A method for incorporating a temperature-regulating hollow structure into a substrate, particularly a substrate for an optical element; a method for manufacturing an optical element; and a substrate for manufacturing an optical element, an optical element, and semiconductor technology equipment and structured electronic components.

Abstract

A method for incorporating a temperature-regulating hollow structure (22) into a substrate (12) for an optical element (8), particularly a mirror (10) of an EUV projection exposure apparatus, is described, comprising the steps of: (A) preparing a substrate (12) made of a substrate material (12a); (B) fabricating an intermediate structure (40) including an intermediate layer (42) of a modified substrate material (44) and an intermediate hollow structure (46) in which at least a portion of the area is surrounded by the intermediate layer (42), wherein the modified substrate material (44) is more sensitive to a chemically active processing medium than the substrate material (12a); and (C) introducing a processing medium (90) that removes the intermediate layer (42) of the modified substrate material (44) into the intermediate hollow structure (46), thereby generating a temperature-regulating hollow structure (22). The intermediate structure (40) is manufactured by step (B), which involves (B.1) sequentially focusing a modifying light beam (56) onto the modifying location (66) to form a modified substrate material (44) at the modifying location (66), and (B.2) sequentially focusing an ablation light beam (70) onto the ablation location (72) to remove the material at the ablation location (72). Furthermore, a method for manufacturing an optical element (8) and a substrate (12), and the optical element (8) are described. Furthermore, semiconductor technology equipment (6) and structured electronic components (224) are described.

Description

Technical Field

[0001] This application claims the priority of German Patent Application No. 102023205565.1 filed on June 14, 2023. The entire disclosure of the above application is incorporated herein by reference.

[0002] The present invention relates to a method of incorporating a temperature-regulating hollow structure into a substrate, particularly into a substrate of an optical element, especially a mirror of an EUV projection lithography apparatus, (A) preparing a substrate made of a substrate material; (B) producing an intermediate structure comprising a modified substrate material intermediate layer and an intermediate hollow structure at least partially surrounded by the intermediate layer, the modified substrate material being more sensitive to a chemically active treatment medium than the substrate material; (C) introducing a chemically active treatment medium for removing the intermediate layer of the modified substrate material into the intermediate hollow structure, thereby generating a temperature-regulating hollow structure and relates to a method comprising the above steps.

[0003] The present invention also relates to a method of manufacturing an optical element, particularly a mirror of an EUV projection lithography apparatus.

[0004] The present invention further relates to a substrate for manufacturing an optical element having a temperature-regulating hollow structure, particularly for manufacturing a mirror of an EUV projection lithography apparatus, an optical element comprising the substrate, particularly a mirror of an EUV projection lithography apparatus, and a semiconductor technology device and a structured electronic component.

Background Art

[0005] The following description of the present invention is based on an optical element in the form of a mirror and its use in an EUV projection lithography apparatus, in which heat is dissipated from the mirror by flowing a temperature-regulating fluid in the form of a cooling fluid through a temperature-regulating hollow structure present in the mirror.

[0006] However, in principle, the following explanation generally applies to optical elements to which a substrate made of a substrate material incorporating a temperature-regulating hollow structure may be assigned, through which a temperature-regulating fluid can be flowed for temperature compensation during the operation of the optical element.

[0007] In particular, optical elements are used in semiconductor technology equipment that irradiates an object with working radiation using one or more optical elements. In addition to EUV projection lithography equipment, other examples of such semiconductor technology equipment include mask inspection equipment and wafer inspection equipment.

[0008] On the other hand, temperature control may involve heating or cooling the optical element or at least one region of the optical element. That is, a temperature-controlling fluid may be used to bring the entire or partial volume of the optical element to a different temperature than before.

[0009] However, on the other hand, temperature control can also have the effect of maintaining a specific temperature or a specific temperature range for an optical element or at least one region of an optical element.

[0010] These considerations also generally apply to components having a corresponding substrate that supports or is capable of supporting one or more functional units, wherein the substrate incorporates a temperature-regulating hollow structure through which a temperature-regulating fluid can be flowed for temperature control during the operation of the component. Such a component could, for example, provide a sensor device, in which case the substrate supports the sensor unit as a functional unit.

[0011] Microlithography projection lithography systems are used in chip manufacturing to transfer structures from a mask onto a photoresist pre-coated on a wafer. For this purpose, the mask is illuminated with light and reduced in size to form an image on the photosensitive layer. In EUV projection lithography systems, the light has a wavelength of approximately 5 nm to 30 nm. Commercially available systems use light with a wavelength of 13.5 nm.

[0012] However, there are no optical materials that have sufficiently high transmittance for such short wavelengths. Therefore, in EUV projection lithography systems, the lens elements that have been commonly used for long wavelengths are replaced with mirrors, and the mask also includes a pattern of reflective structures.

[0013] Providing mirrors for EUV projection lithography systems is technically challenging. The substrate material is generally glass, such as quartz glass, titanium-doped quartz glass such as ULE®, or ceramic. Suitable glass-ceramic materials are available under trade names such as Clearceram® or Zerodur®, and have the characteristic of having a very small coefficient of thermal expansion at the mirror's operating temperature.

[0014] A coating consisting of multiple thin bilayers with alternating refractive indices that reflect EUV light is applied to the substrate.

[0015] However, even with such complex coating configurations, the reflectivity of the mirror to EUV light rarely exceeds 70%, and even then, only for light incident perpendicularly or at an angle of incidence of a few degrees. The portion of the EUV light not reflected by the coating is absorbed by the substrate, and since the EUV light source used is very high-power, this leads to considerable heating. Even when glass ceramics with a low coefficient of thermal expansion are used, heating can lead to unacceptable deformation of the mirror.

[0016] Therefore, it has been proposed to provide the substrate with a temperature-regulating hollow structure, which in this case is a cooling hollow structure, and in particular a temperature-regulating channel in the form of a cooling channel, through which water or some other temperature-regulating fluid, i.e., a cooling fluid, flows during operation to dissipate heat. Such a temperature-regulating channel is approximately 1 mm 2 It has a small cross-sectional diameter and, ideally, can extend directly beneath the reflective coating.

[0017] An outline of a conventionally known method for creating temperature control channels is described in Patent Document 1, and the entire disclosure thereof is incorporated herein by reference. Particularly promising is a method in which an ablation light beam is sequentially focused at the ablation location where a temperature control channel is to be created, and the substrate material is removed by the ablation light beam.

[0018] In this method, a modified substrate material, which is more sensitive to chemically active processing media than the unprocessed substrate material, is formed adjacent to the ablation site, that is, close to the focal point of the light beam rather than at its focal point. In particular, it is highly sensitive to etching. The modified substrate material forms the intermediate layer described at the beginning, and the material-free regions created by ablation form the intermediate hollow structure described at the beginning, thus forming a corresponding intermediate structure.

[0019] In this method, the modified substrate material is formed, in particular, by the absorption of a high-energy ablation light beam and the thermal diffusion of the resulting process heat from the ablation site. However, there is no clear indication of the extent of modified material formation before the substrate is processed. In the case of lasers, experts refer to the region containing the modified substrate material as the so-called laser-affected zone, or simply LAZ. The modified substrate material may differ from the substrate material in terms of density, thermal expansion coefficient, and existing material stress.

[0020] However, such materially non-uniform substrates are not suitable for use in EUV projection lithography equipment. Therefore, the modified substrate material must be removed. In known methods, the modified substrate material is etched off in a downstream process step, particularly using an etchant such as hydrofluoric acid (HF) or potassium hydroxide (KOH). Subsequently, the desired temperature-controlled hollow structure is formed. This means that, as a result, the modified substrate material defines the cross-section of the fabricated temperature-controlled hollow structure.

[0021] The overall process speed for forming the desired hollow structure for temperature adjustment is particularly limited by the removal speed. The substrate material is removed over substantially the entire cross-section of the desired hollow structure for temperature adjustment, and the modified substrate material is generally formed only with a small layer thickness. Furthermore, variations in material removal can occur due to, for example, regions with different refractive indices / transmittances or variations in the microstructure of the substrate material due to the formation of a thermal lens, which can further lead to undesired deviations in the cross-sectional shape of the hollow structure for temperature adjustment and roughness of the side surfaces.

Prior Art Documents

Patent Documents

[0022]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0023] An object of the present invention is, in view of these considerations, to identify methods, substrates, optical elements, and semiconductor technology devices of the above-mentioned type that can incorporate a hollow structure for temperature adjustment into a substrate, particularly with high precision, high quality, and a good process speed, and to enable the production of structured electronic components having particularly extremely small structures using such optical elements, and to provide such components.

Means for Solving the Problems

[0024] In the case of the method of the type described at the beginning, this object is achieved in step (B) by (B.1) sequentially focusing a modification light beam on a modification position to form a modified substrate material at the modification position, and (B.2) sequentially focusing an ablation light beam on an ablation position to remove material at the ablation position to produce an intermediate structure.

[0025] According to the present invention, it has been recognized that a temperature-regulating hollow structure with high-quality, uniform, and smooth surface properties can be incorporated into a substrate by combining the formation of a modified material as intended and the removal of the material as intended. With known methods, the modified substrate material is generated largely unpredictably, but according to the present invention, the modified substrate material is formed as intended using a modifying light beam. This makes it possible to plan the cross-sectional shape of the temperature-regulating hollow structure with high precision, in particular.

[0026] Further advantages of the present invention can be derived from the following features and further from the description of the present invention.

[0027] An advantage of this method is that it allows for the execution of either the first process route (P1) or the second process route (P2). In the case of the first process route (P1), step (B.1) is executed in the first process step (P1-S1), and step (B.2) is executed in the second process step (P1-S2). In the case of the second process route (P2), step (B.2) is executed in the first process step (P2-S1), and step (B.1) is executed in the second process step (P2-S2).

[0028] Therefore, the order of modification and removal can be carried out according to selection.

[0029] If the first process root (P1) is executed, In the first process step (P1-S1), a material structure including the modified substrate material is fabricated by step (B.1). In the second process step (P1-S2), the material is removed by step (B.2), creating an intermediate hollow structure and modifying the material structure, leaving the substrate material as an intermediate layer. This is advantageous.

[0030] Compared to known methods in which almost all substrate material is removed across the cross-section of the desired temperature-controlled hollow structure, here the volume is reduced only by the portion defined by the remaining modified substrate material. As a result, the time required for material removal is shortened.

[0031] Here, since step (B.1) can be performed in the first process step (PS-S1) of the first process route (P1) to produce either a first type of material structure or a second type of material structure, this method is advantageous in that it allows for two additional alternative procedures. In the case of the first type of material structure, the modified substrate material is formed to fill the cross-section, In the case of the second type of material structure, the modified substrate material is formed such that a core region of the substrate material remains, with at least a portion of the region surrounded by the modified substrate material.

[0032] Next, when step (B.2) is performed in the second process step (P1-S2) of the first process route (P1), the modified substrate material may be removed in the case of the first type of material structure, or the substrate material of the core region may be removed in the case of the second type of material structure, thereby creating an intermediate hollow structure, and an intermediate layer is formed by the modified substrate material of the remaining material structure.

[0033] If the second process root (P2) is executed, In the first process step (P2-S1), the substrate material of the substrate is removed in step (B.2), thereby creating an intermediate hollow structure. In the second process step (P2-P2), an intermediate structure is created by forming an intermediate layer from the modified material in step (B.1). This is advantageous.

[0034] Here too, less material is removed than with conventional technology, and consequently, the required time is shortened.

[0035] In the case of the second process step (P2-S2) of the second process route (P2), the intermediate hollow structure is preferably filled with an auxiliary fluid, and therefore, when step (B.1) is performed, it is filled with the auxiliary fluid. In this way, undesirable diffusion effects on the sides of the intermediate hollow structure can be reduced. In this case, it is preferable that the auxiliary fluid is held as a stationary fluid volume.

[0036] For this purpose, the refractive index n at the wavelength of the modifying light beam is preferably used. F The refractive index n of the substrate material at the same wavelength M With a tolerance of less than 20%, preferably less than 10%, preferably less than 5%, and particularly preferably less than 1%, the refractive index n of this substrate material is M It is an auxiliary fluid that matches [the specified value].

[0037] More preferably, a flushing fluid is applied to the ablation site during the execution of step (B.2) to wash away the material removed by the ablation light beam.

[0038] For the final formation of the temperature-regulating hollow structure, it is particularly advantageous in step (C) to flow the processing medium through the intermediate hollow structure at least at specific points in time, preferably continuously over time. For this purpose, the intermediate hollow structure is preferably fabricated to extend between two openings in the substrate.

[0039] Preferably, the chemically active processing medium is an etching medium, an oxidizing agent, or a reducing agent. Corrosive, oxidizing, or reducing actions may be combined. It is particularly preferable that the chemically active processing medium is an etching medium that removes the intermediate layer of the modified substrate material by an etching process in step (C).

[0040] In the case of the method for manufacturing optical elements, particularly mirrors for EUV projection exposure apparatus, as described at the beginning, a temperature-regulating hollow structure is incorporated into the substrate according to the method described above, and further processing includes one or more steps of chemically and / or physically treating at least one surface of the substrate, and forming or applying a coating to the substrate that is designed to reflect at least 50% of EUV light incident perpendicularly or substantially perpendicularly.

[0041] In the case of the type of substrate described at the beginning, the above objective is achieved by defining at least one temperature-regulating hollow structure on an inner side surface having an average roughness Ra of 10.0 μm to 5.0 μm in at least some areas, in particular 10.0 μm to 6.5 μm, 10.0 μm to 8.0 μm, 8.5 μm to 5.0 μm, 7.0 μm to 5.0 μm, or 8.5 μm to 6.5 μm, in accordance with DIN EN ISO25178 as of April 2023, or on an inner surface having an average roughness Ra of 5.0 or less in at least some areas, in particular 5.0 to 0.1 μm, preferably 4.5 μm to 0.125 μm, 4.0 μm to 0.15 μm, 3.5 μm to 0.175 μm, or 3.0 μm to 0.2 μm.

[0042] The above objectives can also be achieved by the type of substrate described at the beginning, wherein at least one temperature-regulating hollow structure defines an inner side having a surface topography with a geometric shape resulting from the overlap of recessed structures extending within the substrate material of the substrate in at least some areas.

[0043] Preferably, one or more submerged structures are themselves segments of an object that is point-symmetric or at least axis-symmetric.

[0044] The advantage of this method is that surface topography defines the peripheral regions, particularly linear peripheral regions, which are adjacent to each other and extend between them.

[0045] One or more settlement regions may be axially symmetric or not.

[0046] It is advantageous if the axially symmetric settlement region follows a part of the outer surface of a spherical segment, an ellipsoidal segment, or a paraboloid.

[0047] An advantage is that the temperature-regulating hollow structure is a temperature-regulating channel having one or more of the following characteristics: a) The temperature control channel has a diameter of 0.5 mm to 20 mm, preferably 1 mm to 5 mm. b) The temperature control channel shall have a length of 10 cm or more, 15 cm or more, or 20 cm or more. c) The temperature control channel is curved or has at least one curved section. d) The temperature control channel has a portion that follows the curvature of the support surface for coating the substrate. e) The temperature control channel has a strongly curved section with a curvature angle of 60° to 120°, particularly 80° to 100°, preferably about 90°. f) The temperature control channel has a strongly curved section with a curvature angle of 60° to 120°, particularly 80° to 100°, preferably about 90°, and is arc-shaped. g) The temperature control channel has a strongly curved section with a curvature angle of 60° to 120°, particularly 80° to 100°, preferably about 90°, forming an arc, and defining the outer radius of curvature R and diameter D, with the ratio of radius of curvature R to diameter D R / D being 2 to 6, preferably 2.5 to 5, particularly preferably 2.5 to 3.5. h) The temperature control channels are located at a distance of 1.0 mm to 50.0 mm, 1.0 mm to 20.0 mm, 1.0 mm to 10.0 mm, or 1.0 mm to 5.0 mm from the support surface for coating the substrate.

[0048] According to the present invention, in the case of the type of substrate described at the beginning that defines the support surface for coating, good flow characteristics can be ensured by keeping the change in the surface shape of the support surface to less than 100 pm, particularly less than 50 pm, and even more particularly less than 25 pm, over a substrate lifespan of up to 10 years, at least up to 5 years, and at least up to 2 years.

[0049] A synergistic advantage is that some or all of the above features can be combined and implemented on the substrate.

[0050] Preferably, the temperature-regulating hollow structure is incorporated into the substrate according to the method described above.

[0051] In the case of the type of optical element mentioned at the beginning, the above objective is achieved by a substrate having some or all of the above-mentioned features.

[0052] For substrate lifespans of up to 10 years, at least up to 5 years, and at least up to 2 years, it is advantageous for the change in the surface shape of the optical elements to be less than 100 pm, particularly less than 50 pm, and even more particularly less than 25 pm.

[0053] These properties are particularly advantageous in the case of mirrors in EUV projection lithography apparatuses, which have a support surface that supports a coating designed to reflect at least 50% of the EUV light incident perpendicularly or nearly perpendicularly on the substrate.

[0054] The properties of the optical elements mentioned can be combined advantageously.

[0055] In the case of semiconductor technology equipment, the objective is achieved by such optical elements.

[0056] This is particularly advantageous in the case of EUV projection lithography systems.

[0057] In the case of structured electronic devices, the above-mentioned objectives are achieved by manufacturing them using such semiconductor technology equipment.

[0058] Exemplary embodiments of the present invention will be described in more detail below with reference to the drawings. [Brief explanation of the drawing]

[0059] [Figure 1] A schematic cross-section of a mirror-type optical element in an EUV projection exposure apparatus is shown, which has a temperature-regulating hollow structure in the form of a temperature-regulating channel through which a cooling fluid flows via a cooling system. [Figure 2]This invention describes a modification process system that forms a modified substrate material at a modification location and incorporates the material structure of the modified substrate material into a substrate by following a first process route that includes sequentially focusing a modification light beam at the modification location. [Figure 3A] Figure 2 shows a magnified view of detail IIIA, which incorporates the first type of material structure that fills the cross-section. [Figure 3B] The cross-section is shown along the cutting line IIIB-IIIB in Figure 3A. [Figure 4] This shows a substrate having a first type of incorporated material structure. [Figure 5A] A magnified view of the detailed VA in Figure 4 is shown. [Figure 5B] A magnified view of the VB details in Figure 4 is shown. [Figure 6A] This shows a detail corresponding to the detail shown in Figure 3A, incorporating a second type of material structure in which the core region of the substrate material remains within the cross-section. [Figure 6B] Figure 6A shows a cross-section following the cutting line VIB-VIB. [Figure 7] Details corresponding to the details shown in Figures 5A and 5B, which have the second type of material structure, are shown. [Figure 8] This invention illustrates an ablation processing system that removes material at ablation locations by sequentially focusing an ablation light beam onto the ablation locations on the substrate, thereby creating an intermediate hollow structure within the material structure from the modified substrate material. [Figure 9A] Figure 8 shows a magnified view of the detailed IXA. [Figure 9B] Figure 9A shows a cross-section following the cutting line IXB-IXB. [Figure 10] This shows a substrate with an integrated intermediate structure. [Figure 11A] A magnified view of the detailed XIA in Figure 10 is shown. [Figure 11B] A magnified view of the detail XIB in Figure 10 is shown. [Figure 12] Figure 8 shows an ablation processing system for creating an intermediate hollow structure on a substrate material by following the second process route. [Figure 13A]A magnified view of detail XIIIA shown in Figure 12 is provided. [Figure 13B] Figure 13A shows a cross-section following the cutting line XIIIB-XIIIB. [Figure 14] This shows a substrate incorporating an intermediate hollow structure. [Figure 15A] A magnified view of the detailed XVA in Figure 14 is shown. [Figure 15B] A magnified view of the XVB detail in Figure 14 is shown. [Figure 16] Figure 2 shows an improved version of the modification treatment system, which includes a device for introducing an auxiliary fluid into an intermediate hollow structure. [Figure 17A] A magnified view of detail XVIIA in Figure 16 is shown. [Figure 17B] Figure 17A shows a cross-section following the cutting line XVIIB-XVIIB. [Figure 18] This invention illustrates an etching system that allows the etching medium to be introduced into the intermediate hollow structure of the intermediate structure. [Figure 19A] A magnified view of detail XIXA in Figure 18 is shown. [Figure 19B] A magnified view of detail XIXB in Figure 18 is shown. [Figure 20A] This shows the details corresponding to Figure 19A after the etching process is complete. [Figure 20B] Figure 19B shows the details corresponding to the etching process after completion. [Figure 21] This diagram illustrates the possibility of correcting the irregularities in the intermediate hollow structure. [Figure 22] This shows a substrate for an EUV mirror incorporating a temperature-regulating hollow structure by following a first or second process route. [Figure 23A] This shows a topographic image of the surface region of a hollow structure used for temperature control. [Figure 23B] A cross-section is shown to illustrate the average roughness Ra achieved. [Figure 24] A schematic cross-section of the hollow structure for temperature control is shown. [Figure 25] A magnified view of detail XXV in Figure 22 is shown. [Figure 26A]This image shows the surface shape of a substrate with an intermediate structure before the etching process. [Figure 26B] This image shows the surface shape of the substrate having a temperature-regulating hollow structure obtained after the etching process. [Figure 26C] The difference between the images shown in Figures 26A and 26B is represented. [Figure 27] A schematic diagram of semiconductor technology equipment based on an example of an EUV projection lithography system is provided. [Modes for carrying out the invention]

[0060] 1. Configuration of optical elements based on the example of an EUV mirror Figure 1 comprehensively shows the semiconductor technology equipment described at the beginning as 6, and shows a cross-section of the optical element as a whole as 8, with this optical element shown as a mirror 10 for an EUV projection lithography apparatus as an example. The mirror 10 may be placed in the illumination system or projection lens.

[0061] The optical element 8, and therefore the mirror 10, includes a substrate 12 made of substrate material 12a, which in this exemplary embodiment of the mirror 10 is the mirror substrate. In practice, such a mirror substrate is particularly titanium-doped quartz glass.

[0062] In this exemplary embodiment, which is also a preferred embodiment, the substrate 12 is monolithic. However, in modified forms not separately illustrated, the substrate 12 may be joined from partial segments. In principle, additive manufacturing methods are suitable in this case. For example, 3D printing methods are considered, as are laser welding methods or techniques for thermal bonding of workpieces.

[0063] In the case of the mirror 10, the substrate 12 has a precisely machined surface 14, the curvature of which determines the optical properties of the mirror 10. The surface 14 of the substrate 12 acts as a support surface, and will be referred to as such hereafter. The support surface 14 supports a coating 16 that provides the optical properties of the optical element 8 in particular. In the case of the mirror 10 shown herein, the coating 16 is designed to primarily reflect incident EUV light 18. As shown in enlarged detail figure A, in this exemplary embodiment, the coating 16 is in a multilayer form and, in particular, consists of a plurality of double layers 20 applied to the support surface 14. The coating 16 has a reflectance coefficient of 50% or more, preferably 70% or more, with respect to perpendicularly incident EUV light 18. The reflectance achieved during operation depends on the angle of incidence of the EUV light 18.

[0064] In addition to the double layers 20, the coating 16 may include further layers that do not contribute to reflection but may contribute to the stabilization and / or protection of the coating 16 or the optical element 8 or the mirror 10. For example, this can provide protection from components of hydrogen plasma. Such further layers may be provided between the double layers 20 within the coating 16, between the double layers 20 and the support surface 14, and / or on the side of the double layers 20 furthest from the support surface 14.

[0065] In the case of the optical element 8, the coating 16 can also be formed by modifying the outer surface of the substrate 12 through processing and / or treatment. Therefore, in this case, the coating 16 is not a separately applied coating, but rather defines a layer of the substrate 12 itself. The surface below it, which is the transition area to the substrate material 12a, is the support surface 14.

[0066] In the case of applying the mirror 10 and EUV light 18 as described here, the unreflected portion enters the substrate 12 and is absorbed there, specifically mainly near the support surface 14. Due to this absorption, the substrate 12 is heated mainly near the region of the support surface 14 exposed to the EUV light 18. The thermal expansion coefficient of the substrate material 12a is not equal to zero, and in addition, it is temperature-dependent, so heating can cause a change in the shape of the substrate 12 and affect the optical properties of the mirror 10. Generally speaking with respect to the optical element 8, temperature changes in the substrate 12 can affect the optical properties of the optical element 8.

[0067] However, due to the extremely stringent specifications of the EUV projection exposure system, any changes in the optical properties of the mirror are either unacceptable or only minimally acceptable. Nevertheless, generally speaking, in the case of optical elements 8, the intention is for the optical properties to remain stable, and in the case of components, the intention is for the functionality to be maintained.

[0068] Multiple temperature-regulating hollow structures 22 are incorporated into the substrate 12 to minimize temperature fluctuations of the substrate material 12a and the resulting changes in the shape of the substrate 12.

[0069] During operation of the EUV projection lithography apparatus, a temperature-regulating fluid in the form of a cooling fluid 24 flows through these temperature-regulating hollow structures 22, and in practice, cooling water is used. However, other cooling fluids and cooling media are also possible.

[0070] The cooling fluid 24 absorbs the heat input from the EUV light 18 and dissipates it from the substrate 12. For this purpose, the temperature-regulating hollow structure 22 is connected to the cooling unit 26 and pump unit 28 of the cooling system shown as 30. The pump unit 28 draws the cooling fluid 24 from the temperature-regulating hollow structure 22 and sends it to the cooling unit 26 via the return line 32. There, the cooling fluid 24 is cooled to its target temperature and then flows through the temperature-regulating hollow structure 22 again. This circuit is shown by the arrow corresponding to Figure 1.

[0071] The temperature-regulating hollow structure 22 typically extends in the vicinity of the support surface 14, with at least a portion of its area extending parallel to it.

[0072] In the exemplary embodiment described herein, the temperature-regulating hollow structure 22 is formed as a temperature-regulating channel 34, of which three temperature-regulating channels 34.1, 34.2, and 34.3 are illustrated. Each temperature-regulating channel 34 extends between two openings 36, which are shown only in Figure 1 for temperature-regulating channel 34.1, and each temperature-regulating channel 34 is connected to the cooling unit 26 and the pump unit 28 through its openings 36. Thus, depending on the allocation, each opening 36 defines an inlet or outlet for the temperature-regulating channel 34 for the cooling fluid 24. The cross-section of the temperature-regulating channel 34 is not constant and may be, for example, circular, elliptical, rectangular, or annular. The cross-section and shape of the temperature-regulating hollow structure 22 may differ depending on the position on the substrate 12. In this exemplary embodiment, the openings 36 of the temperature-regulating channel 34 are located on the back side 38 of the substrate 12 opposite to the support surface 14.

[0073] In modified configurations not shown separately, the temperature-regulating hollow structure 22 may also be a wider chamber in which the cooling fluid 24 is exchanged slowly and a specific longitudinal axis is not defined for the flow path.

[0074] Furthermore, the arrangement of the temperature control channels 34 shown in the illustration is merely an example and may differ in an actual system. The number of temperature control channels 34 may also be increased or decreased. For example, the opening 36 may be located on the side of the substrate 12, or at least one temperature control channel 34 extending in a meandering or spiral manner within or in part of the substrate 12 may be provided.

[0075] In yet another modification, one or more temperature-regulating channels 34 may extend from a distribution section or distribution chamber within the substrate 12. Such temperature-regulating channels 34 have openings at one or both ends that connect to such a distribution section or distribution chamber, from which temperature-regulating fluid is supplied to the channels 34. The distribution section or distribution chamber, and possibly the far end of the temperature-regulating channel 34, are correspondingly connected to the cooling system 30.

[0076] The temperature control channels 34, in particular the temperature control channels 34.1, will be referred to below in all exemplary embodiments as representative of all types and arrangements of temperature control hollow structures 22.

[0077] During the manufacturing of the optical element 8 by applying the method described herein to create a temperature-regulating hollow structure 22, various stages of the substrate 12 are defined.

[0078] The first stage of the substrate 12 defines a kind of raw substrate 12', which is mostly unprocessed and untreated, in which case the support surface 14 has not yet been structurally formed. In the case of the above-mentioned substrate 12, which is a mirror substrate, such a raw substrate is, for example, a parallelepiped of glass made of titanium-doped quartz glass.

[0079] The second stage of the substrate 12 defines the support substrate 12'', in which case the support surface 14 is fabricated and formed. This may require several chemical and / or physical work steps, which may include operations such as grinding, turning, polishing, and / or etching.

[0080] The third stage of the substrate 12 defines the element substrate 12''', in which case at least a coating 16 determining the optical properties is provided on the support surface 14. If the resulting optical element is a mirror, the element substrate 12''' is consequently a mirror substrate in terms of terminology. Therefore, since the substrate 12 in Figure 1 represents the element substrate stage, it also has reference numeral 12'''. As mentioned at the beginning, if the substrate 12 is, for example, part of a sensor device, the element substrate 12''' is consequently a sensor substrate in terms of terminology.

[0081] The fabrication of the temperature-regulating hollow structure 22 on the substrate 12, as described below, can, in principle, be carried out at any stage of the substrate 12. This is generally done at the stage of the unprocessed substrate 12', but it may also be done at the stage of the support substrate 12'', or even at the stage of the element substrate 12'''.

[0082] In this exemplary embodiment, in order to illustrate the function assumed in this exemplary embodiment for the mirror 10 obtained later, the fabrication of the temperature-regulating hollow structure 22 will be described in particular based on the example of the support substrate 12''.

[0083] 2. Fabrication of a temperature-regulating hollow structure based on an example of a temperature-regulating flow path. Figures 2 to 9 show a first process route P1 in which an intermediate structure 40, as shown in Figures 10 and 11, can be incorporated into the substrate 12, which includes an intermediate layer 42 of a modified substrate material 44 and an intermediate hollow structure 46 in which at least a portion of the area is surrounded by the intermediate layer 42.

[0084] The modified substrate material 44 is more sensitive to chemically active processing media than the substrate material 12a and can be removed in downstream processes, thereby completing the desired temperature-regulating hollow structure 22, or in this case, the temperature-regulating channel 34, from the intermediate structure 40. This will be explained further below.

[0085] Figures 12 to 17 show a second process route P2 in which the intermediate structure 40 can be incorporated into the substrate 12.

[0086] In the exemplary embodiment described below, the intermediate hollow structure 46 extends between two openings in the substrate located at the locations of the openings 36 for the temperature control channel 34.

[0087] 2.1 First process route P1 for intermediate structure 40 First, Figure 2 shows the substrate 12 as an unprocessed substrate 12' with a dashed outline, and as a support substrate 12'' before the application of the reflective coating 16, i.e., as a substrate 12 with the support surface 14 already formed, with a solid line.

[0088] Furthermore, the detailed enlarged view shows only the substrate 12. The outer contour of the unprocessed substrate 12' is shown partially, only at the edges, where necessary. Even in the unprocessed substrate 12, the path of the final support surface 14 is already determined, and this assumed support surface 14 acts as a reference surface that defines the path of the temperature-regulating hollow structure 22 on the substrate 12.

[0089] Figure 2 shows the modification processing system 48 of the higher-level processing apparatus indicated by 50. Using the modification processing system 48, the material structure 52 of the modified substrate material 44 can be incorporated into the substrate 12 in the first process step P1-S1 of the first process route P1. There are two options, and a first type of material structure 52 or a second type of material structure 52, designated 52-I and 52-II respectively, can be manufactured.

[0090] The modification system 48 includes a light source 54 that generates a modification light beam 56. The light source 54 is preferably a high-power laser that generates short pulses or ultrashort pulses. These may be pulses in the femtosecond, picosecond, or nanosecond range.

[0091] The modification light beam 56 can be directed to different locations on the substrate 12 by a focusing device 58, which includes a scanning device 60 and a focusing lens element 62. The relative positioning of the substrate 12 and the modification system 48 can also be changed using a positioning table (not shown) so that the processing light beam 56 can be directed to any position on the substrate 12 after passing through the focusing lens element 62. In this case, the scanning device 60, the focusing lens element 62, and the positioning table, if present, are controlled by a control device 64 so that the processing light beam 56 is sequentially focused to all of the modification locations 66 on the substrate 12 where the temperature control channel 34 is intended to be generated. Alternatively, the relative positioning of the substrate 12 and the modification system 48 can be changed by positioning the modification system 50. For small substrates 12, the positioning operation can be omitted if the scanning device 60 covers a sufficiently large area.

[0092] At the focal point generated by the focusing lens element 62, the intensity of the modifying light beam 56 is very high, so the material of the substrate 12 is modified as intended, especially by the absorption of the high-energy modifying light beam 56, with virtually no material loss. This modification can be understood as targeted damage to the substrate material 12a, which embrittles the material and increases its susceptibility to chemically active processing media. In this exemplary embodiment, the modification increases susceptibility to etching. In this case, the region in which the modifying light beam 56 modifies the substrate material 12a defines each modified position 66 that moves naturally with the focal point of the modifying light beam 56.

[0093] The focal point, and therefore the modification location 66, determines the location, geometric shape, and cross-section of the temperature-regulating channel 34 that will later be fabricated in the substrate. To fabricate a temperature-regulating channel 34 with a sufficiently large cross-section, at specific axial positions, the processing light beam 56 travels radially along the entire cross-section in a predetermined pattern. This process is repeated at adjacent axial positions until the material structure 52 of the modified substrate material 44 has the desired axial dimensions.

[0094] Figures 2 and 3 first show how the first type 52-I material structure 52 is incorporated here, and Figures 4 and 5 show these after completion. Regardless of whether they are first or second type, the resulting material structure 52 reflects the path of the final temperature control channel 34 within the substrate 12 and the cross-section in the direction of that path, correspondingly having reference numerals 52.1, 52.2, and 52.3 in Figure 4.

[0095] In Figures 2 and 3, we can see a portion 52a of the material structure 52 of type 1 52-I that is already incorporated into the substrate 12 and follows the path of the final temperature control channel 34.1.

[0096] Figure 3B shows, based on the cross-section of portion 52a, that in the case of the final material structure 52 of type 1 52-I, a modified substrate material 44 without a hollow structure is intended to be present in the cross-section, and is actually present; that is, in the case of these material structures 52 of type 1 52-I, the modified substrate material 44 is formed to fill the cross-section. This does not rule out the possibility that the modified substrate material 44 may be porous, for example.

[0097] As a result, the substrate 12 shown in Figure 4, into which the material structure 52 of the modified substrate material 44 is incorporated, is thus obtained using the modification treatment system 48. Figure 5 shows the continuous path of the first type 52-I material structure 52 within the substrate 12, again based on the detailed VA and VB shown in Figure 4, including the material structure 52.1.

[0098] Figure 6, as an alternative, shows how the second type 52-II material structure 52 is incorporated into the substrate 12, specifically based on an example of a material structure 52.1 that follows the path of the final temperature control channel 34.1. Figure 6 again shows a portion 52a of the material structure 52 that has already been created in the substrate 12. As can be seen in Figure 6B based on a cross-section of this portion 52a, in the case of the second type 52-II material structure 52, the modified substrate material 44 is formed such that a core region of the substrate material 12a remains, surrounded by the modified substrate material 44 in at least a portion of the area.

[0099] In the exemplary embodiment shown herein, the material structure 52 of type 2 52-II has an annular cross-section. Figure 7 shows the completed material structure based on the same details as seen in material structure 52.1 and Figure 5.

[0100] Hereafter, the text will generally refer to material structure 52 only, and will refer to type 1 52-I or type 2 52-II individually only when there are differences.

[0101] In the second process step P1-S2 of the first process route P1, the aforementioned intermediate hollow structure 46 is subsequently incorporated into the material structure 52 of the modified substrate material 44, thereby generating the entire intermediate structure 40.

[0102] For this purpose, the processing apparatus 50 includes an ablation system 68 as shown in Figure 8, the ablation system 68 containing largely the same components as the modification system 48, and these components also have corresponding reference numerals. In principle, what has been said about these components applies correspondingly and similarly.

[0103] In contrast to the modification treatment system 48, the light source 54 of the ablation processing system 68 generates an ablation light beam 70, and it is preferable that this light source is also a high-power laser that generates ultrashort pulses.

[0104] In the case of the ablation light beam 70, the intensity at the focal point formed by the focusing lens element 62 is very high, so the ablation position 72 is defined there, and the material present is removed. The position of the focal point, and therefore the ablation position 72, determines the location, geometric shape, and cross-section of the intermediate hollow structure 46 that is generated in the modified substrate material 44.

[0105] In Figures 8 and 9, it can be seen that the portion 46a of the intermediate hollow structure 46 already incorporated into the material structure 52.1 and the portion 40a of the intermediate structure 40 already incorporated into the substrate 12 follow the path of the material structure 52.1, and therefore the path of the final temperature control channel 34.1. In correspondence with this, the portion 42a of the fabricated intermediate layer 42 is also formed.

[0106] Since the cross-sections of the intermediate hollow structures 46 along the paths of the material structures 52 are smaller than the cross-sections of each material structure 52, an intermediate structure 40 is generated in which each intermediate hollow structure 46 is surrounded by an intermediate layer 42 of the modified substrate material 44. In this exemplary embodiment, the intermediate hollow structure 46 is an intermediate hollow channel surrounded by an outer covering of the modified substrate material 44. Figure 7B shows this based on the cross-sections of portions 40a / 42a / 46a, but also reflects the cross-section of the completed intermediate structure 40.

[0107] If a material structure 52 of type 1 51-I is present, the modified substrate material 44 is removed at the ablation position 72. If a material structure 52 of type 2 52-II is present, the substrate material 12a of the substrate 12 is removed at the ablation position 72. In this case, the core region shown by the dashed line to the right of the processing light beam 70 in Figure 9A still consists of the substrate material 12a.

[0108] The ablation system 68 also includes a flushing device, shown as 74, which is also controlled by a control device 64. The flushing device 74 applies a flushing fluid 76 to the ablation position 72 during the removal of the modified substrate material 44, so that the removed material is washed away by the flushing fluid 76. For this purpose, a flushing line 78 is provided, which is inserted into sections 40a / 46a, and is supplied with the flushing fluid 76 by a pump (not shown). The discharge end of the flushing line 78 can be made to follow the ablation position 72 by a line conveyor (also not shown), which pushes the flushing line 78 forward as sections 40a / 46a are formed. The removed material is carried away by the flushing fluid 76 and flows out through the already formed sections 40a / 46a, as indicated by the arrows corresponding to Figure 9A.

[0109] As a result, the substrate 12 shown in Figures 10 and 11 is obtained in this way using the ablation system 68 as an intermediate substrate incorporating intermediate structures 40 from both the first type 52-I and the second type 52-II material structures 52. Figure 11 shows the continuous path of the intermediate structures 40 within the substrate 12, again based on the details XIA and XIB shown in Figure 10, and these intermediate structures 40 are further shown in 40.1, 40.2, and 40.3, corresponding to the final temperature control channel 34.

[0110] In summary, generally speaking, in the first process route P1 in the first process steps P1-S1, a material structure 52 including the modified substrate material 44 is fabricated on the substrate material 12a of the substrate 12, and in the second process steps P1-S2, an intermediate hollow structure 46 is fabricated and the material is removed so that the modified substrate material 44 remains as an intermediate layer 42, thereby generating an intermediate structure 40. In the second process steps P1-S2, in the case of the first type 52-1 material structure 52, the modified substrate material 44 is removed, or in the case of the second type 52-II material structure 52, the substrate material 12a of the core region is removed, an intermediate hollow structure 46 is fabricated and the intermediate layer 42 is formed from the modified substrate material 44 of the remaining material structure 52.

[0111] 2.2 Second process route P2 for intermediate structure 40 On the other hand, in the case of the alternative second process route P2, the intermediate hollow structure 46 is removed in the second process step P2-S1 by correspondingly removing the substrate material 12a of the substrate 12, and in the second process step P2-S2, an intermediate layer 42 of the modified substrate material 44 is formed, thereby generating an intermediate structure 40.

[0112] Figure 12 shows that the ablation system 68 is used in the first process step P2-S1 of the second process route P2. Identical components again have the same reference numerals.

[0113] In the case of the ablation light beam 70, the intensity at the focal point formed by the focusing lens element 62 is very high, so the substrate material 12a of the substrate 12 is removed at the ablation position 72. Here again, the focal position, and therefore the ablation position 72, determines the location, geometric shape, and cross-section of the intermediate hollow structure 46 that is fabricated, but this time in the substrate material 12a of the substrate 12.

[0114] In Figures 13A and 13B, the geometric shape and cross-section of the temperature-regulating hollow structure 22, particularly the temperature-regulating channel 34.1, which is intended to be present in the completed mirror 10, are shown by dashed lines 80. As can be seen, the cross-section of the intermediate hollow structure 46 along the planned path 80 of the temperature-regulating channel 34 is smaller than those cross-sections.

[0115] In Figures 12 and 13, a portion of the intermediate hollow structure 46 already incorporated into the substrate material 12a can be seen. This portion also has reference numeral 46a in this case and follows the path 80 of the final temperature control channel 34.1.

[0116] Figures 14 and 15 show the first step P2-S1 of the second process route P2 in which the intermediate hollow structure 46 is incorporated into the substrate 12. The intermediate hollow structure 46 reflects the path of the final temperature control channel 34 in the substrate 12 and its cross-sectional view, and is correspondingly designated as reference numerals 46.1, 46.2, and 46.3 in Figure 14.

[0117] In the second process step P2-S1 of the second process route P2, an intermediate structure 40 is fabricated by forming an intermediate layer 42 of the substrate material 12a surrounding the intermediate hollow structure 46, thereby generating the intermediate structure 40 as a whole.

[0118] As shown in Figure 16, an improved modification system 82 is used for this purpose, which largely corresponds to the modification system 48 shown in Figure 2, with the same components having the same reference numerals.

[0119] Figures 16 and 17 show a portion 42a of the intermediate layer 42 of the modified substrate material 44 already incorporated into the material substrate 12a, and correspondingly a portion 40a of the associated intermediate structure 40 is formed, which defines the final temperature control channel 34.1 and is therefore indicated as 40.1.

[0120] The sides of the intermediate hollow structure 46 fabricated by the ablation system 68 have a surface roughness that can exceed 1 μm. Therefore, the modifying light beam 56 is scattered on these sides, which adversely affects the formation of the intermediate layer 42. In particular, in the worst case, the modifying light beam 56 may not be able to reach the region of the substrate material 12a located on the side of the existing intermediate hollow structure 46 that is farther from the focusing lens element 62.

[0121] This scattering effect can be prevented or sufficiently reduced by the auxiliary fluid 84. The auxiliary fluid 84 is preferably transparent to the modifying light beam 56, and more preferably has the same refractive index n as, or at least similar to, the substrate material 12a of the substrate 12. Preferably, in this case, the refractive index n of the auxiliary fluid 84 at the wavelength of the modifying light beam 56 is... F The refractive index n of substrate material 12a at the same wavelength M With a tolerance of less than 20%, preferably less than 10%, preferably less than 5%, and particularly preferably less than 1%, the refractive index n of the substrate material 12a. M This matches. For example, glycerin and water are suitable as auxiliary fluids 84.

[0122] For this purpose, the modification system 82 further includes a fluid device 86 which can be used to fill the already formed intermediate hollow structure 46 with an auxiliary fluid 84. In this case, the fluid device 86 is preferably designed to be held within the hollow structure as a stationary fluid volume in order to avoid undesirable effects caused by turbulence of the auxiliary fluid 84. The pump shown in the case of the fluid device 86 is used only for filling or discharging the hollow structure, but not for circulating the auxiliary fluid 84.

[0123] Refractive index n of auxiliary fluid 84 FDepending on the circumstances, a shift in focus may occur, and therefore a shift in the modification position 66 relative to the focus or modification position to which the modification light beam 56 reaches in the absence of the auxiliary fluid 84. This is particularly important for the modification position 66 which is intended to reach the side of the already existing intermediate hollow structure 40 that is farther from the focusing lens element 62, and for that purpose the light must pass through the intermediate hollow structure 40.

[0124] The control device 64 takes into account this shift effect on the focal point of the modifying light beam 56, so that the modified substrate material 44 is formed in the desired region.

[0125] As a result, the intermediate substrate 12 shown in Figures 8 and 9, in which the intermediate structure 40 is incorporated, is obtained in this way using the modification treatment system 82.

[0126] In summary, in this second process route P2, the intermediate hollow structure 46 is incorporated into the substrate material 12a of the substrate 12 in the first process step P2-S1, and the intermediate layer 42 of the modified substrate material 44 is incorporated into the substrate material 12a of the substrate 12 in the second process step P2-S2, thereby generating the intermediate structure 40.

[0127] 2.3 Application of Process Routes P1 and P2 The two process routes P1 and P2 described above can both be applied to the same substrate 12. Depending on the respective geometric shapes and paths of the different temperature-regulating hollow structures 22, one or the other process route P1 or P2 may be more advantageous for application to different temperature-regulating hollow structures 22. Different options of process route P1 or P2 can also be applied independently to the exact same substrate 12.

[0128] 2.4 Completion of the temperature control channel As described above, the intermediate layer 42 of the modified substrate material 44 is subsequently removed by a chemically active processing medium.

[0129] This is shown in Figure 18, in which the intermediate substrate 12 shown in Figures 10 and 11 can be seen. In the etching step, a chemically active processing medium 90 is introduced into the intermediate hollow structure 46 of the intermediate structure 40 using the processing apparatus 88, thereby removing the intermediate layer 42 of the modified substrate material 44.

[0130] In this case, it is preferable that the processing medium 90 flows continuously through the intermediate hollow structure 46 over time. In a modified form, the processing medium 90 may flow through the intermediate hollow structure 46 only at specific points in time and remain stationary within the intermediate hollow structure 40 for a predetermined period of time. Each intermediate layer 42 and intermediate hollow structure 46 is indicated by a reference numeral only in the case of intermediate structure 40.1.

[0131] In this exemplary embodiment, the chemically active processing medium 90 is an etching medium 90', and the intermediate layer 42 of the modified substrate material 44 is removed by the etching process. The processing apparatus 88 is, in this case, an etching apparatus. Alternatively, the processing medium 90 may be an oxidizing agent or a reducing agent, which may include the processing medium 90 containing an oxidizing agent or a reducing agent.

[0132] Alkalis and acids are considered as etching agents. In the case of alkalis, this is especially true for strong alkalis such as potassium hydroxide (KOH). Strong acids may also be used, but in the case of acids, hydrofluoric acid (HF), which is a weak acid but highly reactive, is particularly used. The concentration of alkali or acid in the etching medium 90' is adjusted in this case to suit the required etching effect.

[0133] Alternatively, ammonium fluoride buffer NH4F / H2O / HF may be used, or CF4 may be used for dry etching.

[0134] The processing apparatus 88 includes a reservoir 92 filled with a processing medium 90, in this case an etching medium 90', and a pump 94, the pump 94 of which can be connected to the open end of an intermediate structure 40 through which the medium flows. Figure 18 shows this in the case of an intermediate structure 40.1.

[0135] The other open end of the intermediate structure 40 through which the medium flows is connected to a recovery container 96 for the processing medium 88. In some cases, the etching medium 90' can also pass through the intermediate structure 40 in multiple cycles by a circulation system 98 schematically shown by dashed lines. This generally also applies to the processing medium 90.

[0136] Figures 19 and 20 show, based on details XIXA and XIXB of Figure 18, that the intermediate layer 42 in the case of the intermediate structure 40.1 in Figure 19 is thinner than the initial state shown in Figure 11, and is further removed or etched by the processing medium 90 or etching medium 90' before the temperature control channel 34.1 shown in Figure 20 is completed.

[0137] Such treatment or etching of the intermediate layer 42 is performed for all existing intermediate structures 40 until the substrate 12 of the mirror 10 having the temperature-regulating hollow structure 22 shown in Figure 1 is obtained, but the coating 16 has not yet been applied to the support surface 14 on this substrate 12.

[0138] Since the etching medium 90' flows through the already existing intermediate hollow structure 46, which is accessible from the outside at both ends, a uniform action or etching action is ensured on the modified substrate material 44 of the intermediate layer 42 without any stagnation effect in the dead volume. In this case, the processing medium 90 or etching medium 90' behaves like laminar flow, and no blind spots are created.

[0139] Furthermore, for simplicity, the etching step in etching medium 90' will be referred to as a processing step. What has been stated in this regard applies similarly to the processing step in alternative chemically active processing medium 90.

[0140] Correction of unevenness Figure 21 illustrates, as an example, the possibility of compensating for irregularities that may occur when the intermediate hollow structure 46 is incorporated into the material structure 52 of the modified substrate material 44 or directly into the substrate material 12a, using two process routes P1 and P2 combined with a subsequent etching step.

[0141] Figures 21A and 21B show details IXA of Figure 8 and details XIIIA of Figure 12, respectively, illustrating how the modified substrate material 44 of type 52-I material structure 52.1 in the case of the first process route P1 and the substrate material 12a in the case of the second process route P2 are removed by the ablation light beam 70. Irregularities in the form of offset points 100 occur in the intermediate hollow structure 46.1 in both cases. Such irregularities can occur if there are interruptions in the removal process or if there are variations in the microstructure of the material structure 52 of the substrate 12.

[0142] As a result, the intermediate substrate 12 shown in Figure 10 has such an offset point 100 on the formed intermediate structure 40 shown in Figure 21C based on the intermediate structure 40.1.

[0143] As long as such offset points 100 still exist within the outer boundary of the fabricated temperature control channel 34 in the radial direction, the offset points 100 can be compensated by the etching step.

[0144] As shown in Figure 21A, this applies when, in the first process route P1, in the first process step P1-S1, the material structure 52.1 is incorporated in a sufficiently large cross-section such that it remains surrounded by the modified substrate material 44 even at the radially outer offset point 100.

[0145] Figure 21B shows that this is true in the second process route P2, where in the first process step P2-S1, the intermediate hollow structure 46.1 with an offset point 100 is still fabricated within the planned geometric shape 80 of the temperature control channel 34.1. In the second process step P2-S2 of the second process route P2, the intermediate layer 42 is formed with a uniform cross-section so that even the radially outward offset point 100 is surrounded by the modified substrate material 44.

[0146] In both process routes P1 and P2, an intermediate structure 40 is fabricated in which the intermediate hollow structure 46 has a corresponding offset point 100. This is shown again in Figure 19D.

[0147] When the etching step is performed, the etching selectivity of the etching medium 90' is sufficient to etch away the thick and thin regions of the intermediate layer 42 without excessively affecting the surrounding substrate material 12a. Once the thin regions of the intermediate layer 42 are etched away, the etching medium 90' can have already flowed over the substrate material 12a and acted upon them before the removal of the thick regions. However, the time required for the remaining intermediate layer 42 to be removed by the etching medium 90' is not enough to cause unacceptable damage to the substrate material 12 that has already been flowed over.

[0148] As a result, even when there is an offset point 100 on the side of the intermediate hollow structure 46, a functionally superior related temperature-regulating hollow structure 22 is fabricated by the etching step, which is shown in Figure 21.

[0149] 3. Obtained substrate Figure 22 again shows the substrate 12 at the stage of the support substrate 12'' having the temperature-regulating hollow structure 22, the temperature-regulating hollow structure 22 obtained by the method described above, and in this case again, it is represented by three temperature-regulating channels 34.1, 34.2 and 34.3 as an example. The temperature-regulating hollow structure 22 has defined inner side edges 102, and a reference numeral is given on one of the inner side surfaces 102 for clarity.

[0150] The characteristics of the temperature-regulating hollow structure 22 or the temperature-regulating flow path 34 and the substrate 12 itself, which can be made possible or obtained by applying the above method, will be described below, and in some cases, already described characteristics will be revisited and / or supplemented.

[0151] 3.1 Hollow structure for temperature adjustment / flow path for temperature adjustment As an effect of applying the first or second process routes P1 and P2 to form the temperature-regulating hollow structure 22, a substrate 12 is obtained having an inner side surface 102 having an average roughness Ra of 10.0 μm to 5.0 μm with very high quality in at least some areas, in particular 10.0 μm to 6.5 μm, 10.0 μm to 8.0 μm, 8.5 μm to 5.0 μm, 7.0 μm to 5.0 μm, or 8.5 μm to 6.5 μm, or an inner surface 102 having an average roughness Ra of 5.0 or less with very high quality in at least some areas, in particular 5.0 to 0.1 μm, preferably 4.5 μm to 0.125 μm, 4.0 μm to 0.15 μm, 3.5 μm to 0.175 μm, or 3.0 μm to 0.2 μm. In practice, it is possible to achieve particularly good average roughness Ra in the ranges of 0.1 μm to 0.5 μm, 0.15 μm to 0.45 μm, 0.2 μm to 0.4 μm, and 0.25 to 0.35 μm. However, in principle, an average roughness Ra of 10.0 μm to 5.0 μm is also a good result.

[0152] Figure 23A shows a topographic image of the surface region 104 of the inner side surface 102 of such a temperature-regulating hollow structure 22, and Figure 23B shows a cross-section along the cutting line indicated by 106 in Figure 23A, showing that the average roughness Ra achieved there is approximately 0.28 μm. The surface region 104 has an area of ​​254 μm × 190 μm.

[0153] The average roughness Ra is measured and specified according to DIN EN ISO 25178 (as of April 2023). The measurement was performed using a white light interferometer with a magnification of 50x, as is known.

[0154] Figure 23A shows that by applying the first process route P1 or the second process route P1, a surface topography 108 having a geometric shape resulting from the overlapping of the recessed structures 110 extending into the substrate material 12a is obtained in at least the surface area of ​​the inner side surface 102 of the temperature-regulating hollow structure 22.

[0155] This is further schematically shown in Figure 24 based on a longitudinal cross-section of the temperature-regulating hollow structure 22, which is clearly exaggerated in proportion and unrelated to the image shown in Figure 23A, and only the transition between the temperature-regulating hollow structure 22 and the substrate material 12a at the bottom of Figure 24 will be described below. As an example, seven recessed structures 110.1, 110.2, 110.3, 110.4, 110.5, 110.6, and 110.7 extending into the substrate material 12a can be seen as solid lines.

[0156] As described above with respect to Figures 13A and 13B, the planned path 80 of the temperature-regulating hollow structure 22, shown again by a dashed line in Figure 24, represents the reference side, from which the settlement structure 108 extends into the substrate material 12a. The overlapping of these settlement structures 110 yields the surface topography 108, and its path can be seen as a thick solid line in the cross-section shown in Figure 24.

[0157] As a result, the surface topography 108 defines mutually adjacent subsidence regions 112 that extend between the peripheral region 114. In Figure 23, only a small number of such subsidence regions and peripheral regions are given reference numerals.

[0158] For example, these peripheral regions 114 form a kind of ridge between two adjacent valleys in the form of two mutually adjacent subsidence regions 112. These peripheral regions 114 may be particularly linear.

[0159] The settlement region 110 may, in particular, be a segment of a body that is point-symmetric or at least axisymmetric, such as a spherical segment, an ellipsoidal segment, or a paraboloid. The resulting settlement region 112 is axisymmetric and may follow, for example, a portion of the outer surface of a spherical segment, an ellipsoidal segment, or a paraboloid. In this case, their peripheral regions 114 are also axisymmetric. However, an asymmetry settlement region 112 with an asymmetry peripheral region 114 may be generated and exist, which can be seen in Figure 23A based on two settlement regions shown as 112 and their peripheral regions shown as 114, respectively. The final geometric shape and dimensions of the settlement region 112 enclosed by the circumferential peripheral regions 114 depend on the geometric shape and dimensions of the settlement structure 110 understood as the basis for the formation of the settlement region 112. For completeness, please note that the settlement structure 110 is distributed across the surface area of ​​the side surface 102. However, Figure 25 naturally only shows the illustrated cross-section and does not show the settlement structure 110 or the resulting settlement region 112 in the foreground or background of the paper.

[0160] The temperature control channel 34 may have a diameter of 0.5 mm to 20 mm, but it is preferable that it has a diameter of 1 mm to 5 mm.

[0161] The length of the temperature control channel 34 varies mainly depending on the dimensions of the substrate 12, and is actually 10 cm or more, but can also be 15 cm or more, or even 20 cm or more.

[0162] The temperature control channel 34 may be curved or may have at least a curved section. As can be seen in Figure 22, the temperature control channel 34 follows the curvature of the support surface 14 at its central section 116, and as a result, the already curved central section 116 extends between two relatively strong curves 118. In Figure 22, the central section 116 and the strongly curved section 118 are indicated by reference numerals only in the case of the temperature control channel 34.1. The central section 116 shown therein leads to the strongly curved section 118 on the left side in Figure 22, the strongly curved section 118 transitions to a straight section 120, the straight section 120 terminates at the opening 36 of the temperature control channel 34.1. Figure 25 shows a magnified view of detail XXV in Figure 22.

[0163] Strong curvature should be understood to mean a curvature angle of 60° to 120°, particularly 80° to 100°, preferably about 90°. Preferably, portion 116 of the temperature control channel 34 extends between two strongly curved portions 118 with a curvature angle of about 90°, as shown in this exemplary embodiment.

[0164] In this case, the curvature of the strongly curved section 118 generally forms an arc. For example, with a curvature of 90°, the two parts of the flow path are not strictly perpendicular.

[0165] The outer radius of curvature R and diameter D of the strongly curved section, in this case the strongly curved section 118, as shown in Figure 25, define the ratio R / D. Preferably, such a ratio R / D is 2 to 6, more preferably 2.5 to 5, and particularly preferably 2.5 to 3.5. These ratios R / D are not reflected in Figure 25 or the other figures. To make this easier to see, the temperature control channel 34.1 is schematically shown with a proportionally larger diameter.

[0166] The temperature control channel 34 extends to a distance of 1.0 mm to 50.0 mm, 1.0 mm to 20.0 mm, 1.0 mm to 10.0 mm, or 1.0 mm to 5.0 mm relative to the support surface 14 of the substrate 12. In this case, the distance between the temperature control channel 34 and the support surface 14 may vary along its path.

[0167] 3.2 Circuit board Using the method described above, a substrate 12 is obtained that is provided with a temperature-regulating hollow structure 22 and a support surface 14 having a surface shape with excellent stability over time. Over the lifespan of the substrate 12, which is up to 10 years, at least up to 5 years, and at least up to 2 years, the change in the surface shape of the support surface 14 is less than 100 pm, particularly less than 50 pm, and even more particularly less than 25 pm.

[0168] This stability of surface shape is also maintained in the case of the mirror 10, which includes a substrate 12 manufactured by the method described above and provided with the coating 16. Thus, a mirror 10 is obtained in which the change in surface shape is less than 100 pm, particularly less than 50 pm, and even more particularly less than 25 pm, over a lifespan of up to 10 years, at least up to 5 years, and at least up to 2 years.

[0169] The high stability of the surface shape of the support surface 14 of the substrate 12 and the surface shape of the mirror 10 manufactured therefrom is achieved by precisely and intentionally removing the modified substrate material 44, thereby obtaining or restoring a substrate that is uniform in itself, particularly in terms of its microstructure, from a state in which the microstructure is not uniform when the modified substrate material 44 is present.

[0170] This is reflected in the representation of the measured surface shape of the support surface 14 of the substrate 122 that was actually processed for the mirror before and after the etching process, as shown in Figures 26A, B, and C. The surface image representation of the support surface 14 is shown above, and the deviation profile along the measured cross section is shown below.

[0171] Measurements are performed using an interferometry system based on a Fizeau interferometer, with a repeatability of 10 pm RMS and a typical pixel size of 0.12 mm × 0.12 mm.

[0172] Figure 26A shows the surface shape of the support surface 14 in the case of substrate 122 before the etching process to remove the modified substrate material 44, and thus reflects the configuration of substrate 12 having the intermediate structure 40 shown in Figure 10, in which the modified substrate material 44 remains. Recesses 124 of the support surface 14 are shown, three of which are indicated as 124.1, 124.2, and 124.3 in the surface image representation and deviation profile. These recesses 124 are located beneath the support surface 14 where the intermediate structure 40 is incorporated into the substrate material 12a and where the modified substrate material 44 is present. As can be seen in Figure 26A, the recesses 124 follow each path of the intermediate structure 40, which in this case appears as a linear channel. The measurement sections of the deviation profiles in Figures 26A, B, and C extend laterally with respect to the channel.

[0173] For comparison purposes, the substrate 122 does not have an intermediate structure 40 beneath the entire support surface 14; rather, the area to the right of the recess 124 is left unprocessed.

[0174] The recess 124 is caused by the non-uniformity of the microstructure of the substrate material 12a, which is formed beneath the support surface 14 by the modified substrate material 44.

[0175] Figure 26B shows the surface shape of the support surface 14 in the case of the substrate in Figure 26A after performing the etching process to remove the modified substrate material 44, which corresponds to the configuration of the substrate 12 shown in Figure 22. As shown in Figure 26B and evident from the deviation profile, the recesses 124 are significantly reduced after the removal of the modified substrate material 44, and the overall shape deviation of the support surface 14 is reduced.

[0176] Figure 26C shows the representation of the measurement differences shown in Figures 26A and 26B, and also shows the region where there is no temperature-regulating hollow structure 22 below the support surface 14 and the changes are not significant.

[0177] In all cases, the surface shape measured according to Figure 26B exhibits the aforementioned stability over time.

[0178] 4. Semiconductor Technology Equipment / Projection Lithography Equipment Figure 27 again shows the semiconductor technology equipment 6 based on an example of a projection exposure apparatus 200 for EUV semiconductor lithography. Other semiconductor technology equipment, such as a mask inspection apparatus or a wafer inspection apparatus, includes components that are, to some extent, identical or similar to those described here based on the example of the EUV projection exposure apparatus 200.

[0179] The projection exposure apparatus 200 includes an illumination system 202 having a radiation source 204 and an illumination optical unit 206 for illuminating an object field of view 208 on the object surface 210, and a reflective reticle 212 is positioned on the object surface 210. In the illustrated exemplary embodiment, the radiation source 204 is an EUV radiation source that emits EUV radiation as working radiation 214, particularly in the wavelength range of 5 nm to 30 nm. The radiation source 204 may be a plasma source, such as an LPP (laser-generated plasma) source or a GDPP (gas discharge plasma) source. Alternatively, a synchrotron-based radiation source or a free electron laser (FEL) may be used as the radiation source 204.

[0180] Furthermore, the projection exposure apparatus 200 includes a projection optical unit 216 that images the object field of view 208 onto the image field of view 218, and the image field of view 218 is positioned on the image plane 220 of the projection optical unit 216. As an example of an object 222, a wafer supporting a photosensitive layer (referred to as resist) is placed on the image plane 220. The components that move the reticle 212 and the wafer 222 in synchronization are only shown in Figure 27 and are not given reference numerals.

[0181] The projection exposure apparatus 200 comprises a plurality of optical elements 8 in the form of mirrors Mn, which are numbered sequentially according to their arrangement in the beam path of the projection exposure apparatus 20. In this exemplary embodiment, a total of 10 mirrors M1 to M10 are present in the beam path.

[0182] Mirrors M3 and M4 are formed as faceted mirrors containing multiple individual mirrors. Each of the other mirrors Mn is a mirror 10 comprising a monolithic mirror substrate 12 and a coating 16 supported thereon, as shown in Figure 1 for example. For simplicity, these mirrors are shown as parallelepipeds in Figure 27. However, in reality, the surface of the mirror 10 exposed to EUV radiation 214 and with the coating 16 is not planar but curved, as also shown in Figure 1.

[0183] Using the mirrors M1 to M4 of the illumination system 206, a portion of the reticle 212 is illuminated with a desired illumination angle distribution. The mirrors M5 to M10 of the projection optical unit 216 reduce this portion to form an image on the wafer 222. As a result, the structure contained in the reticle 212 is imaged onto the photosensitive layer supported by the wafer 222.

[0184] In this exemplary embodiment, the object 222 is irradiated with working radiation 214 using an optical element 8, which is formed as a mirror 10 of the EUV projection exposure apparatus 200 and has a coating designed to reflect at least 50% of the EUV light incident at a perpendicular or substantially perpendicular incidence.

[0185] The semiconductor technology apparatus 6 is part of a manufacturing process that can be used to manufacture a structured electronic component 224, schematically shown in Figure 27 along with the structure 226 produced as a result of the entire manufacturing process, and the manufacturing process includes other steps in addition to the process in the semiconductor technology apparatus 6. However, what is important here is that the semiconductor technology apparatus 6 comprises at least one optical element 8 manufactured by one of the methods included in the modified forms of the method described above.

[0186] The structured electronic component 224 is in particular the computer chip 228, and as mentioned at the beginning, a projection exposure apparatus, in this case the projection exposure apparatus 200, is used in its manufacture.

[0187] 5. Conclusion All of the above methods, steps, sequences, concepts, and principles can be combined with each other, and this is also reflected in the combination of features described in the claims.

Claims

1. A method for incorporating a temperature-regulating hollow structure (22) into a substrate (12), particularly into the substrate (12) of an optical element (8), and especially into the substrate (12) of the mirror (10) of an EUV projection exposure apparatus, (A) A step of preparing a substrate (12) made of substrate material (12a), (B) A step of producing an intermediate structure (40) comprising an intermediate layer (42) of a modified substrate material (44) and an intermediate hollow structure (46) in which at least a portion of the intermediate layer (42) surrounds, wherein the modified substrate material (44) is more sensitive to chemically active processing media than the substrate material (12a), (C) A step of introducing a chemically active processing medium (90) to the intermediate hollow structure (46) to remove the intermediate layer (42) of the modified substrate material (44), thereby generating the temperature-regulating hollow structure (22), In a method including the above, the intermediate structure (40) in step (B) (B.1) A step of forming the modified substrate material (44) at the modified position (66) by sequentially focusing a modifying light beam (56) at the modified position (66), (B.2) The step of removing material at the ablation position (72) by sequentially focusing the ablation light beam (70) onto the ablation position (72) A method characterized by being produced by the following.

2. In the method according to claim 1, the first process route (P1) or the second process route (P2) is executed, In the case of the first process route (P1), step (B.1) is executed in the first process step (P1-S1), and step (B.2) is executed in the second process step (P1-S2). A method characterized in that, in the case of the second process route (P2), step (B.2) is executed in the first process step (P2-S1), and step (B.1) is executed in the second process step (P2-S2).

3. In the method according to claim 2, the first process route (P1) is executed, In the aforementioned first process step (P1-S1), a material structure (52) including the modified substrate material (44) is manufactured by step (B.1), A method characterized in that, in the second process step (P1-S2), the material (44; 12a) is removed by step (B.2) to create the intermediate hollow structure (46), and the modified substrate material (44) of the material structure (52) remains as the intermediate layer (42).

4. In the method according to claim 3, in the first process step (PS-S1) of the first process route (P1), step (B.1) is performed such that a first type (52-I) material structure (52) or a second type (52-II) material structure (52) is produced. In the case of the first type (52-I) material structure (52), the modified substrate material (44) is formed to fill the cross-section, In the case of the second type (52-II) material structure (52), the modified substrate material (44) is formed such that a core region of the substrate material (12a) remains surrounded by at least a portion of the modified substrate material (44).

5. The method according to claim 4, characterized in that in the second process step (P1-S2) of the first process route (P1), step (B.2) is performed such that the modified substrate material (44) is removed in the case of the first type (52-I) material structure (52), and the substrate material (12a) of the core region is removed in the case of the second type (52-II) material structure (52), thereby creating the intermediate hollow structure (46), and the intermediate layer (42) is formed by the remaining modified substrate material (44) of the material structure (52).

6. In the method according to any one of claims 2 to 5, the second process route (P2) is executed, In the first process step (P2-S1), the substrate material (12a) of the substrate (12) is removed by step (B.2) to create the intermediate hollow structure (46). A method characterized in that, in the aforementioned second process step (P2-P2), the intermediate layer (42) is formed from the modified material (44) by step (B.1), thereby producing the intermediate structure (40).

7. The method according to claim 6, wherein in the case of the second process step (P2-S2) of the second process route (P2), the intermediate hollow structure (46) is filled with an auxiliary fluid (84), so that when step (B.1) is performed, the auxiliary fluid is filled, and the auxiliary fluid is preferably held as a stationary fluid volume.

8. In the method according to claim 7, the refractive index n at the wavelength of the modifying light beam (56) Ｆ The refractive index n of the substrate material (12a) at the same wavelength Ｍ With a tolerance of less than 20%, preferably less than 10%, preferably less than 5%, and particularly preferably less than 1%, the refractive index n of the substrate material (12a) Ｍ A method characterized by using an auxiliary fluid (84) that matches the specified fluid.

9. A method according to any one of claims 1 to 8, characterized in that a flushing fluid (76) is applied to the ablation location (72) during the execution of step (B.2) so that the removed material (44; 12a) is washed away.

10. A method according to any one of claims 1 to 9, characterized in that in step (C), the chemically active processing medium (90) is flowed through the intermediate hollow structure (40) at least at a specific point in time, preferably continuously over time.

11. A method according to any one of claims 1 to 10, wherein the chemically active processing medium (90) is an etching medium (90'), an oxidizing agent, or a reducing agent, and is particularly characterized in that in step (C), the etching medium (90') removes the intermediate layer (42) of the modified substrate material (44) by an etching process.

12. A method for manufacturing an optical element, particularly a mirror (10) for an EUV projection exposure apparatus, wherein a temperature-regulating hollow structure (22) is incorporated into a substrate (12) according to the method of any one of claims 1 to 11, and further processing comprises one or more steps of chemically and / or physically treating at least one surface of the substrate (12) and forming or applying a coating (16) onto the substrate (12) that is designed to reflect at least 50% of EUV light incident perpendicularly or substantially perpendicularly.

13. A substrate for manufacturing optical elements, particularly for manufacturing a mirror (10) of an EUV projection exposure apparatus, preferably a monolithic substrate, having a temperature-regulating hollow structure (22), particularly a temperature-regulating hollow structure (22) incorporated according to the method described in any one of claims 1 to 11, in a substrate (12), A substrate characterized in that at least one temperature-regulating hollow structure (22) defines an inner side surface (102) in which the average roughness Ra in at least a portion of the region is 10.0 μm to 5.0 μm, particularly 10.0 μm to 6.5 μm, 10.0 μm to 8.0 μm, 8.5 μm to 5.0 μm, 7.0 μm to 5.0 μm, or 8.5 μm to 6.5 μm, according to DIN EN ISO 25178 as of April 2023, or an inner surface (102) in which the average roughness Ra in at least a portion of the region is 5.0 or less, particularly 5.0 to 0.1 μm, preferably 4.5 μm to 0.125 μm, 4.0 μm to 0.15 μm, 3.5 μm to 0.175 μm, or 3.0 μm to 0.2 μm.

14. A substrate for manufacturing optical elements, particularly for manufacturing a mirror (10) of an EUV projection exposure apparatus, preferably a monolithic substrate, having a temperature-regulating hollow structure (22), particularly a temperature-regulating hollow structure (22) incorporated according to the method described in any one of claims 1 to 11, in a substrate (12), A substrate characterized in that at least one temperature-regulating hollow structure (22) defines an inner side surface (102) having a surface topography (108) having a geometric shape resulting from the overlap of recessed structures (110) extending into the substrate material (12a) of the substrate (12) in at least a portion of the area.

15. A substrate according to claim 14, wherein the one or more recessed structures (110) are themselves segments of an object that is point-symmetric or at least axis-symmetric.

16. A substrate according to claim 14 or 15, characterized in that the surface topography (108) defines mutually adjacent subsidence regions (112) that extend between peripheral regions (114), particularly linear peripheral regions (114).

17. A substrate according to claim 16, characterized in that one or more recessed regions (112) are axially symmetric or axially asymmetric.

18. A substrate according to claim 17, characterized in that the axially symmetric recessed region (112) follows a part of the outer surface of a spherical segment, an ellipsoidal segment, or a paraboloid.

19. In the substrate according to any one of claims 13 to 18, the at least one temperature-regulating hollow structure (22) is a temperature-regulating channel (34) having one or more of the following features, as a feature: a) The temperature control channel (34) has a diameter of 0.5 mm to 20 mm, preferably 1 mm to 5 mm. b) The temperature control channel (34) has a length of 10 cm or more, 15 cm or more, or 20 cm or more. c) The temperature control channel (34) is curved or has at least one curved portion (116; 118), d) The temperature control channel (34) has a portion (116) that follows the curvature of the support surface (14) for coating (16) of the substrate (12), e) The temperature control channel (34) has a strongly curved section (118) with a curvature angle of 60° to 120°, particularly 80° to 100°, preferably about 90°. f) The temperature control channel (34) has a strongly curved section (118) with a curvature angle of 60° to 120°, particularly 80° to 100°, preferably about 90°, and is curved, g) The temperature control channel (34) has a strongly curved section (118) with a curvature angle of 60° to 120°, particularly 80° to 100°, preferably about 90°, forming an arc, and defining the outer radius of curvature R and diameter D, with the ratio of radius of curvature R to diameter D R / D being 2 to 6, preferably 2.5 to 5, particularly preferably 2.5 to 3.

5. h) A substrate characterized in that the temperature control channel (34) is located at a distance of 1.0 mm to 50.0 mm, 1.0 mm to 20.0 mm, 1.0 mm to 10.0 mm, or 1.0 mm to 5.0 mm from the support surface (14) for coating (16) of the substrate (12).

20. A substrate for manufacturing an optical element (8), particularly for manufacturing a mirror (10) of an EUV projection exposure apparatus, preferably a monolithic substrate, having a temperature-regulating hollow structure (22), particularly a temperature-regulating hollow structure (22) incorporated according to the method of any one of claims 1 to 11, and defining a support surface (14) for coating (16), in a substrate (12), A substrate characterized in that, for a substrate (12) lifespan of up to 10 years, at least up to 5 years, and at least up to 2 years, the change in the surface shape of the support surface (14) is less than 100 pm, particularly less than 50 pm, and even more particularly less than 25 pm.

21. A substrate having the features described in claim 13 and the features described in any one of claims 14 to 19.

22. A substrate having the features described in claims 20 and 21.

23. A substrate according to any one of claims 13 to 22, wherein the temperature-regulating hollow structure (22) is incorporated according to the method described in any one of claims 1 to 11.

24. An optical element comprising a substrate (12), particularly a mirror (10) of an EUV projection exposure apparatus, The optical element is characterized in that the substrate (12) is the substrate (12) described in any one of claims 12 to 23.

25. An optical element comprising a substrate (12), particularly a mirror (10) of an EUV projection exposure apparatus, and more particularly the optical element according to claim 24, characterized in that, for a lifespan of the optical element of up to 10 years, at least up to 5 years, and at least up to 2 years, the change in the surface shape of the optical element (8) is less than 100 pm, particularly less than 50 pm, and even more particularly less than 25 pm.

26. The optical element according to claim 24 or 25, wherein the optical element (8) is a mirror (10) of an EUV projection exposure apparatus, and the substrate (12) has a support surface (14) that supports a coating (16) designed to reflect at least 50% of EUV light incident perpendicularly or substantially perpendicularly.

27. The optical element according to claims 26, 25, and 24.

28. A semiconductor technology apparatus, particularly an EUV projection exposure apparatus (200), a mask inspection apparatus, or a wafer inspection apparatus, capable of irradiating an object (222) with working radiation (214) using at least one optical element (8), wherein the optical element (8) is an optical element (8) according to any one of claims 24 to 27.

29. The apparatus according to claim 28, wherein the apparatus (6) is an EUV projection exposure apparatus (200), and the at least one optical element (8) is the mirror (10) according to claim 26.

30. A structured electronic component, characterized in that the structured electronic component (224) is manufactured using a semiconductor technology apparatus (6) according to claim 28 or 29 and at least one optical element (8) according to any one of claims 24 to 27.

Images