Imaging Optical Unit

Abstract

The imaging optical unit (7) comprises a number of mirrors (M1-M8) for imaging the object field (4) in the object plane (5) into an image field (8) in the image plane (9). The image-side numerical aperture is greater than 0.55. The ratio between the object / image offset a and the meridional transverse dimension c is at least 0.5. The ratio between the working distance b between the object plane (5) and the reflecting part of one of the mirrors (M4) closest to the object plane and the meridional transverse dimension c is at least 0.05. The working distance b is at least 270 mm. This results in an imaging optical unit, the use of which is as easy as possible in a projection exposure apparatus, in particular for EUV projection lithography.

Description

[Technical field]

[0001] This patent application claims priority from German patent application DE102021205774.8, the contents of which are incorporated herein by reference.

[0002] The present patent application relates to an imaging optical unit comprising a plurality of mirrors for imaging an object field into an image field, the mirrors of said imaging optical unit being capable of being measured by an inspection optical unit. Furthermore, the invention relates to an optical system comprising such an imaging optical unit, an illumination system comprising such an optical system, a projection exposure apparatus comprising such an illumination system, a method for producing a microstructured or nanostructured component and a microstructured or nanostructured component produced by any such method. [Background technology]

[0003] Imaging or projection optical units of the type mentioned in the introduction are known from DE 10 2019 219 209 A1, DE 10 2019 208 961 A1, WO 2009 / 010213 A1, US 2016 / 0085061 (A1), DE 10 2012 202 675 A1, DE 10 2009 011 328 A1, US 8,027,022 (B2) and US 6,577,443 (B2). An illumination optical unit for a projection exposure apparatus is known from DE 10 2009 045096. Summary of the Invention

[0004] The object of the invention is to develop an imaging optical unit of the type mentioned in the introduction in such a way that the use of the imaging optical unit in a projection exposure apparatus, in particular for EUV projection lithography, is as easy as possible to handle.

[0005] According to the present invention, it has been recognized that a dimensional ratio of an imaging optical unit having as large a ratio as possible between object / image offset and meridional transverse dimension, on the one hand, and between working distance and meridional transverse dimension, on the other hand, results in an imaging optical unit that ensures that the wafer holder does not collide with optical components of the illumination optical unit upstream of the imaging optical unit (conditions of relatively large object / image offset), that sufficient installation space adjacent to the object surface is available for an object holder designed to optionally exchange the object (relatively large working distance), and that a possible vacuum container in which all optical units of the projection exposure apparatus are accommodated does not have to be manufactured with undesirably large dimensions (relatively small meridional transverse dimension).

[0006] The object with the structures to be imaged or a part thereof can be arranged in the object field, The substrate or a substrate part onto which the object structures are imaged can be arranged in the image field.

[0007] The imaging optical unit according to claim 1 meets these three criteria in a manageable form with given dimensional ratios.

[0008] The absolute measurements of the object / image offset, working distance and meridional transverse dimension as claimed in claims 2 to 4 have been found to be particularly advantageous.

[0009] The advantages of the invention are particularly evident in the case of an anamorphic imaging optical unit as defined in claim 5. A corresponding anamorphic optical unit is known from US Pat. No. 9,366,968.

[0010] An imaging optical unit according to claim 6 enables high quality imaging of structures.

[0011] An imaging optical unit as claimed in claim 7 facilitates good imaging correction over a given image field size.

[0012] The imaging optical units according to claims 8 to 9 have proven their worth in practice. There may be more than four GI mirrors, these may for example amount to six or eight in total. There may be more than four NI mirrors, these may for example amount to four in total.

[0013] The advantages of the optical system according to claim 10, the illumination system according to claim 11, the projection exposure apparatus according to claim 12, the production method according to claim 13 and the microstructured or nanostructured component according to claim 14 correspond to those already explained above with reference to the imaging optical unit according to the invention.

[0014] In particular, semiconductor components, for example memory chips, can be produced.

[0015] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. [Brief description of the drawings]

[0016] [Figure 1] 1 illustrates a schematic diagram of a projection exposure apparatus for EUV microlithography; [Diagram 2] 2 shows an embodiment of an imaging optical unit which can be used as a projection lens in the projection exposure apparatus described in FIG. 1 in a meridional section, in which the imaging beam paths of the chief rays and the upper and lower coma rays of three selected field points are shown. [Diagram 3] 1. In a view similar to FIG. 2, a further embodiment of an imaging optical unit that can be used as the projection optical unit in the projection exposure apparatus of FIG. [Figure 4] 1. In a view similar to FIG. 2, a further embodiment of an imaging optical unit that can be used as the projection optical unit in the projection exposure apparatus of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The microlithographic projection exposure apparatus 1 comprises a light source 2 for illumination or imaging light 3. The light source 2 is for example an EUV light source generating light in a wavelength range between 5 nm and 30 nm, in particular between 5 nm and 15 nm. In particular, the light source 2 can be a 13.5 nm wavelength light source or a 6.9 nm wavelength light source. Other EUV wavelengths are also possible. In general, the illumination light 3 guided in the projection exposure apparatus 1 can furthermore have any desired wavelength, for example a visible wavelength or other wavelengths that can otherwise be used in microlithography (for example DUV, deep ultraviolet) and for which suitable laser and / or LED sources are available (for example 365 nm, 248 nm, 193 nm, 157 nm, 129 nm, 109 nm). The beam path of the illumination light 3 is shown very diagrammatically in FIG. 1.

[0018] An illumination optical unit 6 is used to direct illumination light 3 from the light source 2 to an object field 4 in an object plane 5. Using a projection or imaging optical unit 7, the object field 4 is imaged into an image field 8 in an image plane 9 using a given scale, possibly an anamorphic scale.

[0019] In order to facilitate the description of the projection exposure apparatus 1 and the various embodiments of the projection optical unit 7, a Cartesian xyz coordinate system is shown in the figures, from which the respective positional relationships of the components shown in the figures are clear. In figure 1, the x-direction runs into the figure perpendicular to the plane of the drawing, the y-direction runs to the left and the z-direction runs upwards.

[0020] The object field 4 and the image field 8 are rectangular. Alternatively, the object field 4 and the image field 8 can also have a bent or curved embodiment, i.e. in particular a partial ring shape. The object field 4 and the image field 8 have an x / y aspect ratio greater than 1. The object field 4 therefore has a longer object field dimension in the x direction and a shorter object field dimension in the y direction. These object field dimensions extend along the field coordinates x and y.

[0021] One of the exemplary embodiments shown in FIGS. 2, 3 and 4, which will be explained in more detail further below, can be used for the projection optical unit 7.

[0022] The projection optical unit 7 according to Fig. 2 has an anamorphic embodiment. In the yz plane, i.e. in the meridional plane of the section according to Fig. 2, the projection optical unit 7 has a 1 / 8 scale |β y In the meridian plane yz, the object field 4 is therefore imaged onto the image field with a reduction of 1 / 8. x | is 1 / 4 in the sagittal plane xz perpendicular to the meridian plane. In this xz plane, the object field 4 is imaged with a reduction of 1 / 4 into an image field 8 between the object plane 5 and the image plane 9. As will be explained further below on the basis of further exemplary embodiments, other integer or non-integer absolute scales β x , β y is also possible.

[0023] The image field 8 has an x ​​dimension of, for example, 26 mm and a y dimension of, for example, 2 mm.

[0024] In the embodiment of the projection optical unit 7 according to Fig. 7 onwards, the image plane 9 is arranged parallel to the object plane 5. What is imaged in this case is a part of a reflective mask 10, also called a reticle, which coincides with the object field 4. The reticle 10 is held by a reticle holder 10a. The reticle holder 10a is displaced by a reticle displacement drive 10b.

[0025] Imaging via the projection optical unit 7 is realised on the surface of a substrate 11 in the form of a wafer held by a substrate holder 12. The substrate holder 12 is displaced by a wafer or substrate displacement drive 12a.

[0026] 1 shows diagrammatically a beam 13 of illumination light 3 entering the projection optical unit 7 between a reticle 10 and the projection optical unit 7, and a beam 14 of illumination light 3 exiting the projection optical unit 7 between the projection optical unit 7 and a substrate 11. The numerical aperture (NA) on the image field side of the projection optical unit 7 is not reproduced to scale in FIG.

[0027] The projection exposure apparatus 1 is of the scanner type. Both the reticle 10 and the substrate 11 are scanned in the y direction during operation of the projection exposure apparatus 1. A stepper type of projection exposure apparatus 1 is also possible, in which step-like displacements in the y direction of the reticle 10 and the substrate 11 are performed between individual exposures of the substrate 11. These displacements are performed synchronously with one another by suitable activation of the displacement drives 10b and 12a.

[0028] Fig. 2 shows the optical design of a first embodiment of the projection optical unit 7. Fig. 2 shows the beam paths of three individual light rays 29 originating in each case from three object field points spaced apart from one another in the y-direction of Fig. 2. Depicted are the chief ray 30, i.e. the individual light rays 29 passing through the center of the pupil in the pupil plane of the projection optical unit 7, and in each case the upper and lower coma rays, i.e. the rays passing through the upper and lower edges of the pupil of these two object field points, respectively. Proceeding from the object field 4, the chief ray 30 includes an angle CRAO of 5.05° with the normal to the object plane 5.

[0029] The projection optical unit 7 has an image-side numerical aperture of 0.75.

[0030] The projection optical unit 7 according to Fig. 2 has a total of eight mirrors, which are numbered M1 to M8 in the order of the beam paths of the individual light rays 29 proceeding from the object field 4. The imaging optical unit 7 can also have a different number of mirrors, for example four mirrors, six mirrors, nine mirrors, ten mirrors, eleven mirrors or even more mirrors.

[0031] Fig. 2 shows the calculated reflecting surfaces of the mirrors M1-M8. Optionally, only parts of these calculated reflecting surfaces are used. Only the areas of this actually used reflecting surface actually exist in the real mirrors M1-M8. These used reflecting surfaces are carried by the mirror body in a manner known per se.

[0032] In the projection optical unit 7 according to Fig. 2, the mirrors M1, M4, M7 and M8 are configured as mirrors for normal incidence (NI mirrors), i.e. as mirrors at which the imaging light 3 is incident with an angle of incidence smaller than 45°. Overall, the projection optical unit 7 according to Fig. 2 therefore has four mirrors M1, M4, M7 and M8 for normal incidence.

[0033] The mirrors M2, M3, M5 and M6 are mirrors for grazing incidence of the illumination light 3 (GI mirrors), i.e. mirrors at which the illumination light 3 is incident with an angle of incidence greater than 60°. Typical angles of incidence of the individual rays 29 of the imaging light 3 on the mirrors M2, M3, M5 and M6 for grazing incidence are in the region of 80°. Overall, the projection optical unit 7 according to Fig. 2 has exactly four mirrors M2, M3, M5 and M6 for grazing incidence.

[0034] The mirrors M2, M3 on the one hand and M5, M6 on the other hand are designed as consecutive mirror pairs and reflect the imaging light 3 in such a way that the reflection angles of the individual rays 29 at each mirror of the pair M2, M3 on the one hand and the pair M5, M6 on the other hand are summed, i.e., amplified with respect to the deflection effect.

[0035] The mirrors M1-M8 carry a coating that optimizes the reflectivity of the mirrors M1-M8 for the imaging light 3. This can be a ruthenium coating, a molybdenum coating, or a molybdenum coating with a top layer of ruthenium. For the mirrors M2, M3, M5, and M6 for grazing incidence, a coating with one ply from molybdenum or ruthenium can be used, for example. In particular, these highly reflective layers of the mirrors M1, M4, M7, and M8 for normal incidence can be configured as multi-ply layers, with successive layers being made from different materials. Alternating material layers can also be used. A typical multi-ply layer can have 50 bilayers, each made with a layer of molybdenum and a layer of silicon. The multi-ply layer may also be provided with an additional capping layer, for example made from ruthenium.

[0036] For the purpose of calculating the overall reflectance of the projection optical unit 7, the system transmittance can be calculated as follows: The mirror reflectances are determined for each mirror surface based on the angle of incidence of the guide ray, i.e. the chief ray at the central object field point, and are combined by multiplication to form the system transmittance.

[0037] Further information regarding system transmittance can be found in US Patent Application Publication No. 2016 / 0085061(A1).

[0038] Further information on reflection in GI mirrors (grazing incidence mirrors) can be found in WO2012 / 126867. Further information on the reflectivity of NI mirrors (normal incidence mirrors) can be found in DE10155711A.

[0039] Mirror M8, i.e. the last mirror upstream of the image field 8 in the imaging beam path, has a passage opening 30a for the passage of the imaging light 3 reflected from the penultimate mirror M6 towards the penultimate mirror M7. Mirror M8 is used to reflect around the passage opening 30a. All other mirrors M1-M7 are used to reflect in areas without passage openings and are continuous without gaps.

[0040] A stop AS is arranged in the imaging beam path between mirrors M6 and M7, said stop having both the functions of aperture stop and of obscuration stop, whereby it firstly specifies the image-side numerical aperture of the projection optical unit 7 and secondly specifies the size of the inner pupil obscuration.

[0041] The aperture AS may be designed as a split aperture, as known from US Pat. No. 10,527,832.

[0042] The projection optical unit 7 is approximately telecentric on the object side. If the imaging beam path is considered only with respect to the individual rays passing through the object field 4, the entrance pupil is arranged 4052.44 mm downstream of the object field 5 in the xz-plane and 41876.50 mm downstream of the object field 4 in the yz-plane.

[0043] In the projection optical unit 7, a pupil plane lies in the beam path of the imaging light 3 between mirror M1 and mirror M2.

[0044] A first intermediate image plane is present in the beam path between mirror M2 and mirror M3. A further intermediate image plane is present in the beam path between mirror M5 and mirror M6. In the case of the projection optical unit 7, there are no intermediate image planes in the area of ​​the passage opening 30a. The number of intermediate image planes differs from the number of intermediate images in the meridian plane according to FIG. 2 and the number of intermediate images in the plane perpendicular thereto. Such projection optical units with different numbers of intermediate images in mutually perpendicular planes are known in principle from WO 2016 / 166080 A1 and DE 102015226531 A1.

[0045] A stop AS is arranged in the beam path between mirror M7 and mirror M8 in the region of a further pupil surface of the projection optical unit 7.

[0046] The mirrors M1-M8 are embodied as freeform surfaces that cannot be described by a rotationally symmetric function. Other embodiments of the projection optical unit 7 are also possible, in which at least one of the mirrors M1-M8 is embodied as a rotationally symmetric aspheric surface. It is also possible for all mirrors M1-M8 to be embodied as such aspheric surfaces.

[0047] A free-form surface can be described by the following free-form surface equation (Equation 1).

number

[0048] The following applies to the parameters of equation (1):

[0049] Z is the sagittal height of the freeform surface at the point x, y, where x 2 +y 2 =r 2 Here, r is the distance from the reference axis (x=0; y=0) of the free-form surface formula. In the free-form surface formula (1), C1, C2, C3... represent the coefficients of the free-form surface series expansion in the powers of x and y.

[0050] For cone-shaped base regions, c x , c y is a constant corresponding to the vertex curvature of the corresponding aspheric surface. Therefore, c x =1 / R x and c y =1 / R y applies. k x and k y respectively correspond to the conic constants of the corresponding aspheric surface. Thus, equation (1) describes a biconical freeform surface.

[0051] Alternatively possible freeform surfaces can be generated from rotationally symmetric reference surfaces. Such freeform surfaces for reflective surfaces of mirrors of a projection optical unit of a microlithographic projection exposure apparatus are known from US 2007-0058269 A1.

[0052] Alternatively, freeform surfaces can also be described using two-dimensional spline surfaces. Examples of this are Bézier curves or non-uniform rational B-splines (NURBS). As an example, two-dimensional spline surfaces can be described by a grid of points in the xy plane and the associated z values, or by these points and their associated gradients. Depending on the respective type of spline surface, the complete surface is obtained by interpolating between the grid points using polynomials or functions that have specific properties, for example in terms of continuity and their differentiability. Examples of this are analytic functions.

[0053] The optical design data of the reflecting surfaces of the mirrors M1 to M8 (=M01 to M08) of the projection optical unit 7 can be seen from the following table.

[0054] The first of these tables lists the vertex radius (Radiusx=R x , Radiusy=R y ) and refractive power values ​​(Powerx, Powery). A negative value of the radius means a curve that is concave towards the incident illumination light 3 in the cross section of the respective surface with the considered surface (xz, yz) extended by the surface normal of the vertex with the respective direction of curvature (x, y). The two radii Radiusx, Radiusy may explicitly have different signs.

[0055] The vertex at each optical surface is defined as the point of incidence of a guide ray that travels from the object field centre to the image field 8 along the plane of symmetry x=0, ie the plane of the drawing in FIG. 2 (the meridian plane).

[0056] Power at the apex Powerx (P x ), Powery(P y )teeth,

number

[0057] Here, AOI represents the angle of incidence of the guide ray with respect to the surface normal.

[0058] The second table shows how each mirror is decentered in the y direction (D y ) and displaced in the z direction (D z ), tilted (α x , α y , α z ) absolute values ​​are specified, which correspond to the translation and tilt in the case of the freeform surface design method. Here, the displacement is performed along the y direction and in the z direction in mm, and the tilt is performed around the x axis, around the y axis and around the z axis. In this case, the rotation angle is specified in degrees. First, the decentering is performed, followed by the tilting. The reference plane during the decentering is in each case the first plane of the specified optical design data. The decentering in the y and z directions is also specified relative to the object field 4 (reticle). In addition to the values ​​assigned to the individual mirrors M1-M8, the table further tabulates the object plane (reticle) as the first plane, the image plane (wafer) as the final plane and the diaphragm plane (denoted "diaphragm") as the arrangement plane of the aperture or obscuration diaphragm.

[0059] The third table (Table 3a to Table 3c) shows the polynomial x for mirrors M1 to M8. k , y l The free-form surface coefficients C are assigned to n Specify the coefficient C that is not tabulated in the table. n each have a value of 0.

[0060] The fourth table specifies the boundaries of the aperture AS as broken lines in local coordinates xy. As mentioned above, the aperture is decentered and tilted. In this table, the coordinates are specified in two columns. The first column (consisting of x and y coordinates) contains the coordinates of the corners 1 to M / 2 of the polygon, and the second column contains the coordinates of the corners N / 2+1 to N. Each row therefore contains four numbers, specifically xi , y i , x i+N / 2 , y i+N / 2 Includes.

[0061] [Table 1]

[0062] [Table 2]

[0063] [Table 3] TIFF2024522609000007.tif229154 TIFF2024522609000008.tif184154

[0064] [Table 4] TIFF2024522609000010.tif229157 TIFF2024522609000011.tif178157

[0065] [Table 5] TIFF2024522609000013.tif229153 TIFF2024522609000014.tif229153 TIFF2024522609000015.tif222153

[0066] [Table 6] TIFF2024522609000017.tif229153 TIFF2024522609000018.tif229153 TIFF2024522609000019.tif159153

[0067] The mirrors M1, M3, M4, M5 and M8 have a negative value for the radius, i.e. they are in principle concave mirrors. The mirrors M2, M6 and M7 have a positive value for the radius, i.e. they are in principle convex mirrors. The mirrors M1 to M8 of the projection optical unit according to FIG. 2 have R x , R y They have no radius value, and therefore none of the mirrors M1 to M8 has a saddle shape in principle.

[0068] The boundary of the stop surface of the stop (see also table 4 for Fig. 2) arises from the intersection on the stop surface of all rays of the illumination light 3 propagating on the image side at the field centre point in the direction of the stop surface with a complete image-side telecentric aperture. If the stop is embodied as an aperture stop, the boundary is the inner boundary.

[0069] The aperture AS may be in a plane or in an otherwise three-dimensional embodiment. The extent of the aperture AS may be smaller in the scan direction (y) than in the cross-scan direction (x).

[0070] Further data for the projection optical unit 7 arises from Table 5 below.

[0071] [Table 7]

[0072] The projection optical unit 7 has an object / image offset a between a separation plane 31a and the center of the image field 8. The center of the object field 4 is located at the separation plane 31a. The separation plane 31a extends parallel to the xz plane. The separation plane 31a is perpendicular to the yz meridian plane of the imaging optical unit 7. The object / image offset a is 1650 mm for the projection optical unit 7.

[0073] The used reflective surface of mirror M4 is closest to the object plane 5. It therefore defines a working distance b between this used reflective surface of mirror M4 and the object plane 5. The reflective part of mirror M4 that is closest to the object plane 5 is considered to be within the definition of the working distance b. The working distance b is 275 mm in the case of the projection optical unit 7.

[0074] The meridional transverse dimension c is defined between the separation surface 31a and the reflecting part of one of the mirrors furthest from said separation surface, again in this case mirror M4. The meridional transverse dimension c is 2154 mm in the case of the projection optical unit 7.

[0075] The dimensional ratio a / c is 0.76 for the projection optical unit 7. The dimensional ratio b / c is 0.128 for the projection optical unit 7.

[0076] The projection optical unit 7 is designed for a wavelength of the illumination light 3 of 13.5 nm.

[0077] The mean wavefront aberration RMS (scanning wavefront deviation) is a measure for the imaging quality of the projection optical unit 7 .

[0078] The projection optical unit 7 is at least approximately telecentric on the image side.

[0079] Figure 3 shows a further embodiment of a projection optical unit or imaging optical unit 31 which can be used in the projection exposure apparatus 1 instead of the projection optical unit 7. Components and features which correspond to those already described above with reference to Figures 1 and 2 carry the same reference numbers and will not be discussed in detail again.

[0080] The projection optical unit 31 has an image-side numerical aperture of 0.75.

[0081] The projection optical unit 31 has a total of eleven mirrors M1 to M11. The mirrors M1, M10 and M11 are embodied as mirrors for normal incidence. The mirrors M2 to M9 are embodied as mirrors for grazing incidence of the illumination light 3. The projection optical unit 31 has exactly eight mirrors for grazing incidence.

[0082] The mirrors M2-M8, i.e. seven of the eight GI mirrors of the projection optical unit 31, reflect the imaging light 3 in such a way that the reflection angles of the individual rays 29 at the respective mirrors M2-M8 are summed, i.e. resulting in an amplification of their deflection effect. The subsequent GI mirror M9 is a so-called counter mirror and reflects the imaging light 3 so that it results in a deflection effect that is counter to the deflection effect of the mirrors M2-M8, i.e. it has a subtractive effect on the deflection effect of the GI mirrors M2-M8. According to the rules of the mirror surrounding effect, which are explicitly stated in the context of the description of the projection optical unit in DE 102019219209 A1, the projection optical unit 31 has the following sequence of deflection effects on the mirrors M1-M11: RLLLLLLLR0L.

[0083] The projection optical unit 31 is approximately telecentric on the object side. If the imaging beam path is considered only with respect to the individual rays passing through the object field 4, the entrance pupil is arranged 4014.30 mm downstream of the object field 5 in the xz-plane and 5750.64 mm downstream of the object field 4 in the yz-plane.

[0084] The projection optical unit 31 has a pupil surface in the beam path between mirror M1 and mirror M2. An intermediate image surface is arranged in the region of reflection on mirror M5. A further pupil surface is arranged in the imaging light beam path between mirror M5 and mirror M6. A further intermediate image surface is arranged between mirror M6 and mirror M7. The number of intermediate image surfaces differs from the number of intermediate images in the meridian plane according to FIG. 3 and the number of intermediate images in the plane perpendicular thereto. Such projection optical units with a different number of intermediate images in mutually perpendicular planes are known in principle from WO 2016 / 166080 A1 and DE 102015226531 A1.

[0085] The optical design data of the projection optical unit 31 emerge from Tables 1 to 5 below and also correspond, in terms of basic structure, to Tables 1 to 5 relating to the embodiment according to FIG.

[0086] [Table 8]

[0087] [Table 9]

[0088] [Table 10] TIFF2024522609000024.tif229156 TIFF2024522609000025.tif229156 TIFF2024522609000026.tif228156

[0089] [Table 11] TIFF2024522609000028.tif229157 TIFF2024522609000029.tif229157 TIFF2024522609000030.tif76157

[0090]

Table 12

[0091]

Table 13

[0092]

Table 14

[0093] Mirrors M1, M4, M5, M6, M7 and M11 have negative values ​​for the radius, i.e. are in principle concave mirrors. Mirror M10 has a positive radius value, i.e. is in principle a convex mirror. Mirrors M2, M3, M8 and M9 have R values ​​with different signs in each case. x , R y It has a radius, i.e. is essentially saddle-shaped.

[0094] Further data for the projection optical unit 7 arises from Table 5 below.

[0095] [Table 15]

[0096] The projection optical unit 31 has an object / image offset a of 3468 mm. The working distance b, which for the projection optical unit 31 lies between the object plane 5 and the reflecting part of the mirror M5 which is closest to it, is 277 mm. The meridional transverse dimension c, which for the projection optical unit 31 lies between the separation surface 31a and the reflecting part of the mirror M11 which is furthest therefrom, is 4112 mm.

[0097] For the projection optical unit 31, the ratio a / c is 0.84. For the projection optical unit 31, the ratio b / c is 0.067.

[0098] Figure 4 shows a further embodiment of a projection optical unit or imaging optical unit 32 which can be used in the projection exposure apparatus 1 instead of the projection optical unit 7. With reference to Figures 1 to 3, components and functions which correspond to those already described above, in particular in relation to Figures 2 and 3, are designated by the same reference signs and will not be discussed in detail again.

[0099] The projection optical unit 32 has an image-side numerical aperture of 0.75.

[0100] The projection optical unit 32 according to Fig. 4 has a total of nine mirrors M1 to M9. Mirrors M1, M8 and M9 are embodied as mirrors for normal incidence (NI mirrors). Mirrors M2 to M7 are each embodied as mirrors for grazing incidence (GI mirrors). Thus, the projection optical unit 32 includes three NI mirrors and six GI mirrors.

[0101] The NI mirrors M2-M7 reflect the imaging light 3 in such a way that the reflection angles of the individual rays 29 at each mirror M2-M7 sum up, i.e. resulting in an amplification of their deflection effect. The projection optical unit 32 does not have a counter GI image.

[0102] The projection optical unit 32 is approximately telecentric on the object side. If the imaging beam path is considered only with respect to the individual rays passing through the object field 4, the entrance pupil is arranged 4161.14 mm downstream of the object field 5 in the xz-plane and −8870.82 mm upstream of the object field 4 in the yz-plane.

[0103] In the projection optical unit 32, a pupil plane is arranged in the imaging beam path between mirror M1 and mirror M2. A first intermediate image plane is arranged in the beam path between mirror M2 and mirror M3. A further pupil plane is arranged between mirror M3 and mirror M4. A further intermediate image plane is arranged in the area of ​​reflection on mirror M5. The number of intermediate image planes differs from the number of intermediate images in the meridian plane according to FIG. 4 and the number of intermediate images in the plane perpendicular thereto. Such projection optical units with different numbers of intermediate images in mutually perpendicular planes are known in principle from WO 2016 / 166080 A1 and DE 102015226531 A1.

[0104] Apart from the number of GI mirrors and the lack of a counter GI mirror arrangement, the projection optical unit 32 corresponds to the projection optical unit 31 in terms of basic structure.

[0105] The optical design data of the projection optical unit 32 according to FIG. 4 emerges from the following Tables 1 to 5, which correspond to the Tables 1 to 5 relating to the embodiment according to FIGS.

[0106] [Table 16]

[0107] [Table 17]

[0108] [Table 18] TIFF2024522609000047.tif229155 TIFF2024522609000048.tif229155 TIFF2024522609000049.tif236155 TIFF2024522609000050.tif236155

[0109] [Table 19] TIFF2024522609000052.tif229154 TIFF2024522609000053.tif114154

[0110] [Table 20] TIFF2024522609000055.tif229154 TIFF2024522609000056.tif236154 TIFF2024522609000057.tif229154 TIFF2024522609000058.tif229154

[0111] [Table 21] TIFF2024522609000060.tif229153 TIFF2024522609000061.tif229153 TIFF2024522609000062.tif152153

[0112] Further data for the projection optical unit 7 arises from Table 5 below.

[0113] [Table 22]

[0114] The projection optical unit 32 according to Fig. 4 has an object / image offset a of 3731 mm. The working distance b, which lies between the object plane 5 and the reflecting part of the mirror M5 closest to it in the case of the projection optical unit 32, is 275 mm. The meridional transverse dimension c, which lies between the separation surface 31a in the case of the projection optical unit 32 and the reflecting part of the mirror M9 which is furthest from said separation surface 31a in the case of the projection optical unit 32, is 4397 mm in the case of the projection optical unit 32.

[0115] For the projection optical unit 32, the ratio a / c is 0.85. For the projection optical unit 32, the ratio b / c is 0.063.

[0116] The ratio a / c is greater than 0.5 in each of the three above-mentioned projection optical units 7, 31 and 32.

[0117] The dimensional ratio b / c is greater than 0.05 in each of the projection optical units 7, 31 and 32.

[0118] The projection optical units 7, 31 and 32 each have an object / image offset a of at least 1500 mm.

[0119] The projection optical units 7, 31 and 32 each have a working distance b of at least 270 mm. The projection optical units 7, 31 and 32 each have a meridional transverse dimension of at most 4500 mm.

[0120] The important properties of the projection optical units 7, 31, 32 are again summarised below in a property table.

[0121] [Table 23]

[0122] To produce micro- or nanostructured components, the projection exposure apparatus 1 is used as follows: First, a reflective mask 10 or reticle and a substrate or wafer 11 are provided. Subsequently, structures on the reticle 10 are projected onto a photosensitive layer of the wafer 11 using the projection exposure apparatus 1. The micro- or nanostructures on the wafer 11, and thus the microstructured components, are then produced by developing the photosensitive layer.

Claims

1. An imaging optical unit (7; 31; 32), comprising: - a plurality of mirrors (M1 to M8; M1 to M11; M1 to M9) for imaging an object field (4) in an object plane (5) onto an image field (8) in an image plane (9); - having an image-side numerical aperture greater than 0.55; - a separation plane (31a) on which the center of the object field (5) is disposed and which is perpendicular to the meridional plane (yz) of the imaging optical unit (7; 31; 32); - and the center of the image field (8); - having an object / image offset a therebetween; - the object plane (5); - and an operating distance b between the object plane and the reflection portion of one of the mirrors (M4; M5) closest to the object plane; - the separation plane (31a); - and a meridional transverse dimension c between the separation plane (31a) and the reflection portion of one of the mirrors (M4; M11; M9) farthest from the separation plane (31a); - applying the following: - the ratio a / c is at least 0.5; - the ratio b / c is at least 0.05; - and the operating distance b is at least 270 mm. An imaging optical unit.

2. The imaging optical unit according to claim 1, characterized in that the object / image offset a is at least 1500 mm.

3. The imaging optical unit according to claim 1 or 2, characterized in that the operating distance b is at least 275 mm.

4. The imaging optical unit according to claim 1 or 2, characterized in that the meridional transverse dimension c is at most 4500 mm.

5. The imaging optical unit according to claim 1 or 2, characterized by an embodiment as an anamorphic optical unit.

6. The imaging optical unit according to claim 1 or 2, characterized by a wavefront aberration of 20 mλ or less.

7. The imaging optical unit according to claim 1 or 2, characterized in that the mirrors (M1 to M8; M1 to M11; M1 to M9) are at least eight in total.

8. The imaging optical unit according to claim 1 or 2, characterized by at least four GI mirrors.

9. The imaging optical unit according to claim 1 or 2, characterized by at least three NI mirrors.

10. An optical system, comprising: - the imaging optical unit according to claim 1 or 2; and - an illumination optical unit (6) for illuminating the object field (4) with illumination and imaging light (3).

11. ​ ​ ​ An illumination system comprising the optical system according to claim 10 and an EUV light source (2) for generating the illumination and imaging light (3).

12. A projection exposure apparatus (50) for projection lithography, comprising the illumination system according to claim 11.

13. A method for generating a structured component, comprising the following method steps, namely: - providing a reticle (10) and a wafer (11); - projecting a structure on the reticle (10) onto a photosensitive layer of the wafer (11) using the projection exposure apparatus according to claim 12; - generating a micro-structure and / or a nano-structure on the wafer (11). A method comprising the above steps.

14. A structured component produced according to the method of claim 13.

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