Collector mirror and collector mirror assembly for lithography

Abstract

A collector mirror (21) for lithography has a mirror substrate body (22) comprising a mirror basic body (23) and at least one mirror holding section (25). The mirror basic body (23) has a mirror reflection surface (24) for illumination light (4). The mirror holding section (25) is integrally formed with the mirror basic body (23). The mirror substrate body (22) has at the mirror holding section (25) a holding section wall thickness (H) which differs from a further wall thickness (W) of the mirror substrate body (22). A collector mirror assembly includes a collector mirror basic body with a basic body reflection surface for illumination light and a supporting body to mount the basic mirror body. The mirror basic body is mounted floating relative to the supporting body. A collector mirror and a collector mirror assembly including a mirror supporting body result with an improved reproducibility of a position relationship between such collector mirror on the one hand and a light source and / or a mirror supporting body on the other.

Description

[0001] Collector mirror and collector mirror assembly for lithography

[0002] The contents of German patent application DE 10 2024 200 787.0 is incorporated by reference.

[0003] The invention relates to a collector mirror for lithography. Further, the invention relates to a collector mirror assembly for lithography having such a collector mirror, to an illumination system having such a collector mirror assembly, to an optical system having such an illumination system, to a projection exposure system having such an optical system, to a method of producing structured components using a projection exposure apparatus of this type, and to a micro- or nanostructured component which is produced according to this method.

[0004] A collector mirror for collecting illumination light for guiding this illumination light to subsequent illumination optics is known for the UV- wavelength range, for the DU V- wavelength range, and also for the EUV- wavelength range. Such collector mirrors in particular used to collect and guide UV and DUV wavelengths comprise a mirror substrate body made of glass which is fitted into a supporting body. In particular, such a collector mirror is known to be part of a projection exposure apparatus using a mercury vapor light source with a useful wavelength of 365 nm. In particular, such a collector mirror or such a collector mirror assembly may be part of a light or radiation source. Such radiation source may be arranged as a part of (or connected to) an illumination system to provide radiation, e.g. light at a wavelength of 365 nm (i-line), to a lithographical apparatus. The lithographical apparatus may be, for example, an exposure apparatus or a metrology apparatus. DE 10 2017 220 306 Al discloses a mounting arrangement for an optical component. DE 10 2014 216 631 Al discloses a microlithographic projection exposure apparatus, a mirror module usable for such apparatus and a method to operate such mirror module. EP 1 326 114 Al discloses an optical element holding device. US 9,335,641 Bl discloses an optical element mount for a lithographic apparatus. US 6,822,251 Bl discloses a monolithic silicon EUV collector. DE 10 2019 112 224 Al discloses a holding device for an optical element.

[0005] It is an object of the present invention to improve a collector mirror or a collector mirror assembly of the type named in the outset in such a way that the absolute position or the reproducibility of a position relationship between such collector mirror on the one hand and a light source and / or a mirror supporting body and / or a subsequent illumination optics on the other is improved.

[0006] This object is achieved according to the invention by a collector mirror having the features set out in claim 1.

[0007] Integrally forming a mirror holding section with the mirror basic body enables the collector mirror to be securely and reproducibly mountable with a supporting body or with a supporting frame. The wall thickness difference between the holding section wall thickness and the further wall thickness of the mirror substrate body makes it possible to define abutment wall sections for respective holding / counterholding means to reproducibly secure the collector mirror at a supporting body or at a supporting frame. The mirror reflection surface may have a semi-spherical shape. The mirror reflection surface may have an ellipsoidal shape. The mirror reflection surface may have a parabolic shape. The mirror reflection surface may be an inner wall surface of the mirror basic body. The mirror reflection surface may have a high reflective coating.

[0008] Integrally formation of the mirror holding section with the mirror basic body may be realized by connecting both components to one form. Doing so, the mirror holding section also may be formed in a subsequent production step to the mirror basic body.

[0009] Integral formation of the mirror holding section with the mirror basic body may be done by a respective molding or by material adding and / or removal. Such material removal may be done via milling, turning, grinding or polishing. Further, integral formation of the holding section with the mirror basic body may be done by a joining or bonding process, in particular by gluing, soldering or anodic bonding.

[0010] The holding section may be designed such that a hanging support of the collector mirror by the supporting body is possible exploiting the gravitational force, i.e., the weight of the collector mirror.

[0011] The holding section in particular may be arranged in a rotational symmetrical maimer around an optical axis of the collector mirror. This facilitates a thermal management of the collector mirror assembly.

[0012] The mirror holding section may be realized such that holding forces are below a certain force threshold, in particular below 1.000 N, below 800 N, below 750 N, below 700 N, below 650 N, below 600 N, below 550 N, below 500 N, below 450 N, below 400 N, below 350 N, below 300 N, below 250 N, below 200 N, below 150 N, below 100 N, below 50 N. As a rule, such holding forces are at least 1 N. Depending on geometrical dimensions of the mirror holding section and also of the mirror basic body also larger or lower value of such force threshold is suitable. This avoids strain induced mirror deformations.

[0013] A holding section wall thickness being larger than the further wall thickness according to claim 2 improves a stability of the mirror substrate body at the mirror holding section.

[0014] A circumferential collar according to claim 3 makes it possible to use mounting schemes to mount the collector mirror to a supporting body or to a supporting frame which gives a good position reproducibility. Such mounting scheme may be, e.g., like a flange assembly. The circumferential collar may be embodied as an outer circumferential collar at an outer boundary of the mirror reflection surface of the mirror substrate body. In particular, holding forces at such collar may be such that the mirror reflection surface is not put under stress to an unwanted degree.

[0015] An embodiment according to claim 4 makes it possible to mount a collector mirror in the vicinity of an inner opening of the mirror substrate body. A compact holding scheme may be the result.

[0016] A collector mirror may comprise a plurality of holding sections. One of the holding sections of this plurality may be an outer circumferential collar and another of these holding sections may be an inner circumferential collar as discussed above.

[0017] A sleeve section according to claim 5 enables further holding schemes including clamping at the sleeve section and / or a bolted or screwed joint. The sleeve section may be at an inner circumferential collar of the holding section.

[0018] A holding section wall thickness being smaller than the further wall thickness according to claim 6 may be realized as a recess or as an undercut. Such recess or undercut may be in an outer surface of the mirror basic body and may not interfere with the mirror reflection surface. Such recess / under- cut may be realized as a circumferential collar. A smaller holding section wall thickness may be realized by machining the mirror basic body from a raw mirror substrate body with initial uniform wall thickness.

[0019] In at least a certain area the holding section wall thickness may be larger than the further wall thickness and in another area the holding section wall thickness may be smaller than the further wall thickness.

[0020] The advantages of a collector mirror assembly according to claim 7 correspond to those of the collector mirror discussed above. Via the at least one mirror holding section, the mirror substrate body of the collector mirror is held by the supporting body and in particular is mounted with the supporting body. A thermal stability and / or a shock stability of the collector assembly may be improved.

[0021] A floating mount of the mirror basic body relative to the supporting body according to claim 8 has been found to be of particular advantage.

[0022] The mirror supporting body of such collector mirror assembly may surround an outer wall of the mirror basic body. The floating mount of the mirror basic body with the supporting body makes it possible, that a position of the mirror reflection surface of the mirror basic body is independent of a thermal expansion of the collector mirror. Such thermal expansion therefore leads to no unwanted distortion of the collection function of the collector mirror. The floating mount may provide that the collector mirror center stays at the optical axis of the collector mirror and of an illumination light path guided via the collector mirror during a possible thermal expansion of the collector mirror. The floating mount may provide that forces of expansion are equally distributed.

[0023] At least three elastic members according to claim 9 ensure a sufficient floating mount of the mirror basic body relative to the supporting body. The elastic members may be arranged equidistantly surrounding a circumference of the mirror basic body. The number of the elastic members may be in the range between three and twenty, in particular in the range between three and twelve. Each of the elastic members may provide relative movement of the collector mirror or a part of this collector mirror to the supporting body along one degree of freedom. In effect, each of the elastic members can compensate a relative movement of at least a part of the collector mirror to the supporting body through e.g. thermal expansion of the collector mirror and / or the supporting body without unwanted dealignment of the optical system.

[0024] The flexure members according to claim 10 are well suited to give the wanted floating mount. The elastic members or the flexure members may be integrally parts of the supporting body. The respective flexure member may be embodied as at least one flexure bar. Such flexure bar may be connected to the supporting body via one bar and / or alternatively via both bar ends. Such flexure member may extend parallel to a plane defined by a circumference of the reflection surface or alternatively may extend appendicular to such circumference plane.

[0025] Advantages of a collector mirror assembly according to claim 11 are discussed above with respect to the collector mirror.

[0026] The at least one cooling channel according to claim 12 helps to reduce a thermal load on the mirror substrate body, in particular due to residual absorption of the illumination light. The cooling channel or at least a section of the cooling channel may be located within the supporting body. The cooling channel is designed to guide a cooling fluid, i.e. a cooling liquid or a cooling gas. The at least one cooling channel may be connected to a source of a respective cooling fluid. Alternatively or in addition, the supporting body may be realized with at least one cooling fin to enlarge a surface area of the supporting body and in particular to improve a radiation cooling of the collector mirror assembly.

[0027] The at least one clamping body according to claim 13 enables a secure connection of the collector mirror with the supporting body. The clamping body may clamp a circumferential collar and / or a recess or undercut of the holding section against the supporting body.

[0028] The clamping body may be movable between a clamping position and a release position to release the collector mirror from the supporting body.

[0029] A clamping spring according to claim 14 may be embodied as a tension spring, in particular as a compression spring, or as a flexure spring. Such clamping spring enables a reversible atachment of the collector mirror to the supporting body.

[0030] A fixation of the mirror basic body via a clamping body to at least one of the elastic members according to claim 15 ensures to define a fixed positional relationship between the respective elastic member and the mirror basic body. Alternatively or in addition, the mirror basic body may be fixed to a main supporting body via a clamping body which in that case would not be mounted at the elastic member but would be mounted at the main supporting body. To ensure the floating mount in that case, a respective relative movement of the clamping body to the mirror basic body needs to be ensured. In that case, the design of the elastic member without the need to provide a mount for the clamping body is facilitated.

[0031] Combinations of the clamping embodiments discussed above may be part of the collector mirror assembly.

[0032] The at least one actuator according to claim 16 helps, in combination with respective guidings to adjust the collector mirror relative to the supporting body and / or relative to the light source. The actuator may enable a movement between the collector mirror on the one hand and the supporting body and / or the light source on the other along at least one degree of freedom. Depending on the actuator design, a movement along more than one degree of freedom may be possible. The actuator design may enable a movement along two to six degrees of freedom.

[0033] Further, combinations of the features of the collector mirror and of the collector mirror assemblies as discussed above may result in further embodiments which also are part of the disclosure herein. Advantages of an illumination system according to claim 12, of an optical system according to claim 13, of a projection exposure system according to claim 14, of a production method according to claim 15, and of a microstructured and / or nanostructured component according to claim 16, correspond to those discussed above with respect to the collector mirror or the collector mirror assembly. The produced component or device may be a semiconductor chip.

[0034] The collector mirror or the collector mirror assembly as well as the illumination system or the optical system may be part of a metrology apparatus. Such metrology apparatus may be used to inspect an object, in particular to inspect a lithography mask or a mask blank. Such inspection may be used to detect certain defects of the mask or the mask blank.

[0035] The light source may be an arc-lamp, for example a high-pressure arclamp. The light source may be a xenon (Xe) lamp. The light source may be a mercury (Hg) lamp emitting a spectra line approximately at 365 nm (i- line). Alternatively, the light source may be an EUV light source.

[0036] The light source may be part of the collector mirror assembly.

[0037] Embodiments of the invention will hereinafter be explained in more detail by means of the drawing in which:

[0038] Fig. 1 shows a schematic meridional section through optical main groups of a projection exposure apparatus for microlithography; Fig. 2 a meridional section of a collector mirror assembly having a collector mirror with a mirror substrate body having at a holding section a wall thickness differing from a further wall thickness of the mirror substrate body;

[0039] Fig. 3 in a broken meridional section near an outer boundary of the mirror reflection surface another embodiment of the mirror basic body having a holding section embodied as a recess where the holding section wall thickness is smaller than the further wall thickness;

[0040] Fig. 4 in a meridional section another embodiment of the mirror substrate body of the collector mirror having a holding section embodied as an inner circular collar at an inner opening of the mirror substrate body;

[0041] Fig. 5 in a depiction similar to that of fig. 4 another embodiment of the mirror substrate body having a holding section comprising a sleeve section;

[0042] Fig. 6 in a depiction similar to that of fig. 3 another embodiment of the mirror substrate body having a holding section embodied as a circumferential inner recess having a holding section wall thickness being smaller than the further wall’s thickness;

[0043] Fig. 7 in a depiction similar to that of figs 3 and 6 another embodiment of the mirror substrate body having a holding section embodied as a circumferential inner recess having a holding section wall thickness being smaller than the further wall’s thickness, the recess defining an undercut and thus an outer circumferential collar;

[0044] Fig. 8 an upper view of the collector mirror assembly having a mirror substrate body according to fig. 2 showing additionally clamping bodies, abutment bodies and further illustrating a pretensioning force of a clamping tension spring of the collector mirror assembly;

[0045] Fig. 9 a broken meridional section of the collector mirror assembly of fig. 8 at one of the clamping bodies, a clamping body being shown in a release position;

[0046] Fig. 10 in a perspective sectional view comparable to that of fig. 9 another embodiment of a clamping body in a more detailed depiction, the clamping body being shown in a clamping position;

[0047] Fig. 11 a perspective view of the collector mirror assembly having the clamping bodies according to fig. 10, two of them in the clamping position and one being in a release / unclamp- ing position, further showing a clamping tension spring giving a pretension force comparable to that shown in fig. 8;

[0048] Fig. 12 an enlarged portion of fig. 11 showing details of the clamping tension spring (detail XII in fig. 11); Fig. 13 in a view similar to that of fig. 8 another embodiment of the collector mirror assembly having three tensioning springs for floating mount of a collector mirror relative to a supporting body of the collector mirror assembly;

[0049] Fig. 14 in a view similar to that of figs 8 and 13 another embodiment of the collector mirror assembly including another embodiment of elastic or flexure members for floating mount of a collector mirror relative to a supporting body of the collector mirror assembly;

[0050] Fig. 15 enlarged the detail XV of fig. 14 additionally showing a clamping body to fix a mirror basic body of the fig. 14 embodiment to the shown flexure member;

[0051] Fig. 16 further enlarged a section along line XVI-XVI in fig. 15;

[0052] Figs 17 and 18 respectively in a view similar to that of fig. 15 further embodiments of a flexure member which may be used alternatively to that shown in fig. 15;

[0053] Fig. 19 an enlarged detail view similar to that of fig. 15 showing another embodiment of a flexure member part of a three flexure member design for floating mount of the mirror basic body relative to the supporting body of the collector mirror assembly, wherein the mirror basic body is fixed to the main supporting body via another embodiment of a clamping body; Fig. 20 a sectional view along line XX-XX in fig. 19;

[0054] Fig. 21 in a view similar to that of figs 8, 13, and 14 another embodiment of the collector mirror assembly having three flexure members for floating mount of a collector mirror relative to a supporting body of the collector mirror assembly;

[0055] Fig. 22 a sectional view along angled line XXII-XXII in fig. 21;

[0056] Fig. 23 an enlarged view of one of the flexure members of the fig. 21 embodiment for floating mount of the mirror basic body relative to the supporting body;

[0057] Figs 24 and 25 in sectional views similar to that of fig. 23 further embodiments of flexure members for floating mount of the mirror basic body relative to the supporting body;

[0058] Fig. 26 in a view similar to that of figs. 8, 13, 14, and 21 another embodiment of the collector mirror assembly having three elastic members for floating mount of the mirror basic body relative to the supporting body; and

[0059] Fig. 27 in a view similar to that of figs. 8, 13, 14, 21, and 26 another embodiment of the collector mirror assembly having 12 elastic members for floating mount of the mirror basic body relative to the supporting body. Fig. 1 shows a schematic meridional section through the optical main groups of a projection exposure apparatus 1. In this schematic illustration, the optical main groups are refractive optical elements. The optical main groups may also be diffractive or reflective components or combinations or subcombinations of refractive / diffractive / reflective assemblies of optical elements.

[0060] A Cartesian xyz coordinate system will hereinafter be used to facilitate the description of positional relationships. In Fig. 1, the x-axis extends into the drawing plane in a direction perpendicular to the drawing plane. The y-axis extends upwardly in Fig. 1. The z-axis extends to the right of Fig. 1 and is parallel to an optical axis 2 of the projection exposure apparatus 1. If required, the optical axis 2 may also be folded one time or several times.

[0061] The projection exposure apparatus 1 has a radiation source 3 which generates useful light in the shape of an illumination radiation bundle or imaging radiation bundle 4, respectively. The useful light 4 has a wavelength which is in the ultraviolet range (UV) or in the deep ultraviolet range (DUV), for instance in the range of between 193 nm and 365 nm. The radiation source 3 may be embodied as Hg lamp. Details of a collector mirror assembly having a collector mirror to collect the illumination radiation bundle 4 are hereinafter explained with reference to figures 2 et seq.

[0062] An illumination optics 5 of the projection exposure apparatus 1 guides the useful light 4 from the radiation source 3 to an object plane 6 of the projection exposure apparatus 1. An object in the form of a reticle or patterning device 7, which is to be imaged by means of the projection exposure apparatus 1, is arranged in the object plane 6. The reticle 7 is shown by dashed lines in Fig. 1. The reticle 7 is supported on a holding device (not shown), which is configured for a controlled scanning displacement or a gradual displacement.

[0063] The first optical main group of the illumination optics 5 is a pupil-forming optics 8. Said pupil-forming optics 8 serves to generate a defined intensity distribution of the useful light 4 in a downstream pupil plane 9. Furthermore, the pupil-forming optics 8 serves as an adjustment device for defining various illumination settings. Similar adjustment devices, which are for example equipped with displaceable optical components or interchangeable stops, are known to those skilled in the art. The pupil-forming optics 8 images the radiation source 3 into the pupil plane 9 in such a way that a plurality of secondary light sources is obtained. The pupil-forming optics may additionally have a field-forming function. The pupil-forming optics 8 may be equipped with facet elements, honeycomb elements and / or diffractive optical elements. The pupil plane 9 is optically conjugated with another pupil plane 10 of a projection objective 11 of the projection exposure apparatus 1. The projection objective 11 is arranged downstream of the illumination optics 5 between the object plane 6 and an image plane 12. Arranged in the image plane 12 is a wafer (semiconductor substrate) 13 which is shown by a dashed line in Fig. 1. The wafer 13 is supported on a holding device (not shown) which is configured for a controlled scanning displacement or a gradual displacement. The projection objective 11 is used to image an object field 14 in the object plane 6 into an image field 14a in the image plane 12.

[0064] Another optical main group of the illumination optics 5 is a field lens group 15 that is arranged downstream of the pupil plane 9 behind the pupil-forming optics 8. Downstream of the field lens group 15 is arranged an intermediate image plane 16 which conjugated with the object plane 6. The field lens group 15 is therefore a condenser group. A stop 17 is disposed in the intermediate field plane 16 for defining an edge boundary of the object field 14. The stop 17 is also referred to as REMA (reticle masking system for masking the reticle 7) stop.

[0065] The intermediate image plane 16 is imaged into the object plane 6 by means of an objective group 18 which is also referred to as REMA lens group. The objective group 18 is another optical main group of the illumination optics 5. Another pupil plane 19 is arranged within the objective group 18.

[0066] Fig. 2 shows in a meridional section a collector mirror assembly 20 including a collector mirror 21 to collect the useful light 4 from the radiation source 3 and to guide such useful light 4 along a subsequent illumination light path along the optical axis 2. The collector mirror 21 also is indicated in Fig. 1. The collector mirror 21 has a mirror substrate body 22. Depending upon a respective assignment, a collector mirror 21 may be part of the illumination optics, may be part of the illumination system or may be part of the light source.

[0067] The mirror substrate body 22 includes a mirror basic body 23 carrying a mirror reflection surface 24 for the useful illumination light 4. The mirror reflection surface 24 is embodied as an inner wall surface of the mirror basic body 23. As a rule, the mirror reflection surface 24 has an ellipsoidal shape and transfers a source region of the radiation source 3 into an intermediate focus region not shown in figs 1 and 2. The mirror reflection surface 24 alternatively may have another shape, e.g., a semi-spherical or a parabolic or a hyperboloid shape. Further, the mirror substrate body 22 includes a mirror holding section 25. Such mirror holding section is integrally formed with the mirror basic body 23. The mirror holding section 25 may be formed together with the mirror basic body 23 or may be added afterwards.

[0068] At the holding section 25, the mirror substrate body 22 has a holding section wall thickness H which differs from a further wall thickness W of the mirror substrate body 22.

[0069] In the Fig. 2 embodiment, the holding section wall thickness H is larger than the further wall thickness W. The following relation holds:

[0070] 1.1 < H / W < 10. In particular, H / W ~ 2, i.e., the holding section wall thickness is approximately twice the further wall thickness of the mirror substrate body 22.

[0071] The mirror holding section 25 is embodied as a circumferential collar, in particular as an outer circumferential collar at an outer boundary 26 of the mirror reflection surface 24.

[0072] The collector mirror assembly 20 further has a supporting body 28 which surrounds an outer wall 29 of the mirror basic body 23 of the collector mirror 21. The supporting body 28 may comprise a plurality of cooling channels 30. These cooling channels 30 are designed to guide a cooling fluid to cool the collector mirror 21 via direct thermal contact and / or via radiation.

[0073] The collector mirror assembly 20 further has a plurality of clamping bodies 31 for a clamping connection of the collector mirror 21 with the supporting body 28. Fig. 2 schematically depicts one of these clamping bodies 31. The clamping body 31 is connected with the collector mirror 21 on the one hand and with the supporting body 28 on the other. In particular, the clamping body 31 exerts a clamping force 32 onto the holding section 25. Such mirror holding section 25, i.e., the outer circumferential collar of the mirror substrate body 22, is clamped in between the clamping body 31 and a counter clamping section 33 of the supporting body 28. The counter clamping section 33 may be separate from the supporting body 28 as shown in Fig. 2 or alternatively may be part of the supporting body 28.

[0074] Further, the collector mirror assembly 20 has an actuator 34 to position the collector mirror 21 relative to the supporting body 28 and / or to the light source 3. In the embodiment shown in Fig. 2, the actuator 34 is in effective connection with the mirror substrate body 22, in particular with the mirror holding section 25. Via the actuator 34, translation and / or rotation of the collector mirror 21 relative to the supporting body 28 and / or relative to the light source 3 is possible via at least one translational / rotational degree of freedom. To ensure correct movement along the given degree of freedom, a respective guiding scheme is provided which is not shown in the figure in detail. Depending on the respective embodiment of the actuator 34, the collector mirror 21 may be translated / rotated via exactly one, via exactly two, via exactly three, via exactly four, via exactly five, or via exactly six degrees of freedom. The actuator 34 may include a plurality of independent actuator units, each serving to translate / rotate the collector mirror 21 along exactly one degree of freedom of translation / rotation.

[0075] The collector mirror assembly 20 is part of an illumination system. A part of this illumination system is the illumination optics 5. Such illumination system is part of an optical system including the projection objective 11, i.e., including an imaging optics to image the object field 14 into the image field 14a. With the help of Fig. 3, another embodiment of a collector mirror substrate body 35 is described, which may be used as an alternative of the collector mirror substrate body 22 of Fig. 2. Components, details and functions which already were described above with respect to Figs 1 and 2 in particular, have the same reference numerals and are not described in detail again.

[0076] The mirror substrate body 35 has a mirror basic body 36 and a mirror holding section 37 being embodied as an inner circumferential recess in the mirror substrate body 35. A holding section wall thickness H of the holding section 37 is smaller than the further wall thickness W of the mirror substrate body 35, due to this recess embodiment of the mirror holding section 37. Further shown in fig. 3 is a part of a clamping body 38 for clamping connection of the collector mirror 21 having the mirror substrate body 35 according to fig. 3 against the supporting body 28. In that respect, the clamping function of the clamping body 38 corresponds to that of the clamping body 31 discussed above with respect to fig. 2.

[0077] With the help of Fig. 4, another embodiment of a collector mirror substrate body 39 is described which may be used as an alternative of the collector mirror substrate body 22 of Fig. 2. Components, details and functions which already were described above with respect to Figs 1 and 2 in particular, have the same reference numerals and are not described in detail again.

[0078] A mirror substrate body 39 includes a mirror basic body 40 and a mirror holding section 41 being integrally formed with the mirror basic body 40.

[0079] The mirror substrate body 39 has an inner opening 42 defining an inner boundary of the mirror reflection surface 24. Such inner opening 42 also is present in the mirror substrate bodies 22 and 35, i.e., the embodiments of Figs 2 and 3. Such inner opening 42 serves to mount the radiation source 3.

[0080] In the Fig. 4 embodiment, the mirror holding section 41 is embodied as an inner circular collar at the inner opening 42 of the mirror substrate body 39. At the mirror holding section 41, again, a clamping of the collector mirror 21 with the supporting body 28 is possible. Such clamping can be done via a respective clamping body which clamps the mirror substrate body 39 inbetween such clamping body and the supporting body 28 or, in alternative configuration, clamps the supporting body 28 between such clamping body and the holding section 41.

[0081] In the Fig. 4 embodiment, the holding section wall thickness H is larger than the further wall thickness W.

[0082] With the help of Fig. 5, another embodiment of a collector mirror substrate body 43 is described which may be used as an alternative of the collector mirror substrate body 22 of Fig. 2. Components, details and functions which already were described above with respect to Figs 1 and 2 in particular, have the same reference numerals and are not described in detail again.

[0083] The mirror substrate body 43 has a mirror basic body 44 and a holding section 45 integrally formed thereto, the mirror holding section 45 according to Fig. 5 comprises a sleeve section. Here, again, clamping is possible as described above with respect to the mirror holding section 41 of the Fig. 4 embodiment.

[0084] In the Fig. 5 embodiment, the holding section wall thickness H is larger than the further wall thickness W. With the help of fig. 6, another embodiment of a collector mirror substrate body 46 is described which may be used as an alternative of the collector mirror substrate body 22 of fig. 2. Components, details and functions which already were described above with respect to Figs 1 and 2 in particular, have the same reference numerals and are not described in detail again.

[0085] The mirror substrate body 46 comprises a mirror basic body 47 and a mirror holding section 48.

[0086] In the fig. 6 embodiment, the holding section wall thickness H is smaller than the wall thickness W.

[0087] The following relation may hold:

[0088] 0.1 < H / W < 1. In particular, the following relationship holds: H / W ~ 0.5, i.e., the holding section wall thickness has approximately half of the thickness of the further wall.

[0089] The mirror holding section 48 is embodied as a circumferential outer recess in the mirror basic body 47. Such circumferential outer recess is done at the outer boundary of the mirror basic body 47. The opposing inner boundary of the mirror basic body 47, i.e., the inner boundary of the mirror holding section 48 defines also the inner boundary of the mirror reflection surface 24.

[0090] The recess 49 of the mirror holding section 48 again may be used to insert a clamping body corresponding to that explained with respect to figs 2 to 5 above, and in particular with respect to the clamping body 38 of Fig. 3. With the help of Fig. 7, another embodiment of a collector mirror substrate body 50 is described which may be used as an alternative of the collector mirror substrate body 22 of Fig. 2. Components, details and functions which already were described above with respect to figs 1 and 2 in particular, have the same reference numerals and are not described in detail again.

[0091] The mirror substrate body 50 comprises a mirror basic body 51 and a mirror holding section 52 having an outer circumferential recess 53. The outer circumferential recess 53 is positioned such that an outer circumferential collar 50 of the mirror holding section 52 results which may be used to be clamped with a clamping body comparable to what was described above with reference to the fig. 2 embodiment (holding section 25). In particular, a recess wall 55 of a recess 53 can be used to abut against a counter clamping section 33 of the supporting body 28. Such counter clamping section 33 then counteracts with a clamping body 56 illustrated in fig. 7. The counter clamping section 33 of the supporting body 28 may be formed complementary to the recess 53 of the mirror holding section 52 of the mirror substrate body 50.

[0092] At least a section of the recess wall 55 may be embodied as a vertical wall. Such vertical wall is advantageous against a counter clamping section of the supporting body 28 or to abut against the clamping body. In general, the recess 53 can be of varying shape and may be a vertical wall as this makes it attractive for positioning and clamping.

[0093] Fig. 8 shows a top view of the collector mirror assembly 20 of fig. 2 (viewing direction VIII in fig. 2). Shown are three clamping bodies 31 which are circumferentially equally distributed around the collector mirror 21 to clamp it against the supporting body 28 as described above with reference to fig. 2.

[0094] Further, fig. 8 shows two abutment bodies 57 which are mounted to the supporting body 28 and serve to position the collector mirror 21 relative to the supporting body 28 in the x-direction and the y-direction. To secure such xy-positioning via the abutment bodies 57, the collector mirror assembly 20 further includes a positioning spring (not shown) exerting a positioning pretension force 58 also shown in fig. 8. With such spring, the collector mirror 21 is pushed against the two abutment bodies 57 constraining the collector mirror 21 in two degrees of freedom. The other four degrees of freedom are fixed by the clamping bodies 31. Thus, the position of the collector mirror 21 is fixed completely from a mechanical perspective. The positioning spring on the one hand and the clamping bodies 31 on the other allow geometrical changes of the collector mirror 21 in all degrees of freedom. Such geometrically changes may be due to thermal expansion. A position where the positioning pretension 58 exerts upon the collector mirror 21 on the one hand and the position of the two abutment bodies 57 on the other also are equally distributed around the circumference of the collector mirror 21.

[0095] Fig. 9 shows one of the clamping bodies 31 in a release position, where the mirror holding section 25 is free from, i.e. no more clamped by the clamping body 31.

[0096] Via translation of the clamping body 31 along the z-direction (translation direction 59 in fig. 9) the clamping body 31 can be transferred between the release position shown in fig. 9 and a clamping position where the clamping force 32 is exerted by the clamping body 31 upon the mirror holding section 25.

[0097] Fig. 10 shows details of a further embodiment of a clamping body 60 which may be used as an alternative or in addition to the clamping body 31. The embodiment of the clamping body 60 shown in fig. 10 acts together with the holding section embodiment of fig. 7 above (holding section 53). A mounting section 61 of the clamping body 60 is inserted into a respective recess of the supporting body 28. Such mounting section 61 is surrounded by a compression spring 62 which serves as a clamping tension spring to exert the clamping force 32 onto the holding section 52. The compression spring 62 serves as a clamping tension spring.

[0098] To achieve a radial compliance in a radial direction to the optical axis 2, the clamping body 60 has a body cutout 63 between the main part of the clamping body 60 including the mounting section 61 and a clamping part of the clamping body coming into contact with the mirror holding section.

[0099] Fig. 11 shows a perspective view of an embodiment of the collector mirror assembly 20 using the clamping body 60 according to fig. 10. The most distant of the three clamping bodies 60 is shown in fig. 11 in a release position where the clamping part of the clamping body 60 is turned around a pivot axis 64 running along a mounting section 61 such that the clamping part of the clamping body 60 is free from the mirror holding section 52. The other two clamping bodies 60 are shown in fig. 11 in the clamping position according to fig. 10. The abutment bodies 57 are formed in the fig. 11 embodiment as integral contact parts of the supporting body 28.

[0100] The positioning pretension force 58 (cf. fig. 8) is exerted upon the mirror holding section 52 via a leaf spring 65. Details of such leaf spring 65 which is an example of a pretensioning spring are discussed also with respect to fig. 12.

[0101] The leaf spring 65 has a leaf spring body 66 which is mounted to the supporting body 28 via a mounting block 67. A free end of the leaf spring body 66 contacts in the pretensioning position of the leaf spring 65 an outer wall of the mirror holding section 52 of the mirror substrate body 50 of the collector mirror 21. To enable a movement of the free end of the leaf spring body 66 between a force-free position and a pretensioning position where such free end abuts against the mirror holding 52, the supporting body 28 has a respective cutout 68.

[0102] Fig. 13 shows a further embodiment of a collector mirror assembly 20. Components, details and functions explained above with respect to figs 1 to 12 carry the same reference numerals and are not discussed in detail again.

[0103] The collector mirror 21 in the figure 13 embodiment is held in position relative to the supporting body 28 via three elastic members being embodied as flexure members or holding flexures 69, each having a flexure spring or flexure bar 70 connected at both ends at the supporting body 28. With the three flexure members 69, a floating mount of the mirror basic body 23 relative to the supporting body 28 is given. Between both connection ends, the respective flexure spring 70 abuts against the mirror holding section of the collector mirror 21, e.g. against an outer circumferential wall of the mirror holding section 25. The three holding flexures 69 are equally distributed around the circumference of the mirror holding section 25. With these three holding flexures 69, a floating support of the collector mirror 25 with the supporting body 28 in the xy-plane is realized. Positioning in the z-direction is done via at least one pretensioning spring not shown in fig. 13. Such pretensioning spring may be part of a clamping body similar to the clamping body 60 that is discussed above in particular with respect to fig. 10.

[0104] The flexure spring 70 may contact the mirror basic body via one of the mirror holding section embodiments discussed above, in particular may contact the recess / undercut embodiment of the mirror holding section 52 according to fig. 7.

[0105] Figs. 14 to 16 show a further embodiment of a collector mirror assembly 20. Components, details, and functions explained above with respect to figs 1 to 13, and in particular with respect to fig. 13 carry the same reference numerals and are not discussed in detail again.

[0106] The assembly according to figs 14 to 16 has three flexure members 72 which are used alternatively to the flexure members 70 of the fig. 13 embodiment for floating mount of the mirror basic body 22 of the collector mirror 21 relative to the supporting body 28.

[0107] One of those three flexure members 72 is shown in greater detail in figs 15 and 16. The flexure member 72 includes a basic flexure bar 73 which is integrally connected at both ends at the supporting body 28. The flexure bar 73 has a central mounting section 74 to mount a clamping body 31 or 60 similar to those previously discussed, in particular with respect to figs 9 and 10.

[0108] Fig. 16 shows a cross-section of one of the flexure members 72 through such mounting section 74 and the clamping body 31 or 60. Different to the embodiments of figs 9 and 10, the mounting section 74 of the flexure bar 73 to which a respective mounting section of the clamping body 31, 60 is inserted is part of the flexure member 72 and not part of the main supporting body 28. Between such main supporting body 28 and the flexure member 72 also in the region of the mounting section 74 of the flexure bar 73 a flexure gap 75 remains allowing the whole flexure bar 73 including its mounting section 74 to be flexed towards the main supporting body 28.

[0109] Fig. 17 shows another embodiment of a flexure member 76 which may be used as an alternative to the flexure member 72 according to figs. 14 to 16. Components, details and functions explained above with respect to figs 1 to 16, and in particular with respect to figs 14 to 16 carry the same reference numerals and are not discussed in detail again.

[0110] A flexure bar 73 of the flexure member 76 is integrally connected via one bar end to the main mirror supporting body 28. The other end of the flexure bar 73 of the flexure member 76 including the mounting section 74 is a free end.

[0111] Fig. 18 shows another embodiment of a flexure member 77 which may be used as an alternative to the flexure member 72 according to figs. 14 to 17. Components, details and functions explained above with respect to figs 1 to 17, and in particular with respect to figs 14 to 17 carry the same reference numerals and are not discussed in detail again.

[0112] The flexure bar 73 of the flexure member 77 has two bar parts 731, 732, each of which is integrally connected to the main supporting body 28 via one bar end. Both flexure bar parts 731, 732 have a mounting section 74i, 742 capable to optionally mount a clamping body 31 or 60, respectively. Between those two mounting sections 74i, 742 which constitute the free ends of the flexure bars 731, 732 a gap 78 remains.

[0113] Figs 19 and 20 show further embodiments of a flexure member 79 which may be used as an alternative to the flexure member 72 according to figs. 14 to 18. Components, details and functions explained above with respect to figs 1 to 18, and in particular with respect to figs 14 to 18 carry the same reference numerals and are not discussed in detail again.

[0114] A clamping body 80 which is used with the embodiment of the flexure member 79 is mounted with its mounting section 61 with the main supporting body 28 according to the description given above in particular with respect to fig. 10. In the clamping position where the clamping body 80 exerts a clamping force 81 (cf. fig. 20) to the holding section 25 of the collector mirror 21, the clamping body 80 contacts the holding section 25 via an extension arm 82. The length of the extension arm 82 is such that it spans over a contact section 83 of the flexure bar 73 of the flexure member 76 where the holding section 25 of the mirror substrate body 22 of the collector mirror 21 contacts the flexure bar 73. During floating of the floating mount given by the three flexure members 76 according to the fig. 19 / 20 embodiment, a relative movement between the holding section 25 of the collector mirror 21 on the one hand and the extension arm 82 of the clamping body 80 on the other is enabled. During such relative movement, the clamping body 80 maintains its clamping force 81 onto the holding section 25.

[0115] Fig. 21 to 23 show further embodiments of a collector mirror assembly 20. Components, details, and functions explained above with respect to figs 1 to 20 carry the same reference numerals and are not discussed in detail again.

[0116] A collector mirror assembly 20 according to figs 21 to 23 comprises three elastic or flexure members 84 which may be used alternatively to the flexure members described above with respect in particular to figs 13 to 20. The upper view according to fig. 21 illustrates the circumferential arrangement of the three flexure members 84. Fig. 22 shows two of these three flexure members 84 according to the angled cutting line of fig. 21. Fig. 23 shows one of these flexure members 84 in an enlarged sectional view.

[0117] The flexure member 84 includes a flexure spring 85 extending mainly parallel to the optical axis 2 of the collector mirror 21. The flexure spring 85 of the flexure member 84 extends between the main supporting body 28 of the collector mirror assembly 20 and a supporting section 86 which contacts the mirror holding section 25 of the collector mirror 21. Such contact may be given via a gravitational force G via which the collector mirror 21 rests upon the three flexure members 84. Alternatively or in addition, the holding section 25 of the collector mirror 21 may be clamped onto the supporting section 86 of the flexure member 84 via a clamping body as discussed above in particular with respect to the clamping bodies 31 and 60. Via the three flexure members 84, again, a floating mount of the mirror basic body 23 relative to the supporting body 28 is given.

[0118] Fig. 24 shows another embodiment of a flexure member 87 which may be used as an alternative to the flexure member 84 according to figs. 21 to 23. Components, details and functions explained above with respect to figs 13 to 23, and in particular with respect to fig 23 carry the same reference numerals and are not discussed in detail again.

[0119] Whereas in the fig. 23 embodiment, the supporting body 28 is arranged (in the orientation according to figs. 22 and 23) below the mirror holding section 25, in the fig. 24 embodiment the supporting body 28 which is formed as a ring structure is located above the mirror holding section 25. In the fig. 24 embodiment, the mirror holding section 25 embodied as an outer circumferential collar is suspended on the supporting section 86 of a flexure member 87. A flexure spring 85 of the flexure member 87 is located at the outer circumference of the mirror holding section 25.

[0120] Again, the three flexure members 87 give a floating mount of the mirror basic body 23 relative to the supporting body 28.

[0121] Fig. 25 shows another embodiment of a flexure member 88 which may be used as an alternative to the flexure member 84 according to figs. 21 to 23. Components, details and functions explained above with respect to figs 13 to 24, and in particular with respect to fig 23 carry the same reference numerals and are not discussed in detail again.

[0122] In the fig. 25 embodiment, the flexure spring 85 of the flexure member 88 has the cross section of the character “U”. Due to this, the mirror holding section 25 on the one hand and the main supporting body 28 on the other which, again, is embodied as ring structure are on the same level.

[0123] Again, the three flexure members 88 give a floating mount of the mirror basic body 23 relative to the supporting body 28.

[0124] Fig. 26 shows a further embodiment of a collector mirror assembly 20. Components, details, and functions explained above with respect to figs 1 to 25 carry the same reference numerals and are not discussed in detail again.

[0125] The collector mirror assembly 20 according to fig. 26 has three elastic members 89 for floating mount of the mirror basic body 23 of the collector mirror 21 relative to the supporting body 28. The elastic members 89 are embodied as compression springs which are inserted into circumferential recesses 90 which are located in the main supporting body 28. The respective compression spring of the elastic member 89 extends between the bottom of such recess 90 and a circumferential portion of the mirror holding section 25 of the collector mirror 21. Between the whole circumference of the mirror basic body 23 on the one hand and the ring-like supporting body 28 on the other, a circumferential gap 91 is present allowing the floating mount of the collector mirror 20 relative to the supporting body 28 via the three elastic members 89.

[0126] Fig. 27 shows a further embodiment of a collector mirror assembly 20. Components, details, and functions explained above with respect to figs 1 to 26 and in particular with respect to fig. 26 carry the same reference numerals and are not discussed in detail again. Compared to the fig. 26 embodiment which has three elastic members 89, the fig. 27 embodiment of the collector mirror assembly 20 has twelve elastic members 89 which are arranged equidistantly circumferentially around the holding section 25 of the collector mirror 21. These twelve elastic members 89, again, give a floating mount of the mirror basic body 23 relative to the supporting body 28.

[0127] By means of the projection exposure apparatus 1, at least a part of the reticle 7 is imaged onto a region of a light-sensitive layer on the wafer 13 for lithographic production of a microstructured or nanostructured component.

[0128] Depending on whether the projection exposure apparatus 1 is a scanner or a stepper, the reticle 7 and the wafer 13 are either displaced continuously in the y-direction in a temporally synchronized maimer (scanner) or they are displaced gradually (stepper).

Claims

Claims1. Collector mirror (21) for lithography having a mirror substrate body (22; 35; 39; 43; 46; 50) comprising— a mirror basic body (23; 36; 40; 44; 47; 51) having a mirror reflection surface (24) for illumination light (4),— at least one mirror holding section (25; 37; 41; 45; 48; 52) being integrally formed with the mirror basic body (23; 36; 40; 44; 47; 51), wherein the mirror substrate body (22; 35; 39; 43; 46; 50) has at the mirror holding section (25; 37; 41; 45; 48; 52) a holding section wall thickness (H) which differs from a further wall thickness (W) of the mirror substrate body (22; 35; 39; 43; 46; 50), wherein the mirror holding section (25; 37; 41; 45; 48; 52) is realized such that holding forces which are transmitted via the mirror holding section are below a certain force threshold.

2. Collector mirror according to claim 1, wherein the holding section wall thickness (H) is larger than the further wall thickness (W).

3. Collector mirror according to claim 1 or 2, wherein the mirror holding section (25; 41; 45; 52) is embodied as a circumferential collar.

4. Collector mirror according to one of claims 1 to 3, wherein the mirror substrate body (39; 43) has an inner opening (42) defining an inner boundary of the mirror reflection surface (24), wherein the holding section (41; 45) is embodied as an inner circular collar at the inner opening (42) of the mirror substrate body (39; 43).

5. Collector mirror according to one of claims 1 to 4, wherein the mirror holding section (45) comprises a sleeve section.

6. Collector mirror according to one of claims 1 to 5, wherein the holding section wall thickness (H) is smaller than the further wall thickness (W).

7. Collector mirror assembly (20) having a collector mirror (21) according to one of claims 1 to 6 and having a supporting body (28), surrounding an outer wall (29) of the mirror basic body (23; 36; 40; 44; 47; 51).

8. Collector mirror assembly (20) for lithography according to claim 7, wherein the mirror basic body (23) is mounted floating relative to the supporting body (28).

9. Collector mirror assembly according to claim 8, having at least three elastic members (69; 72; 76; 77; 79; 84; 87; 88; 89) for floating mount of the mirror basic body (23) relative to the supporting body (28).

10. Collector mirror assembly according to claim 9, wherein the elastic members (69; 72; 76; 77; 79; 84; 87; 88) are flexure members.

11. Collector mirror assembly according to one of claims 8 to 10, having a collector mirror (21) according to one of claims 1 to 6 and a supporting body (28) surrounding an outer wall (29) of the mirror basic body (23).

12. Collector mirror assembly according to one of claims 7 to 11, having at least one cooling channel (30) at the supporting body (28).

13. Collector mirror assembly according to one of claims 7 to 12, having at least one clamping body (31; 38; 60; 80) for clamping connection of the collector mirror (21) with the supporting body (28), wherein the clamping body (31; 60; 80) is connected with the collector mirror (21) and with the supporting body (28), respectively.

14. Collector mirror assembly according to claim 13, wherein the clamping body (60) is connected with the supporting body (28) and / or with the collector mirror (21) via a clamping spring (62).

15. Collector mirror assembly according to one of claims 9 to 14, wherein the mirror basic body (23) is fixed to at least one of the elastic members (72; 76) via a clamping body (31; 60; 80).

16. Collector mirror assembly according to one of claims 7 to 15, having at least one actuator (34) to position the collector mirror (21) relative to the supporting body (28) and / or to position the collector mirror (21) relative to a light source (3)17. Illumination system having a collector mirror assembly (20) according to one of claims 7 to 16, having an illumination optics (5) for illumination of an object field (14) in which an object (7) to be illuminated is arrangeable, with the illumination light (4) collected with the collector mirror (21).

18. Optical system having an illumination system according to claim 17 and having an imaging optics (11) to image the object field (14) into animage field (14a), in which a substrate (13) to be illuminated is arrangeable.

19. Projection exposure system (1) having an optical system according to claim 18 and having a light source (3) to generate the illumination light (4).

20. Method of producing structured components comprising the following steps: providing a wafer (13) to at least part of which is applied a layer of a light-sensitive material; providing a reticle (7) which has structures to be imaged; providing a projection exposure apparatus (1) according to claim 19; projecting at least a part of the reticle (7) to a region of the layer on the wafer (13) by means of the projection exposure apparatus (1).

21. Structured component which is produced with a method according to claim 20.

Images