Apparatus, holding device, arrangement, system and method for holding an optical element; lithography system

Abstract

The invention relates to an apparatus (1) for holding an optical element (2), in particular an optical element of a mask inspection system or of a lithography system, comprising a holding point (3) for connection to the optical element (2), a support (4) and a support foot (5). The holding point (3) is connected to the support (4). The support (4) has at least one rod leg (6) and a foot joint device (7), wherein the foot joint device (7) articulatedly connects a lower end (6a) of the rod leg (6) facing away from the holding point (3) to the support foot (5). The invention provides for the foot joint device (7) to have a supporting joint (7a) and a transverse joint (7b), wherein the supporting joint (7a) articulatedly connects the lower end (6a) of the rod leg (6) directly to the support foot (5).

Description

[0001] Apparatus, holding device, arrangement, system and method for holding an optical element; lithography system

[0002] This application claims priority to German Patent Application No. DE 10 2024 209 248.7 filed September 25, 2024, incorporated by reference herein in their entirety to form a part of the present disclosure.

[0003] The invention relates to an apparatus for holding an optical element, in particular an optical element of a mask inspection system or of a lithography system.

[0004] The invention also relates to a holding device for holding an optical element, in particular an optical element of a mask inspection system or of a lithography system.

[0005] The invention also relates to an arrangement for holding an optical element, in particular an optical element of a mask inspection system or of a lithography system.

[0006] The invention furthermore relates to a system comprising an optical element, in particular an optical element of a mask inspection system or of a lithography system.

[0007] The invention moreover relates to a method for holding and in particular for positioning and / or aligning an optical element, in particular an optical element of a mask inspection system or of a lithography system.

[0008] In addition, the invention relates to a mask inspection system for inspecting a photomask, in particular a reticle for a projection exposure apparatus, comprising an illumination device with a radiation source and an optical unit which comprises at least one optical element, and comprising a detection device.

[0009] The invention further relates to a lithography system, in particular a projection exposure apparatus for semiconductor lithography, having an illumination system with a radiation source and an optical unit which comprises at least one optical element.

[0010] Optical elements reguire a suitable holder for fixing or holding or mounting them in an optical system and in order to be able to selectively move and / or tilt them, if appropriate. Already during installation, for example uneven assembly or contact surfaces, manufacturing tolerances, angular or positional errors or differences in thermal expansion between the optical element and its surroundings can have an effect on the holder or the optical element. Differences in thermal expansion between the optical element and its surroundings can, during operation, also be caused by light absorption. If positioning and / or aligning is necessary or desired, use is made of actuators which exert additional forces. During installation, during operation, and when positioning and / or aligning, undesired forces and moments that lead to deformations of the optical element and / or of an optical face of the optical element are also transmitted to the optical element. These deformations can adversely affect the functionality of the optical element, in particular if high precision in the beam path and / or in the beam profile is necessary, such as for an imaging guality which is as high as possible and imaging aberrations that are as small as possible in semiconductor lithography. Both lithography systems per se and mask inspection systems by means of which photomasks or reticles for the lithography systems can be inspected or examined beforehand can benefit from reduced deformations of the optical elements.

[0011] For many applications, in particular in high-performance optics, optical elements should be able to be moved at least in translation in a lateral and axial direction and in rotation about the radial, tangential and axial axes. Deformations of the optical elements or optical faces or optical surfaces can occur in the process. Generally speaking, such deformations are caused by parasitic forces and / or moments or parasitic loads, which arise as an undesired or passive side effect of the envisaged active positioning and / or alignment of the optical element. This is in particular because positioning mechanisms for moving the optical elements are constructed from spring joints, which cause deforming forces, torques and / or bending moments when they move in articulation and thus when the positioning mechanism is moved. Such parasitic loads are at least partially absorbed or taken up by the optical element and can therefore unintentionally change the shape of the optical element.

[0012] Besides the positioning and / or alignment of the optical element, the holder also has a basic holding function. In this respect, also of decisive importance are oscillations, which are generally undesirable and, like deformations of the optical element, should be minimized in order to achieve as good as possible an imaging quality and to prevent optical artefacts.

[0013] A variety of kinematic systems for holding or mounting, positioning and / or aligning optical elements are known from the prior art. Use is often made here of what are known as bipods having two bipod legs.

[0014] According to the general prior art, such bipods can be adjusted for example by actuation of the bipod legs in the longitudinal or axial direction. A displacement of the bipod legs in their longitudinal direction by means of an actuator results in a tangential and / or axial displacement of the optical element. It is usual for the bipod legs to in each case have simple joints, in particular tilting joints or leaf spring joints, at their ends, such that the bipod legs are flexible with respect to translational movements, in particular perpendicularly relative to the bipod leg, and with respect to tilting movements.

[0015] It has proven to be a disadvantage here that parasitic loads, which stem from the elastic properties or the stiffness of the joints, are introduced into the optical element in an unobstructed manner and cause deformations of the optical element. In particular, the restoring forces of the joints of a bipod leg, said joints being able to be bent or deflected for example by the displacement of an adjacent bipod leg in its longitudinal direction, are responsible for this. The parasitic bending moments caused in the process cannot, or at least cannot completely, be absorbed by the displaced, adjacent bipod leg and must instead be supported by the optical element, leading to undesired deformations. Alternatives to the actuation of the bipod legs in the longitudinal direction are also known. DE 10 2018 200 178 A1 discloses a projection exposure apparatus in the case of which, for adjustment of the optical element, a kinematic system in the form of a bipod is disclosed, in the case of which at least one movement component in the transverse direction is provided. In this respect, the actuation can additionally be effected in the direction of a connecting line between the foot points of the two bipod legs or displacements of the bipod leg also in the transverse direction can be made possible using an actuating lever by way of an offset between the foot joint and the joint of the actuating lever. In both cases, parasitic bending moments can be at least partially compensated and undesired deformations of the optical element are avoided as a result. In this way, the optical element does not have to support any, or has to support barely any, radial bending moments.

[0016] However, a disadvantage of the solution according to DE 10 2018 200 178 A1 consists in the indirect transmission or conduction of force, i.e. the tortuous flow of force, with the result that the arrangement is comparatively susceptible to the excitation of oscillations. Furthermore, the force required for adjustment is relatively high as a result.

[0017] The present invention is based on the object of providing an apparatus for holding an optical element, said apparatus being improved over the prior art and in particular reducing undesired deformations of the optical element.

[0018] According to the invention, this object is achieved by an apparatus having the features specified in Claim 1.

[0019] The present invention is also based on the object of providing a holding device for holding an optical element, said holding device being improved over the prior art and in particular reducing undesired deformations of the optical element.

[0020] According to the invention, this object is achieved by a holding device having the features specified in Claim 17.

[0021] The present invention is additionally based on the object of providing an arrangement for holding an optical element, said arrangement being improved over the prior art and in particular reducing undesired deformations of the optical element.

[0022] According to the invention, this object is achieved by an arrangement having the features specified in Claim 23.

[0023] The present invention is furthermore based on the object of providing a system comprising an optical element, said system being improved over the prior art and in particular making it possible to hold the optical element in an improved manner and reducing undesired deformations of the optical element. According to the invention, this object is achieved by a system having the features specified in Claim 25.

[0024] The present invention is moreover based on the object of providing a method for holding and in particular for positioning and / or aligning an optical element, said method being improved over the prior art and in particular reducing undesired deformations of the optical element.

[0025] According to the invention, this object is achieved by a method having the features specified in Claim 27.

[0026] The present invention is additionally based on the object of providing a mask inspection system which comprises optical elements held in a way that avoids the disadvantages of the prior art, in particular in a way that reduces undesired deformations of the optical element.

[0027] According to the invention, this object is achieved by a mask inspection system having the features specified in Claim 28.

[0028] The present invention is further based on the object of providing a lithography system which comprises optical elements held in a way that avoids the disadvantages of the prior art, in particular in a way that reduces undesired deformations of the optical element.

[0029] According to the invention, this object is achieved by a lithography system having the features specified in Claim 29.

[0030] The apparatus according to the invention for holding, or mounting, an optical element, in particular an optical element of a mask inspection system or of a lithography system, has a holding point for connection to the optical element. The apparatus according to the invention also has a support and a support foot, wherein the holding point is connected to the support. The support has at least one rod leg and a foot joint device, wherein the foot joint device articulatedly connects a lower end of the rod leg facing away from the holding point to the support foot. The invention provides for the foot joint device to have a supporting joint and a transverse joint, wherein the supporting joint articulatedly connects the lower end of the rod leg directly to the support foot.

[0031] The apparatus or kinematic system according to the invention is advantageously suitable for holding, or mounting, optical elements with minimal parasitic loads.

[0032] The combination of two joints, i.e. the combination of the supporting joint and of the transverse joint to form a foot joint device, instead of the use of an individual foot joint, also enables transverse displacements of the support in addition to displacements in the longitudinal direction, in order to at least approximately or preferably completely compensate for parasitic bending moments. At the same time, the direct connection of the rod leg to the support foot by the supporting joint allows the optical element to be attached to the holder or the frame or the housing more rigidly than in the prior art. Furthermore, the comparatively direct transmission or conduction of force from the holding point at the optical element to the support foot has proven to be advantageous for avoiding oscillation excitations and resonances. Owing to these various aspects, in the case of the solution according to the invention for holding optical elements, no or barely any deformations of the optical element occur. In the context of mask inspection or lithography systems, this leads to a considerably improved imaging quality, because an optical element held, or mounted, with reduced deformation in this way experiences few or no imaging aberrations caused by external influences.

[0033] The apparatus may in particular also be designed to align and / or position the optical element or move it in a guided manner. For this, the rod legs may for example be movable. The present invention can therefore achieve the object of providing an apparatus for positioning and / or aligning an optical element, the apparatus minimizing undesired deformations of the optical element.

[0034] The advantages of the apparatus according to the invention largely result from the fact that, due to the division of the foot joint or of the foot joint device of the support into a supporting joint and a transverse joint which are preferably movable independently of one another and are oriented differently in space, the apparatus can compensate for parasitic forces and / or moments that would otherwise be taken up by the optical element and deform the latter, by means of counter-bending movements of the supporting joint or transverse joint and / or counter-tilting movements of components of the apparatus, for example of an actuating lever which will be described in more detail below. Counter-tilting movements can be enabled in particular by the deflection of the supporting joint and / or of the transverse joint. It is particularly advantageous for the function of the invention if the supporting joint permits translational movements or transverse movements of the lower end of the rod leg in relation to the support foot which is preferably as stationary as possible, wherein the translational movement can be transmitted to the lower end of the rod leg by means of the transverse joint of an actuator that is preferably used for this.

[0035] Usually, multiple apparatuses according to the invention are used together to hold the optical element. In particular, two apparatuses according to the invention together can form a bipod, or a holding device. The two apparatuses may form the limbs of the bipod. In contrast to the prior art, these do not have a foot joint with a single axis, but rather have a foot joint device composed of at least a supporting joint and a transverse joint with two axes which differ from one another or different orientations. Preferably, use is made of three such bipods, or holding devices, or six individual apparatuses for the positioning and / or alignment of an optical element, in the manner of a hexapod or hexapod arrangement. It is possible to provide in particular multiple holding points, to which the optical element is fixed and which together support the optical element.

[0036] If the apparatuses of a bipod or of a holding device for positioning and / or aligning the optical element are actively brought out of their rest position or selectively adjusted, the apparatuses of another bipod fixed to the optical element, in particular the foot joint devices of said other bipod, can also be passively deflected as a result. The present invention is also suitable for this. The optical element may for example be a mirror or a lens element. However, it may also be any other optical element. The optical element may define and / or have an optical face. The optical face of the optical element may in particular be the surface or mirror face of a mirror or the centre plane of a lens element.

[0037] The holding point at least partially supports the optical element. The optical element is fixed to the holding point. The holding point may in particular be in the form of a holder. The optical element and the apparatus, or the support, can be connected by the holding point. The connection may in particular also be formed by further elements between the support and the holding point. Within the meaning of the invention, the holding point is not necessarily a point in the proper meaning of the word, but rather the holding point can have a certain extent.

[0038] The holding point also defines the point or region at / in which parasitic forces and / or moments are possibly introduced into the optical element.

[0039] The support constitutes a preferably positionally fixed base in order to hold or support the optical element. In addition to the rod leg and the foot joint device, the support of the apparatus may possibly have further elements or components. The support may form a bipod leg or be part of a bipod.

[0040] The rod leg is preferably configured and designed to mainly transmit forces along its longitudinal axis or longitudinal direction. As a rule, the rod leg is elongated. The rod leg may in particular be in the form of a rod or bar. Preferably, the rod leg is rigid or stiff, in particular in the axial direction or longitudinal direction.

[0041] According to the invention, the foot joint device has at least two joints, in particular the supporting joint and the transverse joint. The supporting joint and the transverse joint are preferably oriented or aligned differently. In addition to the supporting joint and the transverse joint, the foot joint device may possibly have further joints.

[0042] The supporting joint can in particular have a supporting function, preferably by the supporting joint connecting the rod leg directly or indirectly to the fixed world. The transverse joint can enable transverse displacements of the rod leg or a transverse displacement of the lower region of the rod leg can be initiated by way of the transverse joint. As a result, parasitic forces and / or moments can be avoided and thus undesired deformations of the optical element can be reduced.

[0043] When using two apparatuses according to the invention together in a bipod or a holding device, provision is preferably made for the supporting joint and / or the transverse joint to be bendable or deflectable at least in a plane spanned by both apparatuses.

[0044] The supporting joint and / or the transverse joint may also have multiple partial joints or joint elements. The joints or partial joints, in particular the supporting joint and / or the transverse joint, may for example be or have flexures, in particular leaf springs. Flexures have, in particular, the advantage of having no or negligible mounting play, and of producing no or little abrasion. However, the joints or partial joints may also be other types of joints, such as wire joints.

[0045] The support foot may be part of a holder or of a frame for the optical element. The support foot may be force-fittingly and / or form-fittingly connected to the holder or to the frame or to respective components thereof. The support foot may also be formed in one piece with the holder or the frame or respective components thereof.

[0046] Preferably, the support foot is arranged at a lower end of the rod leg facing away from the holding point, wherein further elements may be arranged between the support foot and the lower end of the rod leg.

[0047] The support foot is preferably used to connect the apparatus to the fixed world.

[0048] The foot joint device, i.e. at least one element of the foot joint device, articulatedly connects the lower end of the rod leg to the support foot. To this end, provision may be made for the foot joint device to be at least partially arranged between the lower end of the rod leg and the support foot. This means in particular that at least one component, in particular a joint, of the foot joint device is arranged between the lower end of the rod leg and the support foot. In particular, the supporting joint of the foot joint device is arranged between the lower end of the rod leg and the support foot.

[0049] The "direct" connection of the lower end of the rod leg to the support foot by the supporting joint should be understood to mean that, except for the supporting joint, no further element, in particular no lever device such as an actuating lever, is arranged or interposed between the lower end of the rod leg and the support foot. It is a direct connection of the lower end of the rod leg to the support foot by means of the supporting joint, which for this purpose functions in particular as a connecting piece.

[0050] This direct connection of the rod leg to the support foot at least partially enables direct dissipation of forces, which act at the holding point, via the rod leg and the supporting joint to the support foot. This achieves a more rigid attachment of the optical element to the surroundings, in order to inter alia avoid oscillation excitation.

[0051] It has proven to be particularly suitable if the supporting joint and the transverse joint are aligned at least approximately at a right angle to one another in a rest position of the apparatus.

[0052] This further reduces the forces required for the adjustment of the rod leg.

[0053] In other words, the supporting joint and the transverse joint are preferably oriented or aligned relative to one another in such a way that the supporting joint and the transverse joint are perpendicular to one another. An approximately right angle may in particular be an angle between 80° and 100°, preferably an angle between 85° and 95°, more preferably an angle between 88° and 92°, particularly preferably an angle of 90°.

[0054] If the optical element or the optical face of the optical element is oriented at least approximately horizontally and the apparatus is in the rest position, the supporting joint of the foot joint device preferably runs at least approximately vertically and the transverse joint of the foot joint device runs at least approximately horizontally. In general, neither the supporting joint nor the transverse joint run in the extension of the rod leg. However, the invention is not restricted to the horizontal orientation of the optical element, nor to a vertical alignment of the supporting joint and / or a horizontal alignment of the transverse joint.

[0055] The rest position or basic position of the apparatus corresponds to a state in which the apparatus, in particular the foot joint device, or the supporting joint and / or the transverse joint, is not deflected, i.e. at least approximately no restoring forces of the foot joint device, or of the supporting joint and / or of the transverse joint, act. In such a state, provision is made for the supporting joint and the transverse joint to preferably be oriented at least approximately at a right angle, or a 90° angle, relative to one another. This is in particular independent of how the optical element itself is oriented in space, whether it is for example vertical or pendant or whether it has an oblique orientation in space.

[0056] Provision may preferably be made in the rest position of the apparatus for the supporting joint to run or be aligned at least approximately perpendicularly, or at a right angle, relative to the optical element or the optical face, and / or for the transverse joint to run or be aligned at least approximately parallel to the optical element or the optical face.

[0057] Within the context of this invention, the alignment of a joint, for example of the supporting joint and of the transverse joint, can be understood to mean the axis through the joint in its rest position. In the example of a joint in the form of a leaf spring, the axis corresponds to the straight connecting lines between the two ends of the leaf spring or to the orientation of the leaf spring in its relaxed or non-deflected state.

[0058] The deflection of a joint causes restoring forces. If a joint is not deflected or no restoring forces act, the joint is in the rest position. The rest position of the apparatus in particular requires that both the supporting joint and the transverse joint are in their respective rest position.

[0059] Within the context of this invention, the deflection of a joint, for example of the supporting joint or of the transverse joint, can be understood to mean, for example, a tilting or bending of the joint. The joint may in particular be deflected perpendicularly relative to the axis of the joint. A virtual point of intersection between the imaginary extensions of the supporting joint and of the transverse joint can be interpreted as a virtual pivot point of the foot joint device, as explained in more detail below. Depending on the construction of the joint, the deflection of the joint leads to one or more restoring forces, which act to bring the joint back into its starting position or rest position. The restoring force counteracts the deflection. The deflection ofthe joint may in particular lead to multiple restoring forces if the joint has multiple partial joints and a plurality of the partial joints are deflected when the joint is deflected.

[0060] A deflection of the foot joint device, or of the supporting joint and / or of the transverse joint, out of its respective rest position can also bring the rod leg out of its rest position, for example the rod leg may be displaced and / or tilted. The deflection of the foot joint device, or of the supporting joint and / or of the transverse joint, may also be the consequence of a deflection, displacement and / or tilting of the rod leg.

[0061] The foot joint device, the supporting joint and / or the transverse joint or the rod leg may in particular be deflected, displaced and / or tilted by a selective or guided movement of the optical element with respect to its positioning and / or alignment. This may be effected, for example, by means of actuators.

[0062] Provision may preferably be made for the rod leg to be tiltable about a virtual point of intersection of imaginary extensions, in a rest position of the apparatus, of an axis of the supporting joint and of an axis of the transverse joint.

[0063] The virtual point of intersection may in particular be interpreted as a virtual pivot point or centre of rotation or momentary centre of rotation of the rod leg. The movability necessary for this is made possible by the foot joint device.

[0064] Of particular advantage is a refinement of the invention in which an actuating lever is provided, wherein the lower end of the rod leg is operatively connected to the support foot by way of the actuating lever, and wherein the transverse joint articulatedly connects the lower end of the rod leg to the actuating lever.

[0065] The actuating lever may preferably be in the form of a lever or lever arm or lever device.

[0066] Preferably, the transverse joint engages with a short side facing towards the support or an end side of the actuating lever, or is preferably fixed thereto. As an alternative or in addition, the transverse joint and the actuating lever preferably run parallel to one another in the rest position of the apparatus or in their respective rest position.

[0067] The actuating lever and the support foot may also be articulatedly connected, preferably on a short side or an end side of the actuating lever that lies opposite the side with the transverse joint.

[0068] Preferably, the supporting joint, the transverse joint and the actuating lever are arranged and designed in such a way that the actuating lever is tiltable relative to a rest position of the apparatus so as to, when the holding point is moved by actuation of the actuating lever, reduce deformations of the optical element by interaction of the supporting joint, the transverse joint and the actuating lever, in order to counteract a tilting of the holding point relative to the optical element.

[0069] When the holding point is displaced for positioning the optical element, the supporting joint, the transverse joint and the actuating lever can in each case execute counter-tilting movements or counter-bending movements and in interaction reduce, preferably at least approximately compensate for, parasitic loads, in particular parasitic bending moments. In conjunction with the transverse joint and supporting joint, the actuating lever can thus contribute to the avoidance of undesired deformations of the optical element by minimizing parasitic forces and moments acting on the optical element.

[0070] The use of an actuating lever, which has a certain reduction ratio, can reduce the force required for an adjustment of the apparatus or of the optical element or for a movement of the support without any change in effect. In addition, the accuracy of the adjustability, which is limited in particular by the resolution or increment of an actuator used for the adjustment, can be improved, in particular refined, by means of the actuating lever.

[0071] A reduction ratio of 5:1 to 30:1 , preferably of 10:1 to 20:1 , has proven to be particularly suitable. The reduction ratio may thus, for example, be 12:1 , 15:1 or 20:1 , but the reduction ratio can also assume other values.

[0072] The side lengths of the actuating lever result from the desired reduction ratio, which can in turn be dependent on the weight of the optical element to be adjusted and / or on the strength and the resolution of an actuator used for this.

[0073] To perform the lever function, it is advantageous if the actuating lever is considerably longer in one spatial direction than in a spatial direction orthogonal thereto. If the short side measures, for example, 2 mm, the length of the long side may, for example, be around 30 mm.

[0074] It may be advantageous if the actuating lever is as stiff or rigid as possible, in particular in the direction of its longer side.

[0075] It has proven to be advantageous if the support can be moved by an actuator, which is preferably fixed to the support foot, for selective positioning and / or alignment of the optical element.

[0076] This also advantageously makes the apparatus suitable for positioning and / or aligning optical elements, or moving them in a guided manner, with minimal parasitic loads.

[0077] The actuator may also be formed in one piece with the support foot. The actuator is preferably designed to move or displace the support, in particular by virtue of the actuator acting indirectly, inter alia by way of the actuating lever, on the lower end of the rod leg. With further preference, the actuator can be moved or displaced in multiple spatial directions, particularly preferably in any desired directions.

[0078] The actuator is preferably operatively connected to the lower end of the rod leg.

[0079] Preferably, an actuator joint is provided in order to articulatedly connect the actuating lever to the actuator.

[0080] Preferably, the actuator joint engages with a short side facing towards the actuator or an end side of the actuating lever that lies opposite the side with the transverse joint, or is preferably fixed thereto.

[0081] The lower end of the rod leg may preferably be connected to the support foot by way of the transverse joint, the actuating lever, the actuator joint and the actuator.

[0082] The actuator joint and the transverse joint may preferably run orthogonal to one another in the rest position of the apparatus or in their respective rest position.

[0083] When using two apparatuses according to the invention together in a bipod or a holding device, provision is preferably made for the actuator joint to be bendable or deflectable at least in a plane spanned by both apparatuses.

[0084] It has proven to be particularly suitable if the actuator is adjustable at least approximately parallel to the supporting joint in relation to a rest position of the apparatus, wherein the actuator is movably connected to the lower end of the rod leg by way of the actuating lever in such a way that extension and retraction of the actuator makes it possible to displace the lower end of the rod leg at least approximately parallel to the transverse joint in relation to the rest position.

[0085] It should be noted that the supporting joint and the transverse joint do not actually have to be in the rest position during the extension and retraction of the actuator. The adjustment path of the actuator is in particular at least approximately parallel to the imaginary rest position of the supporting joint, i.e. to an imaginary axis that the supporting joint would occupy if the apparatus were in the rest position. The displacement path of the lower end of the rod leg is in particular at least approximately parallel to the imaginary rest position ofthe transverse joint, i.e. to an imaginary axis that the transverse joint would occupy if the apparatus were in the rest position. During the adjustment of the actuator, the supporting joint and / or the transverse joint are generally deflected, i.e. the apparatus is not in the rest position.

[0086] If the optical element or the optical face is oriented horizontally, provision may in particular be made for the actuator to be adjustable in an at least approximately vertical direction, the extension and retraction of the actuator making it possible to displace the lower end of the rod leg in an at least approximately horizontal direction.

[0087] During the adjustment of the actuator, the actuating lever, which is preferably connected to the actuator by way of the actuator joint, can tilt. As a result, a translational and transverse movement of the lower end of the rod leg relative to the support foot is induced, wherein a displacement component in the transverse direction and a displacement component in the longitudinal direction of the rod leg can result for the lower end of the rod leg. The induced transverse movement of the lower end of the rod leg may preferably be at least approximately parallel to the optical element. If the optical element is oriented or aligned horizontally, the lower end of the rod leg may in particular be displaced horizontally.

[0088] The bending moment produced by the transverse movement may at least partially, preferably at least approximately, compensate for the bending moment of a passively deformed rod leg of another apparatus fixed to the optical element, with the result that the optical element experiences no or few deformations due to parasitic bending moments.

[0089] Preferably, a lever joint is provided in order to articulatedly connect the actuating lever to the support foot.

[0090] Preferably, the lever joint engages with the short side facing towards the support or the end side of the actuating lever, in particular the side to which the transverse joint is also fixed, or is preferably fixed thereto.

[0091] The lever joint and the transverse joint may preferably run approximately parallel to one another in the rest position of the apparatus or in their respective rest position.

[0092] When using two apparatuses according to the invention together in a bipod or a holding device, provision is preferably made for the lever joint to be bendable or deflectable at least in a plane spanned by both apparatuses.

[0093] It may be advantageous if the actuating lever is at least partially arranged between the foot joint device and the actuator, wherein the actuating lever is articulatedly connected to the lower end of the rod leg by way of the transverse joint, to the support foot by way of the lever joint and / or to the actuator by way of the actuator joint.

[0094] The supporting joint connects the lower end of the rod leg to a first connecting point of the support foot, said first connecting point lying on a notionally extended axis of the supporting joint, in relation to the rest position of the apparatus or of the supporting joint. By contrast, the transverse joint connects the lower end of the supporting leg to a second connecting point by way of the actuating lever, the actuator joint and the actuator and to a third connecting point of the support foot by way of the actuating lever and the lever joint, neither of said second and third connecting points lying on a notionally extended axis of the transverse joint, in relation to the rest position of the apparatus or of the transverse joint. It may be advantageous if the rod legs are rigid, in particular in the axial direction.

[0095] The rod legs are at least partially rigid, or rigid at least in certain portions.

[0096] The rod legs may for example consist of steel, in particular corrosion-resistant or stainless steel, other metals or ceramics.

[0097] It may be advantageous if the cross section of the rod legs is round, square or rectangular.

[0098] This yields a high stiffness in the rod direction or in the longitudinal direction of the apparatus, which has an advantageous effect on the holding properties of the apparatus.

[0099] It may also be advantageous if the rod legs are flexible, in particular in the radial, or transverse, direction.

[0100] The rod legs are at least partially flexible, or flexible at least in certain portions.

[0101] In particular, it may also be advantageous if some portions of the rod legs are rigid and others are flexible. In particular, the flexible portions can establish a movability similar to a joint device.

[0102] In a preferred refinement, the rod legs are between 50 mm and 300 mm, particularly preferably between 100 mm and 150 mm long.

[0103] Provision may be made for the supporting joint, the transverse joint, the lever joint and / or the actuator joint to be in the form of a wire joint and / or to have at least one wire joint.

[0104] Provision may preferably be made for the supporting joint, the transverse joint, the lever joint and / or the actuator joint to be in the form of a leaf spring joint and / or to have at least one leaf spring joint.

[0105] It has proven to be advantageous if the supporting joint, the transverse joint, the lever joint and / or the actuator joint has at least two joint elements which are axially offset relative to one another and oriented rotated by 90° relative to one another.

[0106] Provision may in particular be made for the joint elements to have a common axis. The joint elements may preferably be arranged in two adjacent planes of their common axis which are axially offset relative to one another.

[0107] In a development of the invention, a head joint device may be provided, wherein the head joint device is arranged between the holding point and an upper end of the rod leg facing towards the holding point. The head joint device can connect the support to the holding point.

[0108] The head joint device also preferably makes the apparatus tiltable at the holding point.

[0109] It has proven to be particularly suitable if the head joint device is arranged directly at the holding point. In particular, the head joint device can preferably be arranged as close as possible to the holding point, so no other elements lie in between.

[0110] The foot joint device, the supporting joint, the transverse joint, the lever joint, the actuator joint and / or the head joint device may in each case have at least one joint or joint element.

[0111] Preferably, the at least one joint element is a leaf spring or a leaf spring joint.

[0112] The advantages of leaf spring joints consist in a comparatively high stiffness along the joint axis, the absence of mounting play and a negligibly low movement hysteresis in the region of the elastic deformation. However, the joint element may also be a wire joint or another type of joint. A wire joint can be advantageous for flexibility about multiple axes at the same time.

[0113] Preferably, the foot joint device, the supporting joint, the transverse joint, the lever joint, the actuator joint and / or the head joint device may have a plurality of joint elements, wherein the joint elements are preferably each in the form of leaf springs.

[0114] As viewed in the direction of the axis of the respective joint, the joint elements may be located in various planes. The joint elements may in particular be arranged and designed in such a way that the joint element or the joint elements located in a first plane enable a deflection in a first direction and the joint element or the joint elements located in a second plane enable a deflection in a second direction orthogonal thereto, the two directions running in a surface area and the surface area, or plane, preferably running orthogonally to the axis of the joint. Joint elements in the same plane are preferably uniformly oriented, or not rotated relative to one another. Respective intermediate elements may be provided between the planes.

[0115] The joints with the plurality of joint elements may be formed at least partially monolithically or in one piece, possibly also monolithically or in one piece with the rod leg.

[0116] Further preferred refinements and possible uses of the apparatus according to the invention will become apparent from the description below of further subjects of the invention.

[0117] The present invention also relates to a holding device for holding an optical element, in particular an optical element of a mask inspection system or of a lithography system, at least comprising a first apparatus according to the invention and a second apparatus according to the invention, the first apparatus and the second apparatus converging towards one another in the direction of a common holding point at the optical element.

[0118] The holding device may in particular also be a bipod or referred to as a bipod.

[0119] The first apparatus and the second apparatus are in particular apparatuses having one or more features according to the description above. The advantages similarly arise from the already described advantages.

[0120] Provision is in particular made for the first and the second apparatus to each have a foot joint device having a supporting joint and a transverse joint, the respective supporting joint articulatedly connecting a lower end of a respective rod leg directly to the support foot.

[0121] It has proven to be advantageous if the respective connection of the lower end of the rod leg to the support foot is articulated at least in a plane spanned by both apparatuses, i.e. that the supporting joint is preferably bendable or deflectable at least in this plane.

[0122] The first apparatus and the second apparatus converge towards one another in particular in a V shape, at an angle, in the direction of the optical element.

[0123] At the level of the common holding point, a distance may remain between the first apparatus and the second apparatus, or virtual extensions of the first apparatus and of the second apparatus. The common holding point may in particular be in the form of a common holder, or holding device.

[0124] It may be advantageous if the first apparatus and the second apparatus at least approximately form a right angle with one another.

[0125] The first apparatus and the second apparatus are in particular arranged at an at least approximately right angle to one another. Preferably, the longitudinal axes of the respective rod legs of the two apparatuses are at an at least approximately right angle to one another.

[0126] This ensures the highest possible stability of the holding device, or of the bipod. Moreover, the right angle means that feedback between the apparatuses during a movement, for example during a displacement actively performed by an actuator, of at least one of the two apparatuses is avoided.

[0127] An approximately right angle may in particular be an angle between 80° and 100°, preferably an angle between 85° and 95°, more preferably an angle between 88° and 92°, particularly preferably an angle of exactly 90°. The plane, formed by the V shape of the first apparatus and the second apparatus converging towards one another at an angle, of the holding device is preferably perpendicular to the optical element, or the optical face of the optical element. The plane of the holding device may, however, also be aligned differently.

[0128] It has proven to be advantageous if an actuating lever of the first apparatus and an actuating lever of the second apparatus are provided, wherein the supporting joint of the first apparatus, the supporting joint of the second apparatus, the transverse joint of the first apparatus, the transverse joint of the second apparatus, the actuating lever of the first apparatus and the actuating lever of the second apparatus are arranged and designed in such a way that the actuating lever of the first apparatus and, respectively, of the second apparatus is tiltable relative to a respective rest position of the first apparatus and of the second apparatus so as to reduce deformations of the optical element by interaction of the supporting joints, the transverse joints and the actuating levers, in order to counteract a tilting of the holding point relative to the optical element when the holding point is moved by actuation of one or both actuating levers.

[0129] For the respective apparatus, provision is preferably made for the lower end of the rod leg to be operatively connected to the support foot by way of the actuating lever, wherein the transverse joint articulatedly connects the lower end of the rod leg to the actuating lever.

[0130] It has proven to be advantageous if the respective connection of the lower end of the rod leg to the actuating lever is articulated at least in a plane spanned by both apparatuses, i.e. that the transverse joint is preferably bendable or deflectable at least in this plane.

[0131] The actuating lever of the first and, respectively, second apparatus may preferably be in the form of a lever or lever arm or lever device. It may be advantageous if the respective actuating lever is as stiff or rigid as possible, in particular in the direction of a longer side of the actuating lever. To perform the lever function, the respective actuating lever preferably has a transmission ratio, or in the present case preferably a reduction ratio (larger movement at the lever input and smaller movement at the lever output).

[0132] In an advantageous further development of the invention, it may be provided that, for selective positioning and / or alignment of the optical element, an actuator of the first apparatus is arranged and designed in such a way as to move a support of the first apparatus, and / or, for selective positioning and / or alignment of the optical element, an actuator of the second apparatus is arranged and designed in such a way as to move a support of the second apparatus.

[0133] In this further development, at least one of the two apparatuses has an actuator. In particular, the first apparatus and / or the second apparatus may have an actuator. Preferably, both the first support and the second support are movable or displaceable.

[0134] Preferably, the actuator of the first apparatus and / or the actuator of the second apparatus is adjustable at least approximately parallel to the respective supporting joint in relation to a rest position of the respective apparatus, wherein the actuator of the respective apparatus is movably connected to the lower end of the respective rod leg in such a way that extension and retraction of the respective actuator makes it possible to displace the lower end of the respective rod leg at least approximately parallel to the respective transverse joint in relation to the rest position.

[0135] The actuator may preferably be articulatedly connected to the lower end of the rod leg by way of the actuating lever and an actuator joint of the respective apparatus.

[0136] It has proven to be advantageous if the respective connection of the lower end of the rod leg to the actuator is articulated at least in a plane spanned by both apparatuses, i.e. that the actuator joint is preferably bendable or deflectable at least in this plane.

[0137] Furthermore, the lower end of the rod leg of the first and, respectively, second apparatus may preferably be connected to the support foot by way of the transverse joint, the actuating lever, the actuator joint and the actuator.

[0138] Preferably, the actuating lever of the respective apparatus is articulatedly connected to the support foot by way of a lever joint.

[0139] It has proven to be advantageous if the respective connection of the actuating lever to the support foot is articulated at least in a plane spanned by both apparatuses, i.e. that the lever joint is preferably bendable or deflectable at least in this plane.

[0140] Provision may be made for a support foot of the first apparatus to be formed in one piece with a support foot of the second apparatus.

[0141] In other words, the respective support foot of the first and of the second apparatus may be part of a common foot or of a common holder or of a common frame. Instead of being connected by the common support foot, it is alternatively possible for the respective lower end of the rod legs, or the elements fixed thereto, to be connected by a common contact surface in the surroundings, or in each case directly to the fixed world.

[0142] The present invention also relates to an arrangement for holding an optical element, in particular an optical element of a mask inspection system or of a lithography system, at least comprising six apparatuses according to the invention or three holding devices according to the invention.

[0143] The arrangement according to the invention may in particular also be suitable for positioning and / or aligning the optical element. The apparatuses or the holding devices are in particular apparatuses or holding devices having one or more features according to the description above. The advantages similarly arise from the already described advantages.

[0144] Preferably, the arrangement has exactly six apparatuses according to the invention or exactly three holding devices according to the invention. Generally speaking, therefore, in particular all the degrees of freedom for positioning and / or aligning an optical element are sufficiently determined, if this is intended in addition to the holding function.

[0145] Mixtures of apparatuses and holding devices, in particular such that overall preferably exactly six apparatuses are present, it also being possible for two respective apparatuses to form a holding device, are possible.

[0146] According to the invention, it may in particular also be provided that the arrangement has for example four apparatuses according to the invention and a holding device according to the invention, with the holding device comprising two of the overall six apparatuses provided. Further combinations are similarly possible.

[0147] It should be noted that, if there are more than six apparatuses, it is also possible for the apparatuses to form more than three holding devices.

[0148] The combination of at least six apparatuses, or three holding devices, ensures a stable support for the optical element and at the same time the exploitation of the degrees of freedom for optionally positioning and / or aligning the optical element. The combination of exactly six apparatuses, or exactly three holding devices, to form a hexapod has proven to be particularly advantageous.

[0149] It may be advantageous if the apparatuses and / or the holding devices are at least approximately uniformly distributed around an outer peripheral region of the optical element. This increases the stability of the arrangement.

[0150] The apparatuses and / or the holding devices are to be regarded as at least approximately uniformly distributed around the outer peripheral region of the optical element in particular also if the respective position of the apparatuses and / or of the holding devices deviates from the position thereof in a completely uniform distribution by no more than 10%, preferably no more than 5%, more preferably no more than 2%.

[0151] The holding devices may in particular be aligned such that the V-shaped plane formed respectively by the first apparatus and the second apparatus, which converge towards one another at an angle, is tangential to a periphery of the optical element. The planes of the holding devices may, however, also be aligned differently. The present invention furthermore relates to a system comprising an optical element, in particular an optical element of a mask inspection system or of a lithography system, and at least comprising six apparatuses according to the invention orthree holding devices according to the invention for holding the optical element.

[0152] The positioning and / or alignment of the optical element may in particular also be provided.

[0153] The apparatuses or the holding devices are in particular apparatuses or holding devices having one or more features according to the description above. The advantages similarly arise from the already described advantages.

[0154] The number and the arrangement of the apparatuses according to the invention or of the holding devices according to the invention within the context of the system can be selected preferably as was already described with regard to the arrangement according to the invention. It may in particular be suitable if the system according to the invention comprises six apparatuses or three holding devices. Two respective apparatuses may possibly also form a holding device.

[0155] It may be provided that the optical element is a mirror or a lens element. In particular, it can be a mirror or a lens element of a lithography system.

[0156] The present invention also relates to a method for holding and in particular for positioning and / or aligning an optical element, in particular an optical element of a mask inspection system or of a lithography system, wherein the optical element is held and in particular positioned and / or aligned by means of at least one apparatus according to the invention and / or one holding device according to the invention or an arrangement according to the invention.

[0157] The apparatuses or the holding devices or the arrangement are in particular apparatuses or holding devices or an arrangement having one or more features according to the description above. The advantages similarly arise from the already described advantages.

[0158] The present invention additionally relates to a mask inspection system for inspecting a photomask, in particular a reticle for a projection exposure apparatus, comprising an illumination device with a radiation source and an optical unit which comprises at least one optical element, and comprising a detection device, wherein the optical element is held by at least one apparatus according to the invention and / or one holding device according to the invention or an arrangement according to the invention.

[0159] The at least one optical element can in particular also be positioned and / or aligned by at least one apparatus according to the invention and / or one holding device according to the invention or an arrangement according to the invention. The apparatuses or the holding devices or the arrangement are in particular apparatuses or holding devices or an arrangement having one or more features according to the description above. The advantages similarly arise from the already described advantages.

[0160] The mask inspection system can in particular be used to inspect or measure photomasks or reticles prior to their intended use or prior to their integration in an optical system, in particular a lithography system, in particular to verify the imaging quality. This may possibly be an integral part of the production process for the photomasks and preferably contribute to quality assurance.

[0161] Photomasks are projection templates which are used for photolithographic structuring in the production of semiconductor components by only determined regions of a photoresist or resist which is applied to the substrate or wafer to be structured being specifically exposed. Photomasks are similarly also referred to as "reticles".

[0162] Lithography systems, as described in more detail below, can in particular be projection exposure apparatuses for semiconductor lithography using EUV (extreme ultraviolet) light and / or DUV (deep ultraviolet) light. In a particularly preferred refinement, the lithography system may be an EUV projection exposure apparatus, the reticle to be inspected preferably being in the form of an EUV mask. However, the mask inspection system according to the invention is not restricted to use in EUV lithography. It can in particular also be suitable for other photomasks that are not EUV masks.

[0163] EUV masks are in particular matched to an operating wavelength in the EUV range, preferably to an operating wavelength of 5 nm to 30 nm, more preferably of 10 nm to 15 nm, particularly preferably of 13.5 nm. Generally speaking, these are reflective photomasks which function as interference mirrors by means of multilayer layer arrangements or multilayer coatings.

[0164] Photomasks have to be produced with high accuracy, since for instance within the context of EUV lithography mask errors in an order of magnitude of 1 nm can already lead to considerable losses in imaging quality and thus in the quality of the structures produced. Thus, to check the photomasks, use is usually made of mask inspection systems in order to locate and possibly identify mask errors in the relevant order of magnitude. An exemplary mask inspection system for EUV masks, and also a mask inspection method, is known from the applicant’s document DE 10 2012 213 794 A1 .

[0165] In orderto ensure a high measurement accuracy of the mask inspection system, it is advantageous if optical elements of the mask inspection system are held, and possibly positioned and / or aligned, in as stable or wobble-free a manner as possible, wherein in particular deformations of the optical elements can be avoided. This can be particularly advantageously achieved by the mask inspection system according to the invention. The illumination device of the mask inspection system is used to illuminate the photomask to be inspected with measurement radiation, the detection device detecting the pattern produced by the illuminated photomask.

[0166] The wavelength of the measurement radiation emitted by the radiation source of the illumination device preferably corresponds to the operating wavelength of the lithography system for which the photomask to be inspected is intended. The optical unit of the illumination device comprises the at least one optical element which is held in the manner according to the invention. By means of the optical unit, the measurement radiation can be guided for example over a determined beam path and shaped in a desired manner, for example focused.

[0167] Preferably, in addition to the illumination device and the detection device, the mask inspection system comprises a magnification device for magnified imaging of the pattern produced by the photomask, a maskholding device for holding the photomask and / or an evaluation device.

[0168] The present invention further relates to a lithography system, in particular a projection exposure apparatus for semiconductor lithography, comprising an illumination system with a radiation source and an optical unit which comprises at least one optical element, wherein the optical element is held by at least one apparatus according to the invention and / or one holding device according to the invention or an arrangement according to the invention.

[0169] The optical element can in particular also be positioned and / or aligned by at least one apparatus according to the invention and / or one holding device according to the invention or an arrangement according to the invention.

[0170] The apparatuses or the holding devices or the arrangement are in particular apparatuses or holding devices or an arrangement having one or more features according to the description above. The advantages similarly arise from the already described advantages.

[0171] Lithography systems can in particular be projection exposure apparatuses for semiconductor lithography using EUV (extreme ultraviolet) light and / or DUV (deep ultraviolet) light.

[0172] In these and adjacent fields of application, stable or wobble-free holding, and possibly stable or wobble- free positioning and exact alignment of optical elements and the simultaneous avoidance of deformations of the optical elements is particularly important, in order to achieve a high imaging quality without imaging aberrations and thus be able to produce high-quality structures, in particular semiconductor structures.

[0173] Furthermore, it may be advantageous if, prior to use or integration in the lithography system, a reticle or a photomask of the lithography system has been inspected or examined or measured with regard to quality and imaging properties by means of a mask inspection system according to the invention. Similarly to the mask inspection system according to the invention and the lithography system according to the invention, the apparatus according to the invention, the holding device according to the invention, the arrangement according to the invention, the system according to the invention and the method according to the invention can be employed within the context of other optical systems in a likewise advantageous manner. This applies in particular to all optical systems with high precision requirements.

[0174] Features described in conjunction with one of the subjects of the invention, specifically given by the apparatus according to the invention, the holding device according to the invention, the arrangement according to the invention, the system according to the invention, the method according to the invention, the mask inspection system according to the invention or the lithography system according to the invention, can also advantageously be implemented for the other subjects of the invention. Likewise, advantages specified in conjunction with one of the subjects of the invention can also be understood in relation to the other subjects of the invention.

[0175] Additionally, it should be noted that terms such as "comprising", "having", or "with" do not exclude other features or steps. Furthermore, terms such as "a(n)" or "the" which indicate single steps or features do not exclude a plurality of features or steps - and vice versa.

[0176] However, in a puristic embodiment of the invention, provision may also be made for the features introduced in the invention using the terms "comprising", "having", or "with" to be an exhaustive enumeration. Accordingly, one or more enumerations of features can be considered to be exhaustive within the context of the invention, for example respectively considered for each claim. For example, the invention can consist exclusively of the features specified in Claim 1.

[0177] It should be noted that designations such as "first" or "second", etc. are used predominantly to be able to distinguish between respective apparatus or method features and are not necessarily intended to indicate that features require one another or are related to one another.

[0178] Exemplary embodiments of the invention will be described in more detail below with reference to the drawing.

[0179] The figures each show preferred exemplary embodiments in which individual features of the present invention are illustrated in combination with one another. Features of an exemplary embodiment are also implementable independently of the other features of the same exemplary embodiment, and may readily be combined accordingly by a person skilled in the art to form further viable combinations and subcombinations with features of other exemplary embodiments.

[0180] In the figures, functionally identical elements are given the same reference signs. In the figures:

[0181] Figure 1 shows a meridional section of an EUV projection exposure apparatus;

[0182] Figure 2 shows a DUV projection exposure apparatus;

[0183] Figure 3 shows a basic illustration of one embodiment of the apparatus according to the invention and of the holding device according to the invention for holding an optical element in the rest position;

[0184] Figure 4 shows a further basic illustration according to Figure 3 in the case of active deflection;

[0185] Figure 5 shows a further basic illustration according to Figure 3 in the case of passive deflection;

[0186] Figure 6 shows a basic view of an exemplary joint having two joint elements; and

[0187] Figure 7 shows a basic illustration of one embodiment of the arrangement according to the invention and of the system according to the invention for holding an optical element.

[0188] With reference to Figure 1 , the essential component parts of a microlithographic EUV projection exposure apparatus 100 as an example of a lithography system are initially described below in exemplary fashion. The description of the basic construction of the EUV projection exposure apparatus 100 and of the component parts thereof should not be interpreted restrictively here.

[0189] An illumination system 101 of the EUV projection exposure apparatus 100 comprises, besides a radiation source 102, an illumination optical unit 103 for the illumination of an object field 104 in an object plane 105. What is exposed here is a reticle 106 arranged in the object field 104. The reticle 106 is held by a reticle holder 107. The reticle holder 107 is displaceable in particular in a scanning direction by way of a reticle displacement drive 108.

[0190] Figure 1 depicts a Cartesian xyz-coordinate system for illustrative purposes. The x-direction runs perpendicularly into the plane of the drawing. The y-direction runs horizontally, and the z-direction runs vertically. In Figure 1 , the scanning direction runs in the y-direction. The z-direction runs perpendicularly to the object plane 105.

[0191] The EUV projection exposure apparatus 100 comprises a projection optical unit 109. The projection optical unit 109 serves for imaging the object field 104 into an image field 110 in an image plane 11 1. The image plane 111 runs parallel to the object plane 105. Alternatively, an angle between the object plane 105 and the image plane 111 that differs from 0° is also possible. A structure on the reticle 106 is imaged onto a light-sensitive layer of a wafer 112 arranged in the region of the image field 110 in the image plane 111. The wafer 112 is held by a wafer holder 113. The wafer holder 113 is displaceable in particular in the y-direction by way of a wafer displacement drive 114. The displacement, firstly, of the reticle 106 by way of the reticle displacement drive 108 and, secondly, of the wafer 1 12 by way of the wafer displacement drive 114 may be synchronized with one another.

[0192] The radiation source 102 is an EUV radiation source. The radiation source 102 emits in particular EUV radiation 115, which in the following text is also referred to as used radiation or illumination radiation. The used radiation 1 15 has in particular a wavelength in the range between 5 nm and 30 nm. The radiation source 102 can be a plasma source, for example an LPP source ("laser produced plasma") or a GDPP source ("gas discharge produced plasma"). It may also be a synchrotron-based radiation source. The radiation source 102 can be a free electron laser (FEL).

[0193] The illumination radiation 1 15 emanating from the radiation source 102 is focused by a collector 116. The collector 116 can be a collector with one or more ellipsoidal and / or hyperboloidal reflection surfaces. The at least one reflection surface of the collector 116 can be impinged upon by the illumination radiation 115 with grazing incidence (Gl), i.e. with angles of incidence greater than 45°, or with normal incidence (Nl), i.e. with angles of incidence less than 45°. The collector 116 can be structured and / or coated, firstly to optimize its reflectivity for the used radiation 115 and secondly to suppress extraneous light.

[0194] Downstream of the collector 116, the illumination radiation 115 propagates through an intermediate focus in an intermediate focal plane 117. The intermediate focal plane 117 can constitute a separation between a radiation source module, comprising the radiation source 102 and the collector 116, and the illumination optical unit 103.

[0195] The illumination optical unit 103 comprises a deflection mirror 118 and, disposed downstream thereof in the beam path, a first facet mirror 119. The deflection mirror 118 may be a planar deflection mirror or, alternatively, a mirror with a beam-influencing effect that goes beyond the pure deflection effect. As an alternative or in addition, the deflection mirror 118 may be in the form of a spectral filter that separates a used light wavelength of the illumination radiation 115 from extraneous light of a wavelength differing therefrom. If the first facet mirror 119 is arranged in a plane of the illumination optical unit 103 which is optically conjugate to the object plane 105 as a field plane, it is also referred to as a field facet mirror. The first facet mirror 119 comprises a multiplicity of individual first facets 120, which are also referred to below as field facets. Only a few of these facets 120 are illustrated in Figure 1 by way of example.

[0196] The first facets 120 may be in the form of macroscopic facets, in particular rectangular facets or facets with an arc-shaped edge contour or part-circle-shaped edge contour. The first facets 120 may be in the form of planar facets or, alternatively, of convexly or concavely curved facets. As is known for example from DE 10 2008 009 600 A1 , the first facets 120 themselves can also be composed in each case of a multiplicity of individual mirrors, in particular a multiplicity of micromirrors. The first facet mirror 119 may be in the form of a microelectromechanical system (MEMS system) in particular. For details, reference is made to DE 10 2008 009 600 A1 .

[0197] The illumination radiation 1 15 travels horizontally, i.e. in the y-direction, between the collector 116 and the deflection mirror 118.

[0198] In the beam path of the illumination optical unit 103, a second facet mirror 121 is disposed downstream of the first facet mirror 119. If the second facet mirror 121 is arranged in a pupil plane of the illumination optical unit 103, it is also referred to as a pupil facet mirror. The second facet mirror 121 may also be arranged at a distance from a pupil plane of the illumination optical unit 103. In this case, the combination of the first facet mirror 119 and the second facet mirror 121 is also referred to as a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1 , EP 1 614 008 B1 and US 6,573,978.

[0199] The second facet mirror 121 comprises a plurality of second facets 122. In the case of a pupil facet mirror, the second facets 122 are also referred to as pupil facets.

[0200] The second facets 122 may also be macroscopic facets, which may for example have a round, rectangular or hexagonal boundary, or may alternatively be facets composed of micromirrors. In this regard, reference is also made to DE 10 2008 009 600 A1 .

[0201] The second facets 122 may have planar or, alternatively, convexly or concavely curved reflection surfaces.

[0202] The illumination optical unit 103 thus forms a doubly faceted system. This basic principle is also referred to as fly's eye integrator.

[0203] It may be advantageous to arrange the second facet mirror 121 not exactly in a plane that is optically conjugate to a pupil plane of the projection optical unit 109.

[0204] The individual first facets 120 are imaged into the object field 104 using the second facet mirror 121. The second facet mirror 121 is the last beam-shaping mirror or else actually the last mirror for the illumination radiation 1 15 in the beam path upstream of the object field 104.

[0205] In a further embodiment (not illustrated) of the illumination optical unit 103, a transfer optical unit contributing in particular to the imaging of the first facets 120 into the object field 104 may be arranged in the beam path between the second facet mirror 121 and the object field 104. The transfer optical unit can have exactly one mirror, or alternatively two or more mirrors which are arranged one behind the other in the beam path of the illumination optical unit 103. In particular, the transfer optical unit can comprise one or two normal incidence mirrors (Nl mirrors) and / or one or two grazing incidence mirrors (Gl mirrors). In the embodiment shown in Figure 1 , the illumination optical unit 103 has exactly three mirrors downstream of the collector 116, specifically the deflection mirror 1 18, the field facet mirror 119 and the pupil facet mirror 121.

[0206] In a further embodiment of the illumination optical unit 103, the deflection mirror 1 18 may also be omitted, and so the illumination optical unit 103 may then have exactly two mirrors downstream of the collector 1 16, specifically the first facet mirror 119 and the second facet mirror 121 .

[0207] The imaging of the first facets 120 into the object plane 105 by means of the second facets 122 or using the second facets 122 and a transfer optical unit is often only approximate imaging.

[0208] The projection optical unit 109 comprises a plurality of mirrors Mi, which are numbered in accordance with their arrangement in the beam path of the EUV projection exposure apparatus 100.

[0209] In the example illustrated in Figure 1 , the projection optical unit 109 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or any other number of mirrors Mi are also possible. The second- last mirror M5 and the last mirror M6 each have a through opening for the illumination radiation 115. The projection optical unit 109 is a doubly obscured optical unit. The projection optical unit 109 has an imageside numerical aperture which is greater than 0.5 and may also be greater than 0.6 and may for example be 0.7 or 0.75.

[0210] Reflection surfaces of the mirrors Mi may take the form of free-form surfaces without an axis of rotational symmetry. Alternatively, the reflection surfaces of the mirrors Mi may be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflection surface shape. Just like the mirrors of the illumination optical unit 103, the mirrors Mi may have highly reflective coatings for the illumination radiation 115. These coatings may be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

[0211] The projection optical unit 109 has a large object-image shift in the y-direction between a y-coordinate of a centre of the object field 104 and a y-coordinate of the centre of the image field 110. In the y-direction, this object-image shift may be of approximately the same size as a z-distance between the object plane 105 and the image plane 111 .

[0212] The number of intermediate image planes in the x-direction and in the y-direction in the beam path between the object field 104 and the image field 110 may be the same or may be different, depending on the embodiment of the projection optical unit 109. Examples of projection optical units with different numbers of such intermediate images in the x- and y-directions are known from US 2018 / 0074303 A1 . In each case, one of the pupil facets 122 is assigned to exactly one of the field facets 120 for the purpose of forming a respective illumination channel for illuminating the object field 104. This can in particular result in illumination according to the Kohler principle. The far field is decomposed into a multiplicity of object fields 104 with the aid of the field facets 120. The field facets 120 create a plurality of images of the intermediate focus on the pupil facets 122 respectively assigned thereto.

[0213] The field facets 120 are each imaged by an assigned pupil facet 122 onto the reticle 106 in a manner overlaid on one another in order to illuminate the object field 104. The illumination of the object field 104 is in particular of maximum homogeneity. It preferably has a uniformity error of less than 2%. Field uniformity can be attained by overlaying different illumination channels.

[0214] The illumination of the entrance pupil of the projection optical unit 109 may be defined geometrically by way of an arrangement of the pupil facets. The intensity distribution in the entrance pupil of the projection optical unit 109 may be set by selecting the illumination channels, in particular the subset of the pupil facets which guide light. This intensity distribution is also referred to as illumination setting.

[0215] A likewise preferred pupil uniformity in the region of portions of an illumination pupil of the illumination optical unit 103 that are illuminated in a defined manner can be attained by a redistribution of the illumination channels.

[0216] Further aspects and details of the illumination of the object field 104 and, in particular, of the entrance pupil of the projection optical unit 109 are described below.

[0217] The projection optical unit 109 may have in particular a homocentric entrance pupil. The latter can be accessible. It may also be inaccessible.

[0218] The entrance pupil of the projection optical unit 109 generally cannot be illuminated exactly by means of the pupil facet mirror 121. The aperture rays often do not intersect at a single point in the event of imaging by the projection optical unit 109 that telecentrically images the centre of the pupil facet mirror 121 onto the wafer 112. However, it is possible to find an area in which the spacing of the aperture rays, which is determined in pairs, becomes minimal. This area constitutes the entrance pupil or an area conjugate thereto in real space. In particular, this area exhibits finite curvature.

[0219] It may be the case that the projection optical unit 109 has different positions of the entrance pupil for the tangential beam path and for the sagittal beam path. In this case, an imaging element, in particular an optical structural element of the transfer optical unit, should be provided between the second facet mirror 121 and the reticle 106. With the aid of this optical structural element, it is possible to take account of the different position of the tangential entrance pupil and the sagittal entrance pupil. In the arrangement of the components of the illumination optical unit 103 illustrated in Figure 1 , the pupil facet mirror 121 is arranged in an area conjugate to the entrance pupil of the projection optical unit 109. The first field facet mirror 119 is tilted with respect to the object plane 105. The first facet mirror 119 is arranged so as to be tilted with respect to an arrangement plane defined by the deflection mirror 118.

[0220] The first facet mirror 119 is arranged so as to be tilted with respect to an arrangement plane defined by the second facet mirror 121 .

[0221] Figure 2 shows an exemplary DUV projection exposure apparatus 200. The DUV projection exposure apparatus 200 comprises an illumination system 201 , a device known as a reticle stage 202 for receiving and exactly positioning a reticle 203 by which the later structures on a wafer 204 are determined, a wafer holder 205 for holding, moving, and exactly positioning the wafer 204, and an imaging device, specifically a projection optical unit 206, with a plurality of optical elements, in particular lens elements 207, which are held by way of mounts 208 in a lens housing 209 of the projection optical unit 206.

[0222] As an alternative or in addition to the lens elements 207 illustrated, provision may be made of various refractive, diffractive and / or reflective optical elements, inter alia also mirrors, prisms, terminating plates, and the like.

[0223] The basic functional principle of the DUV projection exposure apparatus 200 makes provision for the structures introduced into the reticle 203 to be imaged onto the wafer 204.

[0224] The illumination system 201 provides a projection beam 210 in the form of electromagnetic radiation, which is required for the imaging of the reticle 203 onto the wafer 204. The source used for this radiation may be a laser, a plasma source, or the like. The radiation is shaped in the illumination system 201 by means of optical elements such that the projection beam 210 has the desired properties with regard to diameter, polarization, shape of the wavefront, and the like when it is incident on the reticle 203.

[0225] By means of the projection beam 210, an image of the reticle 203 is created and transferred from the projection optical unit 206 onto the wafer 204 in an appropriately reduced form. In this case, the reticle 203 and the wafer 204 can be moved synchronously, so that regions of the reticle 203 are imaged onto corresponding regions of the wafer 204 virtually continuously during what is called a scanning operation.

[0226] An air gap between the last lens element 207 and the wafer 204 can optionally be replaced by a liquid medium which has a refractive index of greater than 1.0. The liquid medium can be, for example, high- purity water. Such a construction is also referred to as immersion lithography and has an increased photolithographic resolution.

[0227] The use of the invention is not restricted to use in projection exposure apparatuses 100, 200, in particular also not with the described construction. The invention is suitable for any desired lithography systems or microlithography systems, but in particular for projection exposure apparatuses having the described construction. The invention is also suitable for EUV projection exposure apparatuses which have a smaller image-side numerical aperture than that described in connection with Figure 1 , and have no obscured mirror M5 and / or M6. In particular, the invention is also suitable for EUV projection exposure apparatuses which have an image-side numerical aperture from 0.25 to 0.5, preferably 0.3 to 0.4, particularly preferably 0.33. Moreover, the invention may advantageously also be used for optical elements of mask inspection systems for inspecting photomasks for semiconductor lithography. The invention and the subsequent exemplary embodiments should also not be understood as being restricted to a specific design.

[0228] The figures that follow illustrate the invention merely by way of example and in highly schematized form.

[0229] Figure 3 shows a basic illustration of one embodiment of the apparatus 1 according to the invention for holding an optical element 2, only part of which is shown in Figure 3. The optical element 2 can in particular be an optical element of a mask inspection system or of a lithography system. In Figure 3, two apparatuses 1 are combined to form a holding device 15, as will be explained in more detail below.

[0230] The apparatus 1 has a holding point 3 for connection to the optical element 2, a support 4 and a support foot 5, the holding point 3 being connected to the support 4. The support 4 has at least one rod leg 6 and a foot joint device 7. The foot joint device 7 articulatedly connects a lower end 6a of the rod leg 6 facing away from the holding point 3 to the support foot 5. The invention provides for the foot joint device 7 to have a supporting joint 7a and a transverse joint 7b, wherein the supporting joint 7a articulatedly connects the lower end 6a of the rod leg 6 directly to the support foot 5.

[0231] In Figure 3, the supporting joint 7a and the transverse joint 7b are illustrated merely schematically and in greatly simplified form.

[0232] In the exemplary embodiment, provision is preferably made for the supporting joint 7a and the transverse joint 7b to be oriented or aligned differently, i.e. to be deflectable in different directions.

[0233] In a preferred refinement of the invention, the supporting joint 7a and the transverse joint 7b are aligned at least approximately at a right angle to one another in a rest position of the apparatus 1 .

[0234] Figure 3 shows the apparatus 1 in the rest position, the supporting joint 7a and the transverse joint 7b being in their respective rest position and thus not deflected. For an illustration of the apparatus 1 in which the supporting joint 7a and / or the transverse joint 7b is deflected, reference should be made to Figures 4 and 5 described below.

[0235] In the exemplary embodiment according to Figure 3, the optical element 2 is oriented horizontally by way of example. Furthermore, the supporting joint 7a is oriented at least approximately vertically, i.e. aligned orthogonally to the optical element 2, and the transverse joint 7b is oriented at least approximately horizontally, i.e. aligned parallel to the optical element 2. However, the invention is not restricted to this example.

[0236] In the exemplary embodiment, the rod leg 6 is preferably tiltable about a virtual point of intersection 8 of imaginary extensions, in a rest position of the apparatus 1 , of an axis of the supporting joint 7a and of an axis of the transverse joint 7b. This is apparent for example on the basis of Figure 3.

[0237] It has proven to be advantageous if an actuating lever 9 is provided, wherein the lower end 6a of the rod leg 6 is operatively connected to the support foot 5 by way of the actuating lever 9, and wherein the transverse joint 7b articulatedly connects the lower end 6a of the rod leg 6 to the actuating lever 9.

[0238] The supporting joint 7a, the transverse joint 7b and the actuating lever 9 are preferably arranged and designed in such a way that the actuating lever 9 is tiltable relative to a rest position of the apparatus 1 so as to, when the holding point 3 is moved by actuation of the actuating lever 9, reduce deformations of the optical element 2 by interaction of the supporting joint 7a, the transverse joint 7b and the actuating lever 9, in order to counteract a tilting of the holding point 3 relative to the optical element 2.

[0239] In a particularly suitable development of the invention, the support 4 can be moved by an actuator 10, which is preferably fixed to the support foot 5, for selective positioning and / or alignment of the optical element 2.

[0240] Preferably, an actuator joint 11 is provided in order to articulatedly connect the actuating lever 9 to the actuator 10.

[0241] Preferably, a lever joint 12 is provided in order to articulatedly connect the actuating lever 9 to the support foot 5.

[0242] Provision may preferably be made for the actuator 10 to be adjustable at least approximately parallel to the supporting joint 7a in relation to a rest position of the apparatus 1 , wherein the actuator 10 is movably connected to the lower end 6a of the rod leg 6 by way of the actuating lever 9 in such a way that extension and retraction of the actuator 10 and the interaction with the lever joint 12, the actuator joint 11 , the transverse joint 7b and the supporting joint 7a displaces the lower end 6a of the rod leg 6 at least approximately parallel to the transverse joint 7b in relation to the rest position.

[0243] The actuating lever 9 may be at least partially arranged between the foot joint device 7 and the actuator 10, wherein the actuating lever 9 is articulatedly connected to the lower end 6a of the rod leg 6 by way of the transverse joint 7b, to the support foot 5 by way of the lever joint 12 and / or to the actuator 10 by way of the actuator joint 11 .

[0244] Preferably, the actuating lever 9 is elongated, wherein the actuating lever 9 has short sides (or end sides) and long sides, from which a certain transmission ratio, or in the present case a reduction ratio, results. It has proven to be advantageous if the transverse joint 7b and preferably the lever joint 12 are fixed to a short side (end side) of the actuating lever 9 facing towards the support 4, and preferably the actuator joint 11 is fixed to an opposite short side (end side) of the actuating lever facing towards the actuator 10. It has proven to be particularly suitable if the transverse joint 7b and the lever joint 12 are aligned at least approximately parallel to one another in the rest position of the apparatus 1 and / or if the vertical joint 7a and the actuator joint 11 are aligned at least approximately parallel to one another in the rest position.

[0245] The lower end 6a of the rod leg 6 may preferably be movably connected to the support foot 5 by way of the transverse joint 7b indirectly, namely by way of the actuating lever 9, the actuator joint 11 and the actuator 10. Furthermore, the lower end 6a of the rod leg 6 is articulatedly or movably connected directly to the support foot 5 by means of the supporting joint 7a.

[0246] The supporting joint 7a connects the lower end 6a of the rod leg 6 to a first connecting point of the support foot 5, said first connecting point preferably lying on a notionally extended axis of the supporting joint 7a, in relation to the rest position of the apparatus 1 or of the supporting joint 7a. By contrast, the transverse joint 7b connects the lower end 6a of the supporting leg 6 to a second connecting point by way of the actuating lever 9, the actuator joint 11 and the actuator 10 and to a third connecting point of the support foot 5 by way of the actuating lever 9 and the lever joint 12, neither of said second and third connecting points lying on a notionally extended axis of the transverse joint 7b, in relation to the rest position of the apparatus 1 or of the transverse joint 7b.

[0247] On the basis of the exemplary embodiment according to Figure 3, it is apparent that the apparatus 1 according to the invention creates a relatively direct, compared with the prior art, flow of force from the holding point 3 at the optical element 2 via the head joint device 14, the rod leg 6 and the supporting joint 7a to the support foot 5. Added to this is the flow of force from the holding point 3 via the head joint device 14, the rod leg 6, the transverse joint 7b, the actuating lever and the lever joint 12 to the support foot 5, and the flow of force from the holding point 3 via the head joint device 14, the rod leg 6, the transverse joint 7b, the actuating lever, the actuator joint 11 and the actuator 10 to the support foot 5. The direct flow of force makes it possible to avoid a more rigid attachment of the optical element to the support foot and thus impermissibly high oscillations.

[0248] Provision may preferably be made for the rod legs 6 to be rigid, in particular in the axial direction. Provision may also be made for the rod legs 6 to be flexible, in particular in the radial direction.

[0249] A refinement of the invention in which the supporting joint 7a, the transverse joint 7b, the lever joint 12 and / or the actuator joint 11 is in the form of a leaf spring joint and / or has at least one leaf spring joint has proven to be particularly suitable. The supporting joint 7a, the transverse joint 7b, the lever joint 12 and / or the actuator joint 1 1 may have at least two joint elements 13 which are axially offset relative to one another and oriented rotated by 90° relative to one another.

[0250] Figure 6 shows a basic view of an exemplary joint or of an exemplary joint device of the apparatus 1 having two joint elements 13. The joint may in particular constitute the supporting joint 7a, the transverse joint 7b, the actuator joint 11 or the lever joint 12. As viewed in the direction of an axis of the joint 7a, 7b, 11 , 12, the two joint elements 13 shown by way of example are arranged in two separate planes, the joint elements 13 being rotated by 90° or being oriented orthogonally to one another in adjacent planes. An intermediate element may be arranged between the two joint elements 13, as is graphically indicated. It is similarly also possible for more than two joint elements 13 to be provided. The joint elements 13 are preferably in the form of leaf springs.

[0251] The attachment of the joint, shown by way of example in Figure 6, to components of the apparatus 1 can be of any type, preferably as was described above in each case for the supporting joint 7a, the transverse joint 7b, the actuator joint 1 1 and the lever joint 12.

[0252] Preferably, a head joint device 14 is provided, wherein the head joint device 14 is arranged between the holding point 3 and an upper end 6b of the rod leg 6 facing towards the holding point 3.

[0253] It has proven to be advantageous if the foot joint device 7, the supporting joint 7a, the transverse joint 7b, the lever joint 12, the actuator joint 11 and / or the head joint device 14 has a plurality of joint elements 13, wherein the joint elements 13 are preferably each in the form of leaf springs.

[0254] In this regard, reference should be made to Figure 6 which has already been described above. A similar construction may also be suitable for the head joint device 14.

[0255] Figures 3 to 6 also serve to disclose a basic illustration of one embodiment of the holding device 15 according to the invention for holding an optical element 2. The holding device 15 comprises a first apparatus 1 a and a second apparatus 1 b each having the features of an apparatus 1 according to the invention. The first apparatus 1 a and the second apparatus 1 b converge towards one another in the direction of a common holding point 3 at the optical element 2. This is illustrated in Figure 3 by the dash- dotted lines along the rod legs 6 of the two apparatuses 1 a, 1 b.

[0256] It should be noted that the first apparatus 1 a and the second apparatus 1 b each correspond to an apparatus 1 and in principle can be exchanged, since the designations of "first" and "second" are used primarily to be able to distinguish between them. In particular, the first apparatus 1 a and the second apparatus 1 b may constitute apparatuses 1 according to Figures 3 and 6. Provision may preferably be made for the first apparatus 1 a and the second apparatus 1 b to at least approximately form a right angle with one another.

[0257] In a preferred refinement of the holding device 15, an actuating lever 9 of the first apparatus 1 a and an actuating lever 9 of the second apparatus 1 b are provided. The supporting joint 7a of the first apparatus 1 a, the supporting joint 7a of the second apparatus 1 b, the transverse joint 7b of the first apparatus 1 a, the transverse joint 7b of the second apparatus 1 b, the actuating lever 9 of the first apparatus 1 a and the actuating lever 9 of the second apparatus 1 b are arranged and designed in such a way that the actuating lever 9 of the first apparatus 1 a and, respectively, of the second apparatus 1 b is tiltable relative to a respective rest position of the first apparatus 1 a and of the second apparatus 1 b. This makes it possible to reduce deformations of the optical element 2 by interaction of the supporting joints 7a, the transverse joints 7b and the actuating levers 9, in order to, when the holding point 3 is moved by actuation of one or both actuating levers 9, counteract a tilting of the holding point 3 relative to the optical element 2.

[0258] It has proven to be advantageous if, for selective positioning and / or alignment of the optical element 2, an actuator 10 of the first apparatus 1 a is provided, and arranged and designed in such a way as to move a support 4 of the first apparatus 1 a. As an alternative or in addition, it may be advantageous if, for selective positioning and / or alignment of the optical element 2, an actuator 10 of the second apparatus 1 b is provided, and arranged and designed in such a way as to move a support 4 of the second apparatus 1 b.

[0259] Preferably, the actuator 10 of the first apparatus 1 a and / or the actuator 10 of the second apparatus 1 b is adjustable at least approximately parallel to the respective supporting joint 7a in relation to a rest position of the apparatus 1 a, 1 b, wherein the actuator 10 of the respective apparatus 1 a, 1 b is movably connected to the lower end 6a of the respective rod leg 6 in such a way that extension and retraction of the respective actuator 10 makes it possible to displace the lower end 6a of the respective rod leg 6 at least approximately parallel to the respective transverse joint 7b in relation to the rest position.

[0260] Provision may be made for a support foot 5 of the first apparatus 1 a to be formed in one piece with a support foot 5 of the second apparatus 1 b.

[0261] It is advantageous if the supporting joint 7a and / or the transverse joint 7b is bendable or deflectable at least in a plane spanned by both apparatuses 1 a, 1 b, i.e. in the plane of the drawing in Figures 3 to 5. Furthermore, it may be advantageous if the supporting joint 7a and / or the transverse joint 7b is additionally deflectable in a second direction orthogonal thereto. This is possible for example by way of a joint construction according to Figure 6 already described above.

[0262] Figures 4 and 5 show the embodiments of the apparatus 1 , 1 a according to the invention or of the holding device 15 according to Figure 3 outside the rest position. Figure 4 shows the joints, in particular the supporting joint 7a and the transverse joint 7b of the foot joint device 7, in the case of an active deflection by the actuator 10 of the first apparatus 1 a. Figure 5 shows the joints, in particular the joints 7a, 7b of the foot joint device 7, in the case of a passive deflection, which can be caused by the adjustment of the actuator 10 of another apparatus 1 or holding device 15 fixed to the optical element 2.

[0263] For better comparison, the apparatus 1 in the rest position, as shown in Figure 3, is depicted in the background with thinner lines in each of Figures 4 and 5. The thicker lines represent the apparatus 1 in the deflected state. The reference signs depicted in the drawing are also based thereon.

[0264] In the case of the active deflection according to Figure 4, the optical element 2 is specifically moved upwards to the right by retraction of the actuator 10 of the first apparatus 1 a. In the exemplary embodiment shown, the adjustment path of the actuator 10 in particular runs parallel to the supporting joint 7a of the first apparatus 1 a in relation to the rest position, i.e. parallel to the supporting joint 7a, as depicted in the background of Figure 4 with a thinner line. The active movement of the actuator 10 causes the actuating lever 9 of the first apparatus 1 a, said actuating lever being movably or articulatedly connected to the actuator 10 by way of the actuator joint 11 , to assume a position that is tilted in comparison to the rest position. In this case, the supporting joint 7a, the transverse joint 7b, the actuator joint 11 , the lever joint 12 and / or the head joint device of the first apparatus 1 a may be deflected. This may also apply to the actuating lever 9, and to the corresponding joints 7a, 7b, 11 , 12 and / or the head joint device 14, of the second apparatus 1 b, the second apparatus 1 b being passively deflected.

[0265] The actively effected tilting of the actuating lever 9 of the first apparatus 1 a can preferably lead to a transverse movement, in the example shown in particular a horizontal translational movement, of the lower end 6a of the rod leg 6 of the first apparatus 1 a, this movement being transmitted to the lower end 6a of the rod leg 6 by way of the transverse joint 7b. Furthermore, the supporting joint 7a is preferably configured and designed to permit the resulting horizontal movement of the lower end 6a of the rod leg 6 of the first apparatus 1 a. The rod leg 6 of the first apparatus 1 a may experience a movement component in the longitudinal direction of the rod leg 6 and a movement component transversely thereto, in particular in the direction of the second apparatus 1 b or in the horizontal direction. The movement component in the longitudinal direction of the rod leg 6 displaces the holding point 3. Provision may in particular be made for the rod leg 6 of the second apparatus 1 b to be tilted about the point of intersection 8 of imaginary extensions, in each case in the rest position, of the axes of the supporting joint 7a and of the transverse joint 7b of the second apparatus 1 b.

[0266] As can be seen in Figure 4, the head joint devices 14 of the apparatuses 1 a, 1 b can preferably have an at least approximately equal bending moment, with the result that the bending moments at least virtually cancel one another out. In particular, a tilting of the holding point 3 relative to the optical element 2 can be counteracted by the arrangement of the supporting joint 7a, of the transverse joint 7b and of the tiltable actuating lever 9 and the interaction thereof. The invention thus advantageously avoids the transmission of parasitic forces and / or moments to the optical element 2 and thus the deformation of the latter. In the case of the passive deflection according to Figure 5, none of the rod legs 6 shown are actuated, even though the apparatuses 1 a, 1 b are not in the rest position. Such a situation can occur if the optical element 2, as described in more detail below, is held by more than one apparatus 1 or more than one holding device 15. In relation to the exemplary embodiment shown, at least one of the apparatuses 1 or holding devices 15 (not illustrated in Figure 5) of the optical element 2 would be actively deflected, as a result of which the apparatuses 1 a, 1 b shown are passively deflected. It may, inter alia, be desired that the optical element 2 be tilted at the holding point 3 shown. To this end, provision may be made for the actuating levers 9 of the passively deflected apparatuses 1 a, 1 b to be fixedly held or positionally stable. The necessary movability can be provided by the foot joint devices 7 with their respective supporting joint 7a and transverse joint 7b of the passively deflected apparatuses 1 a, 1 b.

[0267] Aspects that are not described in more detail in relation to Figures 4 and 5 are similar to Figure 3.

[0268] Figure 7 shows, in a top view, a basic illustration of one embodiment of the arrangement 16 according to the invention and of the system 17 according to the invention for holding an optical element 2. The arrangement 16 has at least six apparatuses 1 according to the invention, preferably two respective apparatuses 1 being able to form a holding device 15 according to the invention, or the arrangement 16 has three holding devices 15 according to the invention. In particular, each of the holding devices 15 has two apparatuses 1. Instead of the arrangement in pairs of apparatuses 1 in the form of holding devices 15, the apparatuses 1 could, however, also be arranged individually.

[0269] The apparatuses 1 or holding devices 15 which are illustrated merely schematically in Figure 7 can preferably be designed as was described above on the basis of Figures 1 to 6.

[0270] Preferably, exactly six apparatuses 1 are provided for the arrangement 16 according to the invention, or the system 17 according to the invention. The apparatuses 1 can be used individually or in pairs, to form a respective holding device 15, in order to hold the optical element 2. Preferably, three holding devices 15 are provided.

[0271] The holding devices 15 are preferably in the form of bipods. The two limbs of a bipod can each be formed by an apparatus 1 according to the invention.

[0272] Preferably, the apparatuses 1 and / or the holding devices 15 are at least approximately uniformly distributed around an outer peripheral region of the optical element 2.

[0273] The V-shaped holding devices 15 can be arranged preferably tangentially to the periphery of the optical element 2. The holding devices 15 are preferably aligned perpendicularly to the optical element 2, or an optical face 2a of the optical element 2. The holding devices 15 may, however, also be arranged and / or aligned differently. In a preferred refinement of the invention, the holding devices 15 are also intended to position and / or align the optical element 2.

[0274] If one of the apparatuses 1 or holding devices 15 arranged on the optical element 2 is actively deflected, in particular by an actuator 10, for the positioning and / or alignment of the optical element 2, a passive deflection can occur at the adjacent apparatuses 1 or holding devices 15. This is in particular based on the fact that forces and / or moments introduced at the holding point 3 of the actively deflected apparatus or holding device 15 into the optical element 2 can be transmitted by way of the optical element 2 to the holding point 3 of the adjacent apparatuses 1 or holding devices 15. For a comparison of the active and passive deflection, reference should also be made to the above description of Figures 4 and 5.

[0275] If the shown embodiment of the arrangement 16 of apparatuses 1 or holding devices 15 is considered together with the optical element 2, a system 17 according to the invention is obtained. The system 17 thus comprises the optical element 2, at least six apparatuses 1 according to the invention, two respective apparatuses 1 being able to form a holding device 15 according to the invention, or has at least three holding devices 15 according to the invention for holding the optical element 2. The optical element 2 can in particular be a mirror or a lens element.

[0276] What is also not illustrated in the exemplary embodiment, but possible in principle, is that in each case three apparatuses 1 according to the invention are assembled to form a common device, these apparatuses converging towards one another at a common holding point 3, the rod legs 6 of the apparatuses 1 also each converging towards one another. Preferably, in that case two such devices are provided in order to hold an optical element 2.

[0277] Figures 3 to 7 also serve to disclose a method according to the invention for holding and in particular for positioning and / or aligning an optical element 2, wherein the optical element 2 is held and in particular positioned and / or aligned by means of at least one apparatus 1 according to the invention and / or one holding device 15 according to the invention or an arrangement 16 according to the invention.

[0278] The exemplary embodiments according to Figures 3 to 7 of the apparatus 1 according to the invention, the holding apparatus 15 according to the invention, the arrangement 16 according to the invention, the system 17 according to the invention and the method according to the invention are particularly suitable for holding, and possibly for positioning and / or aligning, an optical element 2 of a mask inspection system or of a lithography system.

[0279] In the case of a mask inspection system according to the invention for inspecting a photomask, comprising an illumination device with a radiation source and an optical unit which comprises at least one optical element 2, and comprising a detection device, the optical element 2 is held, and possibly positioned and / or aligned, by at least one apparatus 1 according to the invention and / or one holding device 15 according to the invention or an arrangement 16 according to the invention. The photomask may in particular be a reticle 106, 203 for a projection exposure apparatus 100, 200 according to Figures 1 and 2.

[0280] The optical element 2 of a lithography system may in particular be an optical element 116, 118, 119, 120, 121 , 122, Mi, 207 of a projection exposure apparatus 100, 200 for semiconductor lithography, comprising an illumination system 101 , 201 with a radiation source 102 and an optical unit 103, 109, 206, according to Figures 1 and 2. In the case of a lithography system according to the invention, at least one of the optical elements 116, 118, 119, 120, 121 , 122, Mi, 207 is held, and possibly positioned and / or aligned, by at least one apparatus 1 according to the invention and / or one holding device 15 according to the invention or an arrangement 16 according to the invention.

[0281] List of reference signs

[0282] 1 Apparatus

[0283] 1a First apparatus

[0284] 1b Second apparatus

[0285] 2 Optical element

[0286] 2a Optical surface

[0287] 3 Holding point

[0288] 4 Support

[0289] 5 Support foot

[0290] 6 Rod leg

[0291] 6a Lower end (of the rod leg 6)

[0292] 6b Upper end (of the rod leg 6)

[0293] 7 Foot joint device

[0294] 7a Supporting joint

[0295] 7b Transverse joint

[0296] 8 Virtual point of intersection

[0297] 9 Actuating lever

[0298] 10 Actuator

[0299] 11 Actuator joint

[0300] 12 Lever joint

[0301] 13 Joint element

[0302] 14 Head joint device

[0303] 15 Holding device

[0304] 16 Arrangement

[0305] 17 System

[0306] 100 EUV projection exposure apparatus

[0307] 101 Illumination system

[0308] 102 Radiation source

[0309] 103 Illumination optical unit

[0310] 104 Object field

[0311] 105 Object plane

[0312] 106 Reticle

[0313] 107 Reticle holder

[0314] 108 Reticle displacement drive

[0315] 109 Projection optical unit

[0316] 110 Image field

[0317] 111 Image plane

[0318] 112 Wafer 113 Wafer holder

[0319] 114 Wafer displacement drive

[0320] 115 EUV / used / illumination radiation

[0321] 116 Collector

[0322] 117 Intermediate focal plane

[0323] 118 Deflection mirror

[0324] 119 First facet mirror / field facet mirror

[0325] 120 First facets / field facets

[0326] 121 Second facet mirror / pupil facet mirror

[0327] 122 Second facets / pupil facets

[0328] 200 DUV projection exposure apparatus

[0329] 201 Illumination system

[0330] 202 Reticle stage

[0331] 203 Reticle

[0332] 204 Wafer

[0333] 205 Wafer holder

[0334] 206 Projection optical unit

[0335] 207 Lens element

[0336] 208 Mount

[0337] 209 Lens housing

[0338] 210 Projection beam

[0339] Mi Mirror

Claims

Claims:

1. Apparatus (1) for holding an optical element (2), in particular an optical element of a mask inspection system or of a lithography system, comprising a holding point (3) for connection to the optical element (2), a support (4) and a support foot (5), wherein the holding point (3) is connected to the support (4), wherein the support (4) has at least one rod leg (6) and a foot joint device (7), and wherein the foot joint device (7) articulatedly connects a lower end (6a) of the rod leg (6) facing away from the holding point (3) to the support foot (5), characterized in that the foot joint device (7) has a supporting joint (7a) and a transverse joint (7b), wherein the supporting joint (7a) articulatedly connects the lower end (6a) of the rod leg (6) directly to the support foot (5).

2. Apparatus (1) according to Claim 1 , characterized in that the supporting joint (7a) and the transverse joint (7b) are aligned at least approximately at a right angle to one another in a rest position of the apparatus (1).

3. Apparatus (1) according to Claim 1 or 2, characterized in that the rod leg (6) is tiltable about a virtual point of intersection (8) of imaginary extensions, in a rest position of the apparatus (1), of an axis of the supporting joint (7a) and of an axis of the transverse joint (7b).

4. Apparatus (1) according to Claim 1 , 2 or 3, characterized in that an actuating lever (9) is provided, wherein the lower end (6a) of the rod leg (6) is operatively connected to the support foot (5) by way of the actuating lever (9), and wherein the transverse joint (7b) articulatedly connects the lower end (6a) of the rod leg (6) to the actuating lever (9).

5. Apparatus (1) according to Claim 4, characterized in that the supporting joint (7a), the transverse joint (7b) and the actuating lever (9) are arranged and designed in such a way that the actuating lever (9) is tiltable relative to a rest position of the apparatus (1) so as to, when the holding point (3) is moved by actuation of the actuating lever (9), reduce deformations of the optical element (2) by interaction of the supporting joint (7a), the transverse joint (7b) and the actuating lever (9), in order to counteract a tilting of the holding point (3) relative to the optical element (2).

6. Apparatus (1) according to any of Claims 1 to 5,characterized in that the support (4) can be moved by an actuator (10), which is preferably fixed to the support foot (5), for selective positioning and / or alignment of the optical element (2).

7. Apparatus (1) according to Claim 6, characterized in that an actuator joint (1 1) is provided in order to articulatedly connect the actuating lever (9) to the actuator (10).

8. Apparatus (1) according to Claim 6 or 7, characterized in that the actuator (10) is adjustable at least approximately parallel to the supporting joint (7a) in relation to a rest position of the apparatus (1), wherein the actuator (10) is movably connected to the lower end (6a) of the rod leg (6) by way of the actuating lever (9) in such a way that extension and retraction of the actuator (10) makes it possible to displace the lower end (6a) of the rod leg (6) at least approximately parallel to the transverse joint (7b) in relation to the rest position.

9. Apparatus (1) according to any of Claims 4 to 8, characterized in that a lever joint (12) is provided in order to articulatedly connect the actuating lever (9) to the support foot (5).

10. Apparatus (1) according to any of Claims 6 to 9, characterized in that the actuating lever (9) is at least partially arranged between the foot joint device (7) and the actuator (10), wherein the actuating lever (9) is articulatedly connected to the lower end (6a) of the rod leg (6) by way of the transverse joint (7b), to the support foot (5) by way of the lever joint (12) and / or to the actuator (10) by way of the actuator joint (11).11 . Apparatus according to any of Claims 1 to 10, characterized in that the rod legs (6) are rigid, in particular in the axial direction.

12. Apparatus according to any of Claims 1 to 11 , characterized in that the rod legs (6) are flexible, in particular in the radial direction.

13. Apparatus (1) according to any of Claims 1 to 12, characterized in thatthe supporting joint (7a), the transverse joint (7b), the lever joint (12) and / or the actuator joint (11) is in the form of a leaf spring joint and / or has at least one leaf spring joint.

14. Apparatus (1) according to any of Claims 1 to 13, characterized in that the supporting joint (7a), the transverse joint (7b), the lever joint (12) and / or the actuator joint (11) has at least two joint elements (13) which are axially offset relative to one another and oriented rotated by 90° relative to one another.

15. Apparatus (1) according to any of Claims 1 to 14, characterized in that a head joint device (14) is provided, wherein the head joint device (14) is arranged between the holding point (3) and an upper end (6b) of the rod leg (6) facing towards the holding point (3).

16. Apparatus (1) according to any of Claims 1 to 15, characterized in that the foot joint device (7), the supporting joint (7a), the transverse joint (7b), the lever joint (12), the actuator joint (1 1) and / or the head joint device (14) has a plurality of joint elements (13), wherein the joint elements (13) are preferably each in the form of leaf springs.

17. Holding device (15) for holding an optical element (2), in particular an optical element of a mask inspection system or of a lithography system, at least comprising a first apparatus (1 a) and a second apparatus (1 b) in each case according to any of Claims 1 to 16, characterized in that the first apparatus (1 a) and the second apparatus (1 b) converge towards one another in the direction of a common holding point (3) at the optical element (2).

18. Holding device (15) according to Claim 17, characterized in that the first apparatus (1 a) and the second apparatus (1 b) at least approximately form a right angle with one another.

19. Holding device (15) according to Claim 17 or 18, characterized in that an actuating lever (9) of the first apparatus (1 a) and an actuating lever (9) of the second apparatus (1 b) are provided, wherein the supporting joint (7a) of the first apparatus (1 a), the supporting joint (7 a) of the second apparatus (1 b), the transverse joint (7b) ofthe first apparatus (1 a), the transverse joint (7b) of the second apparatus (1 b), the actuating lever (9) of the first apparatus (1 a) and the actuating lever (9) of the second apparatus (1 b) are arranged and designed in such a way that the actuating lever (9) of the first apparatus (1 a) and, respectively, of the second apparatus (1 b) istiltable relative to a respective rest position of the first apparatus (1 a) and of the second apparatus (1 b) so as to reduce deformations of the optical element (2) by interaction of the supporting joints (7a), the transverse joints (7b) and the actuating levers (9), in order to counteract a tilting of the holding point (3) relative to the optical element (2) when the holding point (3) is moved by actuation of one or both of the actuating levers (9).

20. Holding device (15) according to Claim 17, 18 or 19, characterized in that, for selective positioning and / or alignment of the optical element (2), an actuator (10) of the first apparatus (1 a) is arranged and designed in such a way as to move a support (4) of the first apparatus (1 a), and / or, for selective positioning and / or alignment of the optical element (2), an actuator (10) of the second apparatus (1 b) is arranged and designed in such a way as to move a support (4) of the second apparatus (1 b).21 . Holding device (15) according to Claim 20, characterized in that the actuator (10) of the first apparatus (1 a) and / or the actuator (10) of the second apparatus (1 b) is adjustable at least approximately parallel to the respective supporting joint (7a) in relation to a rest position of the apparatus (1 a, 1 b), wherein the actuator (10) of the respective apparatus (1 a, 1 b) is movably connected to the lower end (6a) of the respective rod leg (6) in such a way that extension and retraction of the respective actuator (10) makes it possible to displace the lower end (6a) of the respective rod leg (6) at least approximately parallel to the respective transverse joint (7b) in relation to the rest position.

22. Holding device (15) according to any of Claims 17 to 21 , characterized in that a support foot (5) of the first apparatus (1 a) is formed in one piece with a support foot (5) of the second apparatus (1 b).

23. Arrangement (16) for holding an optical element (2), in particular an optical element of a mask inspection system or of a lithography system, at least comprising six apparatuses (1) according to any of Claims 1 to 16 or three holding devices (15) according to any of Claims 17 to 22.

24. Arrangement (16) according to Claim 23, characterized in that the apparatuses (1) and / or the holding devices (15) are at least approximately uniformly distributed around an outer peripheral region of the optical element (2).

25. System (17) comprising an optical element (2), in particular an optical element of a mask inspection system or of a lithography system, and at least comprising six apparatuses (1) according to any ofClaims 1 to 16 or three holding devices (15) according to any of Claims 17 to 22 for holding the optical element (2).

26. System (17) according to Claim 25, characterized in that the optical element (2) is a mirror or a lens element.

27. Method for holding and in particular for positioning and / or aligning an optical element (2), in particular an optical element of a mask inspection system or of a lithography system, characterized in that the optical element (2) is held and in particular positioned and / or aligned by means of at least one apparatus (1) according to any of Claims 1 to 16 and / or a holding device (15) according to any of Claims 17 to 22 or an arrangement (16) according to Claim 23 or 24.

28. Mask inspection system for inspecting a photomask, in particular a reticle (106, 203) for a projection exposure apparatus (100, 200), comprising an illumination device with a radiation source and an optical unit which comprises at least one optical element (2), and comprising a detection device, characterized in that the optical element (2) is held by at least one apparatus (1) according to any of Claims 1 to 16 and / or a holding device (15) according to any of Claims 17 to 22 or an arrangement (16) according to Claim 23 or 24.

29. Lithography system, in particular projection exposure apparatus (100, 200) for semiconductor lithography, comprising an illumination system (101 , 201) with a radiation source (102) and an optical unit (103, 109, 206) which comprises at least one optical element (116, 118, 119, 120, 121 , 122, Mi, 207), characterized in that the optical element (1 16, 1 18, 1 19, 120, 121 , 122, Mi, 207) is held by at least one apparatus (1) according to one of Claims 1 to 16 and / or a holding device (15) according to one of Claims 17 to 22 or an arrangement (16) according to Claim 23 or 24.

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