Optical assembly, optical system and projection exposure equipment

Abstract

An optical assembly (102) for a projection exposure apparatus (1), comprising: an optical element (104); a support structure (106) carrying the optical element (104); and a plurality of decoupling devices (134) disposed between the optical element (104) and the support structure (106) to mechanically decouple the optical element (104) from the support structure (106); wherein each decoupling device (134) comprises a first decoupling element (136) and a second decoupling element (140) connected to the first coupling element (136); the first decoupling element (136) is connected to the optical element (104); and the second decoupling element (140) is connected to the support structure (106).

Description

Technical Field

[0001] The present invention relates to an optical component, an optical system having the optical component, and a projection exposure apparatus having the optical component and / or the optical system.

[0002] The content of the priority application DE 10 2023 201 859.4 is incorporated herein by reference in its entirety. Background Art

[0003] Microlithography is used to create microstructured components, such as integrated circuits. Microlithography processes are performed using a lithography system equipped with an illumination system and a projection system. An image of a mask (reticle) illuminated by the illumination system is projected by the projection system onto a substrate, such as a silicon wafer, coated with a photosensitive layer (photoresist) and positioned in the image plane of the projection system. This transfers the mask structure to the substrate's photosensitive coating.

[0004] Driven by the demand for ever-smaller structures in integrated circuit manufacturing, EUV lithography equipment is currently being developed that uses light in the wavelength range of 0.1 nm to 30 nm, particularly 13.5 nm. In the case of such EUV lithography equipment, since most materials have a high absorption of light at this wavelength, reflective optical units, i.e., mirrors, must be used to replace the previous refractive optical units, i.e., lens elements.

[0005] Using so-called reflector sockets, this reflector can be coupled to an actuator, which can be used to align the corresponding reflector. These reflector sockets can be glued to the rear side of the corresponding reflector. However, this is not mandatory. The reflector socket can also be glued to the front side of the reflector. The adhesive used for this purpose may shrink or expand, for example due to temperature or aging. To prevent parasitic forces caused by shrinkage or expansion of the adhesive from being introduced into the reflector, cutouts or decoupling cutouts can be provided on the optical element in the area of ​​the reflector socket. However, these require additional installation space. Summary of the Invention

[0006] Against this background, it is an object of the present invention to provide an improved optical component.

[0007] Therefore, an optical assembly for a projection exposure apparatus is proposed. The optical assembly comprises an optical element, a support structure carrying the optical element, and a plurality of decoupling devices arranged between the optical element and the support structure to mechanically decouple the optical element from the support structure, each decoupling device comprising a first decoupling element and a second decoupling element connected to the first coupling element, the first decoupling element being connected to the optical element and the second decoupling element being connected to the support structure.

[0008] Since the decoupling device is arranged between the optical element and the supporting structure, the installation space required for the optical component can be significantly reduced.

[0009] The optical component may be a reflector or a reflector module or the like. The optical element is preferably a reflector, in particular an EUV reflector or a DUV reflector. However, the optical element may also be a lens element. The optical element preferably has an optically active surface, in particular a reflective mirror surface. The optically active surface is configured to reflect illuminating radiation, for example EUV radiation or DUV radiation. The optically active surface can be realized by a coating. The optically active surface preferably faces away from the support structure. The optical element comprises a rear side facing away from the optically active surface. The rear side faces the support structure.

[0010] The support structure can be flat or block-shaped. In the present context, a support structure "carrying" the optical element particularly means that the support structure is capable of absorbing the weight of the optical element. The optical element is operatively connected to the support structure by a decoupling device, which, however, ensures that the optical element and the support structure are mechanically decoupled. In particular, this means that the decoupling device is connected to both the optical element and the support structure. Thus, the optical element is indirectly connected to the support structure by the decoupling device.

[0011] In the present context, "mechanical decoupling" is understood to mean, in particular, that forces from the support structure to the optical element, or vice versa, cannot be transmitted, or at least can only be partially transmitted. Therefore, the decoupling device prevents, in particular, the transmission of undesired forces from the support structure to the optical element. This prevents undesirable deformations of the optical element or optically active surfaces. Specifically, the decoupling device prevents the transmission of parasitic forces from the support structure to the optical element. In the present context, "parasitic forces" are understood to include, for example, forces arising from thermally related differential expansion or contraction of components of the optical assembly.

[0012] Any desired number of decoupling devices may be provided. However, preferably, at least three decoupling devices are provided. However, four, five, or more such decoupling devices may also be provided. In the present case, the decoupling device being arranged "between" the optical element and the support structure specifically refers to the decoupling device being positioned between the rear side of the optical element and the front side of the support structure. Thus, the decoupling device is typically arranged within the optical assembly. However, the decoupling device may alternatively be arranged to the side or rear of the support structure.

[0013] According to an embodiment, the decoupling device is at least partially arranged in or on the optical element.

[0014] Preferably, the optical element comprises a plurality of recesses on its rear side, each recess being capable of being assigned a decoupling device. In particular, exactly one decoupling device is arranged or accommodated in each recess. Each recess has a base connected to the corresponding decoupling device. The decoupling device may protrude from these recesses in the direction of the support structure. In particular, this means that the decoupling device may also be arranged at least partially outside the optical element.

[0015] According to a further embodiment, the decoupling device is configured to mechanically decouple the optical element from the support structure axially and laterally.

[0016] Each coupling device is preferably assigned an axis of symmetry or a central axis, relative to which the decoupling device has a substantially rotationally symmetrical structure. In this context, "substantially" means that at least a portion of the decoupling device is rotationally symmetrical with respect to the central axis. In the present context, "axial" should be understood as along the aforementioned central axis. Thus, "transverse" refers to a direction perpendicular to the central axis or along a radial direction of the corresponding decoupling device. A radial direction is perpendicular to and away from the central axis.

[0017] According to a further embodiment, the rigidity of the support structure is greater than the rigidity of the optical element.

[0018] In this context, "rigidity" is understood to refer specifically to the resistance of a body (in this case, a support structure or optical element) to elastic deformation due to an external load. Rigidity provides a correlation between the load on the body and its deformation. Rigidity is determined by the material and geometry of the body. For example, given two geometrically identical bodies, the one whose material or substance has a higher Young's modulus has a greater rigidity. Thus, different rigidities of optical elements and support structures can be achieved through different geometries and / or by using different materials or substances.

[0019] According to a further embodiment, the support structure is made of a substance having a higher Young's modulus than the substance used to manufacture the optical element.

[0020] The support structure is particularly preferably made of a material that is more cost-effective than the optical element. This allows for cost-effective manufacture of the optical element. In particular, the optical element can be made of ultra-low expansion glass (ULE). However, other glass, glass-ceramic, ceramic, or metal materials can also be used for the optical element. For example, the support structure can be made of a metal material. For example, an iron-nickel alloy (particularly Invar) can be used for the support structure. However, non-metallic materials can also be used for the support structure. For example, the support structure can also be made of silicon carbide (SiSiC).

[0021] Each decoupling device comprises a first decoupling element and a second decoupling element connected to the first decoupling element, wherein the first decoupling element is connected to the optical element and the second decoupling element is connected to the support structure.

[0022] The first decoupling element and the second decoupling element can each be configured rotationally symmetrically with respect to the central axis of the corresponding decoupling device. The first decoupling element can be at least partially configured in an annular pattern. However, the first decoupling element can also be triangular. The second decoupling element can be bolt-shaped or rod-shaped. The first decoupling element is connected to the optical element without using an adhesive. For example, the decoupling element is bonded to the optical element. In particular, the first decoupling element can be bonded to the optical element in optical contact. Specifically, the first decoupling element is firmly connected to the bottom of the corresponding recess in the optical element. The second decoupling element can be welded, soldered and / or bonded to the support structure. The second decoupling element can also be fastened to the support structure using threads. The second decoupling element can be bonded to the first decoupling element.

[0023] According to a further embodiment, the first decoupling element is at least partially arranged in or on the optical element, wherein the second decoupling element is at least partially arranged outside the optical element.

[0024] The first decoupling element is particularly preferably disposed entirely within the optical element. The first decoupling element is housed in a corresponding recess in the optical element and is securely connected to the bottom of the recess. The second decoupling element protrudes from the recess in the direction of the support structure. However, the second decoupling element may be disposed at least partially within the optical element, in particular, at least partially within one of the plurality of recesses in the optical element.

[0025] According to a further embodiment, the optical element and the first decoupling element are made of the same substance.

[0026] Preferably, both the optical element and the decoupling element are made of ULE. However, other materials may also be used. Therefore, the optical element and the first decoupling element are made of the same material, and the optical element and the first decoupling element have the same coefficient of thermal expansion. Therefore, temperature changes do not cause mechanical stress in the optical element and / or the first decoupling element.

[0027] According to another embodiment, the first decoupling element and the second decoupling element are made of different materials.

[0028] Particularly preferably, the second decoupling element is made of a metal substance. For example, an iron-nickel alloy can be used for the second decoupling element. In particular, the second decoupling element can be made of Invar.

[0029] According to a further embodiment, the first decoupling element comprises a first connecting portion connected to the optical element and a second connecting portion connected to the second decoupling element.

[0030] The first connecting portion is preferably annular. However, the first connecting portion may also be triangular. The first connecting portion is firmly connected to the bottom of one of the multiple recesses in the optical element. The second connecting portion is centrally arranged within the first connecting portion. The second connecting portion does not contact the optical element. Specifically, a gap is provided between the bottom of the recess and the second connecting portion. The second connecting portion is movable relative to the first connecting portion fixed to the optical element, and the second connecting portion does not contact the optical element or the bottom of the corresponding recess. The second connecting portion is movable along the central axis of the decoupling device toward and away from the bottom of the recess in the optical element. In addition, the second connecting portion is capable of twisting around the central axis relative to the first connecting portion.

[0031] According to a further embodiment, the first connecting part is connected to the second connecting part by means of an elastically deformable decoupling arm.

[0032] Any desired number of decoupling arms can be provided. Particularly preferably, at least two decoupling arms are provided. However, three, four, five or more such decoupling arms can also be provided. In particular, the decoupling arms are elastically deformable. In the present case, a "flexibly deformable" or "elastically deformable" decoupling arm is understood to mean that, in particular, the decoupling arm can be brought from a non-deflected or non-deformed state into a deflected or deformed state by the application of a force or torque. Once the above-mentioned force or torque no longer acts on the decoupling arm, the decoupling arm independently or automatically changes from the deformed state back to the non-deformed state. The decoupling device is preferably rigid when considered along its central axis. A high axial rigidity of the connection between the optical element and the support structure is important for the first eigenmode of the optical system. In this case, "axial" means considered along the central axis of the decoupling device. However, axial compensation of deformations caused by volume changes of the adhesive used due to humidity and / or temperature changes is possible. The decoupling arm also allows the second connecting part to be twisted about the central axis relative to the first connecting part. The decoupling arm does not come into contact with the base of the recess in the optical element. In particular, this means providing a gap between the decoupling arm and the base. The first decoupling element is preferably a one-piece component, in particular a materially one-piece component. In this context, "one-piece" or "one component" means that the first connecting portion, the second connecting portion, and the decoupling arm are not formed from separate sub-components, but rather form a common component. "Materially one-piece" means that the first decoupling element is made entirely of the same material. For example, the first decoupling element is made of ULE.

[0033] According to a further embodiment, the decoupling arm extends from the first connecting portion at an angle to the second connecting portion.

[0034] In particular, "angled" should be understood to mean that the decoupling arm does not extend perpendicularly to the central axis of the decoupling device, but rather at an angle thereto. Specifically, the decoupling arm extends tangentially to the second connecting portion. This angled configuration of the decoupling arm enables rotational movement of the second connecting portion relative to the first connecting portion about the central axis. Furthermore, radial movement is also possible by bending the decoupling arm.

[0035] According to a further embodiment, the second decoupling element comprises at least one flexure.

[0036] As mentioned above, the second decoupling element is preferably cylindrical. The second decoupling element preferably comprises a first joining part connected to the second connecting part and a second joining part firmly connected to the support structure. The cylindrical base part is arranged between the two joining parts. The first joining part is connected to the base part via a first flexure. The second joining part is connected to the base part via a second flexure. Preferably, the second decoupling element is an integrally formed component, in particular a materially integral component. In the present case, "flexure" should in particular be understood to mean an area of ​​a component, in the present case an area of ​​the second decoupling element, which allows relative movement between two rigid areas by bending. In the present case, the first joining part and the base part serve as rigid areas of the first flexure. Therefore, the second joining part and the base part serve as rigid areas of the second flexure. The second decoupling element ensures lateral mechanical decoupling.

[0037] An optical system for a projection exposure apparatus is also proposed. The optical system comprises an optical component as described above and an adjustment device which is operatively connected to a support structure and serves to adjust the optical component.

[0038] The adjustment device preferably comprises a plurality of actuating elements or actuators capable of adjusting or aligning the optical component. The optical component has six degrees of freedom, specifically three translational degrees of freedom in each case along a first spatial direction or x-direction, a second spatial direction or y-direction, and a third spatial direction or z-direction, as well as three rotational degrees of freedom about the x-direction, the y-direction, and the z-direction. This means that the position and orientation of the optically active surface of the optical component or element can be determined or described using the six degrees of freedom.

[0039] Specifically, the "positioning" of an optical component should be understood to mean the coordinates of its coordinates or measurement points located on the optical component relative to the x-, y-, and z-directions. In particular, the "orientation" of an optical component should be understood to mean its tilt relative to these three directions. In other words, the optical component can be tilted about the x-, y-, and / or z-directions.

[0040] This results in six degrees of freedom in the position and orientation of the optically active surface of an optical component or element. The "pose" of an optical component encompasses both its position and orientation. Therefore, the term "pose" can be replaced by the term "position and orientation," and vice versa. In the present context, "adjustment" or "alignment" should be understood to refer specifically to a change in the pose of an optical component.

[0041] When the pose of an optical assembly changes, the optical component and its supporting structure move. For example, an adjustment device can be used to change the optically active surface of an optical assembly or element from an actual pose to a target pose, or vice versa. For example, the target pose may require that the optical assembly or surface meet certain optical specifications or requirements, which may not be met in the actual pose.

[0042] Furthermore, a projection exposure apparatus having such an optical component and / or such an optical system is proposed.

[0043] The optical system is preferably a projection optical unit of a projection exposure apparatus. However, the optical system may also be an illumination system. The projection exposure apparatus may be an EUV lithography apparatus. EUV stands for "extreme ultraviolet," meaning that the wavelength of the working light is between 0.1 nm and 30 nm. The projection exposure apparatus may also be a DUV lithography apparatus. DUV stands for "deep ultraviolet," meaning that the wavelength of the working light is between 30 nm and 250 nm.

[0044] In the present context, "a" or "an" or "an" is not necessarily to be construed as limiting only to one element. Rather, multiple elements, such as two, three, or more, may also be provided. Any other numerical values ​​used herein should not be construed as limiting the exact number of elements. On the contrary, numerical values ​​may deviate upwards and downwards unless otherwise indicated.

[0045] The embodiments and features described for the optical component apply correspondingly to the proposed optical system and / or the proposed projection exposure apparatus, and vice versa.

[0046] Other possible implementations of the present invention also encompass combinations not explicitly mentioned of features or embodiments described above or below with respect to exemplary embodiments. In this case, those skilled in the art will also add various aspects as improvements or supplements to the corresponding basic forms of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Advantageous further developments and aspects of the invention are the object of the dependent claims and of the exemplary embodiments of the invention described below.The invention will be explained in more detail below based on preferred embodiments with reference to the drawings.

[0048] Figure 1 shows a schematic meridional section through a projection exposure apparatus for EUV projection lithography;

[0049] Figure 2 Show the basis Figure 1 A schematic diagram of an embodiment of an optical system of a projection exposure apparatus;

[0050] Figure 3 Show the basis Figure 2 A schematic perspective view of an embodiment of an optical component of an optical system;

[0051] Figure 4 Show the basis Figure 3 A schematic rear view of the optical assembly of FIG.

[0052] Figure 5 Show the basis Figure 3 A schematic front view of an optical assembly;

[0053] Figure 6 Show the basis Figure 3 A schematic perspective view of an embodiment of a decoupling device for an optical component;

[0054] Figure 7 Show the basis Figure 6 A schematic perspective view of an embodiment of a decoupling element of a decoupling device;

[0055] Figure 8 Show the basis Figure 7 Schematic rear view of the decoupling element;

[0056] Figure 9 Show the basis Figure 7 A schematic front view of a decoupling element;

[0057] Figure 10 Show the basis Figure 6 Detailed view of the decoupling device; and

[0058] Figure 11 Show the basis Figure 6 Further detailed view of the decoupling device. DETAILED DESCRIPTION

[0059] Unless otherwise indicated, identical or functionally identical elements are provided with the same reference numerals in the figures. It should also be noted that the illustrations in the figures are not necessarily drawn to scale.

[0060] Figure 1 An embodiment of a projection exposure apparatus 1 (lithography apparatus), in particular an EUV lithography apparatus, is shown. One embodiment of an illumination system 2 of the projection exposure apparatus 1 comprises, in addition to a light or radiation source 3, an illumination optical unit 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a module separate from the rest of the illumination system 2. In this case, the illumination system 2 does not contain the light source 3.

[0061] A reticle 7 arranged in the object field 5 is exposed. The reticle 7 is held by a reticle carrier 8. The reticle carrier 8 can be displaced by a reticle displacement drive 9, in particular in a scanning direction.

[0062] For explanation purposes, Figure 1 A Cartesian coordinate system is shown with an x-direction x, a y-direction y, and a z-direction z. The x-direction x is perpendicular to the plane of the drawing. The y-direction y extends horizontally, and the z-direction z extends vertically. Figure 1 The scanning direction in FIG extends along the y-direction y. The z-direction z extends perpendicular to the object plane 6.

[0063] The projection exposure apparatus 1 comprises a projection optical unit 10. The projection optical unit 10 serves to image the object field 5 into an image field 11 in an imaging plane 12. The image plane 12 extends parallel to the object plane 6. Alternatively, the angle between the object plane 6 and the image plane 12 may also differ from 0°.

[0064] The structures on mask 7 are imaged onto the photosensitive layer of wafer 13, which is arranged in the region of image field 11 in image plane 12. Wafer 13 is held by wafer carrier 14. Wafer carrier 14 can be displaced, particularly in the y-direction y, by wafer displacement drive 15. Reticle 7 is displaced first by reticle displacement drive 9, and wafer 13 is displaced second by wafer displacement drive 15, in a manner synchronized with each other.

[0065] Light source 3 is an EUV radiation source. Light source 3 specifically emits EUV radiation 16, hereinafter also referred to as used radiation, illumination radiation, or illumination light. In particular, the wavelength of used radiation 16 is in the range between 0.1 nm and 30 nm. Light source 3 can be a plasma source, such as a laser-produced plasma (LPP) source or a gas-discharge-produced plasma (DPP) source. It can also be a synchrotron-based radiation source. Light source 3 can be a free-electron laser (FEL).

[0066] Illuminating radiation 16 emitted from light source 3 is focused by concentrator 17. Concentrator 17 can be a concentrator having one or more ellipsoidal and / or hyperbolic reflective surfaces. At least one reflective surface of concentrator 17 can be illuminated by illuminating radiation 16 with grazing incidence (GI), i.e., an angle of incidence greater than 45°, or with normal incidence (NI), i.e., an angle of incidence less than 45°. Concentrator 17 can be structured and / or coated to optimize its reflectivity for the radiation being used and to suppress extraneous light.

[0067] Downstream of the condenser 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 may represent a separation between the radiation source module (which has the light source 3 and the condenser 17) and the illumination optics unit 4.

[0068] The illumination optical unit 4 includes a deflecting mirror 19 and a first facet mirror 20 arranged downstream thereof in the beam path. The deflecting mirror 19 can be a planar deflecting mirror or, alternatively, a mirror having a beam-influencing effect that goes beyond a purely deflecting effect. Alternatively or additionally, the deflecting mirror 19 can be in the form of a spectral filter that separates the desired wavelength of the illumination radiation 16 from extraneous light that deviates from its wavelength. If the first facet mirror 20 is arranged in a plane of the illumination optical unit 4 that is optically conjugate to the object plane 6 and serves as a field plane, it is also referred to as a field facet mirror. The first facet mirror 20 includes a plurality of individual first facets 21, which can also be referred to as field facets. Figure 1 Only some of these first facets 21 are shown by way of example.

[0069] The first facets 21 can be implemented as macro facets, in particular rectangular facets or facets with an arcuate or partially circular edge profile.The first facets 21 can be in the form of planar facets or alternatively in the form of convex or concave curved facets.

[0070] As is known, for example, from DE 10 2008 009 600 A1, the first facets 21 themselves can also each be formed from a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirrors 20 can in particular be in the form of a microelectromechanical system (MEMS system). For more details, please refer to DE 10 2008 009 600 A1.

[0071] Between the condenser 17 and the deflecting mirror 19 , the illuminating radiation 16 propagates horizontally, ie in the y-direction y.

[0072] In the beam path of the illumination optical unit 4, the second facet mirror 22 is arranged downstream of the first facet mirror 20. If the second facet mirror 22 is arranged in the pupil plane of the illumination optical unit 4, it is also called a pupil facet mirror. The second facet mirror 22 can also be arranged at a certain distance from the pupil plane of the illumination optical unit 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also called a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1, EP 1 614 008 B1 and US 6,573,978.

[0073] The second facet mirror 22 comprises a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also called pupil facets.

[0074] The second facets 23 can also be a plurality of macro facets, which can have, for example, circular, rectangular or hexagonal boundaries, or alternatively facets consisting of micromirrors. In this respect, reference is also made to DE 10 2008 009 600 A1.

[0075] The second facet 23 may have a flat surface, or alternatively, a convexly or concavely curved reflecting surface.

[0076] The illumination optical unit 4 thus forms a double-sided system. This basic principle is also called a fly-eye condenser (or integrator).

[0077] It may be advantageous if the second facet mirror 22 is not arranged exactly in a plane optically conjugate to the pupil plane of the projection optical unit 10. In particular, the second facet mirror 22 can be arranged tilted relative to the pupil plane of the projection optical unit 10, as described, for example, in DE 10 2017 220 586 A1.

[0078] By means of a second facet mirror 22 the individual first facets 21 are imaged onto the object field 5 . The second facet mirror 22 is the last beam shaping mirror in the beam path upstream of the object field 5 or actually the last mirror of the illumination radiation 16 .

[0079] In a further embodiment (not shown) of the illumination optical unit 4, a transfer optical unit can be arranged in the beam path between the second facet mirror 22 and the object field 5 and in particular contribute to the imaging of the first facet 21 into the object field 5. The transfer optical unit can have exactly one mirror or, alternatively, two or more mirrors, which are arranged consecutively in the beam path of the illumination optical unit 4. The transfer optical unit can in particular comprise one or two normal incidence mirrors (NI mirrors) and / or one or two grazing incidence mirrors (GI mirrors).

[0080] exist Figure 1In the embodiment shown, the illumination optical unit 4 has exactly three mirrors downstream of the condenser 17 , specifically a deflection mirror 19 , a first facet mirror 20 and a second facet mirror 22 .

[0081] In a further embodiment of the illumination optical unit 4 , the deflection mirror 19 is also not required, so that the illumination optical unit 4 can have exactly two mirrors downstream of the condenser 17 , in particular a first facet mirror 20 and a second facet mirror 22 .

[0082] The imaging of the first facet 21 into the object plane 6 by means of the second facet 23 or using the second facet 23 and the transfer optical unit is usually only approximately performed.

[0083] The projection optical unit 10 comprises a plurality of mirrors Mi, which are numbered consecutively according to their arrangement in the beam path of the projection exposure apparatus 1 .

[0084] exist Figure 1 In the example shown, the projection optical unit 10 includes six mirrors M1 to M6. Alternatively, a number of four, eight, ten, twelve, or any other number of mirrors Mi is equally possible. The projection optical unit 10 is a double-blocking optical unit. The penultimate mirror M5 and the last mirror M6 each have a through-aperture for the irradiating radiation 16. The image-side numerical aperture of the projection optical unit 10 is greater than 0.5, and may also be greater than 0.6, and may be, for example, 0.7 or 0.75.

[0085] The reflective surface of the reflector Mi can be designed as a free-form surface without an axis of rotational symmetry. Alternatively, the reflective surface of the reflector Mi can be designed as an aspheric surface with exactly one axis of rotational symmetry of the reflective surface shape. Like the reflectors of the illumination optical unit 4, the reflector Mi can have a highly reflective coating for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

[0086] The projection optical unit 10 has a large object-image offset in the y-direction y between the y coordinate of the center of the object field 5 and the y coordinate of the center of the image field 11. This object-image offset in the y-direction y can have approximately the same magnitude as the z distance between the object plane 6 and the image plane 12.

[0087] The projection optical unit 10 can, in particular, have a deformable form. It can have different imaging ratios βx and βy in the x-direction x and the y-direction y. The two imaging ratios βx and βy of the projection optical unit 10 are preferably (βx, βy) = (+ / - 0.25, + / - 0.125). A positive imaging ratio β indicates an image without image inversion. A negative imaging ratio β indicates an image with image inversion.

[0088] The projection optical unit 10 thus results in a reduction in size in the x-direction x (ie in a direction perpendicular to the scanning direction) by a ratio of 4:1.

[0089] The projection optical unit 10 results in a reduction in the dimension in the y-direction y (ie the scanning direction) by a ratio of 8:1.

[0090] Other imaging ratios are also possible. Imaging ratios with the same sign and the same absolute value in the x-direction x and the y-direction y are also possible, for example with an absolute value of 0.125 or 0.25.

[0091] The number of intermediate image planes in the x-direction x and the y-direction y in the beam path between the object field 5 and the image field 11 may be the same or different, depending on the embodiment of the projection optical unit 10. Examples of projection optical units with a different number of such intermediate images in the x-direction x and the y-direction y are known from US 2018 / 0074303 A1.

[0092] In each case, exactly one of the second facets 23 is assigned to one of the first facets 21 in order to form an illumination channel for illuminating the object field 5. This can lead in particular to illumination according to the Köhler principle. The far field is decomposed into a plurality of object fields 5 by means of the first facets 21. The first facets 21 generate a plurality of images of the intermediate focus on the second facets 23 respectively assigned thereto.

[0093] The first facets 21 are imaged onto the reticle 7 in each case overlapping one another via the assigned second facets 23 to illuminate the object field 5. The illumination of the object field 5 is particularly uniform as much as possible. Its uniformity error is preferably less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

[0094] The illumination of the entrance pupil of the projection optical unit 10 can be geometrically defined by the configuration of the second facets 23. The intensity distribution in the entrance pupil of the projection optical unit 10 can be set by selecting the illumination channels, in particular the subset of the second facets 23 that guide the light. This intensity distribution is also referred to as the illumination setting or the illumination pupil filling.

[0095] A likewise preferred pupil homogeneity in a subregion of the illumination pupil (illuminated in a defined manner) of the illumination optical unit 4 can be achieved by redistribution of the illumination channels.

[0096] Further aspects and details of the illumination of the object field 5 and in particular of the entrance pupil of the projection optical unit 10 are described below.

[0097] In particular, the projection optical unit 10 may comprise a concentric entrance pupil. The concentric entrance pupil may be accessible. It may also be inaccessible.

[0098] Typically, the entrance pupil of the projection optical unit 10 cannot be precisely illuminated using the second facet mirror 22. When imaging the projection optical unit 10 onto the wafer 13 by telecentrically imaging the center of the second facet mirror 22, the aperture rays typically do not intersect at a single point. However, a region can be found where the separation between pairs of aperture rays is minimized. This region represents the entrance pupil or a region in real space conjugate thereto. In particular, this region has a finite curvature.

[0099] It is possible that the projection optical unit 10 has different entrance pupil poses for the tangential and sagittal beam paths. In this case, an imaging element (in particular, an optical component of the transfer optical unit) should be arranged between the second facet mirror 22 and the reticle 7. This optical element can be used to account for the different poses of the tangential and sagittal entrance pupils.

[0100] exist Figure 1 In the illustrated arrangement of the components of the illumination optical unit 4, the second facet mirror 22 is arranged in a region conjugate with the entrance pupil of the projection optical unit 10. The first facet mirror 20 is arranged to be tilted relative to the object plane 6. The first facet mirror 20 is arranged to be tilted relative to the arrangement plane defined by the deflection mirror 19. The first facet mirror 20 is arranged to be tilted relative to the arrangement plane defined by the second facet mirror 22.

[0101] Figure 2 A schematic diagram of an embodiment of an optical system 100 for a projection exposure apparatus 1 is shown.

[0102] The optical system 100 can be part of the projection optical unit 10 as described above. However, the optical system 100 can also be part of the illumination optical unit as described above. However, it is assumed below that the optical system 100 is part of this type of projection optical unit 10. The optical system 100 is suitable for EUV lithography. However, the optical system 100 can also be suitable for DUV lithography.

[0103] Optical system 100 includes an optical assembly 102. Optical assembly 102 may be a reflector or include a reflector. For example, optical assembly 102 is one of reflectors M1 to M6. Optical assembly 102 may also be referred to as a reflector module. Optical assembly 102 includes an optical element 104. Optical element 104 may be a reflector.

[0104] In addition to the optical element 104, the optical assembly 102 further includes a support structure 106 that carries the optical element 104. The optical element 104 is coupled to the support structure 106. The type of coupling between the optical element 104 and the support structure 106 will be explained further below.

[0105] Optical element 104 is made of glass, glass ceramic, or the like. Specifically, optical element 104 can be made of ultra-low expansion glass (ULE). The material used to make support structure 106 is different from the material used to make optical element 104. Specifically, the material of support structure 106 has a higher Young's modulus than the material of optical element 104. Support structure 106 is preferably made of a material that is more cost-effective than optical element 104. Consequently, optical assembly 102 can be manufactured cost-effectively.

[0106] Support structure 106 has greater rigidity than optical element 104. In this context, "rigidity" should be understood to refer specifically to the body's resistance to elastic deformation due to external loads. Rigidity provides a correlation between the load on the body and its deformation. Rigidity is determined by the material and geometry of the body.

[0107] For example, in the case of two geometrically identical bodies, the body whose material used to make the respective bodies has a higher Young's modulus has a greater stiffness. Thus, different stiffnesses of the optical element 104 and the support structure 106 can be achieved by different geometries and / or by using different materials or substances.

[0108] The optical component 102 or the optical element 104 has six degrees of freedom, specifically, three degrees of freedom of translation in each case along a first spatial direction or x-direction x, a second spatial direction or y-direction y, and a third spatial direction or z-direction z, and three degrees of freedom of rotation relative to the x-direction x, the y-direction y, and the z-direction z. In other words, the position and orientation of the optical component 102 or the optical element 104 can be determined or described using the six degrees of freedom.

[0109] The “position” of the optical component 102 or the optical element 104 is specifically understood to mean its coordinates or the coordinates of a measuring point arranged on the optical component 102 relative to the x-direction x, the y-direction y and the z-direction z.

[0110] The “orientation” of the optical component 102 or optical element 104 is understood to particularly refer to its tilt relative to the three directions x, y, z. That is, the optical component 102 or optical element 104 can be tilted about the x-direction x, the y-direction y and / or the z-direction z.

[0111] This results in six degrees of freedom for the position and orientation of the optical component 102 or optical element 104. The "pose" of the optical component 102 or optical element 104 includes both its position and orientation. Therefore, the term "pose" can be replaced by the term "position and orientation" and vice versa.

[0112] Figure 2The actual posture IL of the optical assembly 102 or optical element 104 is shown using a solid line, and the target posture SL of the optical assembly 102 or optical element 104 is shown using a dashed line and reference numerals 102' and 104'. The actual posture IL of the support structure 106 coupled to the optical element 104 is also depicted using a solid line. The target posture SL of the support structure 106 is depicted using a dashed line and reference numeral 106'.

[0113] The optical assembly 102 may be moved from its actual pose IL to a target pose SL, and vice versa. For example, the optical assembly 102 or optical element 104 in the target pose SL meets certain optical specifications or requirements that the optical assembly 102 or optical element 104 does not meet in the actual pose IL.

[0114] In order to move the optical component 102 from the actual posture IL to the target posture SL, the optical system 100 includes an adjustment device 108. The adjustment device 108 is configured to adjust the optical component 102. In the present case, "adjustment" or "alignment" should be understood to specifically refer to a change in the posture of the optical component 102. When the posture of the optical component 102 changes, the optical element 104 moves together with the support structure 106.

[0115] For example, the optical component 102 can be moved from the actual position IL to the target position SL, and vice versa, by means of the adjustment device 108. Thus, the optical component 102 can be adjusted or aligned in all six degrees of freedom described above by means of the adjustment device 108. The adjustment device 108 is a so-called hexapod mechanism or the like.

[0116] The regulating device 108 includes a plurality of actuators 110, 112, 114. Figure 2 1 is shown only highly schematically. The actuators 110, 112, 114 may also be referred to as actuator systems or actuator elements. The actuators 110, 112, 114 may be so-called bipods or the like. Preferably, exactly three actuators 110, 112, 114 are provided, which are arranged offset by 120° relative to one another. The actuators 110, 112, 114 preferably have the same design.

[0117] The actuators 110, 112, 114 are connected to the support structure 106 by means of joints 116. Figure 2 Only one of them has a reference number. For example, an adhesive connection or a screw connection can be provided at one of the joints 116. Preferably, exactly three joints 116 are provided, each of which is assigned an actuator 110, 112, 114.

[0118] Furthermore, each actuator 110, 112, 114 is coupled to a fixed region 122 via two joints 118, 120. Figure 2Only two connection points have reference numbers.The fixed area 122 may be a force frame or any other immovable structure.

[0119] With the aid of actuators 110, 112, 114, the optical assembly 102 can be moved relative to the fixed area 122. Each actuator 110, 112, 114 can be allocated two of the above-mentioned degrees of freedom. Using three actuators 110, 112, 114, it is thus possible to achieve adjustment of the optical assembly 102 in all six degrees of freedom.

[0120] The actuators 110, 112, 114 can be controlled by means of an open-loop and closed-loop control unit 124 of the adjustment device 108 to adjust the optical assembly 102. All actuators 110, 112, 114 are operatively connected to the open-loop and closed-loop control unit 124, so that the open-loop and closed-loop control unit 124 can adjust the optical assembly 102 in all six degrees of freedom by means of appropriate control of these actuators 110, 112, 114. This can be implemented based on sensor signals from a sensor system (not described here) that is capable of detecting an actual posture IL and a target posture SL of the optical assembly 102.

[0121] Figure 3 A schematic perspective view of the optical assembly 102 is shown. Figure 4 A schematic rear view of the optical assembly 102 is shown. Figure 5 1 shows a schematic plan view of the optical assembly 102. Figures 3 to 5 .

[0122] Figures 3 to 5 The support structure 106 is not shown in FIG. The optical element 104 comprises a rear side 126 facing the support structure 106 and an optically active surface 128 facing away from the rear side 126. The optically active surface 128 is a reflective surface. The optically active surface 128 is suitable for reflecting the illumination radiation 16. The optically active surface 128 can be realized by a coating.

[0123] A plurality of depressions or recesses 130 are provided on the rear side 126. Figure 3 and Figure 4 Only one recess is designated by a reference number. Any desired number of recesses 130 may be provided. For example, 19 recesses 130 may be provided. The recesses 130 may be arranged in a grid or pattern. In the present context, "grid" or "pattern" specifically refers to the recesses 130 being arranged in columns and rows. The recesses 130 may be offset from one another.

[0124] The recesses 130 may be circular. However, in principle, the recesses 130 may have any desired geometric shape. For example, the recesses 130 may be elliptical, rectangular, or hexagonal. Each recess 130 includes a base 132. The base 132 is set back relative to the rear side 126 of the optical element 104.

[0125] A decoupling device 134 is housed in each recess 130. That is, the number of decoupling devices 134 corresponds to the number of recesses 130. The decoupling device 134 is coupled to the base 132 of the recess 130. Only one decoupling device 134 will be discussed in more detail below.

[0126] Figure 6 A schematic perspective view of an embodiment of a decoupling element 134 as described above is shown. Figure 7 A schematic perspective view of an exemplary embodiment of a first decoupling element 136 for a decoupling device 134 is shown. Figure 8 A schematic rear view of the first decoupling element 136 is shown. Figure 9 A schematic front view of the first decoupling element 136 is shown. Figure 10 A schematic detailed view of the decoupling device 134 is shown. Figure 11 A further schematic detailed view of the decoupling device 134 is shown. Figures 6 to 11 .

[0127] The coupling device 134 is preferably assigned an axis of symmetry or a central axis 138 , relative to which the decoupling device 134 has a substantially rotationally symmetrical structure. The decoupling device 134 is also assigned a radial direction R. The radial direction R is oriented perpendicular to the central axis 138 and away from the central axis.

[0128] Decoupling device 134 includes a first decoupling element 136, preferably in the form of a ring, and a second decoupling element 140, preferably in the form of a rod. Decoupling elements 136 and 140 are connected to one another. First decoupling element 136 is connected to optical element 104. Second decoupling element 140 is coupled to support structure 106. Thus, optical element 104 and support structure 106 are operatively connected to one another by means of decoupling device 134.

[0129] The first decoupling element 136 is made of the same material as the optical element 104. For example, the first decoupling element 136 can be made of ULE. The second decoupling element 140 is made of a material different from the material used to make the first decoupling element 136. For example, the second decoupling element 140 is made of a metal material, such as an iron-nickel alloy, particularly Invar.

[0130] The first decoupling element 136 comprises an annular first connecting portion 142. However, in principle, the first connecting portion 142 can have any desired geometric shape. For example, the first connecting portion 142 can be triangular or rectangular.

[0131] First connecting portion 142 has a front side 144 facing toward base 132 of corresponding recess 130, and a rear side 146 facing away from front side 144. Front side 144 is annular. First connecting portion 142 is connected to base 132 via front side 144. An adhesive-free joining method is employed for this purpose. Thus, front side 144 and base 132 are bonded to each other.

[0132] For example, an optical contact joint is used to connect the front side 144 of the first decoupling element 136 to the substrate 132. Furthermore, a welded connection can be provided between the first decoupling element 136 and the optical element 104. The first decoupling element 136 can also be formed integrally with the optical element 104, in particular, integrally formed in terms of material. In the present case, "integral piece" or "one component" particularly means that the first decoupling element 136 and the optical element 104 do not consist of different subcomponents, but rather form a common component. In particular, "integral in terms of material" means that the first decoupling element 136 and the optical element 104 are always made of the same material (e.g., ULE).

[0133] The second connecting portion 148 is arranged within the first connecting portion 142. The second connecting portion 148 is arranged centrally within the first connecting portion 142. The first connecting portion 142 and the second connecting portion 148 are connected to each other by means of decoupling arms 150, 152, 154.

[0134] Any desired number of decoupling arms 150, 152, 154 may be present. For example, exactly three decoupling arms 150, 152, 154 may be provided. Openings 156, 158, 160 are provided between the decoupling arms 150, 152, 154. Rather than extending centrally toward the central axis 138, the decoupling arms 150, 152, 154 are arranged at an angle relative to the central axis. This allows the second connecting portion 148 to twist relative to the first connecting portion 142. The decoupling arms 150, 152, 154 deform in the process.

[0135] The decoupling arms 150, 152, 154 are elastically deformable, and in particular, flexibly deformable. Specifically, this means that the decoupling arms 150, 152, 154 can be moved from a non-deflected or non-deformed state to a deflected or deformed state by applying a force or torque. Once the force or torque is no longer applied, the decoupling arms 150, 152, 154 independently or automatically return from the deformed state to the non-deformed state.

[0136] First decoupling element 136 is a one-piece component, in particular a materially one-piece component. In the present case, "one piece" or "one component" specifically means that the two connecting parts 142, 148 and the decoupling arms 150, 152, 154 do not consist of different subcomponents, but rather form a common component, in particular, first decoupling element 136. In particular, "materially one-piece" means that first decoupling element 136 is always made of the same material (e.g., ULE).

[0137] Second connecting portion 148 and decoupling arms 150, 152, 154 form a common front side 162. Front side 162 is set back relative to front side 144 connected to base 132, thereby providing a gap between front side 162 and base 132. Specifically, this means that decoupling arms 150, 152, 154 do not contact base 132. Therefore, decoupling arms 150, 152, 154 can deform freely without colliding with base 132.

[0138] The first connecting part 142, the second connecting part 148 and the decoupling arms 150, 152, 154 form a common rear side 146 facing away from the front side 162. On the rear side 146, a joining region 164 is centrally arranged on the second connecting part 148. The second connecting part 148 is connected to the second decoupling element 140, for example, by means of the joining region 164, by adhesive bonding. The joining region 164 can be an adhesive point.

[0139] The second decoupling element 140 (such as Figure 10 and Figure 11 The second decoupling element 140 is substantially rotationally symmetrical with respect to the central axis 138 (shown). The second decoupling element 140 has a disk-shaped first connection portion 166, which is connected to the second connection portion 148 on the rear side 146, in particular by adhesive bonding. The first connection portion 166 is adhesively bonded to the connection region 164.

[0140] In addition to the first engagement portion 166, the second decoupling element 140 further comprises a dish-shaped second engagement portion 168, which is firmly connected to the support structure 106, in particular to a front side 170 of the support structure 106 facing the optical element 104. An adhesive connection may be provided. Alternatively, the second engagement portion 168 may be welded or soldered to the front side 170.

[0141] A cylindrical base portion 172 is disposed between the two engagement portions 166, 168. The first engagement portion 166 is connected to the base portion 172 by a first flexure 174. The second engagement portion 168 is connected to the base portion 172 by a second flexure 176.

[0142] The second decoupling element 140 is a one-piece component, in particular a one-piece component in terms of material. In particular, this means that the joining portions 166, 168 and the base portion 172 form a common component, in particular the second decoupling element 140. In this process, the second decoupling element 140 can be made entirely of the same substance.

[0143] In the present case, the term "flexure" is understood to mean a region of a component, in this case, a region of second decoupling element 140, that allows relative movement between two rigid regions by bending. In the present case, first joint portion 166 and base portion 172 serve as the rigid region of first flexure 174. Consequently, second joint portion 168 and base portion 172 serve as the rigid region of second flexure 176.

[0144] Both radial and lateral decoupling are possible with the decoupling device 134. "Axial" refers to the direction along the central axis 138. In the present case, "radial" refers to the direction along and against the radial direction R or perpendicular to the central axis 138. Radial decoupling is implemented with the aid of the second decoupling element 140 or with the aid of flexures 174, 176.

[0145] Axial decoupling is achieved by elastically deformable decoupling arms 150, 152, 154. Decoupling arms 150, 152, 154 allow twisting of second connection portion 148 relative to first connection portion 142 and movement of second connection portion 148 along central axis 138 toward and away from substrate 132. Decoupling is possible because first decoupling element 136 is recessed into one of recesses 130, immediately below optically active surface 128 of optical element 104.

[0146] The joining region 164 (in which the adhesive is provided for interconnecting the first decoupling element 136 and the second decoupling element 140) is mechanically decoupled from the optical element 104 by means of the decoupling arms 150, 152, 154. Therefore, parasitic forces generated by curing, crosslinking, or aging of the adhesive, as well as changes in its volume associated with moisture and / or temperature, cannot be transmitted to the optical element 104. This reliably prevents undesirable deformations of the optically active surface 128.

[0147] The optical assembly 102 preferably includes at least three decoupling devices 134. However, four, five, or more decoupling devices 134 may be provided. Increasing the number of decoupling devices 134 increases the rigidity of the optical assembly 102 and allows for higher frequencies of the optical assembly 102. The first decoupling element 136 provides axial decoupling along the central axis 138. Lateral decoupling is provided by the flexures 174 and 176 of the second decoupling element 140.

[0148] Although the present invention has been described based on exemplary embodiments, the present invention can be modified in various ways.

[0149] Reference Signs List

[0150] 1 Projection exposure equipment

[0151] 2 Lighting system

[0152] 3 Light Source

[0153] 4 Illumination optical unit

[0154] 5 Material Field

[0155] 6 Object Plane

[0156] 7 Reticle Master

[0157] 8 Reticle carrier

[0158] 9 Reticle displacement driver

[0159] 10 Projection optics unit

[0160] 11 Image Field

[0161] 12 Image plane

[0162] 13 chips

[0163] 14 Wafer carrier

[0164] 15 Chip displacement driver

[0165] 16 Illumination Radiation

[0166] 17 Condenser

[0167] 18 Intermediate focal plane

[0168] 19 Deflecting mirror

[0169] 20 First facet mirror

[0170] 21 First facet

[0171] 22 Second facet mirror

[0172] 23 Second facet

[0173] 100 Optical System

[0174] 102 Optical Components

[0175] 102' Optical Components

[0176] 104 optical components

[0177] 104' Optical Components

[0178] 106 Support Structure

[0179] 106' support structure

[0180] 108 Adjustment device

[0181] 110 actuator

[0182] 112 Actuator

[0183] 114 actuator

[0184] 116 junctions

[0185] 118 junctions

[0186] 120 junctions

[0187] 122 Fixed Area

[0188] 124 Open-loop and closed-loop control units

[0189] 126 rear side

[0190] 128 optically effective surfaces

[0191] 130 recess

[0192] 132 base

[0193] 134 Decoupling device

[0194] 136 Decoupling element

[0195] 138 Central Axis

[0196] 140 Decoupling element

[0197] 142 connection part

[0198] 144 front

[0199] 146 rear side

[0200] 148 connection part

[0201] 150 Decoupling arm

[0202] 152 Decoupling arm

[0203] 154 Decoupling arm

[0204] 156 Opening

[0205] 158 Opening

[0206] 160 Opening

[0207] 162 front

[0208] 164 Joint Area

[0209] 166 joint part

[0210] 168 joint part

[0211] 170 front

[0212] 172 base part

[0213] 174 flexures

[0214] 176 flexure

[0215] IL actual posture

[0216] M1 reflector

[0217] M2 reflector

[0218] M3 reflector

[0219] M4 reflector

[0220] M5 reflector

[0221] M6 reflector

[0222] R Radial

[0223] SL Target Posture

[0224] x x-direction

[0225] y y-direction

[0226] z z-direction

Claims

1. An optical assembly (102) for a projection exposure apparatus (1), comprising: Optical element (104); a support structure (106) supporting the optical element (104); as well as a plurality of decoupling devices (134) disposed between the optical element (104) and the support structure (106) to mechanically decouple the optical element (104) from the support structure (106); Each decoupling device (134) includes a first decoupling element (136) and a second decoupling element (140) connected to the first decoupling element (136); The first decoupling element (136) is connected to the optical element (104); and The second decoupling element (140) is connected to the support structure (106).

2. The optical assembly of claim 1, wherein: The decoupling device (134) is at least partially arranged in the optical element (104) or on the optical element (104).

3. The optical assembly of claim 2, wherein: The decoupling device (134) is configured to mechanically decouple the optical element (104) from the support structure (106) axially and laterally.

4. The optical component according to any one of claims 1 to 3, wherein: The support structure (106) has a stronger rigidity than the optical element (104).

5. The optical component according to any one of claims 1 to 4, wherein: The support structure (106) is made of a material having a higher Young's modulus than the material used to make the optical element (104).

6. The optical component according to any one of claims 1 to 5, wherein: The first decoupling element (136) is at least partially disposed within or on the optical element (104); and wherein the second decoupling element (140) is at least partially disposed outside the optical element (104).

7. The optical assembly according to any one of claims 1 to 6, wherein: The optical element (104) and the first decoupling element (136) are made of the same material.

8. The optical assembly according to any one of claims 1 to 7, wherein: The first decoupling element (136) and the second decoupling element (140) are made of different materials.

9. The optical assembly according to any one of claims 1 to 8, wherein: The first decoupling element (136) includes a first connecting portion (142) connected to the optical element (104) and a second connecting portion (148) connected to the second decoupling element (140).

10. The optical assembly of claim 9, wherein: The first connecting portion (142) is connected to the second connecting portion (148) by means of elastically deformable decoupling arms (150, 152, 154).

11. The optical assembly of claim 10, wherein: The decoupling arms (150, 152, 154) extend from the first connecting portion (142) at an angle to the second connecting portion (148).

12. The optical assembly according to any one of claims 1 to 11, wherein: The second decoupling element (140) includes at least one flexure (174, 176).

13. An optical system (100) for a projection exposure apparatus (1), comprising: The optical component (102) according to any one of claims 1 to 12; as well as An adjustment device (108) is operably connected to the support structure (106) and is used to adjust the optical assembly (102).

14. A projection exposure apparatus (1) comprising an optical component (102) according to any one of claims 1 to 12 and / or an optical system (100) according to claim 13.

Images