WO2017046136A1

WO2017046136A1 - Illumination optical unit for projection lithography

Info

Publication number: WO2017046136A1
Application number: PCT/EP2016/071653
Authority: WO
Inventors: Ramon Van Gorkom; Bastiaan Matthias Mertens; Stig Bieling; Lars Wischmeier; Manfred Maul; Martin Endres
Original assignee: Carl Zeiss Smt Gmbh
Priority date: 2015-09-15
Filing date: 2016-09-14
Publication date: 2017-03-23
Also published as: TW201723667A; DE102015217603A1

Abstract

An illumination optical unit for projection lithography serves for illuminating an object field (8), in which an object (12) to be imaged is arrangeable, along an illumination beam path. A first facet mirror (6) has first facets (21) for reflecting guidance of illumination light (3) and for arrangement in a used region of a far field of an EUV light source. A second facet mirror (7) serves for reflecting guidance of the illumination light (3) reflected by the first facet mirror (6) to the object field (8). The second facet mirror (7) has second facets (25) for guiding respectively one illumination light partial beam (26) into the object field (8). The first facet mirror (6) is arranged in a field plane (6a) of the illumination optical unit. The second facet mirror (7) is arranged at a distance from a field plane (6a) and from a pupil plane (12b) of the illumination optical unit. The two facet mirrors (6, 7) are arranged in relation to one another in such a way that at least some of the illumination light partial beams (26) are guided over first facets (21) of the first facet mirror (6) with seamlessly connected reflection surfaces. An illumination optical unit without the mandatory use of a MEMS mirror as first facet mirror emerges.

Description

Illumination optical unit for projection lithography

The content of the German patent application DE 10 2015 217 603.7 is incorporated herein by reference.

The invention relates to an illumination optical unit for projection lithography. Furthermore, the invention relates to an optical system comprising such an illumination optical unit, an illumination system comprising such an illumination optical unit, a projection exposure apparatus comprising such an optical system, a method for producing a microstmctured or nanostmctured component, a method for determining a stop body configuration of at least one stop in such an illumination optical unit and a component produced by the production method. An illumination optical unit comprising a transfer optical unit and at least one illumination-predetermining facet mirror, disposed downstream thereof, is known from WO 2015/036226 Al, WO 2010/099807 Al and US 2006/0132747 Al . It is an object of the present invention to develop an illumination optical unit of the type set forth at the outset in such a way that the advantages of such a facet mirror configuration become accessible without it being mandatory to embody the first facet mirror as a MEMS mirror

(microelectromechanical system mirror).

According to the invention, this object is achieved by an illumination optical unit comprising the features specified in Claim 1. What was identified according to the invention is that the concept of an illumination optical unit comprising a first facet mirror arranged in a field plane and a second facet mirror arranged neither in the field plane nor in a pupil plane, i.e. the concept of a specular reflector, does not necessarily require the embodiment of the first facet mirror as a MEMS mirror but that it is possible to embody the first facets with seamlessly connected reflection surfaces for at least some of the illumination light partial beams. Nevertheless, the flexibility of the concept of the specular reflector is maintained hereby. In particular, it is possible to guide all illumination light partial beams over seamlessly connected first facets. The seamlessly connected reflection surfaces of the first facet mirror can have a rectangular embodiment or, e.g. in accordance with an arcuate object field, they can have an arcuate embodiment. Adjacent first facets with a seamlessly connected reflection surface in each case can be spaced apart from one another. The distance between the second facet mirror and the pupil plane or a plane conjugate thereto can be greater than 200 mm, can be greater than 300 mm, can be greater than 400 mm and can also be greater than 500 mm. In principle, the distance can be even greater. Accordingly, the second facet mirror can also be at a distance from a field plane or a plane conjugate thereto, i.e. it can also assume one of the distance values of greater than 100 mm to greater than 500 mm, mentioned above, from this plane. This ensures that an illumination of the object field by way of various second facets does not exclusively, or practically exclusively, have an effect on the illumination angle distribution, but that it also has a notable field-dependent effect.

As an alternative to the distance criterion of the second facet mirror mentioned above, for example in respect of the pupil plane or a plane of the illumination optical unit conjugate thereto as an absolute distance measure, it is also possible to use a parameter P for characterizing a position of the second facet mirror within the illumination optical unit as a measure, said parameter being explained in even more detail in e.g. WO 2009/024 164 A: P = D(SA)/[D(SA) + D(CR)]

Here:

D(SA) is a diameter of a sub-aperture of the illumination light, emanating from a field point, on the second facet mirror,

D(CR) is a maximum spacing of chief rays of the illumination light at the object field, for example measured in a meridional plane, on the facet surface of the second facet mirror. In a field plane of the illumination optical unit, P = 0 applies, since D(CR) is unequal to zero and D(SA) equals zero. In a pupil plane of the

illumination optical unit, P = 1 applies, since D(CR) equals zero and D(SA) is unequal to zero. On account of the distance of the second facet mirror from the pupil plane, the following can apply thereto: P < 0.8, in particular P < 0.7. Moreover, since the second facet mirror is also at a distance from the field plane, the following can apply for this parameter thereof: P > 0.2, in particular P > 0.3.

At least one stop according to Claim 2 renders it possible to adapt the design of the first facet mirror, which, in particular, is standardized, to flexibly predetermined illumination angle distributions for the object field. The stop can ensure provision of a defined illumination of a pupil of the illumination optical unit. Here, in particular, the stop masks illumination light in regions of a pupil, wherein no light should be incident on the object from the direction of the masked pupil regions. Provision can be made of an interchange holder with a plurality of stops for shadowing at least one portion of at least one illumination light partial beam. These stops can be alternately insertable into the beam path of the illumination light. The stop can be arranged adjacent to the first facet mirror. Alternatively, or additionally, such a stop can also be arranged adjacent to the second facet mirror. The stop can be configured to shadow at least individual complete illumination light partial beams. The stop can be configured to shadow a plurality of illumination light partial beams and, in the limit case, even to shadow all illumination light partial beams in portions in any case.

At least one stop body for shadowing a plurality of illumination light partial beams at least in portions, enables a stable configuration of the stop, in which the stop bodies form supporting constituents. Alternatively, each stop body of the stop can respectively shadow exactly one illumination light partial beam, at least in portions. Then, precisely one stop body is assigned to each illumination light partial beam or each facet.

A plurality of stop bodies according to Claim 5 was found particularly flexible for designing the stop. At least one stop body of the stop can have a displaceable design. This displacement can be used to influence a dimension of a surface to be shadowed of the facet assigned to the stop body or else to change an assignment of the stop body to at least one of the facets.

A stop displaceable overall, i.e. on the whole, according to Claim 6 renders it possible to adapt the shadowing effect of the stop bodies to different predetermined illumination settings. Here, the stop is displaceable, in particular, in an arrangement plane of the stop.

Tiltabilities of the first and/or second facets according to Claims 7 and 8 increase a flexibilization of an object field illumination and pupil illumination. In particular, an assignment of the field facets, i.e. the first facets, to the second facets can be predetermined in a flexible manner.

The advantages of an optical system according to Claim 9, of a projection exposure apparatus according to Claim 10 and of a production method according to Claim 1 1 correspond to those which have already been explained above with reference to the illumination optical unit.

A determination method according to Claim 12 enables the use of one and same facet assignment for obtaining different target illumination angle distributions by the appropriate predetermination of the stop body configuration.

The stop configurations for the various target illumination angle distributions emerge in the method according to Claim 13.

The respective target illumination angle distribution can be partly or completely contained within the selected initial illumination angle distribution.

A method according to Claim 14 renders it possible to use the determined stop body configurations within an illumination optical unit according to the invention. The advantages of a microstructured or nanostructured component according to Claim 15 correspond to those which were already explained above, in particular with reference to the production method. When producing the component, use can be made of at least one stop with a stop body configuration generated in accordance with the determination method explained above.

Exemplary embodiments of the invention are explained in greater detail below with reference to the drawing. In said drawing:

Figure 1 shows, very schematically, a projection exposure apparatus for EUV microlithography in a meridional section, comprising a light source, an illumination optical unit and a projection optical unit;

Figure 2 shows a plan view of a field facet mirror of the

illumination optical unit, which constitutes a first facet mirror and which is arranged in a field plane and in an illumination far field;

Figure 3 shows a plan view of a specular facet mirror of the

illumination optical unit, which constitutes a second facet mirror arranged at a distance from, firstly, a field plane and, secondly, a pupil plane of the illumination optical unit.

Figure 4 shows, schematically and in a meridional section, a beam path of a plurality of illumination light partial beams of illumination light, which are respectively guided over first facets of the first facet mirror with seamlessly connected reflection surfaces; shows an illustration similar to Figure 4, wherein each one of the illumination light partial beams is elucidated by precisely one individual ray and in which the effect of the stop with a plurality of stop bodies for shadowing portions of some of the illumination light partial beams is indicated; shows a plan view of an embodiment of a stop with a plurality of stop bodies, which is suitable for shadowing the first facet mirror; shows, in an exemplary manner, a configuration of stop bodies of a stop for shadowing the first facet mirror according to Figure 2 and for generating an "x dipole" illumination setting; shows, in an exemplary manner, a configuration of stop bodies of a stop for shadowing the first facet mirror according to Figure 2 and for generating a "y dipole" illumination setting; shows the illumination far field of the light source, wherein some seamlessly connected reflection surfaces of the first facets of the first facet mirror for respectively guiding an illumination light partial beam are illustrated schematically; Figure 10 shows a portion of the stop with a total of six stop bodies for shadowing the first facets according to Figure 9 in order to generate a target illumination setting, wherein each stop body of the stop shadows, in portions, exactly one illumination light partial beam in each case, i.e. one of the first facets in each case;

Figure 1 1 shows a schematic plan view of a further embodiment of a second facet mirror, wherein the second facets which are assigned to the first facets according to Figure 9 in the stop body configuration according to Figure 10 are highlighted;

Figure 12 shows, in an illustration similar to Figure 10, an alternative configuration of stop bodies in a portion of a stop for generating the target illumination setting, wherein an overall connected or integral stop body shadows, in portions, all six first facets and hence the illumination light partial beams assigned to these first facets; Figure 13 shows, in an illustration similar to Figure 1 1, an

assignment of second facets of the second facet mirror to the first facets of the first facet mirror according to Figure 9 in the stop body configuration according to Figure 12;

Figure 14 shows, in an exemplary manner, three first facets of the first facet mirror with an embodiment of the stop bodies shadowing these first facets in a variable manner; schematically shows a further embodiment of the first facet mirror with a stop with a plurality of stop bodies disposed in front thereof, wherein the stop on the whole is displaceable and depicted in a first stop position; shows the first facet mirror and the stop according to Figure 15 in a second, displaced stop position for generating a different illumination setting compared to the arrangement according to Figure 15; shows a pupil illumination of the illumination optical unit, wherein the pupil illumination serves as a representative of an initial illumination angle distribution which is selected within the scope of determining a stop body configuration of a stop for shadowing the illumination light partial beams;

Figures 18 and 19 show two target illumination angle distributions, once again depicted as pupil illuminations, which emerge from shadowing illumination light partial beams, proceeding from the initial illumination light distribution, wherein these two target illumination angle distributions are completely contained within the initial illumination angle distribution; and

Figure 20 shows, in an illustration similar to Figure 5, a further

embodiment of an illumination optical unit with first facet mirrors with an arcuate, integral embodiment in the meridional section. A microlithographic projection exposure apparatus 1, depicted very schematically and in a meridional section in Figure 1 , includes a light source 2 for illumination light 3. The light source 2 is an EUV light source which generates light in a wavelength range between 5 nm and 30 nm. Here, this can be an LPP (laser produced plasma) light source, a DPP (discharge produced plasma) light source or a synchrotron radiation-based light source, for example a free electron laser (FEL). A transfer optical unit 4 serves to guide the illumination light 3 emanating from the light source 2. Said transfer optical unit includes a collector 5, merely depicted in Figure 1 in respect of its reflective effect, and a transfer facet mirror 6, which is also referred to as first facet mirror or as field facet mirror and described in more detail below. An intermediate focus 5a of the illumination light 3 is arranged between the collector 5 and the transfer facet mirror 6. A numerical aperture of the illumination light 3 in the region of the intermediate focus 5a is e.g. NA = 0.22 or NA = 0.182.

Disposed downstream of the transfer facet mirror 6, and hence of the transfer optical unit 4, is an illumination prescription facet mirror 7, which is also referred to as second or further facet mirror, or as specular facet mirror, and which will likewise be explained in more detail below. The optical components 5 to 7 are constituents of an illumination optical unit 1 1 of the projection exposure apparatus 1. The transfer facet mirror 6 is arranged in a field plane 6a of the

illumination optical unit 1 1. The illumination prescription facet mirror 7 of the illumination optical unit 1 1 is arranged at a distance from the pupil planes and field planes of the illumination optical unit 1 1. Such an arrangement is also referred to as a specular reflector. A reticle 12, which is arranged in an object plane 9 of a downstream projection optical unit 10 of the projection exposure apparatus 1 , is disposed downstream of the illumination prescription facet mirror 7 in the beam path of the illumination light 3. The projection optical unit 10 is a projection lens. The illumination optical unit 1 1 is used to illuminate an object field 8 on the reticle 12 in the object plane 9 in a defined manner. The object field 8 simultaneously constitutes an illumination field of the illumination optical unit 1 1. What holds true in general is that the illumination field has such an embodiment that the object field 8 can be arranged in the illumination field.

Like the transfer facet mirror 6 as well, the illumination prescription facet mirror 7 is part of a pupil illumination unit of the illumination optical unit and serves to illuminate an entrance pupil 12a in a pupil plane 12b of the projection optical unit 10 with the illumination light 3 with a predetermined pupil intensity distribution. The entrance pupil 12a of the projection optical unit 10 can be arranged in front of the object field 8, or else behind the object field 8, in the illumination beam path. Figure 1 shows the case in which the entrance pupil 12a is arranged in an entrance pupil plane 12b downstream of the object field 8 in the illumination beam path.

A Cartesian xyz-coordinate system is used below in order to facilitate the illustration of positional relationships. The x-direction runs perpendicularly to the plane of the drawing into the latter in Figure 1. In Figure 1, the y- direction extends to the right. In Figure 1 , the z-direction extends downwards. Coordinate systems used in the drawings 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.

The object field 8 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 yo and have a distance xo from one another in the x-direction. The bounding arcs can also be embodied as curved portions of ellipses or parabolas. The aspect ratio xo/yo is e.g. 13 to 1. An insert in Figure 1 shows a plan view (not to scale) of the object field 8. An edge form 8a is arcuate. In the case of an alternative and likewise possible object field 8, the edge form thereof is rectangular, likewise with the aspect ratio xo/yo.

The projection optical unit 10 is merely indicated in part and very schematically in Figure 1. An object- field-side numerical aperture 13 and an image-field-side numerical aperture 14 of the projection optical unit 10 are depicted. Further optical components (not depicted in Figure 1) of the projection optical unit 10 for guiding the illumination light 3 between the optical components 15, 16 are situated between these indicated optical components 15, 16 of the projection optical unit 10, which, for example, can be embodied as mirrors that reflect the EUV illumination light 3.

The projection optical unit 10 images the object field 8 into an image field 17 in an image plane 18 on a wafer 19 which, like the reticle 12 as well, is carried by a holder not depicted in any more detail. Both the reticle holder and the wafer holder are displaceable both in the x-direction and the y- direction (scanning direction) by means of appropriate displacement drives. The transfer facet mirror 6 has a plurality of transfer facets 21 , which are also referred to as first facets. The transfer facets 21 are individual mirrors that are switchable between at least two tilt positions. The transfer facets 21 can be embodied as individual mirrors, tiltable in a driven manner about two mutually perpendicular axes of rotation. Alternatively, the transfer facets 21 can also have a non-tiltable design.

The first facets 21 are arranged next to one another largely without gaps in the style of a 2-D grid in such a way that they cover a far field of the light source 2, in which they are arranged, practically without gaps. This arrangement of the first facets 21 is shown in Figure 2 in an exemplary manner. Apart from a central gap and a passage slit 22 in the 9 o'clock position, the first facet mirror covers the light source far field practically without gaps. Altogether, the first facet mirror has seven columns with, in each case, several tens of first facets 21 arranged above one another and, overall, several hundred first facets 21. The first facets 21 serve for reflective guidance of the illumination light 3.

The second facet mirror 7 disposed downstream of the first facet mirror 6 in the beam path of the illumination light 3 has a plurality of second facets 25, the whole arrangement of which is shown in Figure 3 in an exemplary manner. The second facets 25 have a round embodiment. The second facets 25 have a hexagonal close-packed arrangement. An edge contour of the second facet mirror 7 has a stadium-like shape. The second facets 25 can also have a driven tiltable design, as already explained above in

conjunction with the first facets 21.

The two facet mirrors 6 and 7 are arranged in relation to one another in such a way that the partial beams 26 guided by the second facets 25 are respectively guided over the first facets 21 of the first facet mirror 6, wherein each one of these first facets 21 guiding precisely one of the partial beams 26 is designed with seamlessly connected reflection surfaces. These first facets 21 are also referred to as monolithic facets. An x/y-aspect ratio of the first facets 21 can correspond to the x/y-aspect ratio of the object field 8. In accordance with the object field 8, the first facets 21 can have an arcuate embodiment. Alternatively, a rectangular design of the first facets 21 is possible, as shown in e.g. Figure 2. An exemplary beam path of the partial beams 26 of the illumination light 3 is reproduced in Figure 4. In order to simplify the illustration, the beam path is depicted in such a way that it passes through the object plane 9. In reality, use is made of a reflecting reticle 12. Each one of the partial beams 26 is reflected towards the object field 8 by precisely one of the first facets 21 and by precisely one of the second facets 25.

The partial beams 26 have y-extents that differ from one another at the reflection at the first facet mirrors 21, i.e. different diameters in the y- direction. Due to the arrangement of the first facet mirror 6 in a field plane conjugate to the object plane 9, this y-extent distribution of the partial beams 26 on the first facet mirror 6 is imaged onto a corresponding y- extent distribution of the partial beams 26 in the object plane 9. At the same time, the arrangement and the tilt of the second facets 25 ensures that the partial beams 26 impinge not only onto the object field 8 but also on the entrance pupil 12a in accordance with a predetermined illumination setting. The further the second facets are arranged at a distance from a central axis 27 in the unfolded beam path, said central axis extending firstly through the centre of the pupil 12a and secondly through the centre of the object field 8, the smaller the extent is of the illumination light partial beam 26 guided over this second facet 25. The partial beams 26 which are guided by second facets 25 arranged on or in the vicinity of the central axis 27 have the greatest extent. These partial beams, which are denoted by 26_z in Figure 4, impinge on first facets 21_z with the greatest y-extent on the first facet mirror. Since the partial beams 26 are mixed along the beam path thereof between the two facet mirrors 6 and 7 by an appropriate mixed assignment of the facets 21, 25, the first facets 21_z are arranged distributed over the entire y-extent of the first facet mirror 6.

The illumination light partial beams 26_r which are reflected by second facets 25 in the edge region of the second facet mirror 7, i.e. far away from the central axis 27, belong to the first facets 21_r with the smallest y-extent compared to the other first facets 21.

In accordance with the y-extent distribution, explained above, of the partial beams 26 which are transferred to the object field 8 with a predetermined impingement of the entrance pupil 12a, there is also an emergence of an x- extent distribution of the partial beams 26 perpendicular to the plane of the drawing depicted in Figure 4. In the embodiment according to Figure 4, use is correspondingly made of a first facet mirror 6 with first facets 21 which have differently large extents in the x-direction and in the y-direction. However, the different x-extents and y-extents of the first facets 21 which are required for illuminating the reticle 12 with a predetermined illumination of the pupil 12a, i.e. with a predetermined illumination setting, can alternatively also be achieved by appropriate shadowing of first facets 21 which extend further in the x- direction or y-direction. A corresponding embodiment, in which an appropriate adaptation of the x-extents or y-extents of reflecting portions of the first facets 21 is achieved with the aid of stop bodies 28 of a stop 29, is described below on the basis of Figures 5 and 6. Components and functions corresponding to those which were already explained above with reference to figures 1 to 4 have the same reference signs and are not discussed again in detail.

In contrast to the embodiment according to Figure 4, the first facets 21 of the first facet mirror 6 according to Figure 5 each have the same y-extent. Depending on the assignment of the first facet 21 to the second facet 25 of the second facet mirror 7 by way of an appropriate illumination light partial beam 26, there is corresponding shadowing of the x-extent and/or y-extent of the first facet 21 in order to adapt the reflecting x-extent and/or y-extent of this first facet 21 to the combination of object field 8 and pupil 12a to be illuminated. This is elucidated schematically in Figure 5 by respectively one guide ray 26^F of a central object field point. This guide ray 26^F is representative for the respective whole illumination light partial beam 26.

The second field facet 21_r from the left in Figure 5 belongs to an

illumination light partial beam 26_r ^F which is reflected, by a second facet 25_r at the edge, towards the object field 8 into the predetermined entrance pupil 12a. On account of this position at the edge of the second facet 25_r, only a small y-extent of the first facet 21_r can contribute to illuminate the object. It is for this region that a stop body 28_r shadows the field facet 21_r very strongly, namely along a majority of the y-extent thereof. The fourth field facet 21_z from the left in Figure 5 illuminates one of the central second facets 25_z via an illumination light partial beam 26_z. Here, practically the entire y-extent of the field facet 21_z can contribute to the object illumination, which is why this field facet 21_z is practically not shadowed. A stop body 28_z is practically completely retracted from the assigned field facet 21_z.

An intermediate situation is depicted in Figure 5 on the basis of the third field facet 21_m from the right and on the basis of the far right field facet 21m. These two field facets 21_m belong to second facets 25_m which are arranged between second facets 25_r at the edge and central second facets 25_z. The stop bodies 28_m assigned to the first facets 21_m correspondingly cover a mean y-extent range of the first facets 21_m for adapting the illumination.

The shadowing effect is elucidated in an exemplary manner in Figure 5 for the y-dimension of the first facets 21. Alternatively, or additionally, a corresponding shadowing effect may be present in the x-dimension of the first facets 21, as explained in conjunction with Figure 6.

A stop 29 which can be used for the predetermined shadowing of the first facets 21 with shadowing adapted to the desired illumination setting is shown in Figure 6. Nine stop bodies 28 are depicted in an exemplary manner. These are carried by a lattice carrying structure 30, which in turn is carried by a holding frame 31 with a round edge contour. The grid of the lattice carrying structure 30 corresponds to that of the first facet mirror 6, which is merely indicated schematically in Figure 6. Stop carrying struts 32 of the lattice carrying structure 30 extend along intermediate spaces between adjacent first facets 21 in each case such that the holding structure 31 does not attenuate the illumination light 3 reflected by the first facets 21 in an appreciable manner.

The stop bodies 28 are arranged with a very small z-distance from the first facet mirror 6. By way of example, this z-distance lies in the range between 0.1 mm and 10 mm and, in particular, in the range between 0.1 mm and 1 mm.

Seven of the nine stop bodies 28 depicted in Figure 6 are embodied for shadowing, in portions, precisely one first facet 21 and hence one illumination light partial beam 26. Two of the stop bodies 28, which are denoted by 28° in Figure 6, are embodied for shadowing, in portions, a plurality of first facets 21 and hence a plurality of, namely two,

illumination light partial beams 26.

In the stop 29 according to Figure 6, the stop bodies 28_r shadow a majority of the first facet 21_r assigned thereto, namely approximately 80% of the x- extent thereof. In the stop 29 according to Figure 6, the stop bodies 28_z merely shadow a small portion of the entire x-extent of the first facets 21, namely e.g. 10% or 20% of the entire x-extent of the first facets 21.

The two stop bodies 28°, which shadow two adjacent first facets 21, have a symmetric embodiment in the exemplary embodiment according to Figure 6 and in each case shadow approximately the same portion of the x-extent of the two first facets 21 in the case of the two first facets 21. Such a symmetric embodiment is not mandatory. A stop body 28 shadowing a plurality of first facets 21 can also be embodied in such a way that it is embodied as a strongly shadowing stop body 28_r for a first field facet 21 and a weakly shadowing stop body 28_z for another one of the first facets 21. Figures 7 and 8 shown exemplary embodiments for further stops in the style of the stop 29 explained on the basis of Figure 6. Figures 7 and 8 respectively depict those portions of the first facets 21 which are not shadowed. The portions of the first facets 21 shadowed by the stop bodies 28 of the stop 29 according to Figures 7 and 8 as it were represent the interstices between these portions which are not shadowed.

Figure 7 shows a design of the stop 29 for predetermining an entrance pupil 12a in the style of an x-dipole. Such an x-dipole illumination setting is known, for example, from WO 2015/036226 Al .

The x-dipole setting requires relatively strong integral shadowing of the first facet mirror 6. Here, relatively few field facets 21 are only shadowed a little. In the depicted embodiment, this strong shadowing is indebted to the selected start configuration and not mandatory.

Figure 8 shows the configuration of the stop 29 for generating a "y-dipole" illumination setting which, as a matter of principle, is likewise known from WO 2015/036226 Al . Relatively few regions of the first facet mirror 6 need to be shadowed for generating such a y-dipole illumination setting. Practically none of the first facets 21 need to be shadowed entirely. Many of the first facets 21 need not be shadowed or hardly need to be shadowed.

Figures 9 to 13 are used to explain two alternative facet assignments for generating one and same predetermined x-dipole illumination setting, for which different stop body configurations are required in the case of the same set of first field facets 21.

Figure 9 shows a total of six first facets 21 of a further embodiment of a first facet mirror 6 not depicted otherwise. The first facets 21 are arranged in a far field 33 of the light source 2. In contrast to the embodiment according to Figures 2 and 5, the first facets 21 of the first facet mirror 6 according to Figure 9 have x-extents which differ from one another. Thus, the first facets 21 are inherently assigned second facets 25 which are particularly suitable for illuminating a specific initial illumination angle distribution, i.e. a specific initial illumination setting. Additionally, these first facets 21 can still be shadowed by way of stop body configurations of various refinements of stops 29, which is explained on the basis of Figures 10 to 13.

In the embodiment according to Figure 9, the field facets 21 are not strictly aligned column-by-column but are strictly are aligned line -by-line.

Therefore, interstices between the field facets 21 extend continuously along the x-direction but not along the y-direction (scanning direction).

In the first assignment according to Figures 10 and 1 1 , second facets 251 to 25₆ are assigned to the first facets 211 to 21₆. The field facets 211 and 21₆ shadowed least in the x-dimension belong to second facets 251 and 25₆, which are arranged in the vicinity of an intensity impingement maximum for generating the x-dipole illumination setting on the second facet mirror 7. Depending on whether the stop bodies 281 to 28₆ shadow a left-hand or a right-hand x-portion of the field facet 211 to 21₆, a second facet 25 in the region of the left-hand or right-hand intensity impingement region Ii or h on the second facet mirror 7 is selected for the assignment. In the embodiment according to Figures 10 and 1 1 , the facet assignment of the field facets 211 to 21₆ to the second facets 251 to 25₆ is such that each stop body 281 to 28₆ shadows precisely one field facet 211 to 21₆ in portions. Accordingly, each stop body 281 to 28₆ is carried individually by stop carrying struts 32 extending along the x-direction.

In the embodiment according to Figures 12 and 13, there is an assignment of the second facets 251 to 25₆ to the first facets 211 to 21₆ in such a way that respectively one stop body 28i,2^D, 28₃,₄ ^D and 28₅,6^D shadows two field facets 211 and 21₂, 21₃ and 21₄ and also 21₅ and 21₆.

Moreover, the selected facet assignment is such that the stop bodies 28i,₂ ^D, 28₃,4^D and 28₅,6^D overlap in the x-dimension and therefore, altogether, are also connected to one another in a planar fashion by way of the stop carrying struts 32. What emerges overall is a connected stop main body 34, the portions of which form the stop bodies 28 for the six first facets 211 to 2 . Further embodiments of stop bodies 28 for the stop 29 are described on the basis of Figure 14. The stop bodies 28 according to Figure 14 have a stop element 35 which is movable along the x-direction and designed in a manner possible to be rolled up in the style of a shadowing skylight roller blind. The stop element 35 is guided by way of guide rails 36, which extend along the x-direction and are in turn carried by the stop carrying structure 32. A rolling and unrolling drive 37 for each stop element 35 is attached below a permanent shadowing by the stop element 35; this is depicted schematically using dashed lines in Figure 14 for the uppermost stop body illustrated therein. Alternatively, respectively one of the stops 29 with a predetermined stop body configuration can be manufactured as a punched and, in particular, monolithic component, for example made of metal. The stop 29 can also be constructed from a plurality of stop portions which can be exchanged for one another where necessary, each stop portion having a predetermined stop body configuration.

For the purposes of predetermining various illumination settings, provision can be made of an appropriate plurality of stops 29, each with a different stop body configuration, wherein the various stops 29 can be stored in a stop interchange holder 38. Use can be made of an interchange holder, as was described, for example, in conjunction with US 2009/0251677 Al . This is indicated schematically in Figure 1. There, a selected stop 29 is arranged in the beam path of the illumination light 3 upstream of the first facet mirror 6. An interchange drive 39 of the stop interchange holder 38 has a mechanical connection firstly with the selected stop 29 and secondly with the interchangeable stops 29w within a stop magazine 40. Depending on the illumination setting to be selected, the stop interchange holder 38 can be used to select a stop 29 with a predetermined stop body

configuration assigned to this illumination setting and introduce the latter into the beam path of the illumination light 3 upstream of the first facet mirror 6. Figures 15 and 16 show a further embodiment of a first facet mirror 6 with one and same stop 29, which is configured to be displaceable in the x- direction and which is depicted in two different x-positions in the two Figures 15 and 16. Here, the stop 29 is displaceable in the arrangement plane thereof, i.e. in the plane of the drawing of Figures 15 and 16. According to Figures 15 and 16, the first facet mirror 6 is depicted schematically with thirty-eight first facets 21, which are arranged closely packed line -by-line within a round facet carrying body 41. In this case, 22 of the thirty-eight first facets 21 have the same x-extent and the same x/y aspect ratio. Compared thereto, first facets 21 on the edge along the x- direction have a smaller x-extent, which is adapted in each case to the position in relation to the edge of the facet carrying body 41. The stop 29 has a stop body configuration, in which the stop bodies 28 are respectively arranged offset line -by-line in the style of the black squares of a chequerboard pattern.

In the position of the stop 29 according to Figure 15, the configuration of the stop bodies 28 is driven over the arrangement of the field facets 21 in such a way that the vast majority of the field facets 21 are shadowed, approximately over half thereof, along the x-dimension. The resultant illumination light partial beams reflected by non-shadowed field facets 21 have a correspondingly small x-extent and are therefore suitable for illuminating an illumination setting in the style of an x-dipole.

In the stop position according to Figure 16, the stop 29 is shifted to the right by half an x-extent of a field facet 21 in comparison with the position according to Figure 15. Approximately half of the field facets 21 are then shadowed completely and approximately the other half of the field facets 21 are practically not shadowed at all or only shadowed slightly. This results in illumination light partial beams with practically maximal x- extent, which are suitable for illuminating a "y-dipole" illumination setting. Thus, an illumination configuration for, firstly, an x-dipole illumination setting and, secondly, a y-dipole illumination setting can be realized with the aid of one and same displaceable stop 29. In addition to the

displacement of the stop 29, there can also be a change in an assignment of the first facets 21 to the second facets 25 and, correspondingly, a beam guidance of the illumination light partial beams 26 for the purposes of realizing a corresponding change in the illumination setting. Such a change in the beam guidance assumes that the facets 21 and 25 are embodied in a driven tiltable and, in particular, switchable manner.

For the purposes of displacing the stop 29, the latter has a mechanical functional connection to a displacement drive 42, which is schematically indicated in Figure 15. A displacement of the stop 29 along the x- dimension and/or along the y-dimension is possible by way of the displacement drive 42.

The following procedure can be undertaken when determining a stop body configuration for at least one of the stops 29: Initially, an initial

illumination angle distribution, i.e. an initial illumination setting, of an object field illumination is selected, from which at least one target illumination angle distribution emerges by shadowing illumination light partial beams 26, wherein the target illumination angle distribution is completely contained within the initial illumination angle distribution, Examples of such illumination angle distributions are shown in Figures 17 to 19, which in each case reproduce, for an object field point, an intensity distribution of an illumination of an entrance pupil 12a with the

illumination light 3, which is subdivided into a plurality of illumination light partial beams 26. This intensity distribution is likewise depicted in xy- coordinates, to which the pupil coordinates sigma_x, sigma_y are assigned.

Here, Figure 17 shows an annular illumination setting, in which the entrance pupil 12a is illuminated in a ring-shaped manner along the edge.

Figure 18 shows an x-dipole illumination setting, which is achieved by shadowing an upper portion and a lower portion of the pupil illumination according to Figure 17.

Figure 19 correspondingly shows a y-dipole illumination setting, which is achieved by shadowing right and left portions of the intensity distribution according to Figure 17. As an alternative to the arrangement in which the target illumination angle distribution is contained completely within the initial illumination angle distribution, the initial illumination angle distribution can also be selected in such a way that the target illumination angle distribution is partly contained within the initial illumination angle distribution.

Within the scope of the stop body configuration determination method, the shadowing for each illumination light partial beam 26 required for generating the two target illumination angle distributions is determined after this selection. This is carried out in the case of a predetermined assignment of the field facets 2 (i = 1 to N, N: number of the first facets) to the second facets 25j (j = 1 to M, M: number of the second facets).

Subsequently, each stop body, assigned to the respective illumination light partial beam, is designed in such a way that the shadowing determined in advance emerges for each illumination light partial beam 26 using the formed stop body 28.

In an illustration similar to Figure 5, Figure 20 shows a further embodiment of a first facet mirror 6 and an associated stop 29, which can be used in place of these components in the embodiment according to Figure 5.

Both the field facet mirror 6 and the stop 29 are attached to a concavely curved main body in the embodiment according to Figure 20. The basic curvatures of the first facet mirror 6 and of the stop 29 with the stop bodies 28 according to Figure 20 are matched to one another in such a way that a distance between the stop bodies 28 and the assigned first facets is minimized. In respect of further details of possible embodiments of the transfer facet mirror 6, of the specular facet mirror 7 and of the projection optical unit 10, reference, apart from the monolithic design of the first facets 21, is made to WO 2015/036266 Al and WO 2010/099 807 A.

The reticle 12 and the wafer 19 are initially provided for producing a microstructured component, in particular a highly integrated semiconductor component, for example a memory chip, with the aid of the projection exposure apparatus 1. Then, the illumination setting to be provided, for example an x-dipole illumination setting, is selected and set by

predetermining a corresponding assignment of the facets 21, 25 and, in particular, by predetermining a corresponding stop body configuration. Subsequently, a structure on the reticle 12 is projected onto a light- sensitive layer on the wafer 19 with the projection optical unit of the projection exposure apparatus 1. Here, firstly the reticle 12 and secondly the wafer 19 are scanned in a manner synchronized to one another along the scanning direction y. By developing the light-sensitive layer, a micro structure is then generated on the wafer 19 and the microstmctured or nano structured component is generated therefrom.

Claims

Patent claims

1. Illumination optical unit (1 1) for projection lithography for

illuminating an object field (8), in which an object (12) to be imaged is arrangeable, along an illumination beam path,

- comprising a first facet mirror (6) with first facets (21) for reflecting guidance of illumination light (3) and for arrangement in a used region of a far field (33) of an EUV light source (2),

- comprising a second facet mirror (7) for reflecting guidance of the illumination light (3) reflected by the first facet mirror (6) to the object field (8),

- wherein the second facet mirror (7) has second facets (25) for

guiding respectively one illumination light partial beam (26) into the object field (8),

- wherein the first facet mirror (6) is arranged in a field plane (6a) of the illumination optical unit (1 1),

- wherein the second facet mirror (7) is arranged at a distance from a field plane and from a pupil plane (12b) of the illumination optical unit (1 1),

- wherein a distance between the second facet mirror (7) and the pupil plane (12b) or a plane conjugate thereto is greater than 100 mm,

- wherein the two facet mirrors (6, 7) are arranged in relation to one another in such a way that at least some of the illumination light partial beams (26) are guided over first facets (21) of the first facet mirror (6) with seamlessly connected reflection surfaces.

2. Illumination optical unit according to Claim 1, characterized by at least one stop (29) for shadowing at least one portion of at least one illumination light partial beam (26).

3. Illumination optical unit according to Claim 2, characterized in that the stop (29) is configured to shadow at least one portion of a plurality of the illumination light partial beams (26).

4. Illumination optical unit according to Claim 2 or 3, characterized in that a stop body (28D) of the stop (29) is configured to shadow a plurality of illumination light partial beams (26), at least in portions.

5. Illumination optical unit according to one of Claims 2 to 4,

characterized in that the stop (29) has a plurality of stop bodies (28) for shadowing at least one portion of at least one illumination light partial beam (26) in each case.

6. Illumination optical unit according to one of Claims 2 to 5,

characterized in that the stop (29) is displaceable on the whole.

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

characterized in that the first facets (21) are tiltable in a driven manner.

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

characterized in that the second facets (25) are tiltable in a driven manner.

9. Optical system comprising an illumination optical unit according to one of Claims 1 to 8 and comprising a projection optical unit (10) for imaging the object field (8) into an image field (17), in which a wafer (19) is arrangeable.

10. Projection exposure apparatus comprising an optical system according to Claim 9 and a light source (2).

1 1. Method for producing a microstmctured component, comprising the following method steps:

providing a reticle (12),

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

- proj ecting at least a portion of the reticle ( 12) onto the wafer ( 19) with the aid of the projection exposure apparatus (1) as claimed in claim 10,

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

12. Method for determining a stop body configuration of at least one stop (29) in an illumination optical unit according to one of Claims 2 to 8, comprising the following steps:

- selecting an initial illumination angle distribution of an object field illumination, from which at least one target illumination angle distribution emerges by shadowing illumination light partial beams (26), wherein the target illumination angle distribution is partly or completely contained within the initial illumination angle distribution,

- determining the shadowing of each illumination light partial beam

(26) required for generating the target illumination angle distribution,

- designing each stop body (28), assigned to the respective

illumination light partial beams (26), in such a way that the shadowing determined in advance emerges for each illumination light partial beam (26) using the stop body (28).

13. Method according to Claim 12, characterized by the following steps:

- selecting an initial illumination angle distribution of the object field illumination, from which a plurality of target illumination angle distributions emerge by shadowing illumination light partial beams (26), wherein the target illumination angle distribution is partly or completely contained within the initial illumination angle distribution,

- determining the shadowings of each illumination light partial beam

(26) required for generating the target illumination angle distributions,

- designing each stop body (28), assigned to the respective

illumination light partial beam (26), in such a way that the shadowing, determined in advance, for generating respectively one of the target illumination angle distributions emerges for each illumination light partial beam (26) using the stop body (28), for the prescription of a stop configuration of a stop (29) assigned to this target illumination angle distribution.

14. Method according to Claim 13, characterized by equipping an

interchange holder (38) with the stops (29, 29w) with the stop body configurations assigned to the various target illumination angle distributions.

15. Component, produced according to a method according to Claim 1 1.