Illumination optics for projection lithography

Abstract

An optical illumination system for projection lithography for illuminating an illumination field, wherein an object field of a downstream optical imaging system can be arranged. A pupil facet reflector of the optical illumination system has a plurality of pupil facets (11). Each pupil facet (11) is designed to guide a partial beam (24) of illumination light. i ). For at least some of the pupil facets (11) designed as selectively reflecting pupil facets, the following applies: the selectively reflecting pupil facets (11) have a reflective coating (27) for the illumination light. A first coating area (271) on a first portion of the selectively reflecting pupil facets (11) has a first reflectivity. A second coating area (272) on a second portion of the selectively reflecting pupil facets (11) has a second reflectivity. The first coating area (271) is different from the second coating area (272). The first reflectivity is different from the second reflectivity. In combination or as an alternative, for at least some of the pupil facets designed as having broadband reflectivity, the following applies: the facets having broadband reflectivity have a coating having broadband reflectivity for the illumination light. The result is an illumination optical system in which a desired combination of a high illumination luminous flux and a uniform illumination of the illumination field is achieved.

Description

[0001] This patent application claims the priority of German patent application DE 10 2018 220 625.2, the content of which is incorporated herein by reference. Technical Field

[0002] The invention relates to an illumination optical system for projection lithography for illuminating an illumination field, in which an object field of a subsequent imaging optical system can be arranged. Furthermore, the invention relates to an illumination system having an illumination optical system of this type, a projection exposure system having an illumination system of this type, a method for producing a microstructured or nanostructured component using a projection exposure system of this type, and a microstructured or nanostructured component produced by a production method of this type. Background Art

[0003] Illumination optical systems for projection lithography are known from US 6,658,084 B2 and US 7,196,841 B2. Such illumination optical systems are also known from US 8,817,233 B2, US 9,939,731 B2, DE 10 2008 001 511 A1, DE 10 2016 201 564 A1, DE 10 2013 218 130 A1 and DE 10 2009 017 069 A1. Summary of the invention

[0004] The object of the invention is to develop an illumination optical system of the type mentioned at the outset such that the desired combination of a high illumination luminous flux on the one hand and a homogeneous illumination of the illumination field is achieved.

[0005] This object is achieved according to the invention by an illumination optical system having the features disclosed below.

[0006] The invention discloses an illumination optical system for projection lithography for illuminating an illumination field, wherein an object field of a subsequent imaging optical system can be arranged,

[0007] the pupil facet mirror of the illumination optical system has a plurality of pupil facets, wherein each pupil facet is designed for guiding a partial bundle of illumination light,

[0008] in,

[0009] For at least some pupil facets that are designed to be selectively reflective, the following applies:

[0010] - a selectively reflecting pupil facet having a reflective coating for said illumination light, - wherein a first coating region on a first portion of said selectively reflecting pupil facet has a first reflectivity,

[0011] - wherein a second coating region on a second portion of the selectively reflecting pupil facet has a second reflectivity,

[0012] -- wherein the first coating region is different from the second coating region,

[0013] -- wherein the first reflectivity is different from the second reflectivity

[0014] and / or

[0015] For at least some of the pupil facets designed to be broadband reflecting, the following applies:

[0016] - The broadband pupil facets have a broadband reflective coating for the illumination light.

[0017] By having pupil facets with different coating areas with different reflectivity, selective reflection, correction of the illumination intensity gradient of the illumination light intensity distribution over the illumination field can be achieved. The reflective coating on the pupil facets of the corresponding selective reflection has a reflectivity distribution that can perform such correction. At least when certain critical illumination settings are applied, it is possible to finely compensate the intensity gradient on the illumination field in the absence of such correction means. Each illumination light channel including such a selectively reflecting pupil facet can be corrected independently of other illumination channels. When replacing or adding to the pupil facets of reflection to use at least one broadband reflecting pupil facet, the illumination intensity gradient that otherwise appears on the light field can be smoothed by applying a broadband coating. Such a broadband coating reduces the angular dependence of the pupil facet reflectivity and reduces the illumination intensity gradient.

[0018] The use of such selectively reflecting / broadband reflecting pupil facets adds new degrees of freedom to optimize the illumination conditions achieved by the illumination optical system. Such an illumination optical system can be used in particular in combination with an imaging optical system having a large image side numerical aperture, which can be, for example, higher than 0.3, higher than 0.4, higher than 0.5, higher than 0.6, higher than 0.7 or even higher.

[0019] The illumination light may have a wavelength in the EUV range (eg between 5 nm and 30 nm) or in the DUV range (eg at 193 nm).

[0020] A subset of all pupil facets (i.e. not all pupil facets) may be designed as selectively reflecting facets. A subset of pupil facets (i.e. not all pupil facets) may be designed as broadband reflecting facets. In the case where the pupil facet reflector comprises selectively reflecting facets as well as broadband reflecting facets, such selectively reflecting and / or broadband reflecting facets may appear on different subsets.

[0021] In one embodiment, a third coating area on a third portion of the selectively reflecting pupil facet has an additional reflectivity, wherein the third coating area is different from the first coating area and the second coating area, and the additional reflectivity is different from the second reflectivity. Embodiments of the selectively reflecting pupil facets according to the above are additional degrees of freedom. The additional reflectivity of the third coating area can be the same as the reflectivity of other non-adjacent areas, for example the same as the first coating area. In other embodiments, there can be a large number of coating areas with a specific reflectivity on the selectively reflecting pupil facet.

[0022] In one embodiment, the reflectivity of two adjacent coating areas in different coating areas merges continuously into each other. According to the above, a fine adaptation of the reflectivity over the entire selectively reflecting pupil facet can be achieved.

[0023] In one embodiment, the pupil facets of the pupil facet reflector are arranged so that the image of the light source appears at an image position at a distance from the pupil facets along the illumination channel. The pupil facets arranged according to the above increase the possibility of field-related reflectivity correction. According to the distance from the pupil facets to the image of the light source, the edge profile of the illumination light partial beam irradiated on the corresponding pupil facets can be explained by the convolution of the illumination light source profile and the field-related structure (e.g., the edge profile of the field facets). In particular, the reflectivity distribution on the pupil facets of selective reflection is matched to the size and orientation of the corresponding edge profile irradiated on the pupil facets by the size, orientation and structure of the different coating areas of the reflective coating, so that fine adjustment of the illumination distribution of the illumination light partial beam that contributes to the object field illumination becomes possible.

[0024] In order to enable such a fine adjustment of the illumination distribution of the illumination light partial bundles, the following conditions are met for the defocus distance a:

[0025] a=k B if f f / B f

[0026] Here, k represents the dimension x f The ratio between x and r, i.e. the typical range of the residual field component f and the radius r of the sub-beam emanating from the corresponding field point.

[0027] B if is the typical size of the image of the intermediate focus on the corresponding pupil facet. f is the focal length of the associated field facet, i.e. the focal length of the corresponding illumination light partial beam imaged by the associated field facet. if This is the typical range for field facets.

[0028] Therefore, the ratio K = x f / r, that is, the residual field component x on the pupil plane f The ratio between the size of B and the typical size r of the sub-beams is particularly decisive for the defocus distance value a. The following applies: 2r = B if . To enable field-dependent corrections, the following also applies:

[0029] k ≥ 0.5

[0030] In particular, k ≥ 1 may apply, i.e. the residual field component x f The typical size of is greater than the radius of the beamlet. The field correlation of the above correction improves with the increase of k, which can be greater than 1.5, greater than 2, greater than 3, greater than 4, greater than 5, or even greater.

[0031] Regarding the k condition, refer to US 9,939,731 B2.

[0032] In an embodiment, the illumination optical system further comprises a field facet mirror, wherein the field facets of the field facet mirror are imaged overlappingly onto the illumination field with the contribution of the pupil facets of the pupil facet mirror. The advantages of the illumination optical system according to the above correspond to the advantages already described above. Selectively reflecting pupil facets or broadband pupil facets may be those pupil facets which contribute to specific illumination setups, e.g. x-dipole setups, in which an object field with a high xy aspect ratio is illuminated from two illumination poles in the -x and +x directions.

[0033] The present invention also discloses an illumination system, which comprises the illumination optical system as described above and an imaging optical system for imaging the object field onto an image field.

[0034] The present invention also discloses a projection exposure system, which has the illumination system and illumination light source as described above.

[0035] The present invention also discloses a method for manufacturing a structural component, which comprises the following steps:

[0036] - providing a wafer on which a layer of light-sensitive material is at least partially applied;

[0037] - providing a reticle having the structure to be imaged,

[0038] - providing a projection exposure system as described above,

[0039] - projecting at least a portion of the reticle onto a region of a layer of the wafer by means of the projection exposure system.

[0040] The present invention also discloses a structural component manufactured by the method described above.

[0041] The advantages of the illumination system described above, the projection exposure system described above, the production method described above and the microstructured or nanostructured component described above correspond to those already discussed above with reference to the illumination optical system unit according to the invention. It is possible to specify a precisely adapted and homogeneous illumination on the component structure to be produced, so that in particular semiconductor chips with extremely fine and particularly complex structures can be produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Embodiments of the present invention will be described in more detail below with the aid of the accompanying drawings, in which:

[0043] Figure 1 A projection exposure system for microlithography is shown schematically and in a meridional section relative to an illumination optical system;

[0044] Figure 2 Shown according to Figure 1 A top view of a field facet reflector of an illumination optical system of a projection exposure system;

[0045] Figure 3 Shown according to Figure 1 A top view of a facet arrangement of a pupil facet mirror of an illumination optical system of a projection exposure system of FIG.

[0046] Figure 4 Similar to Figure 2 The views show facet arrangements of other configurations of field facet mirrors;

[0047] Figure 5 Schematically shows parts of two object field illumination channels, which are assigned to Figure 2 or Figure 4 two illumination tilt positions of the tiltable field facets of the field facet reflector, in which the incident illumination light partial beams are located;

[0048] Figure 6 It shows that it is possible to replace Figure 3 Embodiment of a pupil facet mirror for use with a pupil facet mirror, wherein the pupil facets show the edges or edge contours of the illumination light partial beams, the pupil facets being illuminated by Figure 4 irradiating exactly one of the field facets of a field facet mirror, wherein the pupil facet is arranged near the image of the light source but still at a distance therefrom;

[0049] Figure 7is a cross section of another embodiment of a pupil facet reflector comprising more than twelve pupil facets, each pupil facet showing an edge profile of an illumination light partial bundle, wherein most of the pupil facets shown are arranged near an image of the light source but still at a distance therefrom;

[0050] Figure 8 Show according to Figure 7 A pupil facet of detail VIII embodied as a selectively reflecting pupil facet, the three coating areas of the pupil facet having two different reflectivities;

[0051] Fig. 9 is a schematic side view of a further embodiment of a pupil facet which is embodied as a broadband-reflecting pupil facet having a coating for broadband reflection of the illumination light. DETAILED DESCRIPTION

[0052] The projection exposure system 1 for microlithography is used to produce microstructured or nanostructured electronic semiconductor components. The light source 2 emits EUV radiation for illumination, for example, in a wavelength range between 5 nm and 30 nm. The light source 2 can be a GDPP source (gas discharge generated plasma) or an LPP (laser generated plasma). A radiation source based on synchrotron acceleration can also be used for the light source 2. A person skilled in the art will find information about this type of light source in US 6 859 515 B2. EUV illumination light or illumination radiation 3 is used for illumination and imaging in the projection exposure system 1. The EUV illumination light 3 after the light source 2 first passes through a collector 4, which is, for example, a nested collector with a multi-shell structure known in the prior art, or an elliptical collector. A corresponding collector is known from EP 1 225 481 A. After the collector 4, the EUV illumination light 3 first passes through an intermediate focal plane 5, which can be used to separate the EUV illumination light 3 from unwanted radiation or particle parts. After passing through the intermediate focal plane, the EUV illumination light 3 is first incident on the field facet mirror 6 .

[0053] In order to facilitate the description of positional relationships, a Cartesian global xyz coordinate system is firstly drawn in each case in the figures. Figure 1 The x-axis in FIG. 1 extends outwardly perpendicular to the plane of the drawing. Figure 1 The y-axis extends to the right. Figure 1 , the z-axis extends upward.

[0054] In order to facilitate the description of positional relationships in the individual optical components of the projection exposure system 1, a Cartesian local xyz or xy coordinate system is also used in each case in the following figures. The respective local xy coordinates described in the other cases span the respective main arrangement plane of the optical component, for example a reflection plane. The x axes of the global xyz coordinate system and the local xyz or xy coordinate system extend parallel to each other. The respective y axis of the local xyz or xy coordinate system forms an angle with the y axis of the global xyz coordinate system, which corresponds to the tilt angle of the respective optical component about the x axis.

[0055] Figure 2 As an example, a facet arrangement of field facets 7 of a field facet mirror 6 is shown. The field facets 7 are rectangular and have the same x / y aspect ratio in each case. The x / y aspect ratio may be, for example, 12 / 5, 25 / 4 or 104 / 8.

[0056] The field facets 7 specify the reflecting surfaces of the field facet reflector 6 and are grouped into four columns, each with six to eight field facet groups 8a, 8b. The field facet group 8a has seven field facets 7 in each case. The two additional edge-side field facet groups 8b of the two central field facet columns have four field facets 7 in each case. Between the two central facet columns and between the third and fourth facet rows, the facet arrangement of the field facet reflector 6 has an intermediate space 9, in which the field facet reflector 6 is shielded by the spokes holding the light collector 4.

[0057] After reflection on the field facet mirror 6 , the EUV illumination light 3 divided into pencil beams or partial beams which are distributed to the individual field facets 7 impinges on a pupil facet mirror 10 .

[0058] Figure 3 An exemplary facet arrangement of circular pupil facets 11 of a pupil facet mirror 10 is shown. The pupil facets 11 are arranged in facet rings within one another around a center. At least one pupil facet 11 is assigned to each partial beam of EUV illumination light 3 reflected by one of the field facets 7, so that in each case an object field illumination channel of the associated partial beam of the given EUV illumination light 3 is illuminated thereon with one field facet 7 and one facet of pupil facet 11. The channel-by-channel assignment of pupil facets 11 to the field facets 7 takes place in the projection exposure system 1 depending on the desired illumination.

[0059] By means of the pupil facet mirror 10 (see Figure 1) and a subsequent transfer optical system 15 consisting of three EUV mirrors 12, 13, 14 images the field facets 7 in an object plane 16 of the projection exposure system 1. The EUV mirror 14 is configured as a grazing incidence mirror. A mask master 17 is arranged on the object plane 16, through which an illumination area in the form of an illumination field is illuminated with EUV illumination light 3, which illumination field coincides with an object field 18 of a downstream projection optical system 19 of the projection exposure system 1. Instead of such a coincidence of the illumination field with the object field 18, the object field 18 can be arranged within a larger illumination field. The object field illumination channel is covered in the object field 18. In particular, with the contribution of the pupil facets 11 to the object field 18, the field facets 7 are imaged overlappingly.

[0060] The EUV illumination light 3 is reflected by the reticle 17 .

[0061] The projection optical system 19 images the object field 18 in the object plane 16 into an image field 20 in an image plane 21. In the image plane 21 there is arranged a wafer 22 carrying a photosensitive layer which is exposed during projection exposure by the projection exposure system 1. During projection exposure, both the reticle 17 and the wafer 22 are scanned in a synchronized manner in the y direction. The projection exposure system 1 is configured as a scanner. In the following, the scanning direction is also referred to as the object displacement direction.

[0062] The field facet mirror 6, the pupil facet mirror 10 and the mirrors 10 to 14 of the transfer optical unit 15 are components of an illumination optical system 23 of the projection exposure system 1. Together with the projection optical system 19, the illumination optical system 23 forms the illumination system of the projection exposure system 1.

[0063] The field facet mirror 6 is a first facet mirror of the illumination optical system 23. The field facet 7 is a first facet of the illumination optical system 23.

[0064] Pupil facet mirror 10 is a second facet mirror of illumination optical system 23 Pupil facet 11 is a second facet of illumination optical system 23 .

[0065] Figure 4 Other configurations of the field facet reflector 6 are shown. Figure 2 Components corresponding to those described for the field facet reflector 6 of FIG. 1 have the same reference numerals, and only those components corresponding to those described for the field facet reflector 6 of FIG. 1 will be described. Figure 2 The components of the field facet reflector 6 are different. Figure 4 The field facet arrangement of the field facet reflector 6 has curved field facets 7. These field facets 7 are arranged in a total of five columns, each column having a plurality of field facet groups 8. The field facet arrangement is written into the circular confinement of the carrier plate of the field facet reflector.

[0066] according to Figure 4The field facets 7 of the embodiment all have the same area and the same ratio of width in the x-direction to height in the y-direction, which corresponds to Figure 2 The x / y aspect ratio of the configured field facet 7.

[0067] For example, two pupil facets 11 of a pupil facet mirror 10 are assigned in each case by the object field illumination channel to each correspondingly configured field facet 7 of the field facet mirror 6. Thus, there are twice as many pupil facets 11 of the pupil facet mirror 10 as there are field facets 7 of the field facet mirror 6.

[0068] Depending on the configuration of the mechanical tilt capability of the field facets 7, more than two pupil facets 11 of the pupil facet mirror 10 can be assigned to one field facet 7 via the respective object field illumination channel. The field facets 7 can then be moved into a corresponding number of illumination tilt positions.

[0069] Figure 5 The diagram shows the reflected guidance of a partial beam 24 of the entire beam of illumination light 3. The reflection surface 25 of the field facet 7 shown as an example can be tilted between a first illumination tilt position, which guides the partial beam 24 impinging on the reflection surface 25 to the object field 18 or the illumination field along a first object field illumination channel 261 (dashed line), and a further illumination tilt position, which guides the partial beam 24 to the object field 18 along a further object field illumination channel 262 (solid line).

[0070] Along the first illumination channel 261, the partial beam 24 after reflection on the field facet 7 is reflected on the first pupil facet 111. The pupil facet 111 is therefore assigned to the field facet 7 via the object field illumination channel 261. Along the object field illumination channel 262, in other words, at a further illumination tilt position of the field facet 7, the partial beam 24 after reflection on the field facet 7 is reflected on a further pupil facet 112 of the pupil facet mirror 10. Figure 5 Only some of the pupil facets 11 of the pupil facet mirror 10 are shown, namely those pupil facets 11 which are located adjacent to the pupil facets 111, 112. i .

[0071] Figure 6 One of the pupil facets 11 that can be used in the pupil facet mirror 10 is shown. Figure 6 The pupil facet 11 does not have Figure 3 Or 5 presents a circular edge or edge profile, but instead has an approximately square edge or edge profile with rounded corners. Such an edge or edge profile (which can also be designed without rounded corners, i.e. in a square or rectangular manner) allows the pupil facet carrier to be relatively densely occupied by pupil facets 11.

[0072] according to Figure 6 The pupil facet 11 is derived from the Figure 4 The illumination light beam 24 of the arcuate field facet 7 of the field facet reflector 6 i Come to irradiate.

[0073] Figure 6 The illumination partial beam 24 reflected by the pupil facet 11 is shown. i The position of the illumination light beam 24 i The entire cross section of the illumination beam 24 is located on the pupil facet 11, so the illumination beam 24 i The edges or margins of the pupil facets 11 are not cut off or clipped by the edges or margins of the pupil facets 11. The illumination light partial beam 24 on the pupil facets 11 i The cross-sectional edge or edge profile has an approximately arc-shaped, bean-shaped or kidney-shaped shape, and can be understood as Figure 4 The image of the arc field facet 7 (see Figure 6 The solid line "7 B ”) and the circular source area of ​​light source 2. This convolution occurs because the image of light source 2 appears along the illumination channel 24 i At an image position at a distance from the pupil facet 11, ie upstream or downstream of the pupil facet 11 in the beam path.

[0074] Illumination light beam 24 i The arc-shaped edges or edge contours on the pupil facet 11 represent the illumination light partial beams 24. i light spot.

[0075] Illumination light beam 24 i The three sub-beams 24 i 1 ,twenty four i 2 and 24 i 3 In the illumination beam 24 i The edge or edge contour of the pupil 11 is drawn with a dotted line. The illumination light beam 24 i A large number of such sub-beams 24 i j Within the range of known optical parameters of the illumination, the illumination light beam section 24 can be calculated, for example, by means of an optical design program. i .

[0076] These sub-beams 24 i 1 to 24 i 3 The illumination light 3 is emitted from the left edge or edge point 7 of the associated field facet 7 1 , from the central point 7 2 , and right edge or edge point 73 Set off. Figure 4 These initial points 7 1 to 7 3 is drawn in an exemplary manner on one of the field facets 7 .

[0077] Edge sub-beam 24 i 1 and 24 i 3 The intensity is less than the central beamlet 24 i 2 strength.

[0078] Figure 7 FIG. 2 shows a cross section of another embodiment of a pupil facet reflector 10, which can be used in the illumination optical system 23 instead of the pupil facet reflector 10 described above. Figures 1 to 6 The components and functions described have the same reference numerals and are not discussed again in detail.

[0079] exist Figure 7 In the embodiment of FIG. 1 , the pupil facets 11 have a hexagonal outer contour and are shown in close packing. The illumination light partial bundles 24 of the corresponding illumination channel 26 are shown on the respective pupil facets 11. i Depending on the spatial relationship between the field facets 7 and the pupil facets 11 belonging to each of the respective illumination channels and on the distance of the respective pupil facets to the image of the light source, the illumination light partial bundles 24 i The illuminating light partial beams 24 have different orientations and extensions on their assigned pupil facets 11. For pupil facets 11 positioned close to the image of the light source, the illuminating light partial beams 24 i It has a more or less point shape and represents the image of the light source 2. For pupil facets 11 that are at a greater distance from the image of the light source, the corresponding illumination light partial beam 24 impinging on the pupil facet 11 i The expansion is large, and the edge contour of such an illumination light partial bundle 24 can be identified as a convolution of the light source image and the shape of the corresponding field facet 7 (ie shown as an arc shape).

[0080] Figure 8 One of the pupil facets 11 is shown enlarged and in detail. Figure 8 Such pupil facets 11 are designed as selectively reflecting pupil facets 11. i) has a first coating area 271 on a first portion of the pupil facet 11, a second coating area 272 on a second portion of the pupil facet 11, and a third coating area 273 on a third portion of the pupil facet 11. Both the first coating area 271 and the third coating area 273 have a first higher reflectivity R for the illumination light 3. 1 / 3 The second coating region 272 has a second reflectivity R2 that is lower than the first reflectivity.

[0081] The reflectivity R of these coating areas 271, 273 on the one hand and 272 on the other hand 1 / 3 The reflectivity ratio of the edge beamlet 24 is at least approximately i 1 ,twenty four i 3 and on the other hand the central sub-beam 24 i 2 The intensity ratio I on the corresponding coating areas 271, 273 and 272 1 / 3 / The reciprocal of I2.

[0082] Such a ratio value results in that the illumination light beam 24 i The intensity of the illumination light 3 seen over the entire area of ​​the illumination light beam 24 can be homogenized / compensated by dividing the reflective coating 27 into a plurality of coating areas with correspondingly adapted reflectivities. i This can be used as a homogeneity correction device to ensure a given intensity homogeneity in the x-direction of the object field 18, ie to ensure illumination homogeneity over the field height x.

[0083] As mentioned above, Figure 7 Some or all pupil facets 11 of the pupil facet mirror 10 may be embodied as selectively reflecting pupil facets 11 .

[0084] Different coating areas 27 i The arrangement on each pupil facet 11 depends on the corresponding illumination light partial bundle 24 i The position, orientation and spread of the illumination on such a pupil 11. Coating area 27 i This variable arrangement can be achieved by coating the area 27 i The coating regions 27 may be formed by different orientations of the boundaries between the coating regions 27 and / or by different extensions and / or by different numbers of such coating regions 27. i Furthermore, depending on the respective selectively reflecting pupil facet embodiment, two adjacent differently coated areas 27 i The reflectivity (i.e., according to Figure 8The reflectivity of the coating regions 271 and 272 or the reflectivity of the coating regions 272 and 273 of the embodiment of the present invention can be continuously merged with each other so that the reflectivity dependency of the reflective coating 27 is matched to the illumination beam 24 as a whole. i strength correlation.

[0085] Fig. 9 A side view of another embodiment of a pupil facet 11 is shown. Fig. 9 The pupil facet 11 is designed as a broadband reflecting pupil facet. Fig. 9 Such a pupil facet 11 may be used for some or all pupil facets of one of the embodiments of the pupil facet mirror 10 described above.

[0086] according to Fig. 9 The broadband pupil facet 11 has a broadband reflective coating 28 carried by the body of the broadband reflective pupil facet 11 .

[0087] The broadband reflective coating 28 can be embodied as a multilayer coating, in other words a multilayer coating having an alternating, non-periodic sequence of molybdenum layers and silicon layers.

[0088] Instead of a multilayer reflective coating, it is also possible to use a single-layer or double-layer reflective coating with a very narrow incidence angle tolerance range. When using a multilayer reflective coating with a non-periodic layer stack, in other words a so-called broadband coating, the incidence angle tolerance range increases.

[0089] During projection exposure, a reticle 17 and a wafer 22 are provided, which carries a photosensitive coating for EUV illumination light 3. At least a portion of the reticle 17 is then projected onto the wafer 22 by means of the projection exposure system 1. Finally, the photosensitive layer exposed with EUV illumination light 3 is developed on the wafer 22. In this way, microstructured or nanostructured components, such as semiconductor chips, are produced.

[0090] The above embodiments are described with the aid of EUV illumination. As an alternative to EUV illumination, for example UV or VUV illumination can also be used, for example illumination light with a wavelength of 193 nm.

Claims

1. An illumination optical system (23) for projection lithography for illuminating an illumination field, in which an object field (18) of a subsequent imaging optical system (19) can be arranged, The pupil facet mirror (10) of the illumination optical system has a plurality of pupil facets (11), wherein: Each pupil facet (11) is designed to guide the illumination light beamlet (24 i ), in, For at least some pupil facets (11) designed as selectively reflecting facets, the following applies: - the selectively reflecting pupil facet (11) has a reflective coating (27) for the illumination light (3), wherein a first coating area (271) on a first portion of the selectively reflecting pupil facet (11) has a first reflectivity (R1), wherein a second coating region (272) on a second portion of the selectively reflecting pupil facet (11) has a second reflectivity (R2), -- wherein the first coating region (271) is different from the second coating region (272), -- wherein the first reflectivity (R1) is different from the second reflectivity (R2), and / or For at least some of the pupil facets (11) designed as broadband reflecting pupil facets, the following applies: The broadband pupil facet (11) has a broadband reflective coating (28) for the illumination light (3).

2. The illumination optical system according to claim 1, - wherein a third coating area (273) on a third portion of the selectively reflecting pupil facet (11) has a further reflectivity (R3), wherein, The third coating region (273) is different from the first coating region and the second coating region (271, 272), - wherein said further reflectivity (R3) is different from said second reflectivity (R2).

3. The illumination optical system according to claim 1 or 2, wherein: The reflectivities of two adjacent coating areas (271, 272; 272, 273) of different coating areas merge continuously into each other.

4. The illumination optical system according to claim 1 or 2, wherein: The pupil facets (11) of the pupil facet mirror (10) are arranged so that an image of a light source emitting the illumination light appears at an image position at a distance from the pupil facets along an illumination path of the illumination light.

5. The illumination optical system according to claim 1 or 2, wherein: The illumination optical system (23) further comprises a field facet mirror (6), wherein the field facets (7) of the field facet mirror (6) are imaged onto the illumination field in an overlapping manner with the contribution of the pupil facets (11) of the pupil facet mirror (10).

6. An illumination system comprising an illumination optical system (23) according to any one of claims 1 to 5 and an imaging optical system (19) for imaging the object field (18) onto an image field (20).

7. A projection exposure system (1) comprising an illumination system as claimed in claim 6 and an illumination light source (2).

8. A method for manufacturing a structural component, comprising the following steps: - providing a wafer (22) on which a layer of light-sensitive material is at least partially applied; - providing a reticle (17) having the structure to be imaged, - providing a projection exposure system (1) as claimed in claim 7, - projecting at least a portion of the reticle (17) onto a region of a layer of the wafer (22) by means of the projection exposure system (1).

9. A structural component manufactured by the method of claim 8.

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