Method of manufacturing a surface coating reflecting EUV radiation

Abstract

The invention relates to a method for producing a surface coating (200) that reflects EUV radiation on a substrate (300), wherein the surface coating (200) comprises a multilayer layer system (210) and the substrate (300) has a microelectromechanical system on the face on which the surface coating (200) is to be arranged. The method has the following steps: a) producing the surface coating (200) on a carrier (100) in the reverse order to the layers of the multilayer layer system (210); b) connecting the produced surface coating (200) to the substrate (300) on the face facing away from the carrier (100); and c) releasing and removing the carrier (100) from the surface coating (300).

Description

[0001] This patent application claims priority to German patent application DE 10 2023 211 114.4, filed on November 10, 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 an EUV radiation reflective surface coating, and particularly to a method for EUV lithography. Background Technology

[0003] Photolithography is used to fabricate microstructured components, such as integrated circuits. The projection exposure equipment used in this process includes an illumination system and a projection system. Using the projection system, an image of a mask (also called a mask master) illuminated by the illumination system is projected onto a substrate (such as a silicon wafer) to reduce the size of the former. The substrate is coated with a photosensitive layer and arranged in the image plane of the projection system so as to transfer the mask structure onto the photosensitive coating of the substrate.

[0004] In projection exposure equipment operating within the EUV range, various optical elements in the exposure and projection systems are configured as mirrors with reflective surfaces. Since the wavelength of EUV exposure radiation ranges from 5 nm to 30 nm, the effective optical surface of individual elements should be equipped with a multi-layer system to achieve the desired reflectivity.

[0005] Furthermore, illumination systems, particularly in projection exposure equipment designed for the EUV range, typically include two faceted mirrors arranged in the beam path between the actual exposure radiation source and the mask to be illuminated. The faceted mirror closer to the exposure radiation source in the beam path is usually called a field faceted mirror, while the other faceted mirror is called a pupil faceted mirror.

[0006] In order to produce different intensity and / or incident angle distributions during mask illumination, it is known that at least one of the facets of two faceted mirrors—particularly the facets of a field faceted mirror—is formed by one or more individually electromechanically pivotable micromirrors. The same is disclosed, for example, in WO 2012 / 130768 A2. Each of these micromirrors should also be provided with a reflective coating.

[0007] The multilayered systems required for the desired reflectivity are inherently sensitive and, once fabricated on the surface of the optical element intended for this purpose, may be damaged during subsequent manufacturing steps necessary to complete the optical element, rendering it unusable or requiring costly reprocessing. The risk of damage is particularly high in the case of micromirror devices, as micromirrors are typically in the form of microelectromechanical systems (MEMS), which combine micromechanical structures and electronic components on a single chip.

[0008] In the completed state, the micromirrors of the corresponding system can pivot about two axes relative to the base. In this case, a sufficient number of actuators and sensors are provided to enable the mirror elements to pivot precisely about these axes independently and to allow monitoring of this pivoting. To apply the multilayer system with the required precision, the base structure of each individual micromirror should still be fixed and not pivotable; in this case, the steps required to release the micromirrors or allow them to pivot could damage the multilayer system already applied to the base structure. Summary of the Invention

[0009] The problem addressed by this invention is to develop an improved method for manufacturing EUV radiation reflective surface coatings, which relates to existing technologies.

[0010] This problem is solved by the method described in claim 1. The dependent claims relate to advantageous improvements.

[0011] Therefore, the present invention relates to a method for fabricating an EUV radiation-reflective surface coating on a substrate, wherein the surface coating comprises a multilayer system, and the substrate comprises a microelectromechanical system on the side on which the surface coating is to be applied, the method comprising the following steps:

[0012] a) Create a surface coating on a carrier in the reverse order of the layers in a multilayer system;

[0013] b) Attach the manufactured surface coating to the substrate on the side away from the carrier; and

[0014] c) Separate and remove the carrier from the surface coating.

[0015] This invention is based on the understanding that, during the prior art manufacturing of multiple optical elements for EUV applications, the required multilayer system for reflecting EUV radiation must be applied in the early stages of the manufacturing process, making the multilayer system susceptible to damage by subsequent manufacturing steps associated with the optical element. This includes not only the machining of the optical element during manufacturing (which also directly affects the already applied multilayer system, such as the separation of a coated substrate), but also processes in which required process gases (e.g., those required for etching) may come into contact with the multilayer system (even unintentionally) and potentially damage it. This invention provides new possibilities for manufacturing optical elements with corresponding surface coatings that are not feasible in the prior art. The invention provides a final substrate surface coating comprising a suitable multilayer system, which is first manufactured separately from the substrate on a carrier, then applied as a whole to the substrate, followed by removal of the carrier, resulting in a substrate with the surface coating. Since the method of manufacturing an EUV radiation reflective surface coating on a substrate according to the present invention can typically be applied at a later stage in the manufacturing process of optical elements than during the direct manufacturing of multilayer systems on a substrate according to the prior art, the risk of damage due to subsequent manufacturing steps can be reduced or even completely avoided.

[0016] To ensure that the multilayer system actually forms the desired surface coating on the substrate at the end of the process, the individual layers of the multilayer system should be fabricated on the carrier in reverse order. When the surface coating of the substrate is attached to the carrier, the layer closest to the carrier forms the outer layer of the surface coating in the finished state. Conversely, when the multilayer system is arranged on the carrier, the exposed layers of the multilayer system are used to connect to the substrate, and therefore are the layers closest to the substrate in the finished state.

[0017] If the surface coating is arranged on the carrier in the opposite direction to the layers of the multilayer system, then in the next step, the exposed side of the surface coating away from the carrier can be connected to the substrate, which is the ultimate goal of the surface coating.

[0018] Finally, the carrier is still removed to expose the surface coating disposed on the substrate, thereby effectively obtaining the desired reflectivity of the substrate in the surface coating area.

[0019] It is possible that the surface coating is initially constructed on an initial carrier or initial substrate using layers of a multilayer system in a "normal" sequence. Subsequently, before the initial carrier or initial substrate is removed in a suitable manner, the surface coating thus constructed is fixed "inverted" onto the carrier according to the invention. The advantage of manufacturing the surface coating on the carrier in this reverse manner using a multilayer system is that manufacturing methods for the corresponding multilayer systems, which are generally known and proven, can be employed. In particular, this also applies to layers arranged adjacent to the carrier while fixed to it and located outside the substrate after the carrier has been removed; this means that known production methods can be used to ensure the surface quality of said layers.

[0020] However, it is preferable to fabricate the surface coating layer by layer on the carrier, i.e., the individual layers of the multilayer system are applied sequentially and in reverse to the carrier. In this case, the initial carrier or initial substrate can be omitted, which also means that the possible steps for removing these components, which are only required at the beginning, are also eliminated. In principle, methods known in the prior art for manufacturing multilayer systems can also be used in this case.

[0021] To achieve a sufficiently high surface quality for the outer layers of a multilayer system in its finished state, it is preferable to ensure a high surface quality of the carrier through suitable processing, where the layer in question initially rests on the carrier during the fabrication of the surface coating. A high surface quality of the carrier is desirable, particularly when the surface coating is achieved by applying individual layers of the multilayer system layer by layer onto the carrier itself, since the surface of the carrier can be imprinted in a manner comparable to a negative—at least in the layers of the multilayer system arranged adjacent to the carrier. Therefore, it is preferable to process the surface of the carrier by applying a smoothing layer, polishing, and / or cleaning. Methods for polishing and cleaning the surface do not require further explanation. Rather, those skilled in the art can readily determine polishing and cleaning methods suitable for the carrier or its material, and can also verify the results of these methods if necessary. If the carrier or its material itself is not suitable for processing that results in the desired high surface quality, it may be advantageous to apply a smoothing layer to the carrier. This smoothing layer is one that provides the desired surface quality immediately upon application, or—potentially different from the carrier or its material itself—can be processed by suitable methods (e.g., polishing and / or cleaning) to produce the desired surface quality. Independent of the potential provision and optional use of a smoothing layer, and preferably, the carrier surface in the region provided for the surface coating has a root mean square roughness of 0.2 nm RMS or less and / or is free of foreign particles larger than 5 μm, preferably larger than 1 μm. Suitable methods and equipment for checking conformity to the relevant specifications are known.

[0022] To facilitate the separation and removal of the carrier from the surface coating after it has been applied to the substrate, a separation layer can be present between the carrier and the surface coating, on which the carrier can be separated from the surface coating more easily and in a non-destructive manner. If the surface coating is applied directly to the surface of the carrier or possibly a smoothing layer, the surface coating may be difficult to separate, depending on the materials of the coating and the carrier or smoothing layer, thus posing a risk of damaging the surface coating when the carrier separates. In particular, in this case, a separation layer can reduce or completely eliminate the risk of damaging the surface coating. In this case, the separation layer can be designed so that it can be easily separated from the carrier or from the surface coating, at least in the latter case without damaging the surface coating. Alternatively, the separation layer can also be designed so that destruction of its own structure enables separation of the carrier and the surface coating. In this case, any separation layer residue remaining on the surface coating, or the complete separation layer after separation from the carrier, still needs to be removed from the surface coating, either directly or at a later stage. When the separation layer is applied to the carrier, it can be in the form of a single layer made of a suitable material; however, the separation layer can also be formed on the surface of the carrier itself through a chemical reaction. For example, if the carrier is made of silicon, the separation layer can be made of silicon oxide, which forms directly on the surface of the carrier when it comes into contact with air.

[0023] Preferably, a protective layer is provided between the carrier and the surface coating, and the protective layer remains on the surface coating after the carrier has been separated and removed from the surface coating, and is only removed from the surface coating at a later stage. The corresponding protective layer is capable of protecting the surface coating during method steps following the method according to the invention in the manufacture of the optical element or its installation (e.g., in a projection exposure apparatus). In this case, the protective layer should be configured such that it can be easily removed from the surface coating at a later stage, thereby exposing the actual surface coating with reflective properties. In this case, removing the protective layer should not damage the surface coating.

[0024] If the substrate on which the surface coating is to be applied has a structured structure, i.e., it is particularly discontinuous, then it may be advantageous if the surface coating on the carrier has been subdivided into regions that match the structured structure of the substrate. For example, if adjacent micromirrors of a micromirror unit are to be provided with surface coatings, then the surface coatings for individual micromirrors can be provided as separate portions of the surface coating on a common carrier and can be transferred together to the substrate or the individual micromirrors.

[0025] To achieve this, prior to applying the surface coating, the surface of the carrier may include a structure adapted to the surface of the substrate such that the surface coating to be applied thereto is formed in a manner suitable for attachment to the substrate only in predetermined areas. In other words, the surface of the carrier may include, for example, recessed areas where no surface coating is formed at all, or any possible surface coating that is recessed to such an extent that it is not attached to the substrate when the non-recessed areas are attached, and in particular, it is removed along with the carrier in one of subsequent steps.

[0026] In particular, when surface coatings are manufactured layer by layer on a carrier, it is preferable to configure the structural edges in the structured structure of the carrier surface as overhangs. Since the surface area of ​​the carrier to which the surface coating is to be applied forms an angle greater than 90°, preferably greater than 120°, with the sidewalls defining these surface areas, each edge has an overhang structure. Even when surface coatings are produced layer by layer on the carrier, the clear definition of individual areas with surface coatings can be ensured periodically, as the risk of closed edges is minimized.

[0027] As an alternative to creating a directly structured surface coating by appropriately structuring the carrier before fabricating the surface coating on it, the surface coating and / or top side of the carrier can also be structured after the surface coating is fabricated to fit the surface of the substrate. For example, this allows the surface coating, which is initially fabricated in a continuous manner, to be divided into appropriate regions and thus structured using sawing or milling methods.

[0028] One possibility is that the surface coating is integrally bonded to the substrate, thus attaching the surface coating to the substrate. For this purpose, suitable adhesive materials may be used if necessary. Alternatively, the surface coating can be attached to the substrate by adding it to a surface coating fabricated on a carrier, wherein the functional layer can be applied to the side of the substrate opposite to the surface coating.

[0029] Once an EUV radiation reflective surface coating has been fabricated on a substrate according to the present invention, the substrate can be or become curved. For example, this can be done by applying prestress to it in such a way that the shape of the substrate changes when the carrier is removed, and in particular, the shape of the surface of the substrate with the surface coating also changes. Alternatively, after the surface coating has been fabricated on the substrate, other known methods can be used to bend the substrate.

[0030] Spacers used to reduce the contact area between the substrate and the arched assembly can be disposed on the side of the substrate facing away from the surface coating. Reducing the contact area also reduces the risk of the arched component introducing stress into the substrate and / or its surface coating.

[0031] Multilayer systems are preferably designed to reflect radiation with wavelengths from 1 to 20 nm, preferably 13.5 nm. Such multilayer systems are known from the prior art and typically comprise alternating layers of molybdenum and silicon.

[0032] The substrate includes a microelectromechanical system (MEMS) on the side of the substrate to which a surface coating is to be applied. In this case, the MEMS may include micromirrors, particularly micromirrors used in devices for semiconductor technology.

[0033] In this context, "equipment for semiconductor technology" refers to any equipment that can be used to manufacture or test parts of microstructure components or components needed for this purpose. This specifically covers inspection equipment and metrology systems, in addition to photolithography projection exposure equipment. In the case of inspection equipment for masks or wafers, the variability of illumination can be increased, for example by means of one or more MEMS micromirror units, which can result in higher contrast or entirely new image representations of the mask or wafer surface, thus being advantageous for mask or wafer inspection. The same applies to metrology systems that can be used to measure masks, wafers, or any other optical elements (especially mirrors), where increased variability of illumination can improve measurement results. Attached Figure Description

[0034] The invention will now be described by way of example with reference to the accompanying drawings, in which:

[0035] Figure 1 : A schematic diagram of a photolithography projection exposure apparatus is shown, which includes optical elements having a reflective surface coating manufactured according to the present invention;

[0036] Figure 2 : A schematic diagram illustrating a first exemplary embodiment of a method for manufacturing a surface coating on a carrier;

[0037] Figure 3 : A schematic diagram illustrating a second exemplary embodiment of a method for manufacturing a surface coating on a carrier;

[0038] Figure 4 : A schematic diagram illustrating a first exemplary embodiment of a method for attaching a surface coating to a substrate and removing a carrier;

[0039] Figure 5 : A schematic diagram illustrating a second exemplary embodiment of a method for attaching a surface coating to a substrate and removing a carrier;

[0040] Figure 6 : A schematic diagram illustrating an embodiment variation of the method according to the invention for structured substrates; and

[0041] Figure 7: A schematic diagram of an embodiment variant having a curved substrate surface in the finished state is shown. Detailed Implementation

[0042] Figure 1 A schematic meridional section is shown passing through a photolithography projection exposure apparatus 1, an example of semiconductor technology equipment. In this case, the projection exposure apparatus 1 includes an illumination system 10 and a projection system 20.

[0043] The illumination system 10 illuminates the object field 11 in the object plane or mask master plane 12. For this purpose, the illumination system 10 includes an exposure radiation source 13, which, in the illustrated exemplary embodiment, emits illumination radiation containing light in the EUV range, specifically having wavelengths between 5 nm and 30 nm. The exposure radiation source 13 can be a plasma source, such as an LPP (laser-generated plasma) source or a GDPP (gas discharge-generated plasma) source. It can also be a synchrotron-based radiation source. The exposure radiation source 13 can also be a free-electron laser (FEL).

[0044] The illumination radiation emitted from the exposure radiation source 13 is initially focused into the concentrator 14. The concentrator 14 may be a concentrator having one or more elliptical and / or hyperboloidal reflective surfaces. The illumination radiation may be incident on at least one reflective surface of the concentrator 14 at grazing incidence (GI) (i.e., at an angle of incidence greater than 45°) or normal incidence (NI) (i.e., at an angle of incidence less than 45°). The concentrator 14 may be structured and / or coated, on the one hand to optimize its reflectivity to the radiation used, and on the other hand to suppress intrusive light.

[0045] Downstream of the light collector 14, illumination radiation propagates through the intermediate focal point in the intermediate focal plane 15. If the illumination system 10 is constructed with a modular design, the intermediate focal plane 15 can, in principle, be used to separate (including structurally separate) the illumination system 10 into a radiation source module and an illumination optics unit 16, described below, which includes an exposure radiation source 13 and a light collector 14. In the case of such separation, the radiation source module and the illumination optics unit 16 together form the modularly constructed illumination system 10.

[0046] The illumination optical unit 16 includes a deflector 17. The deflector 17 may be a planar deflector, or alternatively a mirror with a beam-affecting effect beyond a pure deflection effect. Alternatively or additionally, the deflector 17 may be implemented as a spectral filter that separates the wavelength of the illumination radiation used from the incoming light having a wavelength that deviates from it.

[0047] The deflector 17 is used to deflect the radiation emitted from the exposure radiation source 13 to the first facet mirror 18. If, as in the present case, the first facet mirror 18 is arranged in the plane of the illumination optics unit 16 that is optically conjugate to the mask master plane 12 as the field plane, then the facet mirror is also called a field facet mirror.

[0048] The first faceted mirror 18 includes a plurality of micromirrors 18', each of which can be individually pivoted about two mutually perpendicular axes to controllably shape the facets. Each facet is preferably provided with an orientation sensor (not shown) for determining the orientation of the micromirror 18'. Thus, the first faceted mirror 18 is a MEMS device, as described, for example, in DE 102008 009 600 A1.

[0049] The second faceted mirror 19 is arranged downstream of the first faceted mirror 18 in the beam path of the illumination optics unit 16, resulting in a double-faceted system, the basic principle of which is also called a fly-eye integrator. If the second faceted mirror 19 (as in the illustrated exemplary embodiment) is arranged in the pupil plane of the illumination optics unit 16, it is also called a pupil faceted mirror. However, the second faceted mirror 19 may also be arranged at a distance from the pupil plane of the illumination optics unit 16, thus the specular reflector is produced by a combination of the first and second faceted mirrors 18, 19, as described, for example, in US 2006 / 0132747 A1, EP1 614 008 B1, and US 6,573,978.

[0050] The second faceted mirror 19 does not, in principle, need to be composed of pivotable micromirrors. Instead, it may comprise individual facets formed by a single mirror or a manageable number of mirrors significantly larger than micromirrors, which are stationary or tiltable only between two defined end positions. However, as shown, the second faceted mirror 19 may also provide a microelectromechanical system with multiple micromirrors 19', each of which can individually pivot about two mutually perpendicular axes, and each micromirror 19' preferably includes an orientation sensor.

[0051] The individual facets of the first faceted mirror 18 are imaged into the object field 11 by means of the second faceted mirror 19, which is typically only an approximate image. The second faceted mirror 19 may be the final beam-shaping mirror, or in fact the final mirror reflecting the illumination radiation in the beam path upstream of the object field 11.

[0052] In each case, one of the facets of the second facet mirror 19 can be assigned to one of the facets of the first facet mirror 18 for the purpose of forming an illumination channel for the illumination field 11. This can in particular lead to illumination according to Köhler's principle.

[0053] To illuminate the object field 11, the facets of the first faceted mirror 18 are imaged by overlapping the corresponding facets of the second faceted mirror 19. Here, the illumination of the object field 11 is made as uniform as possible. Preferably, it has a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

[0054] By selecting the final illumination channel used (which may not be a problem due to the proper setting of the micromirrors 18' of the first faceted mirror 18), it is still possible to set the intensity distribution in the entrance pupil of the projection system 20, as described below. This intensity distribution is also referred to as the illumination setting. Incidentally, it may be advantageous here to arrange the second faceted mirror 19 imprecisely in a plane optically conjugate with the pupil plane of the projection system 20. In particular, the pupil faceted mirror 19 may be arranged tilted relative to the pupil plane of the projection system 20, for example, as described in DE 10 2017 220 586 A1.

[0055] However, in such Figure 1 In the arrangement of the components of the illumination optical unit 16 described herein, the second faceted mirror 19 is arranged in the region conjugate with the entrance pupil of the projection system 20. The deflecting mirror 17 and the two faceted mirrors 18, 19 are arranged to be tilted relative to the object plane 12 and relative to each other in each case.

[0056] In an alternative embodiment (not shown) of the illumination optics unit 16, a transmission optics unit including one or more mirrors may be additionally provided in the beam path between the second faceted mirror 19 and the object field 11. The transmission optics unit may specifically include one or two normal incident mirrors (NI mirrors) and / or one or two grazing incident mirrors (GI mirrors). Using the additional transmission optics unit, different orientations of the incident pupils for the tangential and sagittal beam paths of the projection system 20 described below can be particularly considered.

[0057] Alternatively, it can be omitted. Figure 1 The deflector 17 shown is for this purpose, and the faceted mirrors 18 and 19 should be properly arranged relative to the radiation source 13 and the light collector 14.

[0058] With the aid of the projection system 20, the object field 11 in the mask master plane 12 is transferred to the image field 21 in the image plane 22.

[0059] For this purpose, the projection system 20 includes a plurality of mirrors Mi, which are sequentially numbered according to their arrangement in the beam path of the projection exposure device 1.

[0060] exist Figure 1In the example shown, projection system 20 includes six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or any other number of mirrors M1 are also possible. The penultimate mirror M5 and the last mirror M6 each have a channel opening for illumination radiation, thus the projection system 20 shown is a double-shielded optical unit. Projection system 20 has an image-side numerical aperture greater than 0.3, but can also be greater than 0.6, for example, 0.7 or 0.75.

[0061] Mirror M i The reflecting surface can be a free-form surface without an axis of rotational symmetry. However, the reflecting mirror M... i The reflective surface can also be alternatively designed as an aspherical surface with exactly one axis of rotational symmetry of its shape. Just like the reflector in illumination optics unit 16, reflector M... i It may also have a reflective coating for illumination radiation. These reflective coatings can be designed as multilayer coatings, especially with alternating layers of molybdenum and silicon.

[0062] The projection system 20 has a large object-image offset in the y-direction between the y-coordinate of the center of the object field 11 and the y-coordinate of the center of the image field 21. This object-image offset in the y-direction can have approximately the same magnitude as the z-distance between the object plane 12 and the image plane 22.

[0063] Specifically, the projection system 20 can be designed to be modified, i.e., it has different imaging ratios βx and βy in the x and y directions, respectively. The two imaging ratios βx and βy of the projection system 20 are preferably (βx, βy) = (+ / -0.25, / +-0.125). An imaging ratio β of 0.25 corresponds to a reduction with a ratio of 4:1, while an imaging ratio β of 0.125 results in a reduction with a ratio of 8:1. A positive sign in the case of the imaging ratio β indicates imaging without image inversion; a negative sign indicates imaging with image inversion.

[0064] Other imaging scales are also possible. Imaging scales βx and βy with the same sign and size in the x and y directions are also possible.

[0065] The number of intermediate image planes in the x and y directions along the beam path between object field 11 and image field 21 may be the same or different, depending on the embodiment of projection system 20. Examples of projection systems 20 with different numbers of such intermediate images in the x and y directions are known from US 2018 / 0074303 A1.

[0066] Specifically, the projection system 20 may include concentric entrance pupils. This may be accessible. However, it may also be inaccessible.

[0067] A mask master 30 (also referred to as a mask), arranged in the object field 11, is exposed by the illumination system 10 and transferred onto the image plane 21 by the projection system 20. The mask master 30 is held by a mask master holder 31. The mask master holder 31 can be displaced in the scanning direction, in particular, by a mask master displacement driver 32. In the exemplary embodiment shown, the scanning direction extends in the y-direction.

[0068] The structure on the mask master 30 is imaged onto the photosensitive layer of the wafer 35, which is located in the image field 21 of the image plane 22. The wafer 35 is held by a wafer holder 36. The wafer holder 36 can be moved, particularly along the y-direction, by a wafer displacement driver 37. The displacement of the mask master 30, first by the mask master displacement driver 32, and the displacement of the wafer 35, secondly by the wafer displacement driver 37, can be synchronized with each other.

[0069] exist Figure 1 In the projection exposure apparatus 1 or its illumination system 10 shown, the above description essentially reflects known prior art. Various optical elements reflecting EUV exposure radiation—namely, the mirrors or micromirrors 17, 18', 19' of the exposure system 10 and the mirrors M1 to M6 of the projection system 20—are provided with a surface coating 200 that reflects radiation with wavelengths from 1 to 20 nm and is applied to a substrate 300 that at least partially forms the structure of the respective optical element. In this case, the surface coating 200 comprises a multilayer system 210 made of alternating layers of silicon and molybdenum.

[0070] In this case, at least some of the surface coatings 200 of optical elements 17, 18', 19', M1 to M6 have been applied to the respective substrates 300 using the method according to the invention. The following will be based on... Figures 2 to 7 Various embodiments of the method according to the invention will be explained in more detail.

[0071] The method according to the invention is characterized in that the surface coating 200 for the substrate 300 is initially fabricated integrally on the carrier 100 and then subsequently transferred to the substrate 300.

[0072] A first exemplary embodiment of the method according to the invention, particularly the fabrication of a surface coating 200 on a carrier 100, is illustrated by way of example. Figure 2 Depicted in ae.

[0073] From its surface, the carrier 100 ( Figure 2 a) Initially, a smooth layer 110 with a surface having a root mean square roughness of less than 0.2 μm can be applied to the side facing away from the carrier 100. Figure 2b). The smoothing layer 110 prevents the surface structure of the carrier 100 (even only at the microscale) from being transferred to the surface coating 200 directly or through other possible intermediate layers (such as the separation layer 120 and the protective layer 130 explained below), and prevents subsequent outer surfaces of the surface coating 200 from having a negative structure of the surface structure of the carrier 100. The smoothing layer 110 can have the desired low roughness immediately after application, such as after curing from a fluid state, or due to subsequent processing (such as polishing).

[0074] If the carrier 100 already inherently has a suitably low roughness, or if a suitably low roughness can be achieved through a surface treatment such as polishing, then the smoothing layer 110 can be omitted. However, for clarity, the smoothing layer 110 is shown below as an optional layer only.

[0075] First, separate layer 120 ( Figure 2 c) Apply to the smoothing layer 110 (or directly to the carrier 100), and then apply the protective layer 130. Figure 2 d). In this case, the separation layer 120 is configured to adapt to the protective layer 130, such that the two layers 120, 130 can be easily separated from each other. The subsequent separation of layers 120, 130 should, in principle, be achieved in such a way that the protective layer 130 and other surrounding layers (e.g., in particular the surface coating 200) are not adversely affected by the separation. If separation is achieved solely by applying appropriate tensile force, the force required to untie the connection between the separation layer 120 and the protective layer 130 should be significantly less than the force required to separate other layers from each other—particularly the layers of the multilayer system 210 in the surface coating 200. If the separation of the separation layer 120 from the protective layer 130 is caused or assisted by the use of chemicals and / or specific environmental conditions (e.g., certain temperatures), it must be ensured that the surrounding layers and, in particular, the surface coating 200, are not damaged by these chemicals and / or environmental conditions.

[0076] The protective layer 130 is suitably configured such that it can be removed at a later stage (particularly after the method according to the invention has been completed) without residue. If the protective layer 130 is removed by chemical means, it should be configured such that the chemicals required for removal do not corrode the surrounding layers and structures—particularly the surface coating 200.

[0077] Both the separation layer 120 and the protective layer 130 are optional. For example, if, as described below, the carrier 100 can be separated and removed from the surface coating 200 without damage, even without the corresponding layer, then the separation layer 120 is unnecessary, for example, because the protective layer 130, applied directly to the smoothing layer 110, can be easily separated from the smoothing layer 110. Specifically, the protective layer 130 can be omitted in those processes where the corresponding protective layer 130 must be removed almost immediately after the carrier 100 is separated and removed from the surface coating 200, as described below. In this case, omitting the protective layer 130 avoids the additional process steps required for removing the protective layer 130 and may not significantly increase the risk of damage to the surface coating 200.

[0078] Subsequently, a surface coating 200 is formed on the protective layer 130. For this purpose, individual layers of the multilayer system 210 are formed sequentially, as indicated by arrow 90. In this case, the order of the layers in the multilayer system 210 is the reverse of the order required in the subsequent surface coating 200 of the substrate 300. In the state after transfer to the substrate 300, the layer of the multilayer system 210 immediately adjacent to the protective layer 130 is the outer layer of the exposed surface forming the surface coating 200.

[0079] Figure 3 It shows Figure 2 An alternative procedure to the method steps shown for manufacturing a surface coating 200 on a carrier 100.

[0080] From carrier 100 ( Figure 3 a) Initially, as a result of contact with air or chemicals, the separation layer 120 is formed directly on the carrier 100. Figure 3 b). In this case, the formation of the release layer 120 is optional. The surface coating 200 is then applied integrally to the carrier 100 or the release layer 120 and thus manufactured. For this purpose, a multilayer system 210 of the surface coating 200 is prepared on the initial substrate 215 using known manufacturing methods and in a "normal" layer sequence, and attached to the carrier 100 or the release layer 120. Figure 3 c). Subsequently, the initial substrate 220 is removed ( Figure 3 d).

[0081] Because in Figure 2 The reason explained in the context can be omitted, and the separation layer 120 can also be omitted. Then, for example, an additional protective layer 130 can also be provided.

[0082] Regardless of how the surface coating 200 or its multilayer system 210 is manufactured on the carrier 100, the surface coating 200 is attached and the carrier 100 is then separated and removed, as shown in the following reference. Figure 4 and Figure 5 The explanation is as follows: Figure 4 and Figure 5 Alternative procedures are shown for each. For simplicity, it is assumed here that... Figure 2 The surface coating 200 is manufactured, even Figure 4 and Figure 5 The method steps shown can also be directly applied to... Figure 3 The surface coating manufactured.

[0083] In order to attach the manufactured surface coating 200 to the substrate 300 in the area of ​​the substrate 300 where the surface coating is to be provided, the surface coating 200 still on the carrier 100 is brought closer to the substrate 300 with the side away from the carrier 100 as the leading edge. Figure 4 a), and integrally integrated into substrate 300 ( Figure 4 b).

[0084] Subsequently, the carrier 100 is separated from the surface coating 200, wherein, in the exemplary embodiment shown, separation occurs between the separation layer 120 and the protective layer 130. Figure 4 c). The protective layer 130 is initially retained on the surface coating 200 and is removed only at a later stage, particularly even only after the method according to the invention has been completed. Figure 4 d). As a result of the protective layer 130, the surface coating 200 can be protected from damage, wherein, in this case, the protective layer 130 should also be removed without damaging the surface coating 200.

[0085] Incidentally, in Figure 4 Arrow 90 is shown in the figure, indicating the order in which the layers of the multilayer system 210 are fabricated on the carrier 100 (see [reference]). Figure 2 and Figure 3 It is immediately apparent that the order on the carrier 100 is the reverse of the order on the substrate 200. Subsequently, the layers on the carrier 100 should therefore be manufactured in the reverse order of the final desired layer order on the substrate 300.

[0086] Figure 5 It shows Figure 4 The process of substitution.

[0087] Starting with a surface coating 200 fabricated on a carrier 100, a substrate 300 is then applied directly onto the surface coating 200. Figure 5 a) For this purpose, a method equivalent to that used for applying the individual layers of a multilayer system 210 for applying the surface coating 200 layer by layer can be employed. In particular, the substrate 300 can therefore also be applied layer by layer. Figure 5 The procedure shown also allows for the provision of a functional layer 310 on the side of the substrate 300 opposite to the surface coating 200. Figure 5The functional layer 310 shown in example a can be designed to measure temperature directly on the substrate 300. However, any other or additional layers, such as the functional layer 310 shown, may be provided.

[0088] Compared with the above method (see Figure 4 The states equivalent to 5b) generally exist after the substrate 300 and possibly other layers (e.g., functional layer 310) have been fully fabricated. Therefore, in order to explain Figure 5 c and Figure 5 d, Referring to the explanation above, especially regarding Figure 4 c and Figure 4 Explanation of d.

[0089] Figure 6 This is a variation of the method according to the invention, used for structuring substrate 300, i.e., for substrate 300 with surface discontinuities to which the surface coating 200 is to be provided. Regarding the projection exposure apparatus 1, as... Figure 1 As shown, the faceted reflectors 18 and 19, whose surfaces are formed by multiple discrete micro-reflectors 18' and 19', can be regarded as a structured substrate 300, wherein the individual reflector surfaces of the micro-reflectors 18' and 19' should each be provided with a surface coating 200.

[0090] in this case, Figure 6 Two possibilities for manufacturing surface coating 200 are shown (see Figure 6 (a, b, left / right), and the method steps of attaching the surface coating 200 to the substrate 300 and removing the carrier 100 after manufacturing can be considered together (see...). Figure 6 ce).

[0091] exist Figure 6 In the procedures shown on the left side of a and 6b, the carrier 100 already has a structured structure 105 with overhanging structural edges that adapt to the surface of the substrate 300—that is, in this case, the shape and arrangement of the micromirrors 18', 19' are already in an initial state (see...). Figure 6 a). During the manufacture of the surface coating, the surface coating 200 is similar to Figure 2 The process illustrated is created only in the area of ​​the structured structure 105, i.e., the layer-by-layer construction of the multilayer system 210. In this case, the overhanging structural edges help avoid undesirable edge effects during the layer-by-layer fabrication of the surface coating 200. The adapted structured structure 105 has a height greater than the thickness of the coating to be applied. This effectively prevents material from the multilayer system 210, which might be applied far from the area that should actually be coated, from growing with the actually desired surface coating 200.

[0092] exist Figure 6In the process shown on the right-hand side of a and 6b, for example according to Figure 2 Or 3, first on carrier 100 ( Figure 6 A continuous surface coating 200 is manufactured on the right-hand side (a), and then structured as needed. For the purpose of structuring, the surface coating 200 can be appropriately sawed or etched, for example, where it is not a problem to structure it into the carrier 100 to reliably separate individual areas of the surface coating 200, as long as the structural integrity of the carrier 100 is still guaranteed in principle.

[0093] Independent of how the surface coating 200 is structured on the carrier 100, which is then attached to the substrate 300 and the carrier is separated and removed (see [link]). Figure 6 (cd). In this case, the structuring of the surface coating 200 ensures that each individual micromirror 18', 19' is provided with a surface coating in a precisely matched manner.

[0094] Apart from the fact that individual micromirrors 18' and 19' are provided with surface coating 200 instead of a continuous structure, this process corresponds to Figure 4 The process of ce, for which please refer to the statements given there for further explanation.

[0095] Figure 6 No smoothing, separation, or protective layers are depicted 110, 120, 130 (see [link]). Figure 2-5 However, it goes without saying that appropriate layers can be provided if needed. For a more detailed explanation of the layers discussed, refer to the statements above.

[0096] Figure 7 A variant of the embodiment is shown, having a substrate 300 that is bent in its final state.

[0097] Even if the substrate 300 is bent in the final state (see...) Figure 7 b) When the substrate 300 is in a flat state (see...) Figure 7 a) Apply a surface coating 200 manufactured on the flat carrier 100 in any desired manner (see in particular) Figure 2 and 3 Whether this flatness of the substrate 300 is achieved solely through contact with the surface coating 200 still located on the carrier 100 (e.g., due to the elastic deformation of the substrate 200) or is ensured by other measures is irrelevant.

[0098] In any case, after the carrier 100 has been separated and removed, the substrate 300 adopts a curved shape, which is also reproduced by the surface coating 200.

[0099] The substrate 300 can be connected to the upper-level component 400. To avoid affecting the curvature of the substrate 300, or to minimize the impact on the curvature of the substrate 300, the side of the substrate 300 facing away from the surface coating 200 may include spacers 320 for locally defining the connection between the substrate 300 and the component 400. The spacers 320 may be integrally formed with the substrate 300, or may be connected to the substrate 300 as a separate component.

Claims

1. A method for fabricating an EUV radiation reflective surface coating (200) on a substrate (300), wherein the surface coating (200) comprises a multilayer system (210), and the substrate (300) comprises a microelectromechanical system on the side on which the surface coating (200) is to be applied, characterized by the following steps: a) The surface coating (200) is formed on the carrier (100) in the reverse order of the layers in the multilayer system (210); b) Attach the manufactured surface coating (200) to the substrate (300) on the side away from the carrier (100); and c) Separate and remove the carrier (100) from the surface coating (200).

2. The method according to claim 1, Its features are, The surface coating (200) is manufactured layer by layer on the carrier (100).

3. The method according to any one of the preceding claims, Its features are, The surface of the carrier (100) is treated by applying a smoothing layer (110), polishing and / or cleaning, wherein a roughness of 0.2 nm RMS or less is preferably achieved.

4. The method according to any one of the preceding claims, Its features are, The surface of the carrier (100) is treated by applying a smoothing layer (110), polishing and / or cleaning, while ensuring that there are no foreign particles larger than 5 μm, preferably larger than 1 μm.

5. The method according to any one of the preceding claims, Its features are, A separation layer (120) is disposed between the carrier (100) and the surface coating (200), and the separation layer allows the carrier (100) to be separated from the surface coating (200) in a simplified and non-destructive manner.

6. The method according to any one of the preceding claims, Its features are, A protective layer (130) is disposed between the carrier (100) and the surface coating (200), and the protective layer (130) remains on the surface coating (200) after the carrier (100) has been separated from and removed from the surface coating (200), and is only removed at a later stage.

7. The method according to any one of the preceding claims, Its features are, Before the surface coating (200) is applied, the surface of the carrier (100) includes a structured structure (105) adapted to the surface of the substrate (300), such that the surface coating (200) to be applied thereto is formed in a manner suitable for connection to the substrate (300) only in a predetermined area.

8. The method according to claim 6, Its features are, The structural edges in the structured structure (105) of the carrier (100) are configured to be overhanging.

9. The method according to any one of claims 1 to 5, Its features are, After the surface coating (200) is manufactured, the top side of the surface coating (200) and / or the carrier (100) is structured to suitably fit the surface of the substrate (300).

10. The method according to any one of the preceding claims, Its features are, The surface coating (200) is integrally bonded to the substrate (300).

11. The method according to any one of the preceding claims, Its features are, The surface coating (200) is attached to the substrate (300) by additively applying the substrate (200) onto the surface coating (200) manufactured on the carrier (100), wherein preferably a functional layer (310) is applied to the side of the substrate (300) opposite to the surface coating (200).

12. The method according to any one of the preceding claims, Its features are, After the carrier (100) is separated and removed from the surface coating (200), the substrate (300) is bent or becomes bent.

13. The method according to any one of the preceding claims, Its features are, Spacers (320) are provided on the side of the substrate (300) opposite to the surface coating (200).

14. The method according to any one of the preceding claims, Its features are, The multilayer system (210) is designed to reflect radiation with wavelengths of 1 to 20 nm, preferably 13.5 nm.

15. The method according to any one of the preceding claims, Its features are, The microelectromechanical system includes micromirrors (18', 19') on the side of the substrate (300) to which the surface coating (200) is to be applied.

Images