Imaging EUV optical unit for imaging object field to image field

Abstract

An imaging EUV optical unit (24) for imaging an object field (5) to an image field (11). The EUV optical unit (24) has a plurality of mirrors (M1 to M4) for guiding EUV imaging light (16) having a wavelength shorter than 30 nm from the object field (5) towards the image field (11) along an imaging beam path. The imaging EUV optical unit (24) has four NI mirrors (M1 to M4). The total transmission rate 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) result in an overall polarization rotation of no more than 10 DEG along the imaging beam path. This results in an imaging EUV optical unit having a higher EUV output while meeting strict requirements for imaging quality.

Description

[0001] This application claims the priority of German patent application No. DE 10 2022 206 112.8, the content of which is incorporated herein by reference. Technical Field

[0002] The invention relates to an imaging EUV optical unit for imaging an object field into an image field. Furthermore, the invention relates to an optical system comprising such an imaging optical unit, a projection exposure apparatus comprising such an optical system, a method for producing a microstructured or nanostructured component by means of such a projection exposure apparatus, and a microstructured or nanostructured component produced by means of such a method. Background Art

[0003] Imaging optical units of the type mentioned at the outset are known from DE 10 2018 214 437 A1, US Pat. No. 8,018,650 B2, WO 2018 / 043 433 A1, US Pat. No. 6,353,470 B1 and US Pat. No. 5,291,340. Summary of the invention

[0004] It is an object of the present invention to develop an imaging EUV optical unit of the type specified at the outset in such a way that the EUV throughput is increased while complying with strict requirements on the imaging quality.

[0005] This object is achieved according to the invention by an imaging EUV optical unit having the features of claim 1 .

[0006] According to the invention, it was realized that a small polarization rotation of not more than 10° of the imaging EUV optical unit also enables imaging of linearly polarized imaging light, without causing unwanted contrast losses within the interference range of the different diffraction orders guided in the imaging beam path required for imaging purposes. The total polarization rotation can be less than 10°, less than 8°, less than 7°, less than 6°, less than 5° and also less than 4.5°. Even smaller overall polarization rotations are possible. The overall polarization rotation is typically greater than 0.1°. The overall polarization rotation describes the cumulative polarization rotation effect of all mirrors in the imaging EUV optical unit.

[0007] The EUV optical unit can contain 3 NI mirrors or 4 NI mirrors. In principle, a smaller number of NI mirrors is also possible.

[0008] Compared to the prior art, which discloses that the total transmission of EUV optical units is usually significantly less than 10%, a total transmission of imaging EUV optical units of more than 10% represents a very significant improvement, because at a small absolute value of the total transmission, every percentage point gained in the total transmission means a significant increase in the EUV throughput through the imaging EUV optical unit. This plays a decisive role, especially when using imaging EUV optical units in the projection exposure range of chip production.

[0009] The total transmission of the NI mirror (i.e., the total transmission of the imaging EUV optical unit) can be greater than 11%, greater than 12%, greater than 13%, greater than 14%, greater than 15%, greater than 16%, greater than 17%, greater than 18%, and greater than 19%. The total transmission is typically less than 30%.

[0010] The image side numerical aperture of the imaging EUV optical unit can be less than 0.5, which facilitates imaging aberration correction and increases the reflectivity of small incident angles or small incident angle bandwidth available on the NI mirror. At least one of the multiple mirrors of the imaging EUV optical unit can be designed as a free-form surface, which cannot be described by means of a rotational symmetry axis. Multiple or all mirrors can also be designed as such free-form surfaces.

[0011] The imaging EUV optical unit may have a series of mirrors along the imaging beam path, wherein first a converging mirror is used, then a diverging mirror and then a converging mirror again, in particular in the plane of the long field direction, provided that an object field with an aspect ratio greater than 1 is used.

[0012] In the case of an imaging EUV optical unit, the object plane can extend parallel to the image plane. Alternatively, the object plane can be tilted relative to the image plane, in particular for reasons of installation space optimization.

[0013] At least one mirror in the imaging EUV optical unit may have a saddle basic shape. Additionally, at least 2, 3 or even more mirrors in the imaging EUV optical unit may have a saddle basic shape.

[0014] A chief ray angle between a chief ray of the imaging beam path in the imaging EUV optical unit and a normal to the object plane in which the object field lies may be in the range between 4.5° and 7°, for example in the range between 5° and 6°.

[0015] Due to the relatively small number of NI mirrors, the imaging EUV optical unit according to claim 2 has an advantageously high overall transmission and, as has been shown, still meets the stringent requirements for the imaging quality to be achieved.

[0016] It has also been found that important requirements with regard to the imaging quality of the EUV optical unit can also be met if, as claimed in claim 3, only NI mirrors are used, ie without additional GI mirrors for further imaging aberration correction, which in principle can have a high EUV reflectivity.

[0017] The design of the imaging EUV optical unit as claimed in claim 4, without an intermediate image between the object field and the image field, allows a particularly small angle of incidence bandwidth on the NI mirrors involved. This makes it easier to meet the requirements for highly reflective coatings, especially on the NI mirrors of the imaging EUV optical unit.

[0018] The small polarization rotation of the imaging EUV optical unit as claimed in claim 4 allows imaging of linearly polarized imaging light.

[0019] The saddle-shaped surface design of at least one of the plurality of mirrors as claimed in claim 5 (ie the individual mirror reflecting surfaces have different signs of curvature in mutually perpendicular reflecting surface sections) has been found to be particularly suitable for the optical design of an imaging EUV optical unit.

[0020] The aspect ratio as claimed in claim 6 allows guiding the imaging beam path with a small incidence angle bandwidth even if the field to be imaged has a large aspect ratio, for example, the aspect ratio may be greater than 3, greater than 5, greater than 8, or greater than 10. The aspect ratio of the reflective surface of the mirror may be greater than 1.7, greater than 2, and further greater than 2.5. This aspect ratio of the reflective surface of the mirror is typically less than 5. A corresponding aspect ratio may be particularly applicable to one of a plurality of NI mirrors of an imaging EUV optical unit.

[0021] The annular image field as claimed in claim 7 can be well corrected. Alternatively, the image field can be designed in a rectangular or non-annular arcuate manner.

[0022] According to a specific embodiment of the imaging EUV optical unit, the cross-region as claimed in claim 8 may lead to the realization of a small angle of incidence on the NI mirror and / or the realization of a small angle of incidence bandwidth, each of which is advantageous for obtaining a high reflectivity.

[0023] The embodiment as claimed in claim 9 has proven to be particularly suitable.

[0024] A crossover region may also exist between the portion of the imaging beam path between the third to last and second to last mirrors in the imaging beam path and the portion of the imaging beam path between the last mirror and the image field.

[0025] The entrance pupil in the imaging beam path upstream of the object field, that is to say outside the imaging beam path between the object field and the image field, as claimed in claim 10 allows to configure corresponding illumination optics in the region of this entrance pupil, so that it is not necessary to arrange the illumination optics close to the otherwise inaccessible pupil in the entrance pupil to be imaged into the imaging EUV optical unit. This saves light guide components and thus likewise increases EUV throughput.

[0026] At least one mirror with a passage opening as claimed in claim 11 allows the imaging EUV optical unit to be designed as a shielded system. The imaging EUV optical unit can be designed in a single-shielded manner, wherein exactly one of the multiple mirrors has a passage opening for letting the imaging beam path through. Alternatively, both mirrors can also be provided with this passage opening and, in particular, a double-shielded system can then exist. This mirror passage opening allows the design of small angles of incidence and / or small angle of incidence bandwidths on the corresponding NI mirror. Alternatively, the imaging EUV optical unit can also be designed in a non-shielded manner.

[0027] The advantages of the optical system according to claim 12, the advantages of the projection exposure apparatus according to claim 13, the advantages of the production method according to claim 14 and the advantages of the microstructure or nanostructure according to claim 15 correspond to the advantages already explained above with reference to the projection optical unit according to the invention. The EUV light source of the projection exposure apparatus can be embodied in such a way that the used wavelength occurs not more than 30 nm, not more than 25 nm, not more than 20 nm or not more than 13.5 nm, less than 13.5 nm, less than 10 nm, less than 8 nm, less than 7 nm and it is, for example, 6.7 nm or 6.9 nm. Used wavelengths of less than 6.7 nm, in particular of the order of 6 nm are also possible.

[0028] In particular, projection exposure apparatuses can be used to produce semiconductor components, such as memory chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] At least one exemplary embodiment of the present invention is described below based on the diagrams. In the diagrams:

[0030] Figure 1 Schematically shows a meridian section of a projection exposure apparatus for EUV projection lithography;

[0031] Figure 2 Meridian section display is used as a basis Figure 1 A specific embodiment of an imaging EUV optical unit of a projection lens in a projection exposure apparatus in which the imaging beam paths of the chief rays and the upper coma rays and the lower coma rays of three selected field points are depicted;

[0032] Figures 3 to 9 In each case, Figure 2 The diagrams of FIG. 1 show further specific embodiments of an imaging EUV optical unit, which can in each case again be used as a method according to Figure 1 projection lenses in projection exposure apparatus; and

[0033] Fig.10 Display from Fig. 9 What is seen in the observation direction X is based on Fig. 9 Plan view of the imaging EUV optical unit. DETAILED DESCRIPTION

[0034] Below, first refer to Figure 1 The essential components of a microlithography projection exposure apparatus 1 are described by way of example. The description of the basic structure of the projection exposure apparatus 1 and its components should not be understood as limiting.

[0035] A specific embodiment of an illumination system 2 of a projection exposure apparatus 1 has a light source or radiation source 3 and an illumination optical unit 4 for illuminating an object field 5 in an object plane 6. In an alternative specific embodiment, the light source 3 can also be arranged as a module separate from the rest of the illumination system. In this case, the illumination system does not contain the light source 3.

[0036] A reticle 7 arranged in the object field 5 is exposed. The reticle 7 is held by a reticle carrier 8 which can be displaced by a reticle displacement drive 9, in particular in a scanning direction.

[0037] For ease of explanation, Figure 1 Displays a Cartesian xyz coordinate system. The x direction is perpendicular to the drawing plane and into the latter, the y direction is in the horizontal direction, and the z direction is in the vertical direction. The scanning direction is along Figure 1 The z direction is perpendicular to the object plane 6.

[0038] The projection exposure device 1 comprises a projection optical unit 10. The projection optical unit 10 is used as an imaging optical unit for imaging the object field 5 into an image field 11 in an image plane 12. The image plane 12 extends parallel to the object plane 6. Alternatively, the angle between the object plane 6 and the image plane 12 may also be different from 0°.

[0039] The structures on the mask 7 are imaged on the photosensitive layer of a wafer 13, which is arranged in the image plane 12 in the region of the image field 11. The wafer 13 is held by a wafer carrier 14. The wafer carrier 14 can be displaced, in particular in the y direction, by a wafer displacement drive 15. Firstly the displacement of the mask 7 by the mask displacement drive 9 and secondly the displacement of the wafer 13 by the wafer displacement drive 15 can be carried out in a synchronous manner with each other.

[0040] The radiation source 3 is an extreme ultraviolet (EUV) radiation source, which in particular emits EUV radiation 16, which is also referred to below as use radiation, illumination radiation, illumination light or imaging light. In particular, the use radiation has a wavelength in the range between 5 nm and 30 nm. The radiation source 3 can be a plasma source, such as a laser produced plasma (LPP) source or a gas discharge produced plasma (GDPP) source. It can also be a synchrotron-based radiation source. The radiation source 3 can be a free electron laser (FEL).

[0041] The illumination radiation 16 emitted from the radiation source 3 is focused by a concentrator 17. The concentrator 17 may be a concentrator having one or more elliptical and / or hyperbolic reflecting surfaces. The illumination radiation 16 may be incident on at least one reflecting surface of the concentrator 17 with grazing incidence (GI), i.e. with an angle of incidence greater than 45°, or with normal incidence (NI), i.e. with an angle of incidence less than 45°. The concentrator 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.

[0042] The illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18 downstream of the condenser 17. The intermediate focal plane 18 may represent a separation between the radiation source module with the radiation source 3 and the condenser 17 and the illumination optical unit 4.

[0043] The illumination optical unit 4 comprises a deflection mirror 19 and a first facet mirror 20 arranged downstream thereof in the beam path. The deflection mirror 19 can be a plane deflection mirror or, alternatively, a mirror having a beam-influencing effect beyond a pure deflection effect. Alternatively or additionally, the deflection mirror 19 can be embodied in the form of a spectral filter, which separates the wavelength of the used light of the illumination radiation 16 from extraneous light whose wavelength deviates therefrom. If the first facet mirror 20 is arranged in a plane of the illumination optical unit 4 which is optically conjugate to the object plane 6 (as field plane), it is also referred to as a field facet mirror. The first facet mirror 20 comprises a plurality of individual first facets 21, also referred to below as field facets. Figure 1 Only some of the facets 21 are depicted by way of example.

[0044] The first facet 21 can be embodied as a macro facet, in particular a rectangular facet or a facet with an arcuate edge profile or a partially circular edge profile. The first facet 21 can be embodied as a plane facet, or alternatively as a facet with a convex or concave curvature.

[0045] As is known, for example, from DE 10 2008 009 600 A1, the first facet mirror 21 itself can also be composed of multiple individual mirrors, in particular multiple micromirrors. The first facet mirror 20 can be formed in particular as a microelectromechanical system (MEMS system). For details, please refer to DE 10 2008 009 600 A1.

[0046] The illuminating radiation 16 propagates horizontally between the condenser 17 and the deflection mirror 19 , that is to say in the y direction.

[0047] In the beam path of the illumination optical unit 4, the second facet mirror 22 is arranged downstream of the first facet mirror 20. If the second facet mirror 22 is arranged in the pupil plane of the illumination optical unit 4, it is also called a pupil facet mirror. The second facet mirror 22 can also be arranged at a distance from the pupil plane of the illumination optical unit 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also called a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1, EP 1 614 008 B1 and US 6,573,978.

[0048] The second facet mirror 22 comprises a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also called pupil facets.

[0049] The second facet 23 can likewise be a macroscopic facet, which can have, for example, a circular, rectangular or hexagonal boundary, or alternatively can be a facet consisting of a plurality of micromirrors. In this regard, reference is likewise made to DE 10 2008 009 600 A1.

[0050] The second facet 23 may have a planar reflecting surface or alternatively a convexly or concavely curved reflecting surface.

[0051] The illumination optical unit 4 thus forms a two-facet system. This basic principle is also called a fly's eye condenser (fly's eye integrator).

[0052] It may be advantageous to configure the second facet mirror 22 imprecisely in a plane optically conjugate to the pupil plane of the projection optical unit 10. In particular, the pupil facet mirror 22 may be configured tilted relative to the pupil plane of the projection optical unit 10, as described, for example, in DE 10 2017 220 586 A1.

[0053] By means of the second facet mirror 22, each first facet 21 is imaged into the object field 5. The second facet mirror 22 is the last beam shaping mirror or, in fact, the last mirror of the illumination radiation 16 in the beam path upstream of the object field 5.

[0054] In another specific embodiment (not shown) of the illumination optical unit 4, a transfer optical unit which particularly helps to image the first facet 21 into the object field 5 can be arranged in the beam path between the second facet mirror 22 and the object field 5. The transfer optical unit can have exactly one mirror or, alternatively, two or more mirrors, which are arranged one after the other in the beam path of the illumination optical unit 4. The transfer optical unit can in particular comprise one or two normal incidence mirrors (NI mirrors) and / or one or two grazing incidence mirrors (GI mirrors).

[0055] exist Figure 1 In the specific embodiment shown, the illumination optical unit 4 has exactly three mirrors downstream of the condenser 17 , in particular a deflection mirror 19 , a field facet mirror 20 and a pupil facet mirror 22 .

[0056] In another specific embodiment of the illumination optical unit 4 , the deflection mirror 19 can also be omitted, so that the illumination optical unit 4 can have exactly two mirrors downstream of the condenser 17 , in particular a first facet mirror 20 and a second facet mirror 22 .

[0057] The imaging of the first facet 21 into the object plane 6 by the second facet 23 or using the second facet 23 and the transfer optics is usually only an approximate imaging.

[0058] The projection optical unit 10 comprises a plurality of mirrors Mi which are numbered sequentially according to their arrangement in the beam path of the projection exposure apparatus 1 .

[0059] exist Figure 1 In the example shown, the projection optical unit 10 comprises six mirrors M1 to M6. The alternative of using four, eight, ten, twelve or any other number of mirrors Mi is also possible. The projection exposure unit 10 is a double shadow optical unit. Each of the penultimate mirror M5 and the last mirror M6 has a passage opening for the illumination radiation 16.

[0060] The imaging light 16 directed from the last mirror M6 to the image field 11 passes through the channel opening of the mirror M5. The imaging light 16 reflected from the third-to-last mirror M4 to the second-to-last mirror M5 passes through the channel opening of the mirror M6. Around their channel openings, the mirrors M5 and M6 are used to reflectively guide the imaging light 16.

[0061] The image-side numerical aperture of the projection optical unit 10 is greater than 0.25, and it may also be greater than 0.3, and may be 0.33, for example.

[0062] The image side numerical aperture is typically less than 0.9, less than 0.75, less than 0.6 and may be less than 0.5. In principle, the image side numerical aperture may also be larger.

[0063] The reflective surface of the reflector Mi can be embodied as a free-form surface without an axis of rotational symmetry. Alternatively, the reflective surface of the reflector Mi can be designed as an aspheric surface with exactly one axis of rotational symmetry of the reflective surface shape. Like the reflectors of the illumination optical unit 4, the reflector Mi can have a highly reflective coating for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating molybdenum and silicon layers.

[0064] 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 can be approximately the same as the z distance between the object plane 6 and the image plane 12.

[0065] In particular, the projection optical unit 10 can have variant embodiments. In particular, it can have different imaging ratios β in the x and y directions. x , β y The two imaging ratios β of the projection optical unit 10 x , β y Preferably (β x ,β y )=(+ / -0.25,+ / -0.125). A positive imaging ratio β means imaging without image reversal. A negative sign of the imaging ratio β means imaging with image reversal.

[0066] For example, the projection optical unit 10 is reduced in size in the x-direction (ie, the direction perpendicular to the scanning direction) by a ratio of 4:1.

[0067] In the case of a modified embodiment, the projection optical unit 10 is reduced in size in the y direction (ie the scanning direction) by a ratio of 8:1.

[0068] Other imaging ratios are also possible. Imaging ratios with the same sign and the same absolute value in the x-direction and the y-direction are also possible, for example with an absolute value of 0.125 or 0.25.

[0069] The number of intermediate image planes in the x- and y-directions in the beam path between the object field 5 and the image field 11 may be the same or may differ depending on the specific 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 2018 / 0074303 A1.

[0070] In each case, one of the plurality of pupil facets 23 is assigned to exactly one of the plurality of field facets 21 for forming in each case an illumination channel for illuminating the object field 5. In particular, this can result in The far field is decomposed into a plurality of object fields 5 with the aid of the field facets 21. The field facets 21 generate a plurality of images of the intermediate focus on the pupil facets 23 respectively assigned thereto.

[0071] By means of the assigned pupil facets 23, the field facets 21 are in each case imaged onto the reticle 7 in a mutually superimposed manner for illuminating the object field 5. The illumination of the object field 5 is in particular as homogeneous as possible. It preferably has a homogeneity error of less than 2%. Field homogeneity can be achieved by superposition of different illumination channels.

[0072] The entrance pupil illumination of the projection optical unit 10 can be geometrically defined by the configuration of the pupil facets. The intensity distribution in the entrance pupil of the projection optical unit 10 can be set by selecting the illumination channels, in particular the subset of pupil facets through which the light is directed. This intensity distribution is also referred to as the illumination setting illumination pupil filling.

[0073] By redistributing the illumination channels, a likewise better pupil homogeneity can be achieved which is illuminated in a defined manner in a segment region of the illumination pupil of the illumination optical unit 4 .

[0074] Further aspects and details of the illumination of the object field 5 and in particular of the entrance pupil illumination of the projection optical unit 10 are described below.

[0075] The projection optical unit 10 can in particular have a concentric entrance pupil. The latter can be accessible, or it can be inaccessible.

[0076] The entrance pupil of the projection optical unit 10 cannot usually be precisely illuminated using the pupil facet mirror 22. In the case of an imaging of the projection optical unit 10 with telecentric imaging of the center of the pupil facet mirror 22 onto the wafer 13, the aperture rays usually do not intersect at a single point. However, a region can be found in which the distance of the aperture rays determined in pairs becomes minimal. This region represents the entrance pupil or a region in real space conjugate therewith. In particular, this region has a finite curvature.

[0077] It is possible that the entrance pupil positions of the tangential beam path and the sagittal beam path of the projection optical unit 10 can also be different. In this case, an imaging element, in particular an optical component part of the transfer optical unit, should be arranged between the second facet mirror 22 and the reticle 7. With the help of this optical element, different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

[0078] exist Figure 1 In the component configuration of the illumination optical unit 4 shown, the pupil facet mirror 22 is arranged in a region conjugate with the entrance pupil of the projection optical unit 10. The field facet mirror 20 is arranged such that it is tilted relative to the object plane 6. The first facet mirror 20 is arranged in a tilted manner relative to the configuration plane defined by the deflection mirror 19.

[0079] The first facet mirror 20 is arranged such that it is inclined relative to the arrangement plane defined by the second facet mirror 22 .

[0080] Figure 2 A further embodiment of the projection optical unit or imaging optical unit 24 is shown, which can replace the Figure 1 The projection optical unit 10 in the specific embodiment of the invention is used in the projection exposure device 1. Figure 1 Explained components and functions have the same reference numerals and will not be discussed again in detail.

[0081] Figure 2 Describe in each case from Figure 2 2 . The beam paths of three individual light rays 25 emanating from three object field points spaced apart from one another in the y direction in FIG. 2 are depicted the chief ray 26, that is to say the individual light rays 25 which pass through the pupil centre in the pupil plane of the projection optical unit 24, and the upper and lower coma rays for the three object field points in each case. Starting from the object field 5, the chief ray 26 forms an angle CRA of 5.22° with the normal to the object plane 6. The design of the projection optical unit 24 for the reflection reticle 7 exists due to this chief ray angle CRA. This therefore 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 or imaging light 16 reflected by the reticle 7.

[0082] The image-side numerical aperture of the projection optical unit 24 is 0.33.

[0083] according to Figure 2 The projection optical unit 24 has a total of four mirrors, which are numbered consecutively M1 to M4 in the order of the beam paths of the individual light rays 25 originating from the object field 4 .

[0084] Figure 2 Portions of the calculated reflection surfaces of the reflectors M1 to M4 are depicted. The actually used areas of the reflection surfaces as well as the overhangs are present in the actual reflectors M1 to M4. These used reflection surfaces are determined in a manner known per se by Figure 2 The reflector body not shown in the figure supports.

[0085] In accordance with Figure 2 In the projection optical unit 24, all mirrors M1 to M4 are embodied as mirrors for vertical or normal incidence, that is, mirrors on which the imaging light 16 is incident at an angle of incidence of less than 45°. These vertical incidence mirrors are also called NI (normal incidence) mirrors.

[0086] The mirrors M1 to M4 have a coating which optimizes the reflectivity of the mirrors M1 to M4 for the imaging light 16. This can be a ruthenium coating, a molybdenum coating or a molybdenum coating with a ruthenium top layer. These highly reflective layers can be embodied as a multilayer, wherein successive layers can be made of different materials. Alternating layers of materials can also be used. A typical multilayer can have fifty double layers, each made of a layer of molybdenum and a layer of silicon.

[0087] To calculate the total reflectivity of the projection optical unit 24, the system transmission is calculated as follows: Based on the incident angle of the guided light (i.e., the chief ray of the central object field point), the mirror reflectivity at each mirror surface is determined and combined by multiplication to form the system transmission.

[0088] Details on calculating the reflectivity are explained in WO 2015 / 014 753 A1. More information on the reflectivity of NI mirrors (normal incidence mirrors) can be found in DE 101 55 711 A.

[0089] The system or overall transmission of the projection optical unit 24 (ie the total number of mirrors M1 to M4) is 17.55%. On average, the reflectivity of each of the four mirrors is therefore approximately 64.7%.

[0090] The polarization rotation of the linearly polarized imaging light 16 in the imaging beam path of the projection optical unit 24 between the object field 5 and the image field 11 is approximately 3.6°.

[0091] None of the reflectors M1 to M4 has a passage opening, and the reflectors are used in a reflective manner in a continuous area without gaps. Therefore, the reflectors M1 to M4 have a reflective surface without openings.

[0092] In the projection optical unit 24, the image field 11 is the first field in the imaging beam path downstream of the object field 5. As such, the projection optical unit 24 has no intermediate image plane.

[0093] The z distance between the object field and the image field 8 (installation length) is about 1750 mm. The y distance between the central field point of the object field 5 and the central field point of the image field 11 (object-image offset) is about 1380 mm. In the xz plane, the entrance pupil of the projection optical unit 24 is located about 4100 mm downstream of the object field 5 in the imaging beam path. In the yz plane, the entrance pupil is located more than 10 m upstream of the object field 5 in the imaging beam path. Therefore, the projection optical unit 24 is telecentric on the object side to a good approximation.

[0094] The projection optical unit 24 is telecentric on the image side.

[0095] The minimum distance between the wafer 13 and the mirror M3 closest to the wafer is 75 mm; this distance is also called the working distance.

[0096] When the used wavelength of the imaging light 3 is 13.5 nm, the average wavefront aberration RMS of the projection optical unit 24 is less than 35 mλ.

[0097] The following Tables 1 and 2 summarize the basic data of the projection optical unit 24 again:

[0098] Wavelength used 13.5nm Image side numerical aperture 0.33 Imaging ratio -4.00 Chief Ray Angle CRA 5.22° Etendue <![CDATA[7.08mm 2 ]]> Average wavefront aberration RMS 33.28mλ Total transmission rate 17.55％ Entrance pupil position (x) 4101.25mm Entrance pupil position (y) -39609.53mm Object Image Offset 1379.52mm Working distance (M3 to image field) 75mm z distance between object field and image field 2156.00mm The angle between the object plane and the image plane -0.0° Installation space requirement xyz (980x 1703x 1756)mm

[0099] Figure 2 Table 1

[0100] M1 M2 M3 M4 Maximum incident angle / ° 10.1 14.9 23.7 17.0 Minimum incident angle / ° 2.6 11.9 16.9 3.8 Reflector range (x) / mm 388.4 980.1 571.3 738.4 Reflector range (y) / mm 326.4 460.3 519.4 721.4 Maximum reflector diameter / mm 388.7 980.2 585.1 738.9

[0101] Figure 2 Table 2

[0102] The ranges specified in Table 2 relate in each case to the used reflective surfaces of the mirrors M1 to M4 .

[0103] The maximum angle of incidence of imaging light 16 on mirrors M1 to M4 is present at mirror M3 and is also less than 25° there.

[0104] The minimum angle of incidence occurs at mirror M1 and is greater than 2.5°. The maximum angle of incidence bandwidth, i.e., the difference between the maximum and minimum angles of incidence of the imaging light 16, exists at the last mirror M4 and is less than 15° there. The minimum angle of incidence bandwidth occurs at mirror M2 and is 3° there.

[0105] The diameter of the mirrors M1 to M4 is no greater than 1000 mm. In terms of x-range, the M2 mirror is the largest mirror in the projection optical unit 24. In particular, the mirror M2 has a larger x-range than the mirror M4.

[0106] The mirror M2 has a reflective surface whose x / y aspect ratio between the larger x surface area and the smaller y surface area is greater than 1.5 and which in the case of the mirror M2 of the projection optical unit 24 is 2.13, ie also greater than 2.

[0107] In the projection optical unit 24, the image field 11 is annular, and its annular radius is 260 mm. The x range of the image field 11 is 26 mm. The y range of the image field 11 is 2.5 mm.

[0108] The reflectors M1 to M4 are embodied as free-form surfaces which cannot be described by rotationally symmetric functions. Other embodiments of the projection optical unit 24 are also possible, in which at least one of the reflectors M1 to M4 is embodied as a rotationally symmetric aspheric surface. All reflectors M1 to M4 can also be embodied as such as aspheric surfaces.

[0109] The free-form surface can be described by the following free-form surface equation (Equation 1):

[0110]

[0111] The following apply to the parameters of this equation (1):

[0112] Z is the sagittal height of the free-form surface at point x, y, where x 2 +y 2 =r 2 Here, r is the distance from the reference axis of the free-form surface equation

[0113] (x=0; y=0).

[0114] In the free-form surface equation (1), C1, C2, C3, ... represent the coefficients of the powers x and y of the free-form surface series expansion.

[0115] In the case of a conical base, c x 、c y is a constant corresponding to the vertex curvature of the corresponding asphere. Therefore, c x =1 / RDX and c y =1 / RDY applies. x and k y , also called CCX and CCY, each corresponds to the conic constant of the corresponding aspheric surface. Therefore, equation (1) describes a biconical freeform surface.

[0116] An alternative possible free-form surface can be generated from a rotationally symmetrical reference surface.Such a free-form surface for a reflective surface of a mirror of a projection optical unit of a microlithographic projection exposure apparatus is known from US 2007-0058269 A1.

[0117] Alternatively, free-form surfaces can also be described by means of two-dimensional spline surfaces. Examples of these are Bezier curves or non-uniform rational basis splines (NURBS). For example, a two-dimensional spline surface can be described by a grid of points in the xy plane and the associated z-values, or by these points and the gradients associated therewith. 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 their continuity and differentiability. Examples of this are analytical functions.

[0118] The pupil-defining aperture stop AS is arranged in the region of or on the reflector M3 of the projection optical unit 24; Figure 2 As shown. For example, implementation options for this aperture stop are disclosed in WO 2016 / 188934 A1. In addition to having a single pupil-defining aperture stop AS, its effect can also be exploited by configuring a plurality of pupil-defining partial stops at different points within the projection optical unit 24.

[0119] The arrangement plane of the aperture stop AS coincides with the pupil plane of the projection optical unit 24 .

[0120] The optical design data of the reflecting surfaces in the mirrors M1 to M4 of the projection optical unit 24 can be gathered from the following further tables.

[0121] Table 3 specifies the coordinates of the surface origin of the corresponding mirror surface and of the region of the object field 5 relative to the xyz coordinate system of the image field 11 .

[0122] The first column specifies the distance of the corresponding mirror or object field 5 from the central coordinate origin of the image field 11 in the z direction (first column) and in the y direction (second column).

[0123] The third column of Table 3 additionally specifies the values ​​of the inclination of the mirrors M1 to M4 or the corresponding surfaces of the object field 5 relative to the xy plane of the image field 11. Figure 2 In the specific embodiment of the invention, both the object field 5 and the image field 11 are not tilted relative to the x-axis and extend parallel to each other.

[0124] Table 4 lists the parameters RDX, RDY, CCX, CCY of the reflectors M4 to M1, respectively, and the values ​​of the coefficients C1, C2, C3, etc. of the free surface series expansion obtained according to the above equation (1) according to the power order of x and y.

[0125] Mirrors with different signs in their RDX and RDY values ​​have a saddle point-type or minimax basic shape.

[0126] z distance [mm] y distance [mm] Tilt around x-axis [degrees] Image Field 0 0 0 M4 1052.341063 0 15.501098 M3 85.619483 580.915378 10.659276 M2 1817.74382 876.483984 12.560313 M1 263.752971 1956.707604 21.254751 Material Field 2156 1379.517221 0

[0127] Figure 2 Table 3

[0128]

[0129]

[0130]

[0131]

[0132]

[0133]

[0134]

[0135]

[0136]

[0137]

[0138]

[0139]

[0140]

[0141]

[0142]

[0143]

[0144] Figure 2 Table 4

[0145] Figure 3 A further embodiment of the projection optical unit or imaging optical unit 27 is shown, which can replace the Figure 1 The projection optical unit 10 in the specific embodiment is used in the projection exposure device 1. Figure 1 and Figure 2 , especially in combination Figure 2 The components and functions of those explained are denoted by the same reference numerals and are not discussed again in detail.

[0146] In the projection optical unit 27, the annular field radius of the image field 11 is 80 mm. In the projection optical unit 27, the image field dimensions in the x-direction and the y-direction are the same as those of the projection optical unit 24.

[0147] The core parameters of the optical design related to the projection optical unit 27 are listed again below:

[0148] Wavelength used 13.5nm Image side numerical aperture 0.25 Imaging ratio -4.00 Chief Ray Angle CRA 5.86° Etendue <![CDATA[4.06mm 2 ]]> Average wavefront aberration RMS 17.57mλ Total transmission rate 17.59％ Entrance pupil position (x) 4095.77mm Entrance pupil position (y) -40778.74mm Object Image Offset 1413.37mm Working distance (M3 to image field) 81mm z distance between object field and image field 2156.00mm The angle between the object plane and the image plane 0.0° Installation space requirement xyz (758x 1600x 1742)mm

[0149] Figure 3 Table 1

[0150]

[0151]

[0152] Figure 3 Table 2

[0153] The maximum angle of incidence of the imaging light 16 on the mirrors M1 to M4 is present at the mirror M3 and is 22.9°. Thus, for all individual light rays, an angle of incidence of less than 25° is present on all mirrors M1 to M4 of the projection optical unit 27 .

[0154] The minimum angle of incidence occurs at reflector M1 and is 3.9°. The angle of incidence bandwidth between the minimum angle of incidence and the maximum angle of incidence is less than 10° for all reflectors M1 to M4 and is no greater than 6° for each of reflectors M1 to M3. The minimum angle of incidence bandwidth, i.e. the difference between the maximum and minimum angles of incidence, exists at reflector M2 and is less than 2.5° there.

[0155] The diameter of the mirrors M1 to M4 is no greater than 760 mm. The mirror M2 is the largest mirror in terms of x-range. Specifically, the mirror M2 has a larger x-range than the last mirror M4 of the projection optical unit 27.

[0156] The average wavefront aberration RMS in the projection optical unit 27 is less than 20 mλ.

[0157] The image-side numerical aperture of the projection optical unit 27 is 0.25.

[0158] The maximum x / y aspect ratio of the surface area is at the mirror M2 in the projection optical unit 27 and is 2.14 there.

[0159] The total transmission in the projection optical unit 27 is 17.59%.

[0160] 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°.

[0161] according to Figure 3 The optical design data of the projection optical unit 27 is listed in the following table, and its format is the same as that of the above description according to Figure 2 The format is the same as explained in the specific embodiment.

[0162]

[0163]

[0164] Figure 3 Table 3

[0165]

[0166]

[0167]

[0168]

[0169]

[0170]

[0171]

[0172]

[0173]

[0174]

[0175]

[0176]

[0177]

[0178]

[0179]

[0180]

[0181] Figure 3 Table 4

[0182] Figure 4 A further embodiment of the projection optical unit or imaging optical unit 28 is shown, which can replace the Figure 1 The projection optical unit 10 in the specific embodiment is used in the projection exposure device 1. Figures 1 to 3 , especially in combination Figure 2 and Figure 3 Corresponding components and functions of those explained are denoted by the same reference numerals and will not be discussed again in detail.

[0183] The image field 11 of the projection optical unit 28 is rectangular and the x extent of the image field 11 is 26 mm. The y extent of the image field 11 is 2.5 mm.

[0184] The aperture stop AS may be arranged in the region of an entrance pupil located in the beam path of the imaging light 16 between the mirrors M3 and M4.

[0185] The following Tables 1 and 2 summarize again the basic data of the projection optical unit 28:

[0186]

[0187]

[0188] Figure 4 Table 1

[0189] M1 M2 M3 M4 Maximum incident angle / ° 7.0 10.3 18.0 7.0 Minimum incident angle / ° 2.6 9.4 6.5 2.6 Reflector range (x) / mm 464.9 418.3 236.1 739.6 Reflector range (y) / mm 277.2 293.6 228.5 717.7 Maximum reflector diameter / mm 465.7 419.3 236.8 740.4

[0190] Figure 4 Table 2

[0191] The mirrors M1 to M4 each have a very small angle of incidence bandwidth, which is less than 12° for all individual rays of the imaging light 16. A very small angle of incidence bandwidth of less than 2°, even less than 1°, exists at the mirror M2 of the projection optical unit 28. The absolute angles of incidence at the mirrors M1 to M4 are also quite small in each case, in particular less than 20° for all individual rays. In the case of the mirrors M1 and M4, these absolute angles of incidence are even less than 10° and even less than 8° for all individual rays.

[0192] None of the mirrors M1 to M4 of the projection optical unit 28 has a diameter greater than 750 mm.

[0193] The maximum x / y aspect ratio of the surface area is at the mirror M1 in the projection optical unit 28 and is 1.68 there.

[0194] The image-side numerical aperture of the projection optical unit 28 is 0.28.

[0195] The projection optical unit 28 has an overall transmission of 19.21%.

[0196] 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°.

[0197] The entrance pupil of the projection optical unit 28 is located in both the xz plane and the yz plane in the imaging beam path upstream of the object field 5, specifically about 1750 mm in the imaging beam path upstream of the object field 5. Specifically, the pupil facet mirror of the illumination optical unit 4 can be arranged there.

[0198] according to Figure 4 The optical design data of the projection optical unit 28 are listed in the following table, and its format is the same as that described above according to Figure 2 The format of the specific embodiment explanation is the same.

[0199] z distance [mm] y distance [mm] Tilt around x-axis [degrees] Image Field 0 0 0 M4 1265.259208 0 -4.891753 M3 87.643865 -203.060378 2.252342 M2 1874.587205 -658.154257 4.467444 M1 344.596382 -801.522927 -0.176651 Material Field 2155.723202 -959.975992 0

[0200] Figure 4 Table 3

[0201]

[0202]

[0203]

[0204]

[0205]

[0206]

[0207]

[0208]

[0209]

[0210]

[0211]

[0212]

[0213] Figure 4 Table 4

[0214] Figure 5 A further embodiment of the projection optical unit or imaging optical unit 29 is shown, which can replace the Figure 1 The projection optical unit 10 of the specific embodiment is used in the projection exposure device 1. Figures 1 to 4 , especially in combination Figures 2 to 4 Corresponding components and functions of those explained are denoted by the same reference numerals and will not be discussed again in detail.

[0215] The basic design of the projection optical unit 29 is similar to that of DE 10 2018 214 437 A1, for example. Figure 2 The specific embodiments in .

[0216] The first two mirrors M1 and M2 always serve for reflection, and the two subsequent mirrors M3 and M4 each have a passage opening 30 , 31 for the imaging light 16 in the imaging beam path through the projection optical unit 29 .

[0217] Due to the passage opening 30, 25.3% of the total reflection surface of the reflector M3 is shaded. Due to the passage opening 31, 25.6% of the total reflection surface of the reflector M4 is shaded.

[0218] The image-side numerical aperture of the projection optical unit 29 is 0.33.

[0219] The image field 11 of the projection optical unit 29 is rectangular. The image field 11 has an x ​​extension of 26 mm and a y extension of 2.5 mm.

[0220] The pupil plane exists in the imaging beam path between mirrors M3 and M4. Figure 5 As shown, the aperture stop AS can be arranged here.

[0221] The total transmission in the projection optical unit 29 is 17.28%.

[0222] 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°.

[0223] The object-image offset in the projection optical unit 29 is significantly smaller than in the projection optical units 27 and 28 and is approximately 200 mm in the projection optical unit 29 .

[0224] The core parameters of the optical design which are relevant in this case to the projection optical unit 29 are listed again below:

[0225] Wavelength used 13.5nm Image side numerical aperture 0.33 Imaging ratio -4.00 Chief Ray Angle CRA 5.00° Etendue <![CDATA[7.08mm 2 ]]> Average wavefront aberration RMS 50.64mλ Total transmission rate 17.28％ Entrance pupil position (x) 2812.91mm Entrance pupil position (y) 2964.98mm Object Image Offset 203.26mm Working distance (M3 to image field) 75mm z distance between object field and image field 2385.61mm The angle between the object plane and the image plane -0.0° Installation space requirement xyz (1096x 1070x 2051)mm

[0226] Figure 5 Table 1

[0227] M1 M2 M3 M4 Maximum incident angle / ° 26.2 23.5 9.5 3.3 Minimum incident angle / ° 14.4 13.2 0.2 0.2 Reflector range (x) / mm 164.8 235.0 381.0 1096.1 Reflector range (y) / mm 92.7 152.7 370.7 1069.6 Maximum reflector diameter / mm 165.4 235.8 381.7 1096.1

[0228] Figure 5 Table 2

[0229] Very small angles of incidence exist on each of the mirrors M3 and M4 of the projection optical unit 29, and for each individual ray these angles of incidence are less than 10°. The maximum angle of incidence in the mirror M4 is even less than 5°, even less than 4°.

[0230] The maximum x / y aspect ratio of the reflective surface area is at the mirror M1 in the projection optical unit 29 and is 1.77 there.

[0231] None of the mirrors M1 to M4 has a diameter greater than 1100 mm.

[0232] according to Figure 5 The optical design data of the projection optical unit 29 is listed in the following table, and its format is the same as that of the above description according to Figure 2 The format of the specific embodiment explanation is the same.

[0233]

[0234]

[0235] Figure 5 Table 3

[0236]

[0237]

[0238]

[0239]

[0240]

[0241]

[0242]

[0243]

[0244]

[0245]

[0246]

[0247]

[0248] Figure 5 Table 4

[0249] Figure 6 A further embodiment of the projection optical unit or imaging optical unit 32 is shown, which can replace the Figure 1 The projection optical unit 10 of the specific embodiment is used in the projection exposure device 1. Figures 1 to 5 , especially in combination Figures 2 to 5 Corresponding components and functions of those explained are denoted by the same reference numerals and will not be discussed again in detail.

[0250] Compared to Figure 5 The projection optical unit 29 is configured according to Figure 6 In the projection optical unit 32, the object plane 6 is not parallel to the image plane 12, but is tilted relative to the image plane 12. In the projection optical unit 32, the angle between the object plane 6 and the image plane 12 is 8.3°. Therefore, the angle is less than 10°.

[0251] The core parameters of the optical design which are relevant in this case to the projection optical unit 32 are listed again below:

[0252] Wavelength used 13.5nm Image side numerical aperture 0.33 Imaging ratio -4.00 Chief Ray Angle CRA 5.00° Etendue <![CDATA[7.08mm 2 ]]> Average wavefront aberration RMS 61.41mλ Total transmission rate 17.37％ Entrance pupil position (x) 1883.14mm Entrance pupil position (y) 1601.18mm Object Image Offset 109.39mm Working distance (M3 to image field) 75mm z distance between object field and image field 2156.00mm The angle between the object plane and the image plane -8.3° Installation space requirement xyz (997x 975x 1797)mm

[0253] Figure 6 Table 1

[0254] M1 M2 M3 M4 Maximum incident angle / ° 24.6 26.0 9.3 3.9 Minimum incident angle / ° 11.5 13.7 0.0 0.2 Reflector range (x) / mm 157.3 217.9 399.7 997.0 Reflector range (y) / mm 91.7 161.9 392.3 975.0 Maximum reflector diameter / mm 157.7 218.9 400.0 997.8

[0255] Figure 6 Table 2

[0256] The maximum x / y aspect ratio of the reflective surface area is at the mirror M1 in the projection optical unit 32 and is 1.71 there.

[0257] The total transmission rate of the projection optical unit 32 is 17.37%.

[0258] 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°.

[0259] Due to the passage opening 30, 24.4% of the total reflective surface of the reflector M3 is shaded. Due to the passage opening 31, 26.0% of the total reflective surface of the reflector M4 is shaded. Figure 6 The optical design data of the projection optical unit 32 is then combined with the above-mentioned Figure 2 The same format of explanation of the specific examples is listed below.

[0260]

[0261]

[0262] Figure 6 Table 3

[0263]

[0264]

[0265]

[0266]

[0267]

[0268]

[0269]

[0270]

[0271] Figure 6 Table 4

[0272] Figure 7 A further embodiment of the projection optical unit or imaging optical unit 33 is shown, which can replace the Figure 1 The projection optical unit 10 of the specific embodiment is used in the projection exposure device 1. Figures 1 to 6 , especially in combination Figures 2 to 6 Corresponding components and functions of those explained are denoted by the same reference numerals and will not be discussed again in detail.

[0273] The image-side numerical aperture of the projection optical unit 33 is 0.33.

[0274] The average wavefront aberration RMS in the projection optical unit 33 is 47.2 mλ.

[0275] The x position of the entrance pupil is located in the imaging beam path more than 5 m downstream of the object field 5. The y position of the entrance pupil of the projection optical unit 33 is located in the imaging beam path more than 8 m upstream of the object field 5. Therefore, there is also a well-approximated object-side telecentricity in the projection optical unit 33.

[0276] The total transmission in the projection optical unit 33 is 15.6%.

[0277] 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°.

[0278] All of the above-mentioned projection optical units are designed so that they 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 along the imaging beam path between the object field 5 and the image field 11 undergoes a polarization rotation of less than 10°, less than 7° and furthermore less than 5°. This polarization rotation is very small in the projection optical units 28 and 29 and in particular can be less than 1°. Typically, the polarization rotation is greater than 0°.

[0279] The chief ray angle CRA of the projection optical unit 33 is 6.0°.

[0280] There is a tilt angle of 8.6° between the object plane 6 and the image plane 12 in the projection optical unit 33 .

[0281] The object-image offset in the projection optical unit 33 is 415 mm.

[0282] The installation space requirement in the x / y direction of the projection optical unit 33 is 1450 mm.

[0283] In the projection optical unit 33, the working distance between the mirror closest to the wafer and the image field 11 is 50 mm.

[0284] In the projection optical unit 33 , the imaging beam path section between the object field 5 and the mirror M1 intersects in an intersection region 34 with the imaging beam path section between the mirror M2 and the mirror M3 .

[0285] The reflectors M1 to M4 of the projection optical unit 33 also have free-form reflective surfaces. These free-form surfaces of the reflectors M1 to M4 of the projection optical unit 33 can be described by surface equations, which are explained in the professional article "Characterizing the shape of freeform optics" by GW Forbes, journal "Optics Express", 2012, Vol. 20, No. 3, pp. 2483 to 2499. Free-form surfaces with such a surface description are also called Forbes free-form surfaces.

[0286] The Forbes free-form surface equation is:

[0287]

[0288] The following apply to the parameters of this equation (2):

[0289] z is the sag of the free-form surface at points h and θ, where h is the radial coordinate of the point and θ is the azimuthal coordinate of the point;

[0290] u=h / NH is the standardized radial coordinate;

[0291] ρ is the curvature, which is the reciprocal of the radius of curvature RD;

[0292] κ is the quadratic constant, that is, it corresponds to the CC value in the table above;

[0293] Q m n are orthogonal polynomials on the unit circle, described in the aforementioned professional article in Forbes.

[0294] The optical design data of the projection optical unit 33 can be collected from the following Tables 1 and 2. The coefficients in Table 2 below are the coefficients of the above equation (2) The coefficient is zero.

[0295] according to Figure 7 The optical design data of the projection optical unit 33 in the embodiment are listed in the following table, and its format is the same as that of the above description according to Figure 2 The format of the specific embodiment explanation is the same.

[0296] z distance [mm] y distance [mm] Tilt around x-axis [degrees] Image Field 0 0 0 M4 499.479655 -1.252109 -14.266825 M3 129.297951 -202.71356 0.224322 M2 1450.112914 -934.129645 23.188425 M1 74.84813 -503.522568 7.398378 Material Field 2080.169381 -412.759825 -8.55828

[0297] Figure 7 Table 1

[0298]

[0299]

[0300]

[0301]

[0302]

[0303]

[0304]

[0305] Figure 7 Table 2

[0306] Figure 8 A further embodiment of the projection optical unit or imaging optical unit 35 is shown, which can replace the Figure 1 The projection optical unit 10 of the specific embodiment is used in the projection exposure device 1. Figures 1 to 7 , especially in combination Figures 2 to 7 Components and functions corresponding to those explained are denoted by the same reference numerals and will not be discussed again in detail.

[0307] The image-side numerical aperture of the projection optical unit 35 is 0.26.

[0308] The average wavefront aberration RMS in the projection optical unit 35 is 71.8 mλ.

[0309] The x position of the entrance pupil of the projection optical unit 35 is located in the imaging beam path more than 1100 mm downstream of the object field 5. The y position of the entrance pupil of the projection optical unit 35 is located in the imaging beam path more than 1100 mm downstream of the object field 5. Therefore, there is also a well-approximated object-side telecentricity in the projection optical unit 35.

[0310] The total transmission in the projection optical unit 35 is 17.5%.

[0311] 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°.

[0312] The chief ray angle CRA of the projection optical unit 35 is 5.9°.

[0313] There is an inclination angle of 18.4° between the object plane 6 and the image plane 12 in the projection optical unit 35 .

[0314] The object-image offset in the projection optical unit 35 is approximately 1100 mm.

[0315] The light path in the imaging beam path of the projection optical unit 35 between the object field 5 and the image field 11 is approximately 1850 mm.

[0316] The installation space requirement in the projection optical unit 35 in the x / y direction is approximately 830 mm.

[0317] In the projection optical unit 35, the working distance between the mirror closest to the wafer and the image field 11 is 75 mm.

[0318] The optical data of the projection optical unit 35 can be gathered from the following Tables 1 and 2, which correspond, in terms of their basic design, to the values ​​according to Figure 7 Table related to a specific embodiment of the invention, that is, it describes a Forbes free-form surface.

[0319] z distance [mm] y distance [mm] Tilt around x-axis [degrees] Image Field 0 0 0 M4 1383.433074 -13.578952 -4.823026 M3 75 -241.226417 2.208116 M2 1528.071357 -566.768637 -8.212052 M1 60.587987 -1430.118911 -20.666167 Material Field 1822.997128 -1096.312645 -18.409534

[0320] Figure 8 Table 1

[0321]

[0322]

[0323]

[0324]

[0325]

[0326]

[0327] Figure 8 Table 2

[0328] Fig. 9 and Fig.10 A further embodiment of the projection optical unit or imaging optical unit 36 ​​is shown, which can replace the Figure 1 The projection optical unit 10 of the specific embodiment is used in the projection exposure device 1. Figures 1 to 8 , especially in combination Figures 2 to 8 Components and functions corresponding to those explained are denoted by the same reference numerals and will not be discussed again in detail.

[0329] 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 grazing incidence mirrors, that is to say, mirrors on which the imaging light 16 is incident at an angle of incidence greater than 45°. These grazing incidence mirrors are also referred to as GI (grazing incidence) mirrors.

[0330] The deflection effects of the four GI mirrors M2 , M3 , M4 and M5 are added for the imaging light 16 .

[0331] Firstly the imaging beam path portion between the mirrors M5 and M6 and secondly the imaging beam path portion between the mirror M7 and the image field 11 intersect in the intersection region 37 .

[0332] In the meridional yz beam path of the imaging light 16, the y intermediate image 38 is located between the GI mirrors M4 and M5. In a plane perpendicular thereto (see Fig.10 ), the x intermediate field 39 is located in the xz beam path of the imaging light 16 between the GI mirror M5 and the NI mirror M6.

[0333] The image-side numerical aperture of the projection optical unit 36 ​​is 0.33.

[0334] The average wavefront aberration RMS in the projection optical unit 36 ​​is 8.57 mλ.

[0335] The x position of the entrance pupil of the projection optical unit 36 ​​is located more than 2700 mm downstream of the object field 5 in the imaging beam path. The y position of the entrance pupil of the projection optical unit 36 ​​is located more than approximately 1600 mm upstream of the object field 5 in the imaging beam path. There is also a well-approximated object-side telecentricity in the projection optical unit 36. The total transmission in the projection optical unit 36 ​​is 11.1%.

[0336] 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 does not exceed approximately 1.8°.

[0337] The chief ray angle CRA of the projection optical unit 36 ​​is 5.05°.

[0338] The object plane 6 is parallel to the image plane 12. The z distance between the object plane and the image plane is about 2.1 m.

[0339] In the projection optical unit 36, the object-image offset is about 3.4 m.

[0340] In the projection optical unit 36, the installation space requirement in the x, y and z directions is approximately 1140 mm x 3950 mm x 1920 mm.

[0341] In the projection optical unit 36, the working distance between the mirror closest to the wafer and the image field 11 is approximately 65 mm.

[0342] The projection optical unit 36 ​​has no pupil masking. The reflecting surfaces of all mirrors M1 to M6 are used continuously without interruptions or passage openings.

[0343] The imaging ratio β of the projection optical unit 36 x , βy In the x direction, this is +0.25, or a reduction of 4.00, and in the y direction, -0.25, which is caused by the odd number of mirrors as a whole and the intermediate images in the x and y directions, respectively.

[0344] The image field 11 of the projection optical unit 36 ​​is rectangular and has an extent of 26.0 mm in the x-direction and an extent of 2.5 mm in the y-direction.

[0345] The diameter of the reflector M6 is slightly less than 1150 mm. The maximum y / x aspect ratio of the reflective surface area is at the reflector M6 in the projection optical unit 36 ​​and is approximately 1.56 there. The maximum x / y aspect ratio of the reflective surface area is at the reflector M4 in the projection optical unit 36 ​​and is approximately 2.76.

[0346] The following are the surface area parameters of the optical design associated with the projection optical unit 36:

[0347] Wavelength used 13.5nm Image side numerical aperture 0.33 <![CDATA[Imaging ratio β x > 4.00 <![CDATA[Imaging ratio β y > -4.00 Chief Ray Angle CRA 5.05° Etendue <![CDATA[7.08mm 2 ]]> Average wavefront aberration RMS 8.57mλ Total transmission rate 11.12％ Entrance pupil position (x) 2914.91mm Entrance pupil position (y) -1560.59mm Object Image Offset 3359.91mm Working distance (M3 to image field) 65mm z distance between object field and image field 2156.00mm The angle between the object plane and the image plane 0.0° Installation space requirement xyz (1138x 3950x 1916)mm

[0348] Fig. 9 Table 1

[0349]

[0350] Fig. 9 Table 2

[0351] according to Fig. 9 and Fig.10 The optical design data of the projection optical unit 36 ​​are listed in the following table, and its format is the same as that of the previous description according to Figure 2 The format is the same as explained in the specific embodiment.

[0352]

[0353]

[0354] Fig. 9 Table 3

[0355]

[0356]

[0357]

[0358]

[0359]

[0360]

[0361]

[0362]

[0363]

[0364]

[0365]

[0366]

[0367]

[0368]

[0369]

[0370]

[0371]

[0372]

[0373] Fig. 9 Table 4

[0374] As is evident from the signs of the radii of curvature in the above table, the reflectors M2, M4 and M5 have saddle-shaped surfaces.

[0375] In principle, other combinations of NI and GI mirror sequences are also conceivable. In particular, the number of mirrors in a series of GI mirrors can be varied between three and five without causing the transmission to vary too much, since the GI mirrors are illuminated at grazing incidence (if the number is increased) and therefore each individual mirror has a high transmission.

[0376] The above-described projection optical unit does not have a polarization rotation of the linearly polarized imaging light 16 of more than 10° in the imaging beam path between the object field 5 and the image field 11. In fact, in the above-described specific embodiments of the projection optical unit, this polarization rotation is less than 10°, less than 7°, less than 6°, less than 5° and also less than 4.5°.

[0377] In order to produce a microstructured or nanostructured component, the projection exposure apparatus 1 is used as follows: First, a reflective mask 10 or reticle and a substrate or wafer 11 are provided. Next, with the aid of the projection exposure apparatus 1, the structure on the reticle 10 is projected onto the photosensitive layer of the wafer 11. Then, by developing the photosensitive layer, a microstructure or nanostructure is produced on the wafer 11, and thus a microstructured component is produced.

Claims

1. An imaging EUV optical unit (10, 24, 27, 28, 29, 32, 33, 35, 36) for imaging an object field (5) into an image field (11), - having a plurality of mirrors (M1 to M4; M1 to M7; M1 to M6; M1-M8) for directing EUV imaging light (16) having a wavelength shorter than 30 nm from the object field (5) along an imaging beam path towards the image field (11), -in, The EUV optical unit (10, 24, 27, 28, 29, 32, 33, 35, 36) comprises at least three NI mirrors (M1 to M4; M1, M6, M7; M1, M5, M6; M1, M7, M8), - wherein the total transmission rate of the NI reflectors (M1 to M4; M1 to M7; M1 to M6; M1 to M8) is greater than 10%, - wherein when linearly polarized EUV imaging light (16) is used, the total number of mirrors (M1 to M4) results in an overall polarization rotation along the imaging beam path of no more than 10°.

2. The imaging EUV optical unit according to claim 1, characterized in that Exactly 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) only includes NI mirrors (M1 to M4).

4. The imaging EUV optical unit according to claim 2 or 3, characterized in that: A first imaging of the object field (5) in the imaging beam path takes place in the image field (11).

5. The imaging EUV optical unit according to any one of claims 1 to 4, characterized in that: At least one of the reflectors (M1 to M4; M1 to M6 / M7 / M8) has a saddle-shaped reflective surface.

6. The imaging EUV optical unit according to any one of claims 1 to 5, characterized in that: At least one of the reflectors (M2; M1; M1, M2; M2, M3) has a reflective surface whose aspect ratio (x / y) between a larger surface extent along a first reflective surface dimension (x) and a smaller surface extent along a second reflective surface dimension (y) perpendicular to the first reflective surface dimension is greater than 1.

5.

7. The imaging EUV optical unit according to any one of claims 1 to 6, characterized in that A ring field image field.

8. The imaging EUV optical unit according to any one of claims 1 to 7, characterized in that: Two imaging beam path portions span an intersection region (34; 37), the two imaging beam path portions in each case between the object field (5) and the first mirror (M1) in the imaging beam path, - in each case between two consecutive reflectors (M2, M3; M4, M5), or - between the last mirror (M6) in the imaging beam path and the image field (11).

9. The imaging EUV optical unit according to claim 8, characterized in that: The two intersecting imaging beam path portions are: the imaging beam path portion between the object field (5) and the first mirror (M1) in the imaging beam path; and - the portion of the imaging beam path between the second mirror (M2) in the imaging beam path and the third mirror (M3) in the imaging beam path.

10. The imaging EUV optical unit according to any one of claims 1 to 9, characterized in that An incident light bulb is arranged in the imaging beam path upstream of the object field (5).

11. The imaging EUV optical unit according to any one of claims 1 to 10, characterized in that: At least one of the mirrors (M3, M4) has a passage opening (30, 31) for the passage of the imaging beam path.

12. An optical system, - having an illumination optical unit (4) for illuminating the object field (5) with the imaging light (16); - having an imaging EUV optical unit (10, 24, 27, 28, 29, 32, 33, 35, 36) as claimed in any one of claims 1 to 11.

13. A projection exposure apparatus having an optical system as claimed in claim 12 and having an EUV light source (3).

14. A method for producing a structured component, the method comprising the following method steps: - providing a mask (7) and a wafer (13); - using the projection exposure apparatus according to claim 13, projecting the structure on the mask (7) onto the photosensitive layer of the wafer (13); - Producing microstructures and / or nanostructures on the wafer (13).

15. A structured component produced by the method of claim 14.

Images