Illumination optics for projection lithography and methods for monitoring such illumination optics

Abstract

An illumination optic (11) for projection lithography has a transmission facet mirror (6), an illumination specification facet mirror (7), and a monitoring device (28). The latter has at least one spatially resolving monitoring sensor (29) and a satellite facet (30), which belongs to the transmission facet mirror (6) and is each assigned to exactly one monitoring transmission facet (21). The satellite facet (30) is oriented such that monitoring light (3) from a monitoring light source (2) is guided via the satellite facet (30) and a monitoring illumination control facet (25), which is assigned to the monitoring transmission facet (219) via an illumination channel (27), along a monitoring light channel (31) to the monitoring sensor (29). This results in an illumination optic in which a tilting of illumination control facets of an illumination control facet mirror can be effectively monitored.

Description

The invention relates to an illumination optical unit for projection lithography. The invention further relates to a method for monitoring such an illumination optical unit, to an optical system having such an illumination optical unit, to a projection exposure apparatus having such an optical system, to a method for producing a micro- or nanostructured component having such a projection exposure apparatus, and to a micro- or nanostructured component produced using this method.An illumination optical system for projection lithography is known from DE 10 2015 208 512 A1 and the references specified therein.It is an object of the present invention to further develop an illumination optical unit of the type mentioned at the beginning in such a way that a tilt of illumination specification facets of an illumination specification facet mirror can be effectively monitored.This object is achieved according to the invention by an illumination optical system having a monitoring device having the features specified in claim 1 and by a monitoring method having the features specified in claim 10.According to the invention, it has been recognized that, when at least one satellite facet is used, tilts of the illumination specification facet to be monitored are translated into corresponding displacements of the monitoring light channel which is guided via the respective satellite facet. These displacements of the monitoring light channel can be detected by sensors as corresponding displacements of a light channel location of incidence on the spatially resolving monitoring sensor of the monitoring device and can thus be monitored. Spatial differences between a target point of incidence of the monitoring light channel and an actual point of incidence of the monitoring light channel on the sensor are a measure of tilting of the illumination specification facet to be monitored. In particular, mechanical and / or, assuming a corresponding actuator system of the illumination specification facet, capacitive and / or thermal drifts of the illumination specification facets can be effectively monitored in this way. The monitoring light source may be identical to the illumination light source, i.e. to the light source which generates the illumination light for projection lithography. The transmission facet mirror can be arranged in a field plane of a beam path of the illumination light. Parallel processing of a plurality of monitoring light channels and thus simultaneous monitoring of a plurality of illumination specification facets can be provided by means of the monitoring device of the illumination optical unit. The illumination specification facet mirror can be arranged in or close to a pupil plane of an optical path of the illumination light. Alternatively, the illumination specification facet mirror can be arranged at a distance from a pupil plane of a beam path of the illumination light.The transfer facets of the transfer facet mirror can be tiltable actuatorically. This can be used to specify a respective illumination channel for the illumination light which is guided toward the object field via in each case one of the transmission facets and an illumination specification facet assigned via a respective tilting position of this transmission facet.The at least one monitoring sensor of the monitoring device can provide a sensor surface in the range between 10 mm x 10 mm and 100 mm x 100 mm.The illumination light source that generates the illumination light can be used in particular as the monitoring light source.The monitoring device can include, for example, 10,000 satellite facets.An embodiment of the illumination optics according to claim 2 enables a monitoring of a corresponding plurality of illumination specification facets assigned to the satellite facets and to be monitored. Each illumination specification facet to be monitored can be assigned a satellite facet of the monitoring device via a corresponding monitoring transmission facet. Monitoring in particular all illumination specification facets of the illumination optical unit via corresponding satellite facets of the monitoring device is possible.A spatial proximity between the respective satellite facet and the monitoring transmission facet assigned thereto according to Claim 3 ensures that comparable causes of drift, which originate, for example, on account of far-field illumination of the transmission facet mirror, can be monitored. A distance between the satellite facet and the monitoring transmission facet assigned to it can correspond to a typical extent of a transmission facet. If the transmission facet mirror is configured in modules, the satellite facet on the one hand and the monitoring transmission facet assigned to it on the other hand can be selected such that both facets belong to the same module of the transmission facet mirror.An arrangement of the at least one monitoring sensor according to claim 4 has proven to be advantageous due to corresponding installation space requirements. Two monitoring sensors can be arranged next to the shorter object field sides, i.e. next to the shorter field extents of the object field, such that the object field lies between the two monitoring sensors.The embodiment of the monitoring device with a separate monitoring light source according to claim 5 can extend processing possibilities of the monitoring device. The monitoring light beam path of the separate monitoring light source can be coupled into a light guide of the illumination optical unit in the region of an intermediate focus. Alternatively or additionally, the illumination light source can be used as a monitoring light source.Monitoring light of a plurality of wavelengths according to Claim 6 enable parallel processing of the monitoring light channels assigned to these wavelengths. At least one spectrally selective monitoring sensor can be used here. Part of the wavelength-selective monitoring sensor can be a diffractive element, in particular a grating. Alternatively or additionally, a wavelength-selective coating can belong to the wavelength-selective monitoring sensor, in particular an interference coating. The monitoring sensor, which is then designed to be wavelength-selective, can have a filter that acts as a function of wavelength. Such a monitoring sensor can be designed in the manner of a Bayer sensor, that is to say in the manner of an image sensor which operates according to the concept of a Bayer matrix. Pixels of such an image sensor can be assigned to different colors of a wavelength range to be covered, analogous to the RGB division of the Bayer matrix.A transfer facet mirror and / or an illumination specification facet mirror according to Claim 7 can be embodied as a MEMS mirror. The subdivision of the transmission facets and / or the illumination specification facets into a plurality of individual mirrors, in particular into a plurality of individual mirrors of a MEMS mirror device, increases flexibility of use of the illumination optical unit. When monitoring illumination specification facets, which in turn are constructed from a plurality of illumination specification individual mirrors, the advantages of the monitoring device are particularly important.With the aid of a monitoring device according to claim 8, an effective tilt position monitoring of all individual illumination mirrors belonging to an illumination specification facet is possible. In this case, these illumination specification individual mirrors can be scanned via the monitoring scanning unit.An embodiment of the monitoring light source as a light source grid according to claim 9 enables parallel processing for detecting tilts of individual illumination-specification mirrors of an illumination-specification facet to be monitored as an alternative or additional possibility for monitoring instead of the monitoring scanning unit mentioned above. In the case of the light source grid, parallel processing by the monitoring device is then possible.The advantages of a monitoring method according to claim 10 correspond to those explained above with reference to the illumination optics with the monitoring device. The monitoring of the illumination specification facets to be monitored can take place sequentially and / or in parallel. During the monitoring, a monitoring scanning unit can be used for the sequential monitoring of corresponding illumination specification facets and / or illumination specification individual mirrors, as already explained above. During the monitoring, a light source grid of a monitoring light source can be effected, as likewise already explained above, for the parallel tilt position monitoring of a plurality of illumination specification facets and / or of a plurality of illumination specification individual mirrors. During the comparison, techniques of cross-correlation can be used within the scope of the monitoring method.The monitoring method can be carried out in parallel to the useful operation of the illumination optical unit. Alternatively or additionally, the monitoring method can be carried out in operating pauses of the projection exposure apparatus to which the illumination optical unit belongs. The monitoring method can be used to monitor, in particular, static alignment errors, manufacturing or indication errors and general malpositions of the illumination specification facets to be monitored. Alternatively or additionally, dynamic tilt position deviations can be monitored, for example an effect of thermal effects and / or a change in the illumination specification facets or a facet actuator system caused by the use duration.In the measurement and comparison of the points of incidence, diffraction effects which can occur along the monitoring light channels can be taken into account.The assignment method according to claim 11 specifies boundary conditions which can improve a quality of the monitoring result. If a minimum distance between predetermined target points of impingement of different monitoring light channels is maintained on the monitoring sensor, the corresponding monitoring light channels can be reliably kept apart when evaluating the comparison result of the monitoring method and thus be unambiguously assigned to the illumination specification facets to be monitored via satellite facets and thus to the illumination specification facets to be monitored. If a maximum distance is maintained between the satellite facet and the monitoring transmission facet assigned to it, it is ensured that distance-related deviations between the tilting position influences on the satellite facet on the one hand and on the monitoring transmission facet assigned to it on the other hand are not undesirably high.Advantages of an optical system according to claims 12 and 13, a projection exposure apparatus according to claim 14, a production method according to claim 15 and a nanostructured component according to claim 16 correspond to those already explained above with reference to the illumination optics according to the invention and the monitoring method according to the invention.The substrate may be a wafer. In particular, a structured semiconductor component, in particular a microchip, for example a memory chip, can be produced.Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. In these show: FIG. 1 shows a highly schematic meridional section of a projection exposure apparatus for EUV microlithography with a light source, an illumination optical unit and a projection optical unit, wherein a plan view of an object field of the projection exposure apparatus is illustrated in an insert; FIG. 2 shows schematically and likewise in meridional section a beam path of selected individual beams of illumination light within the illumination optics according to FIG. 1, starting from an intermediate focus up to a reticle or object arranged in the object plane of the projection optics in the region of the illumination or object field; FIG. 3 shows a plan view of a first facet mirror of the illumination optical unit, which is arranged in a field plane of the illumination optical unit and in an illumination far field of the light source and is also referred to as a transmission facet mirror or as a field facet mirror, wherein an array arrangement of single mirror units, which are each formed from a sub-array of single mirrors of the first facet mirror, which sub-array is not visible in FIG. 3, is illustrated; FIG. 4 is an enlarged view, by way of example and more in detail, but still schematically, of one of the individual mirror units in comparison with FIG. 3 embodied as a sub-array of the individual mirrors; FIG. 5 shows a plan view of an illumination-specification facet mirror of the illumination optical unit, which is arranged at a distance from a pupil plane of the illumination optical unit and is also referred to as a second facet mirror; FIG. 6 schematically shows the illumination optics of the projection exposure apparatus including a monitoring device, wherein an illumination channel for illuminating the object is dotted via a transmission facet of the transmission facet mirror and an illumination specification facet of the illumination specification facet mirror, and a monitoring light channel for acting on a monitoring sensor of the monitoring device is shown in solid form via a satellite facet of the transmission facet mirror and the illumination specification facet of the illumination channel; FIG. 7 shows a further embodiment of the illumination optical unit with components of a further embodiment of the monitoring device, having a monitoring light source for monitoring light which is separate from the light source for the illumination light and is guided along a monitoring light channel over a satellite facet of the transmission facet mirror; FIG. 8 shows a perspective view of a further embodiment of the illumination optical system with a further embodiment of the monitoring device, having three monitoring light sources which each generate monitoring light of a specific wavelength, wherein the wavelengths generated by the monitoring light sources differ; FIG. 9 shows, in a representation similar to FIG. 6, a further embodiment of the monitoring device with a monitoring scanning unit which is in signal connection with an actuator system of the satellite facet highlighted in FIG. 9 ; FIG. 10 shows, in a representation similar to FIG. 3, a plan view of the transfer facet mirror, wherein a distribution of transfer individual mirrors used for illuminating the object with a specific illumination setting and transfer individual mirrors unused for this illumination, which are each distributed over an entire useful surface of the transfer facet mirror, is emphasized; FIG. 11 is a plan view of the object field of the projection exposure apparatus, which is rectangular in this case, and also, on the right and left thereof, in each case a sensor surface of a spatially resolving monitoring sensor of the monitoring device, wherein points of impingement of monitoring light channels in the manner of the monitoring light channel according to FIG. 6 on the sensor surfaces are shown schematically; FIG. 12 shows one of the sensor surfaces of the monitoring device, wherein a distribution of points of incidence of the monitoring light channels is illustrated in the manner of FIG. 11 after carrying out an assignment method of satellite facets to illumination specification facets to be monitored, wherein the assignment method leads to a sufficient spatial distance between the points of incidence; FIG. 13 shows, in a representation similar to that according to FIG. 9, an embodiment of the monitoring device with a monitoring light source which is embodied as a light source grid, wherein all light sources of the light source grid are activated and wherein a monitoring light channel of the monitoring device starting from a center of the light source grid is illustrated; FIG. 14 shows an operating situation of the monitoring device according to FIG. 13 in a representation similar to FIG. 13, wherein only a single light source of the light source grid is active.A projection exposure apparatus 1 for microlithography, which is illustrated in a highly schematic manner in FIG. 1 and in a meridional section, has a light source 2 for illumination light 3. 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 transmission optics 4 is used for guiding the illumination light 3, starting from the light source 2, and this optics have a collector 5, which is illustrated in FIG. 1 only with regard to its reflecting effect, and a transmission facet mirror 6, which is described in more detail below and is also referred to as a first facet mirror or as a field facet mirror. Between the collector 5 and the transmission facet mirror 6, an intermediate focus 5 aof the illumination light 3 is arranged. A numerical aperture of the illumination light 3 in the region of the intermediate focus 5 ais, for example, NA=0.182. Arranged downstream of the transfer facet mirror 6 and thus of the transfer optics 4 is an illumination-specification facet mirror 7, which is also referred to as a second or further facet mirror and is likewise explained in more detail below. The optical components 5 to 7 are components of an illumination optical unit 11 of the projection exposure apparatus 1.The transmission facet mirror 6 is arranged in a field plane of the illumination optical unit 11.The illumination-specification facet mirror 7 of the illumination optical unit 11 is arranged at a distance from pupil planes of the illumination optical unit 11. Such an arrangement is also referred to as a specular reflector. Alternatively, the illumination specification facet mirror 7 can also be arranged in the region of a pupil plane of the illumination optical unit 11 and is then referred to as a pupil facet mirror.Arranged downstream of the illumination specification facet mirror 7 in the beam path of the illumination light 3 is a reticle 12 which is arranged in an object plane 9 of a downstream projection optical unit 10 of the projection exposure apparatus 1. The projection optical unit 10 is a projection objective. With the illumination optics 11, an object field 8 on the reticle 12 is illuminated in a defined manner in the object plane 9. The object field 8 simultaneously represents an illumination field of the illumination optical unit 11. In general, the illumination field is designed such that the object field 8 can be arranged in the illumination field.The illumination-specification facet mirror 7 is, like the transmission facet mirror 6, part of a pupil illumination unit of the illumination optical unit and serves for illuminating an entry pupil 12 ain a pupil plane 12 bof the projection optical unit 10 with the illumination light 3 having a predefined pupil intensity distribution. The entrance pupil 12 aof the projection optical unit 10 can be arranged in the illumination beam path upstream of the object field 8 or else downstream of the object field 8.FIG. 1 shows the case in which the entry pupil 12 ais arranged in the illumination beam path downstream of the object field 8. A pupil distance PA of the second facet mirror 7 from the pupil plane 12 bis obtained in this case as the sum of a z-distance PA 1 of the second facet mirror 7 from the object plane 9 and the z-distance PA 2 of the object plane 9 from the pupil plane 12 b. Thus, PA=PA1+PA2 applies. The pupil distance PA can alternatively also be measured in the beam direction.To facilitate the representation of positional relationships, a Cartesian xyz-coordinate system is used below. The x-direction extends in FIG. 1 perpendicularly to the plane of the drawing into the latter. The y-direction extends to the right in FIG. 1. The z-direction runs downward in FIG. 1. Coordinate systems used in the drawing each have x-axes running parallel to one another. The course of a z-axis of these coordinate systems follows a respective main direction of the illumination light 3 within the respectively observed figure.The object field 8 has an arcuate or partially circular shape and is bounded by two circular arcs parallel to one another and two straight side edges which run 0 in the y direction with a length y and are at a distance x 0 to one another in the x direction. The aspect ratio x 0 / y 0 is 13 to 1. an insert of FIG. 1 shows a top view, not to scale, of the object field 8. In an alternative and likewise possible object field 8, its boundary shape is rectangular, likewise with aspect ratio x 0 / y 0.During a projection exposure, the reticle 12 is displaced along an object displacement direction y through the object field 8.The projection optical unit 10 is indicated only partially and strongly schematically in FIG. 1. An object field-side numerical aperture 13 and an image field-side numerical aperture 14 of the projection optical unit 10 are illustrated. The image field-side numerical aperture 14 can lie in the range between 0.2 and 0.8 and can be, for example, 0.3, 0.33, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7 or else 0.75. Between indicated optical components 15, 16 of the projection optical unit 10, which can be designed, for example, as mirrors reflecting for the EUV illumination light 3, there are further optical components of the projection optical unit 10, not shown in FIG. 1, for guiding the illumination light 3 between these optical components 15, 16.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, is carried by a holder, not shown in detail. Both the reticle holder and the wafer holder can be displaced both in the x direction and in the y direction by means of corresponding displacement drives. A structural space requirement of the wafer holder is illustrated in FIG. 1 at 20 as a rectangular box. The installation space requirement 20 is cuboidal with an extent in the x-, y- and z-directions which is dependent on the components to be accommodated therein. The installation space requirement 20 extends, for example, from the center of the image field 17, in the x-direction and in the y-direction by 1 m. The installation space requirement 20 extends, for example, from the image plane 18 in the z-direction too by 1 m. The illumination light 3 must be guided in the illumination optical unit 11 and the projection optical unit 10 in such a way that it is guided past the installation space requirement 20, respectively.The transfer facet mirror 6 has a plurality of transfer facets 21, also referred to as first facets. The transfer facet mirror 6 can be embodied as a MEMS mirror. The transfer facets 21 are individual transfer mirrors ES that can be switched at least between two tilting positions (cf. for example FIGS. 7 and 8 ) and are designed as micromirrors. The transfer facets 21 can be designed as tiltable micromirrors driven about two mutually perpendicular axes of rotation.Of these transfer facets 21, a line with a total of nine transfer facets 21 is schematically shown in the yz section according to FIG. 2, which are indexed from left to right by 21 1 to 21 9 in FIG. 2.In fact, the transfer facet mirror 6 has a substantially larger plurality of the transfer facets 21. The individual transfer mirrors ES are grouped into the transfer facets 21 (cf. also in this regard for example FIGS. 7 and 13 ). These transfer facets 21 are also referred to as single mirror groups, virtual field facets and virtual facet groups, respectively.Each of the transmission facets 21 guides a portion of the illumination light 3, which is also referred to as illumination light sub-bundle, via an illumination channel for partial or complete illumination of the object field 8. In principle, each of the illumination specification facets 25 can in turn be constructed in turn from a plurality of individual mirrors ES (cf. for example FIG. 7 ). The illumination specification facets 25 are also referred to below as second facets. If the second facet mirror 7 is arranged in the region of a pupil plane of the illumination optical unit 11, the illumination specification facets 25 are also referred to as pupil facets.A single mirror group or transfer facet 21 is a group of the single mirrors ES of the first facet mirror 6, which is imaged into the object field 8 by the same second facet 25.For further details of possible embodiments of the transfer facet mirror 6 and of the projection optical unit 10, reference is made to WO 2010 / 099 807 A.The illumination-specification facet mirror 7 is part of an optical system via which transmission facets 21 are imaged at least into sections or subfields of the object field 8. At least some of the illumination specification facets 25 optionally illuminate only a sub-region or sub-field of the object field 8. These sub-fields are shaped very individually and also depend on the desired illumination direction distribution (pupil shape) in the object field 8, i.e. the illumination setting. The illumination specification facets 25 are therefore illuminated by virtual field facets of very different shapes, the shape of which corresponds precisely to the shape of the respective sub-field to be illuminated. Each illumination specification facet 25 also contributes to different regions of the pupil depending on the location in the object field 8.The illumination specification facet mirror 7 can be designed as a MEMS mirror in particular when each of the illumination specification facets 25 is constructed from a plurality of individual mirrors ES. The illumination specification facets 25 are micromirrors switchable between at least two tilt positions. The illumination specification facets 25 are designed as micromirrors which can be tilted in a two-dimensional manner and in particular can be tilted in a continuously driven manner and independently about two tilting axes which are perpendicular to one another, that is to say can be set into a multiplicity of different tilting positions.An example of a predefined assignment of individual transfer facets 21 to the illumination specification facets 25 is illustrated in FIG. 2. The illumination specification facets 25 assigned to the transmission facets 21 1 to 21 9 in each case are indexed in accordance with this assignment. The illumination specification facets 25 are illuminated from left to right on the basis of this assignment in the order 25 6, 258, 253, 254, 251, 257, 255, 252 and 25 9.Indices 6, 8 and 3 of facets 21, 25 include three illumination channels VI, VIII and III, which illuminate three object field points OF 1, OF 2, OF 3, which are numbered from left to right in FIG. 2, from a first illumination direction. The indices 4, 1 and 7 of the facets 21, 25 belong to three further illumination channels IV, I, VII, which illuminate the three object field points OF 1 to OF 3 from a second illumination direction. The indices 5, 2 and 9 of the facets 21, 25 belong to three further illumination channels V, II, IX, which illuminate the three object field points OF 1 to OF 3 from a third illumination direction. Corresponding illumination light sub-beams 3 1 to 3 9 are assigned to the illumination channels I to IX.The illumination directions,the illumination channels VI, VIII, III,the illumination channels IV, I, VII andthe illumination channels V, II, IXThe respective components are assigned to them, are identical. The assignment of the transmission facets 21 to the illumination specification facets 25 is therefore such that telecentric illumination of the object field 8 results in the illumination example illustrated in the figure.The illumination of the object field 8 via the transmission facet mirror 6 and the illumination-specification facet mirror 7 can take place in the manner of a specular reflector. The principle of the specular reflector is known from US 2006 / 0132747 A1.FIG. 3 shows a plan view of an embodiment of the first facet mirror 6, which has a regular array arrangement of individual mirror units 26 which are bounded squarely in FIG. 3. Each of the individual mirror units 26 is designed as a sub-array of N x M of the individual mirrors ES. This sub-array has a plurality of array lines extending along a line direction corresponding to a bisector of the xy-coordinate system.Some of the mutually adjacent array lines are offset with respect to one another by a part of an extent of one of the individual mirror units 26, in particular by half of this extent of the respective individual mirror unit 26 along the array line. Depending on the embodiment of the facet mirror 6, such an offset can be completely omitted, resulting in an array arrangement composed completely of rows and columns. Alternatively, all array lines may be offset from each other. Different amounts of offset between different, adjacent array parts are also possible depending on the design of the facet mirror 6 and depending on the requirements placed on positioning the individual mirror units 26.The first facet mirror 6 is designed for arrangement in a useful region of a far field of the light source 2.Figure 4 shows one of the single mirror units 26 still schematically, but more in detail. The illustration shows a subdivision of the single mirror unit 26 into the sub-array of, in this case, 6 x 6 of the single mirrors ES. Each of the individual mirror units 26 thus has 36 the individual mirrors ES in the embodiment shown. In the example according to FIG. 4, N=6 and M=6. N and M can be the same, can be different and can each lie in the range between 2 and 64, for example at 4, 8, 16, 32 or 64. Values other than powers of two are also possible for N and M, for example 25 or 50.In the embodiment shown in FIG. 3, the first facet mirror 6 has an arrangement of the individual mirror units 26 within a circular envelope. Alternatively, the first facet mirror 6 can also have the individual mirror units 26 within an elliptical, rectangular or else polygonally bordered envelope.In each case one of the individual mirror units 26 can contain a plurality of complete or partial individual mirror groups which guide the illumination light 3 to different second facets 25 and are imaged in the object field 8 in a manner overlapping one another. The individual mirror groups, i.e. the transmission facets 21, can extend over a plurality of the individual mirror units 26.FIG. 5 again shows an embodiment of the second facet mirror 7 in a plan view.The second facets 25 of the second facet mirror 7 are each embodied in a circular-edged manner and are present in the form of a hexagonally densest packing. Alternatively to circularly bordered second facets 25, rectangular or polygonal, in particular hexagonal, bordered second facets 25 can also be present. The second facets 25 can in turn be embodied as individual mirror units in the manner of the individual mirror units of the first facet mirror 6 and in this case be divided into a plurality of individual mirrors in the manner of the individual mirrors ES. In principle, a structure of the second facet mirror 7, as far as the subdivision into individual mirrors and individual mirror units is concerned, can correspond to the structure of the first facet mirror 6.In the embodiment according to FIG. 5, each of the second facets 25 can also be embodied as a monolithic facet.The second facets 25 are arranged in the case of the second facet mirror 7 within an elliptically bordered envelope. Alternatively, other envelope shapes are also possible here, for example a circular envelope, a rectangular envelope and also a polygonally bordered envelope.FIG. 6 schematically shows an embodiment of the illumination optical unit 11. components and functions corresponding to those already explained above with reference to FIGS. 1 to 5 have the same reference numerals and are not discussed in detail again.FIG. 6 illustrates, dotted, a profile of an illumination channel 27 between the light source 2 or the intermediate focus 5 a, a selected transmission facet 21 of the transmission facet mirror 6, an illumination specification facet 25 assigned to this transmission facet 21, and the object field 8 on the reticle 12. The transmission facet 21 is transferred into the object field 8 via the illumination channel 27 in such a way that either the illumination channel 27 impinges on the entire object field 8 or a sub-field of the object field 8, depending on the grouping selection of the individual mirrors ES which belong as an individual mirror group to the respective transmission facet 21. Such an grouping of the individual mirrors ES, so that in particular the edge contour of the transmission facet 21 according to FIG. 6 results, is not illustrated in FIG. 6.FIG. 6 also illustrates a monitoring device 28 of the illumination optical unit 11. the monitoring device 28 includes a spatially resolving monitoring sensor 29 which is designed as a PSD, CMOS or CCD array having a multiplicity of sensor pixels, for example 10,000 x 10,000 sensor pixels. The spatially resolving monitoring sensor 29 can also have a significantly smaller number of sensor pixels, for example 10 x 10, 100 x 100 or 1,000 x 1,000. An aspect ratio of the pixel number deviating from one is also possible. In general, a quadrant detector can also be used as the monitoring sensor 29.Furthermore, a satellite facet 30 in the form of, for example, exactly one individual mirror or else a plurality of selected individual mirrors of the transmission facet mirror 6 belongs to the monitoring device 28.FIG. 6 shows a monitoring light channel 31 from the light source 2 or the intermediate focus 5 avia the satellite facet 30, the illumination specification facet 25, which simultaneously guides the illumination channel 27 according to FIG. 6, to an impact point or impact region 32 on the monitoring sensor 29.The object field 8 has a longer field extension along the x-field dimension and a shorter field extension along the y-field dimension. The monitoring sensor 29 is arranged at a distance from the object field 8 along the x-field dimension and, in the embodiment illustrated in FIG. 6, is situated to the right next to the shorter object field side of the object field 8. The monitoring sensor 29 can also be arranged at a distance from the object plane 9, for example, in comparison to the reticle 12, closer to the illumination-specification facet mirror 7 or alternatively also further away therefrom.On account of the guidance via the same illumination specification facet 25, the satellite facet 30 is assigned to the transmission facet 21 highlighted in FIG. 6, which therefore represents a monitoring transmission facet 21. This assignment brings about an orientation of the satellite facet 30 in such a way that monitoring light, in this case the illumination light 3 generated by the light source 2, is guided from the light source 2, which then equally represents a monitoring light source, via the satellite facet 30 and the illumination specification facet 25 highlighted in FIG. 6 as an illumination specification facet to be monitored along the monitoring light channel 31 toward the monitoring sensor 29.Tilts drx, dry of the illumination specification facet 25, which guides both the illumination channel 27 and the monitoring light channel 31, simultaneously lead to a displacement of the illumination channel 27 and the monitoring light channel 31, namely to displacements dx along the x-coordinate and dy along the y-coordinate. The respective displacement dx, dy on the monitoring sensor 29 is a measure of the tilt dry, drx of the illumination specification facet 25 to be monitored about tilt axes parallel to the coordinate axes x and y. Accordingly, dy=f(drx) and dx=f(dry) apply.From the displacements dx, dy measurable via the monitoring sensor 29 between a setpoint point of incidence 32 spredicted, for example, in the context of a calibration process and the respectively measured actual point of incidence 32 1 of the monitoring light channel 31 on the monitoring sensor 29, it is thus possible to infer actual tilts dry and drx of the monitored illumination specification facet 25.When monitoring the illumination specification facets 25 of the illumination specification facet mirror 7 with the aid of the monitoring device 28, the following procedure can be adopted:First, satellite facets 30 are assigned to illumination specification facets 25 to be monitored. This can be associated with transmission facets 21 by assigning satellite facets 30 which, on the one hand via transmission facet 21 and illumination channel 27 used in the projection exposure and, on the other hand, via satellite facet 30 and monitoring light channel 31, impinge light on the same illumination specification facet 25 to be monitored.Depending on the boundary conditions of the assignment step, the satellite facet 30 can be closely adjacent to the monitoring transmission facet 21 assigned to it. A maximum distance that can be predefined in this case can be, for example, the typical dimension of a monitoring transmission facet 21. An assignment can be made, for example, with the boundary condition that the satellite facet 30 to be assigned is present on a same single mirror unit 26 as in any case a plurality of single mirrors ES of the monitoring transmission facet 21 to be assigned. A group of individual mirrors can therefore also be used as the monitoring transmission facet 21. As an advantage, a greater distance between the satellite facet 30 and the monitoring transmission facet 21 assigned to it in turn allows the monitoring sensor 29 to be integrated into the scanner at a greater distance from the reticle 12.After the assignment has been completed, the monitoring light, i.e. for example the illumination light 3, is guided along the monitoring light channel 31 via the respective satellite facet 30 and the assigned illumination specification facet 25 and an actual point of impingement 32 i of the monitoring light channel 31 on the monitoring sensor 29 is measured in a spatially resolved manner. The actual point of impingement 32 I is then compared with the predetermined setpoint point of impingement 32 S.This comparison takes place with the aid of an evaluation device 33 of the illumination optical unit 11. The evaluation device 33 is in signal connection with a central control device 34 of the projection exposure apparatus 1.Depending on the comparison result of the monitoring method, compensatory countermeasures can be initiated, in particular. This can be done via the control device 34. If displacements of the points of impingement can be attributed to thermal drifts, thermal or mechanical compensation measures can also be taken in particular.FIG. 7 shows a further embodiment of a monitoring device 35 which can be used alternatively or additionally to the monitoring device 28 in a corresponding embodiment of the illumination optical unit 11 of the projection exposure apparatus 1. Components and functions corresponding to those already explained above with reference to FIGS. 1 to 6 and in particular with reference to FIG. 6 are given the same reference numerals and will not be discussed in detail again.The illumination optical unit 11 according to FIG. 7 is shown as a specular reflector. Shown by way of example are main beams 36 guided via individual mirrors ES of the illumination specification facet mirror 7 and boundary beams 37 delimiting an illumination angle distribution on one side and boundary beams 38 delimiting on the other side. This is illustrated in the fundamentally schematic illustration according to FIG. 7 in that the main beams 36 meet at a center of the entry pupil 12 aof the illumination optical unit 11. Correspondingly, the marginal rays 37 on the one hand and 38 on the other hand meet in the beam path of the illumination light 3 downstream of the object field 8 at opposite marginal points of the entry pupil 12 a.The illumination-specification facet mirror 7 is arranged at a distance from the entry pupil plane 12 bof the projection optical unit 10, not illustrated in FIG. 7. Since it is situated in the beam path downstream of the object field 8, the entrance pupil 12 aof the projection optical unit 10 is not accessible as an arrangement plane for the illumination-specification facet mirror 7.Also shown in FIG. 7 are, bounded in each case by two individual beams, two illumination channels 27 1 and 27 2, which are used for illuminating the reticle 12. The illumination channel 27 1 is bounded by one of the main beams 36 and one of the marginal beams 37. the illumination channel 27 1 is guided, starting from the intermediate focus 5a, via a transmission facet 21 1 and an illumination specification facet 25 1 toward the object field 8.The transfer facets 21 1, 212 are formed from a group of individual mirrors ES of the transfer facet mirror 6. Other groupings are also possible, in particular groupings having a few to several hundred of the individual mirrors.The illumination specification facet 25 1 is formed from 2x2 individual mirrors ES of the illumination specification facet mirror 7. the illumination specification facet 25 2 is formed, in contrast thereto, from 4x4 individual mirrors ES of the illumination specification facet mirror 7. It may also be useful to use non-quadratic groups, for example 3x4, 3x5, 4x5, 4x6, 4x7, 5x7 or 6x7 individual mirrors. In the case shown in FIG. 7, the illumination specification facet 25 2 is significantly larger than the illumination specification facet 25 1.The monitoring device 35 according to FIG. 7 has a monitoring light source 39 separate from the illumination light source 2, which can be designed, for example, as a laser diode.The monitoring light source 39 is designed such that it is possible in principle to illuminate the entire transfer facet mirror 6 via the latter. A wavelength conversion screen 40 is arranged in the beam path of the monitoring light source 39.The monitoring light source 39 can be a monochromatic laser diode. The wavelength conversion screen 40 may be a phosphor screen, for example, a screen including YAG aluminum phosphor.The monitoring device 35 has two monitoring sensors 29 1 and 29 2, which are arranged at a distance on both sides of the object field 8 in the direction of the x-coordinate, i.e. perpendicular to the object displacement direction y of the projection exposure apparatus 1. It is also possible, moreover, to arrange further monitoring sensors 29 at a distance from one another in i in the x direction, in order thus to enlarge the effectively usable sensor surface of the monitoring device 35 and to measure more illumination specification facets simultaneously. It is also possible, moreover, to place exactly one monitoring sensor 29 at a distance from the object field 8 in the object displacement direction y.A monitoring light channel 31 is shown in FIG. 7 between the wavelength conversion screen 40, a satellite facet 30, designed as a single mirror ES on the transmission facet mirror 6, the illumination specification facet 25 2 and the monitoring sensor 29 2 of the monitoring device 35.Due to the application of the same illumination specification facet 25 2 the monitoring light channel 31 illustrated in FIG. 7 and the satellite facet 30 applied by it are assigned to the illumination channel 27 2 and thus to the monitoring transmission facet 21 2 and to the illumination specification facet 25 2 to be monitored.As already explained above in connection with the embodiment according to FIG. 6, tilts drx, dry of the illumination specification facet 25 2 are transmitted in displacements dy, dx of the point of incidence 32 of the monitoring light channel 31 on the monitoring sensor 29 2.By suitable tilt angle assignments of the individual mirrors ES on the facet mirrors 6 and 7, it can be ensured that the monitoring light 41 of the monitoring light source 39 does not impinge on the object field 8 in an undesirable manner.With reference to FIG. 8, a further embodiment of the illumination optical unit 11 and a monitoring device 42 is described below, which can be used alternatively or additionally to the monitoring devices 28, 35 explained above. Components and functions corresponding to those already explained above with reference to FIGS. 1 to 7 and in particular with reference to FIGS. 6 and 7 are given the same reference numerals and will not be discussed in detail again.Components or functional units of the illumination optical unit 11 that are illustrated in FIG. 8 are the intermediate focus 5 a, the transmission facet mirror 6, the illumination specification facet mirror 7 and the object field 8 that is arcuate in this case.Emphasized on the transfer facet mirror 6 are two transfer facets 21 1 and 21 2, which are each constructed from a group of 18 individual mirrors ES. The assignment of the individual mirrors ES to the respective transmission facets 21 1, 212 is such that an envelope of these transmission facets 21 1, 212 is adapted in terms of its shape to the arc shape of the object field 8. Illumination channels, not shown in more detail, guide the illumination light from the intermediate focus 5 aon the one hand via the transmission facet 21 1 and an illumination specification facet 25 1 assigned to the illumination specification facet mirror 7, and via the transmission facet 21 2 and an illumination specification facet 25 2 assigned to the illumination specification facet mirror 7, overlapping one another, for illuminating the entire object field 8 in each case. Other NxM arrangements of the individual mirrors ES are also possible, wherein N and M are each regularly in the range between 1 and 10.A monitoring light source 43 of the monitoring device 42 is designed to generate monitoring light 41 1, 412 and 41 3 of respectively different wavelengths. The monitoring light 41 1 for example of a medium wavelength, originates from a source location 44 1 of the monitoring light source 43 adjacent to the intermediate focus 5 aand is guided along a monitoring light channel 31 1 via a satellite facet 30 1, the illumination specification facet 25 2 to an impact point 32 1 on the monitoring sensor 29 1. The satellite facet 30 1 is therefore assigned 2 to the illumination specification facet 25 to be monitored.The monitoring light source 43 furthermore generates monitoring light 41 2 of a shorter wavelength compared to monitoring light 41 1 which is guided along a monitoring light channel 31 2 from a source location 44 2, in turn adjacent to the intermediate focus 5 a, to a satellite facet 30 2 and the illumination specification facet 25 1 to an impact point 32 2 on the monitoring sensor 29 2. The satellite facet 30 2 is assigned 1 to the illumination specification facet 25 to be monitored.For further monitoring of an individual mirror ES 3 on the illumination-specification facet mirror 7, a third monitoring light channel 31 3, which is illustrated in FIG. 8 and which originates from a source location 44 3, in turn adjacent to the intermediate focus 5 a, is used. Monitoring light 41 3, which originates from this third source location 44 3 has a wavelength which is greater than the wavelengths of the monitoring light 41 1 and 41 2, so that the three different wavelengths of the monitoring light 41 i, which originates from the source locations 44 i can be spectrally discriminated by means of the monitoring device 42.The monitoring light channel 31 3 runs from the source location 44 3 to a further satellite facet 30 3 on the transmission facet mirror 6 via the individual mirror ES 3 to be monitored on the illumination specification facet mirror 7 to a further point of incidence 32 3 on the monitoring sensor 29 2. The satellite facet 30 3 is assigned to the individual mirror ES 3 to be monitored. In contrast to the mirror groups ES 1 and ES 2 ES 3 is not exposed to light which has to be imaged into the reticle 8. Such a configuration is useful for specifically measuring an individual mirror such as ES 3 in its tilt angle behavior, independently of the scanner operation, since precisely one image 32 3 is imaged on the sensor by this mirror. In contrast, in the cases 32 1 and 32 2 on the monitoring sensors 29 in this example, 4 (2×2) image overlays of the images of 21 1 and 21 2 are present. The measured images 32 1 and 32 2 are therefore averaged over the tilt angle deviations of the mirror groups 25 1 and 25 2 involved.The monitoring sensors 29 i of the monitoring device 42 can be designed to be spectrally selective, so that these monitoring sensors 29 1, 292 can be determined via the wavelength of the monitoring light 41 i which point of incidence 32 i belongs to which monitoring light channel 31 3 belongs. In particular, parallel processing of an evaluation of the points of impingement 21 i is possible by means of the monitoring device 42, so that the steps explained above in connection with the monitoring method "guiding monitoring light 41 i, measuring a target point of impingement 32 i and comparing the actual point of impingement 32 i with a predetermined target point of impingement" can be carried out in parallel.Spectral selectivity or color separation via the monitoring sensors 29 i makes it possible to record a plurality of superimposed images simultaneously.The monitoring light source 43 may be an RGB light source. The number of monitoring light channels 31 i each having different monitoring light wavelengths can also be greater than three and can be in the range between three and 20 or even greater, for example. In principle, i monitoring light 41 i of a different wavelength can be used for each illumination specification facet 25 to be monitored, so that all illumination specification facets 25 i can also be detected simultaneously with a correspondingly spectrally discriminating monitoring sensor 29. Groups of monitoring light channels 41 i each having the same wavelength and belonging to monitoring light channels 31 i whose target points of incidence differ sufficiently spatially on the monitoring sensor 29 can also be formed, so that, for example, when using three wavelengths of the monitoring light 41 and 300 illumination specification facets 25 i to be monitored, 100 illumination specification facets each having the same wavelength of the monitoring light 41 can be monitored.The monitoring sensors 29 1, 292 can in particular take the form of monitoring device 42 as CMOS sensors with a colored Bayer matrix adapted to the wavelengths of the monitoring light source 43. Bayer matrices are known, for example, from the technical article "Review of Bayer Pattern Color Filter Array (CFA) demosaicing with new quality assessment algorithms" by R. A. Masal Jr., et al., ARL-TR-5061, January 2010.FIG. 9 shows, in a representation comparable to FIG. 6, a further embodiment of a monitoring device 45 which can be used alternatively or additionally to one of the monitoring devices explained above. Components and functions corresponding to those already explained above with reference to FIGS. 1 to 8 and in particular with reference to FIG. 6 are given the same reference numerals and will not be discussed in detail again.In the case of an illumination setting that is to be monitored by means of the monitoring device 45, an illumination specification facet 25 contains four individual mirrors ES 1 to ES 4 which together group form the illumination specification facet 25, corresponding for example to the illumination specification facets 25 i of the embodiment according to FIG. 8.In the monitoring device 45, the satellite facet 30 is designed to be controlled via the control device 34 of the monitoring device 45, actuatorally tiltable by tilt angles drx and dry analogously to what was explained above, for example in connection with the illumination specification facet 25 of the monitoring device 28 according to FIG. 6. The control device 34 contains a monitoring scanning unit 46 which is in signal connection with the actuator system of the satellite facet 30 used by means of the monitoring device 45.When guiding the monitoring light 3 along the monitoring light channel 31, the monitoring scanning unit 46 controls the satellite facet 30 such that all four individual mirrors ES 1 to ES 4 of the illumination specification facet 25 are scanned during the monitoring process of this illumination specification facet 25, which is illustrated in FIG. 9 by arrows between the individual mirrors ES 1 to ES 4.Corresponding to the progress of the scanning step, the respective individual mirrors ES 1 to ES 4 result in points of incidence 32 ES1 to 32 ES4, of which two points of incidence 32 ES1 and 32 ES2, associated with the individual mirrors ES 1 and ES 2 are shown in FIG. 9. On the basis of these respectively measured points of incidence 32 ESi a comparison with the corresponding target points of incidence of the monitoring method of monitoring all individual mirrors ES i of the illumination specification facet 25 can then be carried out.FIG. 10 illustrates how many individual mirrors ES are available as satellite facets 30 in a typical illumination setting used in projection exposure. A plan view of the transfer facet mirror 6 is shown, wherein those individual mirrors ES which are used in the set illumination setting are highlighted by an x symbol. For these used individual mirrors ES, there are practically unused individual mirrors ES uniformly distributed over an entire surface of the transmission facet mirror 6, which can be used as satellite facets 30 within the scope of one of the monitoring methods explained above. The number of individual mirrors ES usable as satellite facets 30 is regularly greater than the number of illumination specification facets 25 to be monitored, with the result that, in principle, all illumination specification facets used in an illumination setting can be monitored with respect to their current tilt position using the monitoring methods described above.FIG. 11 shows, by way of example, the result of a parallel measurement, for example with the aid of a monitoring device of the type of the monitoring device 42 which can be generated with a greater number of different monitoring light wavelengths 41 in i fashion. The points of incidence 32 assigned to a respective monitoring light wavelength are illustrated by different symbols on the monitoring sensors 29 1 and 29 2 respectively. The points of incidence 32 which are assigned to different light wavelengths 41 i are partially superimposed on one another. Here, spectral selectivity of the monitoring device 42 can be used, as explained above.FIG. 11 shows a plan view of an object field 8 which is rectangular in this case between sensor surfaces of the two monitoring sensors 29 1 and 29 2. An x-extent of the sensor surfaces can lie in the range between 10% and 100% of an x-extent of the object field, for example 25% to 75%. A y-extension of the sensor surfaces of the monitoring sensors 29 1, 292 is regularly greater than a y-extension of the object field actually used for the instantaneous exposure and can have, for example, a y-extension corresponding to a total y-scan profile over the object field 8, or a multiple thereof; for example 200% or 500%. The monitoring sensor 29 thus enlarged can also be realized in i at a distance from the object field.The sensor surfaces of the monitoring sensors 29 i can be rectangular and in particular square.FIG. 12 shows, in a representation similar to FIG. 11, a distribution of approximately 100 points of impingement 32 on the sensor surface of one of the monitoring sensors 29 of one of the above-described embodiments of the monitoring device. This arrangement of the points of incidence 32 has a minimum distance between respectively predetermined target points of incidence of different monitoring light channels on the monitoring sensor 29, so that these points of incidence 32 can be differentiated even if the respective actual points of incidence move away from the target points of incidence on account of tilts of the monitored illumination specification facets 25.By means of a corresponding assignment algorithm, an assignment of the satellite facets 30 to the illumination specification facets 25 to be monitored in each case can be achieved, in which an appropriate spatial distribution of the points of incidence 32 with a sufficient minimum distance between two adjacent desired points of incidence is ensured.FIGS. 13 and 14 show a further embodiment of a monitoring device 47, which can be used instead of the monitoring devices described above. Components and functions corresponding to those already explained above with reference to FIGS. 1 to 12 and in particular with reference to FIGS. 6 to 12 are given the same reference numerals and will not be discussed in detail again.A monitoring light source 48 is designed in the monitoring device 47 as a light source grid with individual sources 49 arranged in an NxM grid. FIGS. 13 and 14 show a 6x6 grid of individual sources 49.With the aid of such a light source grid, monitoring of tilting positions of a plurality of individual mirrors ES of an illumination specification facet 25 to be monitored with the same monitoring result as was described above in connection with FIG. 9 in the context of sequential scanning processing is possible with the monitoring device 47 in parallel processing.In FIGS. 13 and 14, a monitoring light channel is shown for the purpose of illustration, which leads from a center of the light source grid of the monitoring source 48 via a satellite facet 30 and an illumination specification facet 25 having a total of 6x6 single mirrors ES to an impact point 32 on the monitoring sensor 29. In the embodiment according to FIGS. 13 and 14, the illumination specification facet 25 is embodied as a 6x6 raster of individual mirrors ES.FIG. 13 shows the situation in which all individual sources 49 of the monitoring light source 48 are activated. Also shown is the situation in which the illumination specification facet 25 is arranged in a pupil plane of the illumination optical unit, such that a grid of corresponding source images 50 of the individual sources 49 is generated on the illumination specification facet 25. The position of this grid of source images 50 can be determined within the scope of a calibration measurement. The distances of the individual sources 49 from one another can be dimensioned such that the source images 50 are each assigned exactly to an individual mirror ES of the illumination specification facet.When all 36 individual sources 49 are activated, in the situation according to FIG. 13, in any case basically all 36 individual mirrors ES of the illumination specification facet 25 to be monitored can be monitored with regard to their points of incidence via the monitoring light channel 31 toward the sensor 29. Parallel monitoring is thus possible, as an alternative to the scanning variant of the monitoring by means of the monitoring scanning unit 46 illustrated above in connection with FIG. 9.To measure individual individual mirrors ES of the illumination specification facet 25 to be monitored, the operating situation according to FIG. 14 can be produced in which exactly one selected individual source 49 of the monitoring light source 48 is activated, whereas all other 35 individual sources 49 are deactivated. Via the monitoring light channel 31 resulting therefrom via the satellite facet 30 and the individual mirror ES at the location of the source image 50 of the activated individual source 49, it is then possible to monitor the angle of tilt of this associated individual mirror ES.When comparing the respective actual point of incidence with the respectively predetermined target point of incidence, techniques can be used which are known in optics as cross-correlation techniques. Such a cross-correlation can be used for determining a displacement of a specific point of incidence 32 or also for parallel determination of displacements of a plurality of points of incidence 32 by determining and evaluating a cross-correlation signal of a recording of the monitoring sensor 29 with a corresponding plurality of points of incidence 32 i, which each belong to a monitoring light channel 31 i.In parallel with the monitoring of the illumination optical unit 11 using a monitoring device described above, a useful projection exposure for imaging the reticle 12 onto the wafer 19 can be carried out using a preset illumination setting.In order to produce a microstructured component, in particular a highly integrated semiconductor component, for example a memory chip, with the aid of the projection exposure apparatus 1, the reticle 12 and the wafer 19 are first provided. A structure on the reticle 12 is then illuminated with the illumination light 3 by the illumination optical unit 11 and projected onto a light-sensitive layer on the wafer 19 by the projection optical unit of the projection exposure apparatus 1. By developing the light-sensitive layer, a microstructure is then produced on the wafer 19 and the micro- or nanostructured component is produced therefrom.The component produced can be a microchip, in particular a memory chip.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2015 208 512 A1

[0002] WO 2010 / 099 807

[0042] US 2006 / 0132747 A1

[0048] Cited Non-Patent LiteratureReview of Bayer Pattern Color Filter Array (CFA) demosaicing with new quality assessment algorithms" by R. A. Maschal Jr., et al., ARL-TR-5061, January 2010

[0097]

Claims

Illumination optical unit (11) for projection lithography - having a transmission facet mirror (6) having a plurality of transmission facets (21) for guiding illumination light (3) from an illumination light source (2) via illumination channels (27) which are predefined by the transmission facets (21) along an illumination light beam path, - having an illumination predefined facet mirror (7) having a plurality of actuator-tiltable illumination predefined facets (25) for superimposed guidance of the illumination light (3) via the illumination channels (27) via in each case one of the transmission facets (21) and in each case one illumination predefined facet (25) assigned via the respective illumination channel (27) towards an object field (8) in which an object (12) to be illuminated can be arranged, wherein the illumination-specification facet mirror (7) is part of an optical system via which the transmission facets (21) are imaged at least in sections of the object field (8), - having a monitoring device (28; 35; 42; 45; 47) which has: - at least one spatially resolving monitoring sensor (29; 29 1, 292), -- at least one satellite facet (30) of the transmission facet mirror (6) which is in each case assigned to exactly one of the transmission facets (21) which then represents a monitoring transmission facet and is oriented such that monitoring light (3; 41) from a monitoring light source (2; 39; 43; 48) is guided along a monitoring light channel (31) towards the monitoring sensor (29; 29 1, 292) via the satellite facet (30) and one of the illumination specification facets (25) as an illumination specification facet to be monitored, which is assigned to the monitoring transmission facet via the illumination channel (27).Illumination optical system according to Claim 1, characterized bya plurality of satellite facets (30).Illumination optical unit according to Claim 1 or 2, characterized in that the satellite facet (30) is closely adjacent to the monitoring transmission facet (21) assigned to it in each case.Illumination optical unit according to one of Claims 1 to 3, characterized in that the object field (8) has a longer field extent along a first field dimension (x) and a shorter field extent along a second field dimension (y) perpendicular thereto, wherein the at least one monitoring sensor (29; 29 1, 292) is arranged at a distance from the object field (8) along the first field dimension (x).Illumination optical unit according to one of Claims 1 to 4, characterized in that the monitoring light source (39; 43; 48) is designed as a light source separate from an illumination light source (2), wherein the monitoring light (41) is guided along a monitoring light beam path adjacent to the illumination channels (27) via at least one of the satellite facets (30) and the associated illumination specification facet (25) to be monitored.Illumination optical system according to one of Claims 1 to 5, characterized by monitoring light (3; 41) of a plurality of wavelengths, wherein the at least one monitoring sensor (29 is of 1, 292) wavelength-selective design.Illumination optical unit according to one of Claims 1 to 6, characterized in that the transmission facets (21) are each divided into a plurality of transmission individual mirrors (ES), and / or in that the illumination specification facets (25) are each divided into a plurality of illumination specification individual mirrors (ES).Illumination optical unit according to Claim 7, characterized in that the at least one satellite facet (30) is designed such that it can be tilted by actuators, wherein the monitoring device (45) has a monitoring scanning unit (46) which is in signal connection with an actuator system for tilting the at least one satellite facet (30).Illumination optical unit according to one of Claims 1 to 8, characterized in that the monitoring light source (48) is designed as a light source grid which is designed in a manner adapted to a grid of illumination specification individual mirrors (ES) which each form an illumination specification facet (25).Method for monitoring an illumination optical unit (11) according to one of Claims 1 to 9, having the following steps: - assigning satellite facets (30) to the illumination specification facets (25) to be monitored, - guiding monitoring light (3; 41) along at least one monitoring light channel (31) via the respective satellite facet (30) and the assigned illumination specification facet (25) to be monitored, - measuring an actual point of incidence (32) of the respective monitoring light channel (31) on the monitoring sensor (29), - comparing the actual point of incidence (32) with a predetermined setpoint point of incidence of the respective monitoring light channel (31).Method according to Claim 10, characterized in that, during the assignment, a minimum distance between predetermined target points of impingement of different monitoring light channels (31) on the monitoring sensor (29) is observed, and / or in that, during the assignment, a maximum distance between the respective satellite facet (30) and the monitoring transmission facet (21) assigned to it, which is assigned to the illumination specification facet (25) to be monitored via an illumination channel (27), is not exceeded.Optical system having an illumination optical unit according to one of Claims 1 to 9 and having a projection optical unit for imaging the object field (8) into an image field (17) in which a substrate (19) can be arranged.Optical system with an illumination optical system according to one of Claims 1 to 12 and with a monitoring light source (2; 39; 43; 48).Projection exposure apparatus having an optical system according to Claim 12 or 13 and having an illumination light source (2).Method for producing a microstructured component, having the following method steps: - providing a reticle (12), - providing a wafer (19) having a coating sensitive to the illumination light (3), - projecting at least a portion of the reticle (12) onto the wafer (19) with the aid of the projection exposure apparatus (1) according to Claim 14, - developing the photosensitive layer exposed to the illumination light (3) on the wafer (19).Component produced by a method according to Claim 15.

Images