Projection exposure apparatus and method for semiconductor lithography

Abstract

The present invention relates to a projection exposure apparatus (1, 101) for semiconductor lithography, comprising at least one optical element (Mx, 117), wherein at least one actuator (44) for deforming the optically effective surface (33) of the optical element is disposed on the back side (43) of the optical element (Mx, 117), the actuator (44) is configured to apply a compressive or tensile force to the optical element (Mx, 117) perpendicular to the optically effective surface (33), and at least one actuator (44) is disposed within a notch (35, 53) of the body (30, 50) of the optical element (Mx, 117). The present invention relates to a method for fixing an actuator (44) in a notch (63) of a body (60) of an optical element (Mx, 117), the method comprising the steps of: preparing the actuator (44) and at least one radial clamping element (68); inserting the actuator (44) and the radial clamping element (68) into the notch (53), wherein the radial clamping element (68) is positioned between the actuator (44) and the inner surface (69) of the notch (53); and tightening the clamping element (68) for the purpose of fixing the actuator (44).

Description

Technical Field

[0001] This application claims the priority of German Patent Application No. 10 2022 211 226.1 filed on October 24, 2022, the content of which is incorporated herein by reference in its entirety.

[0002] The present invention relates to a projection exposure apparatus for semiconductor lithography having an optical element provided with an actuator, and a method of incorporating an actuator.

Background Art

[0003] A projection exposure apparatus for semiconductor technology is used to produce extremely fine structures, particularly on semiconductor components or other microstructured components. The operating principle of the above apparatus is based on producing very fine structures in the nanometer range by generally reducing and imaging the structure on a mask onto a structured target element provided with a photosensitive material called a wafer using a so-called reticle. The minimum dimension of the structure to be produced depends directly on the wavelength of the light used. In addition to light sources having emission wavelengths in the so-called DUV range of 100 nm to 300 nm, which are mainly used, the use of light sources having emission wavelengths of about a few nanometers, for example 1 nm to 120 nm, particularly about 13.5 nm, has been increasing in recent years. This wavelength range is also referred to as the EUV range.

[0004] The optical element used for imaging in the above applications must be positioned with the highest precision and / or possibly deformed in order to ensure sufficient imaging quality. In particular, an optical element in the form of a mirror is configured not only to be positioned with up to six degrees of freedom but also to deform the optically effective surface. The optically effective surface is the surface of the optical element on which the radiation used for imaging and exposure during the normal operation of the associated apparatus is incident.

[0005] In this case, deformation is brought about by an actuator positioned on the back side of the mirror opposite the optically effective surface. In principle, the actuator used can act on the optical element parallel to the optically effective surface, but also perpendicular to the optically effective surface. A corresponding configuration is disclosed in Patent Document 1. In the optical element disclosed in this document, the actuator acts on the optical element from the back side, i.e., from the opposite side of the optically effective surface, introducing a force perpendicular to the optically effective surface. According to the teachings in this document, a back plate is used as a counter bearing, on which the actuator is supported. However, as a result of using a back plate, the actuator becomes not optimally accessible for maintenance or repair purposes. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] German Patent Application Publication No. 10, 2020, 210, 773 Specification [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The object of the present invention is to provide an apparatus and a method that each overcomes the aforementioned drawbacks of the prior art. [Means for solving the problem]

[0008] This problem is solved by the apparatus and method having the features described in the independent claim. The dependent claims relate to advantageous developments and variations of the present invention.

[0009] The projection exposure apparatus for semiconductor lithography according to the present invention comprises at least one optical element, and at least one actuator for deforming the optically effective surface of the optical element is disposed on the back side of the optical element. In this case, the actuator is configured to apply a compressive or tensile force to the optical element perpendicular to the optically effective surface. According to the present invention, at least one actuator is disposed within a notch in the body of the optical element.

[0010] In this regard, the actuator can be connected to the main body via a bearing contact surface located within a notch. In particular, this connection between the actuator and the main body allows for the absorption of forces acting on the actuator during operation due to the elastic properties of the optical element material. In other words, the main body itself acts as a counter bearing for the actuator, eliminating the need for a back plate as is known from the prior art.

[0011] In one embodiment of the present invention, the optical element includes an intermediate disposed between the optical body and the main body. In this case, the optical body is the portion of the optical element that includes the optical surface. The intermediate provides the possibility of introducing further functionality to the optical element.

[0012] Therefore, there may be at least one cavity between the body and the optical body to at least partially mechanically separate the optical body from the body. For example, this can be achieved by a proper design of the intermediate body.

[0013] In particular, at least one cavity may be placed between the intermediate and the main body.

[0014] At least one actuator may extend at least partially into the cavity. It is also conceivable that at least one cavity has a sealed embodiment for at least one actuator. In the latter case, the advantage of the sealed embodiment of the cavity is that, for example, if the actuator is removed and cleaned with water, the cleaning fluid cannot enter the cavity, thus eliminating the need to dry the cavity before installing the actuator.

[0015] Another advantage of using an intermediate is that it may contain a channel for temperature control of the optical element. Here, it is advantageous that the intermediate is easier to process than, for example, the optical element or the main body, especially for the formation of the aforementioned channel.

[0016] The presence of a pin at the bottom of the notch, particularly in the intermediate section, which is mechanically connected to the actuator via an effective contact surface, allows for a degree of mechanical decoupling in a direction perpendicular to the actuator's direction of action. In this case, lateral deformation occurring during actuator operation is absorbed by the pin and not transmitted to the vicinity of the optically effective surface.

[0017] As a result of the distance between the optically effective surface and the effective contact surface being 5mm to 20mm, deformation of the optically effective surface can be achieved with a relatively small actuator force.

[0018] In one advantageous variant of the present invention, the bearing contact surface may be formed on the shoulder of the notch. In this case, for example, the bearing contact surface may be easily connected to the actuator by an adhesive connection.

[0019] A distance of 0mm to 500mm, preferably 0mm to 250mm, and particularly preferably 50mm to 150mm between the bearing contact surface and the back of the main body, can allow for particularly good access to the bearing contact surface, for example, for adhesive application.

[0020] In one advantageous variant of the present invention, at least one clamping element may be positioned between the actuator and the inner surface of the notch. In this regard, the clamping element should be understood to mean an element particularly suitable for securing the actuator within the notch by a clamping force.

[0021] In this regard, the clamping element can in particular be formed as a sleeve-shaped body. In this case, the outer surface of the clamping element can be adhered to the inner surface of the notch, and the inner surface of the clamping element can be adhered to the outer surface of the actuator, thus forming a frictional connection.

[0022] By including a shape memory alloy in the clamping element, a particularly effective and reversible connection between the actuator and the body can be formed. In this regard, the property of the shape memory alloy of exerting a large force even with a small volume is exploited.

[0023] A method for fixing an actuator within a notch of a body of an optical element according to the present invention comprises providing an actuator and at least one radial clamping element, inserting the actuator and the radial clamping element into the notch, the radial clamping element being arranged between the actuator and the inner surface of the notch, and clamping the clamping element to fix the actuator. and

[0024] In this regard, the clamping element can in particular be clamped by changing the temperature of the body or the clamping element.

[0025] If the clamping element includes a shape memory alloy, a relatively large force can be realized by a temperature change.

[0026] By pushing the actuator in the direction of the optically effective surface with a defined contact force before clamping the clamping element, it is possible to minimize or even completely eliminate the play that can occur between the actuator and the optical body or the intermediate body, so that this can be referred to as a play-free connection of the actuator.

[0027] Exemplary embodiments and variants of the present invention will be explained in more detail below based on the drawings.

Brief Description of the Drawings

[0028] [Figure 1] A schematic diagram of the meridian cross-section of a projection exposure apparatus for EUV projection lithography is shown. [Figure 2] A schematic diagram of the meridian cross-section of a projection exposure apparatus for DUV projection lithography is shown. [Figure 3] A first embodiment of the optical element according to the present invention is shown. [Figure 4] Another embodiment of the optical element according to the present invention is shown. [Figure 5] Another embodiment of the optical element according to the present invention is shown. [Modes for carrying out the invention]

[0029] In the following text, the essential components of the microlithography projection exposure apparatus 1 will be described illustratively, first with reference to Figure 1. The description of the basic structure of the projection exposure apparatus 1 and its components should be understood as non-exclusive.

[0030] One embodiment of the illumination system 2 of the projection exposure apparatus 1 includes, in addition to the radiation source 3, an illumination optical unit 4 that illuminates the object field of view 5 on the object surface 6. In an alternative embodiment, the light source 3 may be provided as a module separate from the rest of the illumination system. In this case, the illumination system does not include the light source 3.

[0031] A reticle 7 positioned in the object field of view 5 is exposed. The reticle 7 is held by a reticle holder 8. The reticle holder 8 is displaceable, particularly in the scanning direction, by a reticle displacement drive 9.

[0032] For illustrative purposes, Figure 1 shows an orthogonal xyz coordinate system. The x-direction extends perpendicular to the plane of the figure. The y-direction extends horizontally, and the z-direction extends vertically. In Figure 1, the scanning direction extends in the y-direction. The z-direction extends perpendicular to the object plane 6.

[0033] The projection exposure apparatus 1 includes a projection optical unit 10. The projection optical unit 10 functions to form an image of the object field of view 5 onto the image field of view 11 of the image plane 12. The image plane 12 extends parallel to the object surface 6. Alternatively, angles other than 0° are possible between the object surface 6 and the image plane 12.

[0034] The structure on the reticle 7 is imaged onto the photosensitive layer of the wafer 13, which is positioned in the image field 11 region of the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 is displaceable, particularly in the y-direction, by a wafer displacement drive 15. Firstly, the displacement of the reticle 7 by the reticle displacement drive 9, and secondly, the displacement of the wafer 13 by the wafer displacement drive 15, can be synchronized with each other.

[0035] Radiation source 3 is an EUV radiation source. Radiation source 3 emits EUV radiation 16, which is also referred to below as the radiation used, illumination radiation, or illumination light. The radiation used has wavelengths in the range of 5 nm to 30 nm. Radiation source 3 may be a plasma source, such as a laser-generated plasma (LPP) source or a gas discharge plasma (GDPP) source. It may also be a synchrotron-based radiation source. Radiation source 3 may be a free electron laser (FEL).

[0036] Illumination radiation 16 emitted from the radiation source 3 is focused by a collector 17. The collector 17 may be a collector having one or more elliptical and / or hyperbolic reflecting surfaces. Illumination radiation 16 may be incident on at least one reflecting surface of the collector 17 obliquely (GI), i.e., at an incident angle greater than 45° with respect to the direction of the normal to the mirror surface, or perpendicularly (NI), i.e., at an incident angle less than 45°. The collector 17 may be structured and / or coated, firstly to optimize reflectivity for the radiation used, and secondly to suppress external light.

[0037] Downstream of the collector 17, the illumination radiation 16 propagates through the intermediate focal point of the intermediate focal plane 18. The intermediate focal plane 18 may represent the separation point between the radiation source module, which includes the radiation source 3 and the collector 17, and the illumination optical unit 4.

[0038] The illumination optical unit 4 comprises a deflection mirror 19 and a first facet mirror 20 positioned downstream of it in the beam path. The deflection mirror 19 may be a planar deflection mirror or a mirror having a beam influence effect beyond a pure deflection effect. Alternatively or additionally, the deflection mirror 19 may be in the form of a spectral filter that separates the wavelength of light used by the illumination radiation 16 from external light of different wavelengths. When the first facet mirror 20 is positioned on the plane of the illumination optical unit 4 that is optically conjugate to the object plane 6 as a field of view, this facet mirror is also referred to as a field of view facet mirror. The first facet mirror 20 includes a plurality of individual first facets 21, which are also referred to below as field of view facets. Figure 1 shows only some of these facets 21 as examples.

[0039] The first facet 21 may take the form of a macroscopic facet, particularly a rectangular facet or a facet having an arc-shaped edge contour or a partially circular edge contour. The first facet 21 may take the form of a planar facet, or a facet that is curved in a convex or concave shape.

[0040] For example, as is known from German Patent Application Publication No. 10 2008 009 600, the first facet 21 itself can also be composed of multiple individual mirrors, particularly multiple micromirrors. The first facet mirror 20 can take the form of a micro-electromechanical system (MEMS system). See German Patent Application Publication No. 10 2008 009 600 for further details.

[0041] Between the collector 17 and the deflection mirror 19, the illumination radiation 16 travels horizontally, i.e., in the y-direction.

[0042] In the beam path of the illumination optical unit 4, a second facet mirror 22 is positioned downstream of the first facet mirror 20. When the second facet mirror 22 is positioned on the pupil plane of the illumination optical unit 4, this facet mirror is also referred to as a pupil facet mirror. The second facet mirror 22 can also be positioned away from the pupil plane of the illumination optical unit 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also referred to as a specular reflector. Specular reflectors are known from U.S. Patent Application Publication No. 2006 / 0132747, European Patent No. 1614008, and U.S. Patent No. 6,573,978.

[0043] The second facet mirror 22 includes multiple second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

[0044] Similarly, the second facet 23 may be a macroscopic facet having, for example, a circular, rectangular, or hexagonal boundary, or it may be a facet composed of micromirrors. In this regard, see German Patent Application Publication No. 10 2008 009 600.

[0045] The second facet 23 may have a planar reflective surface or a curved reflective surface that is convex or concave.

[0046] Therefore, the illumination optical unit 4 forms a dual-facet system. This basic principle is also called a fly-eye condenser (fly-eye integrator).

[0047] It may be advantageous not to precisely position the second facet mirror 22 on a plane optically conjugate to the pupil plane of the projection optical unit 10. In particular, the pupil facet mirror 22 may be positioned at an angle to the pupil plane of the projection optical unit 10, for example, as described in German Patent Application Publication No. 10 2017 220 586.

[0048] The individual first facets 21 are imaged into the object field of view 5 using the second facet mirror 22. The second facet mirror 22 is the last beam shaping mirror or, in fact, the final mirror for the illumination radiation 16 in the beam path upstream of the object field of view 5.

[0049] In yet another embodiment of the illumination optical unit 4 (not shown), a transfer optical unit, which contributes particularly to the imaging of the first facet 21 onto the object field of view 5, can be positioned in the beam path between the second facet mirror 22 and the object field of view 5. The transfer optical unit may have exactly one mirror, or two or more mirrors positioned before and after the beam path of the illumination optical unit 4. The transfer optical unit may, in particular, include one or two perpendicular incidence mirrors (NI mirrors) and / or one or two oblique incidence mirrors (GI mirrors).

[0050] In the embodiment shown in Figure 1, the illumination optical unit 4 has exactly three mirrors downstream of the collector 17, specifically a deflection mirror 19, a field of view facet mirror 20, and a pupil facet mirror 22.

[0051] In yet another embodiment of the illumination optical unit 4, the deflection mirror 19 can be omitted, so the illumination optical unit 4 may have exactly two mirrors downstream of the collector 17, specifically a first facet mirror 20 and a second facet mirror 22.

[0052] The imaging of the first facet 21 onto the object surface 6 by the second facet 23, or by using the second facet 23 and the transfer optics unit, is generally only an approximate image.

[0053] The projection optical unit 10 includes a plurality of mirrors Mi, which are numbered sequentially according to their arrangement in the beam path of the projection exposure apparatus 1.

[0054] In the example shown in Figure 1, the projection optical unit 10 includes six mirrors M1 to M6. Substitution with four, eight, ten, twelve, or any other number of mirrors Mi is equally possible. The second-to-last mirror M5 and the last mirror M6 each have a through aperture for illumination radiation 16. The projection optical unit 10 is a double-shielded optical unit. The projection optical unit 10 has an image-side numerical aperture greater than 0.5 and may be greater than 0.6, for example, 0.7 or 0.75.

[0055] The reflective surface of mirror Mi may be in the form of a free-form surface without an axis of rotational symmetry. Alternatively, the reflective surface of mirror Mi may be designed as an aspherical surface with exactly one axis of rotational symmetry of the reflective surface shape. Similar to the mirrors of the illumination optical unit 4, mirror Mi may have a highly reflective coating for illumination radiation 16. These coatings may be designed in particular as multilayer coatings having alternating layers of molybdenum and silicon.

[0056] The projection optical unit 10 has a large object-image offset in the y-direction between the y-coordinate of the center of the object field of view 5 and the y-coordinate of the center of the image field of view 11. This object-image offset in the y-direction may be approximately the same magnitude as the z-distance between the object plane 6 and the image plane 12.

[0057] In particular, the projection optics unit 10 can have an anamorphic design. Specifically, it has different imaging scales βx and βy in the x and y directions. The two imaging scales βx and βy of the projection optics unit 10 are preferably (βx, βy) = (+ / -0.25, + / -0.125). A positive imaging scale β means imaging without image inversion. A negative sign for the imaging scale β means imaging with image inversion.

[0058] As a result, the projection optical unit 10 is reduced in size in the x-direction, i.e., in the direction perpendicular to the scanning direction, at a ratio of 4:1.

[0059] The projection optical unit 10 reduces its size in the y-direction, i.e., in the scanning direction, at a ratio of 8:1.

[0060] Other imaging scales are also possible. Imaging scales with the same sign and absolute value in the x and y directions, for example, 0.125 or 0.25 absolute value, are also possible.

[0061] The number of intermediate image planes in the x and y directions in the beam path between the object field of view 5 and the image field of view 11 may be the same or may differ depending on the embodiment of the projection optical unit 10. An example of a projection optical unit with a different number of such intermediate images in the x and y directions is known from U.S. Patent Application Publication No. 2018 / 0074303.

[0062] Each pupil facet 23 is assigned to exactly one of the field of view facets 21 to form an illumination channel that illuminates the object field of view 5. In particular, this allows illumination according to Köhler's principle. The distant field of view is decomposed into multiple object fields of view 5 using the field of view facets 21. Each of the field of view facets 21 generates multiple images at intermediate focal points in the pupil facet 23 that is assigned to it.

[0063] The field of view facets 21 are each imaged onto the reticle 7, overlapping with the assigned pupil facets 23, to illuminate the object field of view 5. The illumination of the object field of view 5 is particularly uniform, preferably with an error in uniformity of less than 2%. Field of view uniformity can be achieved by overlapping different illumination channels.

[0064] The illumination of the entrance pupil of the projection optical unit 10 can be geometrically defined by the arrangement of the pupil facets. By selecting the illumination channels to guide light, particularly a subset of the pupil facets, the intensity distribution in the entrance pupil of the projection optical unit 10 can be set. This intensity distribution is also referred to as the illumination setting.

[0065] Similarly desirable pupil uniformity in a defined illuminated area of ​​the illumination pupil of the illumination optical unit 4 can be achieved by redistributing the illumination channels.

[0066] Further aspects and details of the illumination of the object field of view 5, particularly the entrance pupil of the projection optical unit 10, will be described below.

[0067] The projection optics unit 10 may have a concentric entrance pupil, which can be made accessible or inaccessible.

[0068] The entrance pupil of the projection optical unit 10 cannot generally be accurately illuminated using the pupil facet mirror 22. When imaging is performed by the projection optical unit 10, which telecentrically images the center of the pupil facet mirror 22 onto the wafer 13, the aperture rays often do not intersect at a single point. However, it is possible to find a plane where the distance between pairs of aperture rays is minimized. This plane represents the entrance pupil or its conjugate plane in real space. In particular, this plane exhibits a finite curvature.

[0069] The projection optics unit 10 may have different entrance pupil positions for the tangential beam path and the sagittal beam path. In this case, an imaging element, particularly an optical component of the transfer optics unit, should be placed between the second facet mirror 22 and the reticle 7. This optical element can be used to account for the difference in positions between the tangential and sagittal entrance pupils.

[0070] In the arrangement of the components of the illumination optical unit 4 shown in Figure 1, the pupil facet mirror 22 is positioned on a plane conjugate to the entrance pupil of the projection optical unit 10. The field of view facet mirror 20 is positioned at an angle with respect to the object plane 6. The first facet mirror 20 is positioned at an angle with respect to the arrangement plane defined by the deflection mirror 19.

[0071] The first facet mirror 20 is positioned at an angle with respect to the arrangement plane defined by the second facet mirror 22.

[0072] Figure 2 schematically shows a meridian cross-section of yet another projection exposure apparatus 101 for DUV projection lithography, in which the present invention can similarly be used.

[0073] The structure and imaging principle of the projection exposure apparatus 101 are equivalent to those described in Figure 1. Identical components are indicated by reference numerals that are 100 higher than those in Figure 1; that is, the reference numerals in Figure 2 begin with 101.

[0074] Unlike the EUV projection lithography apparatus 1 described in Figure 1, the wavelength of the DUV radiation 116 used as the light source is in the range of 100 nm to 300 nm, particularly large at approximately 193 nm. Therefore, refraction, diffraction, and / or reflection optical elements 117 such as lens elements, mirrors, prisms, and end plates can be used for imaging or illumination in the DUV projection lithography apparatus 101. In this case, the projection lithography apparatus 101 essentially comprises an illumination system 102, a reticle holder 108 that houses and precisely positions a reticle 107 having a structure that determines the subsequent structure on the wafer 113, a wafer holder 114 that holds, moves, and precisely positions the wafer 113, and a projection lens 110 having a plurality of optical elements 117. The optical elements 117 are held by mounts 118 on the lens housing 119 of the projection lens 110.

[0075] The illumination system 102 supplies DUV radiation 116 necessary for imaging the reticle 107 onto the wafer 113. Lasers, plasma sources, etc., can be used as sources for this radiation 116. The radiation 116 is shaped by optical elements in the illumination system 102 so that when incident on the reticle 107, the DUV radiation 116 has desired characteristics in terms of diameter, polarization, wavefront shape, etc.

[0076] Aside from the additional use of refractive optical elements 117 such as lens elements, prisms, and end plates, the structure of the downstream projection optical unit 101 having a lens housing 119 is not fundamentally different from the structure described in Figure 1, and therefore will not be described in further detail.

[0077] Figure 3 shows a first embodiment of the optical element according to the present invention used in the projection exposure apparatus 1, 101 described in Figures 1 and 2. In the illustrated example, the optical element takes the form of a deformable mirror Mx. The mirror Mx comprises a body 30, an intermediate 31, and an optical body 32, and an optical effective surface 33 is formed on the optical body, to which the radiation used during the operation of the associated projection exposure apparatus 1, 101, i.e., the radiation used for imaging and exposure, is incident. In the embodiment shown in Figure 3, the intermediate 31 includes a flow channel 34 for temperature control of the mirror Mx and a notch in the direction of the body, thereby forming a cavity that helps in partial mechanical decoupling between the intermediate 31 and the body 30 in the form of a decoupling pocket 42, resulting in an improved method for deforming the optical effective surface 33. For example, the three bodies 30, 31, and 32 can be connected to each other by bonding, but other connection techniques are also possible. The multi-component structure of the mirror Mx is advantageous because, as described above, functional structures such as the flow channel 34 can be more easily realized from a manufacturing perspective. A notch, which takes the form of a perforation 35, is located on the back side 43 of the body 30 opposite the optically effective surface 33, into which an actuator 44 that deforms the optically effective surface 33 of the mirror Mx is introduced. The perforation 35 includes a shoulder 37, which represents the transition from the initial large hole diameter to the small hole diameter of the perforation 35. The shoulder 37 includes a first bearing contact surface 38, where the actuator 44 is connected to the body 30 with a corresponding contact force. The perforation 35 extends to an intermediate body 31, and a pin having an effective contact surface 41 for connecting to another contact surface of the actuator 44 is formed at the bottom of the perforation. The pin 40 is useful for mechanical decoupling, for example, when the actuator 44 and the intermediate body 31 are bonded together. In such cases, the pin 40 absorbs, for example, lateral stresses, so that there is no deformation of the optically effective surface 33 due to these stresses, or the effects of these stresses are reduced. The tolerance chains of individual feature parts that determine position, such as the effective contact surface 41 of the pin 40 or the bearing contact surface 38 of the shoulder portion 37, are designed so that the thickness of the adhesive connection at the pin 40 can be minimized. The tolerance is compensated by an adhesive connection placed between the actuator 44 and the shoulder portion 37. Alternatively, the tolerance can also be compensated by a so-called spacer, i.e., a washer manufactured to a predetermined thickness.A major advantage of positioning the actuator 44 within the perforation 35 starting from the back side 43 of the mirror is that the actuator 44 can always be removed and replaced from the mirror Mx with reasonable load, for example by local heating of the adhesive connection. In this case, to protect the coating formed on the optically effective surface 33, a temperature-controlled medium can be flowed through the channel 34 formed in the intermediate 31 while the adhesive connection is heating.

[0078] The connection of the actuator 44 to the mirror Mx can be changed by modifying several parameters. For example, the distance between the effective contact surface 41 of the pin 40 and the optically effective surface 33 can be changed, and this distance can range from 5 mm to 20 mm depending on the design. To facilitate the replacement of the actuator 44, the adhesive connection between the actuator 44 and the bearing contact surface 38 of the shoulder portion 37 can be positioned as close as possible to the back side 43 of the main body 30 to improve accessibility. Similarly, the position of the flow path 34 of the intermediate body 31 can be changed depending on the thermal load caused by the absorption of light used by the optically effective surface 33 and the waste heat of the actuator 44. It is also conceivable that the flow path 34 adopts the function of a decoupling pocket 42.

[0079] Figure 4 shows yet another embodiment of an optical element in the form of a mirror Mx, which includes a body 50, an intermediate 51, and an optical body 52 having an optically effective surface 33. The body 50 includes a notch in the form of a perforation 53 having a certain diameter and a flat bottom 58. A cavity in the form of a decoupling pocket 55 and a pin 56 for decoupling lateral forces are formed on the side of the body 50 facing the intermediate 51, as already described with respect to Figure 3. In the illustrated example, the effective contact surface 57 of the pin 56 acts directly on the underside of the intermediate 51 facing the body 50. The direction of action of an actuator (not shown) is indicated by an arrow. The actuator is connected to the body 50 via the bottom 58 of the perforation 53. In the arrangement described with respect to Figure 4, the decoupling pocket 55 is completely closed. If the mirror Mx is cleaned, for example from its back side, the cleaning medium cannot reach the decoupling pocket 55, thus simplifying the overall cleaning process. The sealed embodiment of the decoupling pocket 55 eliminates the need for cleaning it. Furthermore, as a result of the illustrated embodiment of the decoupling pocket 55, the distance between the pin 56 and the optically effective surface 33 can be further reduced, which may be advantageous depending on the design.

[0080] Figure 5 shows yet another embodiment of the present invention, in which the mirror Mx comprises a body 60 and an optical body 61 having an optically effective surface 62. A cavity, which serves as a decoupling pocket 71, is formed between the body 60 and the optical body 61. In this case as well, the body 60 includes a hole 63 having a shoulder 64, and a sleeve 68 made of shape memory alloy (SMA) is placed in the hole 63 as a clamping element. To prepare for the mounting of the actuator 66, the sleeve 68 is pushed into the hole 63 until the sleeve contact surface 65 of the edge 70 of the sleeve 68, which corresponds to the shoulder 64 of the hole 63, contacts the shoulder 64. In this case, the sleeve 68 is in an open operating state. The actuator 66 is then inserted into the sleeve 68 and pressed against the back side 72 of the optical body 61 opposite to the optically effective surface 62 with a specified contact force F, shown as an arrow in Figure 5, thereby ensuring a play-free connection between the actuator 66 and the optical body 61. When a contact force F is applied, for example, by heating, a change in the microstructure of the material of the sleeve 68 is promoted, and the sleeve thereby enters a closed operating state. The sleeve 68 securely clamps the outer surface 67 of the actuator 66 to the inner surface 69, which acts as the bearing contact surface of the borehole 63 in the main body 60. To disconnect the connection, the sleeve 68 can be returned to an open operating state by heating and the resulting change in the microstructure of the material of the sleeve 68. The advantages of using a sleeve 68 made of shape memory alloy are that the sleeve 68 can be reused and relatively quick installation is possible as a result of directly switching the sleeve 68 from an open operating state to a closed operating state. Furthermore, shape memory alloys have the advantage of significantly low long-term drift and virtually no aging. In addition, compared to other possible connection elements, such as piezoactive or electrostrictive actuators, shape memory alloys are characterized by a large amount of work per unit volume. This results in a very small space required to fix the actuator 66. In principle, the embodiment shown in Figure 5 can also incorporate the flow path 34 as described with respect to Figures 3 and 4. Alternatively, a so-called one-way shape memory alloy can be used, which, when activated, clamps the actuator 66 into the borehole 63 but does not open even when reheated.In that case, the sleeve 68 can only be opened or removed mechanically. As mentioned above, it still has the advantage of requiring very little space. [Explanation of symbols]

[0081] 1. Projection exposure apparatus 2. Lighting System 3 Radiation source 4. Illumination Optical Unit 5 Object field of view 6 Object plane 7 Reticle 8 Reticle holders 9. Reticle displacement drive 10 Projection Optical Unit 11 Image field 12 Image plane 13 wafers 14 Wafer holder 15 Wafer Displacement Drive 16 EUV radiation 17 Collector 18 Intermediate focal plane 19. Polarizing mirror 20 Faceted Mirror 21 Facets 22 Faceted Mirror 23 Facets 30 Main Unit 31 Intermediates 32 Optical body 33 Optically Effective Surface 34 Flow channels 35 perforation 37 Shoulder 38 Contact surface of the shoulder 40 pins 41 Pin contact surface 42 Decoupling Pockets 43 Back of the main unit 44 Actuators 50 Main Unit 51 Intermediate 52 Optical body 53 Perforation 55 Decoupling Pockets 56 pins 57 Pin contact surface 58 Bottom of the perforation 60 Main Unit 61 Optical body 62 Optically Effective Surface 63 Perforation 64 Perforated shoulder 65 SMA sleeve contact surface 66 Actuators 67 Outer surface of the actuator 68 SMA sleeves 69 Inside of the main body 70 Edge 71 Decoupling Pocket 101 Projection exposure apparatus 102 Lighting System 107 Reticle 108 Reticle Holder 110 Projection Optical Unit 113 wafers 114 Wafer Holder 116 DUV radiation 117 Optical elements 118 mount 119 Lens Housing M1~M6 Mirror F Contact force before fixing

Claims

1. A projection exposure apparatus (1, 101) for semiconductor lithography, comprising at least one optical element (Mx, 117), wherein at least one actuator (44) for deforming the optical effective surface (33) of the optical element is positioned on the back side (43) of the optical element (Mx, 117), and the actuator (44) is configured to apply a compressive or tensile force to the optical element (Mx, 117) perpendicular to the optical effective surface (33), in the projection exposure apparatus (1, 101), A projection exposure apparatus characterized in that the at least one actuator (44) is positioned within a notch (35, 53) of the body (30, 50) of the optical element (Mx, 117), and there is at least one cavity (42, 55, 71) between the body (30, 50, 61) and the optical body (32, 52, 61) for at least partially mechanically separating the optical body (32, 52, 61) from the body (30, 50, 60), and the at least one actuator (44) extends at least partially into the cavity (42, 71).

2. In the projection exposure apparatus (1, 101) according to claim 1, The projection exposure apparatus is characterized in that the actuator (44) is connected to the main body (30, 50) by bearing contact surfaces (38, 69) located within the notches (35, 53).

3. In the projection exposure apparatus (1, 101) according to claim 1 or 2, The projection exposure apparatus is characterized in that the optical element (Mx, 117) includes an intermediate body (31, 51) disposed between the optical body (32, 52) and the main body (30, 50).

4. In the projection exposure apparatus (1, 101) according to any one of claims 1 to 3, A projection exposure apparatus characterized in that at least one cavity (42, 55) is positioned between the intermediate (31, 51) and the main body (30, 50, 60).

5. In the projection exposure apparatus (1, 101) according to claim 1, A projection exposure apparatus characterized in that the at least one cavity (55) is isolated from the at least one actuator (44).

6. In the projection exposure apparatus (1, 101) according to any one of claims 3 to 5, The projection exposure apparatus is characterized in that the intermediate (31) includes a flow path (34) for temperature control of the optical element (Mx, 117).

7. In the projection exposure apparatus (1, 101) according to any one of claims 1 to 6, A projection exposure apparatus characterized in that a pin (40) is located at the bottom of the notch (35) and is mechanically connected to the actuator (44) via an effective contact surface (41).

8. In the projection exposure apparatus (1, 101) according to claim 7 and any one of claims 3 to 6, The projection exposure apparatus is characterized in that the pin (40) is formed on the intermediate (31).

9. In the projection exposure apparatus (1, 101) according to claim 7 or 8, A projection exposure apparatus characterized in that the distance between the optically effective surface (33) and the effective contact surface (41) is 5 mm to 20 mm.

10. In the projection exposure apparatus (1, 101) according to any one of claims 2 to 9, A projection exposure apparatus characterized in that the bearing contact surface (38) is formed on the shoulder portion (37) of the notch (35).

11. In the projection exposure apparatus (1, 101) according to claim 1, A projection exposure apparatus characterized in that the bearing contact surface (38) is connected to the actuator (44) by adhesive connection.

12. In the projection exposure apparatus (1, 101) according to any one of claims 10 or 11, A projection exposure apparatus characterized in that the distance between the bearing contact surface (38) and the back side of the main body is 0 mm to 500 mm, preferably 0 mm to 250 mm, and particularly preferably 50 mm to 150 mm.

13. In the projection exposure apparatus (1, 101) according to any one of claims 1 to 12, A projection exposure apparatus characterized in that at least one clamping element (68) is positioned between the actuator (44) and the inner surface (69) of the notch (53).

14. In the projection exposure apparatus (1, 101) according to claim 13, The projection exposure apparatus is characterized in that the clamp element (68) is formed as a sleeve-shaped body.

15. In the projection exposure apparatus (1, 101) according to claim 13 or 14, The projection exposure apparatus is characterized in that the clamp element (68) includes a shape memory alloy.

16. A method for fixing an actuator (44) within a notch (63) of the main body (60) of an optical element (Mx, 117), The steps include preparing the actuator (44) and at least one radial clamping element (68), The step is to insert the actuator (44) and the radial clamping element (68) into the notch (53), wherein the radial clamping element (68) is positioned between the actuator (44) and the inner surface (69) of the notch (53), The steps include tightening the clamp element (68) for the purpose of fixing the actuator (44) and Methods that include...

17. In the method according to claim 16, A method for tightening the clamp element (68) by changing the temperature of the main body (60) or the clamp element (68).

18. In the method according to claim 17, The clamping element (68) comprises a shape memory alloy, in a method.

19. In the method according to any one of claims 16 to 18, A method of pushing the actuator (66) in the direction of the optically effective surface (62) with a specified contact force (F) before tightening the clamp element (68).

Images