WO2023237452A1

WO2023237452A1 - Component for a projection exposure apparatus for semiconductor lithography and projection exposure apparatus

Info

Publication number: WO2023237452A1
Application number: PCT/EP2023/064889
Authority: WO
Inventors: Michael GROISS
Original assignee: Carl Zeiss Smt Gmbh
Priority date: 2022-06-08
Filing date: 2023-06-02
Publication date: 2023-12-14
Also published as: TW202349134A; DE102022205815A1

Abstract

The invention relates to a component (50, 70) for a projection exposure apparatus (1, 101) for semiconductor lithography comprising at least two structural parts (51, 55, 71, 75) which are connected to one another, it being possible for the structural parts (51, 55, 71, 75) to be positioned relative to one another in at least one plane and the position and alignment being determined via two contact faces (53, 54, 73, 74), In this respect, the connection has a form-fitting design in the at least one plane. Furthermore, the invention relates to a projection exposure apparatus (1, 101) for semiconductor lithography.

Description

Component for a projection exposure apparatus for semiconductor lithography and projection exposure apparatus

The present application claims the priority of the German patent application DE 10 2022 205 815.1 of June 8, 2022, the content of which is fully incorporated herein by reference.

The invention relates to a component for a projection exposure apparatus for semiconductor lithography according to the preamble of claim 1 . Furthermore, the invention relates to a projection exposure apparatus for semiconductor lithography.

Projection exposure apparatuses are subject to extremely stringent requirements in respect of imaging accuracy, which is crucially dependent on the positioning of the optical elements of a projection exposure apparatus.

These requirements increase from one generation to the next and also have a direct effect on the positioning of structural parts, such as actuators and sensors or end stops for aligning and delimiting the movement of optical elements of the projection exposure apparatus. The combination of high accuracy and high positional stability in the event of to some extent high loading, such as unplanned collisions with an end stop owing to a malfunction of the actuation or loading caused by earthquakes lead to the highly precise connections known from the prior art, which are based on a frictional engagement, between two structural parts often no longer being sufficient to meet these requirements.

It is an object of the present invention to provide a device which eliminates the above-described disadvantages of the prior art.

This object is achieved by a device having the features of independent claim 1 . The dependent claims relate to advantageous developments and variants of the invention.

A component according to the invention for a projection exposure apparatus for semiconductor lithography comprises at least two structural parts which are connected to one another, it being possible for the structural parts to be positioned relative to one another in at least one plane and the position and alignment being determined via two contact faces. According to the invention, the connection has a form-fitting design in the at least one plane. The form-fitting design of the connection in the plane can have the effect that a translational movement in the x/y direction, that is to say parallel to the plane, and a rotation about the z axis, that is to say about an axis perpendicular to the plane, can be prevented.

Particularly precise fixing of the structural parts with respect to one another can be achieved in particular in that the angle between the two contact faces is in a range between 60° and 120°, in particular amounts to 90°. In particular in the last- mentioned case, the position of the two structural parts relative to one another in the x direction and the y direction can be set independently of one another by adapting the respective corresponding contact face.

Adaptations in terms of the positioning or alignment of the structural parts can be performed, for example, in that a spacer element is arranged on at least one of the contact faces between the structural parts.

The measures according to the invention make it possible in particular to ensure that the structural parts are aligned relative to one another with a tolerance of less than 67 mrad and less than 30 pm.

In a particularly advantageous variant of the invention, in the case of one of the two components, the two contact faces have different lengths. In this case, the longer contact face has the effect of better positioning with regard to a rotation about the z axis and furthermore provides a longer lever arm, which takes up a moment acting in the plane better than a short lever arm does and thus reduces the loading on the contact point.

In particular, three contact faces may be formed between the two structural parts.

Since a wedge is arranged between the structural parts, fixing of the two structural parts relative to one another can be achieved particularly easily. As an alternative or in addition to this, the structural parts may also be connected to one another with screws.

It is particularly advantageous when at least one, in particular two contact faces of one of the structural parts has a decoupling means. In this case, production-related angular errors can be compensated by the decoupling means. In this respect, the decoupling means ensure abutment over the entire surface area on all sides.

Exemplary embodiments and variants of the invention will be explained in more detail below with reference to the drawing, in which: figure 1 schematically shows a meridional section through a projection exposure apparatus for EUV projection lithography, figure 2 schematically shows a meridional section through a projection exposure apparatus for DUV projection lithography, figure 3 shows a solution known from the prior art, figure 4 shows a first exemplary embodiment of a connection according to the invention, figure 5 shows a further exemplary embodiment of a connection according to the invention, and figure 6 shows a further embodiment of a connection according to the invention.

The essential integral parts of a microlithographic projection exposure apparatus 1 are described in exemplary fashion below initially with reference to figure 1 . The description of the fundamental structure of the projection exposure apparatus 1 and the integral parts thereof is understood here to be non-limiting.

An embodiment of an illumination system 2 of the projection exposure apparatus 1 has, in addition to a radiation source 3, an illumination optical unit 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 may also be provided as a module separate from the rest of the illumination system. In this case, the illumination system does not comprise the light source 3. A reticle 7 arranged in the object field 5 is illuminated. The reticle 7 is held by a reticle holder 8. The reticle holder 8 is displaceable, in particular in a scanning direction, by way of a reticle displacement drive 9.

A Cartesian xyz-coordinate system is shown in Figure 1 for explanation purposes. The x direction runs perpendicularly to the plane of the drawing. The y direction runs horizontally, and the z direction runs vertically. The scanning direction runs in the y direction in figure 1. The z direction runs perpendicularly to the object plane 6.

The projection exposure apparatus 1 comprises a projection optical unit 10. The projection optical unit 10 serves for imaging the object field 5 into an image field 11 in an image plane 12. The image plane 12 extends parallel to the object plane 6. Alternatively, an angle that differs from 0° between the object plane 6 and the image plane 12 is also possible.

A structure on the reticle 7 is imaged onto a light-sensitive layer of a wafer 13 arranged in the region of the image field 11 in the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 is displaceable by way of a wafer displacement drive 15, in particular in the y direction. The displacement, firstly, of the reticle 7 by way of the reticle displacement drive 9 and, secondly, of the wafer 13 by way of the wafer displacement drive 15 can be implemented so as to be mutually synchronized.

The radiation source 3 is an EUV radiation source. The radiation source 3 emits, in particular, EUV radiation 16, which is also referred to below as used radiation, illumination radiation or illumination light. In particular, the used radiation has a wavelength in the range between 5 nm and 30 nm. The radiation source 3 can be a plasma source, for example an LPP (laser produced plasma) source or a GDPP (gas discharge produced plasma) source. It may also be a synchrotron-based radiation source. The radiation source 3 may be a free electron laser (FEL).

The illumination radiation 16 emerging from the radiation source 3 is focused by a collector 17. The collector 17 may be a collector with one or more ellipsoidal and/or hyperboloidal reflection surfaces. The illumination radiation 16 can be incident on the at least one reflection surface of the collector 17 with grazing incidence (Gl), which is to say at angles of incidence of greater than 45° relative to the direction of the normal to the mirror surface, or with normal incidence (Nl), which is to say at angles of incidence of less than 45°. The collector 17 can be structured and/or coated firstly for optimizing its reflectivity for the used radiation and secondly for suppressing stray light.

Downstream of the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 can represent a separation between a radiation source module, having the radiation source 3 and the collector 17, and the illumination optical unit 4.

The illumination optical unit 4 comprises a deflection mirror 19 and, downstream thereof in the beam path, a first facet mirror 20. The deflection mirror 19 may be a plane deflection mirror or, alternatively, a mirror with a beam-influencing effect going beyond a pure deflection effect. As an alternative or in addition, the deflection mirror 19 may be in the form of a spectral filter that separates a used light wavelength of the illumination radiation 16 from stray light of a wavelength deviating therefrom. If the first facet mirror 20 is arranged in a plane of the illumination optical unit 4 that is optically conjugate to the object plane 6 as a field plane, it is also referred to as a field facet mirror. The first facet mirror 20 comprises a multiplicity of individual first facets 21 , which are also referred to below as field facets. Figure 1 depicts only some of said facets 21 by way of example.

The first facets 21 can be in the form of macroscopic facets, in particular in the form of rectangular facets or in the form of facets with an arcuate peripheral contour or a peripheral contour formed as partly circular. The first facets 21 may be in the form of plane facets or alternatively as facets with convex or concave curvature.

As is known for example from DE 102008 009 600 A1 , the first facets 21 themselves can also each be composed of a multiplicity of individual mirrors, in particular a multiplicity of micromirrors. The first facet mirror 20 may in particular be in the form of a microelectromechanical system (MEMS system). For details, reference is made to DE 10 2008 009 600 A1. The illumination radiation 16 travels horizontally, that is to say longitudinally with respect to the y direction, between the collector 17 and the deflection mirror 19.

In the beam path of the illumination optical unit 4, a second facet mirror 22 is arranged downstream of the first facet mirror 20. If the second facet mirror 22 is arranged in a pupil plane of the illumination optical unit 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 can also be arranged at a distance from a 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 US 2006/0132747 A1 , EP 1 614 008 B1 , and US 6,573,978.

The second facet mirror 22 comprises a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

The second facets 23 may likewise be macroscopic facets, which may for example have a round, rectangular or else hexagonal periphery, or may alternatively be facets composed of micromirrors. In this regard, reference is likewise made to DE 102008 009 600 A1 .

The second facets 23 may have plane reflection surfaces or alternatively reflection surfaces with a convex or concave curvature.

The illumination optical unit 4 consequently forms a double-faceted system. This fundamental principle is also referred to as a fly's eye condenser (fly's eye integrator).

It can be advantageous to arrange the second facet mirror 22 not exactly in a plane that is optically conjugate to a pupil plane of the projection optical unit 10. In particular, the pupil facet mirror 22 can be arranged so as to be tilted relative to a pupil plane of the projection optical unit 10, as is described, for example, in DE 10 2017 220 586 A1.

The individual first facets 21 are imaged into the object field 5 using the second facet mirror 22. The second facet mirror 22 is the last beam-shaping mirror or indeed the last mirror for the illumination radiation 16 in the beam path upstream of the object field 5. In a further embodiment, not illustrated, of the illumination optical unit 4, a transfer optical unit can be arranged in the beam path between the second facet mirror 22 and the object field 5, said transfer optical unit contributing in particular to the imaging of the first facets 21 into the object field 5. The transfer optical unit may comprise exactly one mirror, but alternatively also comprise two or more mirrors, which are arranged one behind the other in the beam path of the illumination optical unit 4. The transmission optical unit can in particular comprise one or two normal-incidence mirrors (Nl mirrors) and/or one or two grazing-incidence mirrors (Gl mirrors).

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

The deflection mirror 19 can also be dispensed with in a further embodiment of the illumination optical unit 4, and so the illumination optical unit 4 can then have exactly two mirrors downstream of the collector 17, specifically the first facet mirror 20 and the second facet mirror 22.

The imaging of the first facets 21 into the object plane 6 by means of the second facets 23 or using the second facets 23 and a transfer optical unit is often only approximate imaging.

The projection optical unit 10 comprises a plurality of mirrors Mi, which are consecutively numbered in accordance with their arrangement in the beam path of the projection exposure apparatus 1 .

In the example illustrated in figure 1 , the projection optical unit 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or any other number of mirrors Mi are likewise possible. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 16. The projection optical unit 10 is a doubly obscured optical unit. The projection optical unit 10 has an imageside numerical aperture which is greater than 0.5 and which can also be greater than 0.6 and, for example, can be 0.7 or 0.75. Reflection surfaces of the mirrors Mi can be in the form of free-form surfaces without an axis of rotational symmetry. Alternatively, the reflection surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflection surface shape. Just like the mirrors of the illumination optical unit 4, the mirrors Mi can have highly reflective coatings for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

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

The projection optical unit 10 may in particular have an anamorphic form. In particular, it has different imaging scales |3x, |3y in the x and y directions. The two imaging scales |3x, |3y of the projection optical unit 10 are preferably (|3x, |3y) = (+/- 0.25, +/-0.125). A positive imaging scale [3 means imaging without image inversion. A negative sign for the imaging scale [3 means imaging with image inversion.

The projection optical unit 10 consequently leads to a reduction in size with a ratio of 4:1 in the x direction, which is to say in a direction perpendicular to the scanning direction.

The projection optical unit 10 leads to a reduction in size of 8:1 in the y direction, which is to say in the scanning direction.

Other imaging scales are likewise possible. Imaging scales with the same signs and the same absolute values in the x direction and y direction are also possible, for example with absolute values of 0.125 or 0.25.

The number of intermediate image planes in the x direction and in the y direction in the beam path between the object field 5 and the image field 11 can be the same or can differ depending on the form of the projection optical unit 10. Examples of projection optical units with different numbers of such intermediate images in the x and y directions are known from US 2018/0074303 A1 .

In each case one of the pupil facets 23 is assigned to exactly one of the field facets 21 to form a respective illumination channel for illuminating the object field 5. In particular, this can yield illumination according to the Kohler principle. The far field is decomposed into a multiplicity of object fields 5 with the aid of the field facets 21. The field facets 21 generate a plurality of images of the intermediate focus on the pupil facets 23 respectively assigned thereto.

By way of an assigned pupil facet 23, the field facets 21 are imaged in each case onto the reticle 7 in a manner overlaid on one another for the purpose of illuminating the object field 5. The illumination of the object field 5 is in particular as homogeneous as possible. It preferably has a uniformity error of less than 2%. The field uniformity can be achieved by overlaying different illumination channels.

The illumination of the entrance pupil of the projection optical unit 10 can be geometrically defined by an arrangement of the pupil facets. It is possible to set the intensity distribution in the entrance pupil of the projection optical unit 10 by selecting the illumination channels, in particular the subset of pupil facets, which guide light. This intensity distribution is also referred to as illumination setting.

A likewise preferred pupil uniformity in the region of sections of an illumination pupil of the illumination optical unit 4 that are illuminated in a defined manner can be achieved by a redistribution of the illumination channels.

Further aspects and details of the illumination of the object field 5 and in particular of the entrance pupil of the projection optical unit 10 are described below.

The projection optical unit 10 may in particular have a homocentric entrance pupil. The latter can be accessible. It can also be inaccessible.

The entrance pupil of the projection optical unit 10 generally cannot be illuminated exactly by means of the pupil facet mirror 22. In the case of imaging of 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 an area in which the spacing of the aperture rays, determined in pairwise fashion, is minimal. This area represents the entrance pupil or an area in real space that is conjugate thereto. In particular, this area has a finite curvature.

It may be the case that the projection optical unit 10 has different poses of the entrance pupil for the tangential beam path and for the sagittal beam path. In this case, an imaging element, in particular an optical component part of the transfer optical unit, should be provided between the second facet mirror 22 and the reticle 7. With the aid of this optical element, the different poses of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

In the arrangement that is illustrated in figure 1 of the components of the illumination optical unit 4, the pupil facet mirror 22 is arranged in an area conjugate to the entrance pupil of the projection optical unit 10. The field facet mirror 20 is tilted with respect to the object plane 6. The first facet mirror 20 is tilted with respect to an arrangement plane defined by the deflection mirror 19.

The first facet mirror 20 is tilted with respect to an arrangement plane defined by the second facet mirror 22.

Figure 2 schematically shows a meridional section through a further projection exposure apparatus 101 for DUV projection lithography, in which the invention can likewise be used.

The structure of the projection exposure apparatus 101 and the principle of the imaging are comparable with the construction and procedure described in figure 1 . Identical structural parts are denoted by a reference sign increased by 100 relative to figure 1 , which is to say the reference signs in figure 2 start at 101 .

In contrast to an EUV projection exposure apparatus 1 as described in figure 1 , refractive, diffractive and/or reflective optical elements 117, such as for example lens elements, mirrors, prisms, terminating plates, and the like, can be used for imaging or for illumination in the DUV projection exposure apparatus 101 on account of the greater wavelength of the DUV radiation 116, employed as used light, in the range from 100 nm to 300 nm, in particular of 193 nm. The projection exposure apparatus 101 in this case essentially comprises an illumination system 102, a reticle holder 108 for receiving and exactly positioning a reticle 107 provided with a structure, which determines the later structures on a wafer 113, a wafer holder 114 for holding, moving, and exactly positioning said wafer 113, and a projection lens 110, with a plurality of optical elements 117, which are held by way of mounts 118 in a lens housing 119 of the projection lens 110.

The illumination system 102 provides DUV radiation 116 required for the imaging of the reticle 107 on the wafer 113. A laser, a plasma source or the like can be used as the source of this radiation 116. The radiation 116 is shaped in the illumination system 102 by means of optical elements such that the DUV radiation 116 has the desired properties with regard to diameter, polarization, shape of the wavefront and the like when it is incident on the reticle 107.

Apart from the additional use of refractive optical elements 117, such as lens elements, prisms, terminating plates, the construction of the downstream projection optical unit 110 with the lens housing 119 does not differ in principle from the construction described in figure 1 and is therefore not described in further detail.

Figure 3 shows a connection, known from the prior art, between an inner first structural part 31 and an outer second structural part 35 of a component 30, with figure 3 illustrating a section through the component 30 in the region of the connection. The component 30 may be part of a projection exposure apparatus 1 , 101 elucidated in figure 1 and figure 2. In particular, the outer structural part 35 may be a part of a support structure, what is referred to as a force frame of a projection exposure apparatus; the inner structural part 31 may for example be part of an end stop for securing transport or else for operation. A connection geometry 36 of the outer structural part 35 has a recess 37, which is delimited on three sides at least partially by two faces formed in the y direction and one face, formed perpendicularly thereto, in the x direction and which is delimited on the fourth side, which is opposite the face formed in the x direction, by a slope 38. In this case, the face formed in the x direction is in the form of a first contact face 39 and one of the faces in the y direction is in the form of a second contact face 40 for positioning the first structural part 31 relative to the second structural part 35. The connection geometry 32 of the inner structural part 31 in the x direction has a contact face 33 corresponding to the contact face 39 of the outer structural part 35 and in the y direction has a second contact face 34 corresponding to the contact face 40 of the outer structural part 35. The contact face 34 of the inner structural part 31 in the y direction is in this case, in the embodiment illustrated in figure 3, approximately in the form of a contact line with an extent in the z direction, that is to say perpendicularly to the plane of the drawing, in order to avoid a double fit of the two faces 33, 34. Here, the contact face 33 defines the alignment of the two structural parts 31 , 35 in the y direction and in rotation about the z axis relative to one another and the contact face 34 defines the position in the x direction. The structural parts 31 , 35 are connected to one another in the y direction in a form fit by a wedge 41 , which is arranged between the slope 38 and a face 42 formed parallel to the contact face 33 of the inner connection geometry 32. By contrast, the structural parts 31 , 35 are connected to one another in the x direction merely in a frictional engagement by way of the force, brought about in the y direction by the wedge 41 , on the face 40 and by way of the friction arising between the wedge 41 and the face 42. This can lead to a movement of the inner structural part 31 with respect to the outer structural part 35 in the event of load being applied to the connection in the x direction, as illustrated in figure 3 by an arrow. The positioning of the two structural parts 31 , 35 relative to one another is set by way of the adaptation of one connection geometry or both connection geometries 32, 36, or the positions of the inner structural part 31 and the outer structural part 35 are set by inserting spacer elements, not illustrated in figure 3.

Figure 4 shows a connection according to the invention between an inner structural part 51 and an outer structural part 55 of a component 50, which in turn illustrates a section in the region of the connection of the two structural parts 51 , 55. The component 50 may be part of a projection exposure apparatus 1 , 101 elucidated in figure 1 and figure 2. A connection geometry 52 of the inner structural part 51 in turn comprises two contact faces 53, 54, which are at right angles to one another. A third face 62 is aligned at 45° relative to the two other contact faces 53, 54. In the example shown, the three faces 53, 54, 62 thus form the sides of an imaginary right-angled isosceles triangle, for manufacturing technology reasons the apex with the right angle having been removed and the side opposite this apex being at least partially offset. A connection geometry 56 of the outer structural part 55 has a recess 57, which has a trapezium-like shape in the lower region and is delimited on the opposite side by a slope 58. The opening angle of the trapezium-like recess 57, correspondingly to the two contact faces 53, 54 of the connection geometry 52 of the inner structural part 51 , is 90 degrees. The inner structural part 51 is connected to the outer structural part 55 in a form fit in all directions of the sectional plane (x-y plane) by a wedge 61 , which is arranged between the slope 58 and the third face 62 of the connection geometry 52. By way of example, figure 4 illustrates a force in the positive y direction on the inner structural part 51 in the form of an arrow and the resulting forces in the negative y direction, likewise in the form of an arrow. While the force in the positive y direction is taken up by the wedge 61 and the slope 58 through the form fit, the force in the negative y direction is distributed over the two contact faces 53, 54, which are formed at +/- 45° relative to the y axis in the embodiment illustrated in figure 4, of the connection geometry 52 of the inner structural part 51 and is taken up by the form fit between them. As shown in the figure, to set the position and alignment between the inner structural part 51 and the outer structural part 55, spacer elements 63 may be arranged between the faces 53, 54, 62 of the inner connection geometry 52 and the corresponding faces 59, 60 of the outer connection geometry 56 or of the wedge 61 . The wedge 61 pretensions the connection, with the result that the form fit is ensured even in the event of forces arising during operation or transport. Forces can also be produced by different coefficients of thermal expansion and thus different thermal expansions of the inner structural part 51 and outer structural part 55.

Figure 5 shows a further embodiment of a connection according to the invention between an inner structural part 71 and an outer structural part 75 of a component 70, with illustration of a section through the component 70 in the region of the connection. The component 70 may be part of a projection exposure apparatus 1 , 101 elucidated in figure 1 and figure 2.

The connection geometry 72 of the inner structural part 71 in principle has a form corresponding to the connection geometry 52 elucidated in figure 4. The first contact face 73, illustrated on the right in figure 5, of the inner connection geometry 72 is however larger than the second contact face 74 of the inner connection geometry 72. As already explained above, one of the contact faces 73, 74 is that contact face which determines the alignment of the structural parts relative to one another. In the embodiment illustrated in figure 5, this is the larger contact face 73, since the accuracy of the alignment and position of the inner structural part 51 relative to the outer structural part 55 depends on the size of the contact face 73.

Moreover, a large contact face has the advantage that the lever arm 86.1 between an engagement point 84.1 of a moment on the inner structural part 71 and the outermost contact point 85.1 on the contact face 73 can be maximized, as a result of which the loading on the contact face 73 is minimized. The smaller contact face 74, illustrated on the left in figure 5, of the inner connection geometry 72 comprises a decoupling means 87 and is decoupled from the inner connection geometry 72 thereby in such a way that a manufacturing-related angular error between the contact faces 73, 74 of the inner connection geometry 72 and the contact faces 79, 80 of the recess 77 in the outer connection geometry 76 is compensated. This makes it possible to ensure contact between the contact faces 73, 74, 79, 80 over their entire surface area. The face 82, which is directed toward the slope 78 of the outer connection geometry 76, of the inner connection geometry 72 is likewise decoupled from the connection geometry 72 for the same reasons. In this case, the decoupling means 88 is designed in such a way that the point of rotation of the decoupling means 88 has a minimum spacing from the decoupled face 73, 82. In particular, the decoupling means 88 may be designed in such a way that the point of rotation is in the contact face between the wedge 81 and the face 82.

To minimize the moments and thus the loading on the decoupling means 88, in the embodiment illustrated in figure 5 a decoupling element 83 is arranged between the wedge 81 and the face 82. The decoupling element 83 is prevented by a stop 89 from being pushed over the end of the face 82 in the event of mounting in a mounting direction, indicated in figure 5 by an arrow. When the connection is pretensioned, that is to say when the wedge 81 moves to the left, the decoupling element 83 does not transmit any forces to the inner structural part 71 in the x direction, since they are taken up by the stop 89, as a result of which only the forces required for the form fit and for a pretensioning force are transmitted in the y direction. The mode of action of the form fit is graphically illustrated in figure 5 by moments, lever arms and forces, which are depicted by way of example. At a moment engagement point 84.1 in the center of the inner connection geometry 72, a moment engages in the clockwise direction. The moment is transmitted to a contact point 85.1 on the contact face 73 by a lever arm 86.1 , this being depicted in figure 5 by a force illustrated as an arrow. Furthermore illustrated are another moment in the counterclockwise direction about the same engagement point 84.1 by means of the lever arm 86.2 and contact point 85.2 and a respective moment about an engagement point 84.2 and 84.3 by means of the lever arms 86.3 and 86.4 and contact points 85.3, all of which are taken up by a form fit, that is to say via a lever arm 86.1 , 86.2, 86.3 and a force perpendicular to a contact face 73, 74, 79, 80 or in the direction of the wedge 81 . The contact points 85.1 , 85.2, 85.3 are illustrated as rectangles in figure 5. Also illustrated is an inscribed circle 90 of the imaginary triangle already mentioned further above, which inscribed circle touches the contact faces 79, 80 and the face 82. The contact points 91.1 , 91 .2, 91 .3 of the inscribed circle 90 are illustrated as small squares in figure 5 and are the locations where it would be possible to take up the moment about the engagement point 84.1 only through friction, that is to say through frictional engagement.

Figure 6 shows a further embodiment of a connection of a component 70, the form fit between the two structural parts 71 , 75 being realized by a connection screwed join 92, 94, 96 of the inner connection geometry 72 of the inner structural part 71 to the connection geometry 76 of the outer structural part 75. The screwed joins 92, 94 are made in the contact faces 73, 74 and 79, 80, respectively, with the screwed joins 92, 94 comprising two screws 93, 95 in the embodiment shown in figure 6. The longitudinal axes of the screws 93, 95 are perpendicular to the contact faces 73, 74, 79, 80, with the result that the form fit is ensured by the screws 93, 95. As an alternative, a central screwed join 96 with a screw 97 can also connect the inner connection geometry 72 to the outer connection geometry 76 in a form fit, although this only applies to a screw 97 with finite flexural rigidity. As already elucidated in figure 5, figure 6 also illustrates a moment, lever arms 86.1 , 86.2 and forces by way of example that act on the inner connection geometry 72, to clarify the mode of action of the form fit. The embodiment elucidated in figure 6 has the advantage that the wedge 81 is no longer required and the production costs of the connection are advantageously minimized. The corners of the inner connection geometry 92 are subject to significant loading in particular in the event of repeated installation and removal for setting the position and alignment between the inner structural part 71 and the outer structural part 75, and therefore comprise a reinforcement 98 in the form of an insert or a specially hardened region. This is also conceivable for the embodiments illustrated in figure 4 and figure 5.

List of reference signs

1 Projection exposure apparatus

2 Illumination system

3 Radiation source

4 Illumination optical unit

5 Object field

6 Object plane

7 Reticle

8 Reticle holder

9 Reticle displacement drive

10 Projection optical unit

11 Image field

12 image plane

13 Wafer

14 Wafer holder

15 Wafer displacement drive

16 EUV radiation

17 Collector

18 Intermediate focal plane

19 Deflection mirror

20 Facet mirror

21 Facets

22 Facet mirror

23 Facets

30 Component

31 Inner structural part

32 Connection geometry of the inner structural part

33 First contact face of the inner structural part

34 Second contact face of the inner structural part

35 Outer structural part Connection geometry of the outer structural part Recess

Slope

First contact face of the outer structural part Second contact face of the outer structural part Wedge

Face

Component

Inner structural part

Connection geometry of the inner structural part First contact face of the inner structural part Second contact face of the inner structural part Outer structural part

Connection geometry of the outer structural part Recess

Slope

Face

Spacer elements

Component

Inner structural part

Connection geometry of the inner structural part First contact face of the inner structural part Second contact face of the inner structural part Outer structural element

Connection geometry of the outer structural part Recess

Slope

First contact face of the outer structural part 80 Second contact face of the outer structural part

81 Wedge

82 Face

83 Decoupling elements

84.1 -84.3 Moment engagement point

85.1 -85.3 Contact point

86.1 -86.4 Lever arm

87 Decoupling means

88 Decoupling means

89 Stop

90 Circle

91.1 -91.3 Points of friction

92 Screwed join, short contact face

93 Screw

94 Screwed join, long contact face

95 Screw

96 Screwed join, central screw

97 Screw

98 Corner reinforcement

101 Projection exposure apparatus

102 Illumination system

107 Reticle

108 Reticle holder

110 Projection optical unit

113 Wafer

114 Wafer holder

116 DUV radiation

117 Optical element

118 Mounts

119 Lens housing

M1 -M6 Mirrors

Claims

Patent claims

1 . A component (50, 70) for a projection exposure apparatus (1 , 101 ) for semiconductor lithography comprising at least two structural parts (51 , 55, 71 , 75) which are connected to one another, it being possible for the structural parts (51 , 55, 71 , 75) to be positioned relative to one another in at least one plane and the position and alignment being determined via two contact faces (53, 54, 73, 74), wherein the connection has a form-fitting design in the at least one plane.

2. The component (50, 70) as claimed in claim 1 , wherein the angle between the two contact faces (53, 54, 73, 74) is between 60° and 120°.

3. The component (50, 70) as claimed in claim 2, wherein the angle between the two contact faces (53, 54, 73, 74) amounts to 90°.

4. The component (50, 70) as claimed in one of claims 1 to 3, wherein a spacer element (63) is arranged on at least one of the contact faces (53, 54, 73, 74) between the structural parts (51 , 55, 71 , 75).

5. The component (50, 70) as claimed in claim 4, wherein the position and the alignment of the two structural parts (51 , 55, 71 , 75) relative to one another in the plane can be set by the at least one spacer element (63).

6. The component (50, 70) as claimed in claim 5, wherein the connection is designed in such a way that the structural parts (51 , 55, 71 , 75) are aligned relative to one another with a tolerance of less than 67 mrad and less than 30 pm.

7. The component (70) as claimed in one of the preceding claims, wherein in the case of one of the two structural parts (71 , 75), the two contact faces (73, 74) have different lengths.

8. The component (50, 70) as claimed in one of the preceding claims, wherein three contact faces (53, 54, 62, 73, 74, 82) are formed between the two structural parts (51 , 55, 71 , 75).

9. The component (50, 70) as claimed in one of the preceding claims, wherein a wedge (61 , 81 ) is arranged between the structural parts (51 , 55, 71 , 75).

10. The component (70) as claimed in one of the preceding claims, wherein the structural parts (71 , 75) are connected to one another by screws (93, 95, 97).

11 . The component (70) as claimed in one of the preceding claims, wherein at least one contact face (73, 74) of one of the structural parts (71 , 75) has a decoupling means (87, 88).

12. The component (70) as claimed in one of the preceding claims, wherein at least two contact faces (74, 82) of one of the structural parts (71 , 75) have a decoupling means (87, 88).

13. A projection exposure apparatus (1 , 101 ) for semiconductor lithography, comprising a component (50, 70) as claimed in one of the preceding claims.