Imaging EUV optical unit for imaging the object field into the image field.

Abstract

We provide an imaging EUV optical unit for imaging an object field into an image field. [Solution] The imaging EUV optical unit (10) plays the role of imaging the object field (5) into the image field (11). The imaging optical unit (10) has a plurality of mirrors (M1-M6) for guiding the EUV imaging light (16) along the imaging beam path. The plurality of mirrors include at least two NI mirrors (M1, M2, M5, M6) and at least one GI mirror (M3, M4). The last two mirrors (M5, M6) in the imaging beam path are designed as NI mirrors and do not have apertures for the passage of imaging light. The reflective surface of the third to last mirror (M4) in the imaging beam path faces the last mirror (M6) in the imaging beam path. This results in an imaging EUV optical unit with improved usability for EUV projection exposure apparatus.

Description

[Technical Field]

[0001] This patent application claims priority to German patent application DE102023203224.4, the contents of which are incorporated herein by reference.

[0002] The present invention relates to an imaging EUV optical unit for imaging an object field into an image field. Furthermore, the present invention relates to an optical system having such an imaging optical unit, a projection exposure apparatus having such an optical system, a method for manufacturing micro or nanostructure components using such a projection exposure apparatus, and micro or nanostructure components manufactured by the method. [Background technology]

[0003] The type of projection optical unit mentioned at the beginning is, WO2018 / 010960A1, DE102015209827A1, DE102012212753A1, U.S. Patent Application Publication No. 2010 / 0149509, It is known from U.S. Patent No. 4,964,706, DE102008033341A1, and DE102011076752A1. [Overview of the project]

[0004] The object of the present invention is to develop the imaging EUV optical unit of the type described at the beginning so that its usability in an EUV projection exposure apparatus is improved.

[0005] According to the present invention, this objective is achieved by an imaging EUV optical unit having the features specified in claim 1.

[0006] According to the present invention, it has been recognized that the optical design of an imaging EUV optical unit having a reflective surface where the third-to-last mirror in the imaging beam path faces the last mirror leads to the possibility of guiding the imaging beam path around the last mirror in the imaging beam path, while ensuring a compact structure for the imaging EUV optical unit. This is particularly advantageous because the last mirror that determines the image-side numerical aperture of the imaging EUV optical unit typically has a large embodiment, and guiding the imaging beam path around this mirror saves installation space.

[0007] The reflective surface of the third-to-last mirror faces the last mirror in the imaging beam path if it is possible to draw a direct line of sight, unobstructed by the body of the third-to-last mirror, from at least one point on the reflective surface of the third-to-last mirror, in particular from all points on the reflective surface of the third-to-last mirror used to reflect EUV imaging light, to the last mirror. This line of sight does not need to extend directly to a point on the reflective surface of the last mirror, but can also extend to the body of the last mirror in the imaging beam path.

[0008] The imaging EUV optical unit may have an image-side numerical aperture of less than 0.5, particularly less than 0.4. The image-side numerical aperture may be greater than 0.25 and greater than 0.3.

[0009] The mean wavefront aberration RMS may be less than 200 mλ (λ: wavelength of the light used), less than 100 mλ, or less than 50 mλ. This wavefront aberration RMS is typically greater than 5 mλ.

[0010] The object field of the imaging EUV optical unit may be located on the object plane. The image field of the imaging EUV optical unit may be located on the image plane. The object plane may extend parallel to the image plane. The object plane may extend at an angle other than 0° with respect to the image plane.

[0011] Each GI mirror can be directly continuous within the imaging beam path. Each GI mirror can amplify its own deflection effect on EUV imaging light.

[0012] Alternatively, at least one NI mirror may be present between the two GI mirrors.

[0013] The imaging EUV optical unit according to claim 2, having an object-image offset smaller than the distance between the object field and the image field, can be designed to be small and is advantageous.

[0014] The object-image offset may be less than 75% of the distance between the object field and the image field, may be less than 50%, may be less than 40%, may be less than 30%, may be less than 25%, may be less than 20%, and may also be on the order of 10%.

[0015] The distance ratio according to claim 3 enables a small embodiment of the GI mirror arranged in the vicinity of the intermediate image. This GI mirror, which is at most in the vicinity of one-tenth of the field distance with respect to the intermediate image, can be the third mirror from the end of the imaging EUV optical unit. This distance ratio may be applied to all GI mirrors of the imaging EUV optical unit.

[0016] The distance of at least one GI mirror from the intermediate image along the imaging beam path may be less than 8% of the distance between the object field and the image field, may be less than 6%, may be less than 5%, may be less than 4%, may be less than 3%, may be less than 2%, or may be on the order of 1%.

[0017] The imaging EUV optical unit may be embodied as a choristikonal-type optical unit having different numbers of intermediate images on two imaging optical surfaces. The difference in the number of intermediate images on the two imaging optical surfaces may be exactly 1, but may also be larger than that, for example, 2, or even larger than that. For the choristikonal-type optical unit, reference is made to U.S. Patent No. 10,656,400.

[0018] At least one intermediate image may be a real intermediate image or a virtual intermediate image. The imaging EUV optical unit may have multiple real intermediate images and / or virtual intermediate images.

[0019] The imaging EUV optical unit can have exactly one intermediate image.

[0020] The addition of the deflection angle according to claim 4 proved to be a particularly suitable design modification in situations where the reflective surface of the third-to-last mirror is oriented to face the last mirror.

[0021] The number of mirrors according to claims 5 and 6 proved to be particularly preferable. The imaging EUV optical unit may have exactly four NI mirrors.

[0022] The distance of the intermediate image from the last mirror according to claim 7 allows for compact guidance of the imaging beam path that has passed through the last mirror. The spatial distance between the intermediate image and the last mirror may be less than 50%, less than 40%, less than 30%, less than 25%, less than 20%, less than 15%, or on the order of 10% of the maximum spread of the last mirror in the meridional plane.

[0023] In the embodiment according to claim 8, the imaging EUV optical unit does not have an intermediate image perpendicular to the meridional plane. Therefore, there is a choristikonal type of imaging in the sense of U.S. Patent No. 10,656,400. There is image inversion on the sagittal plane perpendicular to the meridional plane.

[0024] For a given EUV light source power, the total EUV transmittance according to claim 9 enables increased EUV throughput to the image field, and therefore improved exposure power. Alternatively, a reduced power supply can be used for a given required exposure power to the image field.

[0025] The total transmittance of the imaging EUV optical unit may be greater than 11%, greater than 12%, greater than 13%, greater than 14%, and greater than 15%. Due to the number of mirrors and the individual EUV transmittance of the mirrors guiding the imaging light, which is usually 80% or less, the total transmittance is usually less than 20%.

[0026] The image field according to claim 10 enables high imaging throughput. On the image plane, the image field can have a maximum extent greater than 30 mm, greater than 35 mm, greater than 40 mm, greater than 45 mm, and may be greater than 50 mm. The maximum extent can also be on the order of 52 m.

[0027] The advantages of the optical system according to claim 11, the projection exposure apparatus according to claim 12, the manufacturing method according to claim 13, and the microstructure or nanostructure component according to claim 14 correspond to the advantages already described above with respect to the projection optical unit according to the present invention.

[0028] The EUV light source of the projection exposure apparatus may be designed to produce usable wavelengths of 13.5 nm or less, less than 13.5 nm, less than 10 nm, less than 8 nm, less than 7 nm, for example, 6.7 nm or 6.9 nm. Usable wavelengths of less than 6.7 nm, especially on the order of 6 nm, are also possible.

[0029] In more detail, this projection lithography apparatus can be used to manufacture semiconductor components, such as memory chips.

[0030] Below, at least one exemplary embodiment of the present invention will be described with reference to the drawings. [Brief explanation of the drawing]

[0031] [Figure 1] This diagram schematically shows a meridian cross-section of a projection exposure apparatus for EUV projection lithography. [Figure 2]Figure 1 shows an embodiment of the imaging optical unit used as a projection lens in the projection exposure apparatus, with meridian cross-sections illustrating the imaging beam paths of the principal rays, upper coma rays, and lower coma rays of three selected field of view points. [Figure 3] Figure 1 shows an embodiment of the imaging optical unit used as a projection lens in the projection exposure apparatus, with meridian cross-sections illustrating the imaging beam paths of the principal rays, upper coma rays, and lower coma rays of three selected field of view points. [Figure 4] Figure 1 shows an embodiment of the imaging optical unit used as a projection lens in the projection exposure apparatus, with meridian cross-sections illustrating the imaging beam paths of the principal rays, upper coma rays, and lower coma rays of three selected field of view points. [Figure 5] Figure 1 shows an embodiment of the imaging optical unit used as a projection lens in the projection exposure apparatus, with meridian cross-sections illustrating the imaging beam paths of the principal rays, upper coma rays, and lower coma rays of three selected field of view points. [Figure 6] This is a diagram of the imaging optical unit according to Figure 5, as viewed from viewing direction VI in Figure 5. [Figure 7] Figure 1 shows an embodiment of the imaging optical unit used as a projection lens in the projection exposure apparatus, with meridian cross-sections illustrating the imaging beam paths of the principal rays, upper coma rays, and lower coma rays of three selected field of view points. [Figure 8] Figure 1 shows an embodiment of the imaging optical unit used as a projection lens in the projection exposure apparatus, with meridian cross-sections illustrating the imaging beam paths of the principal rays, upper coma rays, and lower coma rays of three selected field of view points. [Figure 9] Figure 1 shows a further embodiment of the imaging optical unit used as a projection lens in the projection exposure apparatus, again in a meridian cross-section, which precisely depicts the imaging beam path of individual selected rays at a single field of view. [Modes for carrying out the invention]

[0032] In the following description, the basic components of the microlithograph projection exposure apparatus 1 are first explained as an example with reference to Figure 1. The description of the basic structure of the projection exposure apparatus 1 and its components should not be interpreted as restrictive.

[0033] One embodiment of the illumination system 2 of the projection exposure apparatus 1 includes, in addition to a light source or radiation source 3, an illumination optical unit 4 for illuminating the object field 5 within the object surface 6. In an alternative embodiment, the light source 3 may be provided as a module separate from the rest of the illumination system. In that case, the illumination system does not include the light source 3.

[0034] A reticle 7 positioned in the object field 5 is exposed. The reticle 7 is held by a reticle holder 8. The reticle holder 8 is displaceable, particularly in the scanning direction, by a reticle displacement drive mechanism 9.

[0035] For explanatory purposes, the Cartesian xyz coordinate system is shown in Figure 1. The x-direction extends perpendicular to the plane of the drawing and toward the back of the drawing. The y-direction extends horizontally, and the z-direction extends vertically. In Figure 1, the scanning direction extends in the y-direction. The z-direction extends perpendicular to the object plane 6.

[0036] The projection exposure apparatus 1 includes a projection optical unit or an imaging optical unit 10. The projection optical unit 10 plays the role of imaging the object field 5 onto the image field 11 of the image plane 12. The image plane 12 extends parallel to the object field 6. Alternatively, an angle other than 0° between the object field 6 and the image plane 12 is also possible.

[0037] The structure on the reticle 7 is imaged onto the photosensitive layer of the wafer 13, which is positioned in the image field 11 region of the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 is displaceable, particularly in the y-direction, by a wafer displacement drive mechanism 15. Firstly, the displacement of the reticle 7 by the reticle displacement drive mechanism 9 and secondly, the displacement of the wafer 13 by the wafer displacement drive mechanism 15 can be performed in synchronization with each other.

[0038] Radiation source 3 is an EUV radiation source. Radiation source 3 emits EUV radiation 16 in particular, which will be referred to below as the radiation used or illumination radiation. Specifically, the radiation used has a wavelength in the range of 5 nm to 30 nm. Radiation source 3 may be a plasma source, such as an LPP (laser-generated plasma) source or a GDPP (gas discharge-generated plasma) source. It may also be a synchrotron-based radiation source. Radiation source 3 may be a free electron laser (FEL).

[0039] Illumination radiation 16 emitted from radiation source 3 is focused by a focuser 17. The focuser 17 may have one or more ellipsoidal and / or hyperbolic reflective surfaces. Illumination radiation 16 can be incident on at least one reflective surface of the focuser 17 by grazing incidence (GI), i.e., at an incidence angle greater than 45°, or by normal incidence (NI), i.e., at an incidence angle less than 45°. The focuser 17 may be structured and / or coated to optimize its reflectivity to the radiation used, on the one hand, and to suppress stray light, on the other hand.

[0040] The illumination radiation 16 propagates downstream of the concentrator 17, through the intermediate focal point of the intermediate focal plane 18. The intermediate focal plane 18 can correspond to the boundary between the radiation source module, which includes the radiation source 3 and the concentrator 17, and the illumination optical unit 4.

[0041] The illumination optical unit 4 includes a first facet mirror 19. When the first facet mirror 19 is positioned on a surface of the illumination optical unit 4 that is optically conjugate to the object surface 6, this facet mirror is also called a field-of-view facet mirror. The first facet mirror 19 comprises a number of individual first facets 20, which are hereinafter also referred to as field-of-view facets. Only a few of these facets are illustrated illustratively in Figure 1.

[0042] The first facet 20 may be embodied as a macroscopic facet, particularly as a rectangular facet, or as a facet having an arched edge contour or a partial circular edge contour. The first facet 20 may be embodied as a planar facet, or alternatively as a facet having a convex or concave curvature.

[0043] For example, as known from DE102008009600A1, the first facet 20 itself may, in each case, consist of a number of individual mirrors, in particular a number of micromirrors. The first facet mirror 19 may be formed in particular as a micro-electromechanical system (MEMS system). For further details, see DE102008009600A1.

[0044] The deflection mirror US is located between the intermediate focal point of the intermediate focal plane 18 in the beam path of the illumination optical unit 4 and the first facet mirror 19. This deflection mirror US may be implemented as a planar mirror, but may also have a beam shaping effect.

[0045] Within the beam path of the illumination optical unit 4, the second facet mirror 21 is positioned downstream of the first facet mirror 19. When the second facet mirror 21 is positioned on the pupil plane of the illumination optical unit 4, it is also called a pupil facet mirror. The second facet mirror 21 may be positioned at a distance from the pupil plane of the illumination optical unit 4. In that case, the combination of the first facet mirror 19 and the second facet mirror 21 is also called a specular reflector. Specular reflectors are known from U.S. Patent Application Publication No. 2006 / 0132747, EP1614008B1, and U.S. Patent No. 6,573,978.

[0046] The second facet mirror 21 comprises multiple second facets 22. In the case of a pupil facet mirror, the second facets 22 are also called pupil facets.

[0047] The second facet 22 may also be a macroscopic facet, which may have, for example, a circular, rectangular, or hexagonal boundary, or alternatively, a facet composed of micromirrors. In this regard, DE102008009600A1 is similarly referenced.

[0048] The second facet 22 may have a planar reflective surface, or alternatively, a curved reflective surface that is convex or concave.

[0049] As a result, the illumination optical unit 4 forms a dual-faceted system. This basic principle is also known as a fly's eye integrator.

[0050] In some cases, it may be advantageous not to position the second facet mirror 21 precisely on a plane that is optically conjugate to the pupil plane of the projection optical unit 10. More specifically, the pupil facet mirror 22 may be positioned at an angle to the pupil plane of the projection optical unit 10, as described, for example, in DE102017220586A1.

[0051] Each first facet 20 is imaged onto the object field 5 using a second facet mirror 21, and optionally using an imaging optical assembly in the form of a transmission optical unit, which is not shown in Figure 1.

[0052] The transmission optics unit may have exactly one mirror, or alternatively, two or more mirrors, which are arranged in a row within the beam path of the illumination optics unit 4. The transmission optics unit may, in particular, comprise one or two direct incidence mirrors (NI mirrors) and / or one or two oblique incidence mirrors (GI mirrors). In the embodiment shown in Figure 1, the illumination optics unit 4 has exactly three mirrors, namely, downstream of the concentrator 17, a deflection mirror US, a first faceted mirror 19, and a second faceted mirror 21.

[0053] The second facet mirror 21 is either the last beam-shaping mirror or the actual last mirror for the illumination radiation 16 in the beam path upstream of the object field 5, to the extent that no further transmission optics units downstream of the second facet mirror 21 are required. An example of an illumination optics unit 4 without a transmission optics unit is disclosed in Figure 2 of WO2019 / 096654A1.

[0054] The imaging of the first facet 20 onto the object surface 6 using the second facet 22, or using the second facet 22 and the transmission optics unit, is mostly only an approximate image.

[0055] The projection optical unit 10 is equipped with multiple mirrors, namely six mirrors M1 to M6 (see Figure 2), which are numbered sequentially according to their order within the beam path of the projection exposure apparatus 1.

[0056] In the example shown in Figure 1, the projection optics unit 10 comprises six mirrors M1 to M6. Alternative examples with four, five, or other numbers of mirrors Mi are equally possible.

[0057] The projection optics unit 10 is a non-obscured optics unit. None of the mirrors M1 to M6 contain a through aperture for the illumination radiation 16.

[0058] The projection optical unit 10 has an image-side numerical aperture of 0.33. Depending on the embodiment of the projection optical unit 10, the image-side numerical aperture may be in the range of, for example, 0.25 to 0.4. Depending on the embodiment, the image-side numerical aperture of the projection optical unit 10 may also be a different value.

[0059] The reflective surface of mirror Mi is realized as a free-form surface without a rotational symmetry axis. Alternatively, the reflective surface of mirror Mi may be designed as an aspherical surface having exactly one rotational symmetry axis of the reflective surface shape. Similar to the mirrors of illumination optical unit 4, mirror Mi may have a high-reflectivity coating for illumination radiation 16. These coatings may be designed as multilayer coatings having, for example, alternating layers of molybdenum and silicon. Ruthenium coatings are also possible, particularly for grazing incidence mirrors (GI mirrors).

[0060] The projection optics unit 10 brings about a 4:1 size reduction in the x-direction, that is, the direction perpendicular to the scanning direction y. Furthermore, the projection optics unit 10 brings about image inversion in this x-direction. Therefore, the imaging scale β in the x-direction x It is -4.00.

[0061] In the scanning direction y, the projection optical unit 10 also brings about a 4:1 size reduction, but in this case, there is no image inversion (β y (=+4.00).

[0062] The projection optics unit 10 may also have an anamorphic design in an alternative embodiment. In that case, different imaging scales β in the x and y directions may be used. x , β y It has two imaging scales β of the projection optical unit 10. x , β y Preferably (β x ,β y ) = (+ / -4, + / -8).

[0063] Other imaging scales are also possible. Imaging scales with the same sign in the x and y directions are also possible.

[0064] The image field 11 has an x-direction extent of 26 mm and a y-direction extent of 2.5 mm.

[0065] The image field may have a partially ring-shaped embodiment.

[0066] Alternatively, the image field may also have a rectangular embodiment.

[0067] In each case, to form an illumination channel that illuminates the object field 5, one of the pupil facets 22 is assigned to exactly one of the field of view facets 20. In detail, this can produce illumination according to Köhler's principle. The far field of view is decomposed into multiple object fields 5 using the field of view facets 20. Each of the field of view facets 20 generates multiple intermediate focal images in the pupil facets 22 assigned to it.

[0068] The assigned pupil facets 22 cause the field of view facets 20 to be imaged onto the reticle 7 in each case so as to superimpose on each other for the purpose of illuminating the object field 5. The illumination of the object field 5 is particularly uniform as possible, preferably with a uniformity error of less than 2%. Field of view uniformity may be achieved by superimposing different illumination channels.

[0069] The illumination of the entrance pupil of the projection optical unit 10 can be geometrically defined by the arrangement of the pupil facets. The intensity distribution of the entrance pupil of the projection optical unit 10 can be set by selecting the illumination channels, particularly the subset of pupil facets that guide the light. This intensity distribution is also referred to as the illumination setting or illumination pupil filling.

[0070] The uniformity of the pupil in multiple segments of the illumination pupil of the illumination optical unit 4, which is illuminated as defined, can be achieved by redistributing the illumination channels.

[0071] Further aspects and details of the illumination of the object field 5, particularly the entrance pupil of the projection optical unit 10, are described below.

[0072] The projection optical unit 10 may have a concentric entrance pupil. It may be reachable, as in the embodiment of the projection optical unit 10 shown in Figure 2.

[0073] The projection optics unit 10 has an entrance pupil EP (see Figure 1), which is located in the range of 1500 mm to 2000 mm upstream of the object field 5 in the beam path in both the x and y directions, and in particular in the range of 1800 mm to 2200 mm. The arrangement plane of this entrance pupil is shown in EP in Figure 1. Therefore, if the pupil facet mirror 21 is positioned approximately 2 m upstream of the object field 5 in the beam path of the illumination or imaging light 16, the pupil facet mirror 21 satisfies the positional condition of "positioning within the region of the entrance pupil of the projection optics unit".

[0074] The entrance pupil may also be inaccessible in the case of an alternative embodiment of the projection optical unit 10, and as a result, the arrangement surface of the pupil facet mirror 21 will be imaged onto the entrance pupil using other components of the illumination optical unit 4.

[0075] The entrance pupil of the projection optical unit 10 cannot typically be precisely illuminated using the pupil facet mirror 21. When the projection optical unit 10 images the center of the pupil facet mirror 21 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, it is possible to find an area where the distance between the paired aperture rays is minimized. This area corresponds to the entrance pupil or its conjugate area in real space. More specifically, this area has a finite curvature.

[0076] The projection optics unit 10 may have entrance pupils with different orientations for the tangential beam path and the sagittal beam path. In this case, the imaging element, particularly the optical component of the transmission optics unit, must be provided between the second facet mirror 21 and the reticle 7. This optical element can be used to take into account the different orientations of the entrance pupil in the tangential and sagittal directions.

[0077] In the arrangement of the components of the illumination optical unit 4 shown in Figure 1, the pupil facet mirror 21 is positioned at an angle with respect to the object surface 5. The second facet mirror 21 is further positioned at an angle with respect to the arrangement plane defined by the first facet mirror 19.

[0078] Further details regarding the projection optical unit 10 are described later in this specification based on Figure 2.

[0079] The projection optics unit 10 has four NI mirrors (direct incidence mirrors), namely the first two mirrors M1 and M2, and the last two mirrors M5 and M6, in the imaging beam path of the projection optics unit 10. The imaging light 16 is irradiated onto these NI mirrors M1, M2, M5, and M6 at an incidence angle of less than 45°. The maximum incidence angle of the imaging light 16 incident on each NI mirror may be less than 40°, less than 35°, less than 30°, less than 25°, less than 20°, less than 15°, and less than 10°.

[0080] The other mirrors M3 and M4 of the projection optics unit 10 are GI mirrors (mirrors for oblique incidence, oblique incidence mirrors). These mirrors M3 and M4 have incidence angles of illumination light 16 to the mirror that are greater than 45° in each case. The minimum incidence angle incident on each GI mirror may be greater than 50°, greater than 55°, greater than 60°, greater than 65°, greater than 70°, greater than 75°, and greater than 80°.

[0081] Information regarding reflection in GI mirrors (oblique incidence mirrors) can be found in WO2012 / 126867A. Further information regarding the reflectivity of NI mirrors (direct incidence mirrors) can be found in DE10155711A.

[0082] None of the mirrors M1 to M6 have through apertures, and in each case, the mirrors are used in a reflective manner within a continuous region without gaps.

[0083] Figure 2 shows the reflecting surfaces of the calculated mirrors M1 to M6. The reflecting surfaces of the mirrors M1 to M6 used are carried in a known manner by a mirror body (not shown).

[0084] Figure 2 also shows the path of the chief ray of the illumination beam 16 of the illumination optical unit 4 upstream of the object field 5. Upstream of the object field 5, this illumination beam 16 is deflected towards the object field 5 by the last mirror 4a of the illumination optical unit 4. The illumination optical unit mirror 4a is embodied as a GI mirror. The mirror 4a may be embodied as a plane mirror, but alternatively may also have a beam shaping effect on the illumination light beam. The beam path of the illumination beam 16 towards the object field 5 on one side intersects the imaging light beam path between the object field 5 and the mirror M1 on the other side before being reflected by the mirror 4a.

[0085] The object plane 6 and the image plane 12 extend approximately parallel to each other.

[0086] The reflecting surface of the third last mirror M4 in the imaging beam path faces the last mirror M6. As a result, the imaging beam path is guided around the last mirror M6. Between the mirror M2 and the mirror M5, the imaging beam path of the imaging light 16 is guided around the mirror M6 by the two GI mirrors M3 and M4.

[0087] The number of intermediate image planes in the x - direction and the number of intermediate image planes in the y - direction in the beam path between the object field 5 and the image field 11 are different in the case of the projection optical unit 10. In the yz - plane, the projection optical unit 10 has an intermediate image 23 in an intermediate image plane 24 as shown in the meridional cross - sectional view according to Figure 2. For an imaging scale β x =-4.00, in the imaging direction perpendicular thereto, the projection optical unit 10 has no intermediate image. The intermediate image 23 exists in the meridional plane of the projection optical unit 10, that is, in the plane containing the chief ray of the central viewing point of the projection optical unit 10.

[0088] An example of a projection optical unit in which the number of such intermediate images differs in the x and y directions, or in imaging planes perpendicular to each other, is known from U.S. Patent Application Publication No. 2018 / 10656400. Alternatively, the projection optical unit 10 may also be designed to have no intermediate images, or to have the same number of intermediate images in the x and y directions.

[0089] The image plane 12 is the first field of view after the object plane 6 in the xz principal plane of the projection optical unit 10, which is perpendicular to the meridional plane, that is, in the imaging beam path of the projection optical unit 10, which is perpendicular to the yz meridional plane. Therefore, the projection optical unit 10 does not have an intermediate image perpendicular to the meridional plane. Thus, there is an image inversion perpendicular to the meridional plane.

[0090] The intermediate image 23 is located in the region of reflection of the illumination light 16 beam at mirror M3. The distance between mirror M3 and the intermediate image 23 is 0. The distance d between the intermediate image 23 and a further GI mirror M4 along the imaging beam path of the illumination light 16 is 0. 23 Furthermore, the distance between object field 5 and image field 11 in the z-direction is less than 10% of Z. And here again, object field 5 and image field 11 have a distance d in the y-direction. OIS Since they are offset from each other by (object-image offset), this distance Z is smaller than the actual spatial distance between the object field 5 and the image field 11.

[0091] The distance Z is 1621.86 mm. Object-image offset d OIS It is 318.43 mm.

[0092] distance d 23 In the embodiment of the projection optical unit 10 shown in Figure 2, this is 84.65 mm.

[0093] Object-image offset d OIS This object-image offset d is measured between the central field of view point of the object field 5 and the central field of view point of the image field 11, such that it is perpendicular to the perpendicular N of the object plane 6. OIS This is smaller than the distance Z, and therefore smaller than the spatial distance between the object field 5 and the image field 11.

[0094] The two mirrors M1 and M2 have a subtractive deflection effect with respect to the principal ray of the central object's field point.

[0095] The deflection effects of the two GI mirrors M3 and M4 are added together with respect to the principal ray of the central object's field point.

[0096] The second-to-last mirror M5 and the last mirror M6 again add up their deflection effects with respect to the principal rays of the central object's field point.

[0097] Depending on the embodiment of the projection optics unit 10, there may be five or more NI mirrors and / or three or more GI mirrors.

[0098] Intermediate image 23 shows the maximum extent of the last mirror M6 in the meridional plane. M6 The spatial distance d from the last mirror M6 is less than 60% of M6 It has. Here, r M6 This corresponds to the diameter of the last mirror M6 that defines the image-side numerical aperture of the projection optical unit 10.

[0099] distance d M6 In the embodiment of the projection optical unit 10 shown in Figure 2, this is 45.84 mm.

[0100] The image field 11 has an x-direction extent of 26 mm and a y-direction extent of 2.5 mm.

[0101] The field radius of image field 11 is 40 mm.

[0102] The total transmittance of the projection optical unit 10, which is expressed as the product of the EUV reflectances of each mirror M1 to M6 with respect to the illumination light 16 along the imaging beam path passing through the projection optical unit 10, is 11.72% in the projection optical unit 10 shown in Figure 2. Therefore, on average, each of the mirrors M1 to M6 has a reflectance of 70%.

[0103] Therefore, the total transmittance of mirrors M1 to M6, i.e., the total transmittance of the projection optical unit 10, is greater than 10%.

[0104] In the yz plane, the first pupil of the projection optical unit 10 is located between mirrors M1 and M2 in the beam path of the imaging light. The second pupil in the yz plane is located in the same place as the pupil in the xz plane, which is perpendicular to the yz plane, and adjacent to the reflection of the imaging light 16 at mirror M5 in the imaging beam path. In the case of the projection optical unit 10, the aperture can be restricted by an aperture diaphragm, which may restrict the imaging beam path, particularly at the edge, and be attached to mirror M5. If necessary, an internal obscuration may also be defined at mirror M5 using an appropriate diaphragm portion.

[0105] The z-direction distance between mirror M5 and image field 11 is 52 mm.

[0106] The entire projection optical unit 10 can be housed in a cube with edge lengths of 427 mm, 774 mm, and 1371 mm in the x, y, and z directions.

[0107] The imaging beam path of the projection optics unit 10 includes an intersection region 25 where two imaging beam path sections intersect. The first of these intersecting imaging beam path sections is the section between mirror M4 and mirror M5. The second of these intersecting imaging beam path sections is the section between mirror M6 and image field 11.

[0108] The projection optical unit 10 is telecentric on the image side.

[0109] Mirrors M1-M6 are coated to optimize their reflectivity to the imaging light 16. In particular, for GI mirrors, this may be a lanthanum coating, a boron coating, a boron coating with a lanthanum top layer, or a ruthenium coating. Other coating materials, especially lanthanum nitride and / or B4C, may also be used. For oblique incidence mirrors M3 and M4, a coating containing, for example, one layer of boron or lanthanum can be used. The high-reflectivity layers of mirrors M1, M2, M5, and M6, especially for direct incidence, can be constructed as multilayers, with consecutive layers made from different materials. Alternating material layers are also usable. A typical multilayer can have 50 double layers, each made from a boron layer and a lanthanum layer. Layers containing lanthanum nitride and / or boron, especially B4C, may also be used.

[0110] Table 1 below summarizes the parameters of the projection optics unit 10. In addition to the data already described above, Table 1 also specifies the angle of the principal ray of the central field of view point relative to the z axis (5.80°), as well as the usable etendue and mean wavefront aberration RMS values ​​of the projection optics unit.

[0111] [Table 1]

[0112] Tables 2a and 2b below summarize the parameters of the mirrors M1 to M6 of the projection optical unit 10: "maximum incident angle," "extent of the reflective surface in the x-direction," "extent of the reflective surface in the y-direction," and "maximum mirror diameter."

[0113] [Table 2]

[0114] [Table 3]

[0115] The two GI mirrors M3 and M4 have a minimum incident angle of 66.1° and a maximum incident angle of 88.6° for imaging light. The NI mirrors M1, M2, M5, and M6 have a minimum incident angle of 2.6° and a maximum incident angle of 26.5°. The maximum incident angle is less than 12° for the last mirror, M6.

[0116] Mirror M1 has the smallest reflective surface spread in the x-direction, with a spread of approximately 280 mm. Mirror M1 also has the smallest reflective surface spread in the y-direction, with a spread of less than 180 mm.

[0117] Mirrors M1-M6 are realized as free surfaces that cannot be described by rotational symmetry functions. Other embodiments of the projection optical unit 10 are also possible in which at least one of the mirrors M1-M6 is realized as a rotationally symmetric aspherical surface. It is also possible that all of the mirrors M1-M6 are realized as such aspherical surfaces.

[0118] A free surface can be described by the following free surface equation (Equation 1).

number

[0119] The following applies to the parameters of equation (1).

[0120] Z is the sagittal height of the freeform surface at point x,y, and x 2 +y 2 =r 2 Here, r is the distance from the reference axis (x=0; y=0) of the free surface equation.

[0121] In equation (1) for the free surface, C1, C2, C3... represent the coefficients of the free surface series expansion as powers of x and y.

[0122] In the case of a cone-shaped base region, c x , c yc is a constant corresponding to the vertex curvature of the corresponding aspherical surface. Therefore, c x = 1 / R x (1 / RDX) and c y = 1 / R y (1 / RDY) is the relevant value. x and k y (CCX,CCY) correspond to the cone constants of the corresponding aspherical surfaces. Therefore, equation (1) describes a free surface of a biconical shape.

[0123] Alternative freeform surfaces can be generated from rotationally symmetric reference surfaces. Such freeform surfaces for the reflective surfaces of mirrors in the projection optics unit of a microlithography projection exposure apparatus are known from U.S. Patent Application Publication No. 20070058269.

[0124] Alternatively, freeform surfaces can also be described using two-dimensional spline surfaces. Examples include Bézier curves or non-uniform rational basis splines (NURBS). For example, a two-dimensional spline surface can be described by a grid of points on the xy plane and their associated z values, or by these points and their associated gradients. Depending on the type of spline surface, the completed surface can be obtained by interpolation between grid points, for example, using polynomials or functions that have specific properties with respect to their continuity and differentiability. An example of this is an analytical function.

[0125] The optical design data for the reflective surfaces of mirrors M1 to M6 of the projection optical unit 10 can be obtained from the other tables below.

[0126] Table 3 specifies the coordinates of the surface origin of each mirror surface and one area of ​​the object field 5 with respect to the xyz coordinate system of the image field 11.

[0127] The first column specifies the distance of each mirror or object field 5 from the coordinate origin at the center of the image field 11 in the x-direction (first column), y-direction (second column), and z-direction (third column).

[0128] The other columns in Table 3 (Table 3b) further specify the inclination values ​​of the respective surfaces or object fields 5 of mirrors M1 to M6 with respect to the x, y, and z axes. In the embodiment shown in Figure 2, both the object field 5 and the image field 11 are not inclined with respect to the x-axis and extend parallel to each other.

[0129] Table 4 shows, for each mirror M1 to M6, the parameters RDX, RDY, CCX, CCY, and the values ​​of the coefficients C1, C2, C3... of the series expansion of the free surface according to equation (1) above, arranged according to the powers of x and y.

[0130] Table 5 shows the aperture diaphragm AS data of the projection optical unit 10 positioned in the region of mirror M6. This aperture is defined by a polygon, and its x and y values ​​are specified in Table 5.

[0131] [Table 4]

[0132] [Table 5]

[0133] [Table 6] TIFF2026512036000009.tif228153 TIFF2026512036000010.tif223153 TIFF2026512036000011.tif228153 TIFF2026512036000012.tif217153 TIFF2026512036000013.tif228153 TIFF2026512036000014.tif228153 TIFF2026512036000015.tif178155

[0134] [Table 7]

[0135] A Miller with values ​​RDX and RDY having different signs is a saddle point type or minimax basic shape.

[0136] In the case of the projection optical unit 10, the GI mirror M4 is spatially located directly next to the last mirror M6.

[0137] Figure 3 shows a further embodiment of the projection optical unit or imaging optical unit 27, which may be used in the projection exposure apparatus 1 instead of the projection optical unit 10 in the embodiment according to Figure 2. With respect to Figures 1 and 2, and in particular with respect to Figure 2, components and functions corresponding to those already described above are indicated by the same reference numerals and are not described in detail.

[0138] The basic structure of the projection optics unit 27 corresponds to the basic structure of the projection optics unit 10. In the projection optics unit 27, the principal ray angle of the central field of view point with respect to the perpendicular N of the object plane 6 extends in the exact opposite direction compared to the projection optics unit 10, and is 6.07° in the projection optics unit 27. Because of this reversed direction, the illumination beam 16 of the illumination optics unit 4 can be guided without intermediate deflection (see mirror 4a in the embodiment shown in Figure 2), and in particular, can be reflected directly from the second facet mirror 21 toward the object field 5, as shown in Figure 1. Intersection between the illumination light and the imaging light in the beam path just upstream of the object field can be avoided in this design of the projection optics unit 27.

[0139] The distance d from the intermediate image 23 to the GI mirror M4 along the imaging beam path of the illumination light 16 is d. 23In the embodiment of the projection optical unit 27 shown in Figure 3, the distance d between the intermediate image 23 and the last mirror M6 is 137.84 mm. M6 It is 18.00 mm.

[0140] The field radius of image field 11 is 160 mm.

[0141] The following tables summarize the parameters and optical design of the projection optics unit 27. Regarding its structure, these tables correspond to those already described above with respect to Figure 2.

[0142] [Table 8]

[0143] [Table 9]

[0144] [Table 10]

[0145] [Table 11]

[0146] [Table 12]

[0147] [Table 13] TIFF2026512036000023.tif234153 TIFF2026512036000024.tif229153 TIFF2026512036000025.tif234153 TIFF2026512036000026.tif229153 TIFF2026512036000027.tif234153 TIFF2026512036000028.tif229153 TIFF2026512036000029.tif234153 TIFF2026512036000030.tif229153 TIFF2026512036000031.tif234153 TIFF2026512036000032.tif240153 TIFF2026512036000033.tif228155

[0148] [Table 14]

[0149] Figure 4 shows a further embodiment of the projection optical unit or imaging optical unit 28, which may be used in the projection exposure apparatus 1 instead of the projection optical unit 10 in the embodiment according to Figure 2. With respect to Figures 1 to 3, and especially with respect to Figures 2 and 3, components and functions corresponding to those already described above are indicated by the same reference numerals and a detailed description is omitted.

[0150] Regarding the basic structure, the projection optical unit 28 shown in Figure 4 is the same as the projection optical unit 27 shown in Figure 3. The essential difference is that the reflective surface of the mirror M6 of the projection optical unit 28 is significantly larger than, for example, the mirror M1.

[0151] The distance d from the intermediate image 23 to the further GI mirror M4 along the imaging beam path of the illumination light 16 is d.23 In the embodiment of the projection optical unit 28 shown in Figure 4, the distance d between the intermediate image 23 and the last mirror M6 is 161.74 mm. M6 It is 144.96 mm.

[0152] Image field 11 is rectangular.

[0153] The following tables summarize the parameters and optical design of the projection optics unit 28. Regarding its structure, these tables correspond to those already described above with respect to Figure 2.

[0154] [Table 15]

[0155] [Table 16]

[0156] [Table 17]

[0157] [Table 18]

[0158] [Table 19]

[0159] [Table 20] TIFF2026512036000041.tif228153 TIFF2026512036000042.tif222153 TIFF2026512036000043.tif229153 TIFF2026512036000044.tif217153 TIFF2026512036000045.tif228153 TIFF2026512036000046.tif229153 TIFF2026512036000047.tif228153 TIFF2026512036000048.tif229153 TIFF2026512036000049.tif206155

[0160] [Table 21]

[0161] The projection optical unit 28 has an image field with an extension of 52 mm in the x-direction and an extension of 2.0 mm in the y-direction. Therefore, the image field 11 of the projection optical unit 28 has a maximum extension greater than 26 mm.

[0162] In the case of the projection optical unit 28, the arrangement surface P of the aperture diaphragm AP. AP However, it is located between mirrors M5 and M6 in the beam path.

[0163] Figures 5 and 6 show further embodiments of the projection optical unit or imaging optical unit 29, which may be used in the projection exposure apparatus 1 instead of the projection optical unit 10 in the embodiment according to Figure 2. With respect to Figures 1 to 3, and especially with respect to Figures 2 and 3, components and functions corresponding to those already described above are indicated by the same reference numerals and a detailed description is omitted.

[0164] From the xz plane view in the sagittal direction of the projection optical unit 29 shown in Figure 6, it can be inferred that there is no sagittal intermediate image at the position of the meridional intermediate image 23, i.e., in the region of reflection at mirror M4.

[0165] Overall, the projection optical unit 29 has a compact form, meaning that the spatial requirements regarding the installation space cube are relatively low.

[0166] The distance d from the intermediate image 23 to the further GI mirror M4 along the imaging beam path of the illumination light 16 is d. 23 In the embodiment of the projection optical unit 29 shown in Figure 5 / 6, the distance d between the intermediate image 23 and the last mirror M6 is 39.86 mm. M6 It is 60.59 mm.

[0167] Image field 11 is rectangular.

[0168] The following tables summarize the parameters and optical design of the projection optics unit 29. Regarding its structure, these tables correspond to those already described above with respect to Figure 2.

[0169] [Table 22]

[0170] [Table 23]

[0171] [Table 24]

[0172] [Table 25]

[0173] [Table 26]

[0174] [Table 27] TIFF2026512036000057.tif234153 TIFF2026512036000058.tif234153 TIFF2026512036000059.tif229153 TIFF2026512036000060.tif234153 TIFF2026512036000061.tif228153 TIFF2026512036000062.tif229153 TIFF2026512036000063.tif228153 TIFF2026512036000064.tif229153 TIFF2026512036000065.tif150155

[0175] [Table 28]

[0176] Figure 7 shows a further embodiment of the projection optical unit or imaging optical unit 30, which may be used in the projection exposure apparatus 1 instead of the projection optical unit 10 in the embodiment shown in Figure 2. With respect to Figures 1 to 3, and especially with respect to Figures 2 and 3, components and functions corresponding to those already described above are indicated by the same reference numerals and a detailed description is omitted.

[0177] In projection optical unit 30, the imaging light 16 is input and coupled to the second mirror M2 via the first mirror M1 from the other side in the y-direction, compared to projection optical units 10 and 27-29. This results in a large object-image offset d of approximately 950 mm in the case of projection optical unit 30. OIS This results in the following: The z-direction distance between mirror M1 and the image plane 12 is slightly greater than the z-direction distance from the image plane 12 to the second-to-last mirror M6. Consequently, the portion of the imaging beam path between the object field 5 and mirror M1 on one side, and the portion of the imaging beam path between mirrors M1 and M2 on the other side, are larger than all other beam path portions between subsequent adjacent mirrors, and also larger than the beam path portion between mirror M6 and the image field 11.

[0178] The distance d from the intermediate image 23 to the further GI mirror M4 along the imaging beam path of the illumination light 16 is d. 23 In the embodiment of the projection optical unit 30 shown in Figure 7, the distance d between the intermediate image 23 and the last mirror M6 is 56.22 mm. M6 It is 84.13 mm.

[0179] The projection optics unit 30 is telecentric with good approximation on the object side.

[0180] Image field 11 is rectangular.

[0181] The following tables summarize the parameters and optical design of the projection optics unit 30. Regarding its structure, these tables correspond to those already described above with respect to Figure 2.

[0182] [Table 29]

[0183] [Table 30]

[0184] [Table 31]

[0185] [Table 32]

[0186] [Table 33]

[0187] [Table 34] TIFF2026512036000073.tif234153 TIFF2026512036000074.tif234153 TIFF2026512036000075.tif234153 TIFF2026512036000076.tif234153 TIFF2026512036000077.tif229153 TIFF2026512036000078.tif234153 TIFF2026512036000079.tif89155

[0188] [Table 35]

[0189] The projection optical unit 30 has a relatively large spread of the reflective surface of the mirror M1 in both the x and y directions, with both spread directions being greater than 200 mm, and especially greater than 250 mm. This reduces the thermal load on the mirror M1 due to residual absorption of the imaging light 16.

[0190] Compared with the projection optical unit described above, due to the different bending in mirror M2, the incident angle in this mirror M2 of the projection optical unit 30 is relatively small and less than 15°.

[0191] FIG. 8 shows a further embodiment of the projection optical unit or the imaging optical unit 31, which can be used in the projection exposure apparatus 1 instead of the projection optical unit 10 of the embodiment according to FIG. 2. With respect to FIGS. 1 to 3, particularly with respect to FIGS. 2 and 3, the components and functions corresponding to those already described above are denoted by the same reference numerals, and the detailed description thereof is omitted.

[0192] In principle, with regard to the arrangement of the mirrors, the projection optical unit 31 corresponds to the projection optical unit 30 according to FIG. 7.

[0193] In contrast to the projection optical unit 30, the projection optical unit 31 has an entrance pupil disposed at a distance of approximately 1750 mm upstream of the object field 5 in the imaging light beam path. And the second facet mirror 21 embodied as a pupil facet mirror can be disposed there.

[0194] The distance d of the further GI mirror M4 from the intermediate image 23 along the imaging beam path of the illumination light 16 23 is 87.99 mm in the case of the embodiment according to FIG. 8 of the projection optical unit 31, and the distance d M6 between the intermediate image 23 and the last mirror M6 is​​​​​​​​​​​​​​​​​

[0198] Table 37

[0199] Table 38

[0200] Table 39

[0201] Table 40

[0202] Table 41 TIFF2026512036000087.tif217153 TIFF2026512036000088.tif217153 TIFF2026512036000089.tif217153 TIFF2026512036000090.tif217153 TIFF2026512036000091.tif206155

[0203] Table 42

[0204] FIG. 9 shows a further embodiment of the projection optical unit or imaging optical unit 32, which can be used in the projection exposure apparatus 1 instead of the projection optical unit 10 of the embodiment according to FIG. 2. With respect to FIGS. 1 to 3, particularly with respect to FIGS. 2 and 3, components and functions corresponding to those already described above are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0205] In the projection optical unit 32, the mirrors M1, M3, M5, and M6 are embodied as NI mirrors, and the mirrors M2 and M4 are embodied as GI mirrors.

[0206] In the imaging beam path of the projection optical unit 32, virtual intermediate images 23 are respectively assigned to the reflections at the two GI mirrors M2 and M4. In FIG. 9, an example of the intermediate image 23 located next to the mirror M2 is used to explain this. Therefore, with respect to this virtual intermediate image 23, in the projection optical unit 32, the intermediate image 23 in the meridional plane yz of the projection optical unit 32 also has a spatial distance of less than 10% of the distance between the object field 5 and the image field 11 from the nearest GI mirror, for example, the mirror M2. V is assigned, which is explained in FIG. 9 using the example of the intermediate image 23 located next to the mirror M2. V Therefore, with respect to this virtual intermediate image 23, V in the projection optical unit 32, the intermediate image 23 in the meridional plane yz of the projection optical unit 32 V also has a spatial distance of less than 10% of the distance between the object field 5 and the image field 11 from the nearest GI mirror, for example, the mirror M2.

[0207] The distance d from the intermediate image 23 along the imaging beam path of the illumination light 16 to the further GI mirror M4 23 is 142.78 mm in the case of the embodiment of the projection optical unit 32 according to FIG. 9.

[0208] The image field 11 is rectangular.

[0209] The following table is a summary of the parameters and optical design of the projection optical unit 32. Regarding its structure, these tables correspond to those already described above with respect to FIG. 2.

[0210]

Table 43

[0211] Table 44

[0212] Table 45

[0213] Table 46

[0214] Table 47

[0215] Table 48 TIFF2026512036000099.tif234153 TIFF2026512036000100.tif228153 TIFF2026512036000101.tif229153 TIFF2026512036000102.tif223153 TIFF2026512036000103.tif228153 TIFF2026512036000104.tif229153 TIFF2026512036000105.tif228153 TIFF2026512036000106.tif229153 TIFF2026512036000107.tif167155

[0216] [Table 49]

[0217] In the projection optics unit 32, there is no intermediate image between the object field 5 and the image field 11. Therefore, in the case of the projection optics unit 32, the image plane 12 is the first field of view downstream of the object plane 6 in the imaging beam path, with respect to both the meridional plane and the sagittal plane perpendicular to the meridional plane.

[0218] In the projection optics unit 32, the NI mirror M6 is positioned between the two GI mirrors M2 and M4. The two GI mirrors M2 and M4 are each located near a virtual intermediate image.

[0219] Depending on the embodiment of the projection optics unit described above, the projection optics unit may have a different number of NI mirrors and / or GI mirrors, for example, exactly one GI mirror or exactly three GI mirrors. Three or fewer or five or more NI mirrors are also possible, for example, two, three, or five NI mirrors.

[0220] To manufacture microstructures or nanostructure components, the projection exposure apparatus 1 is used as follows: First, a reflective mask 7 or reticle and a substrate or wafer 13 are provided. Then, the structure on the reticle 7 is projected onto the photosensitive layer of the wafer 13 using the projection exposure apparatus 1. Subsequently, the microstructure or nanostructure on the wafer 13, and thus the microstructure component, is manufactured by developing the photosensitive layer.

Claims

1. An imaging EUV optical unit (10; 27; 28; 29; 30; 31; 32) for imaging the object field (5) onto the image field (11), - A plurality of mirrors (M1 to M6) are provided to guide EUV imaging light (16) with a wavelength shorter than 30 nm along the imaging beam path from the object field (5) to the image field (11), - The plurality of mirrors (M1 to M6) include at least two NI mirrors (M1, M2, M5, M6; M1, M3, M5, M6) and at least two GI mirrors (M3, M4; M2, M4), - The second to last mirror (M5) in the imaging beam path is designed as an NI mirror. - The second-to-last mirror (M5) in the imaging beam path does not have a passing aperture for the imaging light (16), - The last mirror (M6) in the imaging beam path is designed as an NI mirror. - The last mirror (M6) in the imaging beam path does not have a passing aperture for the imaging light (16), - An imaging EUV optical unit (10; 27; 28; 29; 30; 31; 32) in which the reflective surface of the third-to-last mirror (M4) in the imaging beam path faces the last mirror (M6) in the imaging beam path.

2. The object-image offset (d) is between the central object field point and the central image field point, which are perpendicular to the perpendicular (N) of the object plane (6). OIS The imaging EUV optical unit according to claim 1, characterized in that the distance between the object field (5) and the image field (11) is smaller than the distance between the object field (5) and the image field (11).

3. At least one intermediate image (23;23) in at least one imaging optical plane (yz) V ) includes the principal ray of the central field of view point, and at least one of the GI mirrors (M3, M4; M2, M4) is positioned along the imaging beam path such that the intermediate image (23; 23) is less than 10% of the distance between the object field (5) and the image field (11). V Distance to (d) 23 The imaging EUV optical unit according to claim 1 or 2, characterized by having ).

4. The imaging EUV optical unit according to any one of claims 1 to 3, characterized in that the second-to-last mirror (M5) and the last mirror (M6) have their deflection effects added together with respect to the principal ray of the central object field point.

5. An imaging EUV optical unit according to any one of claims 1 to 4, comprising at least four NI mirrors (M1, M2, M5, M6; M1, M3, M5, M6).

6. An imaging EUV optical unit according to any one of claims 1 to 5, characterized by exactly two GI mirrors (M3, M4; M2, M4).

7. The intermediate image (23) is located in the meridional plane (yz) of the imaging EUV optical unit (10; 27; 28; 29; 30; 31), and the intermediate image (23) is located at a spatial distance (d) from the last mirror (M6) that is less than 60% of the maximum extent of the last mirror (M6) in the meridional plane (yz). M6 The imaging EUV optical unit according to any one of claims 1 to 6, characterized by having ).

8. The imaging EUV optical unit according to any one of claims 1 to 7, characterized in that the image plane (12) of the imaging optical unit in the imaging beam path, which is perpendicular to the meridional plane (yz), is the first field of view downstream of the object plane (6) of the imaging optical unit.

9. The imaging EUV optical unit according to any one of claims 1 to 8, characterized in that the total transmittance of the plurality of mirrors (M1 to M6) to the EUV imaging light is greater than 10%.

10. The imaging EUV optical unit according to any one of claims 1 to 9, characterized in that the image field (11) of the imaging optical unit (28) has the maximum extent on the image plane (12) which is larger than 26 mm.

11. - An illumination optical unit (4) for illuminating the object field (5) with imaging light (16), - An imaging optical unit (10) according to any one of claims 1 to 10 and An optical system equipped with

12. A projection exposure apparatus comprising the optical system according to claim 11 and an EUV light source (3).

13. - A method step of providing the reticle (7) and wafer (13), - A method of projecting a structure on the reticle (7) onto the photosensitive layer of the wafer (13) using the projection exposure apparatus described in claim 12, - A method for generating microstructures and / or nanostructures on the wafer (13) A method for manufacturing structural components, including [the specified element].

14. A structural component manufactured according to the method of claim 13.

Images