WO2016078964A1

WO2016078964A1 - Illumination optical unit for illuminating an illumination field and projection exposure apparatus comprising such an illumination optical unit

Info

Publication number: WO2016078964A1
Application number: PCT/EP2015/076185
Authority: WO
Inventors: Markus DEGÜNTHER; Stig Bieling
Original assignee: Carl Zeiss Smt Gmbh
Priority date: 2014-11-18
Filing date: 2015-11-10
Publication date: 2016-05-26
Also published as: TW201626111A; DE102014223454A1; TWI687776B

Abstract

An illumination optical unit serves to illuminate an illumination field in which an object to be imaged is arrangeable. The illumination optical unit comprises at least one facet mirror and one deflection mirror assembly (5b) in the beam path of an illumination light beam (22) upstream of the facet mirror. The deflection mirror assembly (5b) is embodied in such a way that it deflects a centroid ray (S_in, S_out) of the illumination light beam (22) by at least 10°. The deflection mirror assembly (5b) has at least two mirrors (23, 24) for grazing incidence. These each reflect a dedicated partial beam (25, 26) of the overall illumination light beam (22). What emerges is an illumination optical unit which can be adapted to various light source configurations with little outlay.

Description

Illumination optical unit for illuminating an illumination field and projection exposure apparatus comprising such an illumination optical unit The present application claims priority of German patent application DE 10 2014 223 454.9, the content of which is incorporated herein by reference.

The invention relates to an illumination optical unit for illuminating an illumination field, in which an object to be imaged is arrangeable.

Furthermore, the invention relates to an illumination system comprising such an illumination optical unit, an optical system comprising such an illumination optical unit and a projection optical unit for imaging the illumination field in an image field, a projection exposure apparatus comprising such an optical system, a method for producing a

microstmctured or nanostmctured component and a component produced by this method.

An illumination optical unit as assembly for a projection exposure apparatus is known from US 2005/0207039 Al, US 2003/0095623 Al, US 2005/0093041 Al, US 2005/0094764 Al and US 2005/0274897 Al .

It is an object of the present invention to develop an illumination optical unit in such a way that it can be adapted to various light source

configurations with little outlay.

According to the invention, this object is achieved by an illumination optical unit comprising the features specified in Claim 1. On account of the deflecting effect thereof for the centroid ray, the deflection mirror assembly enables an adaptation to light sources with different centroid ray profiles of an illumination light beam emitted by the light source. The deflection mirror assembly can receive the emitted illumination light beam with the centroid ray profile predetermined by the light source configuration and deflect the latter into a reflected centroid ray profile which the subsequent illumination optical unit comprising the at least one facet mirror can process. The centroid ray deflection by way of the deflection mirror assembly can be through at least 15° or else through at least 20°. Deflection angles of e.g. 19°, 20° or 25° are possible. By way of a design of reflection surfaces of the mirrors for grazing incidence of the deflection mirror assembly, it is also possible to adapt further illumination parameters dependent on the respective light source configuration in such a way that these are matched the subsequent illumination optical unit. In particular, the deflection mirror assembly can be used to adapt an etendue of the light source to the etendue that is receivable by the subsequent illumination optical unit. The deflection mirror assembly can be embodied with high reflection efficiency. The mirrors for grazing incidence can be embodied as curved mirrors, in particular as concavely curved mirrors. Reflection surfaces of the mirrors for grazing incidence can be embodied as aspherical surfaces. The reflection surfaces of the mirrors for grazing incidence can be embodied as free-form surfaces, which cannot be described by way of a rotationally symmetric surface. The deflection mirror assembly can be arranged downstream of a collector collecting the illumination light of the light source.

An arrangement according to Claim 2 enables an advantageously compact embodiment of the deflection mirror assembly. The deflection mirror assembly can be arranged with little distance from the intermediate focus. By way of example, a distance between the intermediate focus and the deflection mirror assembly can be less than a third or a fifth of a light path between the intermediate focus and the next facet mirror of the illumination optical unit.

An embodiment according to Claim 3 enables a use of the deflection mirror assembly with light sources that provide a corresponding maximum numerical aperture of 0.3 at the intermediate focus. The deflection mirror assembly can be embodied for covering a numerical aperture of the intermediate focus of e.g. 0.22.

An effect of the deflection mirror assembly changing, e.g. increasing or, according to Claim 4, decreasing, the effective numerical aperture of the intermediate focus enables a use of e.g. a light source with a comparatively small numerical aperture, which is provided without the effect of the deflection mirror assembly in the region of the intermediate focus, in combination with an illumination optical unit arranged downstream thereof, which illumination optical unit, in comparison therewith, can process a relatively large numerical aperture of the intermediate focus. Then, it is possible to use an illumination optical unit which is designed for a type of light source with a relatively high numerical aperture of the intermediate focus, wherein, by using the deflection mirror assembly, this illumination optical unit then can also be used with a light source which provides a relatively small numerical aperture of the intermediate focus. The increased effective numerical aperture, which is available after reflection at the deflection mirror assembly, may be e.g. 0.2 or 0.22. This also applies to the reverse case, i.e. an illumination system, which expects a relatively small numerical aperture (e.g. 0.16), can thus be operated with a source which provides a relatively large numerical aperture (e.g. 0.22). Here, this is a specific application. The divergence of the overall illumination light partial beam after reflection at the deflection mirror assembly can correspond to an effective numerical aperture which is increased by at least 10% in comparison with a numerical aperture of the intermediate focus. In principle, the effective numerical aperture of the overall illumination light partial beam can also be just as large as the numerical aperture of the intermediate focus. This can be achieved by embodying the mirrors of the deflection mirror assembly as plane mirrors. More than two mirrors for grazing incidence according to Claim 5 enable a specific adaptation of parameters of the sub beams reflected by these mirrors. In particular, a specific adaptation of a far field geometry, which is composed of the far fields of the partial beams, is possible. The deflection assembly can have three mirrors, four mirrors, five mirrors, six mirrors, eight mirrors, ten mirrors or even more mirrors.

An embodiment according to Claim 6 enables a comparatively simple design of the mirrors for grazing incidence. What is possible to achieve by using a relatively large number of mirrors mirroring the far field intensity distribution in this way is that a far field downstream of the deflection mirror assembly resembles the original, non-mirrored far field more strongly than would be the case if a smaller number of mirrors mirroring the far field intensity distribution were to be used. In the case where the original far field intensity distribution is optimized in such a way that comparatively small switching angles of facets of the at least one facet mirror are required, this advantage can be maintained even after reflection at the deflection mirror assembly. A hyperboloid mirror according to Claim 7, i.e. a mirror, the reflection surface of which is embodied as a section of hyperboloid, leads to a deflection mirror assembly with a corresponding effect on the beam parameters of the reflected partial beams. Such a hyperboloid embodiment is suitable both for increasing and for decreasing an effective numerical aperture.

A spaced apart arrangement of the mirrors for grazing incidence according to Claim 8 increases an installation space respectively available for adjacent mirrors of the deflection mirror assembly.

The advantages of an illumination system according to Claims 9 and 10, an optical system according to Claim 1 1, a projection exposure apparatus according to Claim 12, a production method according to Claim 13 and a microstructured or nanostructured component according to Claim 14 correspond to those which were already explained above with reference to the illumination optical unit according to the invention. An EUV light source can be used as illumination light source. The produced component is, in particular, a semiconductor chip, for example a memory chip.

Exemplary embodiments of the invention are explained in more detail below on the basis of the drawing. In detail:

Figure 1 shows a very schematic meridional section of a projection exposure apparatus for EUV microlithography, comprising a light source, an illumination optical unit and a projection optical unit; Figure 2 shows a sectional magnification of the region II in Figure 1 with a deflection mirror assembly of the illumination optical unit in the beam path of an illumination light beam downstream of an intermediate focus;

Figure 3 shows a further embodiment of the deflection mirror assembly, with spatial requirements for various illumination-optical components being highlighted; Figure 4 shows an illustration similar to Figure 3 of a further

arrangement example for deflection mirrors of a deflection mirror assembly, which can be used instead of the deflection mirror assembly according to Figures 2 and 3; Figure 5 shows an illustration similar to Figure 2 of a further

embodiment of a deflection mirror assembly with four deflection mirrors;

Figure 6 schematically shows a far field of the light source in the beam path downstream of the deflection mirror assembly according to Figure 2; and

Figure 7 schematically shows a far field of the light source in the beam path downstream of the deflection mirror assembly according to Figure 5.

A projection exposure apparatus 1 for microlithography, depicted very schematically and in the meridional section in Figure 1 , comprises a light source 2 for illumination light 3. The light source 2 is an EUV light source, which generates light in a wavelength range of between 5 nm and 30 nm. Here, this can be an LPP (laser produced plasma) light source, a DPP (gas discharge produced plasma) light source or a synchrotron radiation-based light source, e.g. a free electron laser (FEL).

A transmission optical unit 4 serves to guide the illumination light 3 emanating from the light source 2. Said transmission optical unit comprises a collector 5, which is merely depicted in view of the reflective effect thereof in Figure 1 , and a transmission facet mirror 6, which is also referred to as first facet mirror. The collector 5 can be a Wolter-type collector. Use can also be made of a collector 5 embodied as an ellipsoid mirror. An intermediate focus 5a (cf. Figure 2) of the illumination light 3 is arranged between the collector 5 and the transmission facet mirror 6. By way of example, a numerical aperture of the illumination light 3 in the region of the intermediate focus 5a is NA = 0.16 or 0.22. The NA at the intermediate focus 5a is at most 0.3 and can, for example, also have a value in the region of 0.17, in the region of 0.18 or in the region of 0.19.

A deflection mirror assembly 5b, which will still be explained in more detail below, is disposed directly downstream of the intermediate focus 5a in the beam path of the illumination light 3.

An illumination pre-defmition facet mirror 7 is disposed downstream of the transmission facet mirror 6 and therefore of the transmission optical unit 4. The optical components 5 to 7 are components of an illumination optical unit 8 of the projection exposure apparatus 1. The illumination pre- defmition facet mirror 7 can be arranged in, or in the region of, a pupil plane of the illumination optical unit 8 in one embodiment of the illumination optical unit 8 and can also be arranged at a distance from the pupil plane, or the pupil planes, of the illumination optical unit 8 in a further embodiment of the illumination optical unit 8.

Disposed downstream of the illumination pre-defmition facet mirror 7 in the beam path of the illumination light 3 is a reticle 9, which is arranged in an object plane 10 of a downstream projection optical unit 1 1 of the projection exposure apparatus 1. The projection optical unit 1 1, which is indicated very schematically in Figure 1 by a dashed boundary line, is a projection lens in each case.

A Cartesian xyz-coordinate system is used below so as to simplify the illustration of positional relationships. In Figure 1, the x-direction extends perpendicular to the plane of the drawing and into the latter. In Figure 1 , the y-direction extends to the right. In Figure 1 , the z-direction extends downwards. Coordinate systems used in the drawing respectively have x- axes extending parallel to one another. The extent of a z-axis of these coordinate systems follows a respective main direction of the illumination light 3 within the respectively considered figure. Using the illumination optical unit 8, an object field 12 on the reticle 9 is illuminated in the object plane 10 in a defined manner. An actually illuminated illumination field can be larger than the object field 12 or can coincide with the object field 12. The object field 12 has an arcuate or partial circle-shaped form and is delimited by two mutually parallel circular arcs and two straight side edges, which extend in the y-direction with a length y₀ and have a distance xo from one another in the x-direction. The aspect ratio x₀/yo is e.g. 13 to 1. In an alternative and likewise possible object field 12, the boundary form thereof is not arcuate but rectangular. The reticle 9 is supported by a reticle holder 12a, which is connected back to an object displacement drive 12b. By way of the object displacement drive 12b, the reticle holder 12a can be displaced together with the reticle 9 in a controlled manner along the y-direction.

The projection optical unit 1 1 is only indicated partly and very

schematically in Figure 1. What is depicted is an object field-side numerical aperture 13 and an image field-side numerical aperture 14 of the projection optical unit 1 1. Between indicated optical components 15, 16 of the projection optical unit 1 1, which may e.g. be embodied as mirrors reflecting the EUV illumination light 3, there are further optical

components of the projection optical unit 1 1, not depicted in Figure 1, for guiding the illumination light 3 between these optical components 15, 16. The projection optical unit 1 1 images the object field 12 into an image field 17 in an image plane 18 on a wafer 19 which, like the reticle 9 too, is carried by a holder 20 and has a functional connection to a wafer displacement drive 21. Both the reticle holder 12a and the wafer holder 20 are displaceable both in the x-direction and in the y-direction by way of the displacement drives 12b, 21.

The transmission facet mirror 6 has a plurality or multiplicity of

transmission facets, which are not depicted in the drawing. The

transmission facet mirror 6 can be embodied as a MEMS mirror. The transmission facets are grouped during projection operation into a plurality of transmission facet groups not depicted in any more detail. Overall, the transmission facet mirror 6 has a region impinged upon by the illumination light 3, which can have an x/y-aspect ratio of less than 1. The value y/x of this aspect ratio can be at least 1.1 or even greater. In one embodiment of the illumination optical unit with an illumination pre-defmition facet mirror 7 arranged in a pupil plane, an x/y-aspect ratio of the transmission facet groups has at least the same size as the x/y-aspect ratio of the object field 12. In the depicted embodiment, the x/y-aspect ratio of the transmission facet groups is greater than the x/y-aspect ratio of the object field 12. The transmission facet groups have a partial circle-shaped arcuate group boundary form, which is similar to the boundary form of the object field 12. In respect of more details in respect of the design of the transmission facet mirror 6, reference is made to WO 2010/099 807 A. Each one of the transmission facet groups guides a portion of the illumination light 3 for the partial or complete illumination of the object field 12.

The transmission facets are micromirrors which are switchable, at least between two tilt positions. The transmission facets can be embodied as micromirrors that the tiltable about two mutually perpendicular axes of rotation. The transmission facets are aligned in such a way that the illumination pre-defmition facet mirror 7 is illuminated with a

predetermined boundary form and a predetermined assignment of the transmission facets to the illumination pre-defmition facets of the illumination pre-defmition facet mirror 7, which are likewise not depicted in the drawing. In respect of further details of the embodiment of the illumination pre-defmition facet mirror 7 and the projection optical unit 1 1, reference is made to WO 2010/099 807 A. The illumination pre-defmition facets are micromirrors that are tiltable between at least two tilt positions. Particularly when the illumination pre-defmition facet mirror 7 is arranged at a distance from a pupil plane of the illumination optical unit, the illumination pre-defmition facets can be embodied as micromirrors which are tiltable continuously and independently about two mutually

perpendicular tilt axes, i.e. said illumination pre-defmition facets can be put into a multiplicity of different tilt positions.

Figure 2 shows, in detail, the beam path of the illumination light 3 in the region of the deflection mirror assembly 5b, which is arranged directly downstream of the intermediate focus 5a in this beam path. The deflection mirror assembly 5b is arranged in the beam path of a light beam 22 upstream of the transmission facet mirror 6. The deflection mirror assembly 5b is embodied in such a way that it deflects a centroid ray of the illumination light beam 22 by at least 10°. A centroid ray of the

illumination light beam 22 incident into the deflection mirror assembly 5b is denoted by in Figure 2. A centroid ray of the illumination light beam 22 reflected by, i.e. leaving from, the deflection mirror assembly 5b is denoted by S_out in Figure 2. Figure 2 also plots a deflection angle a, about which the centroid ray S is deflected when reflected at the deflection mirror assembly 5b. In the embodiment according to Figure 2, this deflection angle a is approximately 25°. Other deflection angles a of at least 10° are also possible, for example a deflection angle a of at least 15°, of at least 20°, or else a deflection angle a which is greater than 25° and, for example, equals 30° or 35°.

The deflection mirror assembly 5b according to Figure 2 has two mirrors 23, 24 for grazing incidence, which are also denoted as GI (grazing incidence) mirrors below. A mirror for grazing incidence is a mirror with an angle of incidence for the illumination light 3 which is greater than 45° and which may be greater than 60°, 65° or 70° and which may, for example, lie in the region of between 70° and 85° or else in the region of between 70° and 88° or 89°. The GI mirrors 23, 24 are embodied as hyperbolic mirrors, i.e. they have reflection surfaces that correspond to sections of a rotation hyperboloid. The GI mirrors 23, 24 carry a coating that is highly reflective for the illumination light 3. Each one of the two GI mirrors 23, 24 reflects a dedicated partial beam 25, 26 of the overall illumination light beam 22. The two partial beams 25, 26 directly adjoin one another in the beam path downstream of the deflection mirror assembly 5b, i.e. they have a practically negligible distance from one another.

A divergence of the overall illumination light beam 22 after reflection at the deflection assembly 5b corresponds to an effective numerical aperture NAg , which may be at least 10% increased or at least 10% reduced compared with the numerical aperture in the intermediate focus 5 a, or else it may be identical therewith. This effective numerical aperture NA_e emerges from an angle between the emerging centroid ray S_out and an outer marginal ray 27 of the overall illumination light beam 22 after reflection at the deflection mirror assembly 5b. Thus, an angle of a marginal ray of the reflected illumination light beam 22 in relation to the centroid ray S_out constitutes a measure for NA_eff. In the embodiment according to Figure 2, the effective numerical aperture NA_eff has a value of 0.16.

Thus, the deflection mirror assembly 5b not only brings about a centroid ray deflection, as explained above, but it also generates an increase or reduction in an effective numerical aperture of the intermediate focus. Following the deflection mirror assembly 5b, it is possible to use downstream optical components of the illumination optical unit 8, which are prepared for a light source with an intermediate focus with a numerical aperture corresponding to this effective numerical aperture.

Individual rays of the illumination light beam 22 are respectively reflected exactly once at the GI mirrors 23, 24 of the deflection mirror assembly 5b. Each one of the individual rays is reflected at exactly one of the GI mirrors 23, 24. Thus, there is no sequential impingement of the GI mirrors 23, 24 with one and the same individual ray of the illumination light beam 22.

Figure 6 shows a far field 28 of the light source 2, recorded in the region of the transmission facet mirror 6 in a xy-plan view. Figure 6 also plots an edge contour 6a of the transmission facet mirror 6. The two GI mirrors 23, 24 each bring about mirroring of a far field intensity distribution present at the outset, i.e. the far field intensity distribution without the deflecting effect of the GI mirrors 23, 24, respectively about a mirror plane parallel to the xz-plane. These two mirror planes are indicated at 29 and 30 in Figure 6. The far field distribution which is approximately ring-shaped without the deflecting effect of the GI mirrors 23, 24, the outer edge contour 31 of which far field distribution is indicated by a dashed line in Figure 6, turns into a far field intensity distribution constructed from two semi rings 32, 33, the ring centres Z of which are away from one another.

Using Figures 3 to 5 and 7, further embodiments of deflection mirror assemblies, which can be used in the illumination optical unit 8 instead of the deflection mirror assembly 5b according to Figures 1 and 2, are explained below. Components corresponding to those that were already explained above with reference to Figures 1 , 2 and 6 are denoted by the same reference signs and are not discussed in detail again.

Apart from a slightly smaller deflecting effect with a deflection angle a of approximately 20°, a deflection mirror assembly 34 according to Figure 3 has, in principle, the same design as the deflection mirror assembly 5b according to Figures 1 and 2.

Figure 3 schematically depicts installation spaces 35, for source-side components in the region of the intermediate focus, and 36, for the left- hand GI mirror 23 in Figure 3. This installation spaces 36 lies between the GI mirrors 23, 24 and is therefore relatively restricted.

In respect of the optical effect thereof, i.e. in respect of, firstly, the centroid ray deflection and, secondly, the magnification or reduction of the intermediate focus NA into an effective numerical aperture NA_e , a further deflection mirror assembly 37 according to Figure 4 corresponds to the deflection mirror assembly 34 according to Figure 3. In contrast to the deflection mirror assembly 34, the right-hand GI mirror 24 in Figure 4 deflects the illumination light partial beam 26 assigned thereto offset from the other illumination light partial beam 25 by a distance A with the main component in the y-direction. The two opening cones of the partial beams 25, 26 are spaced apart by this distance A. Accordingly, the installation space 36, which is available to the GI mirror 23 on the left-hand side in Figure 4 increases. Therefore, the partial beams 25, 26 reflected by the GI mirrors 23, 24 are spaced apart from one another in the region of the mirrors 23, 24. Figure 5 shows a further embodiment of a deflection mirror assembly 38. The latter has, overall, four GI mirrors 39, 40, 41, 42, the effect of which, in principle, corresponds to that of the two GI mirrors 23, 24 in the embodiments according to Figures 2 to 4. Each one of the GI mirrors 39 to 42 reflects a dedicated partial beam 43, 44, 45, 46 of the overall incident illumination light beam 22. Each one of these partial beams 43 to 46 is deflected at exactly one of the GI mirrors 39 to 42. Here, each individual ray of the overall illumination light beam 22 experiences exactly one reflection.

A deflection angle a is approximately 19° in the deflection mirror assembly 38.

Figure 7 shows a far field 47 of the illumination light 3 at the location of the transmission facet mirror 6 after a deflection by the deflection mirror assembly 38. The far field, which once again was approximately ring- shaped at the outset, is now constructed from four correspondingly mirrored or folded over partial ring portions 52, 53, 54 and 55 as a result of a mirroring effect of the GI mirrors 39 to 42 in four mirror planes 48, 49, 50 and 51 parallel to the xz-plane. These partial ring portions 52 to 55 are once again arranged within the edge contour 6a of the transmission facet mirror 6. Compared to the far field 28 according to Figure 6, a far field intensity distribution of the far field 47 has a greater similarity to the originally approximately ring-shaped far field of the light source 2 downstream of the collector 5.

In Figures 6 and 7, an arrow 56 which respectively emanates from the centre of the far field distribution 28 or 47 respectively marks a point of this far field distribution 28 or 47 which has a maximum distance from this centre on the edge contour 6a of the transmission facet mirror 6 which is impinged upon by the illumination light 3. Since the far field 47 has a greater similarity to the ring-shaped initial intensity distribution of the far field than the far field 28, the arrow 56 has a reduced length when comparing the far fields 28 and 47. The far field 47, which was generated by way of the four GI mirrors 39 to 42, may be correspondingly more expedient than the far field 28 in respect of the facet switching angles required on the transmission facet mirror 6.

Claims

Patent claims

1. Illumination optical unit (8) for illuminating an illumination field (12), in which an object (9) to be imaged is arrangeable,

- comprising at least one facet mirror (6, 7),

comprising a deflection mirror assembly (5b; 34; 37; 38) in the beam path of an illumination light beam (22) upstream of the facet mirror (6, 7),

wherein the deflection mirror assembly (5b; 34; 37; 38) is embodied in such a way that it deflects a centroid ray (S) of the illumination light beam (22) by at least 10°,

wherein the deflection mirror assembly (5b; 34; 37; 38) has at least two mirrors (23, 24; 39, 40, 41, 42) for grazing incidence, which each reflect a dedicated partial beam (25, 26; 43, 44, 45, 46) of the overall illumination light beam (22).

2. Illumination optical unit according to Claim 1, characterized in that the deflection mirror assembly (5b; 34; 37; 38) is arranged downstream of an intermediate focus (5a) in the beam path of the illumination light beam (22).

3. Illumination optical unit according to Claim 1 or 2, characterized in that the deflection mirror assembly (5b; 34; 37; 38) is embodied to cover a numerical aperture of the intermediate focus (5a) of at most 0.3.

4. Illumination optical unit according to one of Claims 1 to 3,

characterized in that a divergence of the overall illumination light beam (22) after reflection at the deflection mirror assembly (5b; 34; 37; 38) corresponds to an effective numerical aperture which is reduced by at least 10% compared to a numerical aperture of the intermediate focus (5 a).

5. Illumination optical unit according to one of Claims 1 to 4,

characterized in that the deflection assembly (38) has more than two mirrors (39 to 42) for grazing incidence.

6. Illumination optical unit according to one of Claims 1 to 5,

characterized in that at least one of the mirrors (23, 24; 39 to 42) for grazing incidence is embodied in such a way that it causes mirroring of a far field intensity distribution (28; 47).

7. Illumination optical unit according to one of Claims 1 to 6,

characterized in that at least one of the mirrors (23, 24; 39 to 42) for grazing incidence is embodied as a hyperboloid mirror.

8. Illumination optical unit according to one of Claims 1 to 7,

characterized in that the partial beams (25, 26) reflected by the mirrors (23, 24) for grazing incidence are spaced apart from one another by a distance (A) in the region of the mirrors (23, 24).

9. Illumination system comprising an illumination optical unit (8)

according to one of Claims 1 to 8 and comprising a collector (5) as first optical element in the beam path of an illumination light source (2) for guiding illumination light (3) to the intermediate focus (5a).

10. Illumination system according to Claim 9, characterized by an

illumination light source (2).

1 1. Optical system comprising an illumination optical unit (8) according to one of Claims 1 to 8 and comprising a projection optical unit (1 1) for imaging at least part of the illumination field (12) into an image field (17).

12. Projection exposure apparatus comprising an optical system according to Claim 1 1 and comprising an illumination light source (2).

13. Method for producing a microstructured component comprising the following method steps:

providing a reticle (9),

providing a wafer (19) with a coating sensitive to the illumination light (3),

- projecting at least a portion of the reticle (9) onto the wafer (19) with the aid of the projection exposure apparatus (1) according to Claim 12,

developing the light-sensitive layer, exposed by the illumination light (3), on the wafer (19).

14. Component, produced according to a method according to Claim 13.