lithography system, are exposed to high radiation power during operation. This heating of the mirror, or more precisely, the mirror substrate, which together with a reflective coating forms the mirror, leads to heating of the mirror substrate. The reflective coating is applied to an optically effective surface of the mirror substrate. Heating of the mirror substrate causes deformation of the optically effective surface and can impair the image quality of the projection system. To address this problem, substrates made of glass materials with a low coefficient of thermal expansion, such as titanium-doped fused silica, are typically used.

[0003] The two components can be made of the same glass material or of two or more different glass materials. The same glass material means that the glass material of both components has practically identical properties, for example, because both components were cut from the same glass blank. Different glass materials are present, for example, if the glass material of the two components has practically different properties, or if the two components are made of different types of glass.

[0004] To reduce the temperature of mirrors, it is known to incorporate cooling channels into the mirror substrate, through which a cooling fluid flows. Manufacturing these cooling channels requires creating passageways in the substrate with a geometry that depends on the specific mirror. During the processing of the substrate to create the cooling channels, stresses can occur in the glass material, leading to unexpected deformations. Mechanical stresses, caused, for example, by the mounting or storage of the optical component, its operation, or by attachments mounted to the substrate, can also lead to material stresses, depending on the direction of the mechanical stress. These stresses can affect the optically effective surface or a portion thereof.

[0005] Furthermore, in the production of a mirror, the smallest possible structures and gradients that can be produced on the optically effective surface are limited, among other things, by the tool size of the sub-aperture processes. Therefore, local structures, such as local protrusions or the like, whose extent is smaller than the sub-aperture cannot usually be formed on the optically effective surface.

[0006] In high-temperature bonding, also known as direct bonding, two or more components, usually made primarily of the same glass material or of different glass materials, are typically heated to a temperature above the glass transition temperature of the glass material. The glass transition temperature is material-dependent and is typically around 1000°C or higher. When the glass transition temperature is exceeded, the glass enters a viscous state. This allows the respective surfaces of the components to melt, forming covalent bonds that cause two adjacent components to permanently join at their respective interfaces without the use of an adhesive. Exceeding the glass transition temperature also effectively erases the glass material's history.The term "quenching" refers, for example, to properties of the glass material such as the zero-crossing temperature and the applied mechanical stresses. The glass transition temperature should be distinguished from the melting temperature of the glass material, which is higher and can range, for example, between approximately 1300°C and 1500°C. Even components not made of glass, such as semiconductor materials like silicon, can be joined together by forming at least one interface. The joined components can be made of the same material, or they can be made of different materials.

[0007] The joining surface formed when two components are joined to create an optical element in the form of a mirror can be flat or curved. The latter allows cooling channels to be incorporated into the mirror in the area of ​​the joining surface, maintaining a constant distance from the curved optical surface of the mirror, as described, for example, in WO2022 / 214290A1. In particular, the contact or joining surface can have a curvature that essentially matches the curvature of the optically effective surface of the mirror.

[0008] WO2020 / 207741A1 describes a method for manufacturing a glass body with at least one cooling channel, comprising: providing a first subbody and a second subbody, and manufacturing the glass body by joining the first subbody to the second subbody by high-temperature bonding, embedding at least one placeholder made of a temperature-resistant material between the two subbodies. The placeholder can be tubular and remain in the cooling channel after the glass body has been manufactured. Alternatively, the placeholder can be removed from the glass body after its manufacture to form the cooling channel. Object of the invention

[0009] The object of the invention is to provide a method for manufacturing an optical component, an optical component and a semiconductor technology system in which the optical component is modified when joining the sub-bodies, in particular in which mechanical stresses can be dampened and / or an optical effect can be changed. Subject matter of the invention

[0010] This task is solved, according to one aspect, by a process of the type mentioned above, in which the optical component is reshaped, in particular curved, during high-temperature bonding. "Reshaping" is generally understood to mean a controlled change in shape, as opposed to deformation, which is an uncontrolled plastic change in shape. The reshaping can, in particular, involve the controlled curvature of the optical component or a surface of the optical component.

[0011] During high-temperature bonding or annealing above the glass transition temperature, the optical component becomes viscous and deformable. This "flowing" of the optical component can be used for targeted shape modification in the viscous state, whereby, for example, a cuboid-shaped optical component can be transformed into a differently shaped optical component, such as a concave or convex one, before high-temperature bonding. The additional degree of freedom that arises when heating the sub-bodies or the optical component to temperatures above the glass transition temperature is specifically utilized in this aspect of the invention to bring the optical component into a desired shape.

[0012] When the optical component cools after exceeding its glass transition temperature, temperature gradients develop within it. Depending on the prevailing temperature conditions and the temperature of the furnace used for tempering, tensile and compressive forces act upon it. Measurements have shown that these tensile and compressive forces, even after the optical component has cooled to room temperature, can lead to permanent deformation, particularly warping, resulting in concave and convex sides. However, the deformation caused by cooling is significantly less than the deformation achievable in the viscous state. Nevertheless, a controlled deformation of the optical component can be achieved through a suitable temperature profile during cooling.If necessary, it is also possible to take into account the expected deformation of the optical component during cooling, in which a flat surface of the optical component before high-temperature bonding becomes a surface with a PV value of 100 µm or less after high-temperature bonding, when forming the optical component in a viscous state above the glass transition temperature.

[0013] In one variant, the component parts are placed on a shaped surface, preferably concave or convex, and the optical component is lowered onto the shaped surface during high-temperature bonding – in a viscous or semi-viscous state. In this case, the shaping of the optical component typically occurs through gravity lowering; that is, the component's own weight causes it to lower onto the shaped surface, with the underside of the lowest component part assuming the geometry of the shaped surface. The shaped surface can have, for example, a spherical concave or convex curvature, but it is also possible for the shaped surface to be a freeform surface.In the event that the optically effective surface is an aspherical surface, a shaped surface, which is also an aspherical surface, should be used for the high-temperature flooring.

[0014] The shaped surface can be the surface of a base onto which the components are placed before being inserted into the tempering oven. Alternatively, the shaped surface can be the base of a mold with side walls that prevent the optical component or components from slipping or tipping. The base or mold is made of a heat-resistant material, such as fireclay.

[0015] In a further development, the formed surface has a geometry that corresponds to the geometry of an optically effective surface of the optical component. In the case of an optical component in the form of a mirror, the optically effective surface is the surface onto which a reflective coating is applied. By lowering the component under gravity, an outer surface can be selectively reshaped into the underside of the lowest sub-body and adapted to the geometry of the formed surface of the base or the bottom of the mold.

[0016] The surface of the lowest component, which is usually flat before forming or high-temperature bonding, is typically the surface onto which the reflective coating is applied after post-processing, e.g., polishing, in the case of a mirror. The formed surface is adapted to the geometry of the optically effective surface or corresponds to it (as a negative mold). If the subsequent optically effective surface is concave or convex, the formed surface is also convex or concave and typically has the same radius of curvature.

[0017] If the joining surface is aligned parallel to the surface of the component being deformed or reshaped before forming, and is lowered onto the formed surface during forming, the joining surface typically also follows the geometry of the optically effective surface. The surface of the optical component that comes into contact with the formed surface during forming, and also the joining surface, are typically planar before high-temperature bonding. The optical component is typically held at a temperature above the glass transition temperature until the lowering of the underside of the optical component onto the formed surface is complete. For this purpose, it may be sufficient if the optical component is heated to a temperature-time profile of, for example, approximately...It is heated at 50 K / h, and typically needs to be held at a holding temperature above the glass transition temperature for a certain period of time.

[0018] As described above, the optically effective surface on the shaped optical component is typically created after cooling by mechanical processing, such as grinding or polishing. If the geometry of the surface on which the optically effective surface is created after cooling already substantially corresponds to the geometry or curvature of the optically effective surface before processing, the material removal during machining can be reduced. Furthermore, a largely homogeneous material removal can be achieved during mechanical processing.

[0019] In another variant, the shaped surface has a PV value of at least 0.5 mm, preferably at least 1 mm, and particularly at least 5 mm. The PV value, as is generally understood, is the distance between the highest point and the lowest point of the surface profile of a shaped surface, relative to a base profile in the form of a flat surface.

[0020] The surface of the optical component that comes into contact with the shaped surface during lowering exhibits a PV value after lowering that corresponds to the PV value of the shaped surface. The deformation or curvature of the optical component at the surface that comes into contact with the shaped surface, caused by the lowering process, can be chosen to be sufficiently large to follow the curvature of the optically effective surface to which the reflective coating is applied.

[0021] As described above, a suitable temperature-time profile during annealing or cooling of the optical component to temperatures below the glass transition temperature can also achieve deformation, i.e., a controlled deformation of the optical component. However, the curvature achievable in this way is significantly less than with the gravity forming described above; that is, typically only PV values ​​of less than approximately 100 µm can be generated on the deformed surface. Generally, the optical component, or its sub-bodies, when placed on a flat surface, will warp. The side facing the flat surface will be concave, while the side facing away from the surface will be convex. This is due to temperature gradients within the glass material during cooling. This effect can be used to selectively deform or warp the optical component.However, the effect of the deformation that occurs above the glass transition temperature is usually significantly greater. The effect occurring during cooling can therefore potentially be ignored, especially since the optical component is post-processed after high-temperature bonding to create the optically effective surface.

[0022] In addition to the deformation of the optical component or its sub-bodies, the deformation of the substrate or mold during annealing, caused by thermal stress and pressure exerted by the resting sub-bodies or the optical component, must also be considered. It can be particularly advantageous to perform an intermediate or holding step at a predetermined holding temperature during the cooling phase of the annealing process, in which the optical component is cooled from a temperature above its glass transition temperature to room temperature. This ensures that the entire system—i.e., the optical component and the substrate or mold—reaches a homogeneous temperature. The holding temperature could, for example, be on the order of 700°C.

[0023] In a further development of this variant, prior to high-temperature bonding, a first contact surface of a first sub-body and a second contact surface of a second sub-body are brought into contact and preferably joined by blasting. During high-temperature bonding, the two sub-bodies fuse together at the contact surfaces, forming the joining surface or one of the joining surfaces. The first contact surface of the first sub-body and the second contact surface of the second sub-body can be planar, spherical, aspherical, or freeform.

[0024] It is advantageous to bring the components into contact at their interfaces and bond them together by blasting before high-temperature bonding. Blasting two or more glass components together is a long-established method for joining two glass parts. During blasting, the surfaces of two sufficiently smooth components are brought into close contact, usually at room temperature, with the two interfaces bonding through van der Waals forces or hydrogen bonds. This type of bond between the two components is reversible; that is, the components bonded by blasting can be separated, for example, by inserting a wedge at the bond point. See also the article "Wafer direct bonding: tailoring adhesion between brittle materials," A. Plößl et al., Material Science and Engineering: R: Reports, Volume 25, Issues 1-2, 10 March 1999, p. 1-88. The subsequent high-temperature bonding can significantly increase the adhesive strength and stiffness of the optical component.

[0025] It can be advantageous for the connecting surfaces, and consequently the subsequent joining surface, to have a curvature, for example, when cooling channels are incorporated that are intended to maintain a constant distance from a curved, optically effective surface. In the variant described here, the two sub-bodies can be blasted together at their connecting surfaces, and during high-temperature bonding, the optical component can be reshaped to create a joining surface that deviates from the geometry of the connecting surfaces. For example, reshaping the optical component can increase the curvature of the joining surface, decrease it, or even eliminate the curvature of the joining surface altogether.

[0026] In a further development of this variant, channels for fluid flow are formed on the first and / or second joining surface prior to high-temperature bonding. These channels are preferably formed by mechanical machining. For example, the channels can be created by material removal, such as milling or grinding, on the respective joining surface. When the two sub-bodies are joined along the joining surfaces, the cross-section of the channels is closed circumferentially. After high-temperature bonding, the channels follow the curved or convex joining surface. If the curved or convex optically utilized surface runs essentially parallel to the curved or convex surface, the channels are formed by the convex or convex surface.With a curved joining surface, the channels can maintain a uniform, constant distance from the optically used surface without requiring the two sub-bodies to be joined along curved connecting surfaces. This reduces manufacturing times for the optical component, increases yield, and lowers scrap rates.

[0027] In a further aspect of the invention, which can be combined in particular with the aspect described above, at least one defect, preferably a plurality of defects, particularly preferably in the form of particles, especially polymer particles, resin particles or metal particles, is introduced between the component bodies before joining, and / or at least one local depression is formed on at least one joining surface of at least one of the component bodies by local material removal before joining the component bodies, and during joining, preferably by high-temperature bonding, a closed cavity is formed in the area of ​​at least one joining surface around the at least one defect and / or at the at least one local depression. The particles are typically microparticles or, optionally, nanoparticles.

[0028] In this variant, the joining or joining of two or more sub-bodies is used to create one or more closed cavities within the optical component. These closed cavities can serve to dampen material stresses and / or to selectively influence the geometry of the optically effective surface of the optical component, and thus its optical effect. For this purpose, the closed cavities are typically positioned at a defined distance from the optically effective area or surface, determined by the position of the joining surface. These local, closed cavities are typically filled with air or partially with remnants of the respective defect, and therefore act as stress dampers and / or enable the targeted local modification of the surface geometry of the optically effective surface.

[0029] The closed cavities can be arranged, in particular, between the optically active surface and an area where mechanical stress is applied towards the optically active surface. For example, the closed cavities can be arranged between an optically used portion of the optically active surface on the front side of the optical component and a rear side of the optical component where the mechanical stresses are applied. By reducing the mechanical stresses, system performance can be improved. Furthermore, the specification for the optically used portion of the optically active surface can potentially be relaxed, as a disturbance in the system can be avoided.

[0030] The defects prevent the component parts from bonding together at the joining surface in a locally confined area around the defects, creating a closed cavity between the locally unbonded joining surfaces. To generate or enhance the stress-damping effect of these closed cavities, it is advantageous for the defects to be compressed during joining, for example, during high-temperature bonding. This is generally not the case with particles in the form of metallic spheres or platelets, nor with spheres or platelets made of glass. In particular, polymer particles, resin particles, and, if necessary, metal particles have proven to be suitable materials for the defects, as they compress upon heating; however, other materials can also be used for this purpose. Polymer particles with a size distribution exhibiting a precisely defined mean diameter, i.e.,Particles with low variance in particle size are typically commercially available for a large diameter range, e.g., from approximately 100 nm to approximately 300 µm.

[0031] One or more of the closed cavities can also be formed by creating a local depression in at least one of the connecting surfaces of the two sub-bodies by locally removing material from the connecting surface. This local material removal can be achieved, for example, by laser processing or by other means, such as mechanical processing like grinding or milling. In this case, the closed cavity is formed because the connecting surface of the other sub-body covers the depression along the joining surface during the joining process. Unlike the formation of channels through which a temperature control medium can flow, the cavities formed during joining in this case are closed.

[0032] The joining of the individual components is achieved using a joining process that ensures a permanent bond throughout the entire lifespan of the optical component. This joining process can be the high-temperature bonding described above, but it is also possible to permanently join the components, for example, by bonding at lower temperatures, potentially without exceeding the glass transition temperature. A prerequisite for the method described here is that the design of the optical component allows it to be divided along at least one surface that corresponds to the subsequent joining surface.

[0033] In one variant, the defects are positioned at predetermined locations on the joining surface of at least one component before joining. Positioning is preferably automated; for example, the particles can be applied to the joining surface using a sputtering process or a stencil. It is advantageous if the defects are positioned at defined locations rather than in a statistical distribution on the joining surface.

[0034] In another embodiment, the closed cavities have a maximum extent of no more than 50 µm, preferably no more than 30 µm, and particularly no more than 10 µm, perpendicular to the joining surface, and / or they have a width-to-height ratio of at least 50:1, preferably at least 100:1, and particularly at least 500:1. The width of the closed cavities is measured parallel to the joining surface and denotes the maximum extent of the respective cavity between two points of the cavity parallel to the joining surface. The height of the closed cavities is measured perpendicular to the joining surface and denotes their maximum extent between two points perpendicular to the joining surface. In contrast to the first aspect of the invention described above, the joining surface in the example shown is generally planar. The connecting surfaces are also generally designed as planar surfaces.

[0035] The diameter of the defects or particles before joining typically determines the height of the closed cavities; that is, the height of the closed cavities generally corresponds to the order of magnitude of the diameters of the defects or particles before they are compressed. If the cavities, and thus the defects, have a comparatively small height or diameter, the component parts can be pressed together before joining, as described above in connection with the first aspect of the invention. Generally, the component parts are appropriately aligned relative to each other before being joined along the joining surface(s).

[0036] Unlike the height, the width of the closed cavities is usually significantly larger than the diameter of the defects. The ratio between the maximum width of the cavities and their maximum height, i.e., the aspect ratio, typically falls within the range specified above. Since the size of the defects essentially determines the dimensions of the closed cavities, a wide range of sizes for the closed cavities is possible.

[0037] Despite the relatively small defect that is typically compressed during joining, the two joining surfaces generally do not bond over a relatively large area around the defect along the joining surface, resulting in a closed cavity with a comparatively large width. Since a small cavity height is sufficient for stress-damping, a closed cavity with such an aspect ratio is particularly well-suited to generating stress-damping effects over a relatively large area or width. For this purpose, the joining surface is preferably oriented essentially perpendicular to the direction in which the mechanical stresses are introduced into the material of the optical component.

[0038] In another variant, the defects are introduced laterally offset between each pair of sub-bodies, so that the closed cavities are formed laterally offset from each other on at least two joining surfaces, with the closed cavities of a first joining surface preferably extending at least partially between the laterally offset closed cavities of a second joining surface. For the mechanical stability of the optical component, it is typically necessary that immediately adjacent closed cavities have a sufficient lateral distance from each other. However, no stress-damping effect is achieved in the area between the closed cavities.It is therefore advantageous if the stress-damping effect is enhanced by forming closed cavities along a second joining surface, which are laterally offset and which at least partially fill the gaps between the closed cavities of the first joining surface in order to enhance the stress-damping effect.

[0039] In one variant, a gas, preferably air, is enclosed in the at least one closed cavity during its formation. As described above, the enclosed gas, which is typically air, can have a stress-damping effect. The gas enclosed in the closed cavity has a pressure that typically corresponds to the ambient pressure during the manufacture of the optical component or when the connecting surfaces of the component parts are brought into contact. The ambient pressure during the manufacture of the optical component is typically atmospheric pressure. If the optical component is operated in a semiconductor technology system at an ambient pressure that differs from the pressure prevailing during manufacture or from the pressure present in the closed cavity, the pressure difference can lead to pressure penetration or...leading to a deformation of the material of the optical component located between the closed cavity and an optically effective surface of the optical component.

[0040] If the pressure in the closed cavity is greater than the ambient pressure during operation of the optical component, this typically leads to local deformation in the form of a local elevation at the optically effective surface. If the distance of the closed cavity to the optically effective surface, the dimensions of the closed cavity, and the ambient conditions, e.g., pressure and temperature, are known during manufacturing or when the gas is enclosed in the respective cavity, as well as during operation of the optical component, the local deformation effect caused by the enclosed gas can be calculated or predicted. Accordingly, the parameters during the manufacturing of the respective closed cavity can be selected to achieve the desired deformation effect at the optical surface.

[0041] It is also possible, in principle, to introduce cavities into glass materials by irradiation with ultrashort pulse lasers without carrying out a joining process; see, for example, the article "Void formation in glasses," T. Hashimoto et al., New Journal of Physics, 2007, No. 8, pp. 253ff., or the article "Well-controlled femtosecond laser inscription of periodic void structures in porous glass for photonic applications," Optics Express, 2017, No. 26, pp. 33261-33270. However, the state of the air or gas present in the cavities or closed spaces is unknown in these cases and cannot be easily controlled.

[0042] In another variant, the sub-bodies are made of quartz glass, preferably titanium-doped quartz glass, a glass ceramic, or silicon. Titanium-doped quartz glass and certain glass ceramics exhibit a particularly low coefficient of thermal expansion and are therefore especially suitable for the production of substrates for EUV mirrors. Silicon can also be used as a substrate material for EUV mirrors, particularly when they are operated under grazing incidence. Silicon sub-bodies can also be detachably joined by blasting and subsequently permanently bonded by high-temperature bonding. In this case, a thermal imaging camera, for example in the form of a SWIR camera, can be used for potential in-line process monitoring during blasting and inspection.It is understood that the optical component can also be manufactured from sub-bodies made of other suitable materials, which can be joined together by high-temperature bonding.

[0043] Another aspect of the invention relates to an optical component, preferably a mirror, particularly for reflecting EUV radiation, which is manufactured by the method described above. The optical component, in the form of a mirror, has a reflective coating on an outer surface, which forms the optically effective surface. The reflective coating is typically applied to the outer surface, usually to a portion of the outer, optically effective surface, only after the component parts have been joined. If the component parts are made of glass, the reflective coating is generally a multilayer coating comprising a plurality of alternating layers with different refractive indices.Especially if the optical component is to be reshaped, particularly curved, during high-temperature bonding, it has proven advantageous if it has a thickness that is not too great, ideally on the order of less than one meter.

[0044] In one embodiment of the optical component, the glass material exhibits striae that follow the geometry of a curved, optically used surface of the optical component and / or at least one joining surface. On an optical component made of fused silica or titanium-doped fused silica, it can generally be directly demonstrated that at least one outer surface and / or a joining surface was deformed or warped during high-temperature bonding: These glass materials exhibit striae due to the manufacturing process, which, in the component parts prior to joining, run essentially in planes parallel to the plane and perpendicular to the axial direction of the glass body. If the joining surface or the outer surfaces are warped during high-temperature bonding, the orientation of the striae also changes; that is, they follow the curvature of the optical component.If channels with, for example, a rectangular cross-section are incorporated into the material of the optical component, the streaks will continue to run parallel to the walls on the top and bottom of the channels, as well as perpendicular to the side walls of the channels. This indicates that the tempering process took place after the channels were incorporated. With other materials that exhibit a characteristic streak pattern, it can also be directly demonstrated on the optical component that it was deformed or warped during high-temperature bonding.

[0045] In a further embodiment, the optical component has closed cavities in the area of ​​the at least one joining surface, which preferably have a maximum extent of no more than 50 µm, particularly preferably no more than 30 µm, and especially no more than 20 µm, perpendicular to the joining surface, and / or preferably have a width-to-height ratio of at least 50:1, particularly preferably at least 100:1, and especially at least 500:1. As described above, such cavities can be created by introducing defects, in particular particles, between the component parts, around which the closed cavities are formed.

[0046] Another aspect of the invention relates to a semiconductor technology system, in particular an EUV lithography system, comprising: at least one optical component designed as described above, wherein preferably a gas, in particular air, is enclosed in the at least one closed cavity of the optical component, and the optical component is arranged in the semiconductor technology system in a vacuum environment whose pressure is lower than the pressure of the gas in the closed cavity, whereby at least one local elevation forms on an optically effective surface of the optical component in the area of ​​the at least one closed cavity.

[0047] For the purposes of this application, a semiconductor technology system is understood to be an optical system for lithography, i.e., an optical system that can be used in the field of lithography. In addition to a lithography system used for the production of semiconductor devices, the system may, for example, be an inspection system for inspecting a photomask (hereinafter also referred to as a reticle) used in a lithography system, for inspecting a semiconductor substrate to be structured (hereinafter also referred to as a wafer), or a metrology system used for measuring a lithography system or parts thereof, for example, for measuring a projection system.

[0048] The semiconductor technology system can be operated using useful radiation in the form of EUV radiation. EUV radiation is defined as radiation in a wavelength range between approximately 5 nm and 30 nm, for example, at 13.5 nm. Since EUV radiation is strongly absorbed by most known materials, it is typically guided through the semiconductor lithography system using optical components such as EUV mirrors.

[0049] As described above, the pressure difference between the pressure of the gas enclosed in the respective cavity and the lower pressure in the vacuum environment of the optical component can create at least one local elevation on an optically effective surface of the optical component within the area of ​​the at least one closed cavity. This local elevation allows the optical effect of the optical element to be selectively influenced. The size of the local elevation formed in this way can be smaller than the smallest possible local elevation that can be produced by machining the optically effective surface with a machining tool.

[0050] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, with reference to the figures in the drawing, which show details essential to the invention, and from the claims. The individual features can be implemented individually or in any combination in a variant of the invention. drawing

[0051] Examples of implementation are shown in the schematic drawing and are explained in the following description. It shows Fig. 1. Schematic representation in meridional section of a projection exposure system for EUV projection lithography, Fig. 2a a schematic representation of two sub-bodies which are placed on a shaped surface of a substrate before high-temperature bonding, Fig. 2b a schematic representation of a curved optical component after high-temperature bonding of the two sub-bodies, Fig. 3 a schematic representation analogous to Fig. 2a, in which the two partial bodies are placed on a shaped surface of the base of a casting mold, Fig. 4a,b Schematic representations of two sub-bodies or an optical component that rests on a flat surface during high-temperature bonding, before and after cooling. Fig. 5a-d schematic representations of process steps for producing closed cavities in an optical component, Fig. 6a,b schematic representations of the optical component of Fig. 5a-d and a further optical component which has additional closed cavities laterally offset along a joining surface, as well as Fig. 7a-d schematic representations of process steps for manufacturing an optical component with closed cavities and of an optical component manufactured in this way in operation in a vacuum environment.

[0052] In the following description of the drawings, identical reference symbols are used for identical or functionally equivalent components.

[0053] The following will refer to Fig. 1. The essential components of an optical arrangement for EUV lithography, in the form of a projection exposure system 1 for microlithography, are described as an example. The description of the basic structure of the projection exposure system 1 and its components is not to be understood as restrictive.

[0054] One embodiment of a lighting system 2 of the projection exposure system 1 has, in addition to a light or radiation source 3, a lighting 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 lighting system. In this case, the lighting system does not include the light source 3.

[0055] A reticule 7 located in the object field 5 is illuminated. The reticule 7 is held by a reticule holder 8. The reticule holder 8 can be moved, particularly in one scanning direction, via a reticule displacement drive 9.

[0056] In Fig. Figure 1 shows a Cartesian xyz coordinate system for illustrative purposes. The x-direction runs perpendicular to the plane of the drawing. The y-direction runs horizontally, and the z-direction runs vertically. The scan direction runs in the Fig. 1 along the y-direction. The z-direction runs perpendicular to the object plane. 6.

[0057] The projection exposure system 1 comprises a projection system 10. The projection system 10 serves to image the object field 5 onto an image field 11 in an image plane 12. A structure on the reticulum 7 is imaged onto a light-sensitive layer of a wafer 13 located in the image plane 12 within the area of ​​the image field 11. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be displaced, particularly along the y-direction, via a wafer transfer drive 15. The displacement of the reticulum 7 via the reticulum transfer drive 9 and of the wafer 13 via the wafer transfer drive 15 can be synchronized with each other.

[0058] Radiation source 3 is an EUV radiation source. Specifically, radiation source 3 emits EUV radiation 16, which is also referred to below as useful radiation, illumination radiation, or illumination light. The useful radiation has a wavelength in the range between 5 nm and 30 nm. Radiation 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. Radiation source 3 can be a free-electron laser (FEL).

[0059] The illumination radiation 16 emanating from the radiation source 3 is focused by a collector mirror 17. The collector mirror 17 can be a collector mirror with one or more ellipsoidal and / or hyperboloid reflective surfaces. The at least one reflective surface of the collector mirror 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 mirror 17 can be structured and / or coated to optimize its reflectivity for the useful radiation and to suppress stray light.

[0060] After the collector mirror 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 radiation source 3 and the collector mirror 17, and the illumination optics 4.

[0061] 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 a beam-shaping effect in addition to its deflecting function. 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. The first faceted mirror 20 comprises a plurality of individual first facets 21, which are hereinafter also referred to as field facets. Of these facets 21, the Fig. 1 Only a few examples are shown. In the beam path of the lighting optics 4, a second faceted mirror 22 is arranged downstream of the first faceted mirror 20. The second faceted mirror 22 comprises a plurality of second facets 23.

[0062] The illumination optics 4 thus form a double-faceted system. This basic principle is also known as a honeycomb condenser (fly's eye integrator). 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.

[0063] The projection system 10 comprises a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

[0064] In the Fig. In the example shown, the projection system 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or any other number of mirrors Mi are also possible. In the example shown, the penultimate mirror M5 and the last mirror M6 each have a passage for the illumination radiation 16. The projection system 10 is a double-obscured optic. The projection optic 10 has an image-side numerical aperture that is greater than 0.4 or 0.5 and can also be greater than 0.6, for example, 0.7 or 0.75.

[0065] The mirrors Mi, just like the mirrors of the lighting optics 4, can have a highly reflective coating for the lighting radiation 16.

[0066] Fig. Figures 2a and 2b show an optical component in the form of a mirror Mi of projection system 10 during its manufacture. The mirror has a first, essentially plate-shaped subbody 25 and a second subbody 26. In the example shown, the two subbodies 25 and 26 are made of a glass material in the form of titanium-doped quartz glass, but they could also be made of another material with a low coefficient of thermal expansion. In the example shown, the two subbodies 25 and 26 are circularly cylindrical, with the cylinder axis, or the axial direction, of the two subbodies 25 and 26 running parallel to the direction of gravity, which corresponds to the Z-direction of an XYZ coordinate system. The two subbodies 25 and 26 have in Fig. 2a each has a flat top surface 25a, 26a and a flat bottom surface 25b, 26b. The top surface 25a of the first sub-body 25 and the bottom surface 26b of the upper sub-body 26 form two connecting surfaces 25a, 26b, at which the sub-bodies 25, 26 abut each other. The bottom surface 25b of the first sub-body 25 and the top surface 26a of the second sub-body 26 form the outer surfaces of the mirror Mi.

[0067] The in Fig. 2a The upper subbody 26 has a plurality of channels 27 at the connection surface 26b, designed for the flow of a fluid. The channels 27 were introduced into the glass material of the second subbody 26 in a previous process step by mechanical processing, more precisely by grinding.

[0068] At the in Fig. In the example shown in Figure 2a, the two sub-bodies 25, 26 are in contact with each other at the planar connecting surfaces 25a, 26b and are detachably joined by blasting. The two blasting-together sub-bodies 25, 26 are placed on a base 28 for joining and placed in a tempering furnace for high-temperature bonding. In the tempering furnace, the two sub-bodies 25, 26 are heated to a temperature above the glass transition temperature, in this case approximately 1000°C, whereby the glass material in the area of ​​the two connecting surfaces 25a, 26b melts and the two sub-bodies 25, 26 fuse to form a joining surface 29. Fig. Connect the mirror shown in 2b.

[0069] At the in Fig. In the example described in 2a,b, high-temperature bonding is additionally used to reshape, or more precisely, to convexly curve, the mirror Mi. For this purpose, the two subbodies 25, 26 are placed on a shaped, in the example shown, convexly curved surface 30 of the base 28 before being joined. During high-temperature bonding, the two subbodies 25, 26, or the emerging mirror Mi, are reshaped in a viscous state by being lowered onto the shaped surface 30. During lowering, the underside 25b of the first subbodie 25 assumes the geometry of the shaped surface 30 of the base 28. In the example shown, the shaped surface 30 of the base 28 has a convex geometry that corresponds to the concave geometry of an optically effective surface 31 of the mirror Mi, which is shown in Fig. Figure 2b illustrates this. To enable this, the shaped surface 30 of the base 28 has a PV value of at least 0.5 mm, at least 1 mm, or at least 5 mm. In the example shown, the PV value corresponds to the maximum height H of the curved surface 30 with respect to a flat section of the base 28.

[0070] As in Fig. As can be seen in 2b, the optically effective surface 31 runs in Fig. 2b below the curved outer surface 25b of the first subbody 25 during high-temperature bonding. Since the curvature of the outer surface 25b of the first subbody 25 corresponds to the curvature of the optically effective surface 31, it can be formed by homogeneous material removal from the first subbody 25.

[0071] As in Fig. As can also be seen in 2b, the channels 27, which are intended for the flow of a fluid, also follow the curved or convex joining surface 29 resulting from high-temperature bonding. Since the optically effective surface 31 runs parallel to the concavely curved outer surface 25b of the mirror Mi, the channels 27 have a constant distance d from the later optically effective surface 31. In a subsequent step, a coating is applied to the optically effective surface 31. Fig. 2a,b reflective coating not shown applied to complete the manufacture of mirror Mi.

[0072] At the in Fig. In the mirror shown in Figure 2b, the channels 27 follow the curvature of the joining surface 29, although the connecting surfaces 25a, 26b of the two subbodies 25, 26 of Fig. 2a are formed plan. Due to the warping of the glass material of the mirror Mi during high-temperature bonding, any striae 32 present in the glass material, which are in Fig. 2a run in mutually parallel XY planes, one of which is in Fig. 2a is shown in the illustration, curved and running parallel to the curved joining surface 29, as shown in Fig. 2b can be seen.

[0073] The related to Fig. In the manner described in 2a,b, not only can mirrors Mi with concave or convex curved outer surfaces 25b, 26a be produced, but also mirrors Mi whose outer surfaces 25b, 26a have a basically arbitrary shape. Fig. Figure 3 shows the two partial bodies 25, 26, which are placed on a shaped surface 30 designed as a freeform surface, forming the base of a mold 33. A circumferential side wall 34 of the mold 33 prevents the two partial bodies 25, 26 from slipping laterally during lowering by gravity. This also applies to the Fig. In the example shown in Figure 3, the shaped surface 30 on the bottom of the mold 33 is designed such that it corresponds to the geometry of an optically effective surface of the mirror Mi to be produced.

[0074] Fig. Figures 4a and 4b show a mirror Mi placed on a flat surface 28 during cooling after the glass transition temperature has been undershot during high-temperature bonding. Fig. Figure 4a shows the isotherms of the temperature distribution in the mirror Mi in the second subbody 26. When the mirror Mi cools, radially outer volume regions cool down faster and therefore solidify faster than radially inner volume regions. This leads to mechanical stresses in the glass material of the mirror Mi, which act essentially in a radial direction towards the central axis of the essentially cylindrical subbodies 25, 26, as shown in Fig. 4a is indicated.

[0075] The mechanical stresses cause the mirror Mi to warp as it cools further, as shown in Fig. 4b can be seen. The outer surface 25b of the first subbody 25, on which the optically active surface is to be formed, is convexly curved, while the outer surface 26a of the second subbody 26 is concavely curved. The PV value of the convexly curved outer surface, or the height h1 with respect to the lateral edge of the mirror Mi, is approximately 100 µm in the example shown, and the PV value, or the height h2, of the concavely curved outer surface 26a of the mirror Mi is approximately 70 µm. The diameter of the in Fig. The mirror Mi shown in 4a,b was approximately 400 mm. The one in Fig. The effect of the curvature of the mirror Mi shown in 4a,b during cooling is therefore comparatively small and does not usually make it possible to adapt the geometry of the outer surfaces 25b, 26a to the curved optically effective surface of the mirror Mi.

[0076] Fig. Figures 5a-d show several steps in the manufacture of a mirror Mi, which, for the purpose of damping mechanical stresses, has four closed cavities 35a-d, as shown in Fig. 5d can be seen.

[0077] At the in Fig. In the process step shown in Figure 5a, a blank made of a glass material is first divided along a flat surface into two sub-bodies 25, 26. Subsequently, four defects 36a-d are positioned on the top surface 25a of the lower sub-body 25 at predetermined positions on the top surface 25a of the lower sub-body 25, as shown in Figure 5a. Fig. Figure 5b shows the defects 36a-d, which are arranged at equal lateral distances from each other. In the example shown, the defects 36a-d are particles, for example polymer particles, with a diameter on the order of approximately 5 µm. The polymer particles are in Fig. Figures 5b-d are shown significantly larger for illustrative purposes than they appear in reality. Resin particles, metal particles, or possibly dust particles can be used instead of polymer particles.

[0078] In a Fig. In the process step shown in 5c, the second subbody 26 is placed on the first subbody 25, so that the defects 36a-d are introduced between the two subbodies 25, 26. The second subbody 26 is aligned relative to the first subbody 25 in a suitable manner. Unlike in Fig. As shown in 5c, the two sub-bodies 25, 26 can be blasted together despite the defects 36a-d at the two opposing connecting surfaces 25a, 26b.

[0079] In a subsequent step, the two sub-bodies 25, 26 are joined together by high-temperature bonding along the two contacting connection surfaces 25a, 26b, forming a joining surface 29. At or in the area of ​​the joining surface 29, a closed cavity 35a-d forms around each defect 36a-d, in which the two connection surfaces 25a, 26b are not joined together. The defects 36a-d, in the form of polymer particles, shrink, i.e., they are compressed, as can be seen by comparing Fig. 5c and Fig. 5d can be seen.

[0080] The size of each closed cavity 35a-d can be adjusted by the diameter of the defects 36a-d. In the case of the Fig. In the example shown in Figure 5d, the closed cavities 35a-d perpendicular to the flat joining surface 29 have a maximum extent of no more than 50 µm, no more than 30 µm, or more precisely, no more than 20 µm. The ratio of the maximum width b along the flat joining surface 29 to the maximum height h of the closed cavities 35a-d is at least 50:1, at least 100:1, and in particular at least 500:1.

[0081] The closed cavities 35a-d with the aspect ratio described above make it possible to effectively dampen mechanical stresses that are introduced into the glass material of the mirror Mi perpendicular to the underside 25b of the first subbody 25, as is the case in Fig. 6a is indicated by arrows. In this way, the optically active surface 25a of the mirror Mi, or the optically active part of the surface 25a on which a reflective coating 37 is applied, can be effectively protected from the effects of mechanical stresses.

[0082] Since the closed cavities 35a-d cannot be positioned arbitrarily close to one another in the lateral direction, i.e., parallel to the joining surface 29, it is advantageous to form another joining surface 29' between the first sub-body 25 and a third sub-body 38. The third sub-body 38 is connected to the first sub-body 25 in the manner described above, as shown in Fig. 6b is shown.

[0083] Defects 36e-g are also introduced between the first sub-body 25 and the third sub-body 38, resulting in the formation of closed cavities 35e-g along the further joining surface 29' during high-temperature bonding. The closed cavities 35e-g on the further joining surface 29' are laterally offset from the closed cavities 35a-d of the joining surface 29; more precisely, they run at least partially laterally offset between each pair of adjacent closed cavities 35a-d of the joining surface 29. In this way, mechanical stresses introduced into the material of the mirror Mi between the closed cavities 35a-d of the joining surface 29 can also be dampened, as described in Fig. 6b is indicated by three further arrows.

[0084] Fig. Figures 7a-c show process steps in the manufacture of a mirror Mi, analogous to Fig. 5a-d closed cavities 35a,b are to be formed at the joining surface 29 between the two partial bodies 25, 26. A first closed cavity 35a is formed as in Fig. 5a-d described by introducing a particle 36, in the example shown a metal particle, between the two partial bodies 25, 26, as is done in Fig. Figure 7a shows that around particle 36, a layer forms in the Fig. 7b shows the joining of the two partial bodies 25, 26 by high-temperature bonding in the area of ​​the joining surface 29, resulting in the first closed cavity 35a.

[0085] A second closed cavity 35b is created in the Fig. The example shown in 7a-c is formed by creating a local depression 39 on the joining surface 26b of the second part 26 by removing material before joining the two sub-bodies 25, 26, as shown in Fig. 7a. The recess 39 is essentially cylindrical in the example shown, but can also have a different geometry. The recess 39 can be produced, for example, by laser processing, but also by mechanical processing, e.g., by milling or grinding. When the two partial bodies 25a, 25b are joined by high-temperature bonding along the joining surface 29, the second closed cavity 35b is formed at or in the area of ​​the recess 39, as shown in Fig. 7b can be seen.

[0086] As in Fig. As shown in Figure 7c, the top surface 26a of the second sub-body 26, which is the surface that will later become the optically effective surface of the mirror Mi, is machined with a tool 40 to create a desired surface geometry, which in the example shown is a concave, spherical surface geometry. A reflective coating 37 is then applied to the concavely curved top surface 26a of the second sub-body 26, as described above in connection with Fig. 6a was described.

[0087] The production of the Mi mirror in the in Fig. The steps shown in 7a-c were carried out under manufacturing conditions Z0(p0, T0) at an ambient pressure p0 corresponding to atmospheric pressure. The steps shown in Fig. 7a and Fig. The steps shown in section 7c were carried out at an ambient temperature T0, which corresponds to room temperature (21°C), as described in Fig. The high-temperature bonding step described in 7b was carried out at an ambient temperature T0 that was higher than room temperature. In the vicinity of the two subbodies 25, 26, in particular during the step described in Fig. In step 7a, where the two sub-bodies 25, 26 are brought into contact, a gas, typically air, is present. When the two sub-bodies 25, 26 are brought into contact along the connecting surfaces 25a, 26b, the ambient air is trapped in the closed cavities 35a, 35b. The air trapped in the closed cavities 35a, 35b therefore typically has a pressure p0 that corresponds to the ambient pressure during the manufacture of the mirror Mi.

[0088] Fig. Figure 7d shows the mirror Mi, which is in the projection exposure system 1 of Fig. 1 is operated under operating conditions Z1(p1, T1). The temperature T1 under the operating conditions essentially corresponds to room temperature, i.e., 21°C. However, the ambient pressure p1 under operating conditions is significantly lower than the ambient pressure p0 during the manufacture of the mirror Mi, since the mirror Mi is located in a vacuum environment 42 during the operation of the projection exposure system 1. Due to the pressure difference between the pressure p0 within the respective closed cavities 35a, 35b and the ambient pressure p1 in the vacuum environment 42, the material of the second sub-body 26 is forced through the top surface 26a of the second sub-body 26, onto which the reflective coating 37 is applied. During this forced through, local protrusions 41a, 41b are formed in the area of ​​the closed cavities 35a, 35b on the top surface 26a of the second sub-body 26.

[0089] The height of each local elevation 41a, 41b depends, in addition to the pressure difference p1 - p0, primarily on the distance D between the closed cavities 35a, 35b or the joining surface 29 and the top surface 26a of the second subbody 26. The width or lateral extent of each local elevation 41a, 41b depends on the width b1, b2 of the respective closed cavity 35a, 35b. The width b1 of the closed cavity 35a, in which the particle 35a is located, can be predetermined as described above; the width b2 of the closed cavity 35b, which is formed at the recess 39, can be predetermined during the machining process for producing the recess 39.

[0090] By enclosing air bubbles in the closed cavities 35a, 35b under known manufacturing conditions Z0(p0, T0), local protrusions 41a, 41b, ... can be selectively created whose lateral extent or width b1, b2 is smaller than the sub-aperture of the tool 40 used to machine the top surface 26a of the second sub-body 26. If the manufacturing conditions Z0(p0, T0) during the introduction of the air or gas bubbles into the closed cavities 35a, 35b, the operating conditions Z1(p1, T1), the distance D of the joining surface 29 from the top surface 26a of the second sub-body 26, and the width b1, b2 of the respective closed cavity 35a, 35b are known in advance, the degree of penetration can be calculated beforehand or used to predict the geometry of the local protrusion 41a, 41b in the operating state.It is advantageous to measure the surface geometry of the upper surface 26a in the operating state before installing the mirror Mi in the projection exposure system, with the mirror Mi typically being placed in a vacuum environment for the measurement. Such a measurement can also be carried out in situ, if necessary, to measure the exact geometry of the local protrusions 41a, 41b and thus to predict their optical effect as precisely as possible.

[0091] It is understood that optical components other than the mirrors Mi described above can also be manufactured in the manner described here. In particular, the sub-bodies 25, 26, 38 can also be made of other materials that can be joined together by high-temperature bonding. 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] WO 2022 / 214290A1

[0007] WO 2020 / 207741A1

[0008] Cited non-patent literature

[0000] A. Plößl et al., Material Science and Engineering: R: Reports, Volume 25, Issues 1-2, 10 March 1999, p. 1-88

[0024] Void formation in glasses”, T. Hashimoto et al., New Journal of Physics, 2007, No. 8, page 253ff

[0041] Well-controlled femtosecond laser inscription of periodic void structures in porous glass for photonic applications", Optics express, 2017, No. 26, pp. 33261-33270.

[0041]

Claims

[1] Method for manufacturing an optical component, preferably a mirror, in particular an EUV mirror (Mi), comprising: Providing at least two sub-bodies (25, 26, 38), preferably made of at least one glass material, as well as Joining the at least two sub-bodies (25, 26, 38) to form the optical component by creating at least one joining surface (29, 29'), preferably by high-temperature bonding, characterized by , that the optical component is reshaped, in particular curved, during high-temperature bonding. [2] Method according to claim 1, wherein the partial bodies (25, 26) are placed on a shaped surface (30), which is preferably concave or convex curved, and the optical component is lowered onto the shaped surface (30) during high-temperature bonding. [3] Method according to claim 2, wherein the shaped surface (30) has a geometry that corresponds to the geometry of an optically effective surface (31) of the optical component. [4] Method according to claim 2 or 3, wherein the shaped surface (30) has a PV value of at least 0.5 mm, preferably at least 1 mm, in particular at least 5 mm. [5] Method according to one of the preceding claims, in which, prior to high-temperature bonding, a first connecting surface (25a) of a first partial body (25) and a second connecting surface (26b) of a second partial body (26) are brought into contact with each other and preferably joined together by blasting, wherein the two partial bodies (25, 26) join together at the connecting surfaces (25a, 26b) during high-temperature bonding, forming the joining surface (29). [6] Method according to claim 5, wherein channels (27) for flow through with a fluid are formed on the first joining surface (25a) and / or on the second joining surface (26b) prior to high-temperature bonding, wherein the formation of the channels (27) is preferably carried out by mechanical processing. [7] Method according to the preamble of claim 1, in particular according to one of the preceding claims, characterized by , that prior to joining the partial bodies (25, 26, 38) at least one defect, preferably a plurality of defects, particularly preferably in the form of particles (36a-d, 36e-g, 36), especially in the form of polymer particles, resin particles or metal particles, are introduced between the partial bodies (25, 26, 38), and / or that prior to joining the sub-bodies (25, 26) at least one local depression (39) is formed on at least one joining surface (26b) of at least one of the sub-bodies (25, 26) by local material removal, and that during joining, preferably by high-temperature bonding, a closed cavity (35a-d, 35e-g) is formed in the area of ​​at least one joining surface (29, 29') around the at least one defect and / or at the at least one local depression (39). [8] Method according to claim 7, wherein the defects are positioned at predetermined positions of a joining surface (25a) of at least one subbody (25, 26, 38) before joining. [9] Method according to one of claims 7 or 8, wherein the closed cavities (35a-d, 35e-g) perpendicular to the joining surface (29, 29') have a maximum extent of not more than 50 µm, preferably not more than 30 µm, in particular not more than 20 µm and / or have a width (b) to height (h) ratio of at least 50 : 1, preferably at least 100 : 1, in particular at least 500 :

1. [10] Method according to one of claims 7 to 9, wherein the defects (36a-d, 36e-g) are introduced laterally offset from each other between two of the partial bodies (25, 26; 25, 38), such that the closed cavities (35a-d, 35e-g) are formed laterally offset from each other on at least two joining surfaces (29, 29'), wherein preferably the closed cavities (35a-d) of a first joining surface (29) extend at least partially between the laterally offset closed cavities (35e-g) of a second joining surface (29'). [11] Method according to any one of claims 7 to 10, wherein, when forming the at least one closed cavity (35a-d, 35e-g), a gas, preferably air, is enclosed in the closed cavity (35a-d, 35e-g). [12] Method according to one of the preceding claims, wherein the partial bodies (25, 26, 38) are made of quartz glass, preferably titanium-doped quartz glass, a glass ceramic or silicon. [13] Optical component, preferably mirror, in particular EUV mirror (Mi) for reflecting EUV radiation (16), manufactured by a method according to one of the preceding claims. [14] Optical component according to claim 13, wherein the glass material has schlieren (32) which follow the geometry of a curved optically used surface (31) of the optical component and / or at least one joining surface (29, 29'). [15] Optical component according to claim 13 or 14, which has closed cavities in the area of ​​the at least one joining surface (29, 29') which preferably have a maximum extent of no more than 50 µm, particularly preferably no more than 30 µm, in particular no more than 20 µm, perpendicular to the joining surface (29, 29') and / or preferably have a width (b) to height (h) ratio of at least 50 : 1, particularly preferably at least 100 : 1, in particular at least 500 :

1. [16] Semiconductor technology plant (1), comprising: at least one optical component according to one of claims 13 to 15, wherein preferably a gas, in particular air, is enclosed in the at least one closed cavity (35a, 35b) of the optical component, and the optical component is arranged in the semiconductor technology system (1) in a vacuum environment (42) whose pressure (p1) is lower than a pressure (p0) of the gas in the closed cavity (35a, 35b), whereby at least one local elevation (41a, 41b) is formed on an optically effective surface (26a) of the optical component in the area of ​​the at least one closed cavity (35a, 35b).

Images