Optical system, projection optical unit, and projection exposure system

Abstract

The invention relates to an optical system (100) for a projection exposure system (1), having an optical element (104, 106, 108); a mount (132) which supports the optical element (104, 106, 108), the mount (132) having a displacement device (138) which is configured so as to displace the optical element (104, 106, 108) linearly along exactly one spatial direction (152, 154, 156) in the event of a heat-induced change in the shape of the mount (132), and the displacement device (138) having at least one contact portion (142, 144) which is attached to the mount (132) and against which the optical element (104, 106, 108) bears; and a spring element (140) which displaces the optical element (104, 106, 108) along the spatial direction (152, 154, 156) in the event of the heat-induced change in the shape of the mount (132).

Description

[0001] Carl Zeiss SMT GmbH

[0002] 1

[0003] OPTICAL SYSTEM, PROJECTION OPTICS AND

[0004] PROJECTION LIGHTING SYSTEM

[0005] The present invention relates to an optical system, a projection optics with such an optical system and a projection exposure system with such an optical system and / or such a projection optics.

[0006] The content of priority application DE 10 2024 210 379.9 is fully incorporated by reference.

[0007] Microlithography is used to manufacture microstructured components, such as integrated circuits. The microlithography process is carried out using a lithography system, which includes an illumination system and a projection system. The image of a mask (reticule) 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 onto the photosensitive coating of the substrate.

[0008] Driven by the pursuit of ever smaller structures in the production of integrated circuits, EUV lithography systems are currently being developed that use light with a wavelength in the range of 0.1 nm to 30 nm, particularly 13.5 nm. Since most materials absorb light of this wavelength, such EUV lithography systems must use reflective optics, i.e., mirrors, instead of the refracting optics, i.e., lenses, used previously. Carl Zeiss SMT GmbH

[0009] 2

[0010] In such projection systems, so-called heating heads or mirror preheaters can be used to bring the mirrors up to operating temperature more quickly, which serves to reduce the time until the substrate is exposed and thus increase the productivity of the lithography system.

[0011] Such heating heads may contain optical elements, particularly lenses, which can move freely within their mountings. When such a heating head heats up during operation, these optical elements can experience thermal drift, resulting in a so-called "deployment error" on the mirror being heated. This means that the radiation generated by the heating head, especially infrared radiation, does not fall on the mirror at a designated point, but rather this point shifts undefined across the mirror. This phenomenon needs to be corrected.

[0012] Against this background, one object of the present invention is to provide an improved optical system.

[0013] Accordingly, an optical system for a projection exposure system is proposed. The optical system comprises an optical element and a mount that supports the optical element, wherein the mount has a displacement device configured to displace the optical element linearly along exactly one spatial direction in the event of a heat-induced deformation of the mount, and wherein the displacement device has at least one mounting section attached to the mount against which the optical element rests, and a spring element which displaces the optical element along the spatial direction in the event of a heat-induced deformation of the mount. Carl Zeiss SMT GmbH

[0014] 3

[0015] Furthermore, an optical system for a projection exposure system is proposed. The optical system comprises an optical element and a mount that supports the optical element, the mount having a displacement direction configured to displace the optical element linearly along exactly one spatial direction in the event of a heat-induced deformation of the mount.

[0016] Because the displacement mechanism moves the optical element linearly along precisely one spatial direction, it can be ensured that the optical element can only move in a defined manner along this spatial direction when the mount deforms due to heat. This defined movement can be taken into account in the design of the optical system in such a way that even if heat is introduced into the optical system, no misalignment error of the previously mentioned kind occurs. In particular, this can be achieved by arranging several optical elements consecutively in such a way that the spatial directions of the displacement mechanisms of the optical elements differ from one another. This allows heat-induced deformations of the mounts of the optical elements to be compensated for.

[0017] The optical system is preferably a heating head or a so-called mirror preheater, or part of such a heating head. However, the optical system can also be a projection optic of the projection exposure system or part of such a projection optic. Furthermore, the optical system can also be an illumination system of the projection exposure system or part of such an illumination system. In the following, however, it is assumed that the optical system is a heating head or part of a heating head. In particular, the optical system can be used for EUV lithography. However, the optical system can also be used for DUV lithography. The optical system can have any number of optical elements. In the following, however, only one optical element will be discussed. Carl Zeiss SMT GmbH

[0018] 4

[0019] The optical element is preferably a lens. However, the optical element can also be a mirror, in particular an EUV mirror. The optical element is mounted in the housing. The fact that the housing "carries" the optical element means, in this case, in particular that the housing absorbs the weight of the optical element. The optical element can be connected to the housing. However, the optical element can move relative to the housing with the aid of the displacement device. This movement of the optical element, however, only occurs along the single spatial direction assigned to the displacement device.

[0020] The displacement device is, in particular, part of the mount. When heat is applied to the mount, the mount preferably expands more than the optical element, so that the displacement device follows the heat-induced deformation or expansion of the mount. The single spatial direction of movement can be arbitrarily oriented. However, it is always ensured that the optical element moves only along this single spatial direction when the mount deforms due to heat. This means, in particular, that the displacement device is exclusively assigned to one spatial direction. Movement of the optical element in multiple spatial directions is preferably excluded.

[0021] The optical system preferably has an optical axis that extends along a beam path of the optical system. Radiation, in particular infrared radiation, follows the beam path through the optical system. The spatial direction is in particular perpendicular to the optical axis. The radiation introduces heat into the optical system, in particular into the optical element and the mount. This heat leads to the heat-induced deformation of the mount. In particular, the Carl Zeiss SMT GmbH

[0022] 5

[0023] The version is affected by the heat input. The radiation is preferentially generated by the optical system.

[0024] According to one embodiment, the displacement device has at least one mounting section attached to the socket, against which the optical element rests, and a spring element which displaces the optical element along the spatial direction during the heat-induced deformation of the socket.

[0025] The repositioning device has at least one mounting section. Preferably, however, the repositioning device has several mounting sections. For example, exactly two mounting sections may be provided. The spring element ensures that the optical element always rests against the at least one mounting section, even when the mount deforms due to heat. For this purpose, the spring element pre-tensions the optical element against the at least one mounting section. The spring element can apply a compressive force to the optical element for this purpose. The mounting section and the mount are preferably formed in one piece, in particular as a single piece of material. "One piece" or "one-part" in this context means, in particular, that the at least one mounting section and the mount form a single component, namely the mount, and are not composed of different sub-components."Made from a single piece of material" in this context means, in particular, that the socket and at least one section of the assembly are manufactured entirely from the same material. The spring element is, in particular, a compression spring.

[0026] According to a further embodiment, the displacement device has a first mounting section and a second mounting section, with the spring element arranged between the first mounting section and the second mounting section. Carl Zeiss SMT GmbH

[0027] 6

[0028] In this case, the relocation device has exactly two sections. The optical element is in contact with both the first and second sections simultaneously. The spring element ensures that the optical element is always pressed against both the first and second sections.

[0029] According to a further embodiment, the first attachment section, the second attachment section and the spring element are arranged evenly distributed around an optical axis of the optical system, wherein the first attachment section, the second attachment section and the spring element are in particular arranged offset from each other by 120°.

[0030] The first assembly section, the second assembly section, and the spring element can also be arranged at different angles to each other around the optical axis. As mentioned previously, one spatial direction of the displacement device is preferably oriented perpendicular to the optical axis.

[0031] According to another embodiment, the first system section and the second system section each have a curved contact surface against which the optical element rests.

[0032] The first section of the system is specifically assigned a first support surface. Similarly, the second section of the system is specifically assigned a second support surface. The support surfaces are curved, preferably arc-shaped or circular arcs. However, the support surfaces can have any three-dimensional geometry. Carl Zeiss SMT GmbH

[0033] 7 According to another embodiment, the spring element is arranged between the socket and the optical element.

[0034] Preferably, the mount has a receiving opening in which the optical element is received. A gap is provided between the optical element and the mount. The spring element is preferably arranged within this gap. The spring element can be clamped between the mount and the optical element. The spring element is pre-tensioned such that it presses the optical element against the two contact sections.

[0035] According to another embodiment, the spring element is a leaf spring.

[0036] The spring element can be any type of spring. For example, it could be a disc spring assembly, a cylindrical spring, or something similar. However, it is preferably always a compression spring.

[0037] According to another embodiment, the optical element is a lens.

[0038] However, the optical element can also be a mirror.

[0039] According to another embodiment, the socket has a receiving opening in which the optical element is received, so that a beam path of the optical system passes through the socket.

[0040] In other words, the opening completely penetrates the camera body. The radiation generated by the optical system, particularly infrared radiation, follows the beam path through the optical system. The radiation thus passes through the opening. The optical axis also preferably runs through the opening. Carl Zeiss SMT GmbH

[0041] 8

[0042] According to another embodiment, the optical system has several optical elements, each optical element being assigned a socket with a displacement device.

[0043] The number of optical elements is arbitrary. Preferably, each optical element has its own mount with its own displacement mechanism. Alternatively, only certain optical elements may each have a mount with a displacement mechanism. Preferably, the optical elements are arranged one behind the other along the optical axis of the optical system, so that the radiation passes through the optical elements sequentially.

[0044] According to another embodiment, each displacement device is assigned a spatial direction, with the spatial directions being different from each other.

[0045] The spatial directions of the individual displacement devices can, for example, be oriented in opposite directions. Furthermore, it is also possible for the spatial directions to be oriented at a certain angle to each other, for example, at an angle of 90°. The spatial directions can also be arranged obliquely to each other. However, the spatial directions are preferably always oriented perpendicular to the optical axis.

[0046] According to another embodiment, the spatial directions are oriented in such a way that a placement point of the optical system is unaffected by a heat-induced change in the shape of the mounts.

[0047] With the help of the optical system, the radiation generated by the optical system, especially infrared radiation, is directed onto a mirror in order to be focused locally. Carl Zeiss SMT GmbH

[0048] 9

[0049] Heat is introduced into this system. The radiation strikes an optically effective surface of the mirror at a defined point of impact. If the optical system lacks the previously mentioned displacement device(s), this point of impact can shift undesirably, deviating from its intended position. By appropriately orienting the displacement devices, the point of impact remains unchanged even if the different mounts deform due to heat. The radiation is thus directed so that it always strikes the mirror at the intended point of impact. This reliably prevents misalignment.

[0050] According to another embodiment, the optical element is made of a material with a first coefficient of thermal expansion, wherein the housing is made of a material with a second coefficient of thermal expansion, and wherein the second coefficient of thermal expansion is greater than the first coefficient of thermal expansion.

[0051] For example, the optical element can be made of glass. The mount can be made of a metallic material, such as stainless steel. When heat is applied simultaneously to both the optical element and the mount, the mount expands more than the optical element. The displacement mechanism ensures that the optical element moves within the mount only along the defined spatial direction of the displacement mechanism.

[0052] Furthermore, a projection optic for a projection exposure system is proposed. The projection optic comprises a mirror and such an optical system, wherein the optical system is configured to supply heat to the mirror by means of radiation, in particular infrared radiation. Carl Zeiss SMT GmbH

[0053] 10

[0054] In this case, the optical system is a heating head used to selectively heat a mirror within the projection optics. The projection optics can contain any number of mirrors. The optical system can also be such a projection optics system or part of such a system. In this case, the mount with the integrated displacement mechanism for an optical element in the form of a mirror is used.

[0055] Furthermore, a projection exposure system with such an optical system and / or such projection optics is proposed.

[0056] The projection exposure system can be an EUV lithography system. "EUV" stands for "Extreme Ultraviolet" and refers to a wavelength of the working light between 0.1 nm and 30 nm. The projection exposure system can also be a DUV lithography system. "DUV" stands for "Deep Ultraviolet" and refers to a wavelength of the working light between 30 nm and 250 nm.

[0057] The term "one" here is not necessarily to be understood as restricting the number to exactly one element. Rather, it can also refer to multiple elements, such as two, three, or more. Similarly, every other counter used here should not be interpreted as restricting the number to the specified number of elements. Instead, numerical deviations, both higher and lower, are possible unless otherwise stated.

[0058] The embodiments and features described for the proposed optical system apply accordingly to the proposed projection optics and the proposed projection exposure system, and vice versa.

[0059] Other possible implementations of the invention also include combinations not explicitly mentioned above or below regarding the execution. Carl Zeiss SMT GmbH

[0060] Eleven examples of described features and embodiments are presented. In doing so, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0061] Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the exemplary embodiments of the invention described below. The invention will be explained in more detail below with reference to preferred embodiments and the accompanying figures.

[0062] Fig. 1 shows a schematic meridional section of a projection exposure system for EUV projection lithography!

[0063] Fig. 2 shows a schematic view of an embodiment of a projection optic for the projection exposure system according to Fig. 1;

[0064] Fig. 3 shows a schematic sectional view of an embodiment of an optical system for the projection exposure system according to Fig. 1;

[0065] Fig. 4 shows another schematic sectional view of the optical system according to Fig. 3;

[0066] Fig. 5 shows a schematic view of another embodiment of an optical system for the projection exposure system according to Fig. 1.

[0067] Fig. 6 shows another schematic view of the optical system according to Fig. 5; and

[0068] Fig. 7 shows a schematic sectional view of the optical system according to Fig.

[0069] 5. Carl Zeiss SMT GmbH

[0070] 12

[0071] In the figures, identical or functionally equivalent elements have been labelled with the same reference symbols, unless otherwise indicated. Furthermore, it should be noted that the representations in the figures are not necessarily to scale.

[0072] Fig. 1 shows an embodiment of a projection exposure system 1 (lithography system), in particular an EUV lithography system. One embodiment of the illumination system 2 of the projection exposure system 1 has, in addition to a light or radiation source 3, an illumination optic 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 separate module from the rest of the illumination system 2. In this case, the illumination system 2 does not include the light source 3.

[0073] A reticule 7 arranged in the object field 5 is exposed. The reticule 7 is held by a reticule holder 8. The reticule holder 8 can be moved, particularly in a scanning direction, via a reticule displacement drive 9.

[0074] Figure 1 illustrates a Cartesian coordinate system with an x-direction x, a y-direction y, and a z-direction z. The x-direction x extends perpendicularly into the plane of the drawing. The y-direction y is horizontal, and the z-direction z is vertical. In Figure 1, the scan direction runs along the y-direction y. The z-direction z is perpendicular to the object plane 6.

[0075] The projection exposure system 1 comprises a projection optic 10. The projection optic 10 serves to image the object field 5 onto an image field 11 in an image plane 12. The image plane 12 runs parallel to the object plane 6. Alterna- Carl Zeiss SMT GmbH

[0076] 13. In this context, an angle other than 0° between the object plane 6 and the image plane 12 is also possible.

[0077] A structure on the reticulum 7 is imaged onto a photosensitive layer of a wafer 13 located in the image plane 12 within the image field 11. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be moved, particularly along the y-direction y, via a wafer transfer drive 15. The movement of the reticulum 7 via the reticulum transfer drive 9 and of the wafer 13 via the wafer transfer drive 15 can be synchronized.

[0078] Light source 3 is an EUV radiation source. Light source 3 emits, in particular, EUV radiation 16, which is also referred to below as useful radiation, illumination radiation, or illumination light. The useful radiation 16 has a wavelength in the range between 5 nm and 30 nm. Light source 3 can be a plasma source, for example, an LPP source (Laser Produced Plasma, plasma generated using a laser) or a DPP source (Gas Discharged Produced Plasma, plasma generated by gas discharge). It can also be a synchrotron-based radiation source. Light source 3 can be a free-electron laser (FEL).

[0079] The illumination radiation 16 emanating from the light source 3 is focused by a collector 17. The collector 17 can be a collector with one or more ellipsoidal and / or hyperboloid reflective surfaces. The at least one reflective surface of the collector 17 can be illuminated by the illumination radiation 16 at grazing incidence (Gl), i.e., with angles of incidence greater than 45°, or at normal incidence (NI), i.e., with angles of incidence less than 45°. Carl Zeiss SMT GmbH

[0080] 14. The collector 17 can be structured and / or coated on the one hand to optimize its reflectivity for the useful radiation and on the other hand to suppress stray light.

[0081] After the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 can represent a separation between a radiation source module, comprising the light source 3 and the collector 17, and the illumination optics 4.

[0082] The illumination optics 4 comprise a deflecting mirror 19 and, downstream in the beam path, a first faceted mirror 20. The deflecting mirror 19 can be a planar deflecting mirror or, alternatively, a mirror with an effect that influences the beam shape beyond the mere deflection effect. Alternatively or additionally, the deflecting mirror 19 can be designed as a spectral filter that separates a useful wavelength of the illumination radiation 16 from stray light of a different wavelength. If the first faceted mirror 20 is arranged in a plane of the illumination optics 4 that is optically conjugate to the object plane 6 as the field plane, it is also referred to as a field faceted mirror. The first faceted mirror 20 comprises a plurality of individual first facets 21, which can also be referred to as field facets. Only a few of these first facets 21 are shown in Fig. 1 as examples.

[0083] The first facets 21 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or semicircular border contour. The first facets 21 can be designed as planar facets or alternatively as convexly or concavely curved facets.

[0084] As is known, for example, from DE 10 2008 009 600 Al, the first facets 21 themselves can each also consist of a large number of individual mirrors, in particular Carl Zeiss SMT GmbH

[0085] 15, in particular, a multitude of micromirrors. The first faceted mirror 20 can in particular be designed as a microelectromechanical system (MEMS system). For details, reference is made to DE 10 2008 009 600 A1.

[0086] Between the collector 17 and the deflecting mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction y.

[0087] In the beam path of the illumination optics 4, a second faceted mirror 22 is arranged downstream of the first faceted mirror 20. If the second faceted mirror 22 is arranged in a pupil plane of the illumination optics 4, it is also referred to as a pupil faceted mirror. The second faceted mirror 22 can also be arranged at a distance from a pupil plane of the illumination optics 4. In this case, the combination of the first faceted mirror 20 and the second faceted mirror 22 is also referred to as a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1, EP 1 614 008 B1, and US 6,573,978.

[0088] 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 referred to as pupil facets.

[0089] The second facets 23 can also be macroscopic facets, which may, for example, have round, rectangular, or hexagonal edges, or alternatively, facets composed of micromirrors. Reference is also made to DE 10 2008 009 600 Al in this regard.

[0090] The second facets 23 can have flat or, alternatively, convex or concave curved reflective surfaces. Carl Zeiss SMT GmbH

[0091] 16

[0092] The illumination optics 4 thus form a double-faceted system. This basic principle is also known as a honeycomb condenser (EnglJ Fly's Eye Integrator).

[0093] It can be advantageous not to arrange the second faceted mirror 22 exactly in a plane that is optically conjugate to a pupil plane of the projection optics 10. In particular, the second faceted mirror 22 can be arranged tilted relative to a pupil plane of the projection optics 10, as described, for example, in DE 10 2017 220 586 A1.

[0094] With the aid of the second faceted mirror 22, the individual first facets 21 are imaged into the object field 5. The second faceted mirror 22 is the last beam-shaping, or indeed the last, mirror for the illumination radiation 16 in the beam path before the object field 5.

[0095] In another embodiment of the illumination optics 4, not shown, a transmission optic can be arranged in the beam path between the second facet mirror 22 and the object field 5, which contributes in particular to imaging the first facets 21 into the object field 5. The transmission optic can have exactly one mirror, or alternatively two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics 4. The transmission optic can in particular comprise one or two mirrors for normal incidence (Ni mirrors, normal incidence mirrors) and / or one or two mirrors for grazing incidence (GF mirrors, grazing incidence mirrors).

[0096] In the embodiment shown in Fig. 1, the illumination optics 4 has exactly three mirrors after the collector 17: the deflecting mirror 19, the first faceted mirror 20, and the second faceted mirror 22. Carl Zeiss SMT GmbH

[0097] 17

[0098] In a further embodiment of the lighting optics 4, the deflecting mirror 19 can also be omitted, so that the lighting optics 4 after the collector 17 can then have exactly two mirrors, namely the first faceted mirror 20 and the second faceted mirror 22.

[0099] The mapping of the first facets 21 by means of the second facets 23 or with the second facets 23 and a transmission optic into the object plane 6 is regularly only an approximate mapping.

[0100] The projection optics 10 comprise a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

[0101] In the example shown in Fig. 1, the projection optics 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or any other number of mirrors Mi are also possible. The projection optics 10 is a double-obscured optic. The penultimate mirror M5 and the last mirror M6 each have an aperture for the illumination radiation 16. The projection optics 10 has an image-side numerical aperture greater than 0.5, and which can also be greater than 0.6, for example, 0.7 or 0.75.

[0102] The reflective surfaces of the mirrors Mi can be designed as freeform surfaces without an axis of rotational symmetry. Alternatively, the reflective surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflective surface shape. The mirrors Mi, like the mirrors of the illumination optics 4, can have highly reflective coatings for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon. Carl Zeiss SMT GmbH

[0103] 18

[0104] The projection optics 10 has a large object-image offset in the y-direction y between a y-coordinate of a center of the object field 5 and a y-coordinate of the center of the image field 11. This object-image offset in the y-direction y can be approximately as large as a z-distance between the object plane 6 and the image plane 12.

[0105] The projection optics 10 can be anamorphic. In particular, they have different image scales βx, βy in the x and y directions. The two image scales βx, βy of the projection optics 10 are preferably (βx, βy) = (+ / - 0.25, + / - 0.125). A positive image scale β indicates a projection without image inversion. A negative sign for the image scale β indicates a projection with image inversion.

[0106] The projection optics 10 thus lead to a reduction in the x-direction x, that is, in the direction perpendicular to the scan direction, in a ratio of 4'1.

[0107] The projection optics 10 lead to a reduction of 8H in the y-direction y, that is, in the scan direction.

[0108] Other magnification ratios are also possible. Magnification ratios with the same sign and absolute value in the x and y directions (x, y), for example with absolute values ​​of 0.125 or 0.25, are also possible.

[0109] The number of intermediate image planes in the x and y directions x, y in the beam path between the object field 5 and the image field 11 can be the same or, depending on the design of the projection optics 10, different. Examples of projection optics with different numbers of such intermediate images in the x and y directions x, y are known from US Patent 2018 / 0074303 A. Carl Zeiss SMT GmbH

[0110] 19 Each of the second facets 23 is assigned to exactly one of the first facets 21 to form an illumination channel for illuminating the object field 5. This can result, in particular, in illumination according to Köhler's principle. The far field is divided into a multitude of object fields 5 with the help of the first facets 21. The first facets 21 generate a plurality of images of the intermediate focus on the second facets 23 assigned to each of them.

[0111] The first facets 21 are each superimposed on a corresponding second facet 23 to illuminate the object field 5 on the reticle 7. The illumination of the object field 5 is particularly homogeneous. It preferably exhibits a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

[0112] The illumination of the entrance pupil of the projection optics 10 can be geometrically defined by the arrangement of the second facets 23. By selecting the illumination channels, in particular the subset of the second facets 23 that carry light, the intensity distribution in the entrance pupil of the projection optics 10 can be adjusted. This intensity distribution is also referred to as the illumination setting or illumination pupil filling.

[0113] Another preferred pupil uniformity in the area of ​​defined illuminated sections of an illumination pupil of the illumination optics 4 can be achieved by a redistribution of the illumination channels.

[0114] Further aspects and details of the illumination of the object field 5, and in particular the entrance pupil of the projection optics 10, are described below. Carl Zeiss SMT GmbH

[0115] 20

[0116] The projection optics 10 can, in particular, have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

[0117] The entrance pupil of the projection optics 10 cannot always be illuminated exactly by the second faceted mirror 22. When the projection optics 10 image the center of the second faceted mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, a surface can be found where the pairwise determined separation of the aperture rays is minimized. This surface represents the entrance pupil or a surface conjugate to it in real space. In particular, this surface exhibits a finite curvature.

[0118] The projection optics 10 may have different entrance pupil positions for the tangential and sagittal beam paths. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second faceted mirror 22 and the reticle 7. This optical element can accommodate the different positions of the tangential and sagittal entrance pupils.

[0119] In the arrangement of the components of the illumination optics 4 shown in Fig. 1, the second faceted mirror 22 is arranged in a plane conjugate to the entrance pupil of the projection optics 10. The first faceted mirror 20 is arranged tilted relative to the object plane 6. The first faceted mirror 20 is arranged tilted relative to an arrangement plane defined by the deflecting mirror 19. The first faceted mirror 20 is arranged tilted relative to an arrangement plane defined by the second faceted mirror 22.

[0120] Fig. 2 shows a schematic view of an embodiment of a projection optic 10 as previously described. In Fig. 2, only the mirror Ml is shown. As Carl Zeiss SMT GmbH

[0121] As mentioned in section 21 above, the projection optics 10 can have any number of mirrors M1 to M6. However, only mirror M1 will be discussed below. All subsequent statements concerning mirror M1 are also applicable to mirrors M2 to M6.

[0122] In addition to the mirror Ml, the projection optics 10 has a heating head 24. The heating head 24 can also be referred to as a mirror preheater. Each mirror Ml to M6 can be assigned one such heating head 24. It is also possible for each mirror Ml to M6, or for some of the mirrors Ml to M6, to be assigned several such heating heads 24.

[0123] The heating head 24 is used to bring the mirror Ml up to operating temperature more quickly, which serves to reduce the time until the waver 13 is exposed and thus increase the productivity of the projection exposure system 1. The mirror Ml has an optically effective area 25 into which heat Q is introduced by means of radiation 26, in particular infrared radiation, generated by the heating head 24.

[0124] Fig. 3 shows a schematic sectional view of an embodiment of an optical system 100'. Fig. 4 shows another schematic sectional view of the optical system 100'. Reference is made hereafter to Figs. 3 and 4 simultaneously.

[0125] The optical system 100' can be part of the previously mentioned heating head 24. However, the optical system 100' can also be part of the projection optics 10. An optical axis 102 is assigned to the optical system 100'. The optical system 100' can have several optical axes 102, which can be arranged, for example, parallel to each other and at a distance from each other. The radiation 26 travels along the optical axis 102 through the optical system 100'. Carl Zeiss SMT GmbH

[0126] 22

[0127] The optical system 100' comprises several optical elements 104, 106, 108. The number of optical elements 104, 106, 108 is arbitrary. The optical elements 104, 106, 108 are lenses. In particular, a first optical element 104, a second optical element 106, and a third optical element 108 are provided. The first optical element 104 has a light-intake surface 110 and a light-exit surface 112. Accordingly, the second optical element 106 also has a light-intake surface 114 and a light-exit surface 116. The third optical element 108 also has a light-intake surface 118 and a light-exit surface 120.

[0128] The optical elements 104, 106, 108 and the optical axis 102 form a beam path 122, which the radiation 26 follows through the optical system 100'. Fig. 3 shows the optical system 100' in an ideal state, in which the radiation 26 falls onto the optically effective surface 25 of the mirror M1 at a point of incidence 124. A "point of incidence" is not, in particular, a point in the geometric sense, but rather a region of the optically effective surface 25 onto which the radiation 26 falls.

[0129] Fig. 4 shows the optical system 100' after a certain operating period. The optical elements 104, 106, 108 are mounted in sockets (not shown). The optical elements 104, 106, 108 are made of a different material than their sockets. In particular, the sockets are made of a material with a higher coefficient of thermal expansion than the material from which the optical elements 104, 106, 108 are made. This results in the optical elements 104, 106, 108, or at least some of them, moving undefinedly within their sockets, as indicated in Fig. 4 by arrows 126, 128. Carl Zeiss SMT GmbH

[0130] 23

[0131] This undefined movement of the optical elements 104, 106, 108 causes the radiation 26 to no longer fall on the optically effective surface 25 of the mirror Ml at a desired location, but rather to strike the optically effective surface 25 with a certain offset or displacement 130. This is known as a misalignment error. As a result, the optically effective surface 25 can no longer be heated in the desired manner. In particular, this causes the misalignment point 124 to shift by the displacement 130 on the optically effective surface 5.

[0132] Fig. 5 shows a schematic view of another embodiment of an optical system 100. Fig. 6 shows another schematic view of the optical system 100. Reference is made hereafter to Figs. 5 and 6 simultaneously.

[0133] Optical system 100 is essentially identical in design to optical system 100'. Therefore, only the differences between the two embodiments of optical system 100 and 100' will be discussed below. Figures 5 and 6 show only the first optical element 104. However, all subsequent descriptions concerning the first optical element 104 are applicable to optical elements 106 and 108. The first optical element 104 will be referred to simply as optical element 104 below.

[0134] The optical element 104 is associated with a mount 132, as previously mentioned, which supports the optical element 104. The mount 132 can have any desired geometry. In Figures 5 and 6, the mount 132 is shown in a highly schematic way as a ring-shaped component. The mount 132 has a central receiving opening 134 in which the optical element 104 is received. The optical axis 102, and thus also the beam path 122 (not shown), passes through the receiving opening 134. A gap 136 can be provided between the mount 132 and the optical element 104. Carl Zeiss SMT GmbH

[0135] 24

[0136] To prevent a misplacement error as previously mentioned, the optical system 100 has a displacement device 138. The displacement device 138 comprises a spring element 140 arranged in the receiving opening 134. The spring element 140 is preferably a compression spring, in particular a leaf spring. However, the spring element 140 can be any other compression spring. The spring element 140 is pre-tensioned and exerts a compressive force F on the optical element 104.

[0137] In addition to the spring element 140, the displacement device 138 has at least one mounting section 142, 144 attached to the socket 132. Particularly preferably, exactly two mounting sections 142, 144 are provided, especially a first mounting section 142 and a second mounting section 144. However, exactly one mounting section 142, 144 is also possible. The spring element 140 is arranged between the first mounting section 142 and the second mounting section 144. The first mounting section 142, the second mounting section 144, and the spring element 140 are arranged evenly distributed around the optical axis 102 of the optical system 100. In particular, the first mounting section 142, the second mounting section 144, and the spring element 140 are arranged offset from each other by 120° around the optical axis 102.

[0138] The first assembly section 142 has a curved, in particular arc-shaped, first contact surface 146. Accordingly, the second assembly section 144 has a curved, in particular arc-shaped, second contact surface 148. The optical element 104 rests with an outer surface 150 against the contact surfaces 146, 148 and against the spring element 140.

[0139] The plant sections 142 and 144 are formed in one piece, specifically in one piece of material, with the socket 132. "One piece" or "single-part" means provided- Carl Zeiss SMT GmbH

[0140] 25. It is understood that the plant sections 142, 144 and the socket 132 form a single component and are not composed of different sub-components. "Made of material" in this context means, in particular, that the socket 132 and the plant sections 142, 144 are manufactured entirely from the same material. For example, the socket 132 is made of a steel alloy, in particular a stainless steel alloy.

[0141] The spring element 140 is arranged between the optical element 104 and the socket 132. In particular, the spring element 140 is received in the receiving opening 134 and rests against it.

[0142] The optical element 104 is made of a material with a first coefficient of thermal expansion. The housing 132 is made of a material with a second coefficient of thermal expansion. The second coefficient of thermal expansion is greater than the first. This results in the housing 132 expanding more than the optical element 104 when heat Q is introduced into the optical system 100, as greatly exaggerated in Fig. 6. The heat Q can be introduced by radiation 26.

[0143] As the housing 132 expands, the receiving opening 134 enlarges. The optical element 104 rests with its outer surface 150 further against the contact surfaces 146, 148 of the mounting sections 142, 144. The spring element 140 is pre-tensioned such that it constantly presses the optical element 104 against the contact surfaces 146, 148 with the compressive force F, so that the optical element 104 follows the contact surfaces 146, 148 during the thermal expansion of the housing 132.

[0144] The spring element 140 displaces the optical element 104 in the mount 132, in particular in the receiving opening 134, linearly along exactly one Carl Zeiss SMT GmbH

[0145] 26

[0146] Spatial direction 152. The spatial direction 152 can be oriented perpendicular to the optical axis 102. The spatial direction 152 can be oriented along the z-direction z or opposite to it. However, the spatial direction 152 can also be oriented along the x-direction x, opposite to the x-direction x, or obliquely to the z-direction z and / or the x-direction x. The spatial direction 152 is, however, oriented perpendicular to the optical axis 102.

[0147] Fig. 7 shows a schematic sectional view of the optical system 100. In this case, each optical element 104, 106, 108 is assigned a socket 132 with its own displacement device 138, as mentioned previously. However, it is not absolutely necessary that each optical element 104, 106, 108 has such a displacement device 138 assigned to it.

[0148] Each of the displacement devices 138 is assigned its own spatial direction 152, 154, 156. The spatial directions 152, 154, 156 can be oriented at least partially in the same or opposite directions. Furthermore, the spatial directions 152, 154, 156 can also be oriented obliquely to each other. However, the spatial directions 152, 154, 156 are oriented in such a way that the placement point 124 of the radiation 26 does not change in the event of a heat-induced deformation of the mounts 132 of the optical elements 104, 106, 108. That is, an offset 130 as mentioned above, and thus a placement error, is prevented.

[0149] Although the present invention has been described using exemplary embodiments, it can be modified in many ways. Carl Zeiss SMT GmbH

[0150] 27

[0151] REFERENCE MARK LIST

[0152] 1 Projection exposure system

[0153] 2 lighting systems

[0154] 3 light source

[0155] 4 Lighting optics

[0156] 5 object field

[0157] 6 Object level

[0158] 7 reticles

[0159] 8 label holders

[0160] 9 Reticle displacement drive

[0161] 10 Projection optics

[0162] 11 Image field

[0163] 12 Image plane

[0164] 13 wafers

[0165] 14 wafer holders

[0166] 15 wafer transfer drive

[0167] 16 Lighting radiation

[0168] 17 Collector

[0169] 18 Intermediate focus plane

[0170] 19 deflecting mirrors

[0171] 20 first faceted mirror

[0172] 21 first facet

[0173] 22 second faceted mirrors

[0174] 23 second facet

[0175] 24 heating head

[0176] 25 optically effective areas

[0177] 26 Radiation

[0178] 100 optical system

[0179] 100' optical system Carl Zeiss SMT GmbH

[0180] 28

[0181] 102 optical axis

[0182] 104 optical element

[0183] 106 optical element

[0184] 108 optical element

[0185] 110 light entry area

[0186] 112 Light emission area

[0187] 114 Light entry area

[0188] 116 Light emission area

[0189] 118 Light entry area

[0190] 120 light emission area

[0191] 122 Beam path

[0192] 124 storage point

[0193] 126 Arrow

[0194] 128 Arrow

[0195] 130 offset

[0196] 132 version

[0197] 134 Recording through chb r uch

[0198] 136 gap

[0199] 138 Relocation device

[0200] 140 spring element

[0201] 142 Plant section

[0202] 144 Plant section

[0203] 146 m² of plant area

[0204] 148 site area

[0205] 150 outdoor area

[0206] 152 Spatial direction

[0207] 154 Spatial direction

[0208] 156 Spatial direction

[0209] F Pressure force Carl Zeiss SMT GmbH

[0210] ml mirror

[0211] M2 mirrors

[0212] M3 mirror

[0213] M4 mirrors M5 mirrors

[0214] M6 mirrors

[0215] Q heat x x-direction yy direction z z-direction

Claims

Carl Zeiss SMT GmbH 30 PATENT CLAIMS 1. Optical system (100) for a projection exposure system (1), comprising an optical element (104, 106, 108) and a mount (132) supporting the optical element (104, 106, 108), wherein the mount (132) has a displacement device (138) configured to displace the optical element (104, 106, 108) linearly along exactly one spatial direction (152, 154, 156) in the event of a heat-induced deformation of the mount (132), and wherein the displacement device (138) comprises at least one section (142, 144) attached to the mount (132) against which the optical element (104, 106, 108) rests, and a spring element (140) which holds the optical element (104, 106, 108) during the The shape of the socket (132) is shifted along the spatial direction (152, 154, 156) due to heat-induced deformation.

2. Optical system according to claim 1, wherein the displacement device (138) has a first installation section (142) and a second installation section (144), and wherein the spring element (140) is arranged between the first installation section (142) and the second installation section (144).

3. Optical system according to claim 2, wherein the first assembly section (142), the second assembly section (144) and the spring element (140) are arranged uniformly distributed around an optical axis (102) of the optical system (100), and wherein the first assembly section, the second assembly section and the spring element (140) are in particular arranged offset from each other by 120°.

4. Optical system according to claim 2 or 3, wherein the first system section (142) and the second system section (144) each have a curved contact surface (146, 148) against which the optical element (104, 106, 108) rests. Carl Zeiss SMT GmbH 31 5. Optical system according to one of claims 1 - 4, wherein the spring element (140) is arranged between the socket (132) and the optical element (104, 106, 108).

6. Optical system according to one of claims 1 - 5, wherein the spring element (140) is a leaf spring.

7. Optical system according to one of claims 1 - 6, wherein the optical element (104, 106, 108) is a lens.

8. Optical system according to one of claims 1 - 7, wherein the socket (312) has a receiving opening (134) in which the optical element (104, 106, 108) is received, so that a beam path (122) of the optical system (100) passes through the socket (132).

9. Optical system according to one of claims 1 - 8, comprising several optical elements (104, 106, 108), wherein each optical element (104, 106, 108) is associated with a socket (132) with a displacement device (138).

10. Optical system according to claim 9, wherein each displacement device (138) is assigned a spatial direction (152, 154, 156), and wherein the spatial directions (152, 154, 156) are different from each other.

11. Optical system according to claim 10, wherein the spatial directions (152, 154, 156) are oriented such that a storage point (124) of the optical system (100) is unaffected by a heat-induced change in shape of the mounts (132). Carl Zeiss SMT GmbH 32 12. Optical system according to one of claims 1 - 11, wherein the optical element (104, 106, 108) is made of a material with a first coefficient of thermal expansion, wherein the mount (132) is made of a material with a second coefficient of thermal expansion, and wherein the second coefficient of thermal expansion is greater than the first coefficient of thermal expansion.

13. Projection optics (10) for a projection exposure system (1) with a mirror (M1, M2, M3, M4, M5, M6) and an optical system (100) according to one of claims 1 - 12, wherein the optical system (100) is configured to supply heat (Q) to the mirror (M1, M2, M3, M4, M5, M6) by means of radiation (26), in particular infrared radiation.

14. Projection exposure system (1) with an optical system (100) according to one of claims 1 - 12 and / or a projection optic (10) according to claim

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