Imaging EUV optical unit for imaging an object field onto an image field

Abstract

The imaging EUV optical unit (24) serves to image the object field (5) onto the image field (11). The EUV optical unit (24) has a plurality of mirrors (M1 to M4) for guiding EUV imaging light (16) with a wavelength shorter than 30 nm along the imaging beam path from the object field (5) towards the image field (11). The EUV optical unit (24) has four NI mirrors (M1 to M4). The total transmittance of the NI mirrors (M1 to M4) is greater than 10%. When linearly polarized EUV imaging light (16) is used, the mirrors (M1 to M4) provide a total polarization rotation of 10° or less along the imaging beam path. This results in an imaging EUV optical unit with improved EUV throughput while meeting strict requirements for the quality of imaging.

Description

Technical Field

[0001] This application claims the priority of German Patent Application DE102022206112.8, the content of which is incorporated herein by reference.

[0002] The present invention relates to an imaging EUV optical unit for imaging an object field into an image field. Further, the present invention relates to an optical system comprising such an imaging optical unit, a projection exposure apparatus comprising such an optical system, a method for manufacturing micro or nano-structured components using such a projection exposure apparatus, and a micro or nano-structured component manufactured by said method.

Background Art

[0003] Imaging optical units of the type mentioned at the beginning are known from DE102018214437A1, US Patent No. 8,018,650 (B2), WO2018 / 043433A1, US Patent No. 6,353,470 (B1), and US Patent No. 5,291,340.

Summary of the Invention

[0004] The object of the present invention is to develop an imaging EUV optical unit of the type mentioned at the beginning so that the EUV throughput is improved while meeting strict requirements for the quality of imaging.

[0005] According to the present invention, this object 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 a small polarization rotation of an imaging EUV optical unit of 10° or less enables imaging of linearly polarized imaging light without causing a reduction in unnecessary contrast within the range of interference of diffractions of different orders guided in the imaging beam path required for imaging. The total polarization rotation can be less than 10°, can be less than 8°, can be less than 7°, can be less than 6°, can be less than 5°, and may also be less than 4.5°. Even smaller total polarization rotations are possible. The total polarization rotation is typically greater than 0.1°. The total polarization rotation represents the cumulative polarization rotation effect of all the mirrors within the imaging EUV optical unit.

[0007] The EUV optical unit may include three or four NI mirrors. Basically, even a smaller number of NI mirrors are possible.

[0008] Compared with the prior art that discloses a total transmittance of an EUV optical unit that is typically significantly less than 10%, a total transmittance of an imaging EUV optical unit greater than 10% corresponds to a very significant improvement. This is because any percentage obtained as the total transmittance in the case of a small absolute value of the total transmittance means a significant improvement in EUV throughput through the imaging EUV optical unit. This plays a decisive role particularly when the imaging EUV optical unit is used in the field of projection lithography for chip manufacturing.

[0009] The total transmittance of the NI mirrors, that is, the total transmittance of the imaging EUV optical unit, may be greater than 11%, may be greater than 12%, may be greater than 13%, may be greater than 14%, may be greater than 15%, may be greater than 16%, may be greater than 17%, may be greater than 18%, and may also be greater than 19%. The total transmittance is typically less than 30%.

[0010] The image-side numerical aperture of the imaging EUV optical unit may be less than 0.5, which facilitates the correction of imaging aberration and, due to the reflectivity, increases the small incident angle or small incident angle bandwidth available for the NI mirror. At least one of the mirrors of the imaging EUV optical unit can be designed as a freeform surface, which cannot be described using a rotational symmetry axis. A plurality or all of the mirrors may also be designed as such freeform surfaces.

[0011] The imaging EUV optical unit may have a series of mirrors along the imaging beam path, where, when an object field with an aspect ratio greater than 1 is used, especially in the plane in the long field-of-view direction, a condenser mirror is first used, then a diverging mirror, and then a condenser mirror is used again.

[0012] In the case of the imaging EUV optical unit, the object plane may extend parallel to the image plane. Alternatively, for reasons of optimizing the installation space in particular, it is possible to tilt the object plane with respect to the image plane.

[0013] At least one of the mirrors within the imaging EUV optical unit may have a saddle-shaped basic form. In addition, two, three, or even more of the mirrors within the imaging EUV optical unit may have a saddle-shaped basic form.

[0014] The chief ray angle between the chief ray of the imaging beam path within the imaging EUV optical unit and the perpendicular to the object plane where the object field is located may be in the range of 4.5° to 7°, for example, in the range of 5° to 6°.

[0015] Due to the relatively small number of NI mirrors, it has been found that the imaging EUV optical unit according to claim 2 advantageously has a high overall transmittance and, at the same time, is still able to meet the strict requirements regarding the quality of the imaging to be achieved.

[0016] Furthermore, it has been found that the high requirements regarding the imaging quality of the EUV optical unit can also be met according to claim 3 by using only NI mirrors for further correction of imaging aberrations, i.e., basically without using additional GI mirrors that can have a high EUV reflectivity.

[0017] The design of the imaging EUV optical unit according to claim 4, without an intermediate image between the object field and the image field, enables the provision of a particularly small angle-of-incidence bandwidth for the NI mirrors involved. This facilitates meeting the requirements for the high-reflection coating, particularly on the NI mirrors of the imaging EUV optical unit.

[0018] The small polarization rotation of the imaging EUV optical unit according to claim 4 enables the imaging of linearly polarized imaging light.

[0019] It has been found that the saddle-shaped surface design of at least one of the mirrors according to claim 5, i.e., the different signs of the curvature of the respective mirror reflection surfaces of the reflection surface cross-sections perpendicular to each other, is particularly suitable for the optical design of the imaging EUV optical unit.

[0020] The aspect ratio according to claim 6 enables guiding the imaging beam path with a small angle-of-incidence bandwidth even when the imaging field of view has a large aspect ratio, which may be greater than, for example, 3, greater than 5, greater than 8, or even greater than 10. The aspect ratio of the mirror reflection surface may be greater than 1.7, greater than 2, or even greater than 2.5. This aspect ratio of the mirror reflection surface is usually less than 5. This corresponding aspect ratio may be applied to one of the NI mirrors of the imaging EUV optical unit in particular.

[0021] The annular-field-shaped image field according to claim 7 can be corrected well. Alternatively, the image field may be designed as a rectangle or an arcuate non-annular-field shape.

[0022] Depending on the embodiment of the imaging EUV optical unit, the intersection region according to claim 8 may lead to the realization of a small incident angle on the NI mirror and / or the realization of a small incident angle bandwidth, which are each advantageous for the purpose of obtaining a high reflectivity.

[0023] The design according to claim 9 has been found to be particularly suitable.

[0024] The intersection region may also be present between a portion of the imaging beam path between the third mirror from the last and the second mirror from the last in the imaging beam path and a portion of the imaging beam path between the last mirror and the image field.

[0025] An entrance pupil in the imaging beam path upstream of the object field according to claim 10, i.e., outside the imaging beam path between the object field and the image field, enables the corresponding illumination optical component to be arranged within the region of this entrance pupil, and as a result, there is no need to arrange the illumination optical component near the pupil that images (image) onto the entrance pupil of the imaging EUV optical unit, which cannot be reached by other means. This saves light guiding component parts and thus also improves the EUV throughput.

[0026] At least one mirror having a passage aperture according to claim 11 enables the imaging EUV optical unit to be designed as an obscured system. The imaging EUV optical unit can be designed as a single-obscuration type, where exactly one of the mirrors has a passage aperture for passing the imaging beam path. Alternatively, such a passage aperture may also be provided in two mirrors, and in particular, in that case, a double-obscuration system may exist. The passage apertures of such mirrors enable a design with a small incident angle and / or a small incident angle bandwidth on each NI mirror. Alternatively, the imaging EUV optical unit may also be designed as a non-obscuration type.

[0027] The advantages of the optical system according to claim 12, the projection exposure apparatus according to claim 13, the manufacturing method according to claim 14, and the microstructured or nanostructured component according to claim 15 correspond to the advantages already described above with respect to the projection optical unit according to the invention. The EUV light source of the projection exposure apparatus can be embodied so as to produce a use wavelength of, for example, 30 nm or less, 25 nm or less, 20 nm or less, or 13.5 nm or less, less than 13.5 nm, less than 10 nm, less than 8 nm, less than 7 nm, 6.7 nm or 6.9 nm. Use wavelengths of less than 6.7 nm, in particular on the order of 6 nm, are also possible.

[0028] Specifically, using this projection exposure apparatus, semiconductor components, for example memory chips, can be manufactured.

[0029] Hereinafter, at least one exemplary embodiment of the invention will be described based on the drawings.

Brief Description of the Drawings

[0030]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

DETAILED DESCRIPTION OF THE INVENTION

[0031] In the following description, first, the basic components of the microlithographic projection exposure apparatus 1 will be described by way of example with reference to FIG. 1. The description of the basic structure of the projection exposure apparatus 1 and its components should not be construed as limiting here.

[0032] One embodiment of the illumination system 2 of the projection exposure apparatus 1 has, in addition to a light source or radiation source 3, an illumination optical unit 4 for illuminating an object field 5 in the object plane 6. In an alternative embodiment, the light source 3 can also be provided as a separate module from the rest of the illumination system. In this case, the illumination system does not include the light source 3.

[0033] The reticle 7 disposed in the object field 5 is exposed. The reticle 7 is held by a reticle holder 8. The reticle holder 8 is displaceable by a reticle displacement drive mechanism 9, particularly in the scanning direction.

[0034] For the purpose of explanation, a Cartesian xyz coordinate system is shown in FIG. 1. The x direction extends perpendicular to the plane of the drawing and into the depth of the drawing. The y direction extends horizontally and the z direction extends vertically. The scanning direction extends in the y direction in FIG. 1. The z direction extends perpendicular to the object plane 6.

[0035] The projection exposure apparatus 1 includes a projection optical unit 10. The projection optical unit 10 functions as an imaging optical unit for imaging (image) the object field 5 onto the image field 11 of the image plane 12. The image plane 12 extends parallel to the object plane 6. As an alternative, an angle different from 0° between the object plane 6 and the image plane 12 is also possible.

[0036] The structure on the reticle 7 is imaged onto the photosensitive layer of the wafer 13 disposed in the region of the image field 11 of the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 is displaceable by a wafer displacement drive mechanism 15, particularly in the y direction. First, the displacement of the reticle 7 by the reticle displacement drive mechanism 9 and second, the displacement of the wafer 13 by the wafer displacement drive mechanism 15 can be carried out to be synchronized with each other.

[0037] The radiation source 3 is an EUV (extreme ultraviolet) radiation source. The radiation source 3 emits particularly EUV radiation 16, which is hereinafter also referred to as used radiation, illumination radiation, illumination light, or imaging light. Specifically, the used radiation has a wavelength in the range of 5 nm to 30 nm. The radiation source 3 can be a plasma source, for example an LPP (laser-produced plasma) source or a GDPP (gas-discharge-produced plasma) source. It can also be a radiation source utilizing a synchrotron. The radiation source 3 can be a free electron laser (FEL).

[0038] The illumination radiation 16 emitted from the radiation source 3 is focused by the condenser 17. The condenser 17 may be a condenser having one or more reflecting surfaces of an ellipsoid and / or a hyperboloid. The illumination radiation 16 can be incident on at least one reflecting surface of the condenser 17 at a grazing incidence (GI), i.e., an incident angle greater than 45°, or at a normal incidence (NI), i.e., an incident angle less than 45°. The condenser 17 may be structured and / or coated, on the one hand, to optimize its reflectivity for the radiation used and, on the other hand, to suppress stray light.

[0039] The illumination radiation 16 propagates downstream of the condenser 17 through the intermediate focus of the intermediate focal plane 18. The intermediate focal plane 18 can correspond to the boundary between the radiation source module having the radiation source 3 and the condenser 17 and the illumination optical unit 4.

[0040] The illumination optical unit 4 includes a deflection mirror 19 and a first facet mirror 20 disposed downstream thereof in the beam path. The deflection mirror 19 may be a planar deflection mirror or, alternatively, a mirror having a beam influence effect that exceeds a pure deflection effect. Alternatively or additionally, the deflection mirror 19 may be embodied in the form of a spectral filter that separates the used light wavelength of the illumination radiation 16 from light that is irrelevant at wavelengths deviating therefrom. When the first facet mirror 20 is disposed on the surface of the illumination optical unit 4 that is optically conjugate with the object surface 6, which is the field surface, it is also referred to as a field facet mirror. The first facet mirror 20 includes a number of individual first facets 21, which are also referred to hereinafter as field facets. FIG. 1 illustrates only a part of the facets 21 as an example.

[0041] The first facet 21 may be embodied as a macroscopic facet, in particular as a rectangular facet, or as a facet having an arcuate edge contour or an edge contour that is part of a circle. The first facet 21 may be embodied as a planar facet, or alternatively as a facet having a convex or concave curvature.

[0042] As is known, for example, from DE102008009600A1, the first facet 21 itself may also, in each case, be composed of a number of individual mirrors, in particular a number of micromirrors. The first facet mirror 20 may in particular be formed as a microelectromechanical system (MEMS system). For details, reference is made to DE102008009600A1.

[0043] The illumination radiation 16 travels horizontally, i.e., in the y direction, between the condenser 17 and the deflection mirror 19.

[0044] In the beam path of the illumination optical unit 4, a second facet mirror 22 is arranged downstream of the first facet mirror 20. If the second facet mirror 22 is arranged in the pupil plane of the illumination optical unit 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 may also be arranged at a distance from the pupil plane of the illumination optical unit 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also referred to as a specular reflector. Specular reflectors are known from US Patent Application Publication No. 2006 / 0132747, EP1614008B1, and US Patent No. 6,573,978.

[0045] The second facet mirror 22 comprises a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

[0046] The second facet 23 may likewise be a macroscopic facet, which may have, for example, circular, rectangular, or hexagonal boundaries, or alternatively may be a facet composed of micromirrors. In this regard, DE102008009600A1 is likewise referred to.

[0047] The second facet 23 may have a planar reflecting surface, or alternatively, a convex or concave curved reflecting surface.

[0048] As a result, the illumination optical unit 4 forms a dual-facet system. This basic principle is also referred to as a fly-eye condenser (fly-eye integrator).

[0049] It may be advantageous not to arrange the second facet mirror 22 exactly in a plane optically conjugate to the pupil plane of the projection optical unit 10. Specifically, the pupil facet mirror 22 may be arranged to be inclined with respect to the pupil plane of the projection optical unit 10, as described, for example, in DE102017220586A1.

[0050] Using the second facet mirror 22, the individual first facets 21 are imaged onto the object field 5. The second facet mirror 22 is the last beam-forming mirror or, in the beam path upstream of the object field 5, the actual last mirror for the illumination radiation 16.

[0051] In a further embodiment (not shown) of the illumination optical unit 4, a transmission optical unit that particularly contributes to imaging the first facet 21 onto the object field 5 may be arranged in the beam path between the second facet mirror 22 and the object field 5. The transmission optical unit may comprise exactly one mirror or, alternatively, two or more mirrors, which are arranged in a row within the beam path of the illumination optical unit 4. The transmission optical unit may particularly comprise one or two normal-incidence mirrors (NI mirrors) and / or one or two grazing-incidence mirrors (GI mirrors).

[0052] In the embodiment shown in FIG. 1, the illumination optical unit 4 has exactly three mirrors downstream of the condenser 17, specifically, the deflection mirror 19, the field facet mirror 20, and the pupil facet mirror 22.

[0053] The deflection mirror 19 can also be omitted in a further embodiment of the illumination optical unit 4, in which case the illumination optical unit 4 can have exactly two mirrors downstream of the condenser 17, specifically the first facet mirror 20 and the second facet mirror 22.

[0054] The imaging of the first facet 21 onto the object plane 6 using the second facet 23, or using the second facet 23 and the transmission optical unit, is basically only an approximate imaging.

[0055] The projection optical unit 10 includes a plurality of mirrors Mi, which are sequentially numbered according to their arrangement in the beam path of the projection exposure apparatus 1.

[0056] In the example shown in FIG. 1, the projection optical unit 10 includes six mirrors M1 to M6. Alternative examples with 4, 8, 10, 12, or any other number of mirrors Mi are equally possible. The projection optical unit 10 is an optical unit with double obscuration. The second last mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 16.

[0057] The imaging light 16 guided from the last mirror M6 towards the image field 11 passes through the passage opening of the mirror M5. The imaging light 16 reflected from the third last mirror M4 towards the second last mirror M5 passes through the passage opening of the mirror M6. Around their respective passage openings, the mirrors M5 and M6 are used reflectively to guide the imaging light 16.

[0058] The projection optical unit 10 has an image-side numerical aperture greater than 0.25, and may be greater than 0.3, for example, 0.33.

[0059] The number of openings on the image side is typically less than 0.9, less than 0.75, less than 0.6, and may be less than 0.5. In principle, the number of openings on the image side may also be larger than this.

[0060] The reflecting surface of the mirror Mi may be embodied as a free-form surface without a rotational symmetry axis. Alternatively, the reflecting surface of the mirror Mi may be designed as an aspherical surface having exactly one rotational symmetry axis of the reflecting surface shape. Similar to the mirror of the illumination optical unit 4, the mirror Mi may have a high-reflection coating for the illumination radiation 16. These coatings may be designed in particular as multilayer coatings having alternating layers of molybdenum and silicon.

[0061] The projection optical unit 10 has an object-image offset in the y direction between the y coordinate of the center of the object field 5 and the y coordinate of the center of the image field 11. This object-image offset in the y direction may be approximately the same magnitude as the z-direction distance between the object plane 6 and the image plane 12.

[0062] Specifically, the projection optical unit 10 can have an anamorphic embodiment. Specifically, it has imaging scales β x , β y that are different in the x and y directions. The two imaging scales β x , β y of the projection optical unit 10 are preferably at (β x , β y ) = (+ / -0.25, / +-0.125). A positive imaging scale β means imaging without image inversion. A negative sign of the imaging scale β means imaging with image inversion.

[0063] The projection optical unit 10 has, for example, a size reduction in a ratio of 4:1 in a direction perpendicular to the x direction, i.e., the scanning direction.

[0064] In the case of an anamorphic embodiment, the projection optical unit 10 has a size reduction of 8:1 in the y direction, i.e., the scanning direction.

[0065] Other imaging scales are similarly possible. Imaging scales having the same sign and the same absolute value in the x and y directions are also possible, having, for example, an absolute value of 0.125 or 0.25.

[0066] 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 may be the same or may differ depending on the embodiment of the projection optical unit 10. Examples of projection optical units with different numbers of such intermediate images in the x and y directions are known from US Patent Application Publication No. 2018 / 0074303.

[0067] To form an illumination channel for illuminating the object field 5 in each case, one of the pupil facets 23 in each case is assigned to exactly one of the field facets 21. Specifically, this can produce illumination according to Koehler's principle. The far field is decomposed into a number of object fields 5 using the field facets 21. The field facets 21 generate a plurality of intermediate focal images on the respective assigned pupil facets 23.

[0068] By the assigned pupil facet 23, the field facets 21 are imaged onto the reticle 7 in each case so as to overlap with each other for the purpose of illuminating the object field 5. The illumination of the object field 5 is, in particular, as uniform as possible. Preferably, it has a uniformity error of less than 2%. The uniformity of the field 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 illumination channels, in particular a subset of the pupil facets that conduct light. This intensity distribution is also referred to as the illumination setting or illumination pupil filling.

[0070] Similarly favorable pupil uniformity in the regions of the plurality of sections of the illumination pupil of the illumination optical unit 4, illuminated as defined, can be achieved by redistribution of the illumination channels.

[0071] Further aspects and details of the illumination of the object field 5, in particular of the entrance pupil of the projection optical unit 10, will be explained below.

[0072] The projection optical unit 10 may in particular have a concentric entrance pupil. The latter may be achievable. It may also be non-achievable.

[0073] The entrance pupil of the projection optical unit 10 usually cannot be accurately illuminated using the pupil facet mirror 22. In the case of imaging the projection optical unit 10 that images the center of the pupil facet mirror 22 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 required aperture rays in pairs is minimized. This area corresponds to the entrance pupil or an area in the real space conjugate thereto. Specifically, this area has a finite curvature.

[0074] The projection optical unit 10 may have entrance pupils with different postures in the tangential beam path and the sagittal beam path. In this case, imaging elements, in particular the optical component parts of the transmission optical unit, must be provided between the second facet mirror 22 and the reticle 7. This optical element can be used to take into account the different positions of the entrance pupil in the tangential direction and the entrance pupil in the sagittal direction.

[0075] In the arrangement of the components of the illumination optical unit 4 shown in FIG. 1, the pupil facet mirror 22 is arranged in an area conjugate to the entrance pupil of the projection optical unit 10. The field facet mirror 20 is arranged so as to be inclined with respect to the object plane 6. The first facet mirror 20 is arranged so as to be inclined with respect to the arrangement plane defined by the deflection mirror 19.

[0076] The first facet mirror 20 is arranged so as to be inclined with respect to the arrangement plane defined by the second facet mirror 22.

[0077] Figure 2 shows a further embodiment of the projection optical unit or imaging optical unit 24, which can be used in the projection exposure apparatus 1 in place of the projection optical unit 10 of the embodiment according to FIG. 1. Components and functions corresponding to those already described above with respect to FIG. 1 have the same reference numerals and detailed description thereof is omitted.

[0078] Figure 2 shows the beam paths of three individual light rays 25 emitted from three object field points spaced apart from each other in the y direction of FIG. 2 in each case. Depicted are the chief ray 26, i.e., the individual light ray 25 passing through the center of the pupil of the pupil plane of the projection optical unit 24, and the upper and lower coma rays of these three object field points in each case. Proceeding from the object field 5, the chief ray 26 includes an angle CRA of 5.22° with respect to the perpendicular to the object plane 6. The design of the projection optical unit 24 for the reflective reticle 7 exists due to this chief ray angle CRA. This ensures that the beam path of the illumination light 16 incident on the reticle 7 does not interfere with the beam path of the illumination light or imaging light 16 reflected by the reticle 7.

[0079] The projection optical unit 24 has an image-side numerical aperture of 0.33.

[0080] The projection optical unit 24 according to FIG. 2 has a total of four mirrors, which are sequentially numbered M1 to M4 in the order of the beam paths of the individual light rays 25 proceeding from the object field 4.

[0081] Figure 2 shows the calculated portions of the reflecting surfaces of the mirrors M1 to M4. What is added with an overhang to the actually used area of the reflecting surface exists in the actual mirrors M1 to M4. These used reflecting surfaces are carried in a manner known per se by mirror bodies not shown in FIG. 2.

[0082] In the projection optical unit 24 according to FIG. 2, all the mirrors M1 to M4 are embodied as right-angled or normal-incidence mirrors, i.e., mirrors on which the imaging light 16 is incident at an incident angle smaller than 45°. These normal-incidence mirrors are also referred to as NI (normal incidence) mirrors.

[0083] Mirrors M1 to M4 are provided with a coating that optimizes the reflectivity of mirrors M1 to M4 with respect to imaging light 16. This can be a ruthenium coating, a molybdenum coating, or a molybdenum coating having a top layer of ruthenium. These high-reflection layers can be embodied as multilayers, and consecutive layers can be manufactured from different materials. Alternating material layers can also be used. A typical multilayer can have 50 double layers, each made from a layer of molybdenum and a layer of silicon.

[0084] To calculate the total reflectivity of projection optical unit 24, the system transmittance is calculated as follows. Based on the angle of incidence of the guide ray, i.e., the chief ray of the central object field point, the mirror reflectivity is determined at each mirror surface, and they are multiplied together to form the system transmittance.

[0085] Details regarding the calculation of reflectivity are described in WO2015 / 014753A1. Further information regarding the reflectivity of NI mirrors (normal incidence mirrors) can be found in DE10155711A.

[0086] The system or total transmittance of projection optical unit 24, i.e., the total number of mirrors M1 to M4, is 17.55%. Thus, on average, each individual mirror of the four mirrors has a reflectivity of about 64.7%.

[0087] The polarization rotation of linearly polarized imaging light 16 in the imaging beam path of projection optical unit 24 between object field 5 and image field 11 is approximately 3.6°.

[0088] None of mirrors M1 to M4 have a passage aperture, and the mirrors are used in a reflection mode within a continuous region without a gap. Thus, mirrors M1 to M4 have a reflective surface that is used without an aperture.

[0089] In projection optical unit 24, image field 11 is the first field in the imaging beam path downstream of object field 5. Thus, projection optical unit 24 does not have an intermediate image plane.

[0090] The z-direction distance (installation length) between the object field and the image field 8 is approximately 1750 mm. The y-direction distance (object-image offset) between the central field point of the object field 5 and the central field point of the image field 11 is approximately 1380 mm. In the xz plane, the entrance pupil of the projection optical unit 24 is located approximately 4100 mm downstream from the object field 5 in the imaging beam path. In the yz plane, the entrance pupil is more than 10 m upstream of the object field 5 in the imaging beam path. Therefore, the projection optical unit 24 is approximately telecentric on the object side.

[0091] The projection optical unit 24 is telecentric on the image side.

[0092] The minimum distance between the wafer 13 and the mirror M3 closest to the wafer is 75 mm, and this distance is also referred to as the working distance.

[0093] The average wavefront aberration RMS of the projection optical unit 24 is less than 35 mλ when the wavelength of the imaging light 3 is 13.5 nm.

[0094] The following Tables 1 and 2 summarize again the basic data of the projection optical unit 24.

Table 1

[0095]

Table 2

[0096] The spreads specified in Table 2 are related to the utilized reflecting surfaces of the mirrors M1 to M4 in each case.

[0097] The largest incident angle of the imaging light 16 on the mirrors M1 to M4 exists on the mirror M3, and is also less than 25° there.

[0098] The smallest incident angle exists at mirror M1, where it is greater than 2.5°. The largest incident angle bandwidth, i.e., the difference between the maximum and minimum incident angles of imaging light 16, exists at the last mirror M4, where it is less than 15°. The smallest incident angle bandwidth exists at mirror M2, where it is 3°.

[0099] None of the mirrors M1 to M4 have a diameter greater than 1000 mm. Regarding the spread in the x direction, mirror M2 is the largest mirror of the projection optical unit 24. Specifically, mirror M2 has a greater spread in the x direction than mirror M4.

[0100] Mirror M2 has a reflective surface with an x / y aspect ratio of the larger x-direction surface spread to the smaller y-direction surface spread greater than 1.5. This aspect ratio is 2.13 for mirror M2 of the projection optical unit 24, i.e., it is greater than 2.

[0101] Image field 11 is in an annular field shape and has an annular field radius of 260 mm in the projection optical unit 24. The spread of image field 11 in the x direction is 26 mm. The spread of image field 11 in the y direction is 2.5 mm.

[0102] Mirrors M1 to M4 are embodied as free-form surfaces that cannot be described by a rotationally symmetric function. Other embodiments of the projection optical unit 24 are possible where at least one of mirrors M1 to M4 is embodied as a rotationally symmetric aspherical surface. It is also possible for all of mirrors M1 to M4 to be embodied as such aspherical surfaces.

[0103] The free-form surface can be described by the following free-form surface equation (Equation 1).

Number

[0104] The following corresponds to the parameters of this Equation (1).

[0105] Z is the sagittal height of the freeform surface at points x, y, where x 2 + y 2 = r 2 . Here, r is the distance from the reference axis (x = 0; y = 0) of the freeform surface equation.

[0106] In the freeform surface equation (1), C1, C2, C3... represent the coefficients of the freeform surface series expansion as powers of x and y.

[0107] In the case of the conical base region, c x , c y are constants corresponding to the vertex curvatures of the corresponding aspheres. Thus, c x = 1 / RDX and c y = 1 / RDY are applicable. k x and k y are also called CCX and CCY, respectively, corresponding to the conic constants of the corresponding aspheres. Thus, equation (1) describes a bi-conical freeform surface.

[0108] An alternative possible freeform surface can be generated from a rotationally symmetric reference surface. Such a freeform surface for the reflecting surface of a mirror in the projection optical unit of a microlithography projection exposure apparatus is known from U.S. Patent Application Publication No. 20070058269.

[0109] Alternatively, the freeform surface can also be described using a two-dimensional spline surface. This example is a Bézier curve or a non-uniform rational basis spline (NURBS). As an example, the two-dimensional spline surface can be described by a grid of points in the xy plane and associated z values, or by these points and associated gradients. Depending on each type of spline surface, the completed surface is obtained by interpolation between grid points using, for example, polynomials or functions having specific properties regarding its continuity and differentiability. An example of this is an analytical function.

[0110] The aperture stop AS that defines the pupil is arranged in the region of or on the mirror M3 within the projection optical unit 24, which is shown in FIG. 2. As an example, options for realizing such an aperture stop are disclosed in WO2016 / 188934A1. Instead of having a single aperture stop AS that defines the pupil, the effect can also be achieved by a plurality of partial stops that define the pupil, which are arranged at different locations within the projection optical unit 24.

[0111] The arrangement plane of the aperture stop AS coincides with the pupil plane of the projection optical unit 24.

[0112] The optical design data of the reflecting surfaces of the mirrors M1 to M4 of the projection optical unit 24 can be collected from still other tables below.

[0113] Table 3 specifies the surface origin of each mirror surface and the coordinates of an area of the object field 5 with respect to the xyz coordinate system of the image field 11.

[0114] The first column specifies the distance of each mirror or the object field 5 from the coordinate origin at the center of the image field 11 in the z direction (first column) and the y direction (second column).

[0115] The third column of Table 3 further specifies the inclination values of the respective surfaces of the mirrors M1 to M4 or the object field 5 with respect to the xy plane of the image field 11. In the embodiment according to FIG. 2, neither the object field 5 nor the image field 11 is inclined with respect to the x axis and they extend parallel to each other.

[0116] Table 4 tabulates, for each of the mirrors M4 to M1, the parameters RDX, RDY, CCX, CCY and the values of the coefficients C1, C2, C3... of the series expansion of the freeform surface according to the above formula (1), arranged according to the powers of x and y.

[0117] Mirrors with different signs for the values RDX and RDY have a saddle point type or a minimax basic shape.

Table 3

[0118]

Table 4

[0119]

Table 5

[0120]

Table 6

[0121]

Table 7

[0122] FIG. 3 shows a further embodiment of the projection optical unit or the imaging optical unit 27, which can be used in the projection exposure apparatus 1 instead of the projection optical unit 10 of the embodiment according to FIG. 1. With respect to FIGS. 1 and 2, in particular with respect to FIG. 2, the components and functions corresponding to those already described above are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0123] The annular field radius of the image field 11 is 80 mm in the projection optical unit 27. In the projection optical unit 27, the image field dimensions in the x direction and the y direction are the same as those in the case of the projection optical unit 24.

[0124] The core parameters of the optical design are tabulated again below in relation to the projection optical unit 27. [Table 8] Table 1 of FIG. 3

[0125] [Table 9] Table 2 of FIG. 3

[0126] The largest incident angle of the imaging light 16 on the mirrors M1 to M4 is at the mirror M3 and is 22.9°. Thus, an incident angle of less than 25° exists for all individual light rays on all the mirrors M1 to M4 of the projection optical unit 27.

[0127] The minimum incident angle exists at mirror M1 and is 3.9°. The incident angle bandwidth between the minimum incident angle and the maximum incident angle is less than 10° for all mirrors M1 to M4, and is 6° or less for each of mirrors M1 to M3. The smallest incident angle bandwidth, i.e., the difference between the maximum incident angle and the minimum incident angle, exists at mirror M2 and is less than 2.5° there.

[0128] None of mirrors M1 to M4 have a diameter greater than 760 mm. Regarding the spread in the x direction, mirror M2 is the largest mirror. Specifically, mirror M2 has a greater spread in the x direction than the last mirror M4 of the projection optical unit 27.

[0129] The average wavefront aberration RMS is less than 20 mλ in the projection optical unit 27.

[0130] The image-side numerical aperture of the projection optical unit 27 is 0.25.

[0131] The maximum x / y aspect ratio of the surface spread is at mirror M2 in the projection optical unit 27 and is 2.14 there.

[0132] The total transmittance is 17.59% in the projection optical unit 27.

[0133] The polarization rotation of the linearly polarized imaging light 16 in the imaging beam path of the projection optical unit 27 between the object field 5 and the image field 11 is approximately 2.8°.

[0134] The optical design data of the projection optical unit 27 according to FIG. 3 are summarized in the following table in the same format as those already described above in relation to the embodiment according to FIG. 2.

Table 10

[0135]

Table 11

[0136]

Table 12

[0137]

Table 13

[0138]

Table 14

[0139] Figure 4 shows a further embodiment of the projection optical unit or imaging optical unit 28, which can be used in the projection exposure apparatus 1 in place of the projection optical unit 10 of the embodiment according to FIG. 1. With respect to FIGS. 1 to 3, in particular 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 description thereof is omitted.

[0140] The image field 11 of the projection optical unit 28 is rectangular, and the extent of the image field 11 in the x direction is 26 mm. The extent of the image field 11 in the y direction is 2.5 mm.

[0141] The aperture stop AS can be arranged in the region of the entrance pupil located between the mirror M3 and the mirror M4 in the beam path of the imaging light 16.

[0142] The following Tables 1 and 2 summarize again the basic data of the projection optical unit 28.

Table 15

[0143]

Table 16

[0144] Each of the mirrors M1 to M4 has a very small incident angle bandwidth of less than 12° for all individual light rays of the imaging light 16. A very small incident angle bandwidth of less than 2°, and even less than 1°, exists for the mirror M2 of the projection optical unit 28. The absolute incident angles on the mirrors M1 to M4 are also quite small in each case, specifically less than 20° for all individual light rays. For the mirrors M1 and M4, these absolute incident angles are less than 10°, and even less than 8°, for all individual light rays.

[0145] None of the mirrors M1 to M4 of the projection optical unit 28 has a diameter greater than 750 mm.

[0146] The maximum x / y aspect ratio of the surface spread is at the mirror M1 in the projection optical unit 28, where it is 1.68.

[0147] The image-side numerical aperture of the projection optical unit 28 is 0.28.

[0148] The projection optical unit 28 has a total transmittance of 19.21%.

[0149] The polarization rotation of the linearly polarized imaging light 16 in the imaging beam path of the projection optical unit 28 between the object field 5 and the image field 11 is approximately 0°.

[0150] The entrance pupil of the projection optical unit 28 is upstream of the object field 5 in the imaging beam path in both the xz plane and the yz plane. Specifically, it is approximately 1750 mm upstream of the object field 5 in the imaging beam path. Specifically, the pupil facet mirror of the illumination optical unit 4 may be disposed there.

[0151] The optical design data of the projection optical unit 28 according to FIG. 4 are summarized in the following table in the same format as those already described above in connection with the embodiment according to FIG. 2.

Table 17

[0152]

Table 18

[0153]

Table 19

[0154]

Table 20

[0155]

Table 21

[0156] FIG. 5 shows a further embodiment of the projection optical unit or imaging optical unit 29, which can be used in the projection exposure apparatus 1 instead of the projection optical unit 10 of the embodiment according to FIG. 1. With respect to FIGS. 1 to 4, in particular with respect to FIGS. 2 to 4, the components and functions corresponding to those already described above are denoted by the same reference numerals and detailed description thereof is omitted.

[0157] The basic design of the projection optical unit 29 is similar to that of the embodiment of FIG. 2 of DE102018214437A1, for example.

[0158] The first two mirrors M1 and M2 are used in a fully reflective manner, and the two subsequent mirrors M3 and M4 each have passage openings 30, 31 for passing the imaging light 16 in the imaging beam path of the projection optical unit 29.

[0159] For the passage opening 30, 25.3% of the total reflective surface of the mirror M3 is obscured. For the passage opening 31, 25.6% of the total reflective surface of the mirror M4 is obscured.

[0160] The projection optical unit 29 has an image-side numerical aperture of 0.33.

[0161] The image field 11 of the projection optical unit 29 is rectangular. The image field 11 has an extent in the x direction of 26 mm and an extent in the y direction of 2.5 mm.

[0162] The pupil plane is present in the imaging beam path between the mirrors M3 and M4. As shown in FIG. 5, the aperture stop AS may be arranged there.

[0163] The total transmittance is 17.28% in the projection optical unit 29.

[0164] The polarization rotation of the linearly polarized imaging light 16 in the imaging beam path of the projection optical unit 29 between the object field 5 and the image field 11 is approximately 0°.

[0165] The object-image offset is significantly smaller in the projection optical unit 29 than in the projection optical units 27 and 28, and is approximately 200 mm in the projection optical unit 29.

[0166] The core parameters of the optical design are summarized again in tabular form below in relation to the projection optical unit 29 in this case.

Table 22

[0167]

Table 23

[0168] A very small angle of incidence exists for each of the mirrors M3 and M4 of the projection optical unit 29, and for each individual ray, these are less than 10°. The largest angle of incidence is less than 5° and even less than 4° for the mirror M4.

[0169] The maximum x / y aspect ratio of the reflecting surface spread is at the mirror M1 in the projection optical unit 29, where it is 1.77.

[0170] None of the mirrors M1 to M4 have a diameter larger than 1100 mm.

[0171] The optical design data of the projection optical unit 29 according to FIG. 5 is summarized in the following table in the same format as that already described above in relation to the embodiment according to FIG. 2. [Table 24] Table 3 of FIG. 5

[0172] [Table 25] JPEG2025519867000048.jpg239152

[0173] [Table 26] JPEG2025519867000050.jpg239152

[0174] [Table 27] JPEG2025519867000052.jpg239152

[0175] [Table 28] JPEG2025519867000054.jpg239152 Table 4 of FIG. 5

[0176] FIG. 6 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. 1. With respect to FIGS. 1 to 5, in particular with respect to FIGS. 2 to 5, the components and functions corresponding to those already described above are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0177] In contrast to the projection optical unit 29 according to FIG. 5, in the projection optical unit 32 according to FIG. 6, the object plane 6 is not parallel to the image plane 12, but is inclined with respect thereto. In the projection optical unit 32, the angle between the object plane 6 and the image plane 12 is 8.3°. Therefore, this angle is less than 10°.

[0178] The core parameters of the optical design are summarized again in a table below in relation to the projection optical unit 32 in this case. [Table 29] Table 1 of FIG. 6

[0179] [Table 30] Table 2 of FIG. 6

[0180] The maximum x / y aspect ratio of the reflection surface spread is at the mirror M1 in the projection optical unit 32, where it is 1.71.

[0181] The total transmittance of the projection optical unit 32 is 17.37%.

[0182] The polarization rotation of the linearly polarized imaging light 16 in the imaging beam path of the projection optical unit 32 between the object field 5 and the image field 11 is approximately 1.4°.

[0183] Due to the aperture 30, 24.4% of the total reflecting surface of the mirror M3 is obscured. Due to the aperture 31, 26.0% of the total reflecting surface of the mirror M4 is obscured. The optical design data of the projection optical unit 32 according to FIG. 6 is summarized in the following table in the same format as that already described above in connection with the embodiment according to FIG. 2.

[0184]

Table 31

[0185]

Table 32

[0186]

Table 33

[0187]

Table 34

[0188]

Table 35

[0189] FIG. 7 shows a further embodiment of the projection optical unit or imaging optical unit 33, which can be used in the projection exposure apparatus 1 instead of the projection optical unit 10 of the embodiment according to FIG. 1. With respect to FIGS. 1 to 6, in particular with respect to FIGS. 2 to 6, the components and functions corresponding to those already described above are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0190] The numerical aperture on the image side of the projection optical unit 33 is 0.33.

[0191] The average wavefront aberration RMS is 47.2 mλ in the projection optical unit 33.

[0192] The x-direction position of the entrance pupil is more than 5 m downstream of the object field 5 in the imaging beam path. The y-direction position of the entrance pupil of the projection optical unit 33 is more than 8 m upstream of the object field 5 in the imaging beam path. Therefore, the projection optical unit 33 also has object-side telecentricity with a good approximation.

[0193] The total transmittance is 15.6% in the projection optical unit 33.

[0194] The polarization rotation of the linearly polarized imaging light 16 in the imaging beam path of the projection optical unit 33 between the object field 5 and the image field 11 is approximately 0.5°.

[0195] All the projection optical units described above are designed to have a very small polarization rotation effect on the imaging light 16 propagating linearly along the imaging beam path. The linearly polarized imaging light 16 propagating between the object field 5 and the image field 11 along the imaging beam path undergoes a polarization rotation of less than 10°, less than 7°, and may also be less than 5°. This polarization rotation is very small in the projection optical units 28 and 29, and may particularly be less than 1°. Basically, the polarization rotation is greater than 0°.

[0196] The projection optical unit 33 has a chief ray angle CRA of 6.0°.

[0197] There is an inclination angle of 8.6° between the object plane 6 and the image plane 12 of the projection optical unit 33.

[0198] The object-image offset is 415 mm in the projection optical unit 33.

[0199] The installation space requirement in the x / y direction is 1450 mm in the projection optical unit 33.

[0200] The working distance between the mirror closest to the wafer and the image field 11 is 50 mm in the projection optical unit 33.

[0201] In the projection optical unit 33, the imaging beam path portion between the object field 5 and the mirror M1 intersects with the imaging beam path portion between the mirrors M2 and M3 within the intersection region 34.

[0202] The mirrors M1 to M4 of the projection optical unit 33 also have freeform reflecting surfaces. These freeform surfaces of the mirrors M1 to M4 of the projection optical unit 33 can be described by the surface type described in the technical article "Characterizing the shape of freeform optics" by G.W. Forbes, Optics Express, 2012, vol. 20, no. 3, pages 2483 to 2499. The freeform surface having such a surface description is also called the Forbes freeform surface.

[0203] The formula for the Forbes freeform surface is as follows.

Equation

[0204] The following corresponds to the parameters of this formula (2). z is the sag of the freeform surface at the point h, θ, where h is the radial coordinate of this point and θ is the azimuthal coordinate: u = h / NH is the normalized radial coordinate; ρ is the curvature, i.e., the reciprocal of the radius of curvature RD; κ is the conic constant, i.e., corresponding to the value CC in the above table; Q m n is the orthogonal polynomial with respect to the unit circle described in the aforementioned Forbes feature article.

[0205] The optical design data of the projection optical unit 33 can be collected from Tables 1 and 2 below. The coefficients in Table 2 below are the coefficients of the above formula (2)

Number

[0206]

Number

[0207] The optical design data of the projection optical unit 33 according to FIG. 7 is summarized in the following table in the same format as that already described above in relation to the embodiment according to FIG. 2.

Table 36

[0208]

Table 37

[0209]

Table 38

[0210]

Table 39

[0211]

Table 40

[0212] FIG. 8 shows a further embodiment of the projection optical unit or imaging optical unit 35, which can be used in the projection exposure apparatus 1 instead of the projection optical unit 10 of the embodiment according to FIG. 1. For FIGS. 1 to 7, particularly for FIGS. 2 to 7, the components and functions corresponding to those already described above are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0213] The numerical aperture on the image side of the projection optical unit 35 is 0.26.

[0214] The average wavefront aberration RMS is 71.8 mλ in the projection optical unit 35.

[0215] The x-direction position of the entrance pupil of the projection optical unit 35 is more than 1100 mm downstream of the object field 5 in the imaging beam path. The y-direction position of the entrance pupil of the projection optical unit 35 is approximately more than 1100 mm downstream of the object field 5 in the imaging beam path. Therefore, the projection optical unit 35 also has good approximate object-side telecentricity.

[0216] The total transmittance is 17.5% in the projection optical unit 35.

[0217] The polarization rotation of the linearly polarized imaging light 16 in the imaging beam path of the projection optical unit 35 between the object field 5 and the image field 11 is approximately 1°.

[0218] The projection optical unit 35 has a chief ray angle CRA of 5.9°.

[0219] There is an inclination angle of 18.4° between the object plane 6 and the image plane 12 of the projection optical unit 35.

[0220] The object-image offset is approximately 1100 mm in the projection optical unit 35.

[0221] The optical path of the imaging beam path of the projection optical unit 35 between the object field 5 and the image field 11 is approximately 1850 mm.

[0222] The installation space requirements in the x / y directions are approximately 830 mm in the projection optical unit 35.

[0223] The working distance between the mirror closest to the wafer and the image field 11 is 75 mm in the projection optical unit 35.

[0224] The optical design data of the projection optical unit 35 can be collected from Tables 1 and 2 below, which correspond to the tables related to the embodiment according to FIG. 7 in terms of the basic design, that is, they describe the Forbes free-form surface. [Table 41] Table 1 in FIG. 8

[0225] [Table 42]

[0226] [Table 43]

[0227] [Table 44]

[0228] [Table 45] Table 2 of FIG. 8

[0229] FIGS. 9 and 10 show further embodiments of the projection optical unit or imaging optical unit 36, which can be used in the projection exposure apparatus 1 instead of the projection optical unit 10 of the embodiment according to FIG. 1. For FIGS. 1 to 8, in particular for FIGS. 2 to 8, the components and functions corresponding to those already described above are denoted by the same reference numerals, and the detailed description thereof is omitted.

[0230] The projection optical unit 36 has a total of seven mirrors M1 to M7 in the beam path between the object field 5 and the image field 11. The mirrors M1, M6 and M7 are embodied as NI mirrors. The mirrors M2, M3, M4 and M5 are embodied as mirrors for oblique incidence, that is, as mirrors on which the imaging light 16 is incident at an incident angle greater than 45°. These mirrors for oblique incidence are also referred to as GI (oblique incidence) mirrors.

[0231] The deflection effects of the four GI mirrors M2, M3, M4 and M5 are added for the imaging light 16.

[0232] First, the imaging beam path portion between the mirror M5 and the mirror M6, and second, the imaging beam path portion between the mirror M7 and the image field 11 intersect within the intersection region 37.

[0233] In the meridional yz beam path of the imaging light 16, an intermediate image 38 in the y direction is located between the GI mirror M4 and the GI mirror M5. On the plane perpendicular thereto (see FIG. 10), an intermediate field 39 in the x direction is located between the GI mirror M5 and the NI mirror M6 in the xz direction beam path of the imaging light 16.

[0234] The numerical aperture on the image side of the projection optical unit 36 is 0.33.

[0235] The average wavefront aberration RMS is 8.57 mλ in the projection optical unit 36.

[0236] The x-direction position of the entrance pupil of the projection optical unit 36 is downstream of the object field 5 in the imaging beam path by more than 2700 mm. The y-direction position of the entrance pupil of the projection optical unit 36 is upstream of the object field 5 in the imaging beam path by approximately more than 1600 mm. The projection optical unit 36 also has object-side telecentricity with a good approximation. The total transmittance is 11.1% in the projection optical unit 36.

[0237] The polarization rotation of the linearly polarized imaging light 16 in the imaging beam path of the projection optical unit 36 between the object field 5 and the image field 11 is approximately 1.8° or less.

[0238] The projection optical unit 36 has a chief ray angle CRA of 5.05°.

[0239] The object plane 6 is positioned parallel to the image plane 12. The z-direction distance between the object plane and the image plane is about 2.1 m.

[0240] The object-image offset is approximately 3.4 m in the projection optical unit 36.

[0241] The installation space requirements in the x, y, and z directions are approximately 1140 mm × 3950 mm × 1920 mm in the projection optical unit 36.

[0242] The working distance between the mirror closest to the wafer and the image field 11 is approximately 65 mm in the projection optical unit 36.

[0243] The projection optical unit 36 has no pupil obscuration. The reflecting surfaces of all the mirrors M1 to M6 have no breaks or passing apertures and are used continuously.

[0244] The imaging scale β of the projection optical unit 36 x 、β y is +0.25 in the x direction, that is, a decrease of 4.00, and -0.25 in the y direction, which is caused by the odd number of mirrors as a whole and the respective intermediate images in the x and y directions.

[0245] The image field 11 of the projection optical unit 36 is rectangular, having a spread of 26.0 mm in the x direction and a spread of 2.5 mm in the y direction.

[0246] Mirror M6 has a diameter slightly less than 1150 mm. The maximum y / x aspect ratio of the reflective surface spread is at mirror M6 in the projection optical unit 36, where it is approximately 1.56. The maximum x / y aspect ratio of the reflective surface spread is at mirror M4 in the projection optical unit 36, and is approximately 2.76.

[0247] The surface spread parameters of the optical design are summarized in the following table for the projection optical unit 36. [Table 46] Table 1 of Figure 9

[0248] [Table 47] Table 2 of Figure 9

[0249] The optical design data of the projection optical unit 36 according to FIGS. 9 and 10 are summarized in the following table in the same format as that already described above in relation to the embodiment according to FIG. 2. [Table 48] Table 3 of Figure 9

[0250] [Table 49] JPEG2025519867000083.jpg195152

[0251]

Table 50

[0252]

Table 51

[0253]

Table 52

[0254]

Table 53

[0255]

Table 54

[0256]

Table 55

[0257] As is apparent from the signs of the radii of curvature of the above table, mirrors M2, M4, and M5 have saddle-shaped surfaces.

[0258] In principle, other combinations of consecutive NI mirrors and GI mirrors are also possible. Specifically, the number of consecutive GI mirrors may vary between 3 and 5 without causing an unduly significant change in transmittance. This is because when GI mirrors are present in an increased number, they are incident at an oblique angle, and thus each individual mirror has a high transmittance.

[0259] None of the projection optical units described above have a polarization rotation of linearly polarized imaging light 16 greater than 10° between object field 5 and image field 11 in the imaging beam path. In fact, in the embodiments of the projection optical unit described above, this polarization rotation is less than 10°, less than 7°, less than 6°, less than 5°, and also less than 4.5°.

[0260] To manufacture microstructured 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. Then, the structure on the reticle 10 is projected onto the photosensitive layer of the wafer 11 using the projection exposure apparatus 1. Subsequently, the microstructures or nanostructures on the wafer 11, and thus the microstructured components, are manufactured by developing the photosensitive layer.

Claims

1. An imaging EUV optical unit (10;24;27;28;29;32;33;35;36) for imaging the object field (5) onto the image field (11), - A plurality of mirrors (M1-M4; M1-M7, M1-M6, M1-M8) 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 EUV optical unit (10; 24; 27; 28; 29; 32; 33; 35; 36) comprises at least three NI mirrors (M1-M4; M1, M6, M7; M1, M5, M6; M1, M7, M8), - The total transmittance of the aforementioned NI mirrors (M1-M4; M1-M7, M1-M6, M1-M8) is greater than 10%, - An imaging EUV optical unit in which, when linearly polarized EUV imaging light (16) is used, the total number of mirrors (M1 to M4) results in a total polarization rotation of 10° or less along the imaging beam path.

2. The imaging EUV optical unit according to claim 1, characterized by precisely four NI mirrors (M1 to M4).

3. The imaging EUV optical unit according to claim 1 or 2, characterized in that the EUV optical unit (10; 24; 27; 28; 29; 32; 33; 35; 36) comprises only NI mirrors (M1 to M4).

4. The imaging EUV optical unit according to claim 2, characterized in that the first imaging of the object field (5) in the imaging beam path occurs in the image field (11).

5. The imaging EUV optical unit according to claim 1 or 2, characterized in that at least one of the mirrors (M1 to M4; M1 to M6 / M7 / M8) has a saddle-shaped reflective surface.

6. The imaging EUV optical unit according to claim 1 or 2, characterized in that at least one of the mirrors (M2; M1; M1, M2; M2, M3) has a reflective surface with an aspect ratio (x / y) greater than 1.5 between a larger surface extent along a first reflective surface dimension (x) and a smaller surface extent along a second reflective dimension (y) perpendicular thereto.

7. The imaging EUV optical unit according to claim 1 or 2, characterized by an annular field of view (11).

8. - In each case, between the object field (5) and the first mirror (M1) in the imaging beam path, - Between two consecutive mirrors (M2, M3; M4, M5) in each case, - Between the last mirror (M6) in the imaging beam path and the image field (11) The imaging EUV optical unit according to claim 1 or 2, characterized in that the two imaging beam path portions intersect within the intersection region (34; 37).

9. The two intersecting imaging beam path sections are - The imaging beam path portion between the object field (5) and the first mirror (M1) in the imaging beam path, and - The imaging beam path portion between the second mirror (M2) and the third mirror (M3) in the imaging beam path The imaging EUV optical unit according to claim 8, characterized in that it is the same as described above.

10. The imaging EUV optical unit according to claim 1 or 2, characterized by an entrance pupil positioned in the imaging beam path upstream of the object field (5).

11. The imaging EUV optical unit according to claim 1 or 2, characterized in that at least one of the mirrors (M3, M4) has a through aperture (30, 31) for passing the imaging beam path.

12. - An illumination optical unit (4) for illuminating the object field (5) with imaging light (16), - The imaging EUV optical unit (10; 24; 27; 28; 29; 32; 33; 35; 36) according to claim 1 or 2 and An optical system equipped with

13. A projection exposure apparatus comprising the optical system described in claim 12 and an EUV light source (3).

14. - A method step of providing a reticle (7) and a 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 13, - A method step of generating microstructures and / or nanostructures on the wafer (13), A method for manufacturing structural components, including [a specific component].

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

Images