Bipod, optical system, and projection exposure apparatus

Abstract

A bipod (202, 202A, 202B, 204, 206) for adjusting optical elements (102, 102') of an optical system (100) of a projection exposure apparatus (1), the bipod (202, 202A, 202B, 204, 206) comprising: a mechanism (224) connectable to the optical elements (102, 102') for adjusting the optical elements (102, 102'); a base portion (218); a first tower portion (220) extending from the base portion (218); and a mechanism (224) connectable to the first tower portion (220). ) and a second tower portion (222) that also extends from the base portion (218), unlike the first tower portion (220), and the mechanism (224) is disposed between the first tower portion (220) and the second tower portion (222), and the first tower portion (220) and the second tower portion (222) are connected to each other on the side opposite the base portion (218) to increase the rigidity of the bipod (202, 202A, 202B, 204, 206).

Description

[Technical Field]

[0001] The present invention relates to a bipod for adjusting optical elements of an optical system of a projection exposure apparatus, an optical system equipped with such a bipod, and a projection exposure apparatus equipped with such a bipod and / or such an optical system.

[0002] The content of the priority application German Patent Application No. 10 2022 209 902.8 is incorporated by reference in its entirety. [Background technology]

[0003] Microlithography is used in the manufacture of finely structured components, such as integrated circuits. The microlithography process is carried out using a lithography apparatus having an illumination system and a projection system. An image of a mask (reticle) illuminated by the illumination system is projected by the projection system onto a substrate, such as a silicon wafer, that is coated with a photosensitive layer (photoresist) and positioned in the image plane of the projection system, thereby transferring the mask structure into the photosensitive coating on the substrate.

[0004] Due to the desire for ever smaller structures in the manufacture of integrated circuits, deep ultraviolet (DUV) lithography systems are currently under development that use light with wavelengths in the range of 30 nm to 250 nm, particularly 193 nm, which can use reflective optical units, i.e., mirrors, instead of conventional refractive optical units, i.e., lens elements.

[0005] So-called manipulators or bipods can be used to adjust the mirrors of such a projection system. Three bipods can be assigned to each mirror. Using these three bipods, each mirror can be adjusted with six degrees of freedom. To optimize the dynamics of such a system, maximum stiffness is desirable. However, at the same time, the ability to adjust the mirrors should not be limited. Summary of the Invention [Problem to be solved by the invention]

[0006] Against this background, it is an object of the present invention to provide an improved bipod. [Means for solving the problem]

[0007] Accordingly, a bipod for adjusting an optical element of an optical system of a projection exposure apparatus is provided, the bipod comprising: a mechanism coupleable to the optical element for adjusting the optical element; a base; a first tower extending from the base; and a second tower different from the first tower but also extending from the base, the mechanism being disposed between the first and second towers, the first and second towers being connected to each other on the side opposite the base to increase the rigidity of the bipod.

[0008] The interconnection of the first and second towers allows for increased rigidity of the bipod, which in turn allows for optimized dynamics of the bipod or optical system. In this way, vibrations of the towers can be reliably avoided in the event of dynamic vibration of the bipod. High-precision adjustment of the optical elements is possible without being affected by vibrations.

[0009] The bipod may also be referred to as a manipulator. A plurality of such bipods may be assigned to the optical system. The optical element is preferably a mirror, in particular a DUV mirror. The optical element has an optically effective surface configured to reflect illumination radiation, in particular DUV radiation. The optically effective surface may be a mirror surface. However, the optical element may also be a lens element, etc.

[0010] The optical system can be a projection optical unit or part of a projection optical unit of a projection exposure apparatus. The optical system can therefore also be referred to as a projection optical unit or a projection lens. Alternatively, the optical system can also be an illumination optical unit or part of such an illumination optical unit. However, in the following it will be assumed that the optical system is a projection optical unit as described above or part of such a projection optical unit. The optical system can comprise a number of optical elements.

[0011] A coordinate system having a first spatial direction or x-direction, a second spatial direction or y-direction, and a third spatial direction or z-direction is assigned to the bipod or optical system. The spatial directions are aligned perpendicular to one another. The optical element or optically effective surface has six degrees of freedom, specifically, three translational degrees of freedom along the x-direction, y-direction, and z-direction, respectively, and three rotational degrees of freedom about the x-direction, y-direction, and z-direction, respectively. That is, the position and orientation of the optical element or optically effective surface can be determined or described using the six degrees of freedom.

[0012] The "position" of an optical element or an optically effective surface is understood to mean its coordinates relative to the x-, y-, and z-directions or the coordinates of a measurement point provided on the optical element. The "orientation" of an optical element or an optically effective surface is understood to mean, in particular, its tilt relative to the three spatial directions. That is, the optical element or the optically effective surface can be tilted about the x-, y-, and / or z-direction.

[0013] This provides six degrees of freedom in the position and / or orientation of the optical element or optically effective surface. The "attitude" of the optical element or optically effective surface preferably encompasses both its position and its orientation. The term "attitude" can be appropriately replaced with the expression "position and orientation" and vice versa.

[0014] "Adjustment" or "alignment" of an optical element or an optically effective surface is understood to mean, in particular, a change in the attitude of the optical element or the optically effective surface. For example, the optical element can be moved from an actual position to a target position and vice versa using one or more bipods. Thus, adjustment or alignment of the optical element or the optically effective surface can be performed in all six degrees of freedom.

[0015] The mechanism may also be referred to as a motion mechanism. Preferably, the mechanism includes a coupling element that can be operatively connected or coupled to the optical element. For example, the optical element may have a plurality of mirror sockets on its rear side, with each mirror socket assigned one bipod operatively connected to each coupling element. For this purpose, an intermediate frame may be provided between one or more bipods and the optical element.

[0016] The mechanism preferably includes a plurality of lever arms interconnected by means of so-called flexures. A "flexure" is generally understood to mean a region of a component, such as a narrowed or thin-walled section, that allows relative movement between two rigid regions of the component by bending. In this case, the lever arms form rigid regions that are movably connected to one another by means of flexures.

[0017] The mechanism is configured to convert the movement of the actuating element into a movement of the coupling element by means of the lever arm and / or flexure. This movement can be converted here with a defined transmission ratio. Furthermore, the mechanism is also suitable for converting the direction of action of the actuating element into a movement of the coupling element in a different direction. The actuating element can be part of the mechanism. A plurality of actuating elements can be provided. Thus, one or more actuating elements are specifically configured to move the coupling element via the lever arm and flexure.

[0018] In particular, the mechanism is suitable for translationally or linearly moving and / or tilting the coupling element. Pure linear, pure tilting, or a combination of linear and tilting movements of the coupling element can be performed. For example, the mechanism can move the coupling element linearly along one of the spatial directions and tilt it about another of the spatial directions.

[0019] For example, the mechanism can move the coupling element linearly along the z-direction and tilt about the x-direction. Thus, the mechanism is configured to change or adjust the orientation of the coupling element in two degrees of freedom. By combining multiple such bipods that adjust the optical element together, it is possible to move the optical element in all six degrees of freedom, and thus change its orientation.

[0020] Preferably, the mechanism comprises exactly two actuating elements or actuators. The actuating elements may be piezo elements. The actuating elements are arranged in suitable pockets in the mechanism. The actuating elements are capable of linear motion, which is transmitted to the coupling element by means of the mechanism. The movement of each actuating element can be converted into a movement of the coupling element by means of said lever arms and / or flexures.

[0021] The base portion is particularly rod- or strip-shaped. The base portion may preferably extend along one of the spatial directions, for example along the y-direction. The base portion has a first end and a second end. A first tower portion is provided at the first end. A second tower portion is provided at the second end. Both the first tower portion and the second tower portion are arranged perpendicular to the base portion. For example, the tower portion extends along the z-direction, which is perpendicular to the y-direction. Thus, the base portion and the tower portion form a U-shape. For example, the first tower portion, the second tower portion, and the mechanism extend upward from the base portion.

[0022] The base part, the first tower part, and the second tower part form an integral component, in particular a component made of one piece of material. "Integral" or "one piece" means in particular here that the base part, the first tower part, and the second tower part form a common component rather than being made of different subcomponents. "Made of one piece of material" means in particular here that the entire base part, the first tower part, and the second tower part are made of the same material. In particular, the feature can also be formed integrally with the base part, in particular from one piece of material. Thus, the feature can be part of the base part or vice versa.

[0023] The second tower being "different" from the first tower means in particular that the first and second towers are not identical but form two separate parts or regions of the bipod, the first and second towers being spaced apart in particular when viewed along the y-direction, and the mechanism being located between the first and second towers.

[0024] For example, the mechanism is disposed between a first tower section and a second tower section when viewed along the y direction. The tower sections may each have a rectangular cross-sectional shape. The base section may also have a rectangular cross-sectional shape. The bipod is particularly in the form of a panel. In particular, "panel form" is understood here to mean that the geometric extent of the bipod when viewed along the y and z directions is significantly greater than when viewed along the x direction.

[0025] A first connection point for connecting the bipod to a fixed environment, e.g., a so-called force frame, can be provided on the first tower section. Correspondingly, a second connection point for connecting to a fixed environment can be provided on the second tower section. The connection point can be, for example, a screw hole. Therefore, the tower section can also be referred to as an assembly tower, since it can be used to enable connection or attachment to a fixed environment. The connection point is provided at the end or end of each tower section opposite the base section. In this way, the connection point is provided on the tower section, not on the base section itself. Therefore, the connection point can be positioned offset upward relative to the base section when viewed along the z-direction.

[0026] As mentioned above, the first and second tower sections are each connected to the base section by a first end or first ends integrally, in particular by means of one piece of material. The first and second tower sections are connected to each other at a second end or second ends of the respective tower sections opposite the base section. For this purpose, stiffening elements may for example be provided which are rigidly connected to the first and second tower sections, in particular screw-connected. Thus, "opposite" the base section means that the tower sections are connected to each other at their second end or second ends rather than at their first end or first ends. This connection allows forces to be transmitted from the first tower section to the second tower section and vice versa.

[0027] "Stiffness" is generally understood to mean the resistance of an object, in this case a bipod or tower section, to elastic deformation due to an external load. This external load may include forces and / or moments. Stiffness is determined by the materials used in the deformed object and its shape. Thus, the shape of the bipod, and in particular of the mechanism, can be optimized to achieve maximum stiffness. The higher the stiffness, the better the dynamic behavior.

[0028] According to one embodiment, the base part, the first tower part, the second tower part and the mechanism form a unitary component, in particular a component made from a single material.

[0029] This particularly means that the base, first tower, second tower, and mechanism form one common component rather than being composed of different substructures. The lever arm and flexure can be manufactured by subtractive manufacturing methods. For example, the lever arm can be manufactured using a milling method, and the flexure can be manufactured using an erosion method. A slot or notch is optionally provided between the lever arms to allow the lever arm to move around the flexure.

[0030] According to yet another embodiment, a first notch is provided between the first tower and the mechanism, and a second notch is provided between the second tower and the mechanism.

[0031] The notches may also be referred to as slots or gaps. The first notch is used to separate or decouple the first tower from the mechanism. Correspondingly, the second tower is separated or decoupled from the mechanism using the second notch. Therefore, the mechanism cannot apply a force directly to the tower. Conversely, the tower cannot therefore apply a force to the mechanism. Therefore, it is preferable that the tower is mechanically decoupled from the mechanism rather than being directly connected to it.

[0032] According to yet another embodiment, the mechanism has a first pocket that houses the first actuating element and a second pocket that houses the second actuating element, the pockets being closed at the rear.

[0033] Preferably, exactly two actuating elements are provided. The actuating elements may be piezo actuators. The actuating elements may also be called actuators. In particular, the actuating elements are linear actuating elements or linear actuators. The actuating elements can be used to deflect the aforementioned lever arms of the mechanism in order to move the connecting element in this way and change its orientation. The first pocket and the second pocket each have a rear wall. In particular, this means that the pockets do not penetrate the mechanism. Since the rear sides of the pockets are closed, the mechanism can achieve a higher local stiffness in the area of ​​the pockets.

[0034] According to yet another embodiment, the bipod further comprises a stiffening element connecting the first tower section and the second tower section opposite the base section.

[0035] The stiffening element is provided in particular on the rear side of the bipod. In particular, "rear" means that the stiffening element is arranged on the opposite side from the actuating element. The stiffening element is preferably in the form of a panel. The stiffening element can therefore also be referred to as a stiffening panel. The terms "stiffening element" and "stiffening panel" are therefore interchangeable as needed. The stiffening element can be, for example, a steel sheet or an aluminum sheet. The stiffening element can be connected to the first and second tower parts by means of fastening points. At these fastening points, the stiffening element can be screw-connected to the tower parts.

[0036] According to yet another embodiment, the stiffening element is connected to the base portion.

[0037] For this purpose, the stiffening element has further connection points, for example two connection points are provided for connecting the stiffening element to the base part, at which the stiffening element can be screwed to the base part.

[0038] According to yet another embodiment, the stiffening element has a recess on the side opposite the bipod.

[0039] In particular, the recess is positioned on the opposite side to the mechanism and / or the tower. Preferably, the stiffening element has a front side where the stiffening element abuts the tower and a rear side where the recess is provided. By providing the recess, it is possible to create sufficient installation space for further components arranged adjacent to the bipod.

[0040] According to yet another embodiment, the recess has a plurality of recesses extending to different depths in the stiffening element, as a result of which the recess has a stepped shape.

[0041] For example, a first recess, a second recess, and a third recess are provided, the second recess being deeper than the first recess, and the third recess being deeper than the second recess, thereby achieving a stepped or staircase-like shape of the recess on the side opposite the tower portion.

[0042] According to yet another embodiment, the bipod further comprises an exoskeleton connecting the first tower section and the second tower section opposite the base section.

[0043] "Opposite" the base section specifically means in this case that the first and second tower sections are connected to each other at the end or ends of each tower section opposite the base section using an exoskeleton. The exoskeleton may also be referred to as a stiffening skeleton or stiffening section. Thus, the terms "exoskeleton," "stiffening skeleton," and "stiffening section" are interchangeable where appropriate. "Exoskeleton" may be understood herein to refer very generally to a component or portion of a bipod that connects the first tower section to the second tower section opposite the base section in order to stiffen the bipod.

[0044] According to yet another embodiment, the first tower section, the second tower section and the exoskeleton are integrally connected to each other, in particular by a single material.

[0045] In particular, the mechanism is also integrally connected to the base, in particular by a single piece of material, and the base is further integrally connected to the first and second towers, in particular by a single piece of material. However, the exoskeleton itself is not connected to the mechanism. For this purpose, corresponding slots or notches are provided between the exoskeleton and the mechanism, allowing movement of the mechanism or of the lever arms and flexures of the mechanism.

[0046] According to yet another embodiment, the mechanism is at least partially disposed within the exoskeleton.

[0047] In particular, this means that the exoskeleton at least partially surrounds or encloses the mechanism. For example, the exoskeleton may include a rod-shaped base connected to a first tower via a first connection and to a second tower via a second connection. An opening may be provided in the base through which the movable coupling element passes. The coupling element can thus be moved within this opening.

[0048] According to yet another embodiment, the base, first tower, second tower, and exoskeleton form a frame-type shape that extends around the entire perimeter of the mechanism.

[0049] For example, the base and exoskeleton form two parts of a bipod frame extending along the y direction, and the tower forms two parts of the frame extending along the z direction, and mechanisms are thus located within this frame-type shape or within this frame formed from the base, tower, and exoskeleton.

[0050] An optical system of a projection exposure apparatus is further proposed, which comprises an optical element and at least one bipod as described above, wherein the at least one bipod is coupled to the optical element by means of a mechanism.

[0051] As mentioned above, the optical system can be an illumination optical unit or a projection optical unit of a projection exposure apparatus. The optical system can have a plurality of optical elements. The bipod is operatively connected to the optical elements using the coupling element. The intermediate frame can be provided between the bipod and the optical elements. The optical elements can have a plurality of mirror sockets on their underside, and the coupling element of the bipod is operatively connected to one of the mirror sockets.

[0052] According to one embodiment, the optical system further comprises a first bipod, a second bipod and a third bipod, the optical element being adjustable with six degrees of freedom to move the optical element from an actual attitude to a target attitude and vice versa, with each bipod being assigned two of the six degrees of freedom.

[0053] In particular, exactly three bipods are provided. Each bipod is preferably assigned to one mirror socket of the optical element. The bipods may be adapted to deflect the intermediate frame supporting the optical element. However, the intermediate frame is optional. The optical element can be moved from its actual position to its target position and vice versa using the bipods. For example, the optical element in the target position meets specific optical specifications or requirements that the optical element in the actual position does not meet. To move the optical element from the actual position to the target position, the optical system comprises an adjustment device. The adjustment device may include three bipods. Furthermore, the adjustment device includes an open-loop / closed-loop control unit configured to control the bipods, in particular the actuating elements of the bipods, to adjust or align the optical element.

[0054] Furthermore, a projection exposure apparatus is proposed, which comprises the bipod and / or the optical system described above.

[0055] The optical system is preferably a projection optical unit of a projection exposure apparatus. However, the optical system can also be an illumination optical unit of a projection exposure apparatus. The projection exposure apparatus can be an EUV lithography apparatus. EUV stands for "extreme ultraviolet" and refers to a wavelength of light used between 0.1 nm and 30 nm. The projection exposure apparatus can also be a DUV lithography apparatus. DUV stands for "deep ultraviolet" and refers to a wavelength of light used between 30 nm and 250 nm.

[0056] In this context, "a" or "an" or "one" should not necessarily be construed as limiting to exactly one element. Rather, there can be a plurality of elements, such as two, three, or more. Any other numbers used herein should not be construed as limiting to a precise number of elements. Instead, unless otherwise specified, the number can be increased or decreased.

[0057] The embodiments and features described for the bipod are correspondingly applicable to the proposed optical system and / or the proposed projection exposure apparatus, and vice versa.

[0058] Further possible implementations of the present invention also include not explicitly mentioned combinations of the features and embodiments described above or below with respect to the exemplary embodiments, in which case a person skilled in the art will also be able to add individual aspects as improvements or supplements to each basic form of the invention.

[0059] Further advantageous configurations and aspects of the invention are the subject of the dependent claims and also of exemplary embodiments of the invention which will be described later in this specification. The invention will be further explained in more detail on the basis of preferred embodiments with reference to the attached drawings. [Brief explanation of the drawings]

[0060] [Figure 1] 1 shows a schematic meridional section of a projection exposure apparatus for DUV projection lithography; [Figure 2] 2 shows a schematic diagram of an embodiment of the optical system of the projection exposure apparatus shown in FIG. 1. [Figure 3] 3 shows a schematic top view of the optical system shown in FIG. 2. [Figure 4] 3 shows a schematic front view of an embodiment of a bipod of the optical system shown in FIG. 2. [Figure 5] A schematic rear view of the bipod shown in Figure 4 is shown. [Figure 6] 3 shows a schematic front view of yet another embodiment of the bipod of the optical system shown in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0061] Unless otherwise noted, identical or functionally identical elements are given the same reference numerals throughout the figures. It should also be noted that illustrations in the figures are not necessarily to scale.

[0062] FIG. 1 shows a schematic diagram of a projection exposure apparatus 1, particularly a DUV lithography apparatus, equipped with a beam shaping and illumination system 2 (also referred to herein as an "illumination optical unit") and a projection optical unit 4 (also referred to herein as a "projection lens"). In this case, DUV stands for "deep ultraviolet" and refers to the wavelength of light used, which is between 30 nm and 250 nm. The beam shaping and illumination system 2 and the projection system 4 are preferably arranged in vacuum housings (not shown). Each vacuum housing is evacuated using an exhaust system (not shown). The vacuum housing is surrounded by a machine chamber (not shown), and a drive unit for mechanically moving or setting the optical elements may be provided in the machine chamber. Furthermore, an electrical controller or the like may be provided in the machine chamber.

[0063] The projection exposure apparatus 1 comprises a light source 6. For example, an ArF excimer laser emitting radiation 8 in the deep UV range, for example at 193 nm, can be provided as light source 6. In a beam shaping and illumination system 2, the radiation 8 is focused and a desired operating wavelength (used light) is filtered out of the radiation 8. The beam shaping and illumination system 2 can comprise optical elements, not shown, for example mirrors or lenses.

[0064] After passing through the beam shaping and illumination system 2, the radiation 8 is directed onto a photomask or reticle 10. The photomask 10 may be formed as a transmissive optical element and may be located external to the beam shaping and illumination system 2 and the projection optical unit 4. The photomask 10 has structures that are imaged in reduced form onto a wafer 12 by the projection optical unit 4.

[0065] The projection optical unit 4 has a plurality of lens elements 14, 16, 18 and / or mirrors 20, 22 for imaging the photomask 10 onto the wafer 12. In this case, the individual lens elements 14, 16, 18 and / or mirrors 20, 22 of the projection optical unit 4 may be arranged symmetrically with respect to an optical axis 24 of the projection optical unit 4. It should be noted that the numbers of lens elements 14, 16, 18 and mirrors 20, 22 shown here are for illustrative purposes only and are not limited to the numbers shown. More or fewer lens elements 14, 16, 18 and / or mirrors 20, 22 may be provided.

[0066] The air gap between the final lens element (not shown) and the wafer 12 can be replaced with a liquid medium 26 having a refractive index greater than 1. The liquid medium 26 can be, for example, high-purity water. Such an arrangement is also referred to as immersion lithography and has high photolithographic resolution. The medium 26 can also be referred to as an immersion liquid.

[0067] Figure 2 shows a schematic diagram of an embodiment of an optical system 100 of a projection exposure apparatus, and Figure 3 shows a schematic top view of the optical system 100. In the following text, reference is made simultaneously to Figures 2 and 3.

[0068] The optical system 100 can be a projection optical unit 4 as described above or a part of the projection optical unit 4. Therefore, the optical system 100 can also be referred to as a projection optical unit. However, the optical system 100 can also be a beam shaping and illumination system 2 as described above or a part of the beam shaping and illumination system 2. Therefore, the optical system 100 can alternatively be referred to as a beam shaping and illumination system. However, in the following text, the optical system 100 will be referred to as a projection optical unit 4 or a part of the projection optical unit 4. The optical system 100 is suitable for DUV lithography. However, the projection system 100 can also be suitable for EUV lithography.

[0069] The optical system 100 may include multiple optical elements 102, only one of which is shown in Figures 2 and 3. Therefore, only one optical element 102 will be described below. The optical element 102 may be one of the lens elements 14, 16, 18 or one of the mirrors 20, 22. In the following text, the optical element 102 will be referred to as one of the mirrors 20, 22. The optical element 102 includes a substrate 104 and an optically active surface 106, e.g., a mirror surface. The substrate 104 may also be referred to as a mirror substrate. The substrate 104 may include glass, ceramic, glass-ceramic, or other suitable material.

[0070] The optically active surface 106 is provided on the front side 108 of the substrate 104. The optically active surface 106 can be realized by means of a coating applied to the front side 108. The optically active surface 106 is a mirror surface. The optically active surface 106 is suitable for reflecting illumination radiation, in particular DUV radiation, during operation of the optical system 100. The optically active surface 106 can have an oval or elliptical shape in the top view shown in FIG. 3. The optical element 102 or the substrate 104 can have a triangular shape. However, the shape is generally arbitrary.

[0071] The optical element 102 has a rear side 110 opposite the optically active surface 106 or the front side 108. The rear side 110 does not have any distinct optical properties, i.e., in particular, the rear side 110 does not have any mirrored surface and therefore no reflective properties.

[0072] A plurality of mirror sockets 112, 114, 116 are provided on the rear side 110. A first mirror socket 112, a second mirror socket 114, and a third mirror socket 116 are provided. In other words, the optical element 102 includes exactly three mirror sockets 112, 114, 116. The mirror sockets 112, 114, 116 can have geometrically identical designs. The mirror sockets 112, 114, 116 are cylindrical and extend downward from the rear side 110 in the orientation shown in FIG. 2. The mirror sockets 112, 114, 116 form the corners of an imaginary triangle.

[0073] The optical element 102 or optically effective surface 106 has six degrees of freedom, namely three translational degrees of freedom along the first spatial direction or x-direction x, the second spatial direction or y-direction y, and the third spatial direction z-direction z, respectively, and three rotational degrees of freedom about the x-direction x, the y-direction y, and the z-direction z, respectively. That is, the position and orientation of the optical element 102 or optically effective surface 106 can be determined or described using the six degrees of freedom.

[0074] The "position" of the optical element 102 or the optically effective surface 106 is particularly understood to mean its coordinates with respect to the x-direction x, the y-direction y, and the z-direction z, or the coordinates of a measurement point provided on the optical element 102. The "orientation" of the optical element 102 or the optically effective surface 106 is particularly understood to mean its tilt with respect to the three spatial directions x, y, and z. That is, the optical element 102 or the optically effective surface 106 can be tilted about the x-direction x, the y-direction y, and / or the z-direction z.

[0075] This provides six degrees of freedom in the position and / or orientation of the optical element 102 or the optically effective surface 106. The "attitude" of the optical element 102 or the optically effective surface 106 encompasses both its position and its orientation. The term "attitude" can be appropriately interchanged with the expression "position and orientation" and vice versa.

[0076] 2 shows an actual position IL of the optical element 102 or the optically effective surface 106 in solid lines and a target position SL of the optical element 102 or the optically effective surface 106 in dashed lines using the reference numerals 102' and 106'. The optical element 102 can be moved from its actual position IL to its target position SL, and vice versa. For example, the optical element 102 in the target position SL satisfies a particular optical specification or requirement that the optical element 102 in the actual position IL does not satisfy.

[0077] In order to move the optical element 102 from the actual position IL to the target position SL, the optical system 100 includes an adjustment device 200. The adjustment device 200 is configured to adjust the optical element 102. In particular, "adjustment" or "alignment" is understood herein to mean a change in the position of the optical element 102. For example, the optical element 102 can be moved from the actual position IL to the target position SL and vice versa using the adjustment device 200. Thus, the adjustment or alignment of the optical element 102 can be performed in all six degrees of freedom using the adjustment device 200.

[0078] The adjustment device 200 includes a number of manipulators or bipods 202, 204, 206, which are only shown very diagrammatically in Figure 2. One bipod 202, 204, 206 is assigned to each mirror socket 112, 114, 116. In particular, this means that exactly three bipods 202, 204, 206 are provided. Each bipod 202, 204, 206 can be assigned two of the above degrees of freedom. Thus, using the three bipods 202, 204, 206, adjustment of the optical element 102 in all six degrees of freedom is possible.

[0079] The first bipod 202 is assigned to the first mirror socket 112. The second bipod 204 is assigned to the second mirror socket 114. The third bipod 206 is assigned to the third mirror socket 116. The bipods 202, 204, and 206 have the same design. Therefore, only the first bipod 202 and the first mirror socket 112 will be described below and will be referred to simply as the bipod 202 and the mirror socket 112, respectively.

[0080] The bipod 202 is coupled to a fixed environment 212 using a first junction point 208 and a second junction point 210. The fixed environment 212 can be a force frame or any other immovable structure. For example, the bipod 202 is connected to the fixed environment 212 using a threaded connection at the junction points 208, 210. The bipod 202 further comprises a coupling element 214 coupled to a mirror socket 112 assigned to the bipod 202. An intermediate frame (not shown) can be provided between the coupling element 214 and the mirror socket 112.

[0081] The bipod 202 is assigned two actuators or actuating elements (not shown), which can be controlled using the open-loop / closed-loop control unit 216 of the adjustment device 200. All actuating elements of all bipods 202, 204, 206 are actively connected to the open-loop / closed-loop control unit 216, so that the open-loop / closed-loop control unit 216 can adjust the optical element 102 in all six degrees of freedom by appropriate control of these actuating elements.

[0082] Figure 4 shows a schematic front view of one embodiment of the bipod 202A as described above. Figure 5 shows a schematic rear view of the bipod 202A. In the following text, both Figures 4 and 5 will be referred to simultaneously.

[0083] In order to enhance the dynamics of the optical system 100 and the bipod 202A, it is desirable to increase the stiffness of the bipod 202A. The term "stiffness" is generally understood herein to mean the resistance of a component to elastic deformation due to an external load, in particular a force and / or a moment. Stiffness correlates the load on a component to its deformation. Stiffness is determined by the material of the component and its geometry, in particular its shape and size.

[0084] Stiffening is achieved structurally by adapting the design of the bipod 202A and by attaching stiffening or frame structures, as described below, that provide additional stiffness to the bipod 202A. Additionally, the motion mechanisms or mechanisms of the bipod 202A, as described below, are optimized to allow for high stiffness and high dynamics at the same time.

[0085] Local deformations of the bipod 202A can contribute to a decrease in the dynamic performance of the optical system 100 or the bipod 202A. The objective here is to achieve a structure that is as rigid as possible within a limited installation space. As the requirements regarding dynamic behavior increase, so does the complexity. In this regard, the smaller the installation space, the greater the requirements regarding the amount of movement of the bipod 202A and its positional accuracy. As a result of these requirements, the bipod 202A must be designed to be robust in order to increase its overall rigidity.

[0086] The bipod 202A has a shape that is essentially in the form of a panel. "Panel form" means in this context that the geometric extent of the bipod 202A when viewed in the y-direction y and z-direction z is significantly greater than when viewed along the x-direction x. The cross section of the bipod 202A is substantially rectangular. However, the coupling element 214 may be cylindrical.

[0087] The bipod 202A includes a rod-shaped base portion 218 extending along the y-direction in the orientation shown in Figures 4 and 5. A first tower portion 220 and a second tower portion 222 are provided at each end of the base portion 218. The tower portions 220 and 222 extend along the z-direction z and are therefore disposed perpendicular to the base portion 218. The base portion 218 and the tower portions 220 and 222 are integrally formed, in particular from a single material.

[0088] "Integral" or "one piece" specifically means herein that the base portion 218 and the tower portions 220, 222 form one common component rather than being made up of multiple subcomponents. In particular, "of one material" means that the entire base portion 218 and the tower portions 220, 222 are manufactured from the same material. Suitable materials used are, for example, metallic materials, especially aluminum alloys or steel alloys.

[0089] The first tower section 220 is provided with a first connection point 208, which may be, for example, a screw hole. The first tower section 220 is thus connected to the fixed environment 212 using the first connection point 208. Correspondingly, a second connection point 210, which may also be a screw hole, is provided on the second tower section 222. The second tower section 222 is thus connected to the fixed environment 212 using the second connection point 210.

[0090] When viewed along the y direction, the junctions 208, 210 are spaced apart from each other. When viewed along the z direction, the junctions 208, 210 are located above the base portion 218. Therefore, the base portion 218 itself does not have the junctions 208, 210. The base portion 218 thus does not have the junctions 208, 210. In other words, the base portion 218 is junction-less or has no junctions. Therefore, the base portion 218 itself is not directly connected to the fixed world 212.

[0091] A movement mechanism or mechanism 224 is provided between the first tower section 220 and the second tower section 222, the structural design of which will not be described in further detail. The mechanism 224 can be used to move the coupling element 214 linearly along the z-direction z and / or tilt it about the x-direction x. Linear movement along the z-direction z, linear movement along the y-direction y, diagonal linear movement in a plane defined by the y-direction y and the z-direction z, or linear movement alone in combination with rotational movement about the x-direction x can be performed. Figure 4 shows the purely linear movement of the coupling element 214 along the z-direction z. The coupling element 214 is part of the mechanism 224.

[0092] The coupling element 214 can therefore be moved with two degrees of freedom from a starting position AL, shown in solid lines, to any desired end position EL, shown in dashed lines and with the coupling element referenced 214'. The number of end positions EL is arbitrary. In particular, any intermediate position (not shown) can be set between the starting position AL and the end position EL.

[0093] Mechanism 224 includes a first actuating element 226 and a second actuating element 228 that is different from first actuating element 226. Actuating elements 226, 228 may also be referred to as actuators. Actuating elements 226, 228 may be or be referred to as piezo actuating elements or piezo actuators. Mechanism 224 includes a first pocket 230 that houses first actuating element 226 and a second pocket 232 that houses second actuating element 228. Pockets 230, 232 are closed at the rear in the orientation of FIG. 4.

[0094] As previously mentioned, the actuating elements 226, 228 are controllable using the open-loop / closed-loop control unit 216 to change the attitude of the coupling element 214 or, using all three bipods 202, 202A, 204, 206 together, to change the attitude of the optical element 102. To transfer the motion or travel 234, 236 of each actuating element 226, 228 to the coupling element 214, the mechanism 224 includes multiple lever arms (not shown) formed with notches and flexures that allow the lever arms to pivot.

[0095] For example, each of the travels 234, 236 can be multiplied using the mechanism 224, like a transmission. The mechanism 224 thus multiplies each of the travels 234 toward the coupling element 214, so that a small deflection of each of the actuating elements 226, 228 leads to a large deflection of the coupling element 214. The mechanism 224 can have a particular transmission ratio that translates each of the travels 234, 236 into a corresponding deflection of the coupling element 214.

[0096] With the exception of actuating elements 226, 228, mechanism 224 is a unitary component, in particular a component made of one piece of material. The lever arm described above can be manufactured by a milling method, and the flexure can be manufactured using an erosion method. Mechanism 224, coupling element 214, and base portion 218 form a unitary component, in particular a component made of one piece of material. In particular, this means that mechanism 224 can be part of base portion 218 or vice versa.

[0097] Slots or notches 238, 240 are provided between the tower sections 220, 222 and the mechanism 224, respectively, so that the mechanism 224 is not directly connected to the tower sections 220, 224. A first notch 238 and a second notch 240 are provided. The first notch 238 is provided between the first tower section 220 and the mechanism 224. The second notch 240 is provided between the second tower section 222 and the notch 224.

[0098] Because the tower sections 220, 222 are not connected to the mechanism 224, they may be subject to undesired deformation. To increase the rigidity of the bipod 202A, a stiffening element 242 is provided that interconnects the tower sections 220, 222 and stiffens the bipod 202A. The stiffening element 242 is in the form of a panel and may therefore also be referred to as a stiffening panel. Therefore, the terms "stiffening element" and "stiffening panel" are interchangeable, if desired. The stiffening element 242 is part of the bipod 202A.

[0099] The stiffening element 242 can be made of a metallic material, for example a steel alloy or an aluminum alloy. The stiffening element 242 has a significantly smaller wall thickness compared to the bipod 202A when viewed along the x-direction. The stiffening element 242 can be in the form of a sheet or a thin plate, in particular a steel or aluminum sheet.

[0100] The stiffening element 242 includes a plurality of fastening points 244, 246, 248, 250. The fastening points 244, 246, 248, 250 may be openings or holes in the fastening element 242. A first fastening point 244 is assigned to the first tower section 220, a second fastening point 246 is assigned to the second tower section 222, a third fastening point 248 is assigned to the base section 218, and a fourth fastening point 250 is also assigned to the base section 218. The stiffening element 242 may be threadably connected to the tower sections 220, 222 at the fastening points 244, 246 and to the base section 218 at the fastening points 248, 250.

[0101] The stiffening element 242 is provided with a depression or recess 252 on the side opposite the bipod 202A, which extends into the stiffening element 242 when viewed along the x-direction to locally thin or reduce the wall thickness of the stiffening element 242. The recess 252 can be stepped and have a plurality of recesses 254, 256, 258. A first recess 254, a second recess 256, and a third recess 258 are provided.

[0102] The second recess 256 extends deeper into the stiffening element 242 than the first recess 254 when viewed along the x-direction x, and the third recess 258 extends deeper into the stiffening element 242 than the second recess 256 when viewed along the x-direction x. A stepped or staircase-like shape of the recess 252 is thus obtained.

[0103] 4 and 5, bipod 202A is structurally adapted to have tower sections 220, 222 on the left and right sides, respectively, of base section 218. Junction points 208, 210 of bipod 202A are each located upward toward the end of each tower section 220, 222 opposite base section 218. Because tower sections 220, 222 are connected to base section 218 at only one end and each connection cross-section between corresponding tower section 220, 222 and base section 218 is relatively thin, dynamic excitation of bipod 202A may cause undesired vibration of tower sections 220, 222.

[0104] To dampen these vibrations of the tower sections 220, 222 and the associated deformations at the transitions between the tower sections 220, 222 and the base section 218, the tower sections 220, 222 and the base section 218 are interconnected using stiffening elements 242. The stiffening elements 242 provide additional stiffness to the tower sections 220, 222.

[0105] Due to the limited installation space, the stiffening element 242 is recessed on the outside, i.e., on the side opposite the tower sections 220, 222, with a recess 252 to provide sufficient distance from adjacent components. The rear recess 252 of the stiffening element 242 can serve as a movement space for the bipod movement mechanism. Furthermore, the pockets 230, 232 are closed on one side. This local material reinforcement ensures increased local stiffness in the area of ​​the pockets 230, 232.

[0106] The mechanism 224 is optimized in the design of the bipod 202A. The flexures of the mechanism 224 are optimized with respect to stress and stiffness. Furthermore, the alignment of the swivel joint with the rotation area is adapted to achieve higher stiffness while maintaining the joint stress. The design of the bipod 202A allows the manufacturing process to be adapted. The contours of the bipod 202A are realized by milling and the flexures are cut.

[0107] FIG. 6 shows a schematic front view of yet another embodiment of a bipod 202B as described above.

[0108] The design of the bipod 202B is substantially the same as the design of the bipod 202A, and therefore only the differences between the two embodiments of the bipod 202A, 202B will be described below.

[0109] In contrast to bipod 202A, bipod 202B does not have a stiffening element 242 as previously described, but rather a so-called exoskeleton 260. Exoskeleton 260 may also be referred to as a stiffening skeleton or stiffening section. Thus, the terms "exoskeleton," "stiffening skeleton," and "stiffening section" are interchangeable where appropriate.

[0110] The exoskeleton 260 connects the tower sections 220, 222 at the ends of the tower sections 220, 222 opposite the base section 218. In this case, the tower sections 220, 222 and the exoskeleton 260 form a unitary component, in particular a component made of a single piece of material. In particular, the base section 218, the first tower section 220, the second tower section 222, the mechanism 224, and the exoskeleton 260 form a unitary component, in particular a component made of a single piece of material.

[0111] The base portion 218, the two tower portions 220, 222, and the exoskeleton 260 form a frame-type shape that extends all the way around and surrounds or encases the mechanism 224. The mechanism 224 is at least partially disposed within the exoskeleton 260, or the exoskeleton 260 at least partially surrounds the mechanism.

[0112] Exoskeleton 260 has a base portion 262 with an opening 264 through which coupling element 214 passes. Coupling element 214 has sufficient clearance within opening 264 to allow coupling element 214 to be moved by mechanism 224 to adjust its orientation as described above.

[0113] The base portion 262 is connected integrally, in particular in one piece, to the first tower portion 220 by means of a first connection portion 266. Furthermore, the base portion 262 is connected integrally, in particular in one piece, to the second tower portion 222 by means of a second connection portion 268. In this way, the stepped shape of the exoskeleton 260 is obtained.

[0114] A slot or notch 270 is provided between the first connecting portion 266 and the feature 224. Accordingly, a slot or notch 272 is also provided between the second connecting portion 268 and the feature 224. A corresponding slot or notch 274 is also provided between the base portion 262 and the feature 224.

[0115] The bipod 202B design includes an exoskeleton 260 and a base portion 218 that may include mechanisms 224. The exoskeleton 260 and base portion 218 are integrally connected to one another via tower portions 220, 222 to allow for stable attachment points 208, 210 for the bipod 202B.

[0116] Furthermore, the exoskeleton 260 provides additional stiffness. The resulting increased overall width of the exoskeleton 260 allows for lateral auxiliary holes to be provided for the manufacture of radial decoupling joints. Furthermore, the geometry of the decoupling joints can be reproduced on the exoskeleton 260. To meet the required functional precision, the manufacturing of the pockets 230, 232 is adapted based on a one-sided opening.

[0117] While the present invention has been described with reference to exemplary embodiments, various modifications are possible. [Explanation of symbols]

[0118] 1. Projection exposure equipment 2 Beam shaping and illumination system 4. Illumination optical unit 6 light source 8. Radiation 10 Photomask 12 wafers 14 Lens Elements 16 lens elements 18 Lens Elements 20. Mirror 22 Mirror 24 Optical axis 26 Medium 100 Optical system 102 Optical Elements 102' Optical Elements 104 PCB 106 Optically Effective Surface 106' optical effective surface 108 front side 110 Rear side 112 mirror socket 114 mirror socket 116 Mirror Socket 200 Adjustment device 202 Bipod 202A Bipod 202B Bipod 204 Bipod 206 Bipod 208 Connection Points 210 Connection Points 212 Fixed environment 214 Coupling element 214' Coupling element 216 Open-loop and closed-loop control units 218 Base 220 Tower section 222 Tower section 224 Mechanism 226 Actuating element 228 Actuating element 230 pockets 232 Pocket 234 Movement 236 Movement 238 Notch 240 Notch 242 Stiffening element 244 Fastening Point 246 Fastening Point 248 Fastening Point 250 Fastening Points 252 recess 254 Depression 256 Depression 258 Depression 260 Exoskeleton 262 Base 264 Aperture 266 Connection 268 Connection 270 Notch 272 Notch 274 Notch AL starting position EL Ending Posture IL Actual posture M1 mirror M2 mirror M3 mirror M4 mirror M5 mirror M6 mirror SL target posture xx direction yy direction zz direction

Claims

1. A bipod (202, 202A, 202B, 204, 206) for adjusting optical elements (102, 102') of an optical system (100) of a projection exposure apparatus (1), comprising: a mechanism (224) coupleable to the optical element (102, 102') for adjusting the optical element (102, 102'); a base portion (218); a first tower section (220) extending from the base section (218); a second tower portion (222) extending from the base portion (218) in the same manner as the first tower portion (220); the mechanism (224) is disposed between the first tower section (220) and the second tower section (222); The first tower section (220) and the second tower section (222) are connected to each other on the side opposite the base section (218) to increase the rigidity of the bipod (202, 202A, 202B, 204, 206).

2. 2. The bipod according to claim 1, wherein the base portion (218), the first tower portion (220), the second tower portion (222), and the mechanism (224) form a unitary component, in particular a component made of a single material.

3. 3. The bipod according to claim 1, wherein a first notch (238) is provided between the first tower section (220) and the mechanism (224), and a second notch (240) is provided between the second tower section (222) and the mechanism (224).

4. A bipod according to any one of claims 1 to 3, wherein the mechanism (224) has a first pocket (230) for accommodating a first actuating element (226) and a second pocket (232) for accommodating a second actuating element (228), the first pocket and the second pocket (230, 232) being closed at the rear.

5. 5. The bipod according to claim 1, further comprising a stiffening element (242) connecting the first tower portion (220) and the second tower portion (222) on the side opposite the base portion (218).

6. 6. The bipod of claim 5, wherein said stiffening element (242) is connected to said base portion (218).

7. 7. A bipod according to claim 5 or 6, wherein the stiffening element (242) has a recess (252) on the side opposite the bipod (202, 202A, 204, 206).

8. 8. The bipod of claim 7, wherein the recess (252) has a plurality of recesses (254, 256, 258) extending to different depths within the stiffening element (242), such that the recess (252) has a stepped shape.

9. 5. The bipod of claim 1, further comprising an exoskeleton (260) connecting the first tower section (220) and the second tower section (222) on the side opposite the base section (218).

10. 10. The bipod according to claim 9, wherein the first tower section (220), the second tower section (222) and the exoskeleton (260) are connected integrally, in particular by a single material.

11. 11. The bipod of claim 9 or 10, wherein the mechanism (224) is at least partially disposed within the exoskeleton (260).

12. 12. The bipod of claim 9, wherein the base portion (218), the first tower portion (220), the second tower portion (222), and the exoskeleton (260) form a frame-type shape extending around the entire periphery of the mechanism (224).

13. an optical element (102, 102'); At least one bipod (202, 202A, 202B, 204, 206) according to any one of claims 1 to 12; An optical system (100) of a projection exposure apparatus (1), comprising: The optical system wherein the at least one bipod (202, 202A, 202B, 204, 206) is coupled to the optical element (102, 102') using a mechanism (224).

14. 14. The optical system of claim 13, further comprising a first bipod (202, 202A, 202B), a second bipod (204), and a third bipod (206), wherein the optical element (102, 102') is adjustable with six degrees of freedom to move the optical element (102, 102') from an actual attitude (IL) to a target attitude (SL) and vice versa, and each bipod (202, 202A, 202B, 204, 206) is assigned two of the six degrees of freedom.

15. A projection exposure apparatus (1) comprising a bipod (202, 202A, 202B, 204, 206) according to any one of claims 1 to 12 and / or an optical system (100) according to claim 13 or 14.

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