Optical rod for mixing illumination light in an illumination optical unit of a lithographic projection exposure system

Abstract

An optical rod (19) is used to mix illumination light in an illumination optical unit of a lithographic projection exposure system. A cylindrical rod main part (19a) is divided into at least two cylindrical main part portions (39, 40). Between the two main part portions is at least one partial reflection layer (41) for the illumination light, said partial reflection layer being positioned between an inlet surface (18) and an outlet surface (20) of the rod main part (19a). End-face cross-sections of the main part portions (39, 40) complement each other in order to form the rod cross-section of the rod main part (19a). The result is an optical rod with an improved light mixing function.

Description

[0001] Optical rod for mixing illumination light in an illumination optics of a lithographic projection exposure system

[0002] This patent application claims priority from German patent application DE 10 2023 210 772.4, the contents of which are incorporated herein by reference.

[0003] The invention relates to an optical rod for mixing illumination light in an illumination optics system of a lithographic projection exposure system. Furthermore, the invention relates to an illumination optics system comprising such an optical rod, an optical system comprising such an illumination optics system, and a projection exposure system comprising such an optical system. Further embodiments of optical rods for light mixing are known from JP HI 1-162337 A and DE 102 51 087 AL.

[0004] An illumination optics of a lithographic projection exposure system with an optical rod for mixing illumination light is known from WO 2019 / 145 126 A1 and EP 1 959 302 BL An optical rod for light mixing is known from DE 100 65 198 A1

[0005] It is an object of the present invention to provide an optical rod with improved light mixing.

[0006] This object is achieved according to the invention by an optical rod having the features specified in claim 1. According to the invention, it was recognized that an internal reflective layer in the rod base body, which extends between the entrance surface and the exit surface, makes it possible to enhance the light mixing effect of the optical rod compared to pure reflection at sections of the cylindrical jacket wall of the rod base body. A correspondingly improved light mixing result is the result. The reflective layer can be formed by an internal boundary layer between an optically thicker and an optically thinner material, i.e., by a refractive index jump. Alternatively or additionally, the reflective layer can be implemented by a coating, in particular by an interference coating.Partial reflection occurs at the reflective layer, so that part of the illumination light is transmitted through the reflective layer and another part is reflected by the reflective layer. The rod base body of the optical rod can be cuboid-shaped overall. The entrance and exit surfaces of the optical rod can have square or rectangular edges.

[0007] A cross-section of the exit surface can in particular be adapted to a shape and / or an aspect ratio of the object field.

[0008] A reflective layer according to claim 2 leads to a particularly good mixing result. A reflection of the partial reflective layer can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or even 90%. The reflection of the reflective layer can be in the range of 50%. A ratio between the intensities of the portion of the illuminating light transmitted through the reflective layer on the one hand and the portion of the illuminating light reflected by the reflective layer on the other hand can be adapted to requirements placed on homogenization of an illuminating intensity during light mixing of the illuminating light and / or on an illuminating angle distribution of the illuminating light during light mixing.For example, the larger the reflection component of the reflective layer, the greater the average number of internal reflections of the illuminating light as it passes through the optical rod between the entrance and exit surfaces. The closer the reflection of the partial reflective layer is to 50%, the greater the pupil mixing of the illuminating light as it passes through the optical rod. In the limiting case, a low reflection of the reflective layer leads to an effect of the optical rod with only small additional mixing components due to internal reflection.

[0009] At least two reflective layers according to claim 3 lead to a further improved mixing result of the optical rod. The reflective layers can have identical reflective properties. Alternatively, the reflective properties of two reflective layers can differ. The optical rod can have exactly two reflective layers. If the optical rod has more than two reflective layers, some of the reflective layers or all of the reflective layers can have identical reflective properties. Alternatively, all of the reflective layers can differ in their reflective properties. The number of reflective layers can range between 1 and 10 and can even be greater.

[0010] A profile of the at least one reflective layer according to claim 4 facilitates the manufacture of the optical rod. A profile of the at least one reflective layer according to claim 5 leads to a particularly good mixing result. The smallest angle at which the reflective layer extends to one of the lateral wall surfaces of the cylinder lateral wall can be in the range between 30° and 60°, and can in particular be in the range of 45°.

[0011] At least two parallel reflection layers according to claim 6 also lead to a particularly good mixing result. All reflection layers of the optical rod can run parallel to each other. The parallel reflection layers can run equidistant from each other. In this case, it is possible to manufacture the optical rod from several stacked substrate layers of the same raw substrate layer material.

[0012] Reflective layers extending at a finite angle to each other according to claim 7 also lead to a particularly good mixing result. The angle between the two reflective layers can be greater than 45°, greater than 60°, and greater than 80°. The angle between the at least two reflective layers can be 90°.

[0013] Intersecting reflection layers according to claim 8 also lead to a particularly good mixing result. A crossing point between the reflection layers can be arranged decentered in the rod cross-section of the rod base body relative to a cross-section of the entrance surface and the exit surface. Alternatively, the crossing point can also be arranged centrally in the cross-section of the entrance surface and the exit surface. The advantages of an illumination optical system according to claim 9, an optical system according to claims 10 or 11, and a projection exposure system according to claim 12 correspond to those already explained above with reference to the optical rod.

[0014] The lighting system may include a DUV (deep ultraviolet) light source.

[0015] The projection exposure system can be used to produce a micro- or nano-structured component, particularly a semiconductor chip, for example a memory chip.

[0016] Embodiments of the invention are explained in more detail below with reference to the drawings, in which:

[0017] Fig. 1 is a schematic overview of a microlithography projection exposure system in a meridional section, comprising an illumination optics with an optical rod for mixing illumination light;

[0018] Fig. 2 a pupil of the illumination optics according to the optical

[0019] Rod to illustrate its mixing effect;

[0020] Fig. 3 is a front view of an embodiment of the optical

[0021] Rod with a view towards an end-side entrance surface of the optical rod, comprising a continuous reflection layer for the illumination light between the entrance surface and the exit surface; Fig. 4 schematically shows in a rod longitudinal section an optical

[0022] Mixing effect of the reflective layer;

[0023] Fig. 5 to 15 show, in a representation similar to Fig. 3, further embodiments of the optical rod with different reflective layer embodiment variants extending between the entrance surface and the exit surface of the optical rod;

[0024] Fig. 16 shows a cross-section through a raw stack of optical plane plates as a preliminary stage of the production of a further embodiment of the optical rod with a total of five continuous, mutually parallel reflection layers; and

[0025] Fig. 17 is a perspective view of another embodiment of an optical rod with two intersecting, continuous reflection layers running parallel to the cylinder walls of the rod.

[0026] To clarify spatial relationships, a Cartesian xyz coordinate system is shown in the drawing. In Fig. 1, the x-axis runs perpendicular to the drawing plane and extends out of it. The y-axis runs upward in Fig. 1. The z-axis runs to the left in Fig. 1.

[0027] A microlithography projection exposure system 1 has an illumination system with illumination optics 2 for illuminating a defined illumination or object field 3 at the location of an object or reticle 4, which represents a template to be projected for the production of microstructured or microelectronic semiconductor components. The reticle 4 is held by a reticle holder (not shown).

[0028] A deep ultraviolet (DUV) laser serves as the light source 5 for the illumination system. This can be an ArF excimer laser. Other DUV sources are also possible, e.g., the i-line (365 nm) of the emission spectrum of a mercury vapor lamp.

[0029] A beam expander 6, for example a mirror arrangement known from DE-A 41 24 311, serves to reduce coherence and to generate an expanded, collimated, rectangular cross-section of a beam of the illuminating light 7.

[0030] A first diffractive optical raster element (DOE) 8 is arranged in an object plane of a condenser 9. This DOE 8 is also referred to below as an intensity pre-fork element. The condenser 9 has an axicon pair 10 and a lens 11 with a positive focal length. The distance between the axicon elements of the axicon pair 10 and the position of the lens 11 are adjustable along an optical axis 12 of the illumination optics 2, as indicated in Fig. 1 by double arrows 13, 14. The condenser 9 therefore represents a zoom optics.

[0031] A further diffractive and / or refractive optical raster element (ROE) 16 is arranged in an exit pupil plane 15 of the condenser 9. If the raster element 16 is designed to be diffractive, it can be implemented, for example, as a computer-generated hologram (CGH). Alternatively or in addition to being designed as a diffractive optical element, the ROE 16 can be designed to be refractive, for example, as a refractive optical raster element, in particular as a microlens array. Although a diffractive design is also possible, the raster element 16 will be referred to below as an ROE.

[0032] The first DOE 8 sets a defined intensity distribution in the pupil plane 15 at the location of the ROE 16. This creates a predefined illumination setting, i.e., a defined distribution of illumination angles across the object field 3. The first DOE 8 therefore represents an illumination angle specification element for specifying an illumination angle distribution across the object field 3.

[0033] A coupling optics 17 arranged downstream of the ROE 16 transmits the illumination light to an entrance surface 18 of a transparent optical rod 19. Variants of the optical rod 19 and variants of the holding devices for the optical rod 19 are described below. The optical rod 19 can be manufactured as a glass rod. The optical rod 19 has a transmission of better than 99.5%.

[0034] The optical rod 19 has a cylindrical rod base body 19a. The optical rod 19 has a rectangular or square cross-section. Depending on the design, the rod cross-section can also be polygonal or hexagonal.

[0035] The ROE 16, among other things, adapts the cross-sectional shape of the illumination beam 7 to the rectangular shape of the entrance surface 18 of the rod 19. The ROE 16 is also referred to below as the optical rod illumination specification element. The ROE 16 serves to specify the illumination of the entrance surface 18 of the rod 19 with the illumination light 7. This specification of the illumination of the entrance surface 18 is such that it specifies a distribution of the illumination intensity and, at the same time, the illumination angle distribution across the entrance surface 18. The specified illumination intensity distribution across the entrance surface 18 deviates from a homogeneous distribution, which will be explained in more detail below.

[0036] The DOE 8, i.e. the intensity specification element, is used to specify an illumination intensity distribution on the ROE 16, i.e. on the optical rod illumination specification element.

[0037] The rod 19 mixes and homogenizes the illumination light by multiple internal reflections at the jacket walls of the rod 19. Immediately adjacent to an end-side exit surface 20 of the rod 19 opposite the entrance surface 18 there is an intermediate field plane in which a reticle masking system (REMA) 21, an adjustable field diaphragm, is arranged.

[0038] A condenser 22 is arranged downstream of the REMA 21. A diaphragm changing holder 24 with a plurality of diaphragms or filters can be arranged in an exit pupil plane 23 of the condenser 22, two of which, 25, 26, are shown in Fig. 1. The diaphragm changing holder 24 carries the various diaphragms in the manner of a diaphragm carousel. For diaphragm changing, the carousel is driven by a drive shaft 27 of a drive motor 28, which is in signal communication with a central control device 28a of the projection exposure system 1. The diaphragms of the diaphragm changing holder 24 are divided into an even number of separate diaphragm sections. The diaphragm sections can be diaphragms that completely block the illuminating light, gray filters that attenuate the illuminating light by a predetermined amount, or polarization filters that linearly polarize the illuminating light.

[0039] The pupil plane 23 downstream of the rod 19 is followed by another condenser with lens groups 29, 30. A 90° deflection mirror 31 for the illumination light is arranged between the two lens groups 29, 30. The condenser 22 and the further condenser with the two lens groups 29, 30 form an objective 31a, which images the intermediate field plane of the REMA 21 onto the reticle 4. The pupil plane 23 represents an internal pupil plane of this objective 31a.

[0040] A projection lens 32 images the object field 3, which lies in an object plane 33, into an image field 34 in an image plane 35. The image field 34 is part of the surface of a wafer 36 to be exposed, which is provided with a coating sensitive to the illumination light. The wafer 36 is held by a wafer holder (not shown). During projection exposure, the reticle 4 and the wafer 36 are scanned synchronously with each other. Intermittent displacement of the holders of the reticle 4 and the wafer 36, a so-called stepper operation, is also possible.

[0041] The various bundle-guiding and bundle-forming components of the projection exposure system 1, with the exception of the deflecting mirror 31, are indicated as refractive components. They can also be catadioptric or reflective components. Fig. 2 illustrates a cross-section through an exit pupil 37 of the illumination optics 2 in the exit pupil plane 23. Schematically, the exit pupil 37 in Fig. 2 is divided into four pupil quadrants, namely horizontal pupil quadrants QH1 (right) and QH2 (left) and two vertical pupil quadrants QV1 (top) and QV2 (bottom). The embodiments explained below for the optical rod 19 lead to a mixing of an intensity of the illumination light 7 in all four pupil quadrants QH1, QH2, QV1 and QV2, that is to say also to a mixing between the horizontal pupil quadrants QH1, QH2 on the one hand and the vertical pupil quadrants QV1, QV2 on the other hand.The goal is to achieve the same integral illumination light intensity in all four pupil quadrants within specified tolerances. In this case, an HV ellipticity has EHV.

[0042] EHV = (QH1 + QH2) / (QV1 + QV2) the value 1.

[0043] Fig. 3 shows an embodiment of the optical rod 19 in an end view along a beam path of the illumination light 7. The entrance surface 18 is therefore facing the observer.

[0044] A cylinder jacket wall 38 of the optical rod 19 has a rectangular cross-section which corresponds to the edge of the entrance surface 18 and the opposite exit surface of the optical rod 19.

[0045] The rod base body 19a is divided into two cylindrical base body sections 39, 40 with a congruent trapezoidal cross-section. The trapezoidal end cross-sections of the two base body sections 39, 40 complement each other to form the overall rectangular rod cross-section of the rod base body 19a.

[0046] Between the two base body sections 39, 40, a reflection layer 41 for the illumination light 7 is arranged, which is continuous between the entrance surface 18 and the exit surface 20.

[0047] The reflection layer 41 is designed as a partial reflection layer with a reflection for the illumination light 7 in the range of 50%.

[0048] The reflection layer 41 forms a minimum angle of 45° with the wall sections of the cylinder jacket wall 38.

[0049] Fig. 4 illustrates a mixing effect of the reflective layer 41 in a longitudinal section of the optical rod perpendicular to the reflective layer 41. Illumination light 7 coupled into the entrance surface 18 is split at the reflective layer 41 into a reflected light component 7R and a transmitted light component 7T. After reflection of these light components 7R, 7T at the respective wall sections of the cylinder jacket wall 38, a further split of these components 7R, 7T takes place at the reflective layer 41. In total, this split takes place four times in the mixing example according to Fig. 4, so that the incident beam of illuminating light 7 becomes a total of five outgoing beams of illuminating light 7. This improves the mixing effect of the optical rod.

[0050] Due to the 45 “angle between the reflection layer 41 and the

[0051] Wall sections of the cylinder shell wall 38 also result in a mixed distribution of the illumination light 7 over all H and V quadrants of the exit pupil 37 as shown in Fig. 2. The result is an HV ellipticity EHV close to 1.

[0052] Fig. 5 shows a further embodiment of an optical rod 42, which can be used instead of the optical rod 19 in the illumination optics 2. Components and functions corresponding to those already explained above with reference to Figs. 1 to 4 have the same reference numerals in Fig. 5 and will not be discussed in detail again.

[0053] The optical rod 42 has a total of four cylindrical base body sections 43, 44, 45, and 46, between which two reflective layers 47, 48 intersect at a cross-sectional center of the rod base body 19a in an intersection region K. In the plan view according to Fig. 6, the intersection region K is shown as an intersection point. The intersection region K runs continuously between the entrance surface 18 and the exit surface 20 of the optical rod 42.

[0054] The two main body sections 43, 44 each have a pentagonal cross-section and are congruent to each other. The two other main body sections 45, 46 each have a triangular cross-section and are congruent to each other.

[0055] Due to the two intersecting reflection layers 47, 48, an additional mixing effect of the optical rod 42 results, particularly distributing between the pupil quadrants QH1, QH2, QV1 and QV2. The two reflection layers 47, 48 in turn run at a smallest angle between the edge sections of the cylinder jacket wall 38 of 45°.

[0056] Fig. 6 shows a further embodiment of an optical rod 49, which can be used instead of the optical rod 19 in the illumination optics 2. Components and functions corresponding to those already explained above with reference to Figs. 1 to 5 have the same reference numerals in Fig. 6 and will not be discussed again in detail.

[0057] In the optical rod 49, an intersection point K between the two intersecting reflection layers 47, 48 is not located centrally in the cross-section of the rod base body 19a, but rather offset toward one of the longitudinal sides of the cross-section of the rod base body 19a. The intersection point K is thus decentered relative to both the entrance surface 18 and the exit surface 20.

[0058] In the optical rod 49, the two base body sections 43, 44 are mirror-symmetrical to a center plane of the rod base body 19a, which passes through the intersection point K.

[0059] Compared to the optical rod 42, the ellipticity EHV of the optical rod 49 is even closer to the value 1.

[0060] Fig. 7 shows a further embodiment of an optical rod 50, which can be used instead of the optical rod 19 in the illumination optics 2. Components and functions which correspond to those already explained with reference to Figs. 1 to 6, and in particular with reference to Figs. 5 and 6, bear the following symbol in Fig.

[0061] 7 have the same reference numbers and will not be discussed in detail again.

[0062] The optical rod 50 comprises three cylindrical base body sections 51, 52, 53, each of which has approximately triangular cross-sections and in turn complements the rod cross-section of the rod base body 19a. A reflective layer 54 is located between the base body sections 51 and 53, and a reflective layer 55 is located between the base body sections 53 and 52. The two reflective layers 54 and 55 again form a minimum angle of 45° to wall sections of the cylinder jacket wall 38. The two reflective layers 54, 55 form an angle of 90° to each other. In the view according to Fig. 7, these two reflective layers 54, 55 form a V-shape.

[0063] The optical rod 50 has a particularly good mixing effect with respect to the ellipticity EHV, so that the associated parameter lies in the range between 0.98 and 1.02.

[0064] Fig. 8 shows a further embodiment of an optical rod 56 which can be used in place of the optical rod 19 in the illumination optics 2. Components and functions which correspond to those already explained above with reference to Figs. 1 to 7, and in particular with reference to Figs. 5 to 7, have the same reference numerals in Fig. 8 and will not be discussed in detail again. In contrast to the arrangement of the reflective layers 54, 55 in the optical rod 50, the reflective layers 54, 55 in the optical rod 56 have a somewhat greater minimum distance, so that the two legs of the "V" do not meet in a corner, but are somewhat further apart in the optical rod 56 compared to the optical rod 50.

[0065] Fig. 9 shows a further embodiment of an optical rod 57, which can be used instead of the optical rod 19 in the illumination optics 2. Components and functions corresponding to those already explained above with reference to Figs. 1 to 8, and in particular with reference to Figs. 5 to 8, have the same reference numerals in Fig. 9 and will not be discussed again in detail.

[0066] The optical rod 57 has two parallel reflective layers 58, 59, which in turn form a minimum angle of 45° with the wall sections of the cylinder jacket wall 38. Accordingly, the rod base body 19a of the optical rod 57 is divided into three base body sections 60, 61, 62. The two base body sections 60, 62 are trapezoidal in cross-section and congruent to one another, similar to the base body sections 39, 40 of the optical rod 19 shown in Fig. 3. The base body section 61 located between the two reflective layers 58, 59 has a parallelogram-shaped cross-section.

[0067] Fig. 10 shows a further embodiment of an optical rod 63, which can be used instead of the optical rod 19 in the illumination optics 2. Components and functions corresponding to those already explained above with reference to Figs. 1 to 9, and in particular with reference to Figs. 5 to 9, have the same reference numerals in Fig. 10 and will not be discussed again in detail.

[0068] Compared to optical rod 57, the two parallel reflection layers 58 and 59 of optical rod 63 are spaced further apart. This distance is greater than the thickness of the cylindrical base body sections 60, 62 of optical rod 63, so that the three base body sections 60, 61, and 62 can essentially be manufactured from the same raw optical plate material.

[0069] Fig. 11 shows a further embodiment of an optical rod 64, which can be used instead of the optical rod 19 in the illumination optics 2. Components and functions corresponding to those already explained above with reference to Figs. 1 to 10, and in particular with reference to Figs. 5 to 10, have the same reference numerals in Fig. 11 and will not be discussed again in detail.

[0070] In the optical rod 64, the distance between the parallel reflection layers 58 and 59 is again somewhat larger than in the optical rod 63. In the optical rod 64, the three base body sections 60, 61, 62 can also be manufactured from the same optical raw plate material.

[0071] Fig. 12 shows a further embodiment of an optical rod 65, which can be used instead of the optical rod 19 in the illumination optics 2. Components and functions corresponding to those already explained above with reference to Figs. 1 to 11, and in particular with reference to Figs. 5 to 11, have the same reference numerals in Fig. 12 and will not be discussed again in detail.

[0072] The optical rod 65 has a total of three mutually parallel reflection layers 66, 67, and 68, which are arranged equidistant from one another. Accordingly, the optical rod 65 has two outer cylindrical base body sections 69, 70, which, like the base body sections 39, 40, are trapezoidal and congruent in cross-section, and, between the reflection layers 66, 67 on the one hand and the reflection layers 67, 68 on the other hand, two further base body sections 71, 72, each of which has a parallelogram-shaped cross-section, like the base body section 61.

[0073] Fig. 13 shows a further embodiment of an optical rod 73, which can be used instead of the optical rod 19 in the illumination optics 2. Components and functions corresponding to those already explained above with reference to Figs. 1 to 12, and in particular with reference to Figs. 5 to 12, have the same reference numerals in Fig. 13 and will not be discussed again in detail.

[0074] The optical rod 73 in turn has three parallel reflection layers 66, 67, 68, the distance between which is greater than the distance between adjacent reflection layers 66 to 68 of the optical rod 65 according to Fig. 12.

[0075] Fig. 14 shows a further embodiment of an optical rod 74, which can be used instead of the optical rod 19 in the illumination optics 2. Components and functions corresponding to those already explained above with reference to Figs. 1 to 13, and in particular with reference to Figs. 5 to 13, have the same reference numerals in Fig. 14 and will not be discussed again in detail.

[0076] The optical rod 74 has a total of four parallel reflective layers 75, 76, 77, and 78. Accordingly, the optical rod 74 has a total of five base body sections 79, 80, 81, 82, and 83. The two outer cylindrical base body sections 79, 80 are trapezoidal and congruent to one another, similar to the base body sections 39, 40, and can also have a triangular cross-section, depending on the design of the optical rod 74. The additional base body sections 81, 82, and 83 located between each two adjacent reflective layers 75 to 78 have a parallelogram-shaped cross-section. The middle base body section 82 is somewhat thicker than the two adjacent base body sections 81 and 83. Alternatively, all three base body sections 81, 82, and 83 can be equally thick.

[0077] Fig. 15 shows a further embodiment of an optical rod 84, which can be used instead of the optical rod 19 in the illumination optics 2. Components and functions corresponding to those already explained above with reference to Figs. 1 to 14, and in particular with reference to Figs. 5 to 14, have the same reference numerals in Fig. 15 and will not be discussed again in detail.

[0078] In the optical rod 84, a central base body section 92 is made stronger than a central base body 82 in the optical rod 74 according to Fig. 14. The central base body section 92 is almost twice as strong as the two adjacent base body sections 91 and 93.

[0079] A strength ratio between a strength of the central base body section 92 to the strengths of the adjacent base body sections 91 and 93 can, depending on the design of an optical rod corresponding to the optical rods 74 or 84, be in the range between 0.2 and 5.

[0080] Fig. 16 shows in cross section a raw stack 85 of optical plane plates 68i to 68r> as a preliminary stage for the production of a further embodiment of an optical rod 87 with a total of five reflection layers 88, 89, 90, 91 and 92. Two of these optical rods 87i and 872 are shown.

[0081] To produce the two optical rods 87i and 872, the stacked optical plane plates 86i are cut and polished according to the cross-section of the optical rods 87i and 872 shown in Fig. 16. In a preparatory or alternatively in a subsequent step, the reflective layers are applied between the optical plane plates 86i to 86i that are adjacent to one another within the cross-sections of the optical rods 87i and 872.

[0082] The resulting optical rods 87i, 872 then contain a total of six cylindrical base body sections, each of which forms sections of the optical plane plates 86i to 86<.

[0083] With a corresponding method, using three corresponding optical plane plates, for example, the optical rod 63 according to Fig. 10 or the optical rod 64 according to Fig. 11 can be manufactured. With reference to Fig. 17, a further embodiment of an optical rod 93 is described below, which can be used in the illumination optics 2 instead of one of the variants described above. Components and functions that correspond to those already explained above with reference to Figs. 1 to 16 have the same reference numerals and will not be discussed again in detail.

[0084] In the optical rod 93, the rod base body 19a is divided into a total of four rectangular base body sections 94, 95, 96, and 97. Between these sections are two reflective layers 98, 99, which form an angle of 90° to each other. The reflective layers 98, 99 each run parallel to a surface of the cylindrical wall 38 of the rod base body 19a.

[0085] An intersection point or intersection area K of the two reflective layers 98, 99 is spaced both horizontally and vertically from a cross-sectional center of the entrance surface 18 and the exit surface 20. An arrangement of the intersection point K of the two reflective layers 98 and 99 that is centered horizontally or vertically with respect to one dimension, or centered with respect to both dimensions, is also possible.

[0086] In an alternative embodiment of the illumination optics 2, in addition to an optical rod according to one of the embodiments explained above, a further optical rod is provided sequentially upstream or downstream in the beam path of the illumination light 7, without subdividing the rod base body into cylindrical base body sections. The further optical rod can be designed as known, for example, from the prior art cited in the introduction. The further optical rod can have high-precision polished end surfaces, i.e., a high-precision polished entrance surface 18 and a high-precision polished exit surface 20. By combining a rod according to the embodiments explained above with reference to Fig. 2 ff. with an optical rod known from the prior art, an illumination mixing result can be further optimized.

[0087] During the microlithographic production of a micro- or nanostructured component, the wafer 36 is first coated, at least in sections, with a light-sensitive layer. Then, a structure on the reticle 4 is projected onto the wafer 36 using the projection exposure system 1. One of the variants of the optical rod described above is used for this purpose. The exposed wafer 36 is then processed to form the microstructured component.

Claims

Patent claims 1. Optical rod (19; 42; 49; 50; 56; 57; 63; 64; 65; 73; 74; 84; 87; 93) for mixing illumination light (7) in an illumination optics (2) of a lithographic projection exposure apparatus (1), having a cylindrical rod base body (19a), — with an end-face entrance surface (18) for the entrance of the illumination light (7), — with an opposite, end-face exit surface (20) for the exit of the illuminating light (7), and — with a cylindrical jacket wall (38) with a rod cross-section corresponding to the edge of the entry surface (18) and the exit surface (20), wherein the rod base body (19a) is divided into at least two cylindrical base body sections (39, 40; 43 to 46; 51 to 53; 60 to 62; 69 to 72; 79 to 83; 94 to 97), between which at least one reflective layer (41; 47, 48; 54, 55; 58, 59; 66 to 68; 75 to 78; 88 to 92; 98, 99) for the illuminating light (7) is arranged, wherein on the reflective layer (41; 47, 48; 54, 55; 58, 59; 66 to 68; 75 to 78; 88 to 92; 98, 99) a partial reflection of the illumination light (7) takes place, so that a part of the illumination light (7) is passed through the reflection layer (41; 47, 48; 54, 55; 58, 59; 66 to 68; 75 to 78; 88 to 92; 98, 99) and another part of the illumination light (7) is reflected at the reflection layer (41; 47, 48; 54, 55; 58, 59;66 to 68; 75 to 78; 88 to 92; 98, 99) is reflected; wherein end cross sections of the base body sections (39, 40; 43 to 46; 51 to 53; 60 to 62; 69 to 72; 79 to 83; 94 to 97) complement each other to form the rod cross section of the rod base body (19a).

2. Optical rod according to claim 1, characterized in that the at least one reflection layer (41; 47, 48; 54, 55; 58, 59; 66 to 68; 75 to 78; 88 to 92; 98, 99) is designed as a partial reflection layer with a reflection in the range between 10% and 90%.

3. Optical rod according to claim 1 or 2, characterized by more than two cylindrical base body sections (43 to 46; 51 to 53; 60 to 62; 69 to 72; 79 to 83; 94 to 97), between which at least two reflective layers (47, 48; 54, 55; 58, 59; 66 to 68; 75 to 78; 88 to 92; 98, 99) for the illumination light (7) are arranged, wherein end-side cross sections of the base body sections (43 to 46; 51 to 53; 60 to 62; 69 to 72; 79 to 83; 94 to 97) extend to the rod cross section of the rod base body (19a).

4. Optical rod according to one of claims 1 to 3, characterized in that the at least one reflection layer (98, 99) runs parallel to a jacket wall surface of the cylinder jacket wall (38).

5. Optical rod according to one of claims 1 to 3, characterized in that the reflection layer (41; 47, 48; 54, 55; 58, 59; 66 to 68; 75 to 78; 88 to 92) extends at an angle of between 10° and 90° to a surface of the cylinder wall (38).

6. Optical rod according to one of claims 1 to 5, characterized in that at least two reflection layers (58, 59; 66 to 68; 75 to 78; 88 to 92) run parallel to each other.

7. Optical rod according to one of claims 1 to 5, characterized in that at least two reflection layers (47, 48; 54, 55; 58, 59) extend at a smallest angle in the range of 10 ° to 90 ° to each other.

8. Optical rod according to claim 7, characterized by at least four cylindrical base body sections (43 to 47; 94 to 97), the end cross sections of which complement the rod cross section of the rod base body (19a) in such a way that between the base body sections (43 to 47; 94 to 97) there are reflection layers (47, 48; 98, 99) crossing in cross section at at least one crossing point (K).

9. Illumination optics with an optical rod according to one of claims 1 to 8 for illuminating an object field (3) in which an object to be imaged can be arranged.

10. Optical system with an illumination optics according to claim 9 and with a projection optics (32) for imaging the object field (3) into an image field (34).

11. Optical system with an illumination optics according to claim 9 and with a light source (5) for the illumination light (7).

12. Projection exposure system with an optical system according to claim 10 and 11, with a reticle holder for holding a reticle (4) as an object to be imaged in an object plane (33), with a projection lens (32) for imaging the object field (3) in an image field (34) in an image plane (35) and with a wafer holder for holding a wafer (36) in the image plane (35).

Images