Imaging EUV optical unit for imaging object field to image field

Abstract

An imaging EUV optical unit (10) for imaging an object field (5) to an image field (11). The optical unit has a plurality of mirrors (M1 to M6) for guiding EUV imaging light (16) having a wavelength shorter than 30 nm from the object field (5) to the image field (11) along an imaging beam path. The plurality of mirrors includes at least two NI mirrors (M5, M6) and at least two GI mirrors (M1 to M4). The total transmission rate of the plurality of mirrors (M1 to M6) is greater than 10%. This results in an imaging EUV optical unit that can improve the availability of the EUV projection exposure device.

Description

[0001] This patent application claims the priority of German patent application No. DE 10 2022 206 110.1, 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. The invention also relates to an optical system having such an imaging optical unit, a projection exposure apparatus having 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] Projection optical units of the type mentioned at the outset are known from WO 2018 / 010 960 A1, DE 10 2015 209 827 A1, DE 10 2012 212 753 A1, US 2010 / 0149509 A1 and US 4,964,706. F. Scholze et al., in the professional document “Polarization dependence of multilayer reflectance in the EUV spectral range” in Proc. of SPIE, Vol. 6151 615137-1 to -8, disclose reflection data measured by an EUV reflectometer. DE 10 2011 075 579 A1 discloses a reflector and a microlithography projection exposure device having the reflector. DE 10 2015 226 529 A1 discloses an imaging optical unit for imaging an object field into an image field, and a projection exposure apparatus having such an imaging optical unit. Summary of the invention

[0004] It is an object of the invention to develop an imaging EUV optical unit of the type stated at the outset in such a way that its usability for EUV projection exposure installations is improved.

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

[0006] According to the present invention, it was realized that the use of at least two NI mirrors and at least two GI mirrors within an imaging EUV optical unit allows a design with a surprisingly high overall transmission of more than 10%. For a given source power used for EUV, an overall transmission of more than 10% allows an increase in the EUV throughput to the image field, thereby increasing the exposure power. Alternatively, for a given required exposure power on the image field, a reduced power supply can be used.

[0007] The imaging EUV optical unit may comprise at least four GI mirrors.

[0008] The overall or total transmission of the imaging EUV optical unit may be greater than 11%, greater than 12%, greater than 13%, greater than 14%, and also greater than 15%. The total transmission of the imaging EUV optical unit may be at least 11.8%. Due to the number of mirrors and the individual transmission of the imaging light guide mirrors, which typically do not exceed 80%, the total transmission is typically less than 20%.

[0009] The imaging EUV optical unit may have an image side numerical aperture of less than 0.5 and in particular less than 0.4. The image side numerical aperture may be greater than 0.25, and may be greater than 0.3.

[0010] The average wavefront aberration RMS may be less than 200 mλ (λ: wavelength of light used), may be less than 100 mλ, and may also be less than 50 mλ. The wavefront aberration RMS is usually greater than 5 mλ.

[0011] The object field of the imaging EUV optical unit may lie in an object plane. The image field of the imaging EUV optical unit may lie in an image plane. The object plane may extend parallel to the image plane. The object plane may extend at an angle different from 0° relative to the image plane.

[0012] The embodiment as claimed in claim 2 in particular allows the use of a last mirror upstream of the image field which, by virtue of the relatively small angle of incidence present there and by virtue of its mirror size, specifies the largest possible image-side numerical aperture.

[0013] The number of NI-GI mirrors as claimed in claims 3 and 4 was found to be an advantageous combination of high overall transmission and good imaging quality.

[0014] It was found that the mirror pairs according to claim 5 can complement each other well with respect to their beam shaping effect. In particular, the imaging EUV optical unit can comprise two such GI mirror pairs, whose deflection effects cancel each other out, so that the deflection effect of the second GI mirror pair has a subtractive effect relative to the deflection effect of the first GI mirror pair. The result that can be achieved overall is that the total deflection effect of the NI mirrors on the imaging light is relatively small, so that designs with a small angle between the object plane and the image plane and designs in which the object plane preferably extends parallel to the image plane are still feasible.

[0015] The embodiment with the crossover region as claimed in claim 6 allows the angle of incidence distribution on the mirror of the imaging EUV optical unit to be reflectivity optimized, in particular with respect to the absolute angle of incidence on the mirror surface and / or with respect to the smallest possible angle of incidence bandwidth on the mirror. This embodiment ensures in particular a highly reflective coating of the mirror. Alternatively, this crossover region may not be present in the case of an imaging EUV optical unit.

[0016] This applies in particular to the configuration of crossed imaging beam path sections as claimed in claim 7, which allows small angles of incidence on the penultimate NI mirror.

[0017] The entrance pupil as claimed in claim 8 allows the use of an illumination optical unit in the imaging light beam path upstream of the object field, in which case the mirror of the illumination optical unit arranged in the entrance pupil is the last EUV light guide mirror upstream of the object field. This eliminates reflectivity losses due to the insertion of a transfer optical unit which is otherwise required.

[0018] The advantages of the optical system according to claim 9 or 10, of the projection exposure apparatus according to claim 11, of the production method according to claim 12 and of the microstructure or nanostructure according to claim 13 correspond to the advantages already explained above with reference to the projection unit according to the invention. In the optical system according to claim 10, alternative illumination light incouplings are possible, which can meet corresponding installation space requirements. The EUV light source of the projection exposure apparatus can be embodied in such a way that, for example, the used wavelength does not exceed 13.5 nm, is less than 13.5 nm, is less than 10 nm, is less than 8 nm, is less than 7 nm and can be 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.

[0019] In particular, projection exposure apparatuses can be used to produce semiconductor components, such as memory chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] At least one exemplary embodiment of the present invention is described below based on the diagrams. In the diagrams:

[0021] Figure 1 A meridional cross section of a projection exposure apparatus for EUV projection lithography is shown diagrammatically;

[0022] Figures 2 to 7 In each case the meridian section is shown as a basis Figure 1 A specific embodiment of an imaging optical unit of a projection lens in a projection exposure device in which the imaging beam paths of the main rays and the upper coma rays and the lower coma rays of three selected field points are depicted. DETAILED DESCRIPTION

[0023] In the following, we first discuss Figure 1 The example of FIG. 1 is used to describe the basic components of the microlithography projection exposure apparatus 1. The description of the basic structure of the projection exposure apparatus 1 and its components should not be limited thereto.

[0024] The embodiment of the illumination system 2 of the projection exposure apparatus 1 comprises 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 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 comprise the light source 3.

[0025] The mask 7 arranged in the object field 5 is exposed. The mask 7 is held by a mask carrier 8. The mask carrier 8 can be displaced by a mask shift drive 9, in particular in the scanning direction.

[0026] For ease of explanation, Figure 1 Displays a Cartesian xyz coordinate system. The x direction is perpendicular to the drawing plane and runs into the latter. The y direction runs horizontally, and the z direction runs vertically. The scanning direction runs along Figure 1 The z direction is perpendicular to the object plane 6.

[0027] The projection exposure device 1 comprises a projection optical unit or imaging optical unit 10. The projection optical unit 10 is used to image 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°.

[0028] The structures on the mask 7 are imaged onto the photosensitive layer of a wafer 13, wherein the wafer is arranged in the region of the image field 11 in the image plane 12. The wafer 13 is held by a wafer carrier 14. The wafer carrier can be displaced, in particular in the y direction, by a wafer displacement drive 15. The displacement of the mask 7 by the mask displacement drive 9 on the one hand and the displacement of the wafer 13 by the wafer displacement drive 15 on the other hand can occur in a synchronous manner with each other.

[0029] The radiation source 3 is an EUV radiation source. The radiation source 3 emits in particular EUV radiation 16, which is also referred to below as use radiation or illumination radiation. In particular, the use radiation has a wavelength in the range between 5 nm and 30 nm. The radiation source 3 may be a plasma source, such as a laser produced plasma (LPP) source or a gas discharge produced plasma (GDPP) source. It may also be a synchrotron-based radiation source. The radiation source 3 may be a free electron laser (FEL).

[0030] The illumination radiation 16 emitted from the radiation source 3 is focused by a collector 17. The collector 17 may be a collector having one or more elliptical and / or hyperbolic reflective surfaces. The illumination radiation 16 may be incident on at least one reflective surface of the collector 17 at grazing incidence (GI), i.e. at an angle of incidence greater than 45°, or at normal incidence (NI), i.e. at an angle of incidence less than 45°. The collector 17 may be structured and / or coated, firstly, to optimize its reflectivity for the radiation used and, secondly, to suppress stray light.

[0031] Downstream of the light collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 may represent a separation between the radiation source module containing the radiation source 3 and the light collector 17 and the illumination optics unit 4.

[0032] The illumination optical unit 4 comprises a first facet mirror 19. If the first facet mirror 19 is arranged in a plane of the illumination optical unit 4 optically conjugate to the object plane 6, this facet mirror is also called a field facet mirror. The first facet mirror 19 comprises a plurality of individual first facets 20, which are also referred to below as field facets. Figure 1 Only some of these facets are illustrated in an exemplary manner.

[0033] The first facet 20 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 20 can be embodied as a plane facet, or alternatively as a facet with a convex or concave curvature.

[0034] For example, it is known from DE 10 2008 009 600 A1 that the first facet 20 itself can also be composed in each case of multiple individual mirrors, in particular multiple micromirrors. The first facet mirror 19 can be formed in particular as a microelectromechanical system (MEMS system). For more details, please refer to DE 10 2008 009600 A1.

[0035] A deflection mirror US, which can be embodied as a plane mirror but can alternatively also have a beam-shaping effect, is located in the beam path of the illumination optical unit 4 between the intermediate focus in the intermediate focal plane 18 and the first facet mirror 19 .

[0036] In the beam path of the illumination optical unit 4, the second facet mirror 21 is arranged downstream of the first facet mirror 19. If the second facet mirror 21 is arranged in the pupil plane of the illumination optical unit 4, it is also called a pupil facet mirror. The second facet mirror 21 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 19 and the second facet mirror 21 is also called a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1, EP 1614 008 B1 and US 6,573,978.

[0037] The second facet mirror 21 comprises a plurality of second facets 22. In the case of a pupil facet mirror, the second facets 22 are also referred to as pupil facets.

[0038] The second facets 22 can likewise be macroscopic facets, which can have, for example, circular, rectangular or hexagonal boundaries, or alternatively facets consisting of micromirrors. In this regard, reference is likewise made to DE 10 2008 009 600 A1.

[0039] The second facet 22 may have a planar reflective surface or alternatively may have a convex or concave curved reflective surface.

[0040] 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).

[0041] It may be advantageous to configure the second facet mirror 21 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.

[0042] With the aid of the second facet mirror 21 and optionally with the aid of an imaging optical assembly in the form of a transfer optical unit ( Figure 1 ), the individual first facets 20 are imaged into the object field 5 .

[0043] The transfer optical unit can contain exactly one mirror, but alternatively can also contain 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 contain one or two normal incidence mirrors (NI mirrors) and / or one or two grazing incidence mirrors (GI mirrors). Figure 1 In the specific embodiment shown, the illumination optical unit 4 has exactly three mirrors, namely downstream of the light collector 17 , specifically a deflection mirror US, a first facet mirror 19 and a second facet mirror 21 .

[0044] Insofar as the transfer optics downstream of the second facet mirror 21 are omitted, the second facet mirror 21 is the last beam shaping mirror or, in fact, the last reflector of the illumination radiation 16 in the beam path upstream of the object field 5. Figure 2 An example of an illumination optical unit 4 without a transfer optical unit is disclosed in .

[0045] The imaging of the first facet 20 into the object plane 6 by the second facet 22 or using the second facet 22 and the transfer optics is usually only an approximate imaging.

[0046] The projection optical unit 10 comprises a plurality of reflectors Mi, namely six reflectors M1 to M6 (see Figure 2 ), which are numbered consecutively according to their order in the beam path of the projection exposure apparatus 1 .

[0047] exist Figure 1 In the example shown, the projection optical unit 10 comprises six mirrors M1 to M6. Alternative solutions with four, five or any other number of mirrors Mi are also possible.

[0048] The projection exposure unit 10 is a naked optical unit. The mirrors M1 to M6 comprise no passage openings for the illumination radiation 16 .

[0049] The image side numerical aperture of the projection optical unit 10 is 0.33. According to a specific embodiment of the projection optical unit 10, the image side numerical aperture may be in a range between 0.25 and 0.4, for example. According to a specific embodiment, the image side numerical aperture of the projection optical unit 10 may also adopt different values.

[0050] The reflective surface of the reflector Mi is 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, for example with alternating molybdenum and silicon layers. Ruthenium coatings are also possible, in particular for coating grazing incidence reflectors (GI reflectors).

[0051] The projection optical unit 10 causes a reduction in size along the x direction (i.e., a direction perpendicular to the scanning direction y) by a ratio of 4:1. In addition, the projection optical unit 10 causes an image inversion along this x direction. Thus, along the x direction, the imaging ratio β x is -4.00.

[0052] In the scanning direction y, the projection optical unit 10 again leads to a size reduction of 4:1, but in this case (β y = +4.00) with no image reversal.

[0053] In an alternative embodiment, the projection optical unit 10 can also have a deformed design. In this case, it has different imaging ratios β in the x and y directions. x , β y The two imaging ratios β of the projection optical unit 7 x ,β y Preferably (β x ,β y )=(+ / -4,+ / -8).

[0054] Other imaging ratios are also possible. Imaging ratios with the same sign are also possible in the x and y directions.

[0055] The image field 11 has an x ​​extent of 26 mm and a y extent of 2.5 mm.

[0056] The image field may have a partially annular embodiment.

[0057] Alternatively, the image field can also have a rectangular embodiment.

[0058] The number of intermediate image planes in the x-direction and the y-direction in the beam path between the object field 5 and the image field 11 is different in the case of the projection optical unit 10. In the yz plane, the projection optical unit 10 has an intermediate image in the intermediate image plane 24 between the mirrors M3 and M4, as shown in accordance with Figure 2 The meridional section is shown in Figure 1. x =-4.00 in the imaging direction perpendicular thereto, the projection optical unit 10 has no intermediate image. From US2018 / 0074303 A1, examples of projection optical units with different numbers of such intermediate images along the x-direction and the y-direction are known. Alternatively, the projection optical unit 10 can also be designed to have no intermediate image or to have the same number of intermediate images along the x- and y-directions.

[0059] In each case, one of the plurality of pupil facets 22 is assigned to exactly one of the plurality of field facets 20 for forming in each case an illumination channel for illuminating the object field 5. In particular, this can be done according to The far field is decomposed into multiple object fields 5 with the aid of the field facets 20. The field facets 20 generate multiple intermediate focus images on the pupil facets 22 respectively assigned thereto.

[0060] The field facets 20 are imaged onto the reticle 7 via the assigned pupil facets 22 in each case in such a way that they overlap one another for the purpose of 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 superimposing different illumination channels.

[0061] 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 that guide the light. This intensity distribution is also called illumination setting or illumination pupil filling.

[0062] 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 .

[0063] 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.

[0064] The projection optical unit 10 can in particular have a concentric entrance pupil. It can be accessible, as in Figure 2 A specific embodiment of the projection optical unit 10.

[0065] The projection optical unit 10 has an entrance pupil EP (see Figure 1 ), which is located in the range between 1500 mm and 2000 mm, and in particular in the range between 1800 mm and 2200 mm, upstream of the object field 5 in the beam path both in the x-direction and in the y-direction. Figure 1 The configuration plane of this entrance pupil is depicted at EP in FIG. Therefore, if the pupil facet mirror 21 is arranged about 2 m upstream of the object field 5 in the beam path of the illumination or imaging light 16, the pupil facet mirror 21 meets the positioning condition of being “arranged in the region of the entrance pupil of the projection optical unit”.

[0066] In the case of an alternative embodiment of the projection optical unit 10 , the entrance pupil can also be inaccessible, so that the configuration plane of the pupil facet mirror 21 is imaged into the entrance pupil by means of further components of the illumination optical unit 4 .

[0067] The entrance pupil of the projection optical unit 10 cannot usually be accurately illuminated using the pupil facet mirror 21. When imaging the projection optical unit 10, which telecentrically images the center of the pupil facet mirror 21 onto the wafer 13, the aperture rays usually do not intersect at a single point. However, a region can be found in which the separation 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.

[0068] The entrance pupil positions can also be different for the tangential beam path and the sagittal beam path of the projection optical unit 10. 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 21 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.

[0069] exist Figure 1 In the component configuration of the illumination optical unit 4 shown, the pupil facet mirror 21 is configured tilted relative to the object plane 5. The second facet mirror 21 is further configured tilted relative to the configuration plane defined by the first facet mirror 19.

[0070] The following will be based on Figure 2 Further details regarding the projection optical unit 10 are described.

[0071] The projection optical unit 10 has two NI mirrors (mirrors for normal incidence; normal incidence mirrors), i.e., the last two mirrors M5 and M6 in the imaging optical path of the projection optical unit 10. The imaging light 16 is irradiated on the two NI mirrors M5, M6 at an incident angle of less than 45°. The maximum incident angle of the imaging light 16 incident on the corresponding NI mirrors may be less than 40°, less than 35°, less than 30°, less than 25°, less than 20°, less than 15°, or less than 10°.

[0072] The other mirrors M1 to M4 of the projection optical unit 10 are GI mirrors (mirrors for grazing incidence, grazing incidence mirrors). For these mirrors M1 to M4, the angle of incidence of the illumination light 16 on the mirror is in each case greater than 45°. The minimum angle of incidence on the respective GI mirror may be greater than 50°, greater than 55°, greater than 60°, greater than 65°, greater than 70°, greater than 75° and further greater than 80°.

[0073] Information on reflection at GI mirrors (grazing incidence mirrors) can be found in WO 2012 / 126867 A. Further information on the reflectivity of NI mirrors (normal incidence mirrors) can be found in DE 101 55 711A.

[0074] The mirrors M1 to M6 have no passage openings and are used in a reflecting manner in each case in a continuous area without gaps.

[0075] Figure 2 Calculated reflection surfaces of the mirrors M1 to M6 are illustrated. The used reflection surfaces of the mirrors M1 to M6 are carried in a known manner by a mirror body (not shown).

[0076] The total transmission rate of the projection optical unit 10 is based on Figure 2 The total transmission has a value of 15.12% in the projection optical unit 10, which is presented as the product of the reflectivities of the mirrors M1 to M6 for the illumination light 16 along the imaging beam path through the projection optical unit 10. On average, each individual mirror of the mirrors M1 to M6 therefore has a reflectivity of 73%.

[0077] The first two mirrors M1, M2 in the imaging beam path of the projection optical unit 10 are a pair of consecutive GI mirrors, which are additive in terms of their deflection effect. Therefore, the two subsequent mirrors M3 and M4 in the imaging beam path of the projection optical unit 10 are a pair of consecutive GI mirrors, which are additive in terms of their deflection effect. The two pairs M1, M2 (on the one hand) and M3, M4 (on the other hand) have deflection effects that are opposite in meaning to each other. That is, the deflection effect of the second GI mirror pair M3, M4 has a subtractive effect relative to the deflection effect of the first GI mirror pair M1, M2.

[0078] In the yz plane, a first pupil plane of the projection optical unit 10 is located in the beam path of the imaging light between the mirrors M2 and M3. The second pupil plane in the yz plane is located at the same position as the pupil plane in the xz plane perpendicular thereto, at a position in the imaging beam path adjacent to the reflection of the imaging light 16 at the mirror M6. In the case of the projection optical unit 10, the aperture can be limited by an aperture stop, which in particular limits the imaging beam path at the edge side and can be attached to the mirror M6. If necessary, an internal shielding can also be defined on the mirror M6 by means of a suitable stop section.

[0079] In the case of the projection optical unit 10 , the y-offset between the central field point of the object field 5 and the central field point of the image field 11 is approximately 3570 mm.

[0080] The z distance between the mirror M5 and the image field 11 is 140 mm.

[0081] The distance between the object field 5 and the image field 11 is 2600 mm in the direction perpendicular to the object field.

[0082] The object plane 6 and the image plane 12 extend parallel to each other.

[0083] The entire projection optical unit 10 can be adapted to a cuboid with side lengths of 860 mm, 4011 mm and 1993 mm in xyz.

[0084] The imaging beam path of the projection optical unit 10 includes an intersection region 25, in which two imaging beam path portions of the imaging beam path intersect. The first of these intersecting imaging beam path portions is the one between the reflectors M4 and M5. The second of these intersecting imaging beam path portions is the portion between the reflector M6 and the image field 11.

[0085] The mirrors M1 to M6 have a coating which optimizes the reflectivity of the mirrors M1 to M6 for the imaging light 16. In particular for the GI mirrors this can be a lanthanum coating, a boron coating or a boron coating with an uppermost layer of lanthanum, or a ruthenium coating. Other coating materials can also be used, in particular lanthanum nitride and / or B 4 C. In the mirrors M1 to M4 for grazing incidence, for example, a coating having a layer of boron or lanthanum can be used. The highly reflective layers, in particular the highly reflective layers of the mirrors M5 and M6 for normal incidence, can be constructed 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 bilayers, each made of a layer of boron and a layer of lanthanum. Alternatively, a coating containing lanthanum nitride and / or boron, in particular B can be used. 4 C layer.

[0086] Table 1 below summarizes the parameters of the projection optical unit 10. In addition to the data already explained above, Table 1 specifies the angle of the chief ray of the central field point relative to the z-axis (5.20°), the available etendue of the projection optical unit and the value of the average wavefront aberration RS.

[0087]

[0088] Figure 2 Table 1

[0089] Tables 2a, 2b below summarize the parameters "maximum angle of incidence", "extent of the reflecting surface in the x-direction", "extent of the reflecting surface in the y-direction" and "maximum mirror diameter" of the mirrors M1 to M6 of the projection optical unit 10.

[0090] M1 M2 M3 Maximum incident angle [°] 73.6 67.9 79.3 Minimum incident angle [°] 67.0 66.6 73.5 Extent of the reflective surface along the x-direction [mm] 240.6 347.5 552.9 Extent of the reflective surface along the y direction [mm] 350.4 415.8 244.8 Maximum reflector diameter [mm] 374.1 440.6 557.3

[0091] Figure 2 Table 2a

[0092] M4 M5 M6 Maximum incident angle [°] 83.5 27.3 5.6 Minimum incident angle [°] 75.6 6.3 2.9 Extent of the reflective surface along the x-direction [mm] 485.8 291.5 859.9 Extent of the reflective surface along the y direction [mm] 535.8 237.7 859.9 Maximum reflector diameter [mm] 549.1 291.6 860.8

[0093] Figure 2 Table 2b

[0094] For the four GI mirrors M1 to M4, the minimum angle of incidence of the imaging light 16 is 66.6° and the maximum angle of incidence is 83.5°. For the two NI mirrors M5, M6, the minimum angle of incidence is 2.9° and the maximum angle of incidence is 27.3°. The maximum angle of incidence at the last mirror M6 is less than 10° and in particular less than 6°.

[0095] The minimum incident angle at the last two GI reflectors M3, M4 is greater than 70°, even greater than 73°. The minimum incident angle at the last GI reflector M4 is greater than 75°.

[0096] The reflector with the smallest reflective surface range in the x-direction is reflector M1, which has a range of less than 250 mm. The reflector with the smallest reflective surface range in the y-direction is reflector M5, which has a range of less than 240 mm. The y-ranges of reflectors M3 and M5 are less than 250 mm. All reflectors M1 to M6 have an x / y reflective surface range of more than 200 mm.

[0097] The largest reflector is the M6 ​​reflector which is almost circular with a diameter of 860 mm.

[0098] The reflectors M1 to M6 are embodied as free-form surfaces which cannot be described by rotationally symmetric functions. Other embodiments of the projection optical unit 10 are also possible, in which at least one of the reflectors M1 to M6 is embodied as a rotationally symmetric aspheric surface. All reflectors M1 to M6 can also be embodied as such as aspheric surfaces.

[0099] A free-form surface can be described by the following free-form surface equation (Equation 1):

[0100]

[0101] The following apply to the parameters of this equation (1):

[0102] 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 (x=0; y=0).

[0103] In the free-form surface equation (1), C 1 , C 2 , C 3 …represent the coefficients of the series expansion of the free-form surface expressed as powers of x,y.

[0104] In the case of a conical base, c x 、c y is a constant corresponding to the vertex curvature of the corresponding asphere. Therefore, cx =1 / R x (1 / RDX) and c y =1 / R y (1 / RDY). k x and k y (CCX,CCY) each corresponds to the conic constant of the corresponding aspheric surface. Therefore, equation (1) describes a biconical free-form surface.

[0105] An alternative possible free-form curvature can be generated from a rotationally symmetric reference surface. Such a free-form curvature of a reflective surface of a mirror of a projection optical unit for a microlithographic projection exposure apparatus is known from US 2007 0 058 269 A1.

[0106] Alternatively, free-form surfaces can also be described by means of two-dimensional spline surfaces. Examples of this are, for example, 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 interpolation between the grid points using, for example, polynomials or functions with specific properties in terms of their continuity and differentiability. Examples of this are analytical functions.

[0107] The optical design data of the reflective surfaces of the mirrors M1 to M6 of the projection optical unit 10 can be collected from the following further lists.

[0108] Table 3 specifies the surface origins of the corresponding mirror surfaces and the coordinates of the regions of the object field 5 relative to the xyz coordinate system of the image field 11 .

[0109] The first column specifies the distance of the respective mirror or object field 5 from the central coordinate origin of the image field 11 in the y direction (first column) and in the z direction (second column).

[0110] The additional columns of Table 3 additionally specify the tilt values ​​of the respective surfaces of the mirrors M1 to M6 or the object field 5 relative to the x-axis, the y-axis and the z-axis. 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.

[0111] Table 4 lists the parameters RDX, RDY, CCX, CCY of the reflectors M1 to M6, respectively, and the values ​​of the coefficients C1, C2, C3, ... of the series expansion of the free-form surface obtained according to the above equation (1) in order of the powers of x and y.

[0112] Table 5 lists the reflectivities of the mirrors M1 to M6 and the total transmission or overall transmission of the projection optical unit 10 , which is 15.4584%.

[0113] Table 6 lists data on the opening of the aperture stop AS of the projection optical unit 10 arranged in the region of the mirror M6. This aperture opening is defined by a polygon, whose x and y values ​​are specified in Table 6.

[0114] Mirrors with different signs in their RDX and RDY values ​​have a saddle point or minimax basic shape.

[0115] y distance [mm] z distance [mm] Tilt around x-axis [degrees] Material Field 3567.908119 2600.104852 -0.000000 M1 3513.528571 2002.574213 65.101421 M2 2915.894055 1396.476224 202.479826 M3 1393.145977 1408.255078 13.144114 M4 495.301563 956.069380 37.339438 M5 -186.764134 199.954174 -25.871920 M6 0.000000 1293.569087 -4.845651 Aperture (AS) -186.764134 199.954174 -9.691301 Image Field 0.000000 0.000000 -0.000000

[0116] Figure 2 Table 3a

[0117] y distance [mm] Tilt around the y axis [degrees] Tilt around z axis [degrees] Material Field 3567.908119 0.00 -0.00 M1 3513.528571 180.00 0.00 M2 2915.894055 0.00 -0.00 M3 1393.145977 0.00 180.00 M4 495.301563 0.00 -0.00 M5 -186.764134 180.00 0.00 M6 0.000000 0.00 -0.00 Aperture (AS) -186.764134 180.00 0.00 Image Field 0.000000 0.00 -0.00

[0118] Figure 2 Table 3b

[0119]

[0120]

[0121]

[0122]

[0123]

[0124]

[0125]

[0126]

[0127]

[0128]

[0129]

[0130]

[0131] Figure 2 Table 4

[0132] Reflector Reflectivity M6 0.676098 M5 0.651536 M4 0.848054 M3 0.801719 M2 0.706179 M1 0.730898 Total transmission rate 0.154584

[0133] Figure 2 Table 5

[0134]

[0135]

[0136] Figure 2 Table 6

[0137] Figure 3 Another embodiment of the projection optical unit or imaging optical unit 27 is shown, which can replace the Figure 2 The projection optical unit 10 of the specific embodiment is used in the projection exposure device 1. Figure 1 and Figure 2 , especially in combination Figure 2 Components and functions corresponding to those explained are denoted by the same reference numerals and will not be discussed again in detail.

[0138] Starting from the object field 5, the beam path of the projection optical unit 27 initially passes through three GI mirrors M1, M2 and M3, which add up their deflection effects and result in an overall deflection effect of slightly more than 90° for the imaging light 16. Further along the beam path, the imaging light 16 is reflected at three further GI mirrors M4, M5 and M6, whose deflection effects are opposite to the deflection effects of the mirrors M1 to M3 and which in turn add up their deflection effects. The overall deflection effect of the mirrors M4 to M6 is approximately 60°. The projection optical unit 27 therefore has a total of six GI mirrors.

[0139] Subsequently, the imaging light 16 is reflected at an NI mirror M7 and subsequently at a final NI mirror M8, which defines the image-side numerical aperture of the projection optical unit 27. None of the mirrors M1 to M8 comprises a passage opening for the imaging light 16.

[0140] The pupil plane available for the aperture stop AS is located in the beam path of the imaging light 16 between the mirrors M7 and M8.

[0141] Similarly as in the case of the projection optical unit 10, the penultimate mirror of the projection optical unit 27 (mirror M5 of the projection optical unit 10; mirror M7 of the projection optical unit 27) is located in the beam path of the imaging light 16, on the opposite side of the beam path portion between the last aperture limiting mirror (M6 / M8) and the image field 11 relative to the other mirrors of the projection optical units 10 and 27.

[0142] The following table summarizes the parameters and optical design of the projection optical unit 27. In terms of its structure, these tables are combined with the above Figure 2 The table already explained corresponds to the following.

[0143]

[0144]

[0145] Figure 3 Table 1

[0146]

[0147] Figure 3 Table 2a

[0148]

[0149] Figure 3 Table 2b

[0150]

[0151] Figure 3 Table 3a

[0152] y distance [mm] Tilt around the y axis [degrees] Tilt around z axis [degrees] Material Field 3800.003886 0.00 -0.00 M1 3632.805120 180.00 0.00 M2 2986.815842 0.00 -0.00 M3 2235.173063 180.00 0.00 M4 853.247408 -0.00 -0.00 M5 600.262003 0.00 180.00 M6 370.147843 0.00 -0.00 M7 -253.736945 180.00 0.00 M8 0.000000 0.00 -0.00 Aperture (AS) -146.582552 180.00 0.00 Image Field 0.000000 0.00 -0.00

[0153] Figure 3 Table 3b

[0154]

[0155]

[0156]

[0157]

[0158]

[0159]

[0160]

[0161]

[0162]

[0163]

[0164]

[0165]

[0166] Figure 3 Table 4

[0167]

[0168]

[0169] Figure 3 Table 5

[0170] Figure 4Another embodiment of the projection optical unit or imaging optical unit 28 is shown, which can replace the Figure 2 The projection optical unit 10 of the specific embodiment is used in the projection exposure device 1. Figures 1 to 3 , especially in combination Figure 2 and Figure 3 Components and functions corresponding to those explained are denoted by the same reference numerals and will not be discussed again in detail.

[0171] In the beam path of the imaging light 16 downstream of the object field 5, the projection optical unit 28 initially has three GI mirrors M1, M2, M3, which add up in terms of their deflection effect to produce an overall deflection effect of slightly more than 90°. This is followed by two additional GI mirrors M4 and M5 with deflection effects that are successively additive and opposite to the effects of the GI mirrors M1 to M3. The overall deflection effect of the GI mirrors M4 and M5 is approximately 75°. This is followed by two additional NI mirrors M6 and M7, whose basic configuration is comparable to the two penultimate mirrors of the above-described projection optical units 10 and 27. The projection optical unit 28 therefore has five GI mirrors M1 to M5 and two NI mirrors M6 and M7.

[0172] In the case of the projection optical unit 28, the chief ray CR starting from the central field point of the object field 5 extends relative to a normal N to this central field point of the object field 5 and initially relative to a plane (xN) formed by each normal N and an axis parallel to the x-axis, in a different half-space than the arrangement position of the mirror M2 and the mirror behind it, to Figure 4 To the right of the mid-normal line N.

[0173] This firstly leads to the last component 28b of the illumination optical unit 4 (at Figure 4 The illumination / imaging beam path portion 28a between the first two mirrors M1 and M2 of the projection optical unit 28 and the object field 5 is caused to cross in the intersection region 28d. Therefore, the illumination / imaging beam path portion 28a is between one of the last components of the illumination optical unit 4 (component 28b) and the object field 5, and the illumination / imaging beam path portion 28c between the object field 5 and one of the first components of the imaging optical unit 28 (the beam path portion between the mirrors M1 and M2) crosses in the intersection region 28d.

[0174] Additionally, the reflector M1 is located in another half of the space relative to the xN plane compared to the other reflector M2 and the reflector behind it.

[0175] The following table summarizes the parameters and optical design of the projection optical unit 28. In terms of its structure, these tables are combined with the above Figure 2 The table already explained corresponds to the following.

[0176]

[0177] Figure 4 Table 1

[0178]

[0179] Figure 4 Table 2a

[0180]

[0181] Figure 4 Table 2b

[0182] y distance [mm] z distance [mm] Tilt around x-axis [degrees] Material Field 2617.613579 2897.162348 0.000000 M1 2538.995709 2080.684552 246.834158 M2 2086.772773 1557.364578 34.360602 M3 1015.810934 1177.004195 185.384997 M4 670.383832 1230.373545 11.919326 M5 447.145957 1087.488653 46.011129 M6 -138.535923 97.126614 -17.756720 M7 0.000000 1708.401781 -2.457076 Aperture (AS) -78.335286 797.304506 -4.914152 Image Field 0.000000 0.000000 -0.000000

[0183] Figure 4 Table 3a

[0184]

[0185]

[0186] Figure 4 Table 3b

[0187]

[0188]

[0189]

[0190]

[0191]

[0192]

[0193]

[0194]

[0195]

[0196]

[0197]

[0198]

[0199]

[0200]

[0201]

[0202]

[0203]

[0204] Figure 4 Table 4

[0205] Reflector Reflectivity M7 0.677606 M6 0.662439 M5 0.804769 M4 0.722823 M3 0.792973 M2 0.783720 M1 0.749441 Total transmission rate 0.121614

[0206] Figure 4 Table 5

[0207]

[0208]

[0209]

[0210] Figure 4 Table 6

[0211] Figure 5 Another embodiment of the projection optical unit or imaging optical unit 29 is shown, which can replace the Figure 2 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 Components and functions corresponding to those explained are denoted by the same reference numerals and will not be discussed again in detail.

[0212] The basic structure of the projection optical unit 29, initially with five GI mirrors M1 to M5 and subsequently with two further NI mirrors M6 and M7, corresponds to Figure 4 The projection optical unit 29 has a significantly greater extent in the y direction than the projection optical unit 28, so that in particular the y distance between the mirrors M3 and M4 in the case of the projection optical unit 29 is significantly greater than according to Figure 4 The situation of the projection optical unit 28.

[0213] The following table summarizes the parameters and optical design of the projection optical unit 29. In terms of its structure, these tables are combined with the above Figure 2 The table already explained corresponds to the following.

[0214]

[0215] Figure 5 Table 1

[0216]

[0217] Figure 5 Table 2a

[0218]

[0219] Figure 5 Table 2b

[0220]

[0221]

[0222] Figure 5 Table 3a

[0223] y distance [mm] Tilt around the y axis [degrees] Tilt around z axis [degrees] Material Field 3841.367302 -0.00 -0.00 M1 3472.067232 0.00 -0.00 M2 2715.380121 180.00 0.00 M3 2016.558570 0.00 -0.00 M4 737.855663 0.00 180.00 M5 469.216382 0.00 -0.00 M6 -138.006550 180.00 0.00 M7 0.000000 0.00 -0.00 Aperture (AS) -74.346569 180.00 0.00 Image Field 0.000000 0.00 -0.00

[0224] Figure 5 Table 3b

[0225]

[0226]

[0227]

[0228]

[0229]

[0230]

[0231]

[0232]

[0233]

[0234]

[0235]

[0236]

[0237]

[0238]

[0239] Figure 5 Table 4

[0240] Reflector Reflectivity M7 0.677596 M6 0.660615 M5 0.774072 M4 0.697506 M3 0.838904 M2 0.809802 M1 0.707723 Total transmission rate 0.116199

[0241] Figure 5 Table 5

[0242]

[0243]

[0244] Figure 5 Table 6

[0245] Figure 6 Another embodiment of the projection optical unit or imaging optical unit 30 is shown, which can replace the Figure 2 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 Components and functions corresponding to those explained are denoted by the same reference numerals and will not be discussed again in detail.

[0246] The basic mirror structure of the projection optical unit 30 corresponds to Figure 4 The basic reflector structure of the projection optical unit 28 is different from that of the GI reflector, in particular in the configuration of the GI reflector. Figure 6 In the projection optical unit 30, the penultimate N1 mirror M6 is arranged on the same side as the other mirrors M1 to M5 with respect to the partial beam path portion between the last mirror M7 and the image field 11. Figure 6 The projection optical unit 30 does not have Figures 2 to 5 The intersection area corresponds to the intersection area 25 existing in the projection optical unit.

[0247] In the case of the projection optical unit 30, the chief ray CR starting from the central field point of the object field 5 extends relative to a normal N to this central field point of the object field 5 and initially relative to a plane (xN) formed by each normal N and an axis parallel to the x-axis, in a different half-space than the arrangement position of the mirror M2 and the mirror behind it, to Figure 6 To the right of the mid-normal line N.

[0248] This firstly leads to the last component 30b of the illumination optical unit 4 (eg Figure 6The illumination / imaging beam path portion 30a between the first two mirrors M1 and M2 of the projection optical unit 30 is caused to cross in the intersection region 30d. Therefore, the illumination / imaging beam path portion 30a between one of the last components of the illumination optical unit 4 (component 30b) and the object field 5, and the illumination / imaging beam path portion 30c between the object field 5 and one of the front components of the imaging optical unit 30 (the beam path portion between the mirrors M1 and M2) cross in the intersection region 30d.

[0249] Additionally, the reflector M1 is located in the other half of the space relative to the xN plane compared to the other reflector M2 and the reflector behind it.

[0250] The following table summarizes the parameters and optical design of the projection optical unit 30. In terms of its structure, these tables are combined with the above Figure 2 The table already explained corresponds to the following.

[0251]

[0252]

[0253] Figure 6 Table 1

[0254]

[0255] Figure 6 Table 2a

[0256]

[0257] Figure 6 Table 2b

[0258]

[0259] Figure 6 Table 3a

[0260] y distance [mm] Tilt around the y axis [degrees] Tilt around z axis [degrees] Material Field 2680.382457 -0.00 -0.00 M1 2434.840558 0.00 -0.00 M2 1595.484414 180.00 0.00 M3 902.729497 0.00 -0.00 M4 783.883818 0.00 180.00 M5 469.669777 0.00 -0.00 M6 138.399446 180.00 0.00 M7 0.000000 0.00 -0.00 Aperture (AS) 70.332781 180.00 0.00 Image Field 0.000000 0.00 -0.00

[0261] Figure 6 Table 3b

[0262]

[0263]

[0264]

[0265]

[0266]

[0267]

[0268]

[0269]

[0270]

[0271]

[0272]

[0273]

[0274]

[0275]

[0276] Figure 6 Table 4

[0277] Reflector Reflectivity M7 0.677581 M6 0.660010 M5 0.714146 M4 0.734803 M3 0.838417 M2 0.871903 M1 0.701377 Total transmission rate 0.120323

[0278] Figure 6 Table 5

[0279]

[0280]

[0281]

[0282] Figure 6 Table 6

[0283] Figure 7 Another embodiment of the projection optical unit or imaging optical unit 31 is shown, which can replace the Figure 2 The projection optical unit 10 in the specific embodiment is used in the projection exposure device 1. Figures 1 to 6 , especially in combination Figures 2 to 6 Components and functions corresponding to those explained are denoted by the same reference numerals and will not be discussed again in detail.

[0284] In the case of the projection optical unit 31, the chief ray CR starting from the central field point of the object field 5 extends relative to a normal N to this central field point of the object field 5 and initially relative to a plane (xN) formed by this normal N and an axis parallel to the x-axis, in a different half-space than the arrangement position of the mirror M2 and the mirror behind it, to Figure 7 To the right of the mid-normal line N.

[0285] This firstly leads to the last component 33 of the illumination optical unit 4 (e.g. Figure 7 The illumination / imaging beam path portion 32 between the first two mirrors M1 and M2 of the projection optical unit 31 and the object field 5 is caused to cross in the intersection region 35. Therefore, the illumination / imaging beam path portion 32 between one of the last components of the illumination optical unit 4 (component 33) and the object field 5, and the illumination / imaging beam path portion 34 between the object field 5 and one of the front components (mirrors M1 and M2) of the imaging optical unit 31 cross in the intersection region 35.

[0286] Additionally, the reflector M1 is located in the other half of the space relative to the xN plane compared to the other reflector M2 and the reflector behind it.

[0287] In addition, according to Figure 7 The projection optical unit 31 is configured in accordance with the GI reflectors M1 to M5. Figure 4 The projection optical unit 28 has a corresponding relationship, and the configuration of the subsequent NI reflectors M6 and M7 is consistent with that according to Figure 6 The projection optical unit 30 has a corresponding relationship.

[0288] Depending on the specific embodiment of the above-mentioned projection optical units, these projection optical units can also have a different number of NI mirrors and / or GI mirrors, for example exactly two GI mirrors or exactly three GI mirrors. More than two NI mirrors are also possible, for example three or four NI mirrors.

[0289] In order to produce a microstructured or nanostructured component, the projection exposure apparatus 1 is used as follows: First, a reflective mask 7 or reticle and a substrate or wafer 13 are provided. Next, with the aid of the projection exposure apparatus 1, the structure on the reticle 7 is projected onto the photosensitive layer of the wafer 13. Then, by developing the photosensitive layer, a microstructure or nanostructure is produced on the wafer 13, and thus a microstructured component is produced.

Claims

1. An imaging EUV optical unit (10, 27, 28, 29, 30, 31) for imaging an object field (5) into an image field (11), - having a plurality of mirrors (M1 to M6; M1 to M7; M1 to M8) for guiding EUV imaging light (16) having a wavelength shorter than 30 nm from the object field (5) to the image field (11) along an imaging beam path, - wherein the plurality of reflectors (M1 to M6; M1 to M7; M1 to M8) comprises at least two NI reflectors (M5, M6) and at least two GI reflectors (M1 to M4; M1 to M6; M1 to M5), - The total transmission rate of the plurality of reflectors (M1 to M6; M1 to M7; M1 to M8) is greater than 10%.

2. The imaging EUV optical unit according to claim 1, characterized in that: The last two mirrors in the imaging beam path (M5, M6; M7, M8; M6, M7) are NI mirrors.

3. The imaging EUV optical unit according to claim 1 or 2, characterized in that: The imaging optical unit contains exactly two NI mirrors (M5, M6; M7, M8; M6, M7).

4. The imaging EUV optical unit according to any one of claims 1 to 3, characterized in that: The imaging optical unit comprises exactly four GI mirrors (M1 to M4) or exactly five GI mirrors (M1 to M5) or exactly six GI mirrors (M1 to M6).

5. The imaging EUV optical unit according to any one of claims 1 to 4, characterized in that: The imaging optical unit comprises at least one pair (M1, M2; M3, M4; M1 to M3; M4 to M6; M4, M5) of consecutive GI mirrors which are additive in their deflection effect.

6. The imaging EUV optical unit according to any one of claims 1 to 5, characterized in that: Two imaging beam path sections intersect in an intersection region (25) between two consecutive mirrors (M3, M4; M6, M7; M5, M6) and / or between a mirror (M6; M8; M7) and the field (11) of the EUV optical unit (10).

7. The imaging EUV optical unit according to claims 2 and 6, characterized in that The two imaging beam path portions that intersect are - the imaging beam path portion located between --The mirrors (M4; M6; M5) upstream of the penultimate NI mirror (M5; M7; M6) in the imaging beam path and - the penultimate mirror in the imaging beam path (M5; M7; M6), and - the portion of the imaging beam path between the last mirror (M6; M8; M7) in the imaging beam path and the image field (11).

8. The imaging EUV optical unit according to any one of claims 1 to 7, characterized in that: An entrance pupil is located in the imaging beam path upstream of the object field (5).

9. An optical system, - having an illumination optical unit (4) for illuminating the object field (5) with the imaging light (16), - having an imaging optical unit (10) as claimed in any one of claims 1 to 8.

10. The optical system according to claim 9, characterized in that an illumination / imaging beam path portion (28a; 30a; 32) which is located between one of the last components (28b; 30b; 33) of the illumination optical unit (4) and the object field (5), and - an illumination / imaging beam path portion (28c; 30c; 34) which is located between the object field (5) and one of the first parts (M2) of the imaging optical unit (28; 30; 31), Crossing in the intersection region (28d; 28d; 34).

11. A projection exposure apparatus having an optical system as claimed in claim 9 or 10 and having an EUV light source (3).

12. A method for producing a structured component, the method comprising the following method steps: - providing a mask (7) and a wafer (13); - projecting the structure on the mask (7) onto the photosensitive layer of the wafer (13) with the aid of a projection exposure apparatus as claimed in claim 9; - Producing microstructures or nanostructures on the wafer (13).

13. A structured component produced according to the method of claim 12.

Images