Method of manufacturing an euv mirror element and intermediate product of an euv mirror element

Abstract

This invention relates to a method for manufacturing EUV reflector components (M1-M6, 40), in which a multilayer coating system (31) is applied to the surface of a reflector substrate (30, 37) to form an optical surface with high reflectivity to EUV radiation. A temporary protective layer structure (36) is formed on the multilayer coating system (31). The protective layer structure (36) includes a protective layer (35) and a sacrificial layer (34) located between the protective layer (35) and the multilayer coating system (31). The sacrificial layer (34) is a layer made by oxidizing one layer of the multilayer coating system (31). The temporary protective layer structure (36) is removed before the EUV reflector component is put into use. This invention also relates to an intermediate product of the EUV reflector component.

Description

[0001] This patent application claims priority to German patent application DE 10 2023 212 037.2, filed on November 30, 2023, the entire contents of which are incorporated herein by reference (“incorporated by reference”). Technical Field

[0002] This invention relates to a method for manufacturing EUV reflector components. The invention also relates to intermediate products of EUV reflector components. Background Technology

[0003] Microlithography projection exposure equipment is used to fabricate integrated circuits with extremely small structures. A photomask irradiated by very short-wavelength extreme ultraviolet radiation (EUV radiation) is imaged onto a lithographic object in order to transfer the mask structure onto the lithographic object.

[0004] The projection exposure apparatus contains multiple EUV mirrors, each with an optical surface that reflects EUV radiation. To reduce EUV radiation loss within the projection exposure apparatus, the EUV mirrors have optical surfaces with high reflectivity to EUV radiation. The optical surfaces are formed by a multilayer system, through which incident EUV radiation is reflected away from the multilayer system.

[0005] In addition to the projection exposure equipment itself, there are other optical systems that operate in conjunction with the microlithography projection exposure equipment. These include, for example, measuring devices for checking the reflectivity of EUV mirrors, devices for checking modules and subsystems, and measuring devices for checking the properties or state of photomasks. EUV mirrors are also used in such optical systems.

[0006] There is an intermediate stage between the application of the multilayer system to the reflector substrate and the subsequent commissioning of the associated EUV reflector component, during which the EUV reflector component may be exposed to various influences. For example, the EUV reflector component may be stored, packaged, transported, or installed. Further processing steps may also be performed on the EUV reflector component.

[0007] It has been found that multilayer systems can be contaminated or damaged during this intermediate stage. Potential damage includes mechanical damage caused by the cutting process (e.g., laser cutting); (chemical) layer damage caused by etching media, photoresists, and / or solvents; contamination caused by environmental influences and / or inadequate removal of the applied layer (e.g., photoresist); particulate contamination caused by inadequate removal of the applied layer (e.g., photoresist); changes in surface termination due to chemical interactions of the surface during structuring; layer roughening caused by etching media, photoresists, and / or solvents; diffusion of solvents and / or etching media through the EUV layer and layer separation resulting in subsequent use of the EUV mirror component; and light- or particle-based radiation damage. All of these effects can lead to damage to the multilayer system and thus a reduction in the quality of the optical surfaces of the EUV mirror component. Summary of the Invention

[0008] The problem solved by this invention is to provide a method for manufacturing EUV reflector components and intermediate products of EUV reflector components, thereby avoiding these disadvantages. This problem is solved by the features of the independent claims. Advantageous embodiments are specified in the dependent claims.

[0009] In the method for manufacturing an EUV reflector component according to the present invention, a multilayer system is applied to the surface of a reflector body substrate to form an optical surface that is highly reflective to EUV radiation. A temporary protective layer structure is fabricated on the multilayer system. The protective layer structure includes a protective layer and a sacrificial layer disposed between the protective layer and the multilayer system. The temporary protective layer structure is removed before the EUV reflector component is put into use.

[0010] This invention is based on the insight that protecting optical surfaces from damage in intermediate stages is not entirely straightforward due to conflicting requirements. Indeed, protective layers are known in principle that can be applied to multilayer systems and provide adequate protection against environmental conditions. However, it has proven difficult to remove such protective layers from multilayer systems without damaging them. In contrast, layers that can be easily removed without damaging the multilayer system typically do not provide sufficient protection against the stresses encountered.

[0011] This invention proposes a temporary protective layer structure comprising a protective layer and a sacrificial layer disposed between the protective layer and a multilayer system. The protective layer can be configured such that it provides sufficient protection against encountered strain. It is acceptable that removing this protective layer requires more aggressive process steps because the underlying sacrificial layer prevents these aggressive steps from acting downwards into the multilayer system. After removing the protective layer, the sacrificial layer can be removed using less aggressive process steps. The less aggressive process steps can be selected in a manner that does not damage the multilayer system.

[0012] The temporary protective layer structure ensures that the multilayer system is not damaged during the intermediate stage between applying the multilayer system to the mirror body substrate and putting the EUV mirror component into service. After removing the temporary protective layer structure, the EUV mirror component can be used with a perfectly intact optical surface.

[0013] Multilayer systems can include alternating layers of molybdenum and silicon. Using such coatings, approximately 70% of incident EUV radiation can be reflected. Multilayer systems can be optimized for reflecting EUV radiation in the extreme ultraviolet spectral range between 5 nm and 30 nm, particularly in the extreme ultraviolet spectral range of 13.5 nm.

[0014] A multilayer system may include a top layer made of a material different from the alternating layers beneath the multilayer structure. After the temporary layer structure is removed, the top layer forms the surface of the EUV mirror component. During subsequent operation of the EUV mirror component, the top layer may provide protection, for example, to counteract the rapid degradation of the multilayer system. The top layer may be made of an inorganic material. For example, the top layer may be made of ruthenium, TiO2, or rhenium. The top layer may have a thickness of 1 nm to 20 nm, preferably 2 nm to 10 nm.

[0015] The sacrificial layer can be applied to a multilayer system. It can be applied directly to the top layer of the multilayer system. The material used for the sacrificial layer can be selected to meet one or more of the following requirements: The sacrificial layer should be removable without residue and should not damage or contaminate the multilayer system; this can be achieved, in particular, through the high purity of the sacrificial layer material. The sacrificial layer should have good adhesion to the surface of the multilayer system. The sacrificial layer should form a good adhesion base for the protective layer. The sacrificial layer should have good wetting behavior on the surface of the multilayer system. The surface of the sacrificial layer should have low roughness to avoid negative impacts on subsequent processing steps.

[0016] In one embodiment, the sacrificial layer is a carbon layer. Preferably, at least 80%, more preferably at least 90%, and even more preferably at least 99.99% of the carbon layer is composed of carbon. The percentage related to the proportion of material in the layer is related to the number of particles present in the layer. The surface energy of carbon is lower than that of metals. Therefore, good coverage of the multilayer system is expected. Carbon has the advantage that it can be removed using hydrogen plasma. When using hydrogen plasma, there is no risk of damaging the multilayer system because, in any case, the optical surfaces are exposed to hydrogen plasma during EUV operation. Other methods for removing the carbon layer are also possible. For example, the carbon layer can have a thickness between 1 nm and 30 nm, preferably between 2 nm and 5 nm.

[0017] Alternative materials for the sacrificial layer structure include, for example: nitrides; high-purity, smoothly grown carbon compounds with high sublimation points, such as advanced benzo[a]benzene; carbon compounds with low sublimation points that can be removed by heating to temperatures below 350°C; metals; and 2D materials, such as graphene or transition metal dichalcogenides. In the case of organic materials used for the sacrificial layer, the layer thickness is preferably less than 30 nm. In the case of inorganic sacrificial layers, the layer thickness can be, for example, between 10 nm and 300 nm.

[0018] Possible methods for applying the sacrificial layer include sputtering, electron beam deposition, chemical vapor deposition, physical vapor deposition, atomic layer deposition, spin coating, and spraying. Combinations of these methods are also possible. Typically, the sacrificial layer should be applied in such a manner that the multilayer system will not be damaged by its application. In particular, the temperature should not exceed 350°C.

[0019] Instead of applying the sacrificial layer to the multilayer system, it can also be manufactured by transforming the top layer of the multilayer system. In one embodiment, the sacrificial layer is manufactured by oxidation of the top layer. Sacrificial layers manufactured by oxidation are advantageous because the additional layer application step for the sacrificial layer can be omitted. Another advantage may stem from the fact that oxides in the top layer of a multilayer system typically have only a slight effect on the reflectivity of the optical surface to EUV radiation. Therefore, it is acceptable not to completely remove the sacrificial layer and retain oxide residues before the EUV mirror component is put into service. However, in this case, at least a majority of the sacrificial layer should be removed, particularly at least 80%, preferably at least 90%, and more preferably at least 95%.

[0020] A sacrificial layer with a first sublayer and a second sublayer can also be fabricated. The first sublayer of the adjacent multilayer system can be optimized for easy removal. The second sublayer of the sacrificial layer can be optimized to form a suitable substrate for applying a protective layer. For example, the second sublayer of the sacrificial layer can form a surface that can be easily wetted by the material of the protective layer. For example, if the material of the protective layer is corrosive to the first sublayer of the sacrificial layer, the second sublayer can also form a separation layer between the protective layer and the first sublayer of the sacrificial layer. Alternatively, the second sublayer of the sacrificial layer can be selected such that it is sufficiently resistant to the deposition method for applying the protective layer and / or the cleaning method for removing the protective layer.

[0021] A protective layer can be applied to the sacrificial layer after its fabrication. The material of the protective layer should be selected to meet one or more of the following requirements: stability under mechanical loads, stability relative to the etching medium, stability relative to photoresist and / or solvents, stability at temperatures up to 350°C, effective diffusion barrier against oxygen and / or photoresist and / or solvents, good adhesion to the sacrificial layer, low roughness so as not to adversely affect further processing steps, removability without residue, and without damaging or contaminating the EUV layer. The thickness of the protective layer can, for example, be between 0.1 μm and 10 μm.

[0022] In one embodiment, the protective layer is applied as a protective varnish having specific properties. Specifically, the protective layer can be formed from a protective varnish in the form of a photoresist. In one embodiment, the protective varnish has good cohesive strength, allowing it to be peeled off from the sacrificial layer in a manner similar to a thin film. In the case of a protective varnish, the layer thickness can be, for example, between 1 μm and 10 μm.

[0023] In an alternative embodiment, the protective layer is formed by applying silicon dioxide (SiO2). Silicon dioxide has sufficient resistance to achieve the desired protective function. For example, the silicon dioxide layer can be removed using an HF vapor etching process that has high selectivity for removing silicon dioxide. In the case of a protective layer made of silicon dioxide, the layer thickness can be, for example, between 0.1 μm and 0.3 μm. The protective layer can also be formed of other suitable oxides, particularly other suitable silicon oxides.

[0024] The protective and sacrificial layers can be removed from the surface of a multilayer system in two separate processes. Alternatively, they can be removed in a single process. Generally, the protective and sacrificial layers should be removed in such a manner that one or more of the requirements specified below are met. Damage to the multilayer system should be avoided. The protective and sacrificial layers should be removed without residue, leaving no contaminants on the surface of the multilayer system. Increased particulate contamination or roughening of the surface of the multilayer system should be avoided. Surface temperatures should not exceed 350°C using suitable non-thermal methods or appropriate substrate cooling.

[0025] Commonly used methods for removing protective and / or sacrificial layers include: dry chemical methods, such as using HF vapor, CF4, CHF3, etc.; plasma cleaning, such as by H plasma and / or O plasma; cleaning with an ion beam source; wet chemical cleaning; laser cleaning; application of CO2 beams; heat treatment at temperatures below 350°C and / or suitable substrate cooling; and stripping of the protective layer as a film. These cleaning methods can be combined with each other and / or applied sequentially during the removal of the protective and / or sacrificial layers.

[0026] If the protective layer is formed by a protective varnish, it may be advantageous to remove it using a wet chemical method. In a wet chemical method, the protective layer is treated with a liquid solvent to dissolve its structure. Wet chemical methods generally have the advantage of reliably removing particles and contaminants not only on the protective layer but also within it. The solvent can be chosen so that it does not corrode the underlying sacrificial layer.

[0027] If the protective layer is composed of silica, it may be advantageous to remove it using dry chemical methods. In particular, the protective layer can be removed using HF vapor etching, which is highly selective for removing silica. If the protective layer is completely dissolved in this manner, particles and contaminants can be removed both on and within the protective layer.

[0028] If a contamination layer has already formed on or within the protective layer structure, for example by particle deposition or oxidation, the contamination layer can be removed before removing the layer below it in each case. One possible method for removing the contamination layer is to use oxygen plasma.

[0029] The removal of the protective layer can be followed by the removal of the sacrificial layer. For this purpose, a gentle approach is appropriate to avoid damaging the multilayer system. For example, a commonly suitable method is to apply hydrogen plasma for removal (H* plasma or H' plasma). This is particularly suitable when the sacrificial layer is a carbon layer. Even when the sacrificial layer is created by oxidation of the top layer of the multilayer system, it can be removed by hydrogen plasma. If desired, this can be combined with a physical etching process, such as pre-treatment with an inert gas plasma. The inert gas plasma can be, for example, neon plasma, argon plasma, or krypton plasma.

[0030] The multilayer system can be applied to the reflector substrate under vacuum conditions in a processing chamber. The sacrificial layer of the temporary protective layer structure according to the invention can be manufactured without the EUV reflector components leaving the processing chamber. Maintaining a vacuum between applying the multilayer system and manufacturing the sacrificial layer reduces the risk of contamination.

[0031] Furthermore, a vacuum can be maintained until the protective layer of the temporary protective layer structure has also been applied. In one embodiment, the protective layer is manufactured in the same processing chamber as the multilayer system.

[0032] This method can be implemented in such a way that the EUV mirror component is not subjected to any further processing steps during the intermediate stage between the fabrication and removal of the temporary protective layer structure. The function of the protective layer structure can be primarily to protect the optical surfaces during transport and storage.

[0033] In another embodiment, one or more processing steps are performed on the EUV mirror component during an intermediate stage. Specifically, the EUV mirror component may undergo processing steps in which material is removed from the multilayer structure and / or from the substrate of the EUV mirror component. For example, a processing step may be performed to create a structure on the optical surface of the EUV mirror component. The structure can be created using photolithography. For this purpose, a photoresist applied to the optical surface of the EUV mirror component may be locally exposed according to the structure to be created. The processing steps may be performed in areas of the optical surface where the photoresist has been locally removed.

[0034] In addition to, or as an alternative, one or more of the processing steps mentioned below can be performed. Machining can be performed, for example, for edge grinding of optical surfaces and / or for processing substrate contours. Thermal treatment can be performed, for example, to change the state of a layer or substrate or for welding or bonding. In one embodiment, the thermal treatment is performed outside a vacuum. Chemical treatment is also possible, for example, for structuring purposes, which can be performed by wet chemical methods, from the gas phase, or by ion beam etching. In one embodiment, chemical treatment is combined with photolithography. Another variation is irradiation with ions, with electrons, with UV radiation, or with X-ray radiation.

[0035] The protective layer structure according to the present invention functions to provide protection for the optical surface during the processing steps.

[0036] When using photoresist for structuring, the photoresist can also serve as the protective layer of the temporary protective layer structure. In another embodiment, the photoresist is applied to the protective layer of the temporary protective layer structure. The photoresist and the protective layer can then be removed together in a common method step. Alternatively, the photoresist can be removed separately from the protective layer in the preceding method steps.

[0037] Structuring can be used to subdivide a surface completely covered by a multilayer system into multiple mirror elements. Processing steps can be used to remove portions of the mirror body substrate to create flexures within the substrate, such that each mirror element is hinged to the body of the substrate via these flexures. The mirror body substrate can be made of silicon, particularly monocrystalline silicon. The function of the temporary protective layer structure according to the invention is to provide protection for the optical surface during these processing steps (because it is retained). EUV mirror components comprising multiple individual mirror elements can, for example, be used as faceted mirrors in the illumination system of microlithography projection exposure equipment, particularly as MEMS faceted mirrors.

[0038] It can also have a series of method steps that begin with a processing step to subdivide the optical surface into multiple mirror elements, which then leads to the formation of a temporary protective layer structure. This opens up the possibility of the temporary protective layer structure protecting the outer surface of the mirror element located between the optical surface and the flexure.

[0039] In one embodiment, the temporary protective layer structure is fabricated on an optical surface without undergoing any further structuring, thus giving the EUV mirror component a uniform and continuous optical surface during subsequent use. Such EUV mirrors can be used in optical systems, such as projection lenses in microlithography projection exposure equipment, to deflect and shape EUV beam paths. In the case of these mirrors, there are often stringent requirements regarding the geometry of the optical surface. To meet these requirements, the mirror body can be constructed from a material with a coefficient of thermal expansion of zero cross temperature. An example of such a material is known as ULE. TM (Ultra-low expansion) or ZERODUR TM The titanium silicate glass. In such embodiments, the temporary protective layer structure may primarily function to protect the optical surface during transport and storage, as well as during steps other than those related to the structuring of the optical surface. For example, these include bonding steps, wherein the temporary protective layer structure protects the optical surface from adhesive vapors.

[0040] Typically, metallic materials, single-crystal materials, or glass are also suitable materials for the substrate of the mirror body. In one embodiment, the mirror substrate material is silicon, particularly single-crystal silicon.

[0041] Before mounting the EUV mirror component into the optical system, the temporary protective layer structure can be removed in a separate process. During this process, in the phase between removing the temporary protective layer structure and mounting, the optical surfaces of the EUV mirror component are at risk of damage or contamination. In one embodiment, the sacrificial layer is therefore removed only after the EUV mirror component has been mounted into the optical system. This is particularly advantageous if hydrogen plasma is used to remove the sacrificial layer, as the multilayer system can be exposed to hydrogen plasma under any circumstances during subsequent operations. The protective layer can be removed in a preceding step before mounting the EUV mirror component. This also includes the possibility of removing both the sacrificial layer and the protective layer after the EUV mirror component has been mounted.

[0042] The present invention also relates to intermediate products of EUV reflector components. A multilayer system forming an optical surface highly reflective to EUV radiation is applied to the surface of a reflector body substrate. A temporary protective layer structure is disposed on the multilayer system. The protective layer structure includes a protective layer and a sacrificial layer disposed between the protective layer and the multilayer system.

[0043] This invention includes the development of a method having features described in the context of an intermediate product of an EUV reflector component according to the invention. This invention also includes the development of an intermediate product of an EUV reflector component having features described in the context of a method according to the invention. Attached Figure Description

[0044] The invention is described below by way of example based on advantageous embodiments and with reference to the accompanying drawings, wherein:

[0045] Figure 1 This shows a microlithography projection exposure device;

[0046] Figure 2 Showing details of the EUV reflector components;

[0047] Figure 3 According to the second state of the EUV reflector component Figure 2 The view;

[0048] Figure 4 The third state of the EUV reflector component is shown according to Figure 2 The view;

[0049] Figure 5 The fourth state of the EUV reflector component is shown according to Figure 2 The view;

[0050] Figure 6-8 Various intermediate states during the manufacturing process of the faceted mirror are shown;

[0051] Figure 9 An alternative embodiment of the invention is shown according to Figure 7 The view;

[0052] Figure 10 A diagram illustrating the process according to the present invention is shown;

[0053] Figure 11 An alternative embodiment of the invention is shown. Figure 10 The view. Detailed Implementation

[0054] Figure 1 A microlithography EUV projection exposure apparatus is schematically shown. The projection exposure apparatus includes an exposure beam source 14, an illumination system 10, and a projection lens 22, which operate together in a vacuum chamber 23.

[0055] Exposure beam source 14 generates electromagnetic radiation in the EUV range, specifically electromagnetic radiation with wavelengths between 5 nm and 30 nm. The exposure radiation emitted from exposure beam source 14 is focused into intermediate focal plane 16 by collector 15. The exposure radiation passing through intermediate focal plane 16 is guided into object plane 12 by illumination system 10, resulting in the object field in object plane 12 being illuminated with uniform radiation intensity.

[0056] The illumination system 10 includes a deflector 17 for deflecting exposure radiation to the first faceted mirror 18. A second faceted mirror 19 is disposed downstream of the first faceted mirror 18. The second faceted mirror 19 is used to image the facets of the first faceted mirror 18 onto the object plane 12.

[0057] A photomask 13 is arranged in the object plane 12 and imaged onto the image plane 21 by multiple mirrors M1-M6 of the projection lens 22. The structure formed on the photomask 13 is transferred to the radiation-sensitive layer of the wafer 20 arranged in the image plane 21. The photomask 13 is suspended on the first scanning device 24, and the wafer 20 is placed on the second scanning device 25, so that the wafer 20 can be exposed during the scanning process, during which the photomask 13 and the wafer 20 move synchronously with each other.

[0058] Figure 1 Each of the EUV reflectors 17, 18, 19, and M1-M6 is provided with a multi-layer system that forms an optical surface with high reflectivity to EUV radiation. The following is based on... Figure 2 This can be explained in more detail using an example with mirror M1. Figure 2 An enlarged cross-sectional view showing details of the reflector M1.

[0059] The reflector M1 includes a reflector body 30 made of a reflector substrate material with ultra-low thermal expansion (“ultra-low expansion material”). Examples of such a material include those named ULE. TM or ZERODUR TM The titanium silicate glass sold both possess what is known as a zero cross temperature. For example, for ULE... TM At this zero-crossing temperature of approximately 30°C, the coefficient of thermal expansion has a zero crossover in its temperature dependence, and no thermal expansion of the reflector substrate material occurs or only negligible thermal expansion occurs near this zero crossover.

[0060] A multilayer system 31 having alternating layers 32 of molybdenum and silicon is applied to the mirror body 30. Each layer 32 of the multilayer system 31 can have a thickness, for example, on the order of 5 nm. The multilayer system 31 includes a top layer 33, which is well resistant to effects occurring during the operation of the EUV mirror. The top layer 33 can have a slightly larger thickness than the other layers 32 of the multilayer system, and the thickness can be, for example, between 1 nm and 20 nm. For example, the top layer 33 can be composed of ruthenium, TiO2, or rhenium.

[0061] Figure 2 The EUV mirror M1 is shown in its state for use in a microlithography projection exposure apparatus. The top layer 33 of the multilayer system 31 forms the surface of the EUV mirror M1 during operation of the projection exposure apparatus.

[0062] The EUV reflector M1 also has the characteristics of being manufactured during the period immediately following the application of the multilayer system 31 to the reflector body 30. Figure 2 The EUV reflector M1 is in a state of flux. Between this time and the time it is used in the projection exposure equipment, there exists a relatively long intermediate phase. During this intermediate phase, the EUV reflector M1 undergoes various processing steps, such as storage, packaging, transportation, and unpacking. Figure 2 In the state shown, the surface of the multilayer system 31 will be directly exposed to the conditions of the surrounding environment, and this will be associated with the risk of contamination or damage to the multilayer system 31.

[0063] This invention proposes to protect the multilayer system 31 with a protective layer structure 36 during the intermediate stage; see also Figure 3 , 4 The protective layer structure 36 includes a sacrificial layer 34 and a protective layer 35, which are successively applied to the surface of the EUV mirror. The sacrificial layer 34 is optimized to form a good substrate for applying the protective layer 35, and can be easily and, in particular, removed again without residue before the EUV mirror M1 is put into service, without damaging the top layer 33 of the multilayer system 31. The protective layer 35 is optimized to provide good protection so as to ensure that conditions during intermediate stages do not damage the multilayer system 31. The requirement for a more aggressive step of removing the protective layer 34 again before the EUV mirror M1 is acceptable because the sacrificial layer 34 underneath prevents the aggressive step from affecting the multilayer system 31.

[0064] Figure 3The EUV reflector M1 is shown with the sacrificial layer 34 applied to the top layer 33 of the multilayer system 31. The sacrificial layer 34 is applied in the same processing chamber where the top layer 33 of the multilayer system 31 has also been pre-applied. Both the top layer 33 and the sacrificial layer 34 are applied in a vacuum, with the vacuum continuously maintained during and between the two steps. The sacrificial layer 34 has a surface that provides a good substrate for the subsequent protective layer 35.

[0065] The protective layer 35 can be applied in a separate processing chamber. Figure 4 This shows the state of the EUV reflector M1, where a complete protective layer structure 36 with a sacrificial layer 34 and a protective layer 35 has been applied.

[0066] Before the EUV reflector M1 is put into use, the protective layer structure 36 is removed again. Figure 5 An intermediate state is shown, in which the protective layer 35 has been removed, and the sacrificial layer 34 remains in its state after the action of the corrosive method steps used to remove the protective layer 35. The sacrificial layer may in particular have an uneven and / or damaged surface, which is unsuitable for applying another layer.

[0067] After the remaining sacrificial layer 34 has also been removed using a gentler method, the EUV reflector M1 returns to its original position. Figure 2 The EUV mirror M1 is shown in the diagram. It is ready for use in a microlithography projection exposure system.

[0068] Figure 6-8 It shows Figure 1 The various stages in the fabrication of components of the first faceted mirror 18 or the second faceted mirror 19 of the microlithography projection exposure apparatus. A substrate body 37 made of single-crystal, polycrystalline, or amorphous silicon is provided. Corresponding to... Figure 2 The multilayer system 31 is applied to the surface of the substrate body 37.

[0069] A protective layer structure 36 is applied to the multilayer system 31, the protective layer 35 of which is formed using a photoresist. Areas where material is removed by subsequent processing steps are defined by appropriate exposure to the photoresist. Figure 7 The diagram shows the state in which material is removed between the individual EUV mirror components 40, separating them from each other until they enter the substrate body 37. Each EUV mirror component 40 has a mirror body 30, which is connected to the remainder of the substrate body 37 via a flexure 39, shown schematically. A protective layer structure 36 ensures that the multilayer system 31 is not damaged in the areas where the optical surfaces of the EUV mirror components 40 are intended to be formed.

[0070] Each of the faceted mirrors 18 and 19 is composed of... Figure 7The type shown is composed of multiple components. Before the faceted mirrors 18 and 19 are used in the microlithography projection exposure apparatus, the protective layer structure 36 is removed, allowing the EUV mirror component 40 to obtain its final state, as shown. Figure 8 As shown.

[0071] Figure 9 An alternative exemplary embodiment is indicated, wherein the multilayer system 31 is applied only after the substrate body 37 has been properly structured. A protective layer structure 36 protecting the optical surfaces and sides of the EUV mirror component 40 is applied to the multilayer system 31.

[0072] Reference Figure 10 An exemplary embodiment of the protective layer structure 36 according to the present invention is illustrated. The sequence of adding and removing layers on the surface of the mirror body is shown above the schematic timeline arrow T. In the first step, a carbon layer with a thickness between 2 nm and 5 nm is applied to the top layer 33 of the multilayer system 31 by vapor deposition. In the sense of the present invention, the carbon layer forms a sacrificial layer 34.

[0073] The subsequent steps for applying the protective layer 35 are performed in another processing chamber. There, during transport, the EUV reflector in the exemplary embodiment shown is exposed to an oxygen-containing atmosphere, which has the effect of allowing the sacrificial layer 34 to oxidize and for impurities to deposit. Figure 10 A corresponding contamination layer 41 on the sacrificial layer 34 is shown. Other exemplary embodiments exist without such a contamination layer.

[0074] A protective layer 35 is applied to the contaminated layer 41. In this exemplary embodiment, the protective layer 35 is formed by a protective varnish applied by spin coating. The thickness of the protective varnish is 1 μm to 10 μm.

[0075] The photoresist 42 is then applied to the protective layer 35 again by spin coating. The photoresist 42 can be selectively exposed to define areas for subsequent structuring.

[0076] Before the EUV mirror is used in the projection exposure apparatus, the layers are removed sequentially again until the top layer of the multilayer system 31 is exposed. First, the photoresist 42 and protective varnish 35 are removed using a wet chemical method with a solvent. The sacrificial layer 34, made of carbon, is not eroded by the solvent. If the sacrificial layer is not sensitive to oxygen plasma, the contaminant layer 41 is removed by exposing the surface of the EUV mirror to oxygen plasma. Only when the EUV mirror has been installed in the projection exposure apparatus is the sacrificial layer 34 removed by exposing the surface of the EUV mirror to hydrogen plasma. Subsequently, the projection exposure apparatus with the EUV mirror is ready for use.

[0077] The carbon material of the sacrificial layer 34 has a lower surface energy than metals, thus good coverage of the multilayer system 31 by the top layer 33 can be expected. This facilitates the removal of the sacrificial layer 34 from the top layer 33 without residue. The wet chemical process used to remove the photoresist 42 and the protective layer 35 helps to remove particles and contaminants on and within the layers. Since only chemical processes are used to remove the layers without physical etching processes, the material removal is highly selective.

[0078] According to Figure 11 In an exemplary embodiment, the sacrificial layer 34 is fabricated by oxidation of the top layer 33 of the multilayer system 31. An oxide layer with a thickness of several nanometers is formed. A protective layer 35 made of silicon dioxide with a thickness between 100 nm and 300 nm is applied to the oxide layer 34 by vapor deposition. During subsequent storage of the EUV mirror, a contamination layer 41 may form on the protective layer 35. A photoresist 42 for structuring the surface is applied to the contamination layer 41 by spin coating. Again, the thickness of the photoresist layer is between 1 μm and 10 μm.

[0079] These layers are removed before the EUV mirror is used in the projection exposure equipment. Again, the photoresist 42 is removed using a solvent. The contaminant layer 41 is removed by applying oxygen plasma. The protective layer made of silicon dioxide can be removed by using HF vapor etching. For example, hydrogen plasma can be applied to remove the oxide layer forming the sacrificial layer 34. Alternatively, the sacrificial layer can be removed by physical sputtering (e.g., inert gas plasma) or by applying HF vapor etching.

[0080] The advantage of this exemplary embodiment is that it eliminates the need for a separate deposition of the sacrificial layer 34. The multilayer system 31 is preserved by removing the protective layer structure 36 using a dry chemical method. Contaminants and particles on and within the layers can be reliably removed by applying HF vapor etching to remove the protective layer 35. The separation of functional groups is facilitated by using complementary deposition and removal methods. Potentially incomplete removal of the sacrificial layer 34 is acceptable because small residues of oxide on the top layer 33 do not significantly impair the reflectivity of the multilayer system 31 to EUV radiation.

Claims

1. A method of manufacturing EUV reflector components (M1-M6, 40), wherein a multilayer system (31) is applied to the surface of a reflector body substrate (30, 37) to form an optical surface highly reflective to EUV radiation, wherein a temporary protective layer structure (36) is manufactured on the multilayer system (31), wherein the protective layer structure (36) comprises a protective layer (35) and a sacrificial layer (34) disposed between the protective layer (35) and the multilayer system (31), and wherein the temporary protective layer structure (36) is removed before the EUV reflector component is put into use, wherein the sacrificial layer (34) is a layer manufactured by oxidizing the layers of the multilayer system (31).

2. The method according to claim 1, wherein, The multilayer system (31) includes a top layer (33) which is made of a different material than the lower alternating layers (32) of the multilayer structure (31).

3. The method according to claim 1 or 2, wherein, The sacrificial layer (34) is a layer applied to the multilayer system (31).

4. The method according to claim 3, wherein, The sacrificial layer (34) is a carbon layer.

5. The method according to claim 4, wherein, The thickness of the carbon layer is between 1 nm and 30 nm, preferably between 2 nm and 5 nm.

6. The method according to claim 1 or 2, wherein, The sacrificial layer (34) is a layer manufactured by oxidation of the layers of the multilayer system (31).

7. The method according to any one of claims 1 to 6, wherein, The protective layer (35) is applied as a protective coating.

8. The method according to claim 7, wherein, The protective coating is a photoresist.

9. The method according to any one of claims 1 to 6, wherein, The protective layer (35) is formed of silicon dioxide.

10. The method according to any one of claims 1 to 9, wherein, The temperature during the removal of the protective layer structure (36) shall not exceed 350°C.

11. The method according to any one of claims 1 to 10, wherein, The EUV reflector components (M1-M6, 40) undergo a processing step in which material is removed from the multilayer structure (31) and / or from the reflector body substrate (37) after the temporary protective layer structure (36) is manufactured and before the temporary protective layer structure (36) is removed.

12. The method according to claim 11, wherein, The surface, which is completely covered by the multi-layer system (31), is subdivided into multiple mirror elements (40).

13. An EUV reflector component intermediate product having a multilayer system (31) applied to the surface of a reflector body substrate (30, 37) and forming an optical surface highly reflective to EUV radiation, wherein a temporary protective layer structure (36) is disposed on the multilayer system (31), wherein the protective layer structure (36) comprises a protective layer (35) and a sacrificial layer (34) disposed between the protective layer (35) and the multilayer system (31), and wherein the sacrificial layer (34) is a layer manufactured by oxidation of the layers of the multilayer system (31).

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