WO2016180609A1

WO2016180609A1 - Method for producing an euv module, euv module and euv lithography system

Info

Publication number: WO2016180609A1
Application number: PCT/EP2016/058672
Authority: WO
Inventors: Andreas SCHMEHL
Original assignee: Carl Zeiss Smt Gmbh
Priority date: 2015-05-12
Filing date: 2016-04-19
Publication date: 2016-11-17
Also published as: EP3295248A1; CN107531581B; TWI685389B; TW201639648A; DE102015208831B4; CN107531581A; DE102015208831A1

Abstract

The invention relates to a method for coating a surface (101) of an EUV submodule (120, 130) of ceramic material (100) that is intended for use in an EUV lithography system (500). Firstly, metallic solder (114) is applied to the surface (101) of the ceramic substrate (100) over its full surface area. Then a thermal treatment is performed for producing a material bond (116) between the ceramic material (100) and the metallic solder (114). The invention also relates to a method for producing an EUV module (200). For this purpose, at least two EUV submodules (120, 130) respectively coated over their full surface area by the method described above are joined by soldering or adhesive bonding. The invention relates furthermore to an EUV submodule (120, 130), to an EUV module (200) and to an EUV lithography system.

Description

Method for producing an EUV module, EUV module and EUV lithography system

Background of the invention The present invention relates to a method for producing an EUV module for an EUV lithography system, to an EUV module and to an EUV lithography system.

Among the methods used for producing semiconductor components are photolithographic methods, in which the structure pattern to be produced is projected with the aid of a mask (reticle) on a reduced scale onto a functional layer coated with a light-sensitive layer and, after development of the photosensitive layer, is transferred into the functional layer by means of an etching process. The production of ever finer structures makes it necessary to use light with ever shorter wavelengths for the lithography process. Current lithography methods therefore work with electromagnetic radiation into the range of extremely ultraviolet light (EUV). The term EUV radiation is used to refer to electromagnetic radiation with wavelengths of between 30 nm and 5 nm, in particular with 13.5 nm. EUV radiation is usually generated by plasma sources or as synchrotron radiation. Since EUV radiation is highly absorbed by most known materials, reflective components are generally used for the projection exposure systems in EUV lithography. Specially designed mirror systems which direct the radiation onto the reticle in a suitable way and subsequently project it onto a desired region of the semiconductor wafer are used for this purpose. The known EUV lithography systems at the same time operate with reflective reticles which either take the form of a reflective carrier layer with a structured absorber layer arranged on it or take the form of an absorbent carrier layer with a structured reflection layer arranged on it.

When imaging the lithographic micro or nano structures onto the wafer surface, it is usually not the entire wafer that is exposed but only a narrow region. Generally, the wafer surfaces are exposed piece by piece or through a slit. This involves both the wafer and the reticle being scanned step by step and moved in parallel or antiparallel in relation to one another. Components used for the projection optical units of EUV lithography systems are made of modern technical ceramics, such as for example silicon carbide (SiC) or silicon-infiltrated silicon carbide (Si: SiC), and are intended in particular for receiving sensors. These materials combine many positive technological characteristics: The great stiffness, which provides advantageous vibrational behaviour, the very good thermal conductivity, the low thermal expansion, which produces great geometrical stability under load, and the low weight. The structure elements are produced from sintered green bodies, which are consolidated by subsequent calcining at high temperatures in the range of 1600°C. The ceramic components thus created are comparatively closed-pored and have a high density. Nevertheless, these ceramic components cannot be used in the untreated state in EUV systems. One reason for this is that even subsequently ground or sandblasted surfaces sometimes have only low strengths and may lead to instances of particle contamination in the EUV lithography system. Moreover, on large ceramic components there are often superficial pores and cracks. Furthermore, free, not fully reacted silicon contaminants on the surfaces of the ceramic components may be dissolved by the hydrogen radicals that are present in the EUV lithography system, produced by H₂ molecules that are split by the EUV radiation, and deposited on the surfaces of the optical elements in the EUV lithography system. This leads to undesired transmission losses. Moreover, the surfaces of the untreated ceramic components generally have very great roughnesses, which make it significantly more difficult for them to be cleaned in a vacuum-compatible manner. For the problematic characteristics of untreated ceramic components mentioned above, also see Figure 1. Figure 1 shows the ceramic substrate 100 with non-critical pores 102 in the volume of the substrate 100 and with critical, partly ground away pores 104 on the substrate surface 101. Moreover, a superficial crack 106 and free silicon 108 can be seen on the substrate surface 101. Particularly critical are weakly bonded regions 110 in the vicinity of the substrate surface 101, since they may become detached and, as freely mobile particles, may impair the function of the EUV lithography system. The aforementioned problematic characteristics of untreated ceramic components are caused by the production process and are unavoidable. This necessitates a surface coating of the ceramic components that binds loose particles, protects elemental silicon that is present from the hydrogen radicals, seals cracks and pores and reduces the surface roughness to such an extent that cleaning processes are possible without any problem. As known from the prior art, shown in Figure 2, for this metallic coatings of nickel-phosphorus alloys (NiP) 112 are applied to the surface 101 of the polished ceramic component 100. The coating is performed for example by galvanic deposition or chemical treatment (chemical nickel). The anchorage of the NiP layer 112 takes place purely mechanically, in that an interlocking engagement is formed by the surface roughnesses. Interlocking connections are produced by means of at least two connection partners engaging in one another. As a result, the connection partners cannot come apart even when there is no force transmission or the force transmission is interrupted. However, the low layer bonding provided by interlocking engagement and the imperfect peripheral zone of the ceramic component limit the forces that can be transmitted via the NiP layer 112 into the ceramic component 100 and the tolerable temperature gradients, such as may occur with adhesive bonds or with soldering or brazing. Thus, the coefficient of expansion of NiP is very different from that of Si:SiC. This has the consequence that galvanically or chemically coated ceramic components cannot be joined by means of adhesive bonding or soldering to form larger subassemblies, and attachment parts, also known as holding components, for holding sensors, can only be attached insufficiently securely to the ceramic component coated with NiP. In order to form larger subassemblies from ceramic components, the joining of a number of components by adhesive bonding or soldering must therefore be performed in the uncoated state, that is to say without the NiP layer. Only after joining are the completely joined ceramic subassemblies as a whole coated with the NiP alloy. However, this entails the problem that the ceramic subassembly composed of a heterogeneous material as a result of the joining can no longer be coated with the NiP alloy with sufficient quality. For example, NiP layers galvanically deposited on adhesive bonds are not able to adhere sufficiently and the adhesives are damaged by the coating.

Metallic solders for connecting ceramic parts to one another have been described many times before. A series of proposals for the production of complex ceramic parts by soldering individual parts have become known. For instance, according to DE 19734211 Al, the ceramic parts to be connected are first metallized and then soldered. The term metallization is used for thermally treated, and consequently cured, metallic solder on the surfaces of the ceramic parts. However, the metallization in this case only takes place at the locations on the ceramic parts that are to be soldered to one another. Sealing of the entire surfaces of the ceramic parts by the metallic solder does not take place.

In the present application, the term "EUV submodule" is used synonymously with the ceramic component, EUV module is used synonymously with the subassembly comprising multiple ceramic components or multiply joined EUV submodules.

In view of the disadvantages described above when joining ceramic components to form subassemblies before the absolutely necessary coating, the object is to provide a method that makes a sufficiently stable connection between the ceramic components possible and at the same time seals the surface of the joined ceramic components. A further object is to provide a subassembly that has the aforementioned positive characteristics.

This object is achieved according to the invention by a method for coating a surface of an EUV submodule of ceramic material that is intended for use in an EUV module of an EUV lithography system. The method according to the invention has at least the following steps: Firstly, metallic solder is applied to the surface of the EUV submodule over its full surface area. Subsequently, a thermal treatment is performed to produce a material bond between the ceramic material and the metallic solder. All connections in which the connection partners are held together by atomic or molecular forces are known as material-bonded connections. They are at the same time unreleasable connections, which can only be separated by destroying the means of connection. The above method has many advantages. On the one hand, the loose particles of the ceramic EUV submodule are bonded and cracks and pores in the ceramic material are sealed. Furthermore, the sealing protects free elemental silicon from the effect of hydrogen radicals. In order to ensure this protection, the metallic solder must be applied to the surface over its full surface area. The main advantage of the method according to the invention is the material bonding. Only this material bonding allows the stable joining of EUV submodule to EUV submodule by means of adhesive bonding or soldering to form an EUV module. Furthermore, the sealing smooths the surface of the EUV submodule. This makes it easier to clean.

In one embodiment, the metallic solder is applied by screen printing, spraying, immersion or spreading. In one embodiment, the thermal treatment is performed in a vacuum at 700°C to 1500°C for 5 min to 60 min. This temperature range and the time of exposure to the thermal energy are particularly advantageous, since a particularly stable material-bonded connection is thereby produced between the metallic solder layer and the ceramic substrate. In one embodiment, a reactive metallic solder is applied as the metallic solder, in particular a silver-copper eutectic with additions of titanium (Ti), manganese (Mn), zirconium (Zr) and/or hafnium (Hf). The thermal treatment is in this case performed at 700°C to 900°C, preferably for 5 min to 10 min. The thermal treatment may be preceded by a drying phase at 100°C to 120°C for 5 min to 10 min. Depending on the metallization width, the strength of this material-bonded connection is up to 50 MPa.

In an alternative embodiment, a non-reactive metallic solder, in particular a tungsten paste, is applied as the metallic solder. The thermal treatment is performed at 1000°C to 1500°C, preferably for 30 min to 60 min. The high temperature is necessary because no chemical reaction takes place, but instead the tungsten atoms must diffuse into the ceramic substrate and the atoms of the substrate must diffuse into the microstructure of the tungsten solder. The thermal treatment may be preceded by a drying phase at 100°C for 10 min to 15 min.

In one embodiment, the surface of the EUV submodule coated with the metallic solder over its full surface area is subsequently coated at least in certain regions with nickel (Ni). A stable metallic bond is produced between the nickel and the metallized surface. This on the one hand also increases the resistance of the surface to hydrogen and hydrogen radicals. On the other hand, the nickel layer improves the wettability of the metallized surface with the solder. The nickel-coated regions also allow stable joining by means of adhesive bonding and soldering.

In one embodiment, the subsequent coating with nickel is performed by a galvanic process, by physical vapour deposition (PVD) or by chemical vapour deposition (CVD). Nickel is also particularly well suited for subsequent coating because it can be applied very well with a constant layer thickness. Alternatively or in addition, the completely metallized surface of the EUV submodule may also be subsequently coated in certain regions with copper or gold.

The object mentioned at the beginning is also achieved according to the invention by a method for producing an EUV module from EUV submodules. Firstly, at least two EUV submodules coated according to the invention are provided. Subsequently, the EUV submodules provided are joined. The joining of comparatively small and lightweight EUV submodules to form comparatively large and heavy EUV modules is advantageous for several reasons. A certain number of rejects is unavoidable in the production of the ceramic substrates for the EUV submodules. If an EUV module were produced directly as a monolithic component, it would be possible to dispense with the joining process between EUV submodules. However, if the large, monolithic EUV module had to be rejected because of a production defect, the costs would be much higher than if only a small defective EUV submodule had to be discarded. In one embodiment, the EUV submodules provided are joined by soldering, in particular with hard solder. Hard solders refer to alloys of a high silver content based on nickel silver or brass, which can usually be supplied in the form of bars, rods, wire, films and sometimes paste. Hard solder pastes already contain flux, so that it is no longer necessary for this to be added separately, likewise as a paste, as in the case of other forms of solder. By contrast with soft solder (tin/lead-based), hard solders are particularly well suited for metallic connections that undergo high mechanical and thermal loads. Alternatively or in addition, the EUV submodules provided are joined by adhesive bonding, in particular with ceramic adhesives. Ceramic adhesives are particularly advantageous, because they scarcely outgas in a vacuum. In the case of ceramic adhesives (also referred to as ceramic cements), in principle ceramic powders are mixed with inorganic binder systems such as water glass or phosphate compounds. Some adhesives are offered as paste, others are mixed shortly before use from the powder and a liquid component. There are two groups of ceramic adhesives. First, those that bond physically by evaporation of the solvent, generally water. These adhesives have mineral fillers such as A1₂0₃, Zr0₂ and MgO. Second, those that cure chemically, to be precise by a condensation reaction.

Alternatively, organic adhesives, for example with a methyl methacrylate (MM A) adhesive or epoxy resin adhesive, may be used for the joining.

The object mentioned at the beginning is also achieved according to the invention by a coated EUV submodule provided in an EUV lithography system. The EUV submodule has a ceramic body, which is covered with metallic solder over its full surface area. Between the ceramic body and the metallic solder there is a material bond. The material bond is absolutely necessary to make it possible for EUV submodules to be stably joined to one another later by means of adhesive bonding or soldering.

In one embodiment, the EUV submodule has a thickness of the metallization, that is to say of the metallic solder in the cured state, of between 5 μιη and 300 μιη, preferably between 10 μιη and 200 μιη. This thickness is sufficient for the joining by means of adhesive bonding or soldering. It must not go below the lower limit of 5 μιη, since then there is the risk of holes in the metallization. It is essential for these holes to be avoided, to ensure complete sealing of the EUV submodule. The thickness of the metallization that is necessary as a minimum depends here on the basic roughness of the ceramic substrate. The lower the basic roughness, the thinner the metallization can be chosen. Great thicknesses of the metallization should usually be considered to be positive for the quality of the sealing. With thicknesses of 300 μιη and more, however, there is the risk that during the conditioning, that is to say the thermal treatment, the organic constituents of the tungsten paste that make the tungsten paste spreadable no longer burn out completely. This reduces the quality of the material bond between the ceramic substrate and the metallization and entails risks of contamination for the EUV lithography system. In one embodiment, the ceramic material comprises aluminium oxide (AI₂O₃), silicon carbide (SiC) and/or silicon-infiltrated silicon carbide (Si:SiC). Si:SiC is particularly advantageous for use in an EUV submodule in a lithography system because it has advantageous vibrational behaviour, very good thermal conductivity, low thermal expansion and great geometrical stability under load. A further advantage is the low weight in comparison with metallic materials.

In one embodiment, a reactive metallic solder is applied to the EUV submodule as a metallic solder, in particular a silver-copper eutectic with additions selected from the group comprising titanium (Ti), manganese (Mn), zirconium (Zr) and hafnium (Hf).

In an alternative embodiment, a non-reactive metallic solder, in particular a tungsten paste, is applied to the EUV submodule as the metallic solder.

In one embodiment, the EUV submodule has at least one further metallic layer, in particular of nickel, nickel-phosphorus alloys, copper or gold, covering the metallization, that is to say the metallic solder in the cured state, at least in certain regions. The advantages of subsequent coating with nickel are mentioned above.

The object stated at the beginning is also achieved according to the invention by an EUV module which has at least two EUV submodules that are joined to one another as described above. The EUV submodules are joined to one another with a tensile strength of between 5 MPa and 50 MPa. Among the factors on which the respective level of the tensile strength depends is the kind of joining means. This strong bonding is a basic prerequisite for a stable EUV module. In one embodiment, at least one holding component is joined with the EUV submodule or with the EUV module. The holding component may be a sensor mounting.

In one embodiment, the holding component is joined by soldering, in particular with hard solder. Alternatively or in addition, the holding component may be joined by adhesive bonding, in particular with ceramic adhesives and/or organic adhesives.

Moreover, an EUV lithography system is claimed according to the invention. This has at least one EUV module acting as a measuring frame or as a measuring standard, designed for carrying at least one sensor. Moreover, the EUV lithography system has at least one force frame for carrying at least one optical component, in particular a mirror. The exact position of the optical component can be determined by means of the sensor. The force frame usually consists of steel. Instead of the term force frame, the term carrying frame is also used. The multiple EUV modules are separate and decoupled from one another. The EUV modules are also separate and decoupled from the force frame.

Brief description of the figures

Various exemplary embodiments are explained in more detail below on the basis of the figures. Elements that are the same, are of the same type or act in the same way are provided with the same reference signs in the figures. The figures and the relative sizes of the elements represented in the figures in relation to one another should not be regarded as true to scale. Rather, individual elements may be shown exaggerated in size or reduced in size for better representation and for better understanding.

Figure 1 shows a ground ceramic substrate before the coating.

Figure 2 shows the ground ceramic substrate with a coating according to the prior art.

Figure 3 shows a cutout from an EUV submodule coated according to the invention.

Figure 4 shows a cutout from an alternative EUV submodule coated according to the invention.

Figure 5 shows in a schematic form an EUV module according to the invention, joined from two EUV submodules coated according to the invention.

Figure 6 shows in a schematic form an EUV module according to the invention with a joined holding component and sensor.

Figure 7 shows in a schematic form a cutout essential for the invention from an EUV lithography system.

Figure 8 shows in a schematic form the EUV lithography system in its entirety. Best way of carrying out the invention

Figure 1 shows a known ceramic substrate 100 with non-critical pores 102 in the substrate 100 and with critical, partly ground away pores 104 on the substrate surface 101. Moreover, a superficial crack 106 and free silicon 108 can be seen on the substrate surface 101. Evident as particularly critical are weakly bonded regions 110 in the vicinity of the substrate surface 101, since they may become detached and, as freely mobile particles, may impair the function of the EUV lithography system. The material of the substrate 100 is silicon- infiltrated silicon carbide (Si:SiC). The substrate 100 shown in Figure 1 is both the starting product for the coating method according to the invention, the result of which is represented in Figures 3 and 4, and the starting product for the coating method according to the prior art, the result of which is represented in Figure 2. Figure 2 shows the result of the coating of the ceramic substrate 100 from Figure 1 according to a method from the prior art. The metallic coating of nickel-phosphorus alloys ( P) 112 has been applied to the surface 101 of the ground ceramic component 100. The coating is performed for example by galvanic deposition or chemical treatment (chemical nickel). The anchorage of the NiP layer 112 takes place purely mechanically, in that an interlocking engagement is formed by the surface roughnesses. Interlocking connections are produced by means of at least two connection partners engaging in one another. As a result, the connection partners cannot come apart even when there is no force transmission or the force transmission is interrupted.

However, the low layer bonding provided by interlocking engagement and the imperfect peripheral zone of the ceramic component limit the forces that can be transmitted via the NiP layer 112 into the ceramic component 100 and the tolerable temperature gradients, such as may occur with adhesive bonds or with soldering or brazing. Thus, the coefficient of expansion of NiP is very different from that of Si:SiC. This has the consequence that galvanically or chemically coated ceramic components cannot be joined by means of soldering and only to a limited extent by means of adhesive bonding to form larger subassemblies, and attachment parts, also known as holding components, for holding sensors, can only be attached insufficiently securely to the ceramic component coated with NiP. Figure 3 shows a cutout from an EUV submodule 120, 130 coated according to the invention for use in an EUV lithography system. Firstly, metallic solder 114 is applied to the substrate surface 101 over its full surface area by screen printing, spraying, immersion or spreading. Subsequently, a thermal treatment is performed to produce a material bond between the ceramic material 100 and the metallic solder 114. The material bond exists in a transitional zone 116 between the metallization, that is to say the metallic solder 114 in the cured state, and the ceramic substrate 100. The thermal treatment is performed in a vacuum in the temperature range from 700°C to 1500°C for 5 min to 60 min.

Two groups of materials may be used according to the invention as the metallic solder 114. On the one hand, a reactive metallic solder may be used, in particular a silver-copper eutectic with additions of titanium (Ti), manganese (Mn), zirconium (Zr) and/or hafnium (Hf). The thermal treatment is in this case performed at 700°C to 900°C for 5 min to 10 min. On the other hand, a non-reactive metallic solder, in particular a tungsten paste, may be used as the metallic solder 114. The thermal treatment is in this case performed at 1000°C to 1500°C for 30 min to 60 min.

The metallic solder 114 in the cured state seals the surface 101 of the ceramic substrate 100 and thereby bonds, inter alia, free silicon 108 and weakly bonded regions 1 10 of the substrate 100. After the improvement, the EUV submodule 120, 130 is suitable for a vacuum.

The thickness of the metallization, that is to say of the metallic solder 114 in the cured state, is between 5 μιη and 300 μιη. Even a thickness of 5 μιη is sufficient to impart the characteristics of a metal to the ceramic EUV submodule on its surface.

Figure 4 shows a cutout from an EUV submodule 120, 130 alternatively coated according to the invention. The surface 101 coated with the metallic solder 114 is subsequently coated at least in certain regions with nickel (Ni). The subsequent coating with nickel is performed by a galvanic process, by physical vapour deposition (PVD) or by chemical vapour deposition (CVD). The nickel coating 115 enters into a stable connection with the metallic solder 114 in the cured state and in just the same way as the metallic solder 114 in the cured state is suitable for a subsequent joining process.

Figure 5 shows in a schematic form an EUV module 200 according to the invention, joined from two EUV submodules 120, 130 coated according to the invention. For producing the EUV module 200, firstly two coated EUV submodules 120, 130 are provided. Subsequently, the two EUV submodules 120, 130 are joined. The joining may be performed by soldering, in particular with hard solder. Alternatively, the joining may be performed by adhesive bonding, in particular with ceramic adhesives. The joined region 140 between the first EUV submodule 120 and the second EUV submodule 130 connects the two EUV submodules 120, 130 with a tensile strength of between 5 MPa and 50 MPa. The respective value of the tensile strength is dependent on the choice of solder and the choice of adhesive. Soldered connections have a tensile strength of up to 50 MPa. Adhesively bonded connections with ceramic adhesives that are particularly well suited for operation in a highly pure vacuum have a tensile strength of between 5 MPa and 10 MPa.

Figure 6 shows in a schematic form an EUV module 200 according to the invention with a joined holding component 160. This holding component 160 is designed in the present exemplary embodiment as a sensor mounting. The holding component 160 may be joined by soldering, in particular with hard solder and/or by adhesive bonding, in particular with ceramic adhesives, to the metallic solder 114 in the cured state of the EUV module 200. Between the EUV module 200 and holding component 160 there is produced a joined region 150 with the aforementioned tensile strength. Arranged on the holding component 160 is a sensor 170. In an exemplary embodiment that is not shown, a plurality of holding components 160 with a plurality of sensors 170 are attached to the EUV module 200.

Figure 7 shows in a schematic form a cutout essential for the invention from an EUV lithography system 500. The EUV module 200 is separated from a force frame 300 by a mechanical decoupling 204. The EUV module 200 carries a sensor 170 by way of a holding component 160. The force frame 300 carries an optical component 302, in particular a mirror. Moreover, the actuators (not shown in the figure) for actuating the optical components 302 are fastened to the force frame 300. In an exemplary embodiment that is not shown, a plurality of sensors 170 are attached to the EUV module 200 by way of a plurality of holding components 160. Therefore, the EUV module 200 is also referred to as a sensor frame, measuring frame or measuring standard. The force frame 300 may also carry a plurality of optical components 302. The force frame 300 is separated from the solid surroundings 400 by way of a mechanical decoupling 304. Decisive in this case is the separation of the EUV module (measuring frame) 200 from the force frame 300. This separation makes it possible for the spatial position of the optical components 302 to be sensed without any problem by the sensors 170 of the sensor frame 200. In this case, the respective position of the mirror in relation to this sensor frame 200 may be measured by means of a position sensor 170 and set to the desired value by means of a controller (not shown in the figure) by way of an actuator (not shown in the figure). Details of this are disclosed in DE 102011077315 Al . In an exemplary embodiment that is not shown, the EUV lithography system 500 has a plurality of EUV modules 200. Each EUV module 200 may then be designed for sensing the position of various groups of optical components 302. The multiple EUV modules 200 of an EUV lithography system 500 are completely mechanically decoupled from one another. Figure 8 schematically shows an EUV lithography system 500 in its entirety, which comprises a beam- shaping and illumination system 504 and a projection system 506. The beam-shaping and illumination system 504 and the projection system 506 are respectively provided in a vacuum housing, each vacuum housing being evacuated with the aid of an evacuation device that is not represented any more specifically. The vacuum housings are surrounded by a machine room (not represented any more specifically), in which the drive devices for mechanically moving or adjusting the optical elements are provided. Electrical controllers and the like may also be provided in this machine room. The EUV lithography system 500 has an EUV light source 502. A plasma source or a synchrotron, which emit radiation 516 in the EUV range, may be provided for example as the EUV light source 502. In the beam-shaping and illumination system 504, the EUV radiation 516 is focused and the desired operating wavelength is filtered out from the EUV radiation 516. The EUV radiation 516 generated by the EUV light source 502 has a relatively low transmissivity through air, for which reason the beam-guiding spaces in the beam-shaping and illumination system 504 and in the projection system 506 are evacuated .

The beam-shaping and illumination system 504 represented in Figure 8 has five mirrors 610, 612, 614, 616, 618. After passing through the beam-shaping and illumination system 504, the EUV radiation 516 is directed onto the photomask (reticle) 510. The photomask 510 is likewise formed as a reflective optical element and may be arranged outside the systems 504, 506. Furthermore, the EUV radiation 516 may be directed onto the photomask 510 by means of a mirror 636. The photomask 510 has a structure, a reduced image of which is depicted on a wafer 514 or the like by means of the projection system 506.

The projection system 506 has six mirrors Ml - M6 for depicting the image of the photomask 510 on the wafer 514. In this case, individual mirrors Ml - M6 of the projection system 506 may be arranged symmetrically in relation to the optical axis 624 of the projection system 506. It should be noted that the number of mirrors of the EUV lithography system 500 is not restricted to the number represented. A greater or lesser number of mirrors may also be provided. Furthermore, the mirrors Ml - M6 are generally curved on their front side for beam shaping.

The projection system 500 also has a number of sensors 170, in particular position sensor devices, for determining a position of one of the mirrors Ml - M6.

On the assumption, by way of example, that the projection system 104 has six mirrors Ml - M6 (Nl = 6), of which five mirrors can be actuated (N2 = 5) and each of the actuable mirrors can be assigned six position sensor devices 170 (N4 = 6), a number N3 of the position sensor devices 170 in the projection system 506 of 30 is obtained (N3 = N4 · N2 = 6 · 5 = 30).

Without restricting the generality and for reasons of simplified representation, Figure 8 shows only one position sensor device 170.

The position sensor device 170 is coupled with an evaluation device that is not shown. The evaluation device is designed to determine the position of an actuable mirror of the mirrors Ml - M6 by means of the output signal of the position sensor device 170. The evaluation device - like the position sensor device 170 - may be arranged in the vacuum housing 520 of the projection system 506. In this case, the evaluation device is for example integrated in the signal processing unit. Alternatively, the evaluation device may also be arranged externally of the vacuum housing 520 of the projection system 506. At least one EUV module 200 (not shown in Figure 8) according to one of the aforementioned exemplary embodiments is arranged in the projection system 506.

List of reference signs

100 substrate

101 substrate surface

102 pore in the volume of the substrate

104 partly ground away pore on the substrate surface 101

106 superficial crack

108 free silicon

110 weakly bonded region on the substrate surface 101

112 nickel-phosphorus alloy

114 metallic solder

115 further metallic layer

116 material bond in the region of the transitional zone

120 first EUV submodule

130 second EUV submodule

140 joined region between first EUV submodule 120 and second EUV submodule 130

150 joined region between EUV module 200 and holding component 160

160 holding component

170 sensor, in particular position sensor device

200 EUV module, measuring frame, measuring standard, sensor frame

204 mechanical decoupling of EUV module 200 and force frame 300

300 force frame, carrying frame

302 optical component, for example mirror

304 mechanical decoupling of force frame 300 and fixed surroundings 400

400 fixed surroundings

500 EUV lithography system

502 EUV light source

504 beam-shaping and illumination system

506 projection system

510 photomask, reticle

514 wafer

516 EUV radiation

520 vacuum housing

610, 612, 614, 616, 618 mirrors in the beam-shaping and illumination system

504 624 optical axis of the projection system 506

636 mirror (in the case of grazing incidence)

Ml , M2, M3, M4, M5mirrors in the projection system 506

Claims

Patent claims:

1. Method for coating a surface (101) of an EUV submodule (120, 130) of ceramic material (100) that is intended for use in an EUV lithography system, comprising:

- applying a metallic solder (114) to the surface (101) over its full surface area;

- thermal treatment for producing a material bond (116) between the ceramic material (100) and the metallic solder (114).

2. Method according to Claim 1, the metallic solder (114) being applied by screen printing, spraying, immersion or spreading.

3. Method for producing an EUV module (200), comprising:

- providing at least two EUV submodules (120, 130) respectively coated by the method according to Claim 1 or 2;

- joining the EUV submodules (120, 130) provided.

4. Method according to Claim 3, the EUV submodules (120, 130) provided being joined by soldering, in particular with hard solder, and/or by adhesive bonding, in particular with ceramic adhesives.

5. EUV submodule (120, 130), intended for use in an EUV lithography system,

- with a ceramic body (100) and

- with a metallic solder (114) covering the ceramic body (100) over its full surface area, a material bond (116) existing between the ceramic body (100) and the metallic solder (114).

6. EUV submodule (120, 130) according to Claim 5, having a thickness of the metallic solder (114) of between 5 μιη and 300 μιη, preferably between 20 μιη and 200 μιη.

7. EUV submodule (120, 130) according to Claim 5 or 6, the material of the ceramic body (100) being selected from the group comprising aluminium oxide (A1₂0₃), silicon carbide

(SiC) and silicon- infiltrated silicon carbide (Si:SiC).

8. EUV submodule (120, 130) according to one of Claims 5 to 7, a reactive metallic solder being applied as the metallic solder (114), in particular a silver-copper eutectic with additions selected from the group comprising titanium (Ti), manganese (Mn), zirconium (Zr) and hafnium (Hf).

9. EUV submodule (120, 130) according to one of Claims 5 to 7, a non-reactive metallic solder, in particular a tungsten paste, being applied as the metallic solder (114).

10. EUV submodule (120, 130) according to one of Claims 5 to 9, having at least one further metallic layer (115) covering the metallic solder (1 14), at least in certain regions, the material of the further metallic layer (115) being selected from the group comprising nickel, nickel- phosphorus alloys ( P), copper and gold.

11. EUV module (200) having at least two EUV submodules (120, 130) according to one of Claims 5 to 10 joined to one another.

12. EUV module (200) according to Claim 11, the EUV submodules (120, 130) being joined by solder, in particular by hard solder and/or by adhesives, in particular by ceramic adhesives.

13. Method according to one of Claims 1 to 4, at least one holding component (160), in particular at least one sensor mounting, being joined with the EUV submodule (120, 130) or with the EUV module (200).

14. Method according to Claim 13, the holding component (160) being joined by soldering, in particular with hard solder and/or by adhesive bonding, in particular with ceramic adhesives.

15. EUV lithography system (500), having at least one EUV module (200) according to Claim 11 or 12 acting as a measuring frame or as a measuring standard, designed for carrying at least one sensor (170), and at least one force frame (300) for carrying at least one optical component (302) of which the position can be determined by means of the sensor (170).