Optical element for beam guidance of imaging light in projection lithography

Abstract

An optical element (M) for guiding a beam of imaging light in projection lithography. The optical element (M) comprises a body (18) and at least one optical surface (19) carried by the body (18). At least one compensating weight element (20, 23) attached to the body (18) serves for weight compensation of the figure deformation of the optical surface (19) caused by gravity. This results in an optical element with small figure deformation in the use position.

Description

[0001] The contents of German patent applications DE 10 2017 212 869.0 and DE 10 2018 200 152.9 are incorporated herein by reference.

[0002] The present invention relates to an optical element for beam guiding of imaging light in projection lithography. Furthermore, the present invention relates to a method for producing such an adapted optical element, an imaging optical unit comprising at least one such optical element, an optical system comprising such an imaging optical unit, a projection exposure apparatus comprising such an optical system, a method for producing a microstructured or nanostructured component by means of such a projection exposure apparatus, and a microstructured or nanostructured component produced by this method.

[0003] Such an optical element has been disclosed in DE 10 2013 214 989 A1. An imaging optical unit of the type described at the beginning has been disclosed in WO 2016 / 188934 A1 and WO 2016 / 166080 A1.

[0004] An object of the present invention is to provide an optical element having an ideally small pattern distortion in the use position.

[0005] According to the present invention, this object is achieved by an optical element comprising the features described in claim 1.

[0006] According to the present invention, it has been recognized that the requirements for pattern accuracy in projection lithography, i.e., the requirements for the correspondence between the shape of the optical surfaces of the optical element and the beam guiding of the imaging light, are so high that gravity (which acts directly or indirectly on the optical surfaces), in particular the exact magnitude of the gravity at the use position of the projection exposure apparatus (which is a component of the optical element under consideration), plays a major role. It has thus been recognized that it is necessary to take into account the pattern distortion of the optical surfaces caused by gravity, which depends in particular on the use position. At least one compensating weight element of the optical element ensures appropriate weight compensation, and it is thus possible to compensate for the influence on the optical surfaces caused by gravity, in particular the force differences caused by gravity and its influence on the pattern between, on the one hand, the mirror production position and, on the other hand, the mirror use position. Another example of a pattern distortion caused by gravity (which can be compensated by means of at least one compensating weight) is the deformation of the optical surface caused by the force transmission caused by gravity between the body of the optical element and the bearing of the optical element (for example in a holding frame).

[0007] The construction according to claim 2 has been found to be particularly suitable. The compensating weight element can be attached to the rear side of the mirror without disturbing the optical surface. As an alternative or in addition thereto, at least one weight compensating element can be attached to the edge of the optical element, i.e., for example, to the edge of the mirror. If the optical element is not implemented as a mirror but as, for example, a lens element, such attachment of at least one compensating weight element at the edge of the optical element can also be implemented. The attachment of at least one compensating weight element to the edge of the optical element can take place at the edge of the body of the optical element, for example, at the side wall of the body. The attachment of at least one compensating weight element to the optical element, in particular to the edge of the optical element, can take place with the assistance of a magnetic fixture. At least one magnet for this fixation can be part of the optical element and / or part of the corresponding compensating weight element.

[0008] The attachment of at least one compensating weight element in the region of the centroid axis according to claim 3 ensures that the effect of the compensating weight element attached in this way is as symmetric as possible. Then, in many cases, attaching just one compensating weight element is sufficient. In principle, it is also possible to attach a plurality of compensating weight elements to the body in the region of the centroid axis of the optical element. For example, attaching a plurality of compensating weight elements in the region of the centroid axis is applicable in cases where the centroid axis itself is not accessible for attaching the compensating weight element, for example, if there is a channel opening in the body of the optical element at that location. In such a case, one compensating weight element or a plurality of compensating weight elements can be arranged in the region of the edge of such a channel opening such that, in a good approximation, at least one compensating weight element has a weight influence on the centroid axis. As an alternative or in addition to the above-described configuration variant, at least one compensating weight element can be attached radially between the centroid axis of the optical element and the outer edge region of the optical element. It is also possible to have at least two such radially arranged compensating weight elements, in particular arranged on the same radius radially between the centroid axis and the outer edge region of the optical element.

[0009] In the case of the construction according to claim 4, the additional degree of freedom deviating from rotational symmetry can be used for weight compensation of the figure deformation of the optical surface caused by gravity. Such compensating weight elements attached on the circumferential side can also be used in the case where there are no compensating weight elements in the region of the centroid axis of the optical element. A plurality of compensating weight elements can also be arranged between two bearing locations adjacent to each other in the circumferential direction.

[0010] The construction according to claim 5 has been found to be particularly advantageous.

[0011] The attachment variants according to claims 6 to 9 (which can alternatively be used or used in combination with each other) have proven to be particularly suitable for a fixed and uncomplicated connection of the respective compensating weight element to the body. For example, such a connection can be obtained by screwing or clamping the compensating weight element to the body. A force-fitting connection and / or a contribution to a force-fitting connection of the compensating weight element at the body is also possible.

[0012] The embodiment of the compensating weight element according to claim 7 contributes to introducing a moment from the compensating weight element into the body, which can be used for a targeted influence on the shape of the optical surface of the optical element.

[0013] The adjustable connecting rod according to claim 8 contributes to enabling an adjustable specification of the absolute value and / or the direction of the moment introduction via the moment compensating weight element.

[0014] The compensating weight element according to claim 9 can be connected to the body by means of an additional element, where the additional element can be an interface plate. This connection of the compensating weight element to the body via the additional element can be achieved in an integrally joined manner (for example by means of at least one adhesive layer) and / or in a magnetic manner.

[0015] The advantages of the production method for the post-optical element according to claim 10 correspond to the explanations already made above with reference to the optical element. The attachment of at least one compensating weight element can be carried out before or after moving the blank to the use position of the device for projection lithography. The adjustment steps for the optical element within the respective assembly can still follow the compensating weight attachment step. The optical element can be a component of the projection optical unit and / or a component of the illumination optical unit of the projection exposure device.

[0016] The invention also encompasses a set of various compensating weight elements, where the selected compensating weight elements can be attached to the body of the optical element for weight compensation purposes. The compensating weight elements in this set of compensating weight elements can be annular or disc-shaped. The compensating weight elements in the set can have different ring or disc diameters. The compensating weight elements in the set can have the same ring or disc thickness. If the compensating weight element is annular or disc-shaped and can be attached to the body of the optical element in a centered manner with respect to the axis of rotational symmetry, then if the compensating weight elements only differ in terms of diameter and not in terms of thickness, the center of mass of the compensating weight elements attached to the body accordingly is always located at the same position relative to the body, independent of the diameter of the compensating weight element. Then, the moment contributions that occur in an uncontrolled manner when changing between compensating weight elements with different diameters are avoided.

[0017] The compensating weight elements in the set can have a uniform density, such that the mass of the compensating weight element only depends on its volume.

[0018] The advantages of the imaging optical unit according to claim 11, the optical system according to claim 12, the projection exposure apparatus according to claim 13, the method for producing a microstructured or nanostructured component according to claim 14, and the microstructured or nanostructured component according to claim 15 correspond to the advantages already explained above with reference to the optical element according to the invention and the method for producing a post-optical element according to the invention. In particular, a projection exposure apparatus can be used to produce semiconductor components, such as memory chips.

[0019] The light source can be an EUV light source. Alternatively, a DUV light source, i.e., a light source with a wavelength of 193 nm, for example, can also be used.

[0020] Exemplary embodiments of the invention will be explained in more detail below with reference to the figures. In the figures:

[0021] Figure 1 Schematically shows a projection exposure apparatus for EUV microlithography;

[0022] Figure 2 Shows a meridional section of an embodiment of an imaging optical unit, which can be used as a projection lens in the projection exposure apparatus in Figure 1 in which the imaging beam paths of the chief ray and the upper and lower coma rays for three selected field points are depicted;

[0023] Figure 3 Shows Figure 2 the edge profile of the mirror surface of the mirror of the imaging optical unit in

[0024] Figure 4 Shows Figure 2 a perspective view of the body of the mirror of the imaging optical unit in

[0025] Figure 5 Similar to Figure 3 a schematic diagram shows another embodiment of the configuration of the compensating weight element, in which in addition to Figure 3 the compensating weight element of

[0026] Figure 6 a rear side view of the body of the mirror with an additional configuration of the compensating weight element is shown;

[0027] Figure 7 Similar to Figure 6 a schematic diagram shows the configuration of the compensating weight element, compared withFigure 6 , having a connecting rod for introducing a moment in each case;

[0028] Figure 8 similar to Figure 7 shown in the view of Figure 7 one of the compensating weight elements in the style of , which on the one hand illustrates the mobility of the compensating weight element along the connecting rod and on the other hand illustrates the pivotability of the connecting rod;

[0029] Figure 9 Showing a side view of the compensating weight element according to Figure 8 , as seen from the viewing direction IX in Figure 8 ;

[0030] Figure 10 and Figure 11 similar to Figure 8 and Figure 9 shown in a schematic diagram of another embodiment of the compensating weight element having a connecting rod implemented as a disk;

[0031] Figure 12 Showing a perspective view of another embodiment of the body of the mirror, which is another example of an optical element having a compensating weight element attached to the edge of the optical element;

[0032] Figure 13 Showing, in comparison with Figure 12 , an enlarged axial cross-section of the body shown in Figure 12 in the region of the interface unit for attaching / fixing the compensating weight element;

[0033] Figure 14 Showing a compensating weight element attachable to the edge, which can be attached to the Figure 13 interface unit in

[0034] Figure 15 and Figure 16 shown in a schematic diagram similar to Figure 13 and Figure 14 of another embodiment of the compensating weight element attached to another embodiment of the interface unit of the body;

[0035] Figure 17 Showing a plan view of the compensating weight element according to Figure 16 , as seen from the viewing direction XVII in Figure 16 ;

[0036] Figure 18 shown in a schematic diagram similar to Figure 16 of another embodiment of the compensating weight element.

[0037] The microlithographic projection exposure apparatus 1 has a light source 2 for illumination light or imaging light 3. The light source 2 is an EUV light source which generates light in a wavelength range between, for example, 5 nm and 30 nm, in particular between 5 nm and 15 nm. The light source 2 can be a plasma-based light source (laser-produced plasma (LPP)), a gas-discharge-produced plasma (GDP)) or a synchrotron-based light source, such as a free electron laser (FEL). In particular, the light source 2 can be a light source with a wavelength of 13.5 nm or a light source with a wavelength of 6.9 nm. Other EUV wavelengths are also possible. Generally speaking, for the illumination light 3 guided in the projection exposure apparatus 1, even any wavelength is possible, such as visible light wavelengths or other wavelengths that can be used in microlithography (e.g., DUV, deep ultraviolet light) and for which suitable laser light sources and / or LED light sources can be provided (e.g., 365 nm, 248 nm, 193 nm, 157 nm, 129 nm, 109 nm). Figure 1 The beam path of the illumination light 3 is shown in a very schematic way.

[0038] The illumination optical unit 6 is used to guide the illumination light 3 from the light source 2 to the object field 4 in the object plane 5. Using a projection optical unit or imaging optical unit 7, the object field 4 is imaged onto the image field 8 in the image plane 9 at a predetermined reduction ratio.

[0039] For the purpose of facilitating the description of various embodiments of the projection exposure apparatus 1 and the projection optical unit 7, a Cartesian xyz coordinate system is shown in the figure, from which the corresponding positional relationships of the components shown in the figure can be clearly seen. In Figure 1 it, the x direction is perpendicular to the drawing plane and extends into the drawing plane. The y direction is to the left, and the z direction is upwards.

[0040] In the projection optical unit 7, the object field 4 and the image field 8 have curved or arcuate embodiments, in particular embodiments shaped like a partial annulus. The radius of curvature of this field curvature can be 81 mm on the image side. The corresponding annular field radius of the image field is defined in WO 2009 / 053023 A2. The basic form of the boundary contour of the object field 4 or the image field 8 has a corresponding curvature. Alternatively, it is possible to implement the object field 4 and the image field 8 as rectangles. The object field 4 and the image field 8 have an x / y aspect ratio greater than 1. Thus, the object field 4 has a longer object field size in the x direction and a shorter object field size in the y direction. These object field sizes extend along the field coordinates x and y.

[0041] In an exemplary embodiment of the projection optical unit 7, there is an x size of the image field of 26 mm and a y size of the image field 8 of 1.2 mm.

[0042] Thus, the object field 4 is spanned by a first Cartesian object field coordinate x and a second Cartesian object field coordinate y. A third Cartesian coordinate z perpendicular to these two object field coordinates x and y is also referred to below as the normal coordinate.

[0043] Figure 2 The exemplary embodiments depicted in Figure 2 and Figure 3 can be used for the projection optical unit 7. The optical design of the projection optical unit 7 shown in

[0044] In an embodiment of the projection optical unit 7 according to Figure 2 the image plane 9 is configured to be parallel to the object plane 5. In this case, a part of the reflection mask 10 (also referred to as the mask master) that coincides with the object field 4 is imaged. The mask master 10 is carried by a mask master holder 10a. The mask master holder 10a is displaced by a mask master displacement drive 10b.

[0045] The imaging by means of the projection optical unit 7 is effected on the surface of a substrate 11 in the form of a wafer, where the substrate 11 is carried by a substrate holder 12. The substrate holder 12 is displaced by a wafer or substrate displacement drive 12a.

[0046] Figure 1 The ray bundle 13 of the illumination light 3 entering the projection optical unit between the mask master 10 and the projection optical unit 7 and the ray bundle 14 of the illumination light 3 emerging from the projection optical unit 7 between the projection optical unit 7 and the substrate 11 are shown schematically. The image field side numerical aperture (NA) of the projection optical unit 7 is not reproduced to scale in Figure 1 The projection exposure apparatus 1 is of the scanner type. During the operation of the projection exposure apparatus 1, the mask 10 and the substrate 11 are scanned in the y direction. A stepwise projection exposure apparatus 1 is also possible, where stepwise displacements of the mask master 10 and the substrate 11 in the y direction are effected between the individual exposures of the substrate 11. By appropriate actuation of the displacement drives 10b and 12a, these displacements will be carried out synchronously with one another.

[0047]

[0048] Figure 2 shows the optical design of the projection optical unit 7. Figure 2 shows the meridional section of the projection optical unit 7, i.e., the beam path of the imaging light 3 in the yz plane. The projection optical unit 7 according to Figure 2 has a total of ten mirrors, which are consecutively numbered from M1 to M10 in the order of the beam path of the individual ray 15 starting from the object field 4.

[0049] Figure 2 illustrates in each case starting from in​Figure 2 The beam paths of three individual rays 15 emitted from three object field points spaced apart from each other in the y-direction in Figure 2 . The main ray 16 is shown (i.e., the individual ray 15 passing through the center of the pupil in the pupil plane of the projection optical unit 7), and in each case the upper coma ray and the lower coma ray for these two object field points. Starting from the object field 4, the main ray 16 includes an angle CRA of 5.2° with respect to the normal of the object surface 5.

[0050] The object surface 5 is parallel to the image surface 9.

[0051] Figure 2 Cross-sections of the calculated reflective surfaces of the mirrors M1 to M10 are shown. A part of these calculated reflective surfaces is used. Only this actually used area of the reflective surface, plus the overhang, actually exists in the real mirrors M1 to M10.

[0052] Figure 3 Shows the actually used area of the reflective surfaces of the mirrors M1 to M10. The mirror M10 has a channel opening 17 for the imaging light 3 to pass through, where the imaging light 3 is reflected from the penultimate mirror M8 towards the last but one mirror M9. The mirror M10 is used reflectively around the channel opening 17. None of the other mirrors M1 to M9 has a channel opening, and these mirrors are used reflectively in a continuous area without gaps.

[0053] The mirrors M1 to M10 are implemented as free-form surfaces, which cannot be described by a rotationally symmetric function. Other embodiments of the projection optical unit 7 are also possible, in which at least one of the mirrors M1 to M10 is implemented as a rotationally symmetric aspherical surface. DE 10 2010 029 050 A1 discloses an aspherical equation for such a rotationally symmetric aspherical surface. It is also possible for all the mirrors M1 to M10 to be implemented as such aspherical surfaces.

[0054] The free-form surface can be described by the following free-form surface equation (Equation 1):

[0055]

[0056] The following parameters apply to this Equation (1):

[0057] Z is the sag of the free-form surface at the point x, y, where x 2 +y 2 =r 2 . Here, r is the distance from the reference axis (x = 0; y = 0) of the free-form equation.

[0058] In the free-form surface equation (1), C 1 , C2 , C 3 …… represents the coefficients of a free - form surface series expansion with powers of x and y.

[0059] In the case of the conical base region, c x , c y are constants corresponding to the vertex curvature of the respective aspheres. Thus, c x = 1 / R x and c y = 1 / R y . Here, k x and k y each correspond to the conical constant of the respective aspheres. Thus, Equation (1) describes a bi - conical free - form surface.

[0060] Alternative possible free - form surfaces can be generated from a rotationally symmetric reference surface. Such a free - form surface of the reflective surface of a mirror of a projection optical unit for a microlithography projection exposure apparatus has been disclosed in US 2007 - 0058269A1.

[0061] Alternatively, a free - form surface can also be described with the assistance of a two - dimensional spline surface. Examples in this regard are Bezier curves or non - uniform rational B - splines (NURBS). For example, a two - dimensional spline surface can be described by a grid of points in the xy - plane and associated z - values, or by these points and their associated slopes. Depending on the respective type of the spline surface, a complete surface is obtained by interpolation between the grid points using, for example, polynomials or functions having specific properties in terms of their continuity and differentiability. An example thereof is an analytic function.

[0062] The reflective surfaces used for mirrors M1 to M10 are carried by a body.

[0063] The body 18 can be made of glass, ceramic, or glass - ceramic. The material of the body 18 can be matched such that its coefficient of thermal expansion at the selected operating temperature of the mirror M is very close to a value of 0 and ideally exactly 0. is an example of such a material.

[0064] Figure 4 A perspective view of such a body 18 is shown by way of example. Here, the viewing direction is from the rear side of the mirror, i.e., from the side facing away from the reflective surface used for reflection. The optical surface for reflection is denoted by the symbol 19 in Figure 4 .

[0065] Figure 4 The mirror M shown in

[0066] In accordance with Figure 4In an embodiment of the mirror M, a compensating weight element 20 is attached to the body 18. This compensating weight element is used to compensate for the weight of the figure deformation of the optical surface caused by gravity. Thus, the compensating weight 20 is used to compensate for the figure error of the optical surface 19, which is due to the difference in gravity on the mirror M at the production location where the mirror M is produced and the gravity on the mirror M at the use location, where a projection exposure apparatus (of which the mirror M is a part) is used to produce semiconductor components.

[0067] The compensating weight element 20 is attached to the rear side 21 of the body 18. The compensating weight element 20 is attached to the body 18 in the region of the centroid axis SP of the mirror M, as Figure 4 schematically shown.

[0068] The compensating weight element 20 is connected to the body 18 in an interlocking manner by an undercut catch (which is not shown in more detail). For this purpose, the body 18 has a groove with an undercut, and a part of the compensating weight element 20 complementary to the groove is locked or clamped in the groove, engaging after the undercut. Alternatively, the compensating weight element 20 can also be connected to the body 18 in a monolithic engagement manner and / or in a threaded connection manner.

[0069] In any other embodiment not shown here, the compensating weight element 20 can also be connected to the body 18 by an inserted interface plate. The interface plate can first be connected to the compensating weight element 20 and then connected to the body 18 in an interlocking or monolithic engagement manner, as explained above in connection with the connection of the compensating weight element 20 to the body 18.

[0070] The body 18 has a plurality of bearing sites 22. In the exemplary embodiment shown, these are three bearing sites 22. Through these bearing sites 22, the body 18 is carried in a bearing seat of a holding frame (not shown here) of the mirror M.

[0071] When producing Figure 4 the adjusted optical element in the form of the mirror M, the following procedure is adopted:

[0072] First, a blank of the mirror M is produced while taking into account the negative form tolerance at the production location. Here, the preformed optical surface 19 is such that it has the desired shape only under the action of the force of at least one compensating weight element 20 of the style of compensating weight elements. Subsequently, the blank prefabricated in this way is moved to the use location of the projection exposure apparatus. There, taking into account the acceleration due to gravity at the use location, at least one compensating weight element 20 of the style of compensating weight elements is attached to the body 18 of the mirror M to compensate for the weight of the shape deformation of the optical surface 19 caused by gravity. If the acceleration due to gravity at the use location is well-known enough, it is possible to exchange the last two steps of "moving the blank to the use location" and "attaching at least one compensating weight element". Subsequently, the mirror is adjusted at the mirror use location in the projection exposure apparatus.

[0073] In a variant of the mirror production method, the original compensating weight element can be immediately attached to the body of the optical element during the manufacture of the blank of the optical element, and the original compensating weight element overcompensates for the expected effect of the shape deformation of the optical surface caused by gravity. To manufacture the adjusted optical element, by removing a part of the compensating weight element (e.g., by ablation), the compensating weight element can be made lighter in terms of its weight effect on the optical surface until the desired weight compensation effect is achieved to achieve the desired shape deformation compensation. This variant of the production method avoids subsequently attaching a discharge element to the finished optical surface, which itself may cause unwanted shape deformation.

[0074] In an embodiment where the mirror M is an asymmetric mirror made of ceramic with a mass of 500 kg, a diameter of 90 cm, and a thickness of 20 cm, the theoretically fitted deformation caused by a 0.1% change in the acceleration due to gravity is approximately 350 pm. Due to the above weight compensation by the compensating weight element, this effect can be reduced to approximately 13 pm. Therefore, after compensation, there remains less than 4% of the original shape deformation.

[0075] Generally speaking, it is possible to achieve compensation for the shape deformation caused by gravity to a value less than 10% of the original shape deformation caused by gravity.

[0076] Figure 5 Another embodiment of an optical element showing an example of using the mirror M, which has a weight compensation shape deformation of the optical surface caused by gravity. The components and functional parts that have been explained previously in the context (especially in the context of Figures 1 to 4 have the same element symbols and will not be discussed in detail again. Figure 4 of the context)

[0077] In addition to the central compensating weight element 20 in the region of the centroid axis SP, according toFigure 5 The body 18 of the mirror M also has compensating weight elements 23. One of these additional compensating weight elements 23 is in each case arranged between two bearing sites 22 which are adjacent to one another in the circumferential direction around the centroid axis SP. With the aid of such an embodiment having a plurality of compensating weight elements 20, 23, an additional degree of freedom arises in the weight compensation for gravity-induced figure deformations.

[0078] In a further embodiment not shown corresponding to the arrangement of the compensating weight elements Figure 5 shown, the central compensating weight element 20 in the region of the centroid axis SP is missing.

[0079] Figure 6 A rear view of the mirror M is shown, which has a further configuration variant of the compensating weight elements.

[0080] In the arrangement according to Figure 6 there is a central arrangement of compensating weight elements 20 in the style of the embodiment having Figure 4 and Figure 5 . In the embodiment according to Figure 6 there are in each case two compensating weight elements 23 between two bearing sites 22 which are adjacent to one another in the circumferential direction around the centroid axis SP. In addition, further compensating weight elements 26 are present radially between the centroid axis SP of the mirror M and the outer edge region 25 and have a distance A or radius value which is half that of the outer compensating weight elements 23 arranged circumferentially between the bearing sites 22, relative to the central compensating weight element 20. The distance between the central compensating weight element 20 and the outer compensating weight elements 23 arranged between adjacent bearing sites 22 is denoted by Figure 6 B in Figure 6 . Thus, for the embodiment shown in

[0081] the following applies: B = 2A. Other ratios B / A in the range between 1.1 and 10 are also possible. The radial compensating weight elements 26 can all have the same distance A from the central compensating weight element 20. Alternatively, it is possible to provide different distances A between the radial compensating weight elements 26 and the central compensating weight element 20 1 , A 2 ......

[0082] Overall, in addition to the central compensating weight element 20, there are also three radial compensating weight elements 26 and six circumferential compensating weight elements 23 in the arrangement of the compensating weight elements shown in Figure 6 ; i.e. a total of 10 compensating weight elements. For example, depending on the requirements for the compensation of figure deformations, the number of compensating weight elements can be in the range between 5 and 25.

[0083] Although in principle having the same configuration of compensating weight elements as in Figure 6 , Figure 7 shows a design of a compensating weight element 27 as an alternative to the embodiment shown in Figures 4 to 6 , which is designed as a moment compensating weight element. Thus, overall, Figure 7 there are ten such moment compensating weight elements 27 in the positions of the compensating weight elements 20, 23, and 26 of the embodiment shown in Figure 6 .

[0084] Figure 8 And Figure 9 illustrates the design of a first embodiment of the moment compensating weight element 27. These each have a compensating weight 28, which is connected to the body 18 via a connecting rod 29 and an additional element 30 designed as an interface.

[0085] When the mirror M is oriented such that its rear side points upward, the direction of the gravity G of the compensating weight 28 of the moment compensating weight element 27 extends from the centroid of the compensating weight 28 at a distance from the connection region (where the connecting rod 29 is connected to the body 18 thereby), i.e., at a distance from the additional element (interface) 30. This results in a moment, where the moment compensating weight element 27 introduces this moment into the body 18 of the mirror M. The introduction of the moment can be used for a targeted change in the shape of the mirror relative to the optical surface 19 (which is used for reflection purposes).

[0086] In the moment compensating weight element 27, it is possible to predetermine the magnitude and direction of the introduced moment in an adjustable manner. To predetermine the magnitude of the introduced moment, the compensating weight 28 can be moved relative to the latter along the connecting rod 29, as indicated by the double arrow in the longitudinal direction of the connecting rod 29 in Figure 8 .

[0087] The effective length of the connecting rod 29 and thus the absolute value of the introduced moment are set by the displacement of the compensating weight 28 along the connecting rod 29. This adjustment of the compensating weight 28 along the connecting rod 29 can be carried out continuously. For example, the compensating weight 28 can be magnetically fixed to the connecting rod 29.

[0088] The direction of the moment introduced into the body 18 by the moment compensating weight element 27 can be predetermined by setting the pivot of the connecting rod 29 about the pivot axis SA, as indicated by another double arrow in Figure 8 . Here, the additional element 30 can be implemented by a pivot bearing to the body 18, which can be fixed at a predetermined pivot position of the connecting rod 29 relative to the body 18 such that the connecting rod 29 is fixed at this pivot position.

[0089] Hereinafter, based onFigure 10 and Figure 11 describes another embodiment of such a moment compensation weight element 31. Components and functions corresponding to those components and functions that have been explained above with reference to Figures 1 to 9 (especially with reference to Figures 7 to 9 ) have the same element symbols and will not be discussed in detail again.

[0090] Instead of the elongated connecting rod 29 in the embodiment such as Figures 7 to 9 , the moment compensation weight element 31 has a disc-shaped connecting rod 32. The central region 33 of the connecting rod 32 is connected to the body 18 via an additional element (interface) 30. The compensation weight 28 can be displaced in two dimensions on the upper side of the connecting rod 32 facing away from the additional element 30, as shown by the crossed double arrows in the region of the compensation weight 28 in Figure 10 . By this displacement with two translational degrees of freedom, it is possible to predetermine in an adjustable manner the absolute value and the introduction direction of the moment of the moment compensation weight element 31. In this embodiment, although the pivotability or rotatability of the connecting rod 32 is possible in principle, it is not necessary.

[0091] Figure 12 shows another embodiment of the body 18 of the mirror M, which can be used in the projection exposure apparatus 1, replacing the mirror M shown in Figure 4 . Components and functions corresponding to those components and functions that have been explained above with reference to Figures 1 to 11 have the same element symbols and will not be discussed in detail again.

[0092] According to Figure 12 , the body 18 of the mirror M has a plurality of compensation weight elements 36, three in total in the embodiment shown, which are each attached to the body 18 on the edge side (i.e., on the side wall 35 of the body 18) via an interface unit 37. One of the three compensation weight elements 36 is covered by the body 18 and is therefore shown in dashed lines in Figure 12 . Figure 12 The three compensation weight elements 36 of the embodiment shown can be arranged around the body 18 and are arranged at equal intervals in the circumferential direction. Depending on the embodiment, different numbers of compensation weight elements 36 can also be arranged on the edge of the body 18. Here, the number of compensation weight elements 36 can be, for example, between 1 and 12.

[0093] Figure 13 shows details of one of the interface units 37, and Figure 14 shows the axial section of the compensation weight element 36 before being attached to the interface unit 37.

[0094] The interface unit 37 has a pin 38, the substrate part 38a of which is connected to the interface lateral part 39 of the body 18. In Figure 13In the illustrated embodiment, the substrate portion 38a of the pin 38 is connected to the body 18 in a monolithic bonding manner through an adhesive layer.

[0095] The pin 38 represents a holding member for compensating the weight element 36.

[0096] The pin 38 carries at least one magnet 40. Here, as shown, again, in the Figure 13 axial cross-section, this can be a magnetic ring, which is inserted onto the pin 38 until it reaches the support on the substrate portion 38a. The diameter of the substrate portion 38a can have the same size as the outer diameter of the magnetic ring. Additionally, the magnet 40 can again be connected to the pin 38 in a monolithic bonding manner and / or by press-fitting.

[0097] In the circumferential direction around the sidewall portion 39 of the interface, at least one release notch 41 is provided in the sidewall 35 of the body 18, where the release notch can be a release groove, particularly a release annular groove. The release notch 41 is used to prevent surface deformation caused by unwanted tension of the optical element M.

[0098] The compensating weight element 36 is implemented as a ring, which is inserted onto the free end of the pin 38 through its annular opening 42. To simplify this insertion process, the free end of the pin 38 can be tapered, as Figure 13 shown. The compensating weight element 36 is made of a magnetic material, such as

[0099] The compensating weight element 36 has a thickness D and a diameter DM.

[0100] The compensating weight element 36 can be a component of a set of various compensating weight elements. The compensating weight elements in this set can be different in terms of the diameter DM, but all have the same thickness D. The compensating weight elements in this set all have the same uniform density.

[0101] Figure 15 And 16 Similar to Figure 13 And Figure 14 Another embodiment of the interface unit 44 and the compensating weight element 43 is shown in a schematic diagram. The components and functions that have been explained previously with reference to Figures 1 to 14 (particularly with reference to Figures 12 to 14 ) have the same element symbols and will not be discussed in detail again.

[0102] The compensating weight element 43 carries a magnet 45, and the magnet 45 interacts with the corresponding component (i.e., the substrate portion 38a) of the interface unit 44 to fix the compensating weight element 43 to the interface unit 44. In the case of the interface unit 44, the substrate portion 38a is made of a magnetic material, which is

[0103] The magnet 45 of the compensating weight element 43 can be a magnet portion introduced into the compensating weight element 43, and the compensating weight element 43 is again implemented as annular. The magnet 45 can be adhesively joined to another compensating weight element 43 and / or connected to another compensating weight element 43 by press-fitting.

[0104] Figure 17 Show a plan view of the compensating weight element 43 as viewed from the viewing direction XVII in Figure 16 . The illustrated embodiment of the compensating weight element 43 has three magnets 45, which are equidistantly arranged in the circumferential direction around the annular body. This provides a reliable magnetic connection between the compensating weight element 43 and the substrate portion 38a of the interface unit 44, which has multiple rotational symmetries in terms of force introduction.

[0105] Like the other compensating weight elements described above, the compensating weight element 43 can also be a component of a set of different compensating weight elements. Again, the compensating weight elements in this set only differ in their diameters. The axial extent of the magnet 45 is as large as the axial extent (i.e., thickness) of the annular body of the compensating weight element 43.

[0106] In a schematic diagram similar to Figure 16 , Figure 18 shows another embodiment of the compensating weight element 46, which can be used, for example, instead of the compensating weight element 43. Components and functions corresponding to those components and functions that have been explained above with reference to Figures 1 to 17 (especially with reference to Figure 16 ) are denoted by the same reference numerals and will not be discussed in detail again.

[0107] In the compensating weight element 46, the magnet 45 has a two-part embodiment with magnetic parts 45a, 45b. The two magnetic parts 45a, 45b are arranged on both sides of the body of the compensating weight element 46. The magnetic parts 45a, 45b are arranged mirror-symmetrically with respect to the middle annular plane 47 of the body of the compensating weight element 46. The annular axis 48 is perpendicular to the middle annular plane 47. The intersection point between the annular axis 48 and the middle annular plane 47 is simultaneously the center of mass SP of the compensating weight element 46.

[0108] In Figure 16 and Figure 18 the shown configuration variants of the magnet 45, the central position of the center of mass SP remains unchanged, independent of the diameters of the corresponding compensating weight elements 43, 46. In particular, the relative position of the center of mass SP with respect to the adjacent surface of the interface unit 44 facing the corresponding compensating weight elements 43, 46 is maintained, independent of the compensating weight element diameter.

[0109] The body 18 of the optical element (i.e., for example, the body of the mirror M) can be made of manufactured.

[0110] For manufacturing a microstructured or nanostructured component, the projection exposure apparatus 1 uses the following: First, a reflective mask 10 or a mask blank and a substrate or a wafer 11 are provided. Then, with the assistance of the projection exposure apparatus 1, the structure on the mask blank 10 is projected onto the photosensitive layer of the wafer 11. Then, the microstructured or nanostructured component is produced by developing the photosensitive layer, thereby producing a microstructured component.

Claims

1. An optical element (M; M1 to M10) for guiding a beam of imaging light (3) in projection lithography, comprising a body (18) and at least one optical surface (19) carried by the body (18), characterized in that at least one compensating weight element (20; 23; 26; 27; 31; 36; 43), which is attached to the body (18) for weight compensation of a figure deformation of the optical surface (19) caused by gravity; and the compensating weight (28) of the compensating weight element (27; 31) is connected to the body (18) by a connecting rod (29; 32) such that the direction of gravity (G) starting from its center of mass extends at a distance from the connection region (30), and the connecting rod (29; 32) is connected to the body (18) via this connection region.

2. The optical element according to claim 1, characterized in that the optical element (M; M1 to M10) is implemented as a mirror, wherein the at least one compensating weight element (20; 23; 26; 27; 31; 36; 43) is attached to the body (18) at the rear side (21) of the mirror facing away from the optical surface (19) and / or at the edge of the optical element.

3. The optical element according to claim 1 or 2, characterized in that at least one compensating weight element (20) is attached to the body (18) in the region of the centroid axis (SP) of the optical element (M; M1 to M10).

4. The optical element according to any one of claims 1 to 3, characterized in that the body (18) is carried in a bearing seat of a holding frame of the optical element (M; M1 to M10) by a plurality of bearing sites (22) on the circumferential side, and at least one compensating weight element (23) is arranged between two bearing sites (22) adjacent to each other in the circumferential direction.

5. The optical element according to claim 4, characterized in that one compensating weight element (23) is respectively provided between all bearing sites (22) adjacent to each other in the circumferential direction.

6. The optical element according to any one of claims 1 to 5, characterized in that at least one compensating weight element (20; 20, 23; 23) is connected to the body (18) in an interlocking and / or integral engagement manner.

7. The optical element according to any one of claims 1 to 6, wherein the connecting rod (29; 32) is implemented to be adjustable in terms of the length and / or direction of the connecting rod.

8. The optical element according to any one of claims 1 to 7, characterized in that the compensating weight element (20; 23; 26; 27; 31, 36; 43) is connected to the body (18) by an additional element.

9. A method for producing an optical element (M; M1 to M10) adjusted as claimed in any one of claims 1 to 8, comprising the following steps: Producing a blank of the optical element (M; M1 to M10) taking into account negative deformation tolerances; Transferring the blank to a use position of a device (1) for projection lithography; Taking into account the acceleration due to gravity at the location of use, at least one compensating weight element (20; 23; 26; 27; 31; 36; 43) is attached to the body (18) of the optical element (M) for weight compensation of the figure deformation of the optical surface caused by gravity.

10. An imaging optical unit (7) having at least one optical element (M; M1 to M10) as claimed in any one of claims 1 to 8, for imaging an object field (4) into an image field (8), wherein an object (10) to be imaged can be arranged in the object field and a substrate (11) can be arranged in the image field.

11. An optical system, comprising the imaging optical unit as claimed in claim 10, comprising an illumination optical unit (6) for illuminating the object field (4) with illumination light (3) from a light source (2).

12. A projection exposure apparatus comprising the optical system as claimed in claim 11 and comprising a light source (2) for generating illumination light (3).

13. A method for producing a structured component, comprising the following method steps: providing a mask master (10) and a wafer (11); projecting the structures on the mask master (10) onto the light-sensitive layer of the wafer (11) with the assistance of the projection exposure apparatus as claimed in claim 12, producing microstructures or nanostructures on the wafer (11).

14. A structured component produced according to the method as claimed in claim 13.

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