Illumination system, projection illumination device, and projection illumination method

Abstract

An illumination system (ILL) for a microlithographic projection illumination facility for illuminating a sample disposed in a region of an object plane (OS) of a downstream projection lens (PO) with illumination light generated from light from a primary light source (LS) is designed as a dual-field illumination system that receives a single light beam coming from the primary light source (LS) and generates two illumination beams (BS1, BS2) therefrom, where a first illumination beam (BS1) can be guided along a first illumination beam path to a first illumination field (ILF1) disposed outside an optical axis of the projection lens within an exit surface (ES) of the illumination system, and simultaneously, a second illumination beam (BS2) can be guided along a second illumination beam path to a second illumination field (ILF) disposed outside the optical axis within the exit surface, on the side opposite the first illumination field (ILF1) associated with the optical axis (AX).

Description

Technical Field

[0001] The following disclosure is based on a German patent application with filing reference 102022205273.0, filed on May 25, 2022. The disclosure content of that patent application becomes the content of this application by reference.

[0002] The present invention relates to an illumination system for illuminating a pattern arranged on an object plane of a projection lens. The present invention further relates to a projection exposure apparatus having such an illumination system, and a projection exposure method that can be carried out with the aid of the illumination system.

Background Art

[0003] Today, the microlithography projection exposure method is mainly used to create semiconductor devices and other microstructured components. In this case, a mask (reticle) that supports or creates the pattern of the structure to be imaged, for example, the line pattern of the layer of a semiconductor device, is used. The pattern is arranged in the region of the object plane of the projection lens between the illumination system and the projection lens in a projection exposure apparatus, and is illuminated in the region of the effective object field by the illumination radiation provided by the illumination system. The effective object field is the part of the object field that can be used for the image and is actually used for the image. The radiation modified by the pattern travels as a projection beam through the projection lens, and the projection lens images the pattern onto the substrate to be exposed in the region of the effective image field that is optically conjugate to the effective object field. The substrate usually supports a layer (photoresist) that is sensitive to projection radiation.

[0004] When selecting an appropriate projection exposure apparatus and method for a lithography process, various technical and economic criteria, especially based on the typical structural size of the structure to be created in the substrate to be exposed, must be taken into account.

[0005] A projection exposure apparatus having a high NA projection lens typically operates at an operating wavelength within the range of deep ultraviolet radiation (DUV), for example, about 193 nm, and is used to create relatively fine critical structures.

[0006] In contrast, to create a medium critical layer or a non-critical layer having a typical structure size significantly exceeding 150 nm, a projection exposure apparatus designed for an operating wavelength exceeding 200 nm has traditionally been used. In this wavelength range, purely refractive (dioptric) reduction lenses are often used.

[0007] Here, projection exposure apparatuses (so-called i-line systems) for an operating wavelength of 365.5 nm ± 2 nm have been used for a long time. They use the i-line of a mercury lamp, and its natural bandwidth is limited to a narrower use bandwidth Δλ, for example, approximately 2 nm, by a filter or other means. With such a light source, ultraviolet light in a relatively wide wavelength band is used for projection.

[0008] Most conventional projection exposure apparatuses are designed to image a single effective object field onto a single effective image field. For example, there is also a technique of simultaneously using two beam paths to increase throughput.

[0009] U.S. Patent No. 8,634,060 describes a projection exposure apparatus capable of simultaneously exposing two masks and two wafers. Light from a single light source is alternately sent through two separate identical projection systems each including an illumination system and a projection lens via a high-speed optical switch.

[0010] U.S. Patent Application Publication No. 2008 / 259440 describes a projection exposure apparatus that functions with two separate masks and two separate illumination systems, and the projection beam paths within the projection lens are fused via a triangular prism.

[0011] U.S. Patent Application Publication No. 2010 / 0053738 (corresponding to U.S. Patent No. 8,705,170) describes a projection lens that uses a single mask and branches the projection beam path within the projection lens with the aid of a deflection mirror so that two separate image-side lens portions are formed to generate two image fields of view, as a result of which two wafers can be exposed simultaneously. U.S. Patent Application Publication No. 2010 / 0053583 discloses a suitable illumination system that can simultaneously illuminate two separate illumination fields arranged at a distance from each other on the same mask. A diffractive optical element or a prism is provided to split the beam coming from the light source. A lens array of a fly-eye lens is provided for homogenization of the illumination radiation.

[0012] A projection exposure apparatus having two projection beam paths is described in U.S. Patent No. 8,384,875 using, for example, a schematic example. To illuminate the mask, two illumination systems are provided, which can be constructed separately from each other or integrated into a common illumination system (FIG. 12). There is also a schematic example of a refractive reflective projection lens. Specification data for repairing the system is not disclosed.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0013] In view of this background, an object of the present invention is to provide a practically realizable concept for a dual-field illumination system, a projection exposure apparatus equipped with the same, and a projection exposure method that can be carried out thereby.

MEANS FOR SOLVING THE PROBLEMS

[0014] According to the description of the present invention, this object is achieved by an illumination system having the features of claim 1, a projection exposure apparatus having the features of claim 9, and a projection exposure method having the features of claim 11. Advantageous developments are defined in the dependent claims. The description of all claims is incorporated herein by reference.

[0015] According to one description of the present invention, an illumination system for a microlithographic projection exposure apparatus is provided. The illumination system is configured to illuminate a pattern disposed in a region of the object plane of a downstream projection lens with illumination light generated from light from a primary light source. The illumination system is designed as a dual-field illumination system that receives a single light beam originating from the primary light source and creates two illumination beams therefrom. During operation, the first illumination beam is guided along a first illumination beam path to a first illumination field disposed outside the optical axis of the projection lens within the exit surface of the illumination system. At the same time, the second illumination beam is guided along a second illumination beam path to a second illumination field that is on the opposite side of the first illumination field with respect to the optical axis and is disposed outside the optical axis within the exit surface. The exit surface of the illumination system corresponds to the object plane of the projection lens.

[0016] The illumination system includes a refractive pupil shaping unit that receives light from the primary light source and generates a two-dimensional intensity distribution on a pupil shaping surface of the illumination system. The two-dimensional intensity distribution at the pupil shaping surface substantially determines the angular distribution of the light rays guided to the exit surface. Further, a refractive field shaping system optically downstream of the pupil shaping unit is provided, and the refractive field shaping system includes a homogenizing unit that homogenizes the light received from the pupil shaping unit and divides the illumination light into a first illumination beam and a second illumination beam.

[0017] The pupil shaping unit shapes the two-dimensional intensity distribution solely with the aid of refractive optical elements, i.e., by refraction of light that is adjusted on a correspondingly designed smooth surface of the optical elements. The use of one or more diffractive optical elements is dispensed with. Diffractive optical elements, in principle, offer the possibility of creating one or more output beams with highly individually adjustable characteristics from an input beam, but beam shaping via diffraction is usually associated with light losses and stray light is created, which can have an adverse effect on the function. On the other hand, when the pupil shaping unit is constructed solely of refractive optical elements, pupil illumination can be generated with low light losses.

[0018] To ensure that the illumination field is illuminated as homogeneously as possible by the light from the light source and, at the same time, the light loss between the pupil shaping surface and the exit surface remains low, a refractive field shaping system is provided that includes a homogenizing unit for homogenizing the light received from the pupil shaping unit and splitting the illumination light into a first illumination beam and a second illumination beam.

[0019] Therefore, this assembly has, precisely, a dual function which is the task of homogenizing the illumination radiation and splitting it into two illumination beams. The splitting is due to a special design of the optical components of the homogenizing unit. By integrating several functions (homogenization and splitting) by the optical components of the homogenizing unit, it contributes to illuminating the pattern with as little loss of intensity as possible using the light from the primary light source, thereby also contributing to increasing the throughput.

[0020] There are functionally different ways to implement this concept.

[0021] In a group of embodiments, the homogenizing unit has a first grid configuration having a first refractive grid element for receiving light of a two-dimensional intensity distribution and generating a grid configuration of secondary light sources, and a downstream second grid configuration having a second refractive grid element for receiving light from the secondary light sources and at least partially overlapping the light from the secondary light sources within the exit surface. Each of the first grid elements is used to split the beam into a number of optical channels. Each of the first grid elements generates an optical channel belonging to the secondary light source. The shape or aperture of the first grid element usually determines the shape of the illumination field. For example, the first grid element can be rectangular.

[0022] Each of the second grid elements is formed by a lens element assigned to two adjacent first grid elements and having a first portion located in a first optical channel and a second portion located in a second optical channel, and these portions have different surface shapes and thus different optical effects.

[0023] Preferably, the configuration is such that the first grid elements adjacent in one direction are alternately assigned to the first illumination field and the second illumination field. This contributes to a uniform distribution of the intensity distribution resulting from the pupil shaping surface across the illumination fields. Since each illumination field receives intensity from substantially closely adjacent locations within the pupil shaping surface, the two illumination fields have substantially the same angular distribution, and as a result, the illumination conditions of the patterns in both illumination fields are also substantially the same.

[0024] To achieve the most uniform intensity distribution across both illumination fields, preferably, at least one surface of the lens elements within the second grid element is curved aspherically. Another surface may be curved spherically, which simplifies manufacturing. However, preferably, the incident surface and the exit surface are curved aspherically such that the second grid element is similar to a double aspherical lens at this point.

[0025] To very sharply divide the radiation incident on the lens element into two illumination fields to be illuminated, preferably, a bending line extending between the first part and the second part of the lens element is provided on at least one surface of the lens element, that is, a line forming a transition between adjacent parts that cannot be continuously differentiated.

[0026] The first grid configuration and the second grid configuration can be regarded as an integral part of a specially designed fly-eye lens. The second grid configuration consists substantially of an off-axis lens element part, at least one side of which is aspherical, and each size corresponds to the size of the assigned first grid element. In the second grid configuration, a dense configuration of refractive power with a non-continuously differentiable transition part is obtained. In particular, a dense configuration of refractive power with two different surface shapes that are alternating in the spatial direction can be provided.

[0027] In another group of embodiments, the homogenizing unit includes an integrator rod configuration having an incident integrator rod with an incident surface and an exit surface, a first exit integrator rod optically coupled to a first partial surface of the exit surface, and a second exit integrator rod optically coupled to a second partial surface of the exit surface, wherein the exit surface of the first exit integrator rod is assigned to a first illumination field and the exit surface of the second exit integrator rod is assigned to a second illumination field.

[0028] Such a homogenizing unit uses different light mixing principles. The integrator rod is essentially a long rod made of a material that is transparent to the illumination light. The cross-section of the rod is usually polygonal, for example rectangular. The rod has an incident surface facing the light source optically and an opposite exit surface. Light entering the incident surface at an appropriate angle is, optionally, reflected several times by total internal reflection at the side surfaces of the integrator rod and then exits through the exit surface in a substantially homogenized form. By setting the angular distribution at the entrance, the number of total internal reflections of the light rays at the side surfaces, and thus the homogenization effect, may be affected.

[0029] In the integrator rod configuration, the splitting into two illumination beam paths takes place at the exit surface of the incident integrator rod. There is a virtual separation point between the first partial surface and the second partial surface in order to split the exiting light over two independent exit integrator rods operating in parallel. The exit integrator rods can be directly coupled to the exit surface of the incident integrator rod without the need for further intermediate optical elements. Furthermore, it is also possible to provide one or more optical elements between the incident integrator rod and the exit integrator rods for deflecting the passing radiation.

[0030] In some embodiments, the input integrator rod and the output integrator rod each have a constant cross-sectional shape and cross-sectional size in the axial direction, and between the output surface of the input integrator rod and each of the input surfaces of the output integrator rod, from a location close to the axis with reference to the central axis of the input integrator rod to a location of the output integrator rod located away from the axis at a distance from the central axis of the input integrator rod, a prism configuration for changing the direction of the beam is arranged. With respect to the central axis, then, the input surface of the input integrator rod is centered with respect to the central axis, while the output surface of the output integrator rod is positioned on both sides of the central axis at a distance from this central axis.

[0031] There are also embodiments without an intermediate prism configuration. According to one exemplary embodiment, the first output integrator rod and the second output integrator rod are formed as a "tapered integrator", and the cross-sectional size continuously decreases from the incident side to the output side. Here too, the input surface is preferably directly coupled to the first partial surface and the second partial surface of the output surface of the input integrator rod. If necessary, a prism configuration may be provided, for example, for beam deflection.

[0032] Further advantages and aspects of the present invention will become apparent from the claims and from the description of the exemplary embodiments of the present invention described below with reference to the figures.

Brief Description of the Drawings

[0033]

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DETAILED DESCRIPTION OF THE INVENTION

[0034] In the following description of the preferred embodiments, the term "optical axis" represents a sequence of straight lines or straight line segments passing through the centers of curvature of optical elements. The optical axis is folded by a folding mirror (deflection mirror) or other reflecting surface. In this example, the object is a mask (reticle) having a pattern of an integrated circuit, which may also be related to different patterns of, for example, a grid. In this example, the image is projected onto a wafer provided with a photoresist layer, and the wafer functions as a substrate. Other substrates, for example, elements for a liquid crystal display or a substrate for an optical grating substrate are also possible.

[0035] FIG. 1 shows an example of a microlithography projection exposure apparatus PBA, which is usable for the manufacture of semiconductor devices and other microstructured components and operates with light or electromagnetic radiation from the ultraviolet (UV) range in order to obtain a resolution down to units below micrometers. A mercury lamp functions as a primary radiation source or light source LS. The lamp emits a broad spectrum having emission lines of relatively high intensity I in a wavelength range having center wavelengths of about 436 nm (visible light, blue, g-line), about 405 nm (visible light, violet, h-line), and about 365.5 nm (near ultraviolet, UV-A, i-line).

[0036] The projection exposure apparatus is an i-line system that uses only light from the i-line, i.e., UV light near the center operating wavelength of about 365.5 nm. The natural full bandwidth of the i-line is limited to a narrower use bandwidth Δλ of, for example, approximately 2 nm, with the help of a filter or in another way.

[0037] At its exit surface ES, the illumination system ILL connected downstream of the light source LS generates, from the light from this single primary light source, in any case, two large, clearly delimited, and substantially homogeneously illuminated illumination fields ILF1, ILF2 at a beam angle that conforms to the telecentricity requirements of the projection lens PO arranged downstream in the optical path.

[0038] The optical element that receives light from the light source LS and forms the light illumination radiation directed towards the reticle M is part of the illumination system ILL of the projection exposure apparatus. The illumination system is a dual-field illumination system. Exemplary embodiments will be described below in connection with FIGS. 3 to 8.

[0039] The illumination system ILL has devices for setting different illumination modes (illumination settings), and can, for example, switch between conventional on-axis illumination with different degrees of coherence σ and off-axis illumination.

[0040] Downstream of the illumination system, a device RS for holding and operating the mask M (reticle) is arranged such that the pattern arranged on the reticle coincides with the exit plane ES of the illumination system, and here is located on the object plane OS of the projection lens PO, which is also called the reticle plane OS.

[0041] The substrate to be exposed is, in an exemplary case, a semiconductor wafer W, and is held by a device WS including a scanner drive unit to move the wafer in the scanning direction (y direction) in synchronization with the reticle M perpendicular to the optical axis OA. The device WS, also called the "wafer stage", and the device RS, also called the "reticle stage", are an integral part of the scanner device controlled by a scanning control device integrated into the central control device CU of the projection exposure apparatus PBA in this embodiment.

[0042] FIG. 2 shows a schematic top view of the object plane OS of the projection lens PO (corresponding to the exit plane ES of the illumination system). As shown in this example, the illumination system ILL illuminates two off-axis illumination fields ILF1, ILF2 with light from the light source at the exit surface (reticle surface, object plane of the projection lens). These illumination fields are each rectangular, can be sharply or gently delimited, and are illuminated substantially homogeneously. Each of the illumination fields defines the effective object field actually used in the projection exposure, and as a result, the first effective object field OF1 and the second effective object field OF2 are positioned on the reticle surface. The two nominally identical-sized rectangular effective object fields are in the y direction on both sides of the optical axis OA, each is spaced outside the optical axis, and the height A measured parallel to the y direction* and a width B measured perpendicular to the y direction (in the x direction or the cross-scanning direction) * >A * and has, for example, an aspect ratio AR = B * / A * which can be, for example, 2, 2.5, 3, 5, 10, or 15.

[0043] In the case of the example, the effective rectangular field of view (i.e., what is actually used for imaging) has, respectively, a width B * = 104 mm and a height A * = 56 mm. The distance ABF (field distance) between the corresponding field perimeters in the y direction is the sum of twice the distance d of the field from the optical axis, i.e., 2 × 38 mm, plus the field height (56 mm), i.e., 132 mm. The circle OBC is formed from a rectangle having a side B * in the x direction (= 104 mm) and 2 * (in the y direction (scanning direction)) * (A * + d * )(= 188 mm).

[0044] In a rotationally symmetric system, the circle OBC centered on the optical axis OA encloses the effective object fields of view OF1, OF2, touches them at their corners, determines the size of the object field circle, within which optical correction must correspond to the specifications for all field points. This also applies to all field points within the effective object field of view. The larger this object field of view has to be made, the more complex the correction of aberrations becomes. In this case, the size of the circle is parameterized by the object field radius OBH or half of the object field diameter, which simultaneously corresponds to the maximum field height of the object field points. The object field height OBH is approximately 107 mm.

[0045] The effective image fields of view IF1, IF2 in the image plane IS optically conjugate to the effective object fields of view OF1, OF2 have the same shape as the associated effective object fields of view and the same aspect ratio between the height A and the width B, but the absolute field size is reduced by the imaging scale β of the projection lens in the case of a reduction projection lens ((│β│ < 1), i.e., A = |β|A * and B = |β|B* It is.

[0046] In any case, the distance ABF (field distance) measured in the scanning direction (y-direction) between the edges of the effective object field on the same side in the y-direction is selected such that the corresponding distance between the corresponding longer edges of the effective image fields IF1 and IF2 is the length of the "die" to be accurately exposed. This length is 33 mm in the current standard. In semiconductor and microsystem technology, the term "die" refers to a single unsealed piece of a semiconductor wafer as a single semiconductor chip without a housing or package.

[0047] FIG. 3 shows a schematic view of a first exemplary embodiment of the illumination system ILL. The primary light source LS is a mercury lamp with a condenser mirror, and the condenser mirror reflects light and collects it at the entrance aperture of the illumination system. An alternative (not shown) uses a laser as the light source, for example, a frequency-tripled solid-state laser having a wavelength of about 355 nm.

[0048] The pupil shaping unit PFU follows the primary light source. The pupil shaping unit PFU is constructed only of refractive optical components and is designed to generate a defined local (two-dimensional) intensity distribution at the subsequent pupil surface PUP of the illumination system ILL, and is sometimes also called a secondary light source or illumination pupil. Since the essential characteristics of the illumination radiation are affected or directed by this local intensity distribution, this pupil surface is also called the pupil shaping surface PUP.

[0049] The pupil shaping unit PFU can be made adjustable, and as a result, different local illumination intensity distributions within the circular illumination pupil, for example, a circular illumination spot centered on the optical axis AX, a dipole illumination, or a quadrupole illumination, can be set according to the control of the optical components of the pupil shaping unit, using conventional illumination settings.

[0050] The anamorphic field shaping system FFS is optically connected downstream of the pupil shaping unit PFU. It includes optical components that shape the illumination intensity distribution at the exit surface ES of the illumination system from the light from the pupil shaping surface. The field shaping system FSF includes a homogenization unit HOM for homogenizing the light received from the pupil shaping unit. The homogenization unit has a dual function, because the optical components are further designed to split the illumination light into a first illumination beam BS1 and a second illumination beam BS2 and to incident them on the exit surface at a distance from each other. The anamorphic field shaping system FFS includes an input coupling optical unit EK, and the input coupling optical unit EK collects the light coming from the pupil shaping surface and couples it to the entrance surface EF1 of the integrator rod configuration ISA. This is shown enlarged in Figure 4.

[0051] The integrator rod configuration ISA includes a flat entrance surface EF1, a flat exit surface EF2 parallel thereto, and an entrance integrator rod IE having four flat side surfaces forming a rectangular cross section. The entrance integrator rod is made of a material transparent to the illumination light. The light is mixed within the entrance integrator rod by multiple total reflections at the uncoated or optionally coated outer surfaces (side surfaces) of the integrator rod, thereby being homogenized and exiting from the exit surface AF1 in a homogenized or at least partially homogenized form. The entrance integrator rod has a continuously rectangular cross section and defines a longitudinal central axis that lies on the optical axis AX of the illumination system.

[0052] The integrator rod configuration further includes a first exit integrator rod IA1 and a second exit integrator rod IA2, each having an entrance surface EF2-1 and EF2-2 respectively, and an exit surface AF2-1 and AF2-2 respectively. The two exit integrator rods IA1 and IA2 each have a rectangular cross-sectional shape and have a cross-sectional area that is substantially half of the cross-sectional area of the entrance integrator rod IE.

[0053] The output integrator rods IA1 and IA2 are arranged diametrically opposite at a distance from the optical axis AX of the illumination system. The first output integrator rod IA1 is optically coupled to the first partial surface TF1 of the output surface of the input integrator rod such that the light emerging through the first partial surface TF1 enters only the first output integrator rod IA1. The same applies to the opposite side, and the light from the partial surface TF2 enters the second output integrator rod IA2.

[0054] Between the input integrator rod IE and the two output integrator rods IA1 and IA2, two prisms P1 and P2 of a prism configuration PA are arranged. The first prism P1 directly adjoins the first partial surface TF1 with an intermediate gap LS and has a rectangular flat input surface that receives the radiation emerging from this partial surface. The flat output surface has the same size and is located with an intermediate gap immediately in front of the input surface of the first output integrator rod IA1. The prism further has two flat side surfaces that are oriented at an angle of 45° with respect to the input and output surfaces, and each has a reflective coating. They can be made reflective, for example, by applying an aluminum layer or a dielectric coating.

[0055] The two deflections at the mirror surfaces of the prism with parallel offsets deflect the light emerging from the partial surface TF to a position further away from the optical axis. Thus, each of the prisms optically connects one of the output integrator rods IA1, IA2 to the assigned partial surfaces TF1, TF1 of the output surface AF1 of the input integrator rod and guides the light from a position close to the axis to a place far away from the axis.

[0056] Using this configuration, the light entering the input integrator rod IE is evenly divided into substantially equal parts across the output surface AF2-1 of the first output integrator rod and the output surface AF2-2 of the second output integrator rod, and at the same time, is mixed by multiple total internal reflections in both the input integrator rod and the output integrator rods.

[0057] In the immediate vicinity of the exit part of the first exit integrator rod IA1, there is an intermediate field plane ZE of the illumination system. An adjustable field stop BL1 is arranged there, whereby the actual usable field size of the first illumination field IF1 can be adjusted without limit. A corresponding second field stop BL2 is arranged at the exit part of the second exit integrator rod.

[0058] A subsequent lens REMA, also known as a REMA lens, images the intermediate field plane of the reticle mask system onto the exit surface of the illumination system or the object plane of the subsequent projection lens. Thus, the first illumination beam generates a first illumination field ILF1 on one side of the optical axis AX, while the second illumination field ILF2 is illuminated on the opposite side at a distance from the optical axis with the aid of the second illumination beam SB2.

[0059] Figures 5A to 5C show some variations of this basic concept. The variation in Figure 5A differs from the example in Figure 4 in that the prisms P1 and P2 are replaced by a pair of triangular prisms. The hypotenuse surfaces of the triangular prisms are in each case reflective, and the incident and exit surfaces are flat and adjacent to the upstream or downstream element via a gap.

[0060] Figure 5B shows that additional integrator rods ISW1, ISW2 can in each case be integrated between the incident integrator rod IE and the two exit integrator rods IA1, IA2.

[0061] Figures 5C and 5D show that a prism configuration PA that results in a split into two illumination beam paths does not necessarily have to be directly coupled to the exit side of the incident integrator rod. Rather, additional deflection elements and / or integrator rod elements can be interposed.

[0062] In the exemplary embodiment of FIG. 6, there are no intermediate prisms and / or other optical elements between the incident integrator rod IE and the two output integrator rods IA1 and IA2. In this exemplary embodiment, both output integrator rods are each designed as so-called "tapered integrators". In each of the output integrator rods IA1, IA2, the size of the rectangular incident surfaces EF1, EF2 substantially corresponds to half of the area of the output surface AF1 of the incident integrator rod IE, so that the light emerging from the associated partial surface is fully coupled into the output integrator rod. However, in the previous example, the integrator rods each have a constant cross-sectional shape and cross-sectional size over their length, whereas in the example of FIG. 6, the cross-sectional area of the output integrator varies continuously between the incident surface and the output surface, so that the two output surfaces AF2-1 and AF2-2 are arranged diametrically opposite to the optical axis at a distance from the optical axis. By increasing the angle while passing through the tapered integrator rod, different illuminations may be required at the entrance of the incident integrator rod, and the rod illumination is adapted so that no violation of the conservation of étendue occurs.

[0063] Next, based on FIGS. 7 and later, different exemplary embodiments of the illumination system ILL are described. For clarity, functional groups having functions similar or corresponding to those of the first exemplary embodiment are explicitly indicated accordingly. A significant difference from the previous exemplary embodiment lies in the configuration and operation of the homogenizing unit HOM, which is substantially constructed with the aid of a modified fly-eye lens. Details regarding the configuration and function are shown in FIG. 8.

[0064] The homogenization unit HOM receives the light of the two-dimensional intensity distribution of the pupil shaping surface PUP and includes a first grid configuration RA1 having a number of first refractive grid elements RE1 that generate a grid configuration such as secondary light sources SL1, SL2, etc. The grid configuration such as secondary light sources SL1, SL2, etc. is formed approximately at a distance of the focal length F1 of the first refractive grid element RE1 downstream of the first refractive grid element RE1. In this way, the illumination beam coming from the pupil shaping surface is divided into a number of optical channels, and each illuminated first grid element and the associated secondary light source are part of a separate optical channel.

[0065] There is a second grid configuration RA2 having second refractive grid elements RA2. The second grid configuration RA2 is arranged optically downstream of the first grid configuration, for example, in the region of the secondary light source SL1, etc. It receives the light from each optical channel or secondary light source and helps contribute to the at least partial overlap of the light coming from different optical channels in the region of the exit surface or image surface of the illumination system ILL. This overlap results in the homogenization of the light intensity at the exit surface.

[0066] The cross-sectional area or aperture of the first grid element RE1 determines the shape of the illuminated illumination field, which is rectangular in this exemplary case. The first grid element RE1 is also called a field honeycomb.

[0067] The second grid element RE2, also called a pupil honeycomb, is arranged near each secondary light source. They image the first grid element RE1 onto the intermediate field surface FE of the illumination system via a downstream field lens element. Then, the intermediate field surface is imaged onto the exit surface of the illumination system as in the above example.

[0068] A special feature of this homogenization unit is that each of the first grid elements RE1 generates an optical channel (like a conventional fly-eye lens) belonging to the secondary light source.

[0069] However, each of the second grid elements RE2 is not assigned to only one first grid element, but also to two directly adjacent first grid elements, for example, grid elements RE1-1 and RE1-2. Each of the second grid elements is formed by a lens element divided into two parts of different shapes. The first part AB1 acts only on the light of the assigned first grid element within its optical channel. The second part AB2 is formed integrally with the first part, positioned only in the adjacent second optical channel, and accordingly affects its light propagation.

[0070] In this exemplary case, the first optical channel created by the grid element R1-1 is affected by the lower half or the first part AB1 of the subsequent second grid element such that light is input into the first illumination beam BS1 through the field lens FL, while the light coupled into the second optical channel by the adjacent first grid element R1-2 is affected by the second part AB2 of the second grid element, and as a result, is coupled into the second illumination beam BS2, and the second illumination beam BS2 propagates on the opposite side with respect to the first illumination beam with reference to the optical axis AX.

[0071] To achieve strongly different optical effects in the second grid element RE2, preferably, both the incident surface and the exit surface are provided to be aspherical in the first part AB1 and the second part AB2, respectively. The surface shape of the first part and the surface shape of the second part do not smoothly merge with each other. Rather, a bending line occurs as the separation line between the two parts on the surface of the second grid element.

[0072] Accordingly, the feature of this hybrid concept is that a dense configuration of several refractive powers with two different surface shapes, which are alternating in one spatial direction, is created in the region of the pupil honeycomb (second grid element RE2). In particular, there is a dense configuration of refractive powers with a non-differentiable transition. The second grid element RE2 (pupil honeycomb) can be considered as a lens element composed of an off-axis lens element part, and preferably, at least one of its sides is aspherical, and each size corresponds to the size of the associated field honeycomb.

[0073] FIG. 9 shows a schematic meridional lens element cross-sectional view of an embodiment of a catadioptric projection lens PO with a selected beam to clarify the imaging beam path of the projection radiation passing through the projection lens during operation. The projection lens is provided as an imaging system having a reduction effect for imaging the pattern of a mask disposed on an object surface OS, for example, at a scale of 1:4, onto an image surface IS oriented parallel to the object surface.

[0074] The projection lens is designed according to one embodiment of the claimed invention and has an image-side numerical aperture NA in the range of 0.2 < NA < 0.4, for example, NA = 0.3.

[0075] The projection lens is designed as a dual-field projection lens. It images a first effective object field OF1 disposed outside the optical axis OA in the object surface OS along a first projection beam path RP1 into a first effective image field IF1 located outside the optical axis OA in the image surface IS, and at the same time, images a second effective object field OF2 disposed on the opposite side of the first object field with respect to the optical axis outside the optical axis in the object surface along a second projection beam path RP2 into a second effective image field IF2 located outside the optical axis in the image surface.

[0076] The projection lens includes a number of lens elements (for example, between 15 and 25 lens elements), and further includes exactly two concave mirrors CM1, CM1, with exactly one concave mirror in each of the projection beam paths, including a number of optical elements.

[0077] Most of the lens elements (more than 50%, in particular, 60% or more, or 70% or more, or 80% or more) are arranged along the first part OA1 of the optical axis OA, and these first parts extend coaxially and perpendicular to each other with respect to the object plane OS and the image plane IS. The concave mirrors CM1, CM2 are arranged on both sides of the first part OA1, defining the second part OA2 of the optical axis, and the second part OA2 of the optical axis, together with the first part, defines an axial plane (lying in the plane of the drawing in FIG. 9). The concave mirrors in this example are arranged coaxially with each other on both sides of the first part, and the second part OA2 of the optical axis is perpendicular to the first part OA1, thereby creating an intersecting shape.

[0078] The optical elements are arranged and formed symmetrically with respect to a symmetry plane SYM that extends perpendicular to the axial plane (here, the plane of the drawing) through the first part OA1. For each of the concave mirrors, within the assigned projection beam path, there is a first deflection unit ULE1 for deflecting the radiation coming from the object plane OS towards the concave mirror, and a second deflection unit ULE2 for deflecting the radiation coming from the concave mirror in the direction of the image plane IS. The deflection units ULE1, ULE2 are each arranged on the side of the symmetry plane SYM facing the assigned concave mirrors CM1 and CM2 respectively.

[0079] Exactly two real intermediate images (generally referred to as IMI) of the assigned effective object field are generated in each of the projection beam paths RP1, RP2 between the object plane and the image plane, becoming the exact IMI1-1, IMI2-1 in the first projection beam path, and IMI1-2 and IMI2-2 in the second projection beam path (see FIG. 10).

[0080] Constructed only of transparent optical elements, thus the first lens part OP1, which is refractive (dioptric), is designed such that the pattern in each of the illuminated effective object fields is imaged onto the first intermediate images IMI1-1, IMI1-2 of the respective projection beam paths and is slightly reduced (for example, an imaging scale in the range of about 1.85:1 to about 1.75:1).

[0081] The second refractive-reflective lens portion OP2 images the first intermediate image of the projection beam path onto respective second intermediate images IMI2 without substantially changing their size. The second lens portion OP2 includes, for each of the projection beam paths, separate concave mirrors CM1, CM2, and three upstream double-pass lens elements. In the second lens portion, the projection beam path separates and travels along separate optical paths through separate partial lenses, after which the projection beam paths are recombined at a common lens element in the region of the second intermediate image IMI2. The second intermediate image IMI2 is located between two individual mirrors of ULE2, i.e., the projection beam paths are still separated at the second mirror of ULE2 and are only recombined thereafter.

[0082] The third refractive lens portion OP3 is designed to image the second intermediate images IMI2-1, IMI2-2 scaled down onto the image plane IS.

[0083] All lens elements of the first lens portion OP1 and all lens elements of the third lens portion OP3, and thus all lens elements on the first portion OA1 of the optical axis, are common to both projection beam paths. The footprint of the projection beam path on the surface of an individual lens element, i.e., the surface area on which the radiation impinges, is symmetric with respect to the symmetry plane SYM. Therefore, any possible lens heating effects, particularly in the near-field lens elements, are substantially symmetric with respect to the symmetry plane, and thus any possible corrections are simplified.

[0084] In each of the projection beam paths, pupil surfaces or pupil planes P1, P2, P3 are arranged where the chief ray CR of the optical imaging intersects the optical axis OA between the object plane and the first intermediate image, between the first intermediate image and the second intermediate image, and between the second intermediate image and the image plane. The aperture stop of this system may be arranged in the region of the pupil surface P3 of the third lens portion OP3. The pupil surface P2 within the refractive-reflective second lens portion OP2 is positioned immediately adjacent to the respective concave mirror CM.

[0085] To assist with color correction, a negative group NG having at least one diffractive negative lens is disposed in each of two projection beam paths near associated concave mirrors CM1, CM2 within a region close to the pupil. The "region close to the pupil" is a region where the marginal ray height (MRH) of imaging is higher than the chief ray height (CRH). The marginal ray height within the region of the negative group can be at least twice the chief ray height.

[0086] To provide context, the total refractive power, field curvature, and contribution to chromatic aberration of lens elements having positive refractive power and lens elements having negative refractive power in an optical system act in opposite directions, but a concave mirror has a positive refractive power in exactly the same way as a positive lens element and has an inverse effect on field curvature compared to the positive lens element. In addition, a concave mirror does not introduce chromatic aberration. Therefore, a catadioptric system portion having a concave mirror close to the pupil and an adjacent negative lens (Schupmann achromatization) is a means well-suited to achromatize a projection lens. A double-pass positive lens PL can be disposed between each deflection unit and the negative group, which can also be omitted in other exemplary embodiments (see Table 3).

[0087] An exceptional technical feature relates to the design of the deflection units ULE1, ULE2. These are not designed as plane mirrors or deflection mirrors that reflect alone. Instead, the first deflection unit ULE1 and the second deflection unit ULE2 each have a substantially flat first reflecting surface RF1 and a directly subsequent substantially flat second reflecting surface RF2. The reflecting surfaces are tilted by different tilt angles about an axis of tilt orthogonal to the first and second portions with respect to a plane of symmetry SYM. The first reflecting surface RF1 is used to deflect radiation coming from the object surface OS to the second reflecting surface RF2, and the second reflecting surface is used to deflect radiation coming from the first reflecting surface RF1 in the direction of the image surface.

[0088] In each projection beam path, the first reflecting surface RF1 is a reflecting surface that receives the beam coming from the last lens element of the first lens portion OP1 and reflects it in the direction of the immediately following second reflecting surface RF2. Then, the reflecting surface RF2 reflects the beam within the second lens portion OP2 towards the associated concave mirror CM. After being reflected by the concave mirror and passing twice through three upstream lens elements, the beam then enters the second deflection unit ULE2. The first reflecting surface RF1 of the second deflection unit ULE2 deflects the beam towards the second reflecting surface RF2, and the second reflecting surface RF2 reflects it in the direction of the first lens element of the third lens portion OP3.

[0089] When the tilt angle KW of the reflecting surface is defined as the angle enclosed by the surface normal NOR of the reflecting surface and the incident-side optical axis, the tilt angles of the first reflecting surfaces on the side of the first lens portion are each 67.5°. For the immediately following second reflecting surface in each beam path, the tilt angle is then slightly 22.5°, that is, it corresponds to the complementary angle of the first tilt angle whose sum is 90°. The same applies to the second deflection unit ULE2, that is, the one that deflects the beam coming from each concave mirror CM in the direction of the third lens portion OP3, where the second part OA2 of the optical axis is regarded as the incident-side optical axis.

[0090] Therefore, a 90° deflection with respect to the incident-side optical axis is achieved in exactly two immediately consecutive steps, namely, the first x degrees and the second 90 - x degrees. The two associated reflecting surfaces of the deflection unit are positioned on the same side of the symmetry plane SYM, exactly on the side where the associated concave mirror CM is positioned.

[0091] Both reflecting surfaces RF1, RF2 of the deflection unit ULE are each positioned in the optical vicinity of the first intermediate image IMI1 of the associated projection beam path. As a result, the footprint of the beam on the reflecting surface appears as a rectangle with more or less rounded corners, positioned at a distance from the optical axis but close to the optical axis. More specifically, the first intermediate image is between the two reflecting surfaces RF1 and RF2, and in this way, both reflecting surfaces are close to the intermediate image. At the imaging scale of the first lens portion OP1 with a maximum very small magnification or a slight reduction, the size of the intermediate image is not larger or only slightly larger than the size of the generated effective object field of view OF. As a result, a mirror surface with compact dimensions is sufficient to reflect the entire beam to the downstream optical element without vignetting. This applies in particular to the reflection from the first reflecting surface RF1 to the second reflecting surface RF2, which can also be made very compact in size because this reflection is still in the optical vicinity of the first intermediate image, in particular in a region where the sub-aperture ratio SAR is less than 0.3 in absolute value. The SAR is preferably between 0.2 and 0.3.

[0092] For the purposes of explanation, the optical vicinity or optical distance of an optical surface with respect to a reference surface (e.g., the field surface or the pupil surface) is described in this application by the so-called sub-aperture ratio SAR. The sub-aperture ratio SAR of an optical surface is defined as follows for the purposes of this application. SAR = sign(CRH)·(MRH / (|CRH| + |MRH|)) Here, MRH represents the marginal ray height, CRH represents the chief ray height, the sign function sign(x) represents the sign of x, and by convention, sign(0) = 1. The chief ray height is the ray height of the chief ray of the field point of the object field of view having the maximum field height with respect to the absolute value. It should be understood that the ray height is here signed. The marginal ray height is the ray height of the ray with the maximum aperture starting from the intersection of the optical axis and the object plane. This field point does not need to contribute to the transfer of the pattern arranged on the object plane, in particular in the off-axis image field.

[0093] The sub-aperture ratio is a signed variable that is a measure in the vicinity of the field of view or the pupil of a plane within the beam path. By definition, the sub-aperture ratio is normalized to a value between -1 and +1, the sub-aperture ratio is zero at each field plane, and the sub-aperture ratio jumps from -1 to +1 or vice versa at the pupil plane. Thus, a sub-aperture ratio with an absolute value of 1 identifies the pupil plane.

[0094] Thus, the near field plane has a sub-aperture ratio close to 0, while the near pupil plane has a sub-aperture ratio close to 1 with respect to the absolute value. The sign of the sub-aperture ratio indicates the position of the front or rear surface of the reference plane.

[0095] The reflecting surface can be designed as a nominal plane, i.e., it defines a mathematical plane except for manufacturing tolerances. It is also possible to design individual reflecting surfaces or all reflecting surfaces with a defined deviation from the plane, so that the reflecting surface can function as a correcting surface for aberrations such as distortion.

[0096] In the schematic example of FIG. 9, the reflecting surfaces are each manufactured as individual mirrors and housed in separate mounts. The example of FIG. 10 shows in each case that two of the deflecting mirrors or reflecting surfaces may be designed in combination as a triangular prism. These triangular prisms can be mounted together at the center of the star-shaped cross-section of the deflection unit. Alternatively, all the mirrors required for deflection may be combined and designed as a composite prism with a star-shaped side surface. The prism can consist of, for example, a plurality of individual prisms that are joined or bonded to each other.

[0097] To show the advantages provided by such a double reflection deflection unit in comparison with the prior art, FIGS. 11A-11C show three folding situations for comparison. FIG. 11A shows a "classical" fold in a refractive reflective projection lens with a single concave mirror CM. A first deflection mirror FS1 that reflects radiation coming from the object surface OS to the concave mirror CM is on the side facing away from the concave mirror of a portion of the optical axis that is perpendicular to the object surface and the image surface. The same applies to a second deflection mirror that deflects the light rays coming from the concave mirror to a third lens portion.

[0098] When two fields of view can be used simultaneously, the folding mirrors for each field of view will block the respective beam paths of the opposite field of view. Therefore, it is only possible to image a single field of view.

[0099] To enable the (simultaneous) imaging of two fields of view, the deflection unit should be positioned on the side of the optical axis facing the associated horizontal arm or the concave mirror. FIG. 11B shows an attempt at an embodiment with a conventional planar mirror. In the folding variant in FIG. 11B, the folding mirror FS reflects in the other direction in each case, i.e., the concave mirror is positioned on the opposite side of the effective object field of view. In this case, the folding mirror is arranged in its own beam path. As a result, there is no functioning system.

[0100] The difference between FIG. 11B and FIG. 11C is that the light rays in FIG. 11C are positioned on the left side (object side) of the optical axis of the horizontal arm (OA2) in the first deflection unit and, after reflection at the concave mirror, are positioned on the right side (image side) of OA2 in the second deflection unit. In FIG. 11B, this is the reverse. As a result, the second deflection unit has to be on the left side of the first deflection mirror (i.e., closer to the object surface) and thus within the beam path of the object - first deflection mirror.

[0101] FIG. 11C shows, for comparison purposes, the folding by means of two deflection mirrors for each 90° deflection according to an exemplary embodiment of the invention, i.e., the folding by means of a two-stage reflection deflection unit. It can be seen that the separation of the beam paths leading to the individual concave mirrors can be achieved in this way.

[0102] The following text explains some practical advantages of the dual-field projection lens. An increase in throughput (the components exposed per unit time) can be achieved by the possibility of simultaneously exposing two off-axis fields. This is achieved in the projection lens, in particular, by the fact that two catadioptric partial lenses, i.e., two horizontal arms each containing a concave mirror, are included in the second lens part. The lens part containing the concave mirror is symmetric with respect to the plane of symmetry. The axis of symmetry is a virtual line extending through the optical axis OA and parallel to the wide side of the effective image field.

[0103] The field distance ABBF of the two effective image fields in the scanning direction (y-direction) is ideally such that the sum of the slit width (A*) of one field and the distance between the two fields exactly corresponds to the width of the stepper field (see the situation in FIG. 2 showing the object field).

[0104] The dual field can be used in the scanning for double exposure or with the help of the step-and-scan method.

[0105] In the first case, two identical structures must be arranged adjacent to each other on the reticle or mask. During scanning, a substrate such as a wafer is continuously exposed by a first field having a first structure and then by a second field having a second identical structure. During normal scanning, the far peripheral regions of the wafer are exposed only once. This can be prevented if the scanning is started with some overflow. It is conceivable that the second image field is blocked in the overflow region.

[0106] In the second case, two different structures can also be placed adjacent to each other on the reticle, and these can be combined to form a structure twice as large. Subsequently, the necessary step-and-scan operations will scan two fields of view and then jump to the next double field of view in a stepping step.

[0107] The following figures are used to illustrate some of the special features of the scan. Figure 12A shows a schematic top view of a wafer provided with a number of directly adjacent rectangular exposure units DIE (dies) having current standard dimensions of 26 mm in width and 32 mm in length. The enlarged section of Figure 12A and Figure 12B show a typical conventional scan operation. The wafer moves in a serpentine manner under the projection lens or image field of view or scan slit used for exposure. There are two different states. In the scan phase shown by the solid lines in Figures 12A and 12B, the substrate and the mask or the wafer and the reticle move at a uniform and matched speed (depending on the imaging scale of the projection lens), and the dies are exposed. After each scan operation, a direction change is performed, which is marked by the dashed lines in Figures 12A and 12B. As a result, while the wafer is moving, the movement of the reticle is stopped. This movement includes a deceleration phase, a movement perpendicular to the scan direction, and then an acceleration in the opposite direction. There is no exposure during the direction change, so this phase is non-productive. Figures 12A and 12B schematically show the time-sequence sequence of the two phases.

[0108] For comparison, Figure 13B shows the different phases of the scan operation with the aid of a projection exposure apparatus having a double field of view and two rigidly coupled scan slits having the shape schematically shown in Figure 13A. It is immediately apparent that the scan phase now extends over the length of two directly consecutive dies, such that two dies can be exposed simultaneously during the scan phase. Compared to the scan phase, the non-productive direction change performs only half of the classical scan operation in the sense that in the classical operation the direction change is performed after the scan of a die, while in the case of the double field of view the direction change is performed only after the scan of two dies.

[0109] To enable this type of scanning, two scanning slits or effective image fields in an exemplary embodiment are arranged according to FIG. 13A.

[0110] The scanning operation by double exposure corresponds to the scanning operation of a single field with respect to reticle and wafer movement. In any case, one die is exposed first, and the adjacent die is exposed second. The difference from the scanning operation of a single field is that in the upper and lower peripheries of the wafer, the illumination of one of the two fields must be switched off so as not to be exposed beyond the periphery of the wafer.

[0111] The previous example shows that the two-step folding in the two deflection units of each projection beam path enables the use of a double field. There are other potential uses and advantages beyond a single fold. One example is the avoidance of so-called "image flipping" by a refractive-reflective projection lens using a single concave mirror and two intermediate images.

[0112] Such a projection lens provides advantages, for example, with respect to the correction of chromatic aberration, but has the disadvantage that "image flipping" is generated during imaging. This means that features described in a right-handed coordinate system on the reticle are described in a left-handed coordinate system on the image plane. This inconvenient characteristic results from the fact that the left and right images change between the object plane and the image plane at each intermediate image and each reflection. If the sum of the number of intermediate images and the number of reflections is odd, the result is image flipping. If this sum is even, image flipping can be avoided. This is explained below using a comparison between a classical projection lens according to FIG. 11A and a projection lens PO-X according to FIG. 14.

[0113] FIG. 14 shows a lens element cross section through a catadioptric projection lens PO-X that images an effective object field of view in an object plane positioned outside the optical axis onto an off-axis effective image field of view in an image plane. Two real intermediate images IMI1-X and IMI2-X are created between the object plane and the image plane. The projection lens has a single concave mirror with an upstream negative group to assist in correcting chromatic aberration. A first deflection unit ULE1-X directs radiation coming from the object plane in the direction of the concave mirror. A second deflection unit ULE2-X directs the radiation reflected by the concave mirror in the direction of the image plane. The second deflection unit is formed by a simple plane mirror and causes a single reflection, while the first deflection unit ULE-X is designed as a two-stage reflection deflection unit. The first deflection unit ULE-X has a first reflecting surface RF1-X that deflects radiation coming from the object in the direction of a second immediately downstream reflecting surface RF2-X. The first deflection unit ULE-X then reflects the radiation in the direction of the concave mirror. The two reflecting surfaces can be arranged on separate individual mirrors, and preferably, the two reflecting surfaces are formed on a common carrier element to fix their orientation relative to each other. There are two intermediate images and a total of four reflections between the object plane and the image plane, so the sum of the intermediate images and reflections is even. Thus, image flipping (see FIG. 11A) present in this type of conventional system is avoided. Alternatively, the first deflection unit can be single-stage and the second deflection unit can be two-stage. As in classical systems, the deflection mirrors are each arranged in the optical vicinity of the associated intermediate image, i.e., in the near-field region.

[0114] The use of a two-stage reflection deflection unit of the type described in this application is not limited to exemplary embodiments. It is also possible to use such a deflection unit in a projection lens that creates only one intermediate image between the object plane and the image plane or that generates a direct image without an intermediate image. The two-stage reflection deflection unit may be arranged in the projection beam path behind an upstream plane mirror and / or in front of a downstream deflection mirror.

[0115] The following table summarizes the specifications of two exemplary embodiments. Tables 1 and 1A apply to the exemplary embodiment of FIG. 9 with NA = 0.3, and Tables 2 and 2A apply to an exemplary embodiment (not shown in the figures) with NA = 0.28 and no positive lens element in the double-pass beam path between the deflection unit and the concave mirror.

[0116] The table summarizes the specifications of each design in tabular form. The "Surface" column indicates the number of the refractive surface or the surface with different characteristics, the "Radius" column indicates the radius r (in mm) of the surface, the "Thickness" column indicates the distance d (in mm) of the surface from the subsequent surface, and the "Material" column indicates the material of the optical component. The columns "Index 1", "Index 2", and "Index 3" indicate the refractive indices of the material at wavelengths 365.5 nm (Index 1), 364.5 nm (Index 2), and 366.5 nm (Index 3). The "Semi-diameter" column indicates the available free radius or semi-free optical diameter (in mm) of the lens element or optical element. A radius r = 0 (in the "Radius" column) corresponds to a plane. Some of the optical surfaces are aspherical. The tables with the suffix "A" show the corresponding aspherical data, and the aspheres are calculated according to the following rules.

[0117]

Number

Number

[0118]

Table 1

[0119]

Table 2

[0120]

Table 3

[0121]

Table 4

Claims

1. An illumination system (ILL) for a microlithographic projection exposure apparatus for illuminating a pattern arranged in a region of an object plane (OS) of a downstream projection lens (PO) with illumination light created from light from a primary light source (LS), wherein the illumination system is designed as a dual-field illumination system for receiving a single light beam from the primary light source (LS) and creating two illumination beams (BS1, BS2) therefrom, with a first illumination beam (BS1) being guidable along a first illumination beam path to a first illumination field (ILF1) arranged outside the optical axis of the projection lens within an exit surface (ES) of the illumination system, and simultaneously, a second illumination beam (BS2) being guidable along a second illumination beam path to a second illumination field (ILF) arranged outside the optical axis within the exit surface, on the opposite side of the first illumination field (ILF1) with respect to the optical axis (AX), a refractive pupil shaping unit (PFU) for receiving light from the primary light source (LS) and generating a two-dimensional intensity distribution on a pupil shaping surface (PUP) of the illumination system, and a refractive field shaping system (FFS) optically downstream of the pupil shaping unit, including a homogenizing unit (HOM) for homogenizing the light received from the pupil shaping unit and splitting the illumination light into the first illumination beam (SB1) and the second illumination beam (SB2). An illumination system comprising the above.

2. The illumination system according to claim 1, characterized in that the homogenizing unit (HOM) includes an integrating rod configuration (ISA) having an incident integrating rod (IE) with an incident surface (EF1) and an exit surface (AF1), and further a first exit integrating rod (IA1) optically coupled to a first partial surface (TF1) of the exit surface (AF1) and a second exit integrating rod (IA2) optically coupled to a second partial surface (TF2) of the exit surface (AF1), wherein an exit surface (AF2-1) of the first exit integrating rod is assigned to the first illumination field (ILF1) and an exit surface (AF2-2) of the second exit integrating rod is assigned to the second illumination field (ILF2).

3. The incident integrator rod (IE) and the output integrator rods (IA1, IA2) each have a constant cross-sectional shape and cross-sectional size in the axial direction, and between the output surface of the incident integrator rod and each of the input surfaces of the output integrator rods, from a location close to the axis, a prism configuration (PA) for beam deflection from the location close to the axis to a location far from the axis, positioned at a distance from the optical axis (AX), is arranged. The lighting system according to claim 2, characterized in that.

4. The first output integrator rod (IA1) and the second output integrator rod (IA2) are formed as tapered integrators, and the cross-sectional size continuously decreases from the incident side to the output side. The lighting system according to claim 2 or 3, characterized in that.

5. The homogenizing unit (HOM) has a first grid configuration (RA1) with a first refractive grid element (RE1) for receiving light of the two-dimensional intensity distribution and generating a grid configuration of secondary light sources (SL1, SL2,...), and a second grid configuration downstream with a second refractive grid element (RE2) for receiving light from the secondary light sources (SL1, SL2) and at least partially overlapping the light from the secondary light sources at the output surface (RA2), Each first grid element (RE1) creates an optical channel, and each of the second grid elements (RE2) is assigned to two adjacent first grid elements (RE1) and is formed by a lens element having a first portion (AB1) positioned in a first optical channel and a second portion (AB2) positioned in a second optical channel, the portions having different surface shapes. The lighting system according to claim 1, characterized in that.

6. The lighting system according to claim 5, characterized in that first grid elements (RE1) adjacent in one direction are alternately assigned to the first illumination field (ILF1) and the second illumination field (ILF2).

7. At least one surface of the lens element of the second grid configuration (RA2) is curved aspherically, preferably, the incident surface and the output surface are curved aspherically. The lighting system according to claim 5 or 6, characterized in that.

8. The illumination system according to claim 5, 6 or 7, characterized in that the flexion line extends between the first part (AB1) and the second part (AB2) on at least one surface of the lens element of the second grid configuration (RA2).

9. A projection exposure apparatus for exposing a radiation-sensitive substrate arranged in the region of the image plane of a projection lens with at least one image of a pattern of a mask arranged in the region of the object plane of the projection lens, An illumination system (ILL) for shaping illumination radiation, which receives light from a single light source, illuminates a first effective object field arranged outside the optical axis of the projection lens in the object plane, and simultaneously illuminates a second effective object field arranged on the opposite side of the first object field outside the optical axis in the object plane. A projection lens configured to image the first effective image field along a first projection beam path onto a first effective image field located outside the optical axis in the image plane, and simultaneously image the second effective object field into a second effective image field located outside the optical axis in the image plane along a second projection beam path. A device for holding the mask between the illumination system and the projection lens such that the pattern is arranged in the region of the object plane of the projection lens. A device for holding the substrate such that the radiation-sensitive surface of the substrate is arranged in the region of the image plane of the projection lens. In a projection exposure apparatus, comprising A projection exposure apparatus, characterized in that the illumination system according to any one of claims 1 to 8 is formed.

10. The projection lens includes a lens element and a concave mirror (CM), and is a refractive reflective projection lens having a number of optical elements arranged between the object plane (OS) and the image plane (IS) along the optical axis (OA). Preferably, Each of the projection beam paths includes a first deflection unit (ULE1) for deflecting radiation coming from the object plane (OS) to the concave mirror, and a second deflection unit (ULE2) for deflecting radiation coming from the concave mirror in the direction of the image plane (IS). The optical element forms a first lens portion (OP1) for imaging each of the effective object fields (OF1, OF2) of the object surface onto a first real intermediate image (IMI1), a second lens portion (OP2) for generating a second real intermediate image (IMI2) by radiation coming from the first lens portion (OP1), and a third lens portion (OP3) for imaging the second real intermediate image (IMI2) into the image plane (IS). In a region of a pupil surface (P2) positioned between the first intermediate image and the second intermediate image, the concave mirror (CM) of the projection beam path is arranged, the first deflection unit (FM1) is arranged in the optical vicinity of the first intermediate image (IMI1), and the second deflection unit (FM2) is arranged in the optical vicinity of the second intermediate image (IMI2). and / or In the projection beam path, at least one two-stage reflection deflection unit including a first reflection surface (RF1) and a second reflection surface (RF2) immediately following is arranged. The first reflection surface (RF1) is arranged to deflect the radiation coming from the object surface (OS) to the second reflection surface (RF2), and the second reflection surface (RF2) is arranged to deflect the radiation coming from the first reflection surface in the direction of the image plane (IS). The projection exposure apparatus according to claim 9, characterized in that.

11. A projection exposure method for exposing a radiation-sensitive substrate with at least one image of a mask pattern, comprising: preparing the pattern between an illumination system of a projection exposure apparatus and the projection lens such that the pattern is arranged in a region of an object surface of the projection lens; holding the substrate such that a radiation-sensitive surface of the substrate is arranged in a region of an image plane of the projection lens that is optically conjugate with the object surface; illuminating two illumination regions of the mask with illumination radiation from a single primary light source supplied by the illumination system. Here, two illumination beams (BS1, BS2) are generated, and the first illumination beam (BS1) is guided along the first illumination beam path to a first illumination field (ILF1) disposed outside the optical axis of the projection lens within the exit surface (ES) of the illumination system, and at the same time, the second illumination beam (BS2) is guided along the second illumination beam path to a second illumination field (ILF2) positioned outside the optical axis within the exit surface, on the opposite side of the first illumination field (ILF1) with respect to the optical axis (AX). Projecting, with the aid of the projection lens, the portion of the pattern positioned in the illumination field onto the assigned image field on the substrate comprising A projection exposure method in which the illumination system according to any one of claims 1 to 8 and / or the projection exposure apparatus according to claim 9 or 10 is used.

Images