WO2003067334A2

WO2003067334A2 - Polarisation-optimised illumination system

Info

Publication number: WO2003067334A2
Application number: PCT/EP2003/001146
Authority: WO
Inventors: Karl-Heinz Schuster
Original assignee: Carl Zeiss Smt Ag
Priority date: 2002-02-08
Filing date: 2003-02-05
Publication date: 2003-08-14
Also published as: DE10206061A1; EP1474726A2; AU2003210213A8; WO2003067334A3; AU2003210213A1

Abstract

An illumination system for a projector unit for microlithography working with ultra-violet light, has an angle-retaining light mixer with at least one integrator rod comprising an inlet surface for receiving light from a light source and an output surface for output of emergent light mixed by means of the integrator rod. At least one prism arrangement for receiving emergent light and for changing the polarisation state of the emergent light is arranged in series after the integrator rod. A preferred prism arrangement has a polarisation distribution surface arranged perpendicular to the propagation direction of the emergent light which permits the unhindered transmission of light components with p polarisation and reflects components with s polarisation. The separated beams with orthogonal polarisation are brought parallel by means of a mirror surface arranged parallel to the polarisation distribution surface and the same polarisation state for both partial beams is achieved by means of a suitable retarder.

Description

Description Polarization-optimized lighting system

The invention relates to an illumination system for an optical device, in particular for a projection exposure system for microlithography, and to a projection exposure system equipped with such an illumination system.

The performance of projection exposure systems for the microlithographic production of semiconductor components and other finely structured components is essentially determined by the imaging properties of the projection optics. In addition, the image quality and the wafer throughput that can be achieved with a system are largely determined by the properties of the lighting system upstream of the projection lens. This must be able to prepare the light of a light source with the highest possible efficiency and to set a light distribution that can be precisely defined with regard to the position and shape of illuminated areas and with the most uniform possible intensity distribution within the illuminated areas is present. These requirements should be met equally in all adjustable lighting modes, for example in conventional settings with different degrees of coherence or in ring field, dipole or quadrupole illumination, which are the prerequisites for imaging the reticle patterns with high interference contrast.

An increasingly important requirement for lighting systems is that they should be able to provide output light with a polarization state that can be defined as precisely as possible. For example, it may be desirable for the light falling on the photomask or in the subsequent projection objective to be largely or completely linearly polarized and to have a defined orientation of the preferred polarization direction. With linearly polarized input light e.g. modern catadioptric projection lenses with polarization beam splitter (beam splitter cube, BSC) work with a theoretical efficiency of 100% on the beam splitter. It may also be desirable to provide illuminating light that is largely unpolarized or very well circularly polarized in the area of the photomask. In this way, for example, structure-dependent resolution differences (H-V differences, CD variations) can be avoided, which can occur when illuminated with linearly polarized light and the typical structure widths of the patterns to be imaged are in the order of magnitude of the wavelength used.

A further requirement, in particular in modern microlithographic projection exposure systems, is that a light distribution provided in the area of a pupil plane of the illumination system should be transferred into a pupil plane of the projection objective conjugated to the pupil plane of the illumination system while maintaining the distribution of the light energy in the angular space. Any change in the angular spectrum introduced in the light path between the conjugate pupil planes leads to a distortion of the intensity distribution present in the objective pupil, which, for example in the case of dipole or quadrupole illumination, can lead to asymmetrical irradiation in the imaging two-beam interference and thus to a deterioration in the imaging performance.

A high degree of uniformity or homogeneity of the illumination falling on the photomask (reticle) can be achieved by mixing the light coming from a light source with the aid of a light mixing device. In light mixing devices, a distinction is essentially made between light mixing devices with honeycomb condensers and light mixing devices with integrator bars or light mixing bars. These systems have specific advantages and disadvantages. Honeycomb condensers with grid arrangements of lenses (fly's eye lens) for generating a large number of secondary light sources have the advantage that the polarization state of the light passing through is practically unchanged. This is offset by the disadvantage of poorer light transmission efficiency compared to integrator bars, since the passage area in the area of interfaces between the individual lenses has non-transmitting dead areas. A honeycomb condenser also changes the angular spectrum of the light passing through due to aberrations introduced by lenses.

Lighting systems which have light mixing devices with honeycomb capacitors are disclosed, for example, in US Pat. Nos. 6,211, 944 B1 and 6,252,647 B1. A lighting system designed for the range of visible light for a projection apparatus for projecting the content of LCD displays is shown in US Pat. No. 6,257,726 B1.

In contrast, systems with integrator bars are characterized by a superior transmission efficiency. Preferred here Considered lighting systems designed for ultraviolet light, an integrator rod consists of a material which is transparent to the light from the light source and is irradiated with light of a given aperture essentially along its longitudinal direction. In the integrator rod, the light passing through is often totally reflected at the lateral interfaces, as in a kaleidoscope, whereby an almost perfect mixture of non-homogeneous portions of the light can be achieved. The effectiveness of the mixture depends on the number of reflections in the individual directions over the rod length. In the case of the integrator rods considered here with parallel, flat lateral boundary surfaces, the angular distribution of the incoming light is practically completely retained. A disadvantage of integrator bars is their poorly controllable influence on the polarization state of the light passing through. Firstly, an optical path of great length is in use. Due to intrinsic or induced birefringence, delay effects of different magnitudes of the components of the electric field vector vibrating in different directions can occur on this. On the other hand, there are many skewed (total) reflections on the sides, which change the polarization state of the transmitted light in an uncontrollable manner due to their phase-shifting effect.

Illumination systems for the UV range with rod-shaped light integrators are disclosed, for example, in German patent applications DE 44 21 053, DE 195 20 363, DE 199 12 464 or in US Pat. No. 6,028,660. Rod integrators can also be designed as kaleidoscopic waveguides with mirror surfaces facing inwards

The object of the invention is to create an illumination system which is particularly suitable for use in a microlithographic projection exposure system and which transmits the light from an associated light source with high efficiency, a has negligible influence on the angular distribution of the passing light and allows a defined setting of the polarization state of the emerging light.

This object is achieved by a lighting system with the features of claim 1. Advantageous further developments are specified in the dependent claims. The wording of all claims is incorporated by reference into the content of the description.

The invention provides an illumination system for an optical device, in particular for a projection exposure system for microlithography, which has a light mixing device. The light mixing device has: at least one integrator rod, which has an entry surface for receiving light from a light source and an exit surface for emitting exit light mixed by the integrator rod, and at least one prism arrangement for receiving exit light and for changing the polarization state of the exit light, the prism arrangement at least has a polarization splitter surface oriented transversely to the direction of propagation of the exit light.

The prism arrangement has two or more prisms and causes a change in the polarization state of the incoming light while maintaining the light energy distribution in the angular space. Here, a prism is a body made of transparent material, that is to say transparent to the light used, the interfaces of which include at least two intersecting planes. The prisms preferably have only flat interfaces at which the light running in the prism, possibly several times, is totally reflected before it emerges from the prism. Since there is no refraction on curved surfaces, all beam angles are retained. The polarization splitter surface leaves the proportion of light in which the electric field vector is parallel to the plane of incidence (p-polarized light), unhindered by, while the light component in which the electric field vector swings perpendicular to the plane of incidence (s-polarized light) is reflected on the polarization splitter surface and thereby deflected. The plane of incidence here refers to that plane which is spanned by the direction of incidence of the light and the surface normal of the polarization splitter surface. The transmitted light therefore has p-polarization regardless of the polarization state of the incident light at the exit and thus has a defined polarization state.

The arrangement has a high transmission efficiency without further measures if the light incident on the polarization splitting surface is almost or completely p-polarized.

In order to optimize the overall transmission of the light mixing device regardless of the polarization state of the light impinging on the polarization splitter surface, in a preferred development it is provided that the prism arrangement has at least one mirror surface which is arranged with respect to the polarization splitter surface in such a way that (s- polarized) light can be deflected with the aid of the mirror surface in a direction of propagation which runs essentially parallel to the direction of propagation of the light transmitted by the polarization splitter surface. Since reflectable, s-polarized light hits the mirror surface with a high degree of reflection, deflection with high efficiency is possible. It is also possible to provide a mirror surface which is arranged with respect to the polarization splitter surface in such a way that the light which passes unhindered through the polarization splitter surface is deflected in a direction which is essentially parallel to the direction of propagation of the light reflected by the polarization splitter surface. In both cases, a very high proportion of the light energy radiated on the entrance side is available behind the prism arrangement, the polarization state of the two at least largely parallel beams being defined in each case and accordingly being able to be changed in a targeted manner. The mirror surface is preferably totally reflective and can be formed by an interface of a prism of the prism arrangement. Normally reflecting mirror surfaces are also possible.

Preferred embodiments have an optically active polarization splitter layer on the polarization splitter surface. A polarization splitter layer is an optically effective multilayer system with layers of dielectric material which is transparent for the light wavelength used, the layers lying one above the other alternatingly consisting of high-index and low-index material. The multilayer system is essentially obliquely oriented with respect to the incident light such that angles close to the layer-specific Brewster angle determined by the refractive indices of the materials occur at the interfaces of the layers. As is known, the reflectance for p-polarized light is minimal for this and the corresponding transmittance is maximal.

In particular for applications in the field of visible light, a polarization splitter layer can optionally be dispensed with. The prism arrangement can then be used using birefringence properties of e.g. crystalline prism materials work and include, for example, a Nicol prism, a Rochon prism or the like. The polarization-selective effect can optionally also be achieved by one or more inclined plates.

Prism arrangements, in particular those with a polarization splitter layer, preferably have at least one polarization splitter block with a first and a second prism, which face one another Have interfaces between which the polarization splitter surface, in particular the polarization splitter layer, is arranged. As a result, the polarization is split entirely within transparent materials, which is advantageous for maintaining the angle. In addition, the polarization divider block should have free outer surfaces, that is to say suitable for total reflection, in order to transmit light in a manner that maintains the angle and without loss of light. The light rod is thus continued on all sides in the area of the prism arrangement. The interfaces of the prisms provided for the light exit or light entry are preferably at least partially covered with suitable anti-reflective layers.

In order to set a uniform polarization state for all the light emerging from the light mixing device, suitable delay elements or other measures with a corresponding effect are used. A preferred prism arrangement has at least one first exit surface for the exit of light transmitted through the polarization splitting surface and at least one second exit surface for the exit of light reflected by the polarization dividing surface. At least one of the exit surfaces is followed by a device for changing the polarization state of the light passing through, in particular at least one optical delay element. For example, it is possible to connect one of the exit surfaces with a λ / 2 plate or another element which causes the preferred polarization direction to be rotated by 90 °. As a result, the entire exit light is uniformly p or s polarized. It is also possible to connect a λ / 4 plate or another device to each of the two exit surfaces, which generates circularly polarized light from incoming linearly polarized light. As a result, the entire exit light is circularly polarized, with the same direction of rotation behind the different exit surfaces. Further devices for changing the state of polarization can follow. In preferred prism arrangements, the light exits at two adjacent exit surfaces. There may be a fine dividing line of reduced exit intensity between the exit surfaces. In order to avoid possible effects from the imaging quality, in preferred further developments for wafer scanners the polarization splitter surface is oriented such that an intersection line between it and a plane oriented perpendicular to the direction of exit of the light is transverse, in particular perpendicular to the scanning direction. This means that even exposure is possible even when there is a dividing line.

In the lighting systems considered here, light with a defined aperture is radiated into the integrator rod, which maintains the angle, so that the light strikes the polarization splitter surface lying at an angle to the direction of propagation. For an open bundle of light, the degree of polarization across the aperture will usually vary asymmetrically with respect to rays parallel to the axis. In order to compensate for this effect, the prism arrangement of a preferred development has a first prism group with a first polarization splitter surface and a second prism group with a second polarization splitter surface, the polarization splitter surfaces being arranged mirror-symmetrically to a mirror plane of the integrator rod, which extends in the longitudinal direction of the rod and contains an intersection line between the polarization splitter layers.

Light mixing devices are preferably designed such that the cross-sectional shape of the exit surface is adapted to the shape of the surface to be illuminated. The rod cross section of conventional rod integrators is therefore rectangular with an aspect ratio deviating from one. While in conventional cylindrical rod integrators the exit surface corresponds in shape and size to the entry surface, the invention creates angle-maintaining light mixing devices in which NEN, the exit surface formed by the exit of the prism arrangement has an exit surface cross section that deviates from the entry surface cross section. In particular, the exit area can be larger than the entry area. The exit area cross section can be, for example, an integral multiple, in particular approximately twice the entry area cross section. Since the integrator rod can thus have a smaller cross section than the desired exit surface, a material saving is possible by reducing the cross section of the rod. In addition, the number of reflections in one direction is increased, which improves the homogeneity of the exit light in this direction.

In order to obtain light-mixing devices with high transmission that mix well with moderate demands on the angular loading capacity of the polarization splitter layer, various measures which are advantageous individually or in combination can be taken.

In a preferred development, it is provided that at least one integrator rod of the light mixing device consists of a UV-transparent material, the absorption edge of which lies at lower wavelengths than the absorption edge of calcium fluoride. Magnesium fluoride or lithium fluoride, for example, can be used here as rod material. The use of birefringent material such as magnesium fluoride is unproblematic in the case of embodiments with a downstream device for changing the polarization state, since the change in the polarization state caused by birefringence is cleaned up behind the integrator rod. The use of UV-suitable materials with the lowest possible volume absorption allows rod arrangements with long usable lengths, which generate a sufficient number of reflections even with a low inner aperture. Alternatively or additionally, an integrator rod arrangement, which may be folded several times, can be provided in order to be able to accommodate large overall lengths of the rod arrangement in a limited installation space. This can be achieved in that a plurality of integrator rods are provided and that at least one angle-maintaining deflection device for deflecting the direction of light travel is provided between a first integrator rod and a subsequent second integrator rod. Deflections of 90 or 180 ° are preferred. An almost loss-free, angle-maintaining deflection can be made possible by one or more intermediate deflection prisms. These deflecting prisms preferably have anti-reflective layers on their surfaces serving for the entry or exit of light, the total reflection being retained. The deflection prisms are preferably made of a highly refractive material, the refractive index of which is preferably n> 1, 6, for example BaF ₂ . This means that total reflection can also be used with large numerical apertures.

One measure for increasing the number of reflections in a rod of a given length is to divide the integrator rod into an undivided rod section immediately in front of the exit surface and at least one divided rod section upstream of the undivided rod section, which at least two essentially fill the overall cross section of the integrator rod , totally reflective sticks. Due to the smaller rod cross-sections in the area of the rods, higher reflection numbers and thus better mixing are achieved, the subsequent undivided section causing further homogenization. A graded division over the length of the rod is also possible, for example two or more divided regions with different numbers of rods can be provided. Additional degrees of freedom in optimizing the light mixing device with regard to material and polarization-optical effect are achieved in preferred further developments in that the integrator rod consists of a first material and at least one prism of the prism arrangement and / or at least one deflection prism consists of a second material, which is different from the first Material differs. It should be taken into account here that the prisms arranged in front of and / or behind an integrator rod are relatively small compared to the integrator rod, so that any intrinsic double calculation that may be present is of lesser importance. For example, in a system with a wavelength of 157 nm, the prisms can be made of calcium fluoride, barium fluoride, which is only available at low cost in small volumes, synthetic quartz glass or another suitable, optically isotropic material. The rod material should be selected for low absorption; for example, calcium fluoride, magnesium fluoride or lithium fluoride can be used.

A targeted selection of materials can also be used to optimize the polarization-dividing effect of a polarization splitter block with a polarization splitter layer system. For this purpose, the material of the first and the second prism is to be selected as a function of the refractive index ratios in the polarization splitter layer in such a way that a misalignment between the direction of incidence of the light incident on the polarization splitter layer and a direction corresponding to the Brewster angle of the layer system is optimized, in particular minimized. In this way, a maximum transmittance for p-polarized light can be achieved. Materials with a high refractive index, in particular n> 1, 6, are preferred as prism material, for example BaF _2. This means that total reflection can also be used at high NA.

According to a further development, it is provided that at least a part, preferably all, totally reflecting and non-totally reflecting surfaces surfaces with a reflective effect are coated with a thin coating with a phase-preserving effect. Depending on the type of surface, two types of phase-preserving layer systems are particularly advantageous. On the side surfaces that do not serve as light entry or exit surfaces, the layers are preferably optimized for phase maintenance in reflection and / or total reflection. In the case of those surfaces which serve as light entry or exit surfaces, the layers preferably have a double function. They have a phase-correcting or phase-maintaining effect in reflection, in particular in the case of total reflection, and in transmission as anti-reflective layers. Layers of this type can be provided, in particular, on all of the catheter surfaces of the prisms of the prism arrangement.

In a further development, the light mixing device is assigned at least one diaphragm for setting the local distribution of the energy of an illumination field generated by the light mixing device, the diaphragm preferably having movable diaphragm elements for controlled change in the width of an illumination field as a function of positions along the length of the illumination field. In this way, for example at a longitudinal position in which there is an increased light intensity, the width of the illumination field can be reduced to such an extent that the integrating effect of a scanning movement over the entire length of the illumination field results in essentially the same illumination dose. An example of such an aperture is disclosed in US Pat. No. 6,097,474, the disclosure content of which is made the content of this description by reference.

The lighting system can be constructed in such a way that the light emerging from the light mixing device falls on the structure to be illuminated, for example a photomask, without an intermediate illustration. An advantage here is the significantly reduced NA in the beam part ler of the projection lens and thus in its polarization splitter layer. In preferred developments, a lens is connected downstream, which images the area of the light exit of the light mixing device onto the reticle, which is arranged in the object plane of the subsequent projection lens. This lens has at least one plane, which is a Fourier-transformed plane to the reticle plane and accordingly lies at a conjugate point to the pupil of the subsequent projection lens. In a preferred embodiment, a polarization filter is arranged in the area of the pupil of this objective, which acts as a polarization-selective retroreflector in the manner of a cat's eye (in one section) and has a plurality of polarization splitter surfaces or polarization splitter layers arranged in a V-shape at an angle to one another. In the installation position mentioned, the polarization filter acts as an intermediate polarizer in order to refresh the polarization state of the incoming light or to clean it up such that only p-polarized light is transmitted and s-polarized light is reflected.

Filters of this type are also useful regardless of other features of the invention.

The above and further features emerge from the claims and also from the description and the drawings, the individual features being realized individually or in groups in the form of sub-combinations in one embodiment of the invention and in other fields, and advantageous as well protective designs can represent.

1 is a schematic illustration of a projection exposure system for microlithography with an embodiment of an illumination device according to the invention; Fig. 2 is an axial plan view of the light exit side of a light mixing device of the type shown in Fig. 1;

3 is a schematic section through the outlet-side end region of an embodiment of a light mixing device according to the invention with a preferred variant of a prism arrangement;

4 is a schematic section through the outlet-side end region of another embodiment of a light mixing device;

5 is a schematic section through the outlet-side end region of a further, different embodiment of a light mixing device;

6 schematically shows an embodiment of a light mixing device with four integrator rods and multiple folding of the integrator rod arrangement;

FIG. 7 shows another embodiment of a light mixing device with two integrator rods offset in parallel and 180 ° steel deflection;

Fig. 8 is a perspective view of an integrator rod with two divided and one undivided rod section;

9 is a schematic section through the outlet-side end region of an embodiment of a light mixing device with a mirror-symmetrically constructed prism arrangement; 10 shows schematic representations of the degree of polarization for p-polarization as a function of the beam aperture with a non-symmetrical output (a) and with a symmetrical output (b) of the light mixing device;

11 shows a schematic illustration of a preferred embodiment of a microlithographic projection exposure system; and

12 shows an embodiment of a polarization filter which has a prism arrangement with a plurality of prisms, between which are arranged zigzag-shaped polarization beam splitter layers.

1 shows an example of a projection exposure system 1 for the microlithographic production of integrated circuits and other finely structured components with resolutions down to fractions of 1 μm. The system 1 comprises an illumination system 2 for illuminating a photomask 5 arranged in the image plane 4 of the illumination system and a projection objective 6, which reproduces the pattern of the photomask arranged in its object plane 4 in the image plane 7 of the projection objective on a reducing scale. In the image plane 7 there is, for example, a semiconductor wafer coated with a light-sensitive layer.

A laser 8 is used as the light source of the illumination system 2, for example an excimer laser with a working wavelength of 248 nm, 193 nm or 157 nm, which is customary in the deep ultraviolet range (DUV). The light of the emitted light beam is largely linearly polarized. A subsequent optical device 9 forms the light from the light source and transmits it to a subsequent light mixing device 10. In the example shown, the optical device 9 comprises a laser 8 downstream beam expander, which is used for coherence reduction and beam shaping to a rectangular beam cross section with an aspect ratio x / y of its side lengths of more than one. A first diffractive optical raster element following the beam expander sits in the object plane of a subsequent zoom lens, in the exit pupil of which a second optical raster element is provided. From this, the light enters a coupling optic, which transmits the light into the light mixing device. The light is mixed and homogenized within the light mixing device 10 by multiple internal reflection and exits at the outlet 11 of the light mixing device largely homogenized. Immediately at the outlet of the light mixing device is an intermediate field level, in which a reticle masking system (REMA) 12, an adjustable field diaphragm, is arranged. The subsequent lens 13, which is also referred to as a REMA lens, has a plurality of lens groups, a pupil plane 14 and a deflection mirror 15 and images the intermediate field plane of the reticle masking system onto the reticle or the photomask 5.

Further details on the structure and mode of operation of such a lighting system can be found in DE 195 20 563, the content of which is made the content of this application by reference. An important difference to the lighting system of DE 195 20 563 is the construction of the light mixing device 10, which will be described in detail.

In the case of a wafer stepper, the entire structured surface corresponding to a chip, generally a rectangle with any aspect ratio between height and width of, for example, 1: 1 to 1: 2, is illuminated on the reticle 5 as uniformly and as sharply as possible. In a wafer scanner of the type shown, a narrow strip, for example a rectangle with an aspect ratio of typically 1: 2 to 1: 8, is illuminated on the reticle 5 and by scanning in one the entire structured field of a chip is illuminated serially in the direction corresponding to the y direction of the lighting system. Here, too, the illumination is extremely uniform and at least in the direction perpendicular to the scanning direction, ie in the x direction, to be sharply defined.

In exceptional cases, other forms of the illuminated area on the photomask 5 are also possible. The opening of the reticle masking system 12 and the cross-sectional shape of the light exit 11 of the light mixing device 10 are precisely adapted to the required field shape. The axial plan view shown in FIG. 2 on the exit side 11 of the light mixing device 10 schematically shows that the width in the x direction is a multiple of the total height in the y direction (scanning direction).

The light mixing device 10 comprises an integrator rod 20 and a prism arrangement 30 immediately following with a small air gap. The integrator rod is a rod with a rectangular cross section made of a material which is transparent to the light from the light source 8, for example crystalline calcium fluoride. The longitudinal axis of the rod runs parallel to the z direction or to the optical axis of the lighting system. The rod 20 has a flat entry surface 21 facing the optical device 9 for receiving a shaped light beam from the light source 8, a flat exit surface 22 from which light which is mixed within the integrator rod 20 emerges, and flat side surfaces running in pairs parallel to one another ,

The prism arrangement 30 has an assembly with three prisms 31, 32 and 33, which are shaped and dimensioned identically in preferred embodiments. They are preferably prisms with two mutually perpendicular boundary surfaces of essentially the same size (catheter surfaces) and a larger hypotenuse surface which is oriented at an angle of approximately 45 ° to the catheter surfaces. Two of the prisms, namely the first prism 31 and that second prism 32, enclose a flat polarization splitter layer 34 between their hypotenuse surfaces and form a compact, cuboid-shaped polarization splitter block 35 with an approximately square cross section in the yz plane and catheter surfaces, the cross section of which corresponds to the cross section of the rod exit surface 22. The hypotenuse of the third prism 33, which is also referred to here as a mirror prism, is aligned parallel to the polarization splitting surface 34 and forms a flat, reflecting, preferably totally reflecting mirror surface 36.

The mutually facing catheter surfaces of the polarization splitter block 35 and the third prism 33 are at a small distance 37 from one another, which can be of the order of a few light wavelengths of the light used in order to allow total reflection on the adjacent catheter surfaces. The other free prism surfaces also border on gas or another optically thinner medium in order to allow total reflection. In particular, there is also a small air gap 39 between the exit surface 22 of the integrator rod 20 and the entry surface 38 of the beam splitter block. The prisms 31 to 33 of the prism arrangement can be fixed in a common holder, which in turn can be attached to a holder for the integrator rod 20 to fix the geometry of the arrangement.

1 and 3 are constructed identically with respect to the integrator rod and prism arrangement, which is why the same reference numerals are used for corresponding features.

In the light mixing device 10 in FIG. 1, a delay element 45 designed as a λ / 2 plate, which is a rectangular plate made of birefringent material, the axial thickness and crystal axis of which is dimensioned, is blown onto the exit-side cathode surface 40 of the third prism 32. that is between the perpendicular to each other vibrating components of the electric field vector results in a delay of half a wavelength, which leads to a rotation of an existing polarization preferred direction by 90 ° around the direction of propagation of the light.

The projection exposure system shown here works with largely linearly polarized input light from the laser. In the example, the projection objective 6 is a catadioptical projection objective with a polarization-selective, physical beam splitter (an example will be explained in connection with FIG. 11). Projection lenses of this type work in the area of the beam splitter with the highest degree of efficiency if suitably linearly polarized light is irradiated. This creates the requirement that the lighting system between the laser 8 and the light exit should maintain polarization and / or allow the polarization state of the light occurring to be set in a targeted manner. In addition, there is a requirement to achieve an angle-maintaining light mixture in order to reproduce a spatial intensity distribution generated in the region of a pupil plane of the optical device 9 in the pupil plane 16 of the projection objective that is optically conjugated to this pupil plane.

The light mixing device 10 fulfills this requirement for an angle-maintaining light mixing because of the exclusively flat, reflecting, preferably totally reflecting interfaces on the integrator rod and prism arrangement. In addition, a setting of a defined polarization state at the outlet 11 of the light mixing device is made possible. In the integrator rod 20, due to permanent or induced or intrinsic birefringence of the rod material and a large number of skewed reflections on the side faces, considerable phase shifts between the different field components of the light can occur. As a result, the degree of polarization of the input light is normally difficult to control and partially polarized light emerges at the rod exit 22. This emerges from the exit surface 22 provided with an anti-reflective layer and via the anti-reflective entry surface 38 into the beam splitter block 35, in which the polarization splitter layer 34 is located at an angle of approximately 45 ° to the direction of radiation. This allows all light that vibrates in the plane of incidence (p-polarization, characterized by lines perpendicular to the direction of propagation) to pass through unhindered. All light that vibrates perpendicular to the plane of incidence (s-polarization, characterized by points along the direction of propagation) is reflected at an angle of incidence of approx. 45 ° to the polarization splitter layer and leaves the polarization splitter block essentially perpendicular to the direction of incidence via an anti-reflective catheter surface in the direction of the third prism 33. The reflected light emerging essentially perpendicular to the longitudinal axis of the rod is deflected on the mirror surface 36 of the third prism by approximately 90 ° such that its direction of propagation behind the mirror surface 36 is essentially parallel to the direction of propagation of the light transmitted by the polarization splitter layer 34.

In the embodiment according to FIG. 1, the p-polarized light transmitted through the layer 34 is converted into s-polarized light by the λ / 2 plate 45 without loss, so that both exit beams are s-polarized. S polarization at the input of the REMA lens 13 is advantageous in those embodiments which, like the embodiment according to FIG. 1, have a deflection mirror 15 within the lens which has a higher reflectance for s polarization than for p polarization.

In the embodiment of a light mixing device 25 according to FIG. 3, on the other hand, the preferred polarization direction of the radiation polarized behind the mirror surface is rotated through 90 ° by the retardation plate 46, which is sprayed onto the outlet 41 of the mirror prism 33 is. Both outputs lying one above the other (see FIG. 2) now have identical p-polarization.

In both cases, there are identically polarized parallel exit beams, the total area of which for the light exit side 11 of FIG

Light mixing device have the desired cross section, for example 12 x 22 mm, this cross section is twice as large as the cross section of the rod entry surface 21. At the same time, this creates an angle-maintaining light mixing device with a light exit that can be precisely defined with respect to the polarization state, in which the cross section of the exit face 11 is of the cross section of the Entry surface 21 deviates. In addition to the factor two shown, other area ratios are also possible, in particular integer multiples of the entry area cross section.

With the help of this cross section, it is now possible to scan in the y direction (FIG. 2). Reticle masking can also be operated via a REMA objective 13 that maintains good polarization. By scanning, the fine separation that results due to the air gap 37 between the fields I and II lying one above the other is meaningless for the imaging. For the function, it is also noticeable that a longer distance with light mixing is covered in field II, which leads through the third prism. This is also irrelevant for uniform illumination. Each of the light mixing paths remains optically fully functional, since all exposed prism surfaces on the catheter surfaces are totally reflective. These catheter surfaces are coated with a phase-preserving coating.

The light mixing devices 10 and 25 shown are not only useful in the case of largely linearly polarized input light, but independently of the degree of polarization of the input light at the outlet 11 deliver completely polarized light with s or p polarization. This is from it it can be seen that, regardless of the input polarization (for example unpolarized, circularly polarized, linearly polarized or with rotating linear polarization), p-polarization is transmitted on the beam splitter surface 34 and s-polarization is reflected to the mirror 36. The embodiment according to FIG. 4 is distinguished from the above embodiments in that the exit light of the light mixing device 50 is emitted essentially at right angles to the longitudinal axis of the integrator rod 51. The mirror prism 52 is arranged behind the beam splitter block 53 in the extension of the integrator rod 51 in such a way that light with p-polarization, which passes unhindered through the beam splitter surface 54, is directed downward by 90 °. The s component of the light entering the beam splitter block is deflected downwards at right angles on the splitter surface 54 and converted into light with p-polarization without loss by a downstream λ / 2 plate 55. It is easy to see that the arrangement for emitting s-polarized light can be converted by removing the delay plate 55 from the output of the polarization splitter block 53 and placing it behind the output of the mirror prism 52.

The possibility demonstrated here of arranging the light exit direction either in an extension of the rod or perpendicular to it in an angle-maintaining light mixing device with integrator rod increases the degrees of freedom in the construction of lighting systems equipped with light mixing devices according to the invention.

The embodiment of a light mixing device 60 in FIG. 5 is designed identically to the embodiment according to FIGS. 1 and 2 with regard to integrator rod 20 and prism arrangement 30. In contrast to this, a λ / 4 delay plate 61, 62 is blasted onto the exit surfaces of the steel divider block 35 and the mirror prism 33. As a result, the linearly polarized light emerging from the prism arrangement is included s or p polarization is converted into light with circular polarization, with the same direction of rotation of the two beams.

Circularly polarized light, the properties of which are similar to those of unpolarized light, can be radiated directly onto a reticle, if necessary without the interposition of a REMA lens, and avoids the occurrence of so-called HV differences on the reticle, which can occur when using linear polarized light the typical structure widths on the reticle are in the order of magnitude of the light wavelength used. When using a projection objective with polarization beam splitter, the light would then have to be converted into a linearly polarized light suitable orientation by entering a further λ / 4 plate or the like before entering the beam splitter block. A λ / 4 plate preferably protrudes. the reticle and a λ / 4 plate following the reticle exactly perpendicular to each other. As a result, the incomplete λ / 4 effect with a very large aperture can be completely compensated for by the subsequent λ / 4 plate.

Circularly polarized light can also be used advantageously in conjunction with one-piece REMA lenses without an internal mirror.

The possibly high aperture in the integrator rod places particularly high demands on the angular strength of the polarization splitter layer in the case of prism arrangements with a polarization splitter layer. This should provide its polarization-selective effect over the largest possible angular range around an irradiation direction. In addition, in systems for the shortest working wavelengths, for example 193 nm or 157 nm, there are material problems with the layer materials. While the absorption edge is still sufficiently far away for 193 nm with some suitable layer materials so that the materials do not absorb or only absorb slightly, the selection at 157 nm is reduced. layer materials essentially on magnesium fluoride and representatives as low-refractive layer material and on lanthanum fluoride, barium fluoride and comparable materials as high-refractive layer material. The greatest angular bandwidth can be achieved by the greatest possible refractive index difference between the layer materials. Since only small differences in refractive index can be achieved due to the limited choice of materials, in particular at 157 nm, the only remaining measure for the polarization splitter layer is essentially to increase the number of layer pairs with high refractive index / low refractive index. This brings manufacturing and life-time problems; moreover, the angular load capacity cannot be increased arbitrarily.

These problems can be alleviated by lowering the inner aperture of the integrator rod, which leads to a reduction in the angular load on the polarization splitter layer. A related enlargement of the cross-section of an integrator rod would reduce the number of reflections if the length of the rod remains unchanged, as a result of which the mixing and uniformity of the illumination on the reticle would suffer. Compensating for larger lengths can lead to structural difficulties in the installation environment; furthermore, transmission losses are caused by absorption over a longer distance in the rod material, conventionally calcium fluoride or quartz glass.

In order to obtain sufficient transmission efficiency and thorough mixing with a reduced aperture of the rod, one or more of the measures described below can be used alternatively or cumulatively. One measure consists in changing the rod material from the conventionally used calcium fluoride to magnesium fluoride, which improves the transmission, since magnesium fluoride is at a significantly greater distance from the absorption edge. A double calculation introduced in this way in the rod material is unproblematic, since the prism arrangement downstream of the one anyway Desired polarization state can be restored without loss. Furthermore, a bar arrangement with at least two integrator bars, between which at least one angle-maintaining deflection device is provided, can be provided between the bar inlet and outlet surface of the light mixing device, if necessary while maintaining the conventional overall length. In this way, single or multiple folds of the light path within the light mixing device are possible. With more than two folds, a spatial fold is also conceivable in addition to a flat fold.

The embodiment in FIG. 6 has a light mixing device 70 with four integrator bars 71, 72, 73, 74, between which deflection devices in the form of isosceles 90 ° deflection prisms 75, 76, 77 are provided to deflect the direction of light movement by 90 ° in each case. The light entry and exit surfaces each border on gas. Behind the exit of the last integrator rod 74, a prism arrangement 78 similar to the arrangement according to FIG. 4 is shown, which aligns the exit direction of the two equally polarized beams perpendicular to the longitudinal axis of the last integrator rod 74 and parallel to the direction of incidence at the entrance of the first rod 71. A split REMA lens 79 with a deflecting mirror is located behind the light mixing device, which is designed to emit s-polarized light. The axial installation space (distance between the entry surface of the first integrator rod 71 and light exit at the prism arrangement) is only about half as large as the total light path in this embodiment, which essentially results from the total length of the integrator rods and the irradiated lengths of the deflection prisms and the prism arrangement ,

The embodiment of a light mixing device 80 in FIG. 7 shows, by way of example, that a large light path is possible in a small installation space by arranging two (or more) integrator bars 81, 82 in parallel, which can be a multiple of the direct distance between entry in the integrator rod and exit at the prism arrangement. A 180 ° deflection between the integrator rods is achieved by two identically dimensioned, totally reflecting deflection prisms 83, 84 arranged between the exit of the first rod 81 and the entry of the second rod 82. There is a sufficiently small air gap between the integrator bars and between them and the associated deflection prisms in order to allow total reflection within the optical components which are delimited by the straight surface.

Another measure that can be used as an alternative or in addition to the measures described consists in keeping an integrator rod possibly in its length, lowering the inner aperture by increasing the cross-section and providing at least one divided rod section on the rod which has two or more totally reflecting rods, whose overall cross-section essentially corresponds to the original cross-section of the rod. By reducing the cross section in the rods of the divided rod cross section, the total number of reflections is increased, so that the exit-side uniformity can be improved. An example of such an integrator rod 90 is shown in FIG. 8. It has an entry-side first rod section 91 with three identically dimensioned rods 92, a subsequent second divided rod section 93, which has only two identical rods 94 with the same cross-section, and an undivided rod section 95 on the outlet side, the length of which is dimensioned such that sufficient mixing is guaranteed overall. Instead of the two-stage division shown by way of example, it is also possible to provide only one divided section and one undivided rod section or more than two divided sections which precede an undivided rod section. Here too, care must be taken that the laterally opposite boundary surfaces of the rods are at a short distance from one another so that they can have a totally reflective effect. When using a polarization splitter layer, which is oriented obliquely to the direction of propagation of an open light beam, the degree of polarization of the radiation passing through will vary over the opening angle or the aperture of the rays, namely asymmetrically to the direction corresponding to the direction of propagation (corresponding to aperture NA = 0). , This is illustrated with the aid of FIG. 9, where it is shown that with an open beam bundle 100, which extends parallel to the longitudinal axis 101 of an integrator rod 102, the marginal beams of the beam bundle strike the polarization splitter layer 103 with different incidence angles. The angle of incidence (angle between the direction of incidence and the surface normal of the polarization splitter layer) varies symmetrically around the angle of incidence of the direction of incidence (normally approx. 45 °). However, since the transmittance of a polarization splitter layer normally does not vary symmetrically around the mean angle of incidence (typically in the range of 45 °, close to the Brewster angle), the rays of the tuft as a whole have an asymmetrical transmission with respect to the direction of incidence (NA = 0) T for p-polarized light. This situation is shown schematically in Fig. 10 (a).

The asymmetrical polarization for the opened tufts is compensated for by a mirror-symmetrical structure of the polarization splitter layers with respect to this mirror plane, which runs in the longitudinal direction of the rod and contains an intersection line between the polarization splitter surfaces. This arrangement results in a symmetrical distribution of the total transmittance for p-polarization at the exit (FIG. 10 (b)). In the example shown, this is achieved by a prism arrangement 105 which has a first prism group 106 and a second prism group 107, the two prism groups being arranged mirror-symmetrically to the mirror plane of the integrator rod 102. Any prism Group is constructed essentially the same as the prism arrangement 30 in FIG. 3, the second prisms 32, which are mirror-symmetrical to one another, being integrated into a single prism 108 behind the polarization splitter layers 103, 104 which are oriented at right angles to one another. This prism arrangement has two polarization splitter surfaces 103, 104, which are aligned mirror-symmetrically to the mirror surface of the integrator rod, each oriented by approximately 45 ° to the longitudinal axis of the rod, the asymmetrical effects of which on the incident radiation compensate one another.

An appropriate apodization filter in the REMA lens allows this value of the degree of polarization to be adjusted uniformly via the pupil. However, apodization is usually neither necessary nor appropriate. For the interference contrast, which is to be maximized in the foreground illumination types ring field and dipole illumination, the adjustment of the partial intensities of interfering beams is already achieved through the proposed symmetrical structure. Since an apodization filter generally destroys light, it can be omitted thanks to the symmetrical prism arrangement. 9 reduces the prisms by a factor of 2 when the rod geometry is enlarged. This can be advantageous since the individual prisms would have to be used in the best possible way with regard to crystal orientation, but it can be uncompensated, particularly at 157 nm , aperture-related contribution of intrinsic birefringence remains. This is not a problem at longer wavelengths, for example 193 nm, since prisms made of synthetic quartz glass can be used without intrinsic birefringence. Accordingly, as with all other embodiments, a combination of different suitable materials for the integrator rod and the prisms of prism arrangements and deflection devices is possible. 11 shows a possible overall structure of the optical components of a projection exposure system 110, which comprises an illumination system 111 for illuminating a photomask 112 and a projection objective 113 for imaging the photomask onto a wafer arranged in the image plane 114 of the projection objective. The lighting system has a pulsed laser 115 as the light source, behind which is arranged a λ / 2 plate 116 which can be rotated about the optical axis of the system. One of these downstream optics 117 transmits the light into the angle-maintaining, polarization-optimized light mixing device 118, which essentially corresponds to the structure and function of the light mixing device 10 in FIG. 1 and is designed to emit completely s-polarized light. The fully polarized exit light strikes the photomask 112 without the interposition of a REMA lens. If illumination of the mask with circularly polarized light is desired, a λ / 4 plate can be arranged in front of and behind the mask. The light polarized behind the mask 112 strikes a polarization splitter layer 117 of a beam splitter block 118 of the projection objective arranged obliquely in the light path and is deflected in the direction of the concave mirror 119 of the objective. A λ / 4 plate 120 arranged between the beam splitter block and the concave mirror ensures that the concave mirror and the upstream lenses are operated with circularly polarized light, while the light reflected back onto the beam splitter surface 117 is p-polarized and thus from the layer 17 in the direction of one the dioptric lens part of the projection lens downstream of the beam splitter cube is let through. This can include a deflection mirror 121 in order to achieve a parallel position of the photomask 112 and the wafer 114. An optional λ / 2 plate between the beam splitter cube and the deflecting mirror can ensure that the mirror 121 is operated with s-polarization in order to increase its degree of reflection. A λ / 4 plate 122 following in the direction of the wafer provides for illumination of the wafer and upstream objective lenses with circularly polarized light. In microlithography with pulsed lasers, good light stability between the individual light pulses of the laser 8 is desired, since only a finite number of pulses contribute to an exposure when scanning. There are various options for inversively illuminating the two scan fields one above the other. The simplest is to rotate the polarization of the input light between individual pulses or pulse groups by 90 °. Each point in the total exit surface 11 of the light mixing device thus continuously inverts its brightness from pulse to pulse or from pulse group to pulse group in such a way that two assigned pulses or pulse groups result in a temporal mean value which, free of any polarization properties, represents the mean value of the pulses emitted from the laser , Accordingly, when using pulsed lasers, a device for rotating the polarization direction of the light emitted by the laser, for example a rotatable λ / 2 plate 116, is preferably provided between the light source and the integrator rod. This is preferably controlled in such a way that light is emitted during an exposure interval with different orientations of the preferred polarization direction occurs approximately equally often in the light mixing device. A temporal averaging of different polarization states at the exit is thus achieved.

The system can be operated with maximum efficiency for all types of lighting, in particular ring field, quadrupole or dipole lighting. The use of phase masks is possible without restrictions. The scan mode (in the y direction) literally illuminates the reticle plane completely uniformly. By actuating the rotating λ / 2 plate 116 in such a way that approximately the same number of pulses with orthogonally aligned polarization preferred directions are transmitted during an exposure interval, uniform illumination of both outputs of the light mixing device 118 is achieved on average over time. Numerous variants of the system, for example with a REMA lens between the light mixing device and the reticle level are also possible.

When using imaging optics between the light mixing device and the reticle, it should be noted that the ideally prepared polarization state at the exit of the light mixing device, for example with s or p polarization, can still be changed by optical components within the subsequent objective, for example by intrinsic voltage double calculation in the lens material. This problem can be reduced by using a polarization filter 130 explained by way of example with reference to FIG. 12, which serves here as an intermediate polarizer in order to “refresh” the polarization state with p-polarization optimally prepared at the entrance of the objective 131. The polarization filter has a prism arrangement with at least three, usually significantly more, essentially isosceles prisms, which are arranged in an interlocking manner in such a way that facing catheter surfaces of the prisms form a zigzag arrangement that spans the entire cross-section of the filter The entire prism arrangement is fastened here on a separate, plane-parallel, transparent carrier 143, which can optionally also be formed in one piece with the prisms attached to it.

A polarization splitter layer is arranged in each case between the opposing catheter surfaces. This creates seamlessly adjacent pairs of polarization splitter layers 140, 141, the layers of a pair being inclined at an angle of approximately 90 ° in the direction of the incident light in such a way that the polarization splitter surface of the pair reflects (s-polarized.es) Light is deflected in the direction of the assigned other polarization splitting surface and is deflected again by this into one Direction of propagation, which runs essentially counter-parallel to the direction of incidence of the light. This creates a polarization-selective retro reflector that works (on average) like a (two-dimensional) cat's eye, only allows light with p-polarization to pass through and s-polarized light is completely reflected back. The shape shown has a high efficiency even with considerable angular loading, since there is no geometric shading.

This principle of intermediate polarization does not worsen the uniformity in the reticle, since the intermediate polarizer 130 lies in the region of the pupil of the REMA objective and thus at a location conjugated to the location of the projection objective pupil. At its output, the intermediate polarizer can be combined with an optical element 150 to generate a desired output polarization from the ideally p-polarized light behind the intermediate polarizer. For example, it can be a grid plate with a large number of suitable oriented λ / 2 facets for producing tangential polarization. Such a component is disclosed, for example, in DE 195 35 392, the disclosure content of which is made by reference to the content of this description.

A polarization filter of the type of polarization filter 130 can be used in other optical devices, regardless of the other features of the invention described here, in order to block components with s-polarization by back reflection and only p-polarization from light incident largely perpendicular to the filter plane with any polarization state pass. An arrangement in the area of small angular loads, for example in the area of a pupil of an objective, is advantageous for a high filter efficiency.

Claims

claims

1. Illumination system for an optical device, in particular for a projection exposure system for microlithography, with a light mixing device which has the following features: at least one integrator rod which has an entry surface for receiving light from a light source and an exit surface for emitting exit light mixed by the integrator rod , as well as at least one prism arrangement for receiving exit light and for changing the polarization state of the exit light, wherein the prism arrangement has at least one polarization splitter surface oriented transversely to the direction of propagation of the exit light.

2. Lighting system according to claim 1, wherein the prism arrangement has at least one mirror surface, which is arranged with respect to the polarization splitter surface either such that light reflected from the polarization splitter surface can be deflected with the aid of the mirror surface in a direction of propagation which is substantially parallel to the direction of propagation of the light transmitted by the polarization splitter surface runs or is arranged such that light transmitted by the polarization splitter surface can be deflected with the aid of the mirror surface in a direction of propagation which is essentially parallel to the direction of propagation of the light reflected by the polarization splitter surface.

3. Lighting system according to claim 1 or 2, in which an optically effective polarization splitter layer is arranged on the polarization splitter surface, which preferably has an optically active multilayer system with layers of alternately high breakdown the or low-refractive index, transparent dielectric material.

4. Lighting system according to one of the preceding claims, in which the prism arrangement has a polarization splitter block with a first and a second prism, which have mutually facing interfaces between which the polarization splitter surface, in particular the polarization splitter layer, is arranged.

5. Lighting system according to one of claims 2 to 4, in which the prism arrangement has at least one prism serving as a mirror prism, in which an interface forms the mirror surface, the mirror surface preferably being totally reflective.

6. Lighting system according to one of the preceding claims, in which the prism arrangement has at least one assembly with three prisms, two of the three prisms having mutually facing hypotenuse surfaces, between which the polarization splitting surface lies and the third prism has a hypotenuse surface which forms the mirror surface.

7. Lighting system according to one of the preceding claims, in which the prism arrangement has interfaces provided for the light entry or exit and at least some of the interfaces are coated with an anti-reflective layer.

8. Lighting system according to one of claims 4 to 7, in which a material-free gap is formed between the exit surface of the integrator rod and an entry surface of the polarization splitter block and / or between a light exit surface of the polarization splitter block and a deflecting prism, the gap preferably has a slit width which is on the order of a few wavelengths of the light wavelength used.

9. Lighting system according to one of the preceding claims, wherein the prism arrangement has at least one first exit surface for the exit of light transmitted through the polarization splitting surface and at least one second exit surface for exit of light reflected by the polarization dividing surface, at least one of the exit surfaces having an optical device for changing the polarization state of light passing through, in particular a delay element

10. Lighting system according to claim 9, in which one of the exit surfaces is followed by a device for rotating the preferred polarization direction of the passing light by 90 °, in particular in the form of a half-wave plate.

11. Lighting system according to claim 8 or 9, in each of the two exit surfaces a device for converting incoming linearly polarized light into circularly polarized light, in particular a quarter-wave plate, is connected downstream.

12. Lighting system according to one of the preceding claims, wherein the polarization splitter surface is oriented such that an intersection line between the polarization splitter surface and a plane oriented perpendicular to the exit direction of the light is transverse, in particular perpendicular to a direction (y-direction) which is a scanning direction of a Wafer scanner is assigned.

13. Lighting system according to one of the preceding claims, wherein the prism arrangement a first prism group with egg ner first polarization splitter surface and a second prism group with a second polarization splitter surface, wherein the first and the second prism group are arranged mirror-symmetrically to a mirror plane of the integrator rod.

14. Lighting system according to one of the preceding claims, in which the light mixing device maintains the angle, has an entry surface with an entry surface cross section and an exit surface with an exit surface cross section that deviates from the entry surface cross section.

15. Lighting system according to claim 14, in which the exit surface cross section is larger than the entry surface cross section, wherein the exit surface cross section is preferably an integral multiple of the entry surface cross section.

16. Lighting system according to one of the preceding claims, in which the prism arrangement is arranged such that the direction of propagation of the light emerging from the light mixing device is transverse, preferably substantially perpendicular to the direction of propagation of the light incident in the light mixing device.

17. Illumination system according to one of the preceding claims, in which a pulsed laser is provided as the light source for emitting a plurality of laser pulses, a device for rotating the polarization direction of the light of the light source being arranged between the light source and the light mixing device, in particular a rotatable half-wavelength plate, and wherein the device for rotating the light can be controlled or controlled in such a way that light pulses with different polarization orientations alternate during an exposure interval. preferential direction, in particular with orthogonally aligned polarization preferential directions, enter the light mixing device.

18. Lighting system according to one of the preceding claims, in which at least one integrator rod is provided, which consists of a transparent material whose absorption edge is at lower wavelengths than the absorption edge of calcium fluoride, magnesium fluoride or lithium fluoride being preferably used as the rod material.

19. Lighting system according to one of the preceding claims, wherein the light mixing device has an integrator rod arrangement with a plurality of integrator rods and wherein at least one point of the integrator rod arrangement between a first integrator rod and a subsequent second integrator rod, at least one angle-maintaining deflection device for deflecting the direction of light travel is provided, the deflection device is preferably designed as a deflection prism.

20. Lighting system according to claim 19, in which the integrator rod arrangement has at least three integrator rods arranged at an angle to one another, between each of which a deflection, preferably by 90 °, is provided.

21. Lighting system according to claim 19 or 20, in which the integrator rod arrangement has at least two integrator rods which are aligned essentially parallel to one another, at least one deflection device being provided between the outlet surface of an upstream integrator rod and the inlet surface of a downstream integrator rod.

22. Lighting system according to one of the preceding claims, in which at least one integrator rod is provided which has an undivided rod section immediately in front of its exit surface and at least one divided rod section upstream of the undivided rod section, which at least two essentially completely, totally reflecting the total cross section of the integrator rod Has chopsticks.

23. Lighting system according to one of the preceding claims, in which the integrator rod consists of a first material and at least one prism of the prism arrangement and / or at least one deflection prism made of a second material, which differs from the first material.

24. The lighting system of claim 23, wherein the first material is calcium fluoride, magnesium fluoride or lithium fluoride.

25. Lighting system according to claim 23 or 24, wherein the second material is optically isotropic, wherein the second material is preferably calcium fluoride, barium fluoride or synthetic quartz glass.

26. Lighting system according to one of the preceding claims, in which a beam splitter block is provided with an entry-side prism, a polarization splitter surface and an exit-side prism and in which the material of the prisms is selected as a function of the refractive index ratios in the polarization splitter layer so that a misalignment between the Direction of incidence of the light incident on the polarization splitter layer and a direction corresponding to the Brewster angle of the polarization splitter layer with regard to maximum Transmittance of the polarization splitter layer is optimized for p-polarized light, in particular minimized.

27. Lighting system according to one of the preceding claims, in which a thin layer having a phase-correcting or phase-maintaining effect is applied to at least one interface of an integrator rod and / or the prism arrangement and / or a deflecting prism provided for reflection.

28. Lighting system according to one of the preceding claims, in which a phase-maintaining or phase-correcting coating with anti-reflective effect is applied to at least one interface of an integrator rod and / or the prism arrangement and / or a deflecting prism provided for light entry or exit.

29. Lighting system according to one of the preceding claims, in which the light mixing device is assigned at least one diaphragm for setting the local distribution of the energy of an illumination field generated by the light mixing device, the diaphragm preferably being movable diaphragm elements for controlled change in the width of a lighting field as a function of positions along the length of the lighting field.

30. Lighting system according to one of the preceding claims, in which no optical imaging system is arranged between the outlet of the light mixing device and the image plane of the lighting system.

31. Lighting system according to one of claims 1 to 29, in which an optical imaging system is arranged with at least one pupil plane between the exit of the light mixing device and the image plane of the illumination system, which is a Fourier-transformed plane to the image plane of the illumination system.

32. Lighting system according to claim 31, in which a polarization filter is provided in the region of the pupil plane for influencing the polarization state of light, which is incident on the polarization filter along a direction perpendicular to a filter plane, the polarization filter being a polarization-selective filter for transmitting light components of a polarization direction and for blocking light components of the other polarization preferred direction.

33. Lighting system according to claim 32, in which the polarization filter is designed as a polarization-selective retroreflector in the manner of a cat's eye with a plurality of polarization splitter surfaces arranged at an angle to one another.

34. Lighting system according to claim 32 or 33, wherein the polarization filter has a prism arrangement with at least one pair of V-shaped polarization splitter surfaces, which are inclined at an angle of approximately 90 ° in the direction of the incident light such that from a polarization splitter surface A pair of reflected light is deflected in the direction of the assigned other polarization splitting surface and is deflected again by the latter in a direction of propagation which runs essentially counter-parallel to the direction of incidence of the light.

35. Lighting system according to claim 34, wherein the polarization filter a plurality of pairs of V-shaped polarization splitter arranged has layers that form a zigzag arrangement spanning the entire useful cross section of the filter.

36. Polarization filter, in particular for use with ultraviolet light from a wavelength range of less than 260 nm, for generating completely linearly polarized light from input light which is incident essentially along an optical axis of the polarization filter, the polarization filter being a polarization-selective retroreflector in the manner of a cat's eye a plurality of polarization splitter surfaces arranged at an angle to one another is formed.

37. Polarization filter according to claim 36 with the features of the characterizing part of at least one of claims 34 and 35.

38. Projection exposure system for microlithography, characterized in that it comprises an illumination system according to one of the preceding claims 1 to 34.

39. A method for producing semiconductor components and other finely structured components, comprising the following steps: providing a mask with a predetermined pattern; Illumination of the mask with ultraviolet light of a predetermined wavelength with the aid of an illumination system according to one of claims 1 to 34; and

Projecting an image of the pattern onto a light-sensitive substrate arranged in the area of the image plane of a projection objective.