Especially for mirrors in microlithography projection exposure systems

Abstract

The invention relates to a reflector, in particular a reflector for a microlithography projection exposure system, comprising a reflector substrate (12, 32, 52). The reflector has: a reflective layer stack (21, 41, 61) for reflecting electromagnetic radiation of an operating wavelength that impinges on an optically effective surface (11, 31, 51); and at least one piezoelectric layer (16, 36, 56) arranged between the reflector substrate and the reflective layer stack, and to which an electric field that generates a local deformable deformation can be applied by a first electrode arrangement and a second electrode arrangement, the first electrode arrangement (20, 40, 60) being located on the side of the piezoelectric layer facing the reflective layer stack, and the second electrode arrangement (14, 34, 54) being located on the side of the piezoelectric layer facing the reflector substrate. According to one aspect, a support layer (98) is provided, which reduces the sinking of the piezoelectric layer (96) into the reflector substrate (92) with the application of the electric field and thus increases the effective deflection of the piezoelectric layer (96) compared to a similar design without a support layer.

Description

[0001] This application claims the priority of German patent application DE 10 2017 213 900.5 filed on August 9, 2017. The content of this German application is also incorporated into the text of the present application by reference. Background of the Invention

[0002] Field of the Invention

[0003] The invention relates to a reflector, in particular a reflector for a microlithography projection exposure device, and a method for manufacturing the same.

[0004] Prior art

[0005] Microlithography is used to produce microstructured components, such as integrated circuits or LCDs. The microlithography process is carried out in a so-called projection exposure system, which comprises an illumination device and a projection lens. Here, the image of a mask (=reticle) illuminated by the illumination device is projected by the projection lens onto a substrate (e.g. a silicon wafer) which is coated with a photosensitive layer (photoresist) and is arranged in the image plane of the projection lens, in order to transfer the mask structure to the photosensitive coating of the substrate.

[0006] In projection lenses designed for the EUV range (ie at wavelengths of eg about 13 nm or about 7 nm), mirrors are used as optical components of the imaging process due to the lack of available appropriately light-transmitting refractive materials.

[0007] In this context, it is known that one or more mirrors in an EUV system are configured as an adaptive mirror with an actuator layer consisting of a piezoelectric material, wherein an electric field with locally varying strength is generated above the piezoelectric layer by applying a voltage to electrodes arranged on both sides with respect to the piezoelectric layer. In the event of a local deformation of the piezoelectric layer, the stack of reflective layers of the adaptive mirror also deforms, so that for example (possibly also time-variable) imaging aberrations are at least partially compensated by appropriately driving the electrodes.

[0008] Figure 8The conventional structure of a reflector 100 comprising a reflector substrate 112 and a reflective layer stack 121 is shown schematically. The reflector 100 is of adaptive design and comprises a piezoelectric layer 116 (e.g., composed of lead zirconate titanate (Pb(Zr, Ti)O3, PZT)) for this purpose. Electrode arrangements 114, 120 are located above and below the piezoelectric layer 116, respectively, through which an electric field that produces a locally variable deformation can be applied to the reflector 100. The second electrode arrangement 114 facing the substrate 112 is configured as a continuous planar electrode with a constant thickness, while the first electrode arrangement 120 comprises a plurality of electrodes 120a, 120b, 120c, ..., to which a voltage relative to the first electrode arrangement 114 can be applied via supply lines 119a, 119b, 119c, ..., respectively.

[0009] The electrodes 120a, 120b, 120c, ... are embedded in a smoothing layer 118 made of quartz (SiO2), which serves to level the electrode arrangement 120. In addition, the reflector 100 comprises an adhesive layer 113 (e.g., made of titanium Ti), and a buffer layer 115 between the reflector substrate 112 and the bottom electrode 114 facing the reflector substrate 112.

[0010] During operation of an optical system including the mirror 100, a voltage is applied to the electrode arrangements 114 and 120 via an electric field formed in the region of the piezoelectric layer 116, resulting in a deflection of the piezoelectric layer 116. In this way, compensation of optical aberrations (e.g. caused by thermal deformations in the case of EUV radiation incident on the optically active surface 111) enables actuation of the mirror 100. The intermediate layer 117 is connected to the electrodes 120a, 120b, 120c, ... (which are shown in FIG. 1 for illustration purposes only). Figure 1 ) in direct electrical contact in a plan view, and the intermediary layer 117 is used to "communicate" the potential between the electrodes 120a, 120b, 120c... of the electrode arrangement 120 within the piezoelectric layer 116, wherein the intermediary layer has only a low electrical conductivity (for example, less than 200 Siemens / meter (S / m)), so that the potential difference existing between adjacent electrodes 120a, 120b, 120c... is substantially reduced across the intermediary layer 117, and therefore reduced in the piezoelectric material between the electrodes.

[0011] During the manufacture of the adaptive mirror 100, it is a demanding challenge to ensure that the reflective layer stack 121 is applied while meeting the required specifications. In practice, one problem that arises here is, in particular, that during the manufacturing process before the application of the reflective layer system, an interferometric measurement of the corresponding surface-treated layer is achieved without the measurement being influenced by the metallic structure of the electrode arrangement 120 and the piezoelectric layer 116, since such influences could lead to a deterioration of the interferometric measurement results and therefore the availability of material removal carried out in each case during manufacturing is insufficient.

[0012] With regard to the prior art, reference is made purely by way of example to DE 10 2015 213 273 A1. Summary of the invention

[0013] It is an object of the present invention to provide mirrors, in particular mirrors for microlithographic projection exposure apparatuses, and methods for their production which enable the highest possible surface quality while complying with the specifications required, for example, in the EUV range.

[0014] This object is achieved according to the features of the independent patent claim.

[0015] According to one aspect of the present invention, the reflector according to the present invention comprises:

[0016] -Optically effective surface;

[0017] - mirror substrate;

[0018] - a stack of reflective layers for reflecting electromagnetic radiation of an operating wavelength incident on the optically effective surface; and

[0019] at least one piezoelectric layer, which is arranged between the reflector substrate and the reflector layer stack and to which an electric field producing a local deformable deformation can be applied by means of a first electrode arrangement and a second electrode arrangement, the first electrode arrangement being located on a side of the piezoelectric layer facing the reflector layer stack and the second electrode arrangement being located on a side of the piezoelectric layer facing the reflector substrate;

[0020] - wherein a multifunctional layer system is provided which enables a smooth surface treatment when the first electrode arrangement is embedded and secondly has a transmittance of less than 10 for electromagnetic radiation having a test wavelength -6 , in order to be able to perform surface interferometry.

[0021] Here and in the following, the term "transmittance" is to be understood as the transmittance in two passes (after reflection of the relevant electromagnetic radiation) through the layer being treated in order to achieve the desired surface quality.

[0022] The invention is based in particular on the idea that in an adaptive mirror comprising a piezoelectric layer to which a voltage can be applied via an electrode arrangement, a high surface quality can be achieved while meeting the specifications required in the EUV range, by virtue of the fact that the mirror is equipped with a multifunctional layer system which, in addition to the conventional embedding of electrodes, enables surface interferometry. This effect is achieved by providing a sufficiently low transmittance for electromagnetic radiation having the corresponding test wavelength.

[0023] In other words, the multifunctional layer system according to the invention not only meets the requirements regarding smoothness and electrical insulation of the electrodes with respect to one another, but also simultaneously prevents during the manufacturing process the measurement results obtained by the metal structures of the electrode arrangement and by the piezoelectric layer during interferometric measurements of the corresponding surface-treated layers, as described in the background, from being influenced or deteriorated.

[0024] In particular, the present invention does not involve solely the use of a smoothing layer in the form of amorphous quartz (SiO2) to embed the electrodes, but rather, according to the embodiments described below, either appropriately manipulating the smoothing layer by corresponding doping or adding at least one further layer in order to ensure that the above-mentioned metallic structure of the electrode arrangement and the piezoelectric layer is "invisible" during interferometric measurements.

[0025] In the context of this application, the term "multifunctional layer system" is intended to cover: configurations comprising only a single layer that performs all the functions described above (i.e. smoothing, electrical insulation and ensuring interferometry); as well as configurations in which the functions are performed by two or more layers.

[0026] According to one embodiment, the transmittance of the multifunctional layer system for electromagnetic radiation having a test wavelength is less than 10 -7 , especially less than 10 -8 , more particularly less than 10 -9 .

[0027] According to one embodiment, the multifunctional layer system comprises a layer of doped quartz glass (SiO 2 ).

[0028] According to one embodiment, the multifunctional layer system comprises a layer composed of amorphous silicon (a-Si).

[0029] According to one embodiment, the mirror comprises a support layer which reduces the sinking of the piezoelectric layer into the mirror substrate accompanying the application of an electric field and thereby increases the effective deflection of the piezoelectric layer compared to a similar structure without the support layer.

[0030] According to one embodiment, the support layer comprises quartz glass (SiO 2 ).

[0031] The above effects achieved by the support layer are advantageous regardless of the presence of the multifunctional layer system as described above. Therefore, according to further aspects, the invention also relates to a reflector, wherein the reflector comprises an optically active surface, the reflector comprising:

[0032] - mirror substrate;

[0033] - a stack of reflecting layers for reflecting electromagnetic radiation of an operating wavelength incident on the optically effective surface;

[0034] at least one piezoelectric layer arranged between the reflector substrate and the reflective layer stack and capable of applying an electric field producing a local deformable deformation to the at least one piezoelectric layer by means of a first electrode arrangement located on a side of the piezoelectric layer facing the reflective layer stack and a second electrode arrangement located on a side of the piezoelectric layer facing the reflector substrate; and

[0035] - A support layer, which reduces the sinking of the piezoelectric layer into the mirror substrate accompanying the application of an electric field and thus increases the effective deflection of the piezoelectric layer compared to a similar construction without a support layer.

[0036] According to one embodiment, the thickness of the support layer is at least 10 μm, more particularly at least 15 μm, and more particularly at least 30 μm.

[0037] According to one embodiment, the mirror is designed for an operating wavelength of less than 30 nm, in particular less than 15 nm.

[0038] According to one embodiment, the mirror is a mirror of a microlithography projection exposure apparatus.

[0039] According to another aspect, the present invention also relates to a method for manufacturing a reflector, wherein the method comprises the following steps:

[0040] -Providing a reflector substrate;

[0041] - applying a piezoelectric layer and a first electrode arrangement and a second electrode arrangement to the reflector substrate, wherein an electric field generating a local deformable deformation can be applied to the piezoelectric layer via the first electrode arrangement and the second electrode arrangement, the first electrode arrangement being located on a side of the piezoelectric layer facing away from the reflector substrate, and the second electrode arrangement being located on a side of the piezoelectric layer facing the reflector substrate;

[0042] wherein the first electrode arrangement is embedded in a multifunctional layer system which firstly allows a smooth surface treatment and has a transmittance of less than 10 for electromagnetic radiation having a test wavelength. -6 , to enable surface interferometry; and

[0043] - Applying a reflective layer stack to reflect electromagnetic radiation of the operating wavelength incident on the optically active surface.

[0044] According to one embodiment, the multifunctional layer system comprises a layer composed of quartz glass (SiO 2 ).

[0045] According to one embodiment, the multifunctional layer system comprises an absorber layer, in particular composed of carbon (C).

[0046] According to one embodiment, the absorption layer is removed in each case before applying the reflective layer stack, in particular after correspondingly carrying out the surface interferometry measurement.

[0047] According to one embodiment, the multifunctional layer system comprises a layer of doped quartz glass (SiO 2 ).

[0048] According to one embodiment, the multifunctional layer system comprises a layer composed of amorphous silicon (a-Si).

[0049] The reflector can in particular be a reflector of a microlithography projection exposure apparatus. However, the invention is not limited thereto. In other applications, the reflector according to the invention can also be employed or utilized, for example, in an apparatus for mask metrology.

[0050] According to one embodiment, the mirror is designed for an operating wavelength of less than 30 nm, in particular less than 15 nm. However, the invention is not limited thereto, and thus the invention can also be advantageously implemented in other applications of optical systems with an operating wavelength in the VUV range (e.g. less than 200 nm).

[0051] The invention further relates to an optical system, in particular an illumination device or a projection lens of a microlithography projection exposure apparatus, said optical system comprising at least one mirror having the above-mentioned features, and to a microlithography projection exposure apparatus.

[0052] Further configurations of the invention can be gathered from the description and the dependent claims.

[0053] The invention is explained in more detail below on the basis of exemplary embodiments illustrated in the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In the attached figure:

[0055] Figure 1 shows a schematic diagram illustrating the structure of an adaptive mirror according to one embodiment of the present invention;

[0056] Figure 2-3 shows a schematic diagram illustrating the structure of an adaptive reflector in other embodiments of the present invention;

[0057] Figure 4shows a schematic diagram illustrating one possible method of manufacturing a reflector according to the invention;

[0058] Figure 5-7 Schematic diagrams illustrating other embodiments of the present invention are shown;

[0059] Figure 8 shows a schematic diagram illustrating a possible structure of a conventional adaptive mirror; and

[0060] Fig. 9 A schematic diagram of the structure of a microlithography projection exposure apparatus designed to operate in EUV is shown. DETAILED DESCRIPTION

[0061] Figure 1 A schematic diagram illustrating the structure of a reflector according to the invention in one embodiment of the invention is shown. The reflector 10 comprises in particular a reflector substrate 12, which is made of any desired suitable reflector substrate material. Suitable reflector substrate materials are, for example, quartz glass doped with titanium dioxide (TiO2), merely as an example (and the invention is not limited thereto), wherein available materials are known under the trade name (from Corning Incorporated) or Materials sold by SCHOTT.

[0062] Furthermore, the reflector 10 has in principle in a manner known per se a reflective layer stack 21 which in the illustrated embodiment comprises, by way of example only, a molybdenum-silicon (Mo-Si) layer stack. Without limiting the invention to a specific configuration of the layer stack, a suitable structure, by way of example only, may comprise a layer system of about 50 lamellae or 50 layer packages, comprising molybdenum (Mo) layers each having a layer thickness of 2.4 nm and silicon (Si) layers each having a layer thickness of 3.3 nm.

[0063] The mirror 10 may in particular be an EUV mirror of an optical system, in particular a projection lens or an EUV mirror of an illumination device in a microlithography projection exposure apparatus.

[0064] During operation of the optical system, electromagnetic EUV radiation ( Figure 1Irradiation of the optically active surface 11 of the reflector 10 (indicated by arrows in the figure) may lead to an inhomogeneous volume change of the reflector substrate 12 and a shape change of the optically active surface 11 due to a temperature distribution, which is caused by the absorption of radiation that is inhomogeneously irradiated on the optically active surface 11. In order to correct such undesired shape changes of the optically active surface 11, or in order to correct other aberrations that occur during operation of the microlithography projection exposure apparatus, the reflector 10 has an adaptive design, as explained in more detail below. To this end, the reflector 10 according to the invention comprises a piezoelectric layer 16, which in an exemplary embodiment is made of lead zirconate titanate (Pb(Zr,Ti)O3, PZT) and whose exemplary thickness may be, for example, in the range of 1 μm to 2 μm. In other embodiments, the piezoelectric layer 16 may also be made of some other suitable material, such as aluminum nitride (AlN), aluminum scandium nitride (AlScN) or lead magnesium niobate (PbMgNb). The thickness of the piezoelectric layer 16 may be, for example, less than 5 μm, more particularly in the range of 1 μm to 2 μm.

[0065] according to Figure 1 , electrode arrangements 14, 20 (made of platinum in the exemplary embodiment) are respectively located above and below the piezoelectric layer 16, through which an electric field that generates local deformable deformation can be applied to the reflector 10. With regard to the electrode arrangements 14, 20, the second electrode arrangement 14 facing the substrate 12 is configured as a continuous planar electrode of constant thickness, while the first electrode arrangement 20 includes a plurality of electrodes 20a, 20b, 20c, ..., to which a voltage relative to the first electrode arrangement 14 can be applied via supply lines 19a, 19b, 19c, ..., respectively.

[0066] In other embodiments, Figure 1 Conversely, the second electrode arrangement 14 may also consist of a plurality of electrodes instead of the first electrode arrangement 20 , and the first electrode arrangement may instead be configured as a continuous planar electrode.

[0067] Furthermore, without limiting the invention to this, the electrodes 20a, 20b, 20c, ... have a hexagonal geometry, wherein, in particular, they can also be arranged substantially over a wider area and only in a manner isolated from one another by relatively narrow grooves. The invention as a whole is not limited to a specific geometry of the electrodes or the distances between the electrodes (wherein the distances between the electrodes can also be, for example, a few millimeters (mm) or a few centimeters (cm)).

[0068] according to Figure 1, the supply lines 19a, 19b, 19c, ... each have a first section extending perpendicularly to the stacking direction of the reflective layer stack 21 and a second section (also referred to as a "through hole" or "plated through hole") extending in the stacking direction of the reflective layer stack 21. Other types of contact are also possible, where for example in other embodiments, the supply line can also be implemented with only one section extending perpendicularly to the stacking direction (two-dimensional design and without a "through hole").

[0069] In addition, according to Figure 1 The reflector 10 includes an adhesive layer 13 (e.g., made of titanium Ti) between a reflector substrate 12 and a bottom electrode 14 facing the reflector substrate 12. In addition, "15" indicates a growth layer present between the electrode arrangement 14 facing the substrate 12 and the piezoelectric layer 16. The growth layer 15 is used to provide optimal crystal growth conditions and control the piezoelectric layer as much as possible, and can be made of LaNiO3, for example.

[0070] During operation of the mirror 10 or an optical system comprising the mirror 10, a voltage is applied to the electrode arrangements 14 and 20 via the electric field formed in the region of the piezoelectric layer 16, resulting in a deflection of the piezoelectric layer 16. In this way, an actuation of the mirror 10 can be achieved, for example by compensating for optical aberrations caused by thermal deformations in the event of EUV radiation incident on the optically active surface 11.

[0071] exist Figure 1 In an exemplary embodiment of the present invention, the reflector 10 further comprises an interposer layer 17. The interposer layer 17 is in direct electrical contact with the electrodes 20a, 20b, 20c, ... (which is shown in FIG. 1 for illustration purposes only). Figure 1 ). The intermediary layer 17 itself does not constitute the claimed subject matter of the present invention and serves to "communicate" the potential between the electrodes 20a, 20b, 20c, ... of the electrode arrangement 20 within the piezoelectric layer, wherein the intermediary layer has only a low conductivity (preferably less than 200 Siemens / meter (S / m)), so that the potential difference existing between adjacent electrodes 20a, 20b, 20c, ... is substantially reduced across the intermediary layer 17. Although, as described above, the use of an intermediary layer 17 in the adaptive mirror according to the present invention is advantageous, the present invention is not limited to the presence of such an intermediary layer.

[0072] Electrodes 20a, 20b, 20c, ... are embedded in the multifunctional layer system 18. Figure 1In the exemplary embodiment of the present invention, the multifunctional layer system 18 is formed by a doped quartz (SiO2) layer and is used to level the electrode arrangement 20. The multifunctional layer system 18 is not only provided for smoothing and leveling the structure pressed by the structured electrode 20 and the supply line 19 on the entire layer stack, but is also provided for electrically insulating the supply lines 19a, 19b, 19c, ... from one another and, during the manufacturing process of the mirror 10, for making it possible to carry out interferometric measurements without the measurement results being influenced by the metal structure of the electrode arrangement 20 and the piezoelectric layer 16. For this purpose, according to Figure 1 The doping of the formed quartz (SiO2) layer may include, for example, the incorporation of carbon (C) atoms, as a result of which the transmittance of radiation having a corresponding test wavelength (which may be in the range of 400nm-600nm as an example) is sufficiently reduced so that for interferometric measurements the underlying structures mentioned above (electrode arrangement 20 and piezoelectric layer 16) are no longer visible.

[0073] With regard to the above-mentioned smooth or achievable surface roughness, exemplary suitable values ​​of surface roughness achievable in each case by methods such as robotic polishing or ion beam patterning are preferably less than 0.2 nm RMS, more preferably less than 0.15 nm RMS in the spatial frequency range of 1 μm to 1 mm.

[0074] As far as electrical insulation of the supply line is concerned, the relevant layer or multifunctional layer system 18 preferably has a surface conductivity of less than 1 / (kΩ·m), in particular less than 1 / (MΩ·m).

[0075] Finally, as far as interferometry is concerned, the transmittance of the relevant layer or multifunctional layer system 18 is preferably less than 10 -9 .

[0076] In an embodiment, the multifunctional layer system 18 may further comprise a reflective layer having a reflectivity of preferably at least 10%, more preferably at least 30%, and more preferably at least 50% for radiation having a corresponding operating wavelength.

[0077] In the finished mirror, the thickness of the doped quartz (SiO2) layer forming the multifunctional layer system 18 can be, for example, in the range of (500-700) nm. If, for example, it is further assumed that material removal in the range of (600-800) nm is to be achieved during production, this presupposes that the initial thickness of the part of the multifunctional layer system 18 to be smoothed is at least 1300 nm.

[0078] Figure 2 Other embodiments of the present invention are shown, in which Figure 1Components that are similar or have substantially the same functions as those in the exemplary embodiments of the present invention are denoted by reference numerals with “20” added thereto.

[0079] and Figure 1 In comparison, according to Figure 2 , the multifunctional layer system 38 is configured as an amorphous silicon layer, so that the reduction in transmittance required for interferometric measurements is also achieved. In order to ensure sufficient electrical insulation, the amorphous silicon layer can have an appropriate doping.

[0080] Figure 3 Other embodiments of the present invention are shown, in which Figure 2 Components that are similar or have substantially the same functions as those in the exemplary embodiments are sequentially denoted by reference numerals with “20” added thereto.

[0081] and Figure 1 and Figure 2 In comparison, according to Figure 3 , the multifunctional layer system 58 comprises a layer stack consisting of a quartz (SiO2) layer 58a and an amorphous silicon layer 58b, wherein the transmittance reduction required for interferometric measurement is achieved by the amorphous silicon layer 58b. The quartz (SiO2) layer 58a serves to smooth and level the electrode arrangement 60, and to ensure sufficient electrical insulation of the supply lines 59a, 59b, 59c, ... from one another (so the amorphous silicon layer 58b no longer needs to have an insulating effect). The smoothing level made by the quartz (SiO2) layer 58a is not impaired by the amorphous silicon layer 58b, so that overall a multifunctional layer system 58 having the three effects described above (smoothing, electrical insulation and transmittance reduction, or ensuring interferometric measurement) is achieved.

[0082] Figure 4 A schematic diagram illustrating a possible method for manufacturing a reflector according to a further embodiment of the invention is shown. This embodiment differs from the embodiment described above in that during the manufacturing process, a sacrificial layer 78b consisting, for example, of carbon (C) is applied to the quartz (SiO2) layer 78a for the purpose of the interferometric measurement and for the duration of the interferometric measurement, and after the measurement, the sacrificial layer is removed again in each case, so that a new step of surface treatment can be implemented in each case. In this case, the thickness of the sacrificial layer 78b consisting of carbon (C) can be, for example, 35 μm. Although the sacrificial layer 78b consisting of carbon (C) applied in each case for the purpose of the interferometric measurement and for the duration of the interferometric measurement no longer needs to be present in the finished manufactured reflector, the invention is also intended to cover embodiments in which the sacrificial layer 78b consisting of carbon (C) is ultimately retained in the layer structure of the reflector.

[0083] Figure 5 Other possible embodiments of the present invention are shown in schematic diagrams. Similar to the embodiments described above, Figure 5 The layer structure schematically shown in firstly comprises a mirror substrate 92 , a buffer layer 93 , a piezoelectric layer 96 located between the electrode arrangements 94 , 99 and a reflective layer stack 101 .

[0084] Then, Figure 5 The embodiments in the present invention take into account that in practice d 33 The problem of an undesirable reduction of the coefficient occurs, which describes the component of the dielectric tensor responsible for the linear expansion depending on the voltage applied to the piezoelectric layer 96 in the direction perpendicular to the optically active surface. The problem is caused by the sinking of the piezoelectric layer into the mirror substrate, which occurs when a voltage is applied to the electrodes and is accompanied by lateral contraction. This effect is mainly manifested in the case of soft, non-rigid mirror substrate materials (with a low elastic modulus) and ultimately has the undesirable consequence that the expansion of the piezoelectric layer that can be effectively used for deformations of the optically active surface of the mirror in the direction perpendicular to the optically active surface is significantly reduced.

[0085] Figure 6 a-6b shows the corresponding simulation results for different substrate materials, wherein curves "C" and "E" represent the simulation results for a quartz substrate ( Figure 6 a) and for the bottom surface of the silicon substrate ( Figure 6 b), and wherein the curves “D” and “F” represent in each case the deformation of the piezoelectric layer occurring for the top side (i.e. the side facing away from the substrate).

[0086] To counteract this effect, Figure 5 In the schematically illustrated structure, the reflector according to the invention comprises a support layer 98, which is arranged on the side of the piezoelectric layer 96 or the electrode arrangement 99 facing the reflective layer stack 101. The support layer 98 can be made of a material such as quartz glass (SiO2), for example, the value of the elastic modulus (Young's modulus) of which is comparable to the value of the elastic modulus of the material of the reflector substrate 92. In this way, a compensation effect can be achieved (which can be understood graphically with the help of the structure of the mirror image as described above), thereby increasing the effective deflection of the piezoelectric layer 96. In order to obtain a significant compensation effect, the thickness of the support layer 98 can be of the order of 30 μm, for example.

[0087] Figure 7 A diagram illustrating the effect of a support layer having a thickness of 30 μm on the effective deflection of the piezoelectric layer compared to a mirror without a support layer is shown.

[0088] The compensation effect described above due to the support layer 98 can also be achieved in combination with the above-described effects of the multifunctional layer system according to the invention.

[0089] Fig. 9 A schematic diagram of an exemplary projection exposure apparatus is shown which is designed to operate in EUV and in which the present invention can be implemented. Fig. 9 , the illumination device in the projection exposure apparatus 900 designed for EUV comprises a field facet mirror 903 and a pupil facet mirror 904. Light from a light source unit comprising a plasma light source 901 and a collector mirror 902 is directed onto the field facet mirror 903. A first telescope mirror 905 and a second telescope mirror 906 are arranged in the light path downstream of the pupil facet mirror 904. A deflection mirror 907 is arranged downstream of the light path, the deflection mirror directing the radiation incident thereon onto the object field in the object plane of the projection lens, the projection lens comprising six mirrors 951-956. At the location of the object field, a mask 921 carried by a reflective structure is arranged on a mask stage 920, the mask being imaged into an image plane by means of the projection lens, in which a substrate 961 coated with a photosensitive layer (photoresist) is located on a wafer stage 960.

[0090] With regard to the mirrors 951 - 956 of the projection lens, in particular mirrors 951 and 952 - which are arranged in the initial region of the projection lens with regard to the beam path - they can be configured in a manner according to the invention, since the effect achieved by compensating for thermal deformations is particularly noticeable due to the still relatively low total reflection losses and therefore relatively high light intensity at the mirrors 951 , 952.

[0091] Although the present invention has been described with reference to specific embodiments, many variations and alternative embodiments will be apparent to those skilled in the art, for example by combining and / or exchanging the features of the various embodiments. Therefore, it is apparent to those skilled in the art that the present invention also encompasses such variations and alternative embodiments, and the scope of the present invention is limited only within the meaning of the appended claims and their equivalents.

Claims

1. A reflector, wherein: The reflector has an optically effective surface (11, 31) comprising: A reflector substrate (92); A reflective layer stack (101) for reflecting electromagnetic radiation having an operating wavelength incident on the optically effective surface; at least one piezoelectric layer (96), the at least one piezoelectric layer being arranged between the reflector substrate (92) and the reflective layer stack (101), and being capable of applying an electric field producing a local deformable deformation to the at least one piezoelectric layer through a first electrode arrangement (99) and a second electrode arrangement (94), the first electrode arrangement (99) being located on a side of the piezoelectric layer (96) facing the reflective layer stack (101), and the second electrode arrangement (94) being located on a side of the piezoelectric layer (96) facing the reflector substrate (92); and a support layer (98) that reduces the sinking of the piezoelectric layer (96) into the mirror substrate (92) with the application of an electric field and thereby increases the effective deflection of the piezoelectric layer (96) compared to a similar structure without the support layer; Wherein, the thickness of the support layer (98) is at least 15 μm.

2. The reflector according to claim 1, characterized in that The support layer (98) includes quartz glass (SiO2).

3. The reflector according to claim 1 or 2, characterized in that: The support layer (98) has a thickness of at least 30 μm.

4. The reflector according to any one of claims 1 to 3, characterized in that A multifunctional layer system (18, 38, 58) is provided which enables a smooth surface treatment when the first electrode arrangement is embedded and which additionally has a transmittance of less than 10 for electromagnetic radiation having a test wavelength. -6 , in order to be able to perform surface interferometry.

5. A reflector, wherein the reflector has an optically effective surface (11, 31, 51), comprising: A reflector substrate (12, 32, 52); A reflective layer stack (21, 41, 61) for reflecting electromagnetic radiation having an operating wavelength incident on the optically effective surface (11, 31, 51); as well as At least one piezoelectric layer (16, 36, 56), the at least one piezoelectric layer being arranged between the reflector substrate (12, 32, 52) and the reflective layer stack (21, 41, 61), and being capable of applying an electric field producing a local deformable deformation to the at least one piezoelectric layer through a first electrode arrangement (20, 40, 60) and a second electrode arrangement (14, 34, 54), the first electrode arrangement (20, 40, 60) being located on a side of the piezoelectric layer (16, 36, 56) facing the reflective layer stack (21, 41, 61), and the second electrode arrangement (14, 34, 54) being located on a side of the piezoelectric layer (16, 36, 56) facing the reflector substrate (12, 32, 52); Therein, a multifunctional layer system (18, 38, 58) is provided, which allows for a smooth surface treatment when the first electrode arrangement is embedded, and additionally has a transmittance of less than 10 for electromagnetic radiation having a test wavelength. -6 , to enable surface interferometry; and Therein, the multifunctional layer system (18) comprises a layer composed of doped quartz glass (SiO2).

6. The reflector according to claim 4 or 5, characterized in that: For electromagnetic radiation having the test wavelength, the multifunctional layer system (18, 38, 58) has a transmittance of less than 10 -7 .

7. The reflector according to claim 6, characterized in that The transmittance is less than 10 -8 .

8. The reflector according to claim 6, characterized in that The transmittance is less than 10 -9 .

9. The reflector according to any one of claims 4 to 8, characterized in that The multifunctional layer system (38, 58) comprises a layer composed of amorphous silicon (a-Si).

10. A reflector according to any one of the preceding claims, characterized in that The mirrors are designed for operating wavelengths less than 30 nm.

11. The reflector according to claim 10, characterized in that The operating wavelength is less than 15 nm.

12. A reflector according to any one of the preceding claims, characterized in that The mirror is a mirror of a microlithography projection exposure apparatus.

13. A method for manufacturing a reflector, wherein: The method comprises the following steps: Providing a reflector substrate (12, 32, 52, 72); A piezoelectric layer (16, 36, 56, 76) and a first electrode arrangement and a second electrode arrangement are applied to the reflector substrate (12, 32, 52, 72), wherein an electric field that generates a local deformable deformation can be applied to the piezoelectric layer (16, 36, 56) through the first electrode arrangement (20, 40, 60, 80) and the second electrode arrangement (14, 34, 54, 74), the first electrode arrangement is located on a side of the piezoelectric layer (16, 36, 56, 76 that faces away from the reflector substrate (12, 32, 52, 72), and the second electrode arrangement is located on a side of the piezoelectric layer (16, 36, 56, 76) that faces the reflector substrate (12, 32, 52, 72); The first electrode arrangement is embedded in a multifunctional layer system which firstly allows a smooth surface treatment and secondly has a transmittance of less than 10 -6 , to enable surface interferometry; and applying a stack of reflective layers (21, 41, 61) to reflect electromagnetic radiation of an operating wavelength incident on an optically active surface (11, 31, 51) of the reflector; In this case, the multifunctional layer system comprises a layer composed of doped quartz glass (SiO 2 ).

14. A method of manufacturing a reflector, wherein: The method comprises the following steps: Providing a reflector substrate (12, 32, 52, 72); A piezoelectric layer (16, 36, 56, 76) and a first electrode arrangement and a second electrode arrangement are applied to the reflector substrate (12, 32, 52, 72), wherein an electric field that generates a local deformable deformation can be applied to the piezoelectric layer (16, 36, 56) through the first electrode arrangement (20, 40, 60, 80) and the second electrode arrangement (14, 34, 54, 74), the first electrode arrangement is located on a side of the piezoelectric layer (16, 36, 56, 76 that faces away from the reflector substrate (12, 32, 52, 72), and the second electrode arrangement is located on a side of the piezoelectric layer (16, 36, 56, 76) that faces the reflector substrate (12, 32, 52, 72); The first electrode arrangement is embedded in a multifunctional layer system which firstly allows a smooth surface treatment and secondly has a transmittance of less than 10 -6 , so as to be able to perform surface interferometry; applying a stack of reflective layers (21, 41, 61) to reflect electromagnetic radiation of an operating wavelength incident on an optically active surface (11, 31, 51) of the reflector; wherein the absorbent layer system comprises an absorbent layer (98); and Therein, the absorber layer (98) is removed in each case before applying the reflective layer stack (21, 41, 61).

15. The method according to claim 13 or 14, characterized in that For electromagnetic radiation having the test wavelength, the multifunctional layer system (18, 38, 58) has a transmittance of less than 10 -7 .

16. The method according to claim 15, characterized in that The transmittance is less than 10 -8 .

17. The method according to claim 15, characterized in that The transmittance is less than 10 -9 .

18. The method according to claim 14 or 15, characterized in that The multifunctional layer system comprises a layer composed of quartz glass (SiO 2 ).

19. The method according to claim 13, characterized in that The multifunctional layer system includes an absorbent layer (98).

20. The method according to claim 19, characterized in that The absorption layer (98) is composed of carbon (C).

21. The method according to claim 19 or 20, characterized in that After the surface interferometry has been carried out in each case accordingly, the absorption layer (98) is removed.

22. The method according to any one of claims 13 to 21, characterized in that The multifunctional layer system comprises a layer composed of amorphous silicon (a-Si).

23. An optical system, characterized in that: The optical system comprises a mirror as claimed in any one of the preceding claims.

24. The optical system according to claim 23, characterized in that The optical system is an illumination device or a projection lens of a microlithography projection exposure apparatus.

25. A microlithography projection exposure device (200), comprising an illumination device and a projection lens, characterized in that: The projection exposure apparatus comprises an optical system according to claim 23 or 24.

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