Optical element, and associated assembly and optical system

Abstract

The optical element (OE) incorporated into the holding device for the purpose of forming the assembly (BG) for constructing the optical system is transparent to light from the wavelength range of use and comprises a body (K) on which a first light passage surface (LF1) and an opposite second light passage surface (LF2) are formed. Each light passage surface (LF1, LF2) has an optical use area (NB1, NB2) arranged in the use beam path of the optical system and an edge area (RB1, RB2) located outside the area and serving as an engagement area for the holding element (HE) of the holding device, and has a surface shape designed according to the use area specification specified by the function of the optical element (OE) in the use beam path. A light deflection structure (LUS1) is formed in at least one edge area (RB1) of the light passage surface (LF1) and is designed according to an edge area specification that deviates from the use area specification and deflects a portion of the light deflected by the light deflection structure into a target area (ZB) outside the use beam path.

Description

Technical Field

[0001] The following disclosure is based on German Patent Application No. 10 2022 205 143.2, filed on May 24, 2022, which is incorporated herein by reference.

Background Art

[0002] The present invention relates to an assembly comprising an optical element for incorporation into a holding device for the purpose of forming an assembly for constructing an optical system of a microlithographic projection exposure apparatus, the optical element, and a holding device for holding the optical element, and to an optical system having at least one such optical element.

[0003] A preferred field of application is the field of optical imaging systems for constructing microlithographic projection exposure apparatuses, in particular optical imaging systems in the form of dioptric or catadioptric microlithographic projection lenses.

[0004] Recently, micro-lithographic projection exposure methods are mainly used for manufacturing semiconductor components and other fine-structured components. Here, a mask (photomask, reticle) that holds or forms the pattern of the structure to be imaged, such as the line pattern of a layer of a semiconductor component, is utilized. In a projection exposure apparatus, the mask is disposed in the beam path between the illumination system and the projection lens, and as a result, the pattern is located within the region of the object plane of the projection lens. The substrate to be exposed, such as a semiconductor wafer coated with a radiation-sensitive layer (resist, photoresist), is held such that the radiation-sensitive surface of the substrate is disposed within the region of the image plane of the projection lens that is optically conjugate to the object plane. During the exposure procedure, the pattern is irradiated by an illumination system that forms illumination radiation from the radiation of a primary radiation source, directed towards the pattern, within an illumination field having a defined shape and size, characterized by specific illumination parameters. The radiation modified by the pattern travels as projection radiation through the projection lens, and the projection lens images the pattern onto the substrate to be exposed, which is coated with a radiation-sensitive layer. For example, the micro-lithographic projection exposure method can also be used for manufacturing a mask (reticle).

[0005] One of the aims in the development of projection exposure apparatuses is to lithographically manufacture structures with even smaller dimensions on a substrate. For example, in the case of semiconductor components, as the structure becomes smaller, the integration density increases, which generally has a beneficial effect on the performance of the components of the manufactured fine structure. The size of the structures that can be manufactured depends critically on the resolution of the projection lens used, and the resolution can be improved by, firstly, reducing the wavelength of the projection radiation used for projection and, secondly, increasing the numerical aperture NA on the image side of the projection lens used in the process.

[0006] A projection lens is generally an optical imaging system having a number of optical elements in order to partially satisfy conflicting requirements regarding correction of imaging aberration, even in cases where a large numerical aperture is used. In the field of microlithography, both dioptric or refractive imaging systems and catadioptric imaging systems often have more than ten transparent optical elements.

[0007] A holding device is used to hold the optical elements at defined positions along the beam path used by the optical system. In the case of an imaging system, the beam path used is usually referred to as the imaging beam path. The optical elements of the imaging system that contribute to imaging have an optical use area located within the imaging beam path and an edge area located outside the optical use area. The refractive or reflective surfaces are prepared to the optical quality within the optical use area. The surface shape is specified according to the desired optical effect of the optical element by the design parameters of the optical design of the imaging system, and the specification is usually in the form of polynomial coefficients of a polynomial that defines the surface shape. In a specification table, the optical use area is often also referred to as the "clear optical diameter" or "clear aperture" of the optical element. It is not necessary to achieve optical quality in the edge area. When assembling an assembly with lens elements and other transparent optical elements, the holding elements of the holding device assigned to the optical elements usually engage with the edge area. A corresponding description applies to the optical elements within the illumination system, and the beam path used is often referred to as the illumination beam path.

[0008] Various options have been proposed for fixing an optical element to a holding element. U.S. Patent Application Publication No. 2003 / 0234918 discloses an example of a clamping mount technique where the optical element is held by an anti-vibration holding element within the edge area (soft mount). In another holding device, the elastic holding elements of the holding device are bonded to the optical element with an adhesive within the area of the contact zone assigned to each by an adhesive layer. Examples of adhesive bonding techniques are disclosed in U.S. Patent No. 4,733,945 or U.S. Patent No. 6,097,536.

[0009] In reality, in the case of an optical imaging system with a complex structure, radiation not only reaches the image plane from the object along the imaging beam path, which is desirable for imaging, but also parts of the radiation that do not contribute to imaging, but in some cases interfere or cause degradation can occur. For example, what is called "super-aperture light" can lead to degradation of the imaging quality in the case of a projection exposure method. In this context, "super-aperture light" refers to light diffracted by a mask that provides a structure and radiated at an angle larger than the object-side aperture angle used for imaging, where the object-side aperture angle is determined by the actual diameter of the aperture stop that defines the boundary of the imaging beam path. Since super-aperture light cannot reach the image plane through the aperture stop, it does not directly contribute to imaging. However, super-aperture light heats the optical elements located between the mask and the aperture stop. As a result of this heating, the refractive index and the lens element shape change, and as a result, there is a disturbance of the wavefront that contributes to image generation. Alternatively or in addition, scattered light can also be generated, and scattered light generally reduces the contrast of the generated image when it reaches the image plane. In this case, the term "scattered light" in particular refers to light that can occur, for example, as a result of residual reflections on the surface of a transparent optical element coated with an anti-reflection film at the rear side of a mirror and / or other locations within the area of the imaging beam path. Such undesirable parts of the light of the wavelength specified for imaging, in particular scattered light and super-aperture light, are also referred to within the scope of the present application as "stray light", regardless of their cause.

[0010] In addition to the inherent imaging aberrations that a projection lens may have for its optical design and manufacture, imaging aberrations can also occur during the period of use, for example, during the operation of the projection exposure apparatus by the user. It turns out that the cause of such imaging aberrations is often in the change of the optical elements used in the projection lens caused by the radiation utilized during use. As an example, a part of this radiation can be absorbed by the optical elements in the projection lens. The range of absorption depends particularly on the materials used for the optical elements, such as lens element materials, mirror materials, and / or perhaps the properties of the anti-reflection film or reflective coating provided. The optical elements can be heated by the absorption of the projection radiation, and as a result, surface deformation can be caused in the optical elements. In the case of refractive elements, changes in the refractive index can be directly and indirectly caused through thermally induced mechanical stress. Due to the change in the refractive index and surface deformation, the imaging characteristics of the individual optical elements change, and thus the entire projection lens can also change. This problem area is often dealt with under the heading of "lens heating".

[0011] The illumination system can also suffer from performance degradation due to light propagating outside the illumination beam path.

[0012] In order to improve the benefits for customers of high-performance microlithography optical systems, throughput improvement for projection exposure apparatuses is achieved within the scope of the roadmap for lithography using deep ultraviolet (DUV) radiation. Due to the higher light intensity required in this case, it is expected that the "lens heating" effect will increase with the improvement in throughput. However, a significant increase in the lens heating effect is hardly acceptable in the case of invariant and even more stringent lithography requirements. Summary of the Invention Problems to be Solved by the Invention

[0013] Therefore, even in the case of an increase in light intensity, a measure that can contribute to avoiding the negative effect of the "lens heating" effect or limiting it to a non-critical level if possible is considered to be in demand.

[0014] To solve this problem, the present invention provides an optical element having the features of claim 1. An assembly having the features of claim 9 and an optical system having at least one such optical element are also provided. Advantageous developments are specified in the dependent claims. The wording of all claims is incorporated by reference into the description.

Means for Solving the Problem

[0015] According to a first aspect, the present invention provides an optical element for incorporation into a holding device, and the incorporated optical element jointly forms an assembly with the holding device. The assembly serves to construct an optical system for a microlithographic projection exposure apparatus, in particular a projection lens or an imaging system. Such an optical system usually comprises a number of assemblies each having an optical element held thereby, and the assemblies, in the assembled state, jointly define a common use beam path which, in the case of an imaging system, is also referred to as an imaging beam path.

[0016] The optical element has a transparent body made of a material having a high transmittance for light from the wavelength range used or being transparent. For example, the material can be synthetic fused silica or a fluoride crystal material, such as calcium fluoride. On both sides of the transparent body, light-passing surfaces, i.e., a first light-passing surface and a second light-passing surface on the opposite side, are formed. When light passes through the optical element, one of the light-passing surfaces acts as a light inlet surface and the other acts as a light outlet surface.

[0017] For example, the optical element can be a lens element having a positive or negative refractive power or a parallel plate substantially without refractive power.

[0018] Each of the light-passing surfaces has an optical use area and an edge area located outside the optical use area. In the assembled state, the optical use area is provided for placement within the use beam path of the optical system. The edge area is provided as an engagement area for the holding elements of the holding device. In the assembled state, these can engage with the edge area within the area of the contact zone. The optical use area can be used without being impaired by the holding elements of the holding device. Each of the light-passing surfaces is prepared to the optical quality within the optical use area, which means that, in particular, there is no surface roughness that actually interferes with light passing. The surface shape within the optical use area is designed according to the specified use area specifications, and the specified use area specifications are revealed from the desired optical effect or function of the optical element within the use beam path and are specified by what is called the optical design accordingly.

[0019] As a rule, the surface shape of the optical use area continues beyond the area boundary between the optical use area and the edge area, but no particularly strict requirements are imposed regarding the surface quality. Occasionally, a part of the edge area near the use area can still have substantially optical quality as a result of overshoot of the polishing tool, but this quality decreases with an increase in the distance from the area boundary between the use area and the edge area.

[0020] In the case of the optical element according to this aspect of the invention, a (one or more) light deflection structure having a geometrically defined surface design, which is designed according to an edge area specification deviating from the use area specification, is formed within at least one edge area of the light-passing surface. The light deflection structure or its surface design is configured to deflect the part of the light deflected or path-changed by the light deflection structure into a target area that can be specified by the edge area specification outside the use beam path.

[0021] This aspect is based in part on the discovery that the portion of light that propagates outside the used beam path and impinges on the light-passing surface in the edge region during operation of the optical system mostly does not impinge from incident directions that are arbitrary or random. On the contrary, due to the structure of the optical system, it is possible to calculate the incident directions and positions at which stray light can impinge on the edge region for most of the stray light. For example, this predictability results for the portion of stray light that occurs as a result of even a very effective anti-reflection film having a residual reflectivity sufficient to reflect a portion of the incident light in at least the incident directions with radiation in a precisely predictable exit direction.

[0022] The inventors have recognized that additional benefits regarding the operation of the optical system can be obtained herein by the defined structure of the edge region. That is, when a light deflection structure having a geometrically defined surface design that can be specified by the edge region specification is provided, it is possible to completely deflect or at least mostly deflect the incident stray light into a specifiable target region outside the used beam path in a targeted manner by refraction and / or diffraction and / or reflection.

[0023] Therefore, with an appropriate edge region specification, it is possible to steer stray light that was previously regarded as an interference source and as uncontrollable in a targeted manner and thus use said stray light to improve the performance of the optical system.

[0024] Preferably, the light deflection structure comprises a refractive and / or diffractive light deflection structure. Thus, the deflection by the light deflection structure can be achieved in this case by light refraction (refraction), by light diffraction (diffraction), or by a combination of diffraction and refraction. In part, such a light deflection structure can be created in one part, for example together with the rest of the optical element, without incurring high costs during the manufacture of the optical element. In some cases, a reflective light deflection structure can also be provided, and there are options even in cases of a reflective light deflection structure that combines these with a refractive and / or diffractive light deflection structure or that uses these exclusively as a mirroring (reflection) light deflection structure.

[0025] There are various options for "using" the stray light that is deflected. One option consists of arranging the target area such that the stray light affected by the light deflection structure is steered into an area that is not critical for the performance of the optical system, for example where it is absorbed, and thus enters an absorption structure that renders the stray light harmless with respect to the function of the optical system.

[0026] In the case of an assembly case assembled with a holding device and the optical element to be held, the holding device comprises holding elements that engage in the area of a contact zone within the edge region. The contact zone is the area where there is direct or indirect mechanical contact between the holding element and the optical element. If stray light enters the area of the contact zone, this can thereby heat the contact zone and thus there is a possibility of an undesirable lens heating effect. In the case of clamping retention, these can occur, for example, when the holding element is directly heated by the stray light and the heat generated is transmitted into the material of the optical element through the contact area. In the case of an assembly case where the holding elements of the holding device are adhesively bonded to the optical element within the area of the respectively assigned contact zone, the adhesive material can be heated by the effect of the stray light and thus can indirectly result in a lens heating effect. Alternatively or additionally, local heating occurs within the area of the contact zone as a result of the absorption effect within the adhesive protection layer, provided that an adhesive protection layer for protecting the curable adhesive from damage by light of the wavelength used is provided within the area of the contact zone. If the light deflection structure is designed such that the deflected part of the light is deflected into the target area outside the contact zone, such problems can be avoided or significantly reduced when the present invention is applied.

[0027] The targeted deflection of the stray light to a specifiable target area is also used to obtain an improvement in the performance of the imaging system by means of the component of the stray light intensity that is deflected into the target area, which is used in a targeted manner to heat the components arranged in the target area for the purpose of obtaining thermally induced operations within the optical system, in particular within the imaging system.

[0028] The use of this method can be understood as follows. The stray light distribution in the position space and the angle space, as well as the intensity distribution of the stray light within the distribution, depend, as a matter of principle, not only on the optical design of the optical system but also on the type of use during the production operation. For example, the stray light distribution within the projection lens of a projection exposure apparatus depends on the mask structure of the mask (reticle) used for imaging. Alternatively or additionally, the stray light distribution also depends on the manner in which the mask is irradiated, i.e., the stray light distribution depends on what is called the irradiation setting. Thus, as a result of a coherent irradiation setting (on-axis irradiation) having a specifiable sigma value, a significantly different stray light distribution is obtained compared to an off-axis irradiation such as a dipole irradiation setting in which the mask is mainly irradiated from two inclined and mutually opposite directions.

[0029] Furthermore, the stray light distribution and the light distribution used are affected by the shape and position of the (effective) image field of view. The image field of view can have a rectangular shape or an arcuately curved shape (a "ring field of view"). The image field of view can be centered with respect to the optical axis (an "on-axis field of view") or can be located outside the center of the optical axis (an "off-axis field of view").

[0030] The spatial distribution of the stray light intensity within the optical system can be calculated for a typical combination of the mask structure and the irradiation setting. Here, the stray light can be deflected by a light deflection structure such that a thermally activated manipulator is created, and the thermally activated manipulator is designed such that its effect cancels out the adverse effect of lens heating within the region of the use beam path and thus can at least partially compensate for the adverse effect.

[0031] Such a thermally activatable manipulator is passive, i.e., it does not have a dedicated drive or actuator. Such a thermally activatable manipulator is "controlled" by the stray light deflected in a targeted manner.

[0032] Another advantage and aspect of the present invention will be apparent from the description of the claims and the exemplary embodiments of the present invention, and the exemplary embodiments will be described below with reference to the figures. BRIEF DESCRIPTION OF THE DRAWINGS

[0033]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4A

Figure 4B

Figure 5A

Figure 5B

Figure 6A

Figure 6B

Figure 7A

Figure 7B

Figure 8A

Figure 8B

Figure 9

DETAILED DESCRIPTION OF THE INVENTION

[0034] FIG. 1 shows an example of a microlithographic projection exposure apparatus WSC that can be used in the manufacture of semiconductor components and other microstructural components and operates with light or electromagnetic radiation in the deep ultraviolet (DUV) range to obtain a resolution of a fraction of a micrometer. An ArF excimer laser having an operating wavelength λ of about 193 nm serves as the primary radiation source or light source LS. Another UV laser source, such as an F 2 laser with an operating wavelength of 157 nm, or an ArF excimer laser with an operating wavelength of 248 nm is also possible.

[0035] At the exit surface ES, an illumination system ILL arranged downstream of the light source LS generates a large, clearly defined, and substantially uniformly illuminated illumination field, and the illumination field conforms to the telecentricity requirements of a projection lens PO arranged downstream of the illumination system ILL within the optical path. The illumination system ILL has devices for setting various illumination modes (illumination settings), for example, it can switch between conventional on-axis illumination with various degrees of coherence σ and off-axis illumination. As an example, the off-axis illumination mode includes annular illumination, or dipole illumination, or quadrupole illumination, or any other multipole illumination. The design of a suitable illumination system is essentially known and will not be described in further detail here. US Patent Application Publication No. 2007 / 0165202 (corresponding to WO2005 / 026843A2) shows examples of illumination systems that can be used within the scope of various embodiments.

[0036] The optical component that receives light from the laser LS, forms illumination radiation from the light, and directs the illumination radiation towards the reticle M is part of the illumination system ILL of the projection exposure apparatus.

[0037] A device RS for holding and operating the mask M (reticle) is arranged downstream of the illumination system so that the pattern arranged on the reticle lies within the object plane OS of the projection lens PO, which coincides with the exit plane ES of the illumination system and is also referred to here as the reticle plane OS. For the scanning operation, the mask can be moved in this plane in a scanning direction (y direction) perpendicular to the optical axis OA (z direction) using a scanner device.

[0038] The projection lens PO follows downstream of the reticle plane OS. The projection lens PO acts as a reduction lens and forms an image of the pattern arranged on the mask M on a substrate W coated with a photoresist layer at a reduced scale, for example, at a scale of 1:4 (|β| = 0.25) or 1:5 (|β| = 0.20), and the photosensitive substrate surface SS lies within the region of the image plane IS of the projection lens PO.

[0039] In the exemplary case, the substrate to be exposed, which is a semiconductor wafer W, is held by a device WS equipped with a scanner drive to move the wafer in the scanning direction (y-direction) synchronously with a reticle M perpendicular to the optical axis OA. The device WS, also called a "wafer stage", and the device RS, also called a "reticle stage", are components of a scanner device controlled by a scanning control device. In this embodiment, the scanning control device is integrated within the central control device CU of the projection exposure apparatus.

[0040] The illumination field generated by the illumination system ILL defines the effective object field OF used during projection exposure. In the exemplary case, the effective object field is rectangular and has a height A measured parallel to the scanning direction (y-direction) * and a width B measured perpendicular to the scanning direction (y-direction) (x-direction). * >A * Generally, the aspect ratio AR = B * / A * is between 2 and 10, especially between 3 and 8. The effective object field is positioned at a distance next to the optical axis in the y-direction (off-axis field). The effective image field IF within the image surface IS, which is optically conjugate to the effective object field, has the same shape as the effective object field and the same aspect ratio between height B and width A, but the absolute field dimensions are reduced by the imaging scale factor β of the projection lens, i.e., A = |β|A * and B = |β|B * .

[0041] When the projection lens is designed and operates as an immersion lens, radiation is sent through a thin layer of immersion liquid during the operation of the projection lens, and the thin layer is located between the exit surface of the projection lens and the image plane IS. An image-side numerical aperture NA > 1 is possible during immersion operation. A configuration as a dry lens is also possible, and in this case, the image-side numerical aperture is limited to a value NA < 1.

[0042] FIG. 2 shows a schematic meridional lens element cross-sectional view of one embodiment of a catadioptric projection lens PO, along with a beam selected to reveal the imaging beam path of the projection radiation passing through the projection lens during operation. The projection lens is provided as an imaging system having a reduction effect for imaging the pattern of a mask disposed within the object plane OS of the projection lens onto an image plane IS of the projection lens that is aligned parallel to the object plane at a reduced scale, for example, a scale of 4:1. Here, exactly two real intermediate images IMI1, IMI2 are generated between the object plane and the image plane. A first lens portion OP1, which is constructed solely of transparent optical elements and is thus refractive (dioptric), is designed such that the pattern of the object plane is imaged onto the first intermediate image IMI1 with little or no change in size. Second, a catadioptric lens portion OP2 images the first intermediate image IMI1 onto the second intermediate image IMI2 with little or no change in size. Third, a refractive lens portion OP3 is designed to image the second intermediate image IMI2 with a large reduction onto the image plane IS.

[0043] The one-surface or one-plane P1, P2, P3 of the imaging system is located between the object plane and the first intermediate image, between the first intermediate image and the second intermediate image, and between the second intermediate image and the image plane, respectively, and the chief ray CR of the optical imaging intersects the optical axis OA. The aperture stop AS of the system can be mounted within the region of the one-surface P3 of the third lens portion OP3. The one-surface P2 within the catadioptric second lens portion OP2 is in direct proximity to the concave mirror CM.

[0044] The catadioptric second lens portion OP2 includes the only concave mirror CM of the projection lens. A negative group NG having two negative lens elements is located immediately upstream of the concave mirror. In this arrangement, sometimes called a Schupmann achromat, Petzval correction, i.e., correction of image field curvature, is achieved as a result of the curvature of the concave mirror and the negative lens elements in its vicinity, and chromatic correction is achieved as a result of the refractive power of the negative lens elements upstream of the concave mirror and, further, of the stop position with respect to the concave mirror.

[0045] The reflective deflection device serves to separate a beam passing from the object plane OS to the concave mirror CM, or the corresponding partial beam path, from the beam or partial beam path passing between the concave mirror and the image plane IS after reflection at the concave mirror. For this purpose, the deflection device has a planar first deflection mirror FM1 having a first mirror surface MS1 for reflecting the radiation coming from the object plane to the concave mirror CM, and a planar second deflection mirror FM2 which is aligned at right angles to the first deflection mirror FM1 and has a second mirror surface MS2, the second deflection mirror deflecting the radiation reflected from the concave mirror in the direction of the image plane IS. Since the optical axis is bent by the deflection mirror, in the present application, the deflection mirror is also called a folding mirror. The deflection mirror extends perpendicular to the optical axis and is inclined, for example, by 45° with respect to the optical axis OA of the projection lens about an inclination axis parallel to a first direction (x-direction). When configuring the projection lens for the scanning operation, the first direction (x-direction) is perpendicular to the scanning direction (y-direction) and is thus perpendicular to the moving directions of the mask (reticle) and the substrate (wafer). For this purpose, the deflection device is realized by a prism whose adjacent side surfaces, which are aligned at right angles to each other and are reflectively coated on the outside, act as deflection mirrors.

[0046] The intermediate images IMI1, IMI2 are each optically close to the folding mirrors FM1 and FM2 closest to them, but can be at a minimum optical distance from them, so that possible defects on the mirror surface are not clearly imaged on the image plane, and the planar deflection mirrors (plane mirrors) FM1, FM2 are in a region of medium radiation energy density.

[0047] (Paraxial) The positions of the intermediate images define the field planes of a system that is optically conjugate to the object plane and the image plane, respectively. Thus, the deflection mirror is optically close to the field plane of the system, which is also called the "near-field" in the context of the present application. In this case, the first deflection mirror is arranged optically close to the first field plane belonging to the first intermediate image IMI1, and the second deflection mirror is arranged optically close to the second field plane belonging to the second intermediate image IMI2, which is optically conjugate to the first field plane.

[0048] The optical proximity or optical distance of an optical surface with respect to a reference plane (e.g., a field plane or an eye plane) is described in the present application by what is called the sub-aperture ratio SAR. In the present application, the sub-aperture ratio SAR of an optical surface is defined as follows. SAR = sign h(|r| / (|h| + |r|)) In the above formula, r represents the marginal ray height, h represents the chief ray height, the sign function sign x represents the sign of x, and according to convention, sign 0 = 1. The chief ray height is understood to mean the ray height of the chief ray of the field of view of an object field having the maximum field height in terms of magnitude. It should be understood that the ray height is signed. The marginal ray height is understood to mean the ray height of the ray having the maximum aperture proceeding from the intersection between the optical axis and the object plane. This field point does not necessarily contribute to transferring a pattern arranged in the object plane, especially in the case of an off-axis image field.

[0049] The sub-aperture ratio is a signed variable that is a measure of the field of view or the eye that is close to a plane within the beam path. By definition, the sub-aperture ratio is normalized to a value between -1 and +1, the sub-aperture ratio is zero within each field plane, and the sub-aperture ratio jumps from -1 to +1 or from +1 to -1 within the eye plane. Therefore, a sub-aperture ratio with an absolute value of 1 determines the eye plane.

[0050] Next, when the sub-aperture ratio of an optical surface or an optical plane and an optical reference surface is of the same order of magnitude numerically, these two surfaces are called "(optically) close".

[0051] In particular, when an optical surface or an optical plane has a sub-aperture ratio close to 0, it is called "(optically) near field". When an optical surface or a plane has a sub-aperture ratio close to 1 in terms of absolute value, it is called "(optically) near eye".

[0052] The use beam path of the projection lens, also called the imaging beam path or the projection beam path, extends from the effective object field of view OF to the effective image field of view IF. The use beam path is a volume (a "subset of R" 3 in a three-dimensional space), and the volume in the three-dimensional space is defined in that each point in the space has at least one continuous ray passing through it from the object field of view OF in the object-side use aperture to the image field of view IF in the image-side use aperture. The shape and position of the imaging beam path during the process generally depend on the current field of view size and the order of diffraction.

[0053] The area of the optical surface irradiated by the rays of the projection beam path coming from the effective object field of view OF is also called the "footprint" in this application. Here, the footprint of the projection radiation on the optical surface represents the size and shape of the intersection of the projection beam and the surface irradiated by the projection beam. Adjacent to the lens element section, FIG. 2 schematically shows the footprint FP at various positions along the projection beam path. The optical vicinity of the closest field plane is distinguishable by a footprint having a substantially rectangular effective object field of view OF, with the edge regions being slightly rounded (see, for example, near the lens element L1-1 or on the deflecting mirror near the intermediate image). The footprint is outside the optical axis OA, like the object field of view. In contrast, a substantially circular area is irradiated within the area of the pupil plane that is Fourier-transformed with respect to the field plane, and as a result, the footprint within the pupil area has at least a substantially circular shape (see P1 of the first refractive lens part OP1 or P2 in the optical vicinity of the concave mirror CM). The footprint can provide information, among other things, about the spatial distribution of heat induced by the radiation.

[0054] During operation, there are light rays that are not normally part of the used beam path. These include, among others, those referred to as "super-aperture light rays". In this context, these are understood to mean light rays that are diffracted by a mask that gives structure and are emitted at an angle greater than the object-side aperture angle used for imaging, where the object-side aperture angle is determined by the actual diameter of the aperture stop that defines the boundary of the projection beam path. This object-side aperture angle defines the object-side use aperture. A corresponding statement applies to the image side, i.e., the side of the image that is optically conjugate to the object.

[0055] For some further explanation of the problems and their solutions that form the basis of this application, FIG. 3A shows an enlarged portion of the projection lens of FIG. 2 from the region immediately behind the object plane OS, where in the object plane OS, a mask M having a structure PAT to be imaged is positioned during operation. A parallel plane plate PP (an optical element without refractive power) that follows immediately after the object plane and, immediately after this parallel plane plate, a lens element L1-1, which is the first transparent optical element having the refractive power closest to the object as part of the projection lens, are shown. In general, the reference sign OE shall denote an optical element.

[0056] The lens element L1-1 has a body K that is transparent to ultraviolet light (e.g., made of synthetic fused silica), and is formed as a relatively thick biconvex lens element having a first light-passing surface LF1 facing the object plane (light entrance surface LF1) and a second light-passing surface (LF2) on the opposite side (light exit surface LF2).

[0057] The lens element must realize its assigned optical function within the best possible range in the beam path under all conditions of use. Thus, each of the light-passing surfaces LF1, LF2 has an optical use area NB1, NB2, which includes the area of the optical axis and extends radially outwards from the optical axis to a range such that, under all operating conditions, all the light rays of the projection beam path pass through the optical use area on both the entrance side and the exit side. The light ray ST1 propagating at the edge of the projection beam is shown. Each of the lens element surfaces has an edge area RB1, RB2 that surrounds its respective optical use area in a ring shape outside the radial direction of the optical use area.

[0058] In the installed state, the optical element or lens element L1-1 is held by a holding device or mount that is distributed over the outer periphery of the lens element and includes several holding elements HE that face vertically and on which the lens element is placed in the case of a projection lens. Together with the lens element mounted or held therein, the mount or holding device forms an assembly BG, and the assembly BG forms a projection lens together with another assembly including another optical element.

[0059] The contact zone KZO between the holding element and the exit-side light-passing surface LF2 is positioned in a form that is azimuthally distributed within the edge area of the lens element and contacts the lens element within the area of the contact zone KZO. It is clear from the enlarged details of the area of the contact zone KZO in Figure 3B that the lens element is bonded to the holding element HE with an adhesive by its light exit side LF2. The area of the adhesive connection has a multilayer structure. An adhesive layer KL made of an adhesive material is attached to the support surface of the holding element. Before the adhesive connection is established in the area of the contact zone, an adhesive protection layer KSS disposed between the adhesive layer and the light exit surface LF2 is attached to the edge area of the light exit side LF2. The UV radiation-absorbing adhesive protection layer protects the adjacent adhesive layer KL from the UV radiation that can reach the adhesive layer through the lens element in the edge area, thus improving the service life of the adhesive connection.

[0060] Each of the light-passing surfaces is prepared with an optical quality within the optical use regions NB1, NB2 and has a surface shape designed according to the use region specifications. The use region specifications are specified by the function of the optical element within the use beam path. The use region specifications are defined within the scope of calculating the optical design. In an exemplary case, both lens element surfaces LF1, LF2 are spherically curved in the use region.

[0061] In contrast, the intention is that the edge regions RB1, RB2 do not contribute to imaging. Although the surface shape within the edge regions still corresponds to the mathematical continuity of the surface shape within the use region in the case of a conventional lens element, the optical surface is significantly rougher in the region of the radial distance from at least the transition between the use region and the edge region (dashed line), and is optically insufficient in quality at this point. This is because such surface portions are not necessary for imaging.

[0062] The characteristics of this optical element L1-1 relate to the effect on light rays that travel outside the projection beam path and reach the edge region radially outside the optical use region. FIG. 3A shows what is called a super-aperture ray UAP through which light radiated at an angle greater than the object-side aperture angle used for imaging and deflected by the mask M that gives the structure propagates. The object-side aperture angle is specified by the diameter of the aperture stop.

[0063] The solid line in FIG. 3 shows the path of the super-aperture array UAP that enters the lens element material within the entrance-side edge region RB1 through the light-passing surface LF1, passes through the lens element material, and reaches the region of the contact zone KZO on the light exit side through the light-passing surface LF2. The radiant energy is absorbed by the adhesive protection layer KSS, whereby the adjacent lens element and the adjacent holding element are heated, and optionally, the adjacent region of the mount can be heated. Due to this locally generated heat, an undesirable lens heating effect can occur.

[0064] In the illustrated embodiment, this problem is avoided by the edge region of the entrance-side light-passing surface LF1, which is given a geometrically defined surface design during manufacturing, rather than a simple extrapolation of the surface shape on the light entrance side within the usage area. The edge region is designed according to edge region specifications that deviate from the usage area specifications. In an exemplary case, a specified shaping of the light entrance surface within the edge region RB1 on the light entrance side is selected such that the entrance-side edge region RB1 has a rotationally symmetric aspherical shape. The entrance-side edge region RB1 is a transition region between the usage area and the edge region, and appears smoothly or continuously, i.e., without edges or jumps, from the surface shape of the usage area. However, in the edge region, it significantly deviates from the mathematical continuity of the usage area, which is indicated by the dashed line.

[0065] In an exemplary case, the entrance-side light-passing surface LF1 is convexly spherically curved within the optical usage area, and as the distance from the optical axis increases, the convex curvature changes to a concave curvature within a narrow region after the inflection point, before the convex curvature reappears further out. This creates a refractive light deflection structure LUS1 that ensures that the super-aperture light UAP deflected by diffraction reaches a target region ZB outside the usage beam path. The target region can be specified by the edge region specifications. In this case, the target region is defined to be located (radially) outside the contact zone KZO. In other words, the contact zone is protected from the super-aperture light rays by the refractive light deflection structure LUS1 such that the super-aperture light rays are deflected into the non-critical region outside the contact zone after passing beyond the outer contact zone, which is shown by the dashed super-aperture light ray UAP’ drawn using a dashed line.

[0066] The target region ZB, into which the deflected super-aperture light that bypasses the contact zone is incident, should be quite large or have quite a lot of mass because in the case where radiation is incident, it is only subject to small temperature changes. Furthermore, the region should have a good thermal connection to the outside so that heat does not flow back into the lens element through the heat retention element.

[0067] Since the rotationally symmetric aspherical surface (optical deflection structure LUS1) can be manufactured in one working step together with the rotationally symmetric design within the optical use area, the target deflection of the super-aperture light by the aspherical surface in the edge region of the lens element on the light entrance side of the lens element can be relatively easily achieved from the manufacturing perspective.

[0068] In the example of FIG. 3A, the optical deflection structure LUS1 has a surface shape that is continuously curved throughout the edge region, and the surface shape has a negative radius of curvature in at least one region, and thus in that region, the center of curvature is located on the light entrance side. Thereby, a diverging function or a ring-shaped circumferential diverging lens element or a diverging zone is created.

[0069] An alternative option for designing a refractive light deflection structure for the purpose of deflecting super-aperture light can be achieved by an optical deflection structure having a Fresnel lens ring in the edge region. Accordingly, the aspherical surface in the edge region can be implemented as a ring-shaped Fresnel lens element, and as a result, the installation space can be saved compared to the larger aspherical surface of FIG. 3A.

[0070] In the exemplary embodiments described below, for clarity, the same reference numerals as in FIG. 3A are partially used for the same or similar features. The above example is referred to regarding the arrangement and basic shape of the lens element L1-1.

[0071] Figures 4A and 4B show an exemplary embodiment in which the deflection of super-aperture light is achieved by diffraction using a light deflection structure LUS2 in the form of a diffraction structure within the edge region of the lens element. In this regard, FIG. 4A shows a meridional cross-sectional view similar to that of FIG. 3A, and FIG. 4B shows a plan view of the upper surface of the lens element facing the object plane (the first light passing surface LF1). The diffraction light deflection structure LUS2 has a circular diffraction structure and is formed by a diffraction grating formed rotationally symmetrically with respect to the optical axis, so that the diffraction of the incident radiation results mostly radially outward in each case. In an exemplary case, the light deflection structure LUS2 has a blazed grating having a diffraction effect for light of the wavelength used. As is quite apparent from FIG. 4A, this has a ring designed to be serrated in cross-section. Its radial spacing and the angle of the sawtooth surface are matched to each other such that the diffraction efficiency at the wavelength used is maximized for a certain diffraction order. Thus, most of the intensity components of the narrow-band projection radiation light are concentrated on a single desired diffraction order, and there is almost no intensity remaining at other orders, especially at the 0th order diffraction, i.e., when passing straight through the diffraction grating. In this way, the desired deflection angle can be set very precisely, and the light intensity of the deflected super-aperture light ray UAP’ is concentrated only in the narrow target region ZB, which can be particularly advantageous in cases of complex installation situations. Here again, the light deflection structure is designed so that the deflected stray light is redirected and does not reach the contact zone KZO. Within the scope of manufacturing the lens element, the rotationally symmetric blazed grating can be manufactured from the same material simultaneously with the lens element.

[0072] The creation of a light deflection structure rotationally symmetric with respect to the optical axis of the optical element can be advantageous for manufacturing reasons, but this may not be necessary or desirable for functional reasons in many cases. Thus, there are exemplary embodiments in which the optically effective surface shape of the edge region is not rotationally symmetric with respect to the optical axis. In particular, the surface shape can have n-fold rotational symmetry with respect to the optical axis in the edge region, where n can be, for example, 2, 3, 4, 6, or 8. Some examples are described below.

[0073] Figures 5A and 5B show a meridional sectional view (5A) and a plan view of the upper surface of the lens element (Fig. 5B) of an exemplary embodiment in which the deflection of super-aperture light is achieved by an azimuthal structure diffraction structure within the entrance-side edge region RB1 of the lens element. As is apparent from Fig. 5A, the light deflection structure LUS3 is designed as a diffraction structure, i.e., a diffraction grating, precisely in the form of a blazed grating. However, deviating from the deformation patterns of Figs. 4A and 4B, eight substantially rectangular grating regions GB are provided in a locally restricted form only within angular regions that are offset by 45° in the circumferential direction within the ring-shaped edge region RB1, and there is a contact zone or holding element substantially at the center below it. Also in this case, the diffraction grating lines extend not continuously in the circumferential direction but only over a narrow angular range with an angular width, for example, between 10° and 30°, so as to curve in the circumferential direction with a uniform radius of curvature.

[0074] A diffraction structure having a serrated cross-section can be formed in one piece with the material of the lens element body and can be manufactured in one piece with the lens element body. However, in an exemplary case, a different procedure is chosen by forming the light deflection structure LUS3 on a separate optical light deflection element LUE. The optical light deflection element LUE is manufactured separately from the transparent body of the optical element and is only fixed to a specified region within the entrance-side edge region RB1 of the body of the optical element following its completion. Here, each of the light deflection elements LUE has a contact surface on the side opposite to the light deflection structure, and the design of the contact surface is matched to the surface shape of the lens element body within the edge region. Thus, reliable fixation is possible, for example, directly by optical contact bonding without auxiliary means or using a thin adhesive layer or optical cement. In this way, even a relatively complex distribution of light deflection characteristics in the edge region can be realized within the scope of a relatively well-controllable manufacturing process. Optionally, the plane can also be incorporated into the edge region at the position provided for the light deflection element. This is because they are particularly suitable for contact without auxiliary means with the plane of the light deflection element by optical contact bonding.

[0075] A deformation mode for deflecting super-aperture light using a refractive light deflection structure in the form of a prism PR within the edge region of a lens element is described based on FIGS. 6A and 6B. The form of expression is the same as in the previous example. The plan view of the upper surface of the lens element in FIG. 6B shows that a total of eight light deflection elements LUE in the form of triangular prisms, which are dispersed over the outer periphery at the same 45° angle division, are attached to the edge region RB1, and each adhesion position is assigned to a prism. From the meridional plane cross-sectional view of FIG. 6A, the inclined prism surface having the normal direction PN faces radially inward, and as a result, an outward deflection of the radially incident super-aperture light is brought about. Similar to the example of FIG. 5, the refractive light deflection structure designed as a prism is manufactured in the form of separate light deflection elements LUE, and the light deflection elements LUE are arranged at appropriate positions within the edge region following the completion of the lens element surface and are optically neutrally connected to the lens element body, for example, by optical contact bonding or using optical cement.

[0076] FIGS. 7A and 7B are used to explain another embodiment, in which a light deflection structure LUS5 exists in the form of a prism PR. The prism PR is initially manufactured separately from the lens element body as separate prism elements and is then fixed at an appropriate position within the entrance-side edge region RB1 of the lens element by optical contact bonding or optical cement. Deviating from the deformation mode of FIGS. 6A and 6B, the prism surface PF within the beam path at an oblique angle for the purpose of light deflection has its surface normal PN not facing radially but facing circumferentially (azimuthally). As is apparent from FIG. 7A, this also makes it possible to deflect the super-aperture light so that the super-aperture light in the region does not enter the contact zone KZO with respect to the holding element.

[0077] Circumferential light deflection can also be achieved using a diffraction structure. As an example, the light deflection elements in FIGS. 5A and 5B can be designed such that the grating lines of the diffraction structure are substantially aligned radially. Thus, according to the basic concept, a large number of degrees of freedom are possible with respect to the deflection angle and direction in which stray light is intended to be deflected. In other words, the target region can be located at various positions clearly within the projection lens.

[0078] In the previous example, in particular, regardless of where the holding element is provided, and optionally, regardless of where the absorption layer is present within the region of the contact zone, the light deflection structure is designed mostly in consideration of preventing super-aperture light and other stray light from incident on the light exit surface within a certain region. As a result, it is possible to protect the connection point between the holding element and the lens element from the heating effect induced by the stray light.

[0079] However, in order to heat the component part arranged in the target region in a targeted manner and thus independently achieve the desired and predictable thermally induced operations within the optical system, it is also possible to improve the performance of the projection lens by deflecting a certain component of the stray light intensity or the entire stray light intensity into the target region or a plurality of target regions, by deflecting the targeted stray light into the defined target region.

[0080] An example of a thermal operation using stray light deflected in a targeted manner is described with reference to FIGS. 8A and 8B. In particular, a thermal manipulator is created that independently brings about a certain homogenization or equalization of the temperature distribution within the operating optical element OE, for example within the lens element. FIGS. 8A and 8B each show an axial plan view of a transparent optical element OE optically arranged in the vicinity of the field plane of a projection lens (off-axis system) having an off-axis object field and an image field. For example, the optical element can be a parallel plate PP of the projection lens of FIG. 2 or the first lens element L1-1, or a lens element arranged in the vicinity of one of the intermediate images. The optical element is mounted within a holding device having eight holding elements HE1, HE2, etc. that are uniformly distributed over the outer periphery of the optical element, and an edge region RB of the optical element is arranged on the holding element. The transparent optical element is firmly connected to the holding element by an adhesive layer protected by an adhesive protection layer.

[0081] For the near-field configuration of the illustrated light entrance surface (first light passing surface LF1), light propagating along the projection beam path generates an irradiation footprint FP on the lens element surface, the footprint having a substantially rectangular shape of the effective object field of view and at least the corners being slightly rounded due to the distance from the field plane. In this case of irradiation that is asymmetric with respect to the optical axis OA, the passing projection light generates an asymmetric temperature distribution within the optical element OA that is non-rotationally symmetric. When the temperature distribution within the edge region RB is considered, a relatively warm zone WZ is found wherever the corners of the irradiation field are close to the edge of the optical element.

[0082] Stray light propagating outside the imaging beam path impinges on the lens element in substantially the same way across the entire edge region. The contact zones of the holding elements HE1 and HE3 - HE7 are not protected, and as a result, the super-aperture light can slightly heat the contact zones located there. In contrast, the contact zones of the holding elements HE2 (at 2 o'clock) and HE8 (at 10 o'clock) are protected from the incident stray light by the light deflection structure LUS6 formed on the light entrance side, and as a result, the contact zones remain relatively cold compared to the contact zones of the other holding elements exposed to the stray light. The asymmetric thermal distribution occurring within the region of the footprint FP can be at least partially compensated as a result of this non-uniform circumferential thermal distribution of the heat generated by the stray light, and thus the temperature distribution within the optical element OE is more uniform or better homogenized than in the case without the light deflection structure LUS5.

[0083] In this example, a diffractive light deflection structure LUS6 that deflects the stray light radially outwards is used. Similar effects can also be achieved using refractive light deflection structures and / or light deflection structures that deflect the light in the circumferential direction.

[0084] FIG. 8B shows a modification of the arrangement of FIG. 8A that can produce a well-homogenized different temperature distribution. In contrast to the example of FIG. 8A, in the example of FIG. 8B, an adhesive protection layer KSS that covers all the holding elements HE3 to HE7 and the circumferentially inserted region and circumferentially surrounds them is attached on the light exit side in the edge region RB, between this light exit side and the holding elements arranged there. When super-aperture light is incident on this region, due to the absorption of stray light by the adhesive protection layer, the edge region is locally heated over the covered angular range (slightly larger than 180°). In combination with the light deflection structure LUS6 in the regions of the holding elements HE2 and HE8 closest to the footprint, this results in a further improved homogenization of the temperature distribution within the optical element.

[0085] The concept of the present invention is not limited to the use of refractive and / or diffractive light deflection structures. It is also possible to provide a light deflection structure that operates based on the reflection principle, which is advantageous in certain cases. FIG. 9 schematically shows an example. The lens element L1-1M therein has an exit-side light passing surface LF2, and its surface shape corresponds to the corresponding light exit surface of FIG. 3. In the use region NB1, similarly, the entrance-side light passing surface LF1 has the same surface shape. The deviation in this regard is found in the edge region RB1 on the light entrance side. In the exemplary embodiment of FIG. 3, the edge region specification is selected such that the light passing surface curves radially upward, i.e., toward the light entrance side, but in the variant of FIG. 9, exactly the opposite applies. In this case, the edge region specification is such that the edge region has a significantly larger curvature in the radial direction than would be expected to apply for the imagined extension V of the surface shape from the use region. In other words, an entrance surface with a convex curvature exists in the use region, and the adjacent edge region RB1 has a convex curvature as well, although with a smaller radius of curvature. Thus, the ring-shaped edge region RB1 has a design that slopes outward in the radial direction.

[0086] The single-layer or multi-layer reflective coating (mirror coating) REF adheres to the entire surface within the edge region RB1. When the super-aperture light UAP is incident on the reflective edge region, it is reflected into the target region ZB in the radially outward direction opposite to the normal light propagation direction, and the target region ZB is located upstream of the lens element, i.e., between the lens element and the object plane, so as to be visible along the optical axis. An absorber or any other light-absorbing structure is provided in this target region. In this way, the contact zone within the region of the holding element can be further protected against irradiation by the super-aperture light. In this variant, furthermore, by a specific specification of the surface shape within the edge region according to the edge region specification, it is ensured that it is possible to precisely calculate how the surface design of the mirror surface must be designed in order to deflect the super-aperture light from a known angle-of-incidence range precisely to the desired target region ZB.

[0087] Aspects of the invention have been described above using the example of an optical imaging system in the form of a microlithography projection lens. The invention can also be used in other optical systems, for example in an illumination system for constructing a microlithography projection exposure apparatus. Problems with super-aperture light, such as damage to the adhesive due to the radiation load associated with the lack of adhesive protection, can also occur in the illumination system.

Claims

1. An optical element (L1-1, OE) for incorporation into a holding device for the purpose of forming an assembly (BG) for constructing an optical system (PO) of a microlithographic projection exposure apparatus, wherein the optical element is transparent to light from the wavelength range of use and comprises a body (K) on which a first light-passing surface (LF1) and an opposite second light-passing surface (LF2) are formed, each of the light-passing surfaces (LF1, LF2) having an optical use area (NB1, NB2) provided for placement within the use beam path of the optical system and edge areas (RB1, RB2) located outside the optical use area and designated as engagement areas for holding elements (HE) of the holding device, each light-passing surface being prepared to an optical quality within the optical use area (NB1, NB2) and having a surface shape designed according to use area specifications specified by the function of the optical element (L1-1, OE) within the use beam path, in the optical element, a light deflection structure (LUS1, LUS2, LUS3, LUS4, LUS5, LUS6) having a geometrically defined surface design is formed in at least one of the edge areas (RB1) of the light-passing surface (LF1), the surface design being designed according to edge area specifications deviating from the use area specifications and configured to deflect a portion of the light deflected by the light deflection structure into a target area (ZB) outside the use beam path, and a plurality of contact zones (KZO) distributed over the outer periphery of the edge area are defined in the edge area of the light-passing surface opposite the light-passing surface having the light deflection structure, and the light deflection structure (LUS1, LUS2, LUS3, LUS4, LUS5, LUS6) is configured such that a portion of the light deflected by the light deflection structure can be deflected into the target area (ZB) outside the contact zone characterizes the optical element.

2. The optical element according to claim 1, characterized in that the light deflection structure comprises a refractive and / or diffractive light deflection structure (LUS1, LUS2, LUS3, LUS4, LUS5), and the light deflection structure preferably comprises, alternatively or additionally, a reflective light deflection structure (LUS6).

3. The following conditions, namely, (i) The edge region specification is adapted to the usage region specification such that the surface shape of the usage region (NB1) within the transition region located outside the usage region within the edge region (RB1) smoothly transitions within the surface shape of the edge region. (ii) The light passing surface has an aspherical shape that is continuously curved in the edge region according to the edge region specification, and has a spherical or aspherical shape in the optical usage region according to the usage region specification. (iii) The light deflection structure has a continuously curved surface shape having a negative radius of curvature in at least one region throughout the edge region. (iv) An inflection point region having a transition from the positive radius of curvature of the light passing surface on the side of the optical usage region to the negative radius of curvature of the light passing surface away from the optical usage region is located within the edge region. The optical element according to claim 1 or 2, wherein at least one of the above applies to the light deflection structure.

4. The light deflection structure includes a Fresnel lens ring, and / or the light deflection structure includes a diffraction grating (LUS2, LUS3, LUS6) having a diffraction effect for light of the usage wavelength, and / or the light deflection structure includes a blazed grating (LUS2, LUS3) having a diffraction effect for light of the usage wavelength. The optical element according to any one of claims 1 to 3, characterized in that.

5. The optical element (OE) has an optical axis (OA), the surface shape of the optical usage region (NB) is rotationally symmetric with respect to the optical axis, and the surface shape of the edge region (RB) is not rotationally symmetric with respect to the optical axis. The optical element according to any one of claims 1 to 4, characterized in that.

6. The optical element according to claim 5, characterized in that the surface shape within the edge region has n-fold rotational symmetry with respect to the optical axis, where n is particularly 2, 3, 4, or 6.

7. The light deflection structure is formed as one component with the material of the optical element, and / or the light deflection structure (LUS3) is manufactured separately from the transparent body (K) of the optical element and is formed on a separate optical light deflection element (LUE) attached to the edge region (RB) within a specified region. The optical element according to any one of claims 1 to 6, characterized in that.

8. Based on a calculation regarding the spatial distribution of stray light intensity in the optical system for a specified combination of a mask structure and irradiation settings such that a thermally activated manipulator exists, an optical deflection structure is designed, and the thermally activated manipulator is designed such that its effect can cancel out and at least partially compensate for the adverse effect of lens heating in the region of the use beam path. The optical element according to any one of claims 1 to 7.

9. An assembly (BG) comprising an optical element (OE) and a holding device for holding the optical element, The optical element (OE) is transparent to light from the use wavelength range and comprises a body (K) on which a first light passage surface (LF1) and an opposite second light passage surface (LF2) are formed, Each of the light passage surfaces has an optical use region (NB) positioned for placement within the use beam path and a peripheral region (RB) positioned outside the optical use region. In the optical use region, the light passage surface is prepared with optical quality according to a specification surface shape specified by the function of the optical element within the use beam path. The holding device comprises a holding element (HE) that engages within a region of a contact zone within the peripheral region (RB) of the second light passage surface (LF2). In the assembly, An optical deflection structure (LUS1, LUS2, LUS3, LUS4, LUS5, LUS6) having a geometrically defined surface design is formed within the peripheral region (RB) of the first light passage surface and is configured to deflect a portion of the light deflected by the optical deflection structure into a target region (ZB) outside the contact zone (KZ). An assembly characterized by this.

10. The surface shape of the optical deflection structure is configured irregularly in the azimuthal direction, and the maximum density of the optical deflection structure is arranged in the vicinity of the optically used footprint where the use beam path intersects the light passage surface. The assembly according to claim 9, characterized by this.

11. A material having strong absorbency at the use wavelength is arranged within the target region (ZB) of the optical deflection structure, and the absorbency of the material is greater than the absorbency of the transparent material of the optical element. The assembly according to claim 9 or 10, characterized by this.

12. An optical system having at least one optical element according to any one of claims 1 to 8 and / or having at least one assembly (BG) according to any one of claims 9 to 11.

13. The optical system according to claim 12, characterized in that it is an optical imaging system for constructing a microlithography projection exposure apparatus, in particular a dioptric or catadioptric microlithography projection lens (PO).

Images