Microlithography projection objective

Abstract

Microlithography projection objectives for imaging into an image plane a pattern arranged in an object plane are described with respect to suppressing false light in such projection objectives.

Claims

1. A projection objective, comprising: a plurality of optical components configured to image a pattern in an object plane along an imaging beam path through the projection objective into an image plane, each optical component comprising an optically operative surface; and a first shield having an adjustable position, wherein: the plurality of optical components comprises a first optical component comprising a first optically operative surface configured so that, during the operation of the projection objective, the first optically operative surface comprises a first surface region not used by the imaging beam path to image the pattern into the image plane; the first shield is configured to mask out the first surface region to suppress false light; and the projection objective is a microlithography projection objective, and wherein one of the following holds: i) the first shield is not located in a pupil plane of the projection objective or a field plane of the projection objective; ii) the projection objective has a pupil plane and an intermediate image plane, and the first shield is between the pupil plane and the intermediate plane; and iii) the projection objective has a first pupil plane, a second pupil plane and an intermediate image plane, the intermediate image plane is between the first and second pupil planes, the second pupil plane is between the intermediate image plane and the image plane, and the first shield is between the intermediate image plane and the second pupil plane.

2. The projection objective of claim 1, wherein the first shield comprises a plate in an immediate vicinity of the first optically operative surface.

3. The projection objective of claim 1, wherein the first shield comprises an aperture in an immediate vicinity of the first optically operative surface, and the aperture has an opening adapted to a cross-sectional shape of the imaging beam path at the aperture.

4. The projection objective of claim 3, wherein the opening in the aperture is substantially rectangular.

5. The projection objective of claim 1, wherein the first shield comprises a shielding coating on the first surface region.

6. The projection objective of claim 1, wherein the first shield is reflective for a wavelength of the light used to image the pattern during operation of the projection objective.

7. The projection objective of claim 1, wherein the first shield is absorbing for a wavelength of the light used to image the pattern during operation of the projection objective.

8. The projection objective of claim 1, wherein the first optically operative surface is a near-field surface.

9. The projection objective of claim 1, wherein the first optical component comprises a mirror.

10. The projection objective of claim 1, wherein the first optical component comprises a lens.

11. The projection objective of claim 1, further comprising a second shield, wherein: the plurality of optical components comprises a second optical component comprising a second optically operative surface configured so that, during operation of the projection objective, a second surface region of the second optically operative surface is not used by the imaging beam path for imaging the pattern into the image plane; and the second shield is configured to mask out the second surface.

12. The projection objective of claim 1, further comprising a second shield configured to shield over-aperture light from the object plane.

13. The projection objective of claim 1, wherein the first shield is not located in a pupil plane of the projection objective or a field plane of the projection objective.

14. The projection objective of claim 1, wherein the projection objective has a pupil plane and an intermediate image plane, and the first shield is between the pupil plane and the intermediate plane.

15. The projection objective of claim 14, wherein the pupil plane is between the intermediate image plane and the image plane.

16. The projection objective of claim 1, wherein: the projection objective has a first pupil plane, a second pupil plane and an intermediate image plane; the intermediate image plane is between the first and second pupil planes; the second pupil plane is between the intermediate image plane and the image plane; and the first shield is between the intermediate image plane and the second pupil plane.

17. A projection objective, comprising: a plurality of optical components configured to image a pattern in an object plane along an imaging beam path through the projection objective into an image plane, each optical component comprising an optically operative surface; and a first shield having a variable active cross-section; wherein: the plurality of optical components comprises a first optical component comprising a first optically operative surface configured so that, during the operation of the projection objective, the first optically operative surface comprises a first surface region not used by the imaging beam path to image the pattern into the image plane; the first shield is configured to mask out the first surface region to suppress false light; and the projection objective is a microlithography projection objective, and wherein one of the following holds: i) the first shield is not located in a pupil plane of the projection objective or a field plane of the projection objective; ii) the projection objective has a pupil plane and an intermediate image plane, and the first shield is between the pupil plane and the intermediate plane; and iii) the projection objective has a first pupil plane, a second pupil plane and an intermediate image plane, the intermediate image plane is between the first and second pupil planes, the second pupil plane is between the intermediate image plane and the image plane, and the first shield is between the intermediate image plane and the second pupil plane.

18. The projection objective of claim 17, further comprising an aperture of the projection objective configured to limit the imaging beam path, wherein the projection objective is configured so that the active cross-section of the first shield and the aperture are set in common.

19. The projection objective of claim 17, wherein the projection objective is configured so that setting the active cross-section of the first shield is a function of a size of the image field.

20. The projection objective of claim 17, wherein the projection objective is configured so that setting the active cross-section of the first shield is a function of an illumination setting of the projection objective.

21. The projection objective of claim 17, wherein the first shield comprises a plate in an immediate vicinity of the first optically operative surface.

22. The projection objective of claim 17, wherein the first shield comprises an aperture in an immediate vicinity of the first optically operative surface, and the aperture has an opening that is adapted to a cross-sectional shape of the imaging beam path at the aperture.

23. The projection objective of claim 22, wherein the opening is substantially rectangular.

24. A projection objective, comprising: a plurality of optical components configured to image a pattern in an object plane along an imaging beam path through the projection objective into an image plane; and a first shield, wherein: the plurality of optical components comprises a first optical component comprising a first optically operative surface configured so that, during the operation of the projection objective, the first optically operative surface comprises a first surface region not used by the imaging beam path to image the pattern into the image plane; the first shield has at least one property selected from the group consisting of an adjustable position and a variable active cross-section; the first shield is configured to mask out the first surface region to suppress false light; and the projection objective is a microlithography projection objective, and wherein one of the following holds: i) the first shield is not located in a pupil plane of the projection objective or a field plane of the projection objective; ii) the projection objective has a pupil plane and an intermediate image plane, and the first shield is between the pupil plane and the intermediate plane; and iii) the projection objective has a first pupil plane, a second pupil plane and an intermediate image plane, the intermediate image plane is between the first and second pupil planes, the second pupil plane is between the intermediate image plane and the image plane, and the first shield is between the intermediate image plane and the second pupil plane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention are illustrated in the drawings and explained in more detail hereafter with reference thereto. In the drawings:

(2) FIG. 1 shows a first exemplary embodiment of a projection objective in side view;

(3) FIG. 2 shows an enlarged section of the projection objective in FIG. 1 in the region of the beam deflecting device of the projection objective;

(4) FIG. 3 shows a further exemplary embodiment of a projection objective in side view;

(5) FIG. 3A shows a section of the projection objective in FIG. 3 on an enlarged scale;

(6) FIG. 4 shows a projection exposure machine comprising the projection objective in FIG. 1 in a schematic illustration;

(7) FIG. 5 shows the projection objective in FIG. 1 with a modification regarding the false light suppression;

(8) FIG. 6 shows a further exemplary embodiment of a projection objective with measures for false light suppression;

(9) FIG. 7 shows a yet further exemplary embodiment of a projection objective with measures for false light suppression;

(10) FIG. 8 shows a yet further exemplary embodiment of a projection objective with measures for false light suppression;

(11) FIG. 9 shows a yet further exemplary embodiment of a projection objective with measures for false light suppression;

(12) FIG. 10 shows a yet further exemplary embodiment of a projection objective with measures, for false light suppression; and

(13) FIG. 11 shows a yet further exemplary embodiment of a projection objective with measures for false light suppression; and

(14) FIG. 12FIG. 12A shows a yet further exemplary embodiment of a projection objective according to another aspect of the invention.

DETAILED DESCRIPTION OF PREFERRED EXEMPLARY EMBODIMENTS

(15) FIG. 1 shows a microlithography projection objective provided with the general reference numeral 10 intended for imaging into an image plane 14 a pattern (not shown) arranged in an object plane 12.

(16) The projection objective 10 has a first objective part 16, a second objective part 18 and a third objective part 20.

(17) The first objective part 16 is dioptric and is formed by a lens L.sub.1.

(18) The second objective part 18 is catadioptric and has lenses L.sub.2, L.sub.3 and a concave mirror M.sub.2.

(19) The third objective part 20 is dioptric and has lenses L.sub.4 to L.sub.17 and an end plate L.sub.18.

(20) As shown in FIG. 1, the light propagation direction in the second objective part 18 differs from the light propagation direction in the first objective part 12 and in the third objective part 20. To this end, the projection objective 10 has a beam deflecting device 22, that is formed in the exemplary embodiment shown by two folding mirrors M.sub.1 and M.sub.3. The folding mirror M.sub.1 deflects the light beam coming from the first objective part 16 into the second objective part 18 toward the mirror M.sub.2, and the second folding mirror M.sub.3 deflects the light beam coming from the second objective part 18 into the third objective part 20.

(21) The light propagation direction in the third objective part 20 corresponds to that in the first objective part 16.

(22) A shield 24 that is non-transmissive to light is provided in the region of the beam deflecting device 22 in order to avoid a direct light leakage froth the first objective part 16 into the third objective part 20, for example reflections from the surfaces of the lens L.sub.1. In particular, the shield 24 prevents light leaking from the first objective part 16 into the third objective part 20 with the omission of the second objective part 18, that is to say prevents it from not going through the lenses L.sub.2, L.sub.3 and being reflected at the mirror M.sub.2.

(23) As already mentioned, the beam deflecting device 22 is formed by the two folding mirrors M.sub.1 and M.sub.3, whose reflecting surfaces are arranged at an angle to one another, as is illustrated in FIGS. 1 and 2. The two reflecting surfaces, that is to say the mirrors M.sub.1 and M.sub.3 are arranged in accordance with the beam deflection to be effected at an angle (here approximately 90) to one another, the shield 24 extending, starting from the angle vertex of the two mirrors M.sub.1 and M.sub.3 in the direction of the second objective part 18.

(24) The shield 24 is a plate 26, for example, a metal plate, that absorbs in the wavelength region of the light used. In addition, this plate can be provided with an absorbing layer. Instead of a metal plate, however, it is also possible to use an element made from another material that may be coated so as to be absorbing. In accordance with FIG. 2, the two mirrors M.sub.1 and M.sub.3 are slightly apart from one another at the angle vertex such that the plate 26 can be positioned there and does not mask out the useful light.

(25) The shield 24 is designed and arranged such that it does not limit or restrict the imaging beam path, that is to say the beam path of the light that is to be used for imaging. The positioning and extent of the plate 26 in the direction of the light propagation into the second objective part 18 are to be designed correspondingly.

(26) A further shield 28 is arranged in the region of an intermediate image 30, which is produced in the third objective part 20, in order to further reduce the level of stray light in the projection objective 10.

(27) The shield 28 comprises a stray light stop 32 that reduces the passage of stray light. The stray light stop 32 is, however, to be distinguished from a system aperture stop 34 that serves to limit the imaging beam path. The stray light stop 32, by contrast, does not limit the imaging beam path, but serves to reduce stray light fractions in the projection objective 10.

(28) It is preferably provided that the shield 24 and/or the shield 28 can be adjusted in position, and/or can be variably set with regard to its active cross section. For example, the plate 26 of the shield 24 could be movable and of variable length such that the optimum position and the optimum active cross section of the plate 26 can be set in order to reduce stray light. Adjusting the position and/or setting of the active cross section of the stray light shield is preferably performed as a function of the illumination mode (setting), of the aperture of the objective and/or of the object field size that is used.

(29) It could be provided, for example, in the case of the stray light stop 32 to vary the opening cross section of the stray light stop 32 and/or to configure the stray light stop 32 such that it can be adjusted in position so that the stray light stop 32 can be brought into the optimum position.

(30) It is self-evident that further shields can be provided in the projection objective 10 in order to reduce the level of stray light in the projection objective 10.

(31) It has emerged that a stray light reduction of approximately 30% and more is within the range of the possible with the aid of suitably mounted shields.

(32) FIG. 3 illustrates a further microlithography projection objective 40 for imaging a pattern (not illustrated) arranged in an object plane 42 in an image plane 44.

(33) The projection objective 40 is disclosed in document WO 2004/019128 A2, to which reference may be made for a more accurate description of the design.

(34) Like the projection objective 10 the projection objective 40 is a catadioptric projection objective, the projection objective 40 having a first objective part 46 with a plate L.sub.1 and lenses L.sub.2 to L.sub.11, a second objective part 48 with lenses L.sub.12, L.sub.13 and a mirror M.sub.2 and a third objective part 50 with lenses L.sub.14, to L.sub.28.

(35) A beam deflecting device 52 that, as in the case of the exemplary embodiment in FIG. 1, comprises a folding mirror M.sub.1 and a folding mirror M.sub.3 is arranged between the first objective part 46 and the second objective part 48 or the second objective part 48 and the third objective part 50.

(36) In the case of the projection objective 40, as well, there is provided in the region of the deflecting device 52 a shield 54, comparable to the shield 24 of the projection objective 10, which has the effect of preventing stray light leaking from the first objective part 46 into the third objective part 50.

(37) An enlarged section of the projection objective 40 in the region of the beam deflecting device 52 is illustrated in FIG. 3A. In addition to the shield 54, in the case of the projection objective 40 there are provided a further shield 54a and a further shield 54b that are respectively arranged in the region of an intermediate image of the projection objective 40. The shields 54a and 54b are designed as stray light stops.

(38) For the rest, reference may be made to the description of the shield 24 in FIG. 1 with regard to the configuration of the shield 54, that is to say the configuration of the shield 54 corresponds to that of the shield 24.

(39) The general reference 60 in FIG. 4 indicates a projection exposure machine in which, for example, the projection objective 10 is used. The projection exposure machine comprises a laser light source 62 with a device 64 for narrowing the bandwidth of the laser. An illumination system 66 produces a large, sharply delimited and very homogenously illuminated image field that is adapted to the telecentric requirements of the downstream projection objective 10. The illumination system 66 has devices for selecting the illumination mode and can, for example, be switched between conventional illumination with a variable degree of coherence, annular field illumination and dipole or quadrupole illumination. Arranged after the illumination system is a device 68 for holding and manipulating a mask 70, such that the mask 70 lies in the object plane 12 of the projection objective 10 and can be moved in this plane for scanning operation. The device 68 correspondingly comprises the scanning drive.

(40) Following after the object plane 12 is the projection objective 10 that projects an image of the mask 70 on a reduced scale onto a substrate or wafer 72 that is covered with a photoresist layer and is arranged in the image plane 14 of the projection objective 10. The substrate or the wafer 72 is held by a device 74 that comprises a scanner drive in order to move the wafer synchronously with the mask 70. All the systems are controlled by a control unit 74. The design of such systems is, like their mode of operation, known per se, and will therefore not be described in more detail here.

(41) In the case of a method for producing semiconductor components and other finely structured subassemblies, the mask 70 is provided with a prescribed pattern (not illustrated). Via the illumination device 66, the mask 70 is illuminated with ultraviolet light of a predetermined wavelength from the laser 62. It is possible in this case to set various illumination modes that are sufficiently well known from the literature. The pattern of the mask 70 is then imaged via the projection objective 10 onto the substrate or the wafer 72 and into the image plane 14 of the projection objective 10. Various aperture openings can be set in this case.

(42) FIG. 5 shows, once again, the projection objective 10 in FIG. 1, further measures for false light suppression being provided at the projection objective 10.

(43) In order to suppress false light, the shields to be described below serve the purpose of masking out the respectively unused surface regions of the optical components to which these shields are assigned. The function of these shields is therefore different from the shield 24, that has already been described above, and whose function consists in preventing the propagation of light from the first objective part 16 into the third objective part 20 with the omission of the second objective part 18.

(44) According to FIG. 5, the lens L.sub.5 has a surface region U.sub.L5 that is not used by the imaging beam path for imaging the object plane 12 into the image plane 14. A shield 80 that masks out the unused surface region U.sub.L5 of the lens L.sub.5 in order to suppress false light is assigned to this unused surface region U.sub.L5. The shield 80 is designed in the form of a coating 82 that is, in particular, absorbing for the wavelength of the light used for imaging. The absorbance of the shield 80 is in this case at least approximately 95%, preferably at least approximately 98%. The shield 80 in the form of the coating 82 can, however, also have alternatively or additionally reflecting properties.

(45) The shield 80 further preferably has photocatalytic properties in order to decompose contaminants that are deposited on it, for example hydrocarbons. The gas space of the projection objective 10, which is located between the optical components, is thereby freed from these contaminants.

(46) The lens L.sub.5 is located in the vicinity of a field plane, specifically in the vicinity of the intermediate image 30. However, by contrast with the stray light stop 32, the shield 80 is assigned directly to the lens L.sub.5 and even applied, in the form of the coating 82, directly to the lens L.sub.5.

(47) A further optical component that is suitable for being assigned a shield for suppressing false light is the lens L.sub.6, which has a surface region U.sub.L6 not used by the imaging beam path. The lens L.sub.6 is correspondingly assigned a shield 84 that, in turn, is applied in the form of a coating 86 on the optically active surface of the lens L.sub.6.

(48) The last lens element L.sub.18, which is directly adjacent to the image plane 14, has a surface region U.sub.L18 not used by the imaging beam path, as is illustrated in FIG. 5. A further shield 88, which is formed from a coating 90, is correspondingly assigned on both sides to the last lens element L.sub.18. In the case of the last lens element L.sub.18, the coating 90 is formed annularly thereon such that the useful light can penetrate to the image plane 14 through the opening in the shield 88 in the form of the coating 90.

(49) FIG. 6 shows a further catadioptric projection objective 100, in which, as described previously with reference to FIG. 5, measures are provided for false light suppression. The projection objective 100 is disclosed in US 2005/0190435 A1 to which reference may be made for a more accurate description of the design.

(50) The projection objective 100 images an object plane 101 into an image plane 102. The projection objective 100 produces between the object plane 101 and the image plane 102 two intermediate images 103 and 104 that are located in a catadioptric objective part 105, upstream of which a refractive objective part 106 is located, and downstream of which a refractive objective part 107 is located.

(51) Among the plurality of optical components of the projection objective 100, which comprises lenses and two mirrors, are ones whose at least one optically operative surface has a surface region that, during operation of the projection objective, is not used by the imaging beam path for imaging the object plane 101 into the image plane 102. These optical components are suitable for being directly assigned to a shield.

(52) A lens 108 that is assigned a shield 110 in the form of a coating 112 belongs to these optical components. The coating 112 is applied to the optically operative surface, on the image side, of the lens 108, and preferably has, in turn, the properties of the coatings 82, 86 and 90, which have already been described with reference to FIG. 5.

(53) A mirror 114 of the projection objective 100 likewise has a surface region not used by the light and which is provided with a shielding coating 116.

(54) A lens 118 directly adjacent to the mirror 114 has an optically operative surface that has a surface region not used by the imaging beam path, and that is correspondingly provided with a shielding coating 120.

(55) Finally, a last lens element 122 is likewise provided with a shielding coating 124.

(56) The abovenamed optical components, which are assigned a shield as described, are all near the field, the lenses 108, 118 and the mirror 116 being arranged in the vicinity of the intermediate images 103 and 104, while the last lens element 122 is arranged in the vicinity of the image plane 102. Such near-field optical components are suitable, in particular, for being directly assigned a shield that, for the purpose of suppressing false light, masks out the respectively unused surface region of the optically operative surface of the respective optical component.

(57) FIG. 7 shows a further projection objective 200, in the case of which measures comparable to FIGS. 5 and 6 are provided in order to suppress false light. The projection objective 200 is likewise disclosed in US 2005/0190435 A1.

(58) The projection objective 200 has a plurality of optical components that image an object plane 201 into an image plane 202. The projection objective 200 has a refractive first objective part 210, a catoptric second objective part 220, that is formed from two mirrors 221 and 222, and a refractive third objective part 230.

(59) An intermediate image 203 and an intermediate image 204 are produced in the catoptric objective part 220.

(60) A last lens 232 of the first objective part 210 is provided with a shielding coating 234. A first lens 236 of the third objective part 230 is provided with a shielding coating 238. A last lens element 240 is provided with a shielding coating 242.

(61) Here, as well, near-field optical components have been selected for the measures for suppressing false light.

(62) Finally, FIG. 8 shows a further projection objective 300, in the case of which measures are provided for suppressing false light. The projection objective 300 is likewise disclosed in US 2005/0190435 A1.

(63) The projection objective 300 is a catadioptric projection objective that images an object plane 301 into an image plane 302. The projection objective 300 has a refractive first objective part 310, a catoptric second objective part 320 and a refractive third objective part 330.

(64) The catoptric objective part 320 has four mirrors 306, 307 and 321, 322.

(65) The projection objective 300 produces intermediate images in the catoptric objective part 320.

(66) A lens 332 that is located in a position near the field has a surface region that is not used by the imaging beam path and is provided with a shielding coating 334. A further lens 336 is provided with a shielding coating 338 and a yet further lens 340 is provided with a shielding coating 342.

(67) A last lens element 344 is likewise provided with a shielding coating 346.

(68) Particularly when such projection objectives are designed as immersion objectives, the last lens elements, for example the lens element 344, are preferably provided with a coating that protects the last lens element 344 against degradation by the immersion liquid. In such a case, this protective coating can, in particular, also be designed with a shielding action, that is to say the protective layer then serves not only to protect the last lens element 344, but also to suppress false light.

(69) FIGS. 9 to 11 show projection objectives in the case of which measures are provided for false light suppression in accordance with the invention.

(70) The measures for false light suppression that are taken in the case of the projection objectives that are to be described below are based on the following principle. In the case of a projection objective that has at least one mirror, an imaging beam path that can be used to image the pattern into the image plane can have in the region of the at least one mirror beam path segments that run obliquely relative to one another and overlap one another at least partially in an overlap region. The beam path segments are spaced apart from one another by a gap or free space outside the overlap region. A shield is arranged in this case in the gap in order to suppress false light. When such a projection objective has a number of such gaps or free spaces between the beam path segments or light bundles, it is preferably possible to introduce into each of these free spaces a shield, for example, in the form of one or more stray light stops, such that these free spaces or gaps are no longer available for the propagation of false light. False light can be effectively suppressed in this way.

(71) FIG. 9 shows a projection objective 400, that has between an object plane 402 and an image plane 404 a first catadioptric objective part 406 and a second dioptric objective part 408. The projection objective 400 is described in document WO 2004/107011 A1, in FIG. 5 thereof.

(72) The catadioptric objective part 406 has a first mirror 410 and a second mirror 412.

(73) In order to suppress the propagation of false light, a first shield 414 is provided in the form of a stray light stop 416, and a second shield 418 is provided in the form of a stray light stop 420. The stray light stops 416 and 420, which can also be designed as sections of a stray light stop of a unipartite design, are, as emerges from FIG. 9, located in the vicinity of the mirrors 410 and 412, the stray light stop 416 extending into the region between the mirrors 410 and 412. The stray light stop 420 also has a section 422 that projects into the region between the mirrors 410 and 412. The stray light stops 416 and 420 have been installed such that the free space between the light bundles is filled between the two mirrors 410 and 412. Sections 416a and 420a, extending radially relative to the optical axis 440, of the stray light stops 416 and 420 prevent false light from passing from the object plane 402 along the first mirror 410 or along the second mirror 412 while omitting the latter, and prevent the lenses from imaging the second objective part 408 onto the image plane 404.

(74) FIG. 10 shows a projection objective 500 that is likewise shown in the abovenamed document WO 2004/107011 A1, in FIG. 9 thereof, and is described in that document.

(75) The projection objective 500 has between an object plane 502 and an image plane 504 four mirrors 506, 508, 510 and 512 that belong to two objective parts 514 and 516 of the projection objective 500 from which the projection objective 500 is constructed.

(76) Shields 518, 520 and 522 are provided in the case of the projection objective 500 in order to suppress the propagation of false light. The shield 518 is a stray light stop 524 that has sections 526, 528 and 530 that can be designed as one subassembly, appropriate passages being provided in the stray light stop 424 for the imaging light provided for imaging. The shields 520 and 522 are likewise designed in the form of stray light stops that are arranged in the free space between light bundles of the imaging light.

(77) Finally, FIG. 11 shows a projection objective 600, that is illustrated in the abovementioned document WO 2004/107011 A1 in FIG. 14 thereof, and is described in that document.

(78) The projection objective has a total of six mirrors between an object plane 602 and an image plane 604, specifically in the direction of the light propagation: a first mirror 606, a second mirror 608, a third mirror 610, a fourth mirror 612, a fifth mirror 614 and a sixth mirror 616.

(79) In order to prevent the propagation of false light in the projection objective 600, a number of shields are arranged in the form of stray light stops 618, 620, 622 and 624 in the region of the mirrors 606 to 616, and these in turn shield the free space between the light bundles to be used for imaging against the propagation of false light.

(80) FIG. 12 shows another embodiment of a microlithography projection objective 700 for imaging a pattern arranged in an object plane 702 into an image plane 704.

(81) The projection objective 700 comprises a plurality of optical components 705 to 733, wherein the optical components 713, 717 and 718 are mirrors and the remaining components of the optical component 705 to 733 are lenses.

(82) The projection objective 700 further has a first pupil plane 736 in which a first aperture stop 738 is arranged. The aperture stop 738, which is adjustable in cross section defines the system or design aperture of the projection objective 700. A second pupil plane 740 is present between the optical components 707 and 708.

(83) In the illustration of FIG. 12, two field points 742 and 744 of the object plane 702 are shown which illustrate the illuminated area of the pattern in the object plane 702. Starting from the field points 742 and 744, light rays propagate through the optical components 705 to 733 and reach the image plane 704 in an area 746. The light rays which reach the image plane 746 in the area 746 are used for imaging the pattern arranged in the object plane 702 into the object plane 704.

(84) As shown in FIG. 12, there is a ray 748 starting from field point 742 in the object plane 702 which starts with an aperture which is larger than the aperture of the other rays, for example ray 749, which also start from the field point 742. Ray or rays 748 is/are called an over-aperture ray.

(85) FIG. 12a shows the first four optical components 705 to 708 in an enlarged scale, showing the rays starting from field points 742 and 744 in more detail.

(86) The over-aperture ray 748 which actually is a small bundle of rays, propagates through the projection objective 700 partially separated from the rays used for imaging, and partially not separated from the rays used for imaging, the latter reaching the image plane 704 in the area 746. The over-aperture rays, instead, reach the image plane 704 in an area 750. The over-aperture rays 748 disturb the imaging, in particular by producing a non-uniform field in the image plane 704.

(87) In order to prevent the over-aperture rays 748 from reaching the image plane 704, at least a second aperture stop in addition to the system aperture stop 738 is provided in the projection objective 700 as described in the following.

(88) The second aperture stop is preferably arranged at a position in the projection objective 700, where the over-aperture rays 748 are separated from the ordinary rays which are useful for imaging. Such a position may be for example the space between the optical component 706 and the optical component 707 (see. arrow 752 in FIG. 12A) and/or the location between the optical component 707 and 708 (see arrow 754 in FIG. 12A). In the latter case, because the space between the optical components 707 and 708 is small, the second aperture stop can be formed by a coating 756 on the optical component 707 or 708 which is non-transmissive to the light used for the exposure operation. The coating can be formed by a blacking of the respective portion of the surface of the optical component 707, for example.

(89) At the position shown by arrow 752, the at least one second aperture stop can be formed by a plate having suited shielding properties for shielding or masking out the over-aperture rays 748.

(90) Another position which is very suitable for arranging at least a second aperture stop for masking out the over-aperture rays 748 is in an area 758 of the projection objective 700, where the over-aperture rays 748 are significantly separated from rays 760, which are the rays used for imaging and having the largest height with respect to the optical axis. It can be seen in FIG. 12 that the rays 748 are strongly refracted or aberrated when emerging from component 724, far more than the ordinary rays.

(91) For example, a second or further aperture stop 762 can be arranged between the optical component 725 and the optical component 726, and/or between the optical components 726 and 727, etc.

(92) The position of the second or further aperture stop 762 is preferably chosen such that the distance L of the aperture stop 762 from the system aperture 738 is such that 0.5D<L<2D, wherein D is the maximum diameter of the optical components in this area.

(93) The at least one second aperture stop, when for example arranged at the position shown by arrow 752 or the aperture stop 762 preferably are fixed aperture stops, and the aperture stop 738 defining the system aperture is adjustable with respect to its effective cross-section.

(94) The projection objective 700 has at least one intermediate image plane between the first pupil plane 738 and the second pupil plane 740. Further, at least one of the optical components 705 to 733 of the projection objective 700 may have an aspherical optically operative surface. In particular in projection objectives having components with aspherically operative surfaces, over-aperture rays like over-aperture rays 748 are aberrated to a higher degree as in projection objectives without aspherical components. Thus, the provision of at least a second aperture stop in such a projection objective having aspherical components is in particular advantageous.

(95) It is to be understood that at least a second aperture stop as described with reference to FIG. 12 can also be provided in any of the projection objectives shown in FIGS. 1 to 11, if appropriate. Vice versa, the shields for shielding false light which have been described with respect to FIGS. 1 to 11, can be provided within projection objective 700, too.