Reflective refraction projection objective lens, projection illumination system, and projection illumination method

Abstract

A reflective refractive projection objective for reproducing a pattern arranged on the object plane (OS) of the projection objective on the image plane of the projection objective parallel to the object plane includes a plurality of optical elements, the plurality of optical elements including a lens and a concave mirror (CM), and is arranged between the object plane (OS) and the image plane (IS) along the optical axis (OA). The projection objective (PO) reproduces a first effective object field of view (OF1) arranged outside the optical axis in the object plane along a first projection beam path to a first effective image field of view (IF1) located outside the optical axis in the image plane, and at the same time, a second effective object field of view (OF2) arranged outside the optical axis in the object plane and on the opposite side of the first object field of view related to the first optical axis is reproduced along a second projection beam path (RP2) to a second effective image field of view (IF2) located outside the optical axis in the image plane, and is designed as a dual-field projection objective. Each of the projection beam paths has 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 elements form a first objective lens portion (OP1) for reproducing each of the effective object fields of view (OF1, OF2) of the object plane to a first real intermediate image (IMI1), a second objective lens portion (OP2) for generating a second real intermediate image (IMI2) by the radiation coming from the first objective lens portion (OP1), and a third objective lens portion (OP3) for reproducing the second real intermediate image (IMI2) to the image plane (IS). The concave mirror (CM) of the projection beam path is arranged in the region of the pupil surface (P2) located between the first intermediate image and the second intermediate image. 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).

Description

Technical Field

[0001] The following disclosure is based on German Patent Application No. 10 2022 205 272.2 with filing reference number, 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 a reflective refractive projection lens for imaging a pattern arranged on the object plane of a projection lens onto an image plane of the projection lens parallel to the object plane. The present invention further relates to a projection exposure apparatus having such a projection lens, and a projection exposure method that can be carried out with the aid of the projection lens.

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 a pattern of the structure to be imaged, for example, a line pattern of a layer of a semiconductor device, is used. The pattern is arranged in the region of the object area of the projection lens between the illumination system and the projection lens in the projection exposure apparatus, and is illuminated in the region of the effective object field by the illumination radiation provided by the illumination system. The radiation modified by the pattern travels through the projection lens as a projection beam, 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) sensitive to the projection radiation.

[0004] When selecting an appropriate projection exposure apparatus and method for the 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 mid-critical or 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. The optical elements share a common linear optical axis. The object field of view and the image field of view can be centered with respect to the optical axis (on-axis field of view). Thus, in certain cases, full-field exposure in the stepper mode (step and repeat) is possible, and as a result, a high throughput rate (complete exposure per unit time) is promoted.

[0007] Here, a projection exposure apparatus (so-called i-line system) for an operating wavelength of 365.5 nm ± 2 nm has been used for a long time. It uses the i-line of a mercury lamp, and its natural bandwidth is limited to a narrower usable bandwidth Δλ, for example, approximately 2 nm, by a filter or other means. During projection, ultraviolet light in a relatively wide wavelength range is used with this type of light source, and as a result, the projection lens must perform a relatively strong correction of chromatic aberration in order to ensure imaging with low aberration at the desired resolution even using such broadband projection light.

[0008] It has already been suggested to use a refractive-reflective projection lens (see German Patent Application Publication No. 10 2006 022 958) for this wavelength range, that is, a projection lens including both a refractive optical element having refractive power, that is, a lens element, and a reflective element having refractive power, that is, a curved mirror. Generally, at least one concave mirror is included.

[0009] When a reflective refractive projection lens is constructed without a polarization selective physical beam splitter and has no pupil masking and no beam aperture vignetting, the off-axis field of view must be used in a rotationally symmetric configuration of the system, i.e., a configuration where the effective object field of view and the effective image field of view are off the optical axis.

[0010] The size of the off-axis field of view is limited by shape requirements and performance. In particular, it is not possible to achieve a full field of view (as in the case of a stepper), and therefore, the exposure is performed in a scanning mode. This requires more technology to achieve high throughput.

[0011] Most conventional projection exposure apparatuses are designed to image a single effective object field of view onto a single effective image field of view. For example, there is also a technique of simultaneously using two beam paths to increase throughput.

[0012] U.S. Patent No. 8,634,060 describes a projection exposure apparatus that can simultaneously expose 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.

[0013] 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.

[0014] 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, and as a result, two wafers can be exposed simultaneously. A patent application filed simultaneously (published as U.S. Patent Application Publication No. 2010 / 0053583) discloses a corresponding illumination system that can simultaneously illuminate two separate illumination fields positioned at a distance from each other on the same mask. A diffractive optical element or prism is provided to split the beam coming from the light source. An array of lens elements of a fly-eye lens is provided for homogenization of the illumination radiation.

[0015] A projection exposure apparatus having two projection beam paths is described, for example, in U.S. Patent Specification No. 8,384,875 using a schematic example. Two illumination systems are provided for illuminating the mask, and they 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 reworking the system is not disclosed. SUMMARY OF THE INVENTION

[0016] Against this background, it is an object of the present invention to provide a practically feasible concept of a refractive reflective dual-field projection lens, a projection exposure apparatus comprising the same, and a projection exposure method that can be carried out using the same.

[0017] This object is achieved according to the present invention by a refractive reflective projection lens having the features of claim 1, a projection exposure apparatus having the features of claim 13, and a projection exposure method having the features of claim 15. Advantageous developments are defined in the dependent claims. The expressions of all claims are incorporated by reference into the content of this specification.

[0018] According to the representation of the present invention, there is provided a catadioptric projection lens including a number of optical elements arranged along the optical axis between an object plane and an image plane parallel to the object plane. The projection lens is designed as a dual-field projection lens, and a first effective object field arranged outside the optical axis within the object plane is imaged into a first effective image field located outside the optical axis within the image plane along a first projection beam path, and at the same time, a second effective object field arranged outside the optical axis within the object plane and on the opposite side of the first object field with respect to the optical axis is imaged into a second effective image field located outside the optical axis within the image plane along a second projection beam path.

[0019] Each of the projection beam paths includes a first deflection unit for deflecting the radiation coming from the object plane to a concave mirror and a second deflection unit for deflecting the radiation coming from the concave mirror in the direction of the image plane. Therefore, the projection lens has at least two concave mirrors, preferably exactly two concave mirrors, i.e., a single concave mirror per projection beam path.

[0020] A special feature of this concept is that the optical elements form a first lens portion for imaging each of the effective object fields of the object plane into a first real intermediate image, a second lens portion for generating a second real intermediate image by the radiation coming from the first lens portion, and a third lens portion for imaging the second real intermediate image into the image plane, and the concave mirrors of the projection beam paths are arranged in the region of the pupil surface located between the first intermediate image and the second intermediate image, the first deflection unit is arranged optically close to the first intermediate image, and the second deflection unit is arranged optically close to the second intermediate image.

[0021] This design method enables the construction of a projection lens that functions with two simultaneously usable fields of view of a practically usable size with an overall compact structural mass. In principle, the dimensional design of the deflection unit is complicated by the boundary conditions. If the deflection surface can be designed relatively large, a deflection with a larger field of view without vignetting can be realized relatively easily, but usually, it results in a considerably large structural size. When the structural size is kept small, the reflecting surface becomes too small with respect to the size of the field of view to be projected, and the risk of vignetting may increase. By providing two intermediate images, conditions are created for projecting or imaging a practically usable field of view size from the object plane to the image plane using a relatively small mirror surface.

[0022] The two projection radiation paths can be used selectively or as an alternative to each other. In particular, it is possible to use two off-axis effective object fields of view simultaneously. This means that it is possible to expose an area of the substrate having twice the size per unit time compared to a conventional projection lens having only one off-axis object field of view of the same size. This enables a higher throughput than a conventional off-axis projection lens.

[0023] Preferably, the optical element includes a number of lens elements and two concave mirrors. According to one deployment, the plurality of lens elements are arranged along a first portion of the optical axis. The first portion is coaxial with each other and perpendicular to the object plane and the image plane. The concave mirrors are arranged on both sides of the first portion and define a second portion of the optical axis that is laterally directed with respect to the first portion. Thus, the optical axis is folded. Overall, the projection lens has rotational symmetry with respect to the folded optical axis. The first portion and the second portion are in a common plane, herein called the axial plane. The optical element is arranged and formed symmetrically with respect to the symmetry plane. The symmetry plane extends perpendicularly to the axial plane through the first portion. For each of the concave mirrors, a first deflection unit for deflecting radiation coming from the object plane towards the concave mirror and a second deflection unit for deflecting radiation coming from the concave mirror in the direction of the image plane are provided. The deflection units are each arranged on the side of the symmetry plane facing the assigned concave mirror.

[0024] The concave mirrors can be arranged coaxially with respect to each other such that the second portion is directed perpendicular to the first portion. Then, the projection lens has an overall cross-shaped configuration of the optical element. The two concave mirrors are coaxially on opposite sides of each other on different sides of the symmetry plane.

[0025] It is also possible for the second portion to be directed laterally with respect to the first portion or the symmetry plane at an angle deviating from 90°, which may be useful, for example, from the perspective of the installation space.

[0026] A special feature is that the deflection units are each arranged on the side of the symmetry plane facing the associated concave mirror. This enables the use of two projection beam paths in the projection lens, each leading from an off-axis effective object field of view optically conjugate to an effective image field of view. The two off-axis effective object fields of view can be arranged symmetrically with respect to the symmetry plane, at a distance from the symmetry plane on opposite sides, and the same applies to the associated effective image fields of view.

[0027] In the prior art of reflective refraction projection lenses, there are many examples where one or more concave mirrors are combined in the projection beam path between the object plane and the image plane so that an image without masking and without vignetting is possible. For the folding, generally, a planar mirror (folding mirror) inclined by 45° with respect to the incident side portion of the optical axis is used to achieve a 90° fold by a single reflection. The conventional planar mirror is arranged on the side of the optical axis facing away from the concave mirror.

[0028] According to one development, this conventional approach should be abandoned. Instead, the first deflection unit and the second deflection unit each have a first reflecting surface and a second reflecting surface immediately behind it, and their reflecting surfaces are inclined at different inclination angles with respect to the symmetry plane about an inclination axis extending at right angles to the first and second portions, the first reflecting surface being arranged to deflect the radiation coming from the object plane to the second reflecting surface, and the second reflecting surface being arranged to deflect the radiation coming from the first reflecting surface in the direction of the image plane. Therefore, the deflection unit is designed not as a 45° planar mirror but as a two-stage reflection deflection unit, and the two-stage reflection deflection unit, in any case, results in a change in the beam angle of the incident radiation by reflection in two immediately consecutive stages. In this context, "immediately" means, in particular, that no other optical element is present between the first reflecting surface and the second reflecting surface.

[0029] The deflection unit is preferably arranged, in any case, on the side of the symmetry plane facing the associated concave mirror, i.e., on the same side as the associated concave mirror.

[0030] The first and second reflecting surfaces of the deflection unit can together achieve the 90° folding angle required for the cross-shaped structure of the projection lens. However, the folding angle may also deviate from 90°.

[0031] The inclination angles of the first reflecting surface and the second reflecting surface are preferably adapted to each other such that each beam incident on the first reflecting surface parallel to the incident-side optical axis is deflected by the same angle at the first reflecting surface and the second reflecting surface. For example, a deflection of 45° can be provided, resulting in a total deflection of 90°. The inclination angle is here defined as the angle enclosed by the surface normal of the reflecting surface and the incident-side portion of the optical axis. Thus, for example, the first inclination angle can be 67.5° and the second inclination angle can be 22.5°. However, in some cases, it may be useful to tilt the two reflecting surfaces so as to deflect the deflected beam to different extents.

[0032] The reflecting surfaces can each be formed as separate individual mirrors, which can be individually and precisely adjusted relative to each other as required. It is also possible to form two or more reflecting surfaces of the deflection unit on a common carrier element. For example, the carrier element can be composed of four triangular prisms. These triangular prisms can be mounted together at the center of the star-shaped cross-section of the deflection unit. Alternatively, all the reflecting surfaces required for deflection can be combined and designed as a composite prism with star-shaped sides. The composite prism can, for example, be composed of a plurality of individual prisms, which are joined or crimped to each other.

[0033] The first reflecting surface and the second reflecting surface can be flat, i.e., formed as a plane. Within the range of manufacturing tolerances, the deviation from the plane can be in the range of about j percent or one-thousandth of the operating wavelength. However, for example, larger deviations in the surface shape from the plane may also be provided, especially to achieve a specific effect on the shape of the wavefront.

[0034] The intermediate image is located on or near the field plane of a projection lens that is optically conjugate to the object plane and the image plane. The first deflection unit is arranged optically close to the first field plane, and the second deflection unit is arranged optically close to the second field plane that is optically conjugate to the first field plane. With the near-field configuration, it is possible to keep the reflecting surface used for deflection relatively small, and as a result, it is possible to achieve a compact structural size of the deflection unit. Preferably, the first deflection unit and the second deflection unit are arranged in a region where the sub-aperture ratio SAR is less than 0.3 in absolute value. In particular, the intermediate image can be arranged between two individual mirrors of the deflection unit.

[0035] The first lens portion should not have an enlarging effect or a strong enlarging effect, if possible, such that the size of the first intermediate image does not exceed or greatly exceed the size of the effective object field. According to a certain development, the first lens portion has a first imaging scale factor β 1 to which the condition 0.5 ≦ |β 1 | ≦ 2.0 applies. When these conditions are met, it is possible to achieve transporting or carrying a sufficiently large field size that can be actually used without vignetting by the relatively small mirror surface of the deflection unit. If the lower limit is greatly undershot, and as a result, the first lens portion has too strong a reducing effect, a relatively high aperture angle may occur in the region of the deflection unit, and as a result, deflection may not be achievable with a sufficiently small mirror surface, or deflection may only be achievable with a very small field size. On the other hand, if the upper limit is exceeded, and as a result, the first lens portion has too strong an enlarging effect, the aperture angle in the deflection unit will decrease, but the deflection unit must have relatively large dimensions so as to be able to completely reflect a relatively large intermediate image. The first lens portion can be a 1:1 system, and usually, the magnification should not exceed 1.2 times. Therefore, the absolute value of the imaging scale factor β 1 of the first lens portion can particularly be in the range of 1.2 or less. Then, it is possible to realize two-stage deflection, especially in a particularly compact installation space.

[0036] According to another formulation, the projection lens preferably has a reduction imaging scale, and the first lens part generates a reduction of at most half.

[0037] The projection lens is designed as a scanner system. During scanning, only a part of the object field of view is imaged by the projection lens at any given time. Therefore, a scanning movement in which adjacent portions of the reticle are continuously transferred to the substrate is required to perform a single exposure step.

[0038] To transfer the complete pattern of a 6-inch reticle in a single exposure step by scanning, the effective object field of view should have a width of 104 mm. According to one development, the projection lens is designed with an object field radius OBH of at least 107 mm. The projection lens can be designed such that each of the effective object fields has a size of 104 mm × 56 mm and can be positioned at a distance of 38 mm from the optical axis.

[0039] Some embodiments are characterized in that the image-side numerical aperture is less than 0.5, and the numerical aperture is preferably in the range between 0.2 and 0.4.

[0040] The present invention also relates to a projection exposure method 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, wherein the projection lens according to the present invention is used in this method.

[0041] The present invention also relates to 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, the projection exposure apparatus comprising a primary radiation source for emitting primary radiation, an illumination system for receiving the primary radiation and generating illumination radiation directed onto the mask, and a projection lens for generating at least one image of the pattern within the region of the image plane of the projection lens, the projection lens being configured according to the present invention.

[0042] The projection lens is used to scan two adjacent dies simultaneously. Double exposure can also be performed.

[0043] The projection exposure apparatus preferably includes a central control device for controlling the functions of the projection exposure apparatus, and the control device in at least one operating mode is configured to operate the illumination system and the projection lens such that two adjacent dies are scanned simultaneously by a double field of view. In another operating mode, double exposure can be performed.

[0044] The two-stage reflection deflection unit of the type described in the present application can also be advantageously used, regardless of the claimed invention, for example, further in a single-field reflection-refraction projection lens, i.e., a reflection-refraction projection lens having only one effective object field of view. Accordingly, the present disclosure also relates to a reflection-refraction projection lens for imaging a pattern arranged on the object plane of the projection lens onto an image plane of the projection lens parallel to the object plane, the reflection-refraction projection lens including a plurality of lens elements and a plurality of optical elements including a concave mirror, and for imaging an effective object field of view arranged outside the optical axis in the object plane along the projection beam path to an effective image field of view located outside the optical axis in the image plane, including a plurality of optical elements arranged between the object plane and the image plane along the optical axis, and at least one two-stage reflection deflection unit having a first reflecting surface and a second reflecting surface immediately behind it is arranged in the projection beam path, the first reflecting surface being arranged to deflect radiation coming from the object plane to the second reflecting surface, and the second reflecting surface being arranged to deflect radiation coming from the first reflecting surface in the direction of the image plane.

[0045] In particular, in the projection beam path, a first deflection unit for deflecting radiation coming from the object plane to the concave mirror and a second deflection unit for deflecting radiation coming from the concave mirror in the direction of the image plane are arranged, and the first deflection unit and / or the second deflection unit may be formed as a two-stage reflection deflection unit.

[0046] Both the first deflection unit and the second deflection unit can each be a two-stage reflection deflection unit. It is also possible that only one of the deflection units is a two-stage reflection deflection unit and the other deflection unit is a planar mirror, and either the first deflection unit or the second deflection unit can be a two-stage reflection deflection unit.

[0047] Further advantages and aspects of the present invention will become apparent from the claims and from the description of the exemplary embodiments of the invention described below with reference to the figures.

Brief Description of the Drawings

[0048]

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DETAILED DESCRIPTION OF THE INVENTION

[0049] In the following description of the preferred embodiments, the term "optical axis" represents a sequence of straight lines or straight line portions passing through the centers of curvature of optical elements. The optical axis is folded by a folding mirror (deflection mirror) or other reflective surfaces. In this example, the object is a mask (reticle) having an integrated circuit pattern, which may also be related to different patterns of, for example, gratings. In this example, the image is projected onto a wafer provided with a photoresist layer, and the wafer functions as a substrate. Other substrates, such as substrates for liquid crystal display elements or optical grating substrates, are also possible.

[0050] FIG. 1 shows an example of a microlithography projection exposure apparatus PBA, which can be used for the manufacture of semiconductor devices and other microstructured components and operates with light or electromagnetic radiation from the ultraviolet (UV) range 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 with 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).

[0051] The projection exposure apparatus is an i-line system that uses only light from the i-line, i.e., UV light near the central operating wavelength of approximately 365.5 nm. The natural full bandwidth of the i-line is limited to a narrower usable bandwidth Δλ, e.g., approximately 2 nm, with the help of a filter or by another method.

[0052] At its exit surface ES, the illumination system ILL connected downstream of the light source LS forms, from the light from this single primary light source, in each case, two large, clearly delimited, and substantially homogeneously illuminated illumination fields ILF1, ILF2 at a beam angle that meets the telecentricity requirements of the projection lens PO arranged downstream in the optical path.

[0053] The optical element that receives the 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.

[0054] The illumination system ILL has a device 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.

[0055] 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 is located on the object plane OS of the projection lens PO, which is also called the reticle plane OS here.

[0056] 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 for synchronously moving the wafer in the scanning direction (y direction) perpendicular to the optical axis OA with the reticle M. The device WS, also called the "wafer stage", and the device RS, also called the "reticle stage", are integral parts of a scanner device controlled by a scanning control device integrated into the central control device CU of the projection exposure apparatus PBA in this embodiment.

[0057] Figure 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 and ILF2 with light from a light source at the exit plane (reticle plane, object plane of the projection lens). These illumination fields are each rectangular and can be sharply or gently delimited and are illuminated substantially homogeneously. Each of the illumination fields defines the effective object field actually used in projection exposure, and as a result, the first effective object field OF1 and the second effective object field OF2 are positioned on the reticle plane. 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 the width B measured perpendicular to the y direction (in the x direction or cross-scanning direction) * >A * and have. For example, the aspect ratio AR = B * / A * can be, for example, 2, 2.5, 3, 5, 10, or 15.

[0058] In the case of the illustration, the effective rectangular fields (i.e., those actually used for imaging) each have 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 results 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). *

[0059] In a rotationally symmetric system, a 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 meet 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 the 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.

[0060] The effective image fields of view IF1, IF2 in the image plane IS that are optically conjugate to the effective object fields of view OF1, OF2 have the same shape and the same aspect ratio between height A and width B as the associated effective object fields of view, but the absolute field size is reduced by the imaging scale β of the projection lens in a reduction projection lens (|β| < 1), i.e., A = |β|A * and B = |β|B * is.

[0061] In either case, the distance ABF (field distance) measured in the scanning direction (y-direction) between the edges of the effective object fields of view 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 of view IF1, IF2 is the length of the "die" that should 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.

[0062] Figure 3 shows a schematic diagram 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 with a wavelength of approximately 355 nm.

[0063] The pupil shaping unit PFU follows the primary light source. The pupil shaping unit PFU is constructed solely 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 referred to as a secondary light source or illumination pupil. Since the essential characteristics of the illumination radiation are influenced or directed by this local intensity distribution, this pupil surface is also referred to as the pupil shaping surface PUP.

[0064] The pupil shaping unit PFU can be variably adjustable, so that depending on the control of the optical components of the pupil shaping unit, different local illumination intensity distributions within the circular illumination pupil can be set, for example, a circular illumination spot centered on the optical axis AX, a dipole illumination, or a conventional illumination setting using quadrupole illumination.

[0065] The refractive 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 coming 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 make them incident on the exit surface at a distance from each other. The 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.

[0066] The integrator rod configuration ISA includes an incident integrator rod IE having a flat incident surface EF1, a flat exit surface EF2 parallel thereto, and four flat side surfaces forming a rectangular cross-section. The incident integrator rod is made of a material transparent to the illumination light. The light is mixed within the incident integrator rod by multiple total internal reflections at the uncoated or optionally coated outer surfaces (side surfaces) of the integrator rod, and thus exits from the exit surface AF1 in a homogenized, at least partially homogenized form. The incident 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.

[0067] The integrator rod configuration further includes a first exit integrator rod IA1 and a second exit integrator rod IA2, each having an incident 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 incident integrator rod IE.

[0068] The exit integrator rods IA1, IA2 are arranged diametrically opposite at a distance from the optical axis AX of the illumination system. The first exit integrator rod IA1 is optically coupled to a first partial surface TF1 of the exit surface of the incident integrator rod such that the light exiting through the first partial surface TF1 enters only the first exit integrator rod IA1. The same applies to the opposite side, and the light from the partial surface TF2 enters the second exit integrator rod IA2.

[0069] Between the incident integrator rod IE and the two output integrator rods IA1, IA2, two prisms P1 and P2 of the 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 incident surface that receives the radiation emerging from this partial surface. The flat exit surface has the same size and is located with an intermediate gap immediately in front of the incident surface of the first output integrator rod IA1. The prism further has two flat side surfaces, which are oriented at an angle of 45° with respect to the incident surface and the exit surface, and each has a reflective coating. They can be made reflective, for example, by applying an aluminum layer or a dielectric coating.

[0070] The two deflections at the mirror surface 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 exit surface AF1 of the incident integrator rod and guides the light from a position close to the axis to a place far away from the axis.

[0071] Using this configuration, the light entering the incident integrator rod IE is evenly divided into substantially equal parts across the exit surface AF2-1 of the first output integrator rod and the exit surface AF2-2 of the second output integrator rod, and at the same time, it is mixed by multiple total reflections in both the incident integrator rod and the output integrator rods.

[0072] In the immediate vicinity of the exit part of the first output integrator rod IA1, there is an intermediate field surface 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 infinitely. A corresponding second field stop BL2 is arranged at the exit part of the second output integrator rod.

[0073] 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 a subsequent projection lens. Thus, a first illumination beam generates a first illumination field ILF1 on one side of the optical axis AX, while a second illumination field ILF2 is illuminated on the opposite side at a distance from the optical axis with the aid of a second illumination beam SB2.

[0074] Figures 5A through 5C show some variations of this basic concept. The variation of Figure 5A differs from the example of 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 an upstream or downstream element via a gap.

[0075] Figure 5B shows that additional integrator rods ISW1, ISW2 can also in each case be integrated between an incident integrator rod IE and two exit integrator rods IA1, IA2.

[0076] 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.

[0077] In the exemplary embodiment of FIG. 6, there are no intermediate prisms and / or other optical elements between the input 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 input surfaces EF1, EF2 substantially corresponds to half of the area of the output surface AF1 of the input integrator rod IE, so that the light emerging from the assigned partial surface is in each case 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 input 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 perhaps be required at the entrance of the input integrator rod, and the rod illumination is adapted so that no violation of the etendue conservation occurs.

[0078] 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. The significant difference from the previous exemplary embodiment lies in the configuration and operation of the homogenization 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.

[0079] 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 configurations such as secondary light sources SL1, SL2, etc. are 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 split 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.

[0080] 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 the image surface of the illumination system ILL. This overlap results in the homogenization of the light intensity at the exit surface.

[0081] 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.

[0082] 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. Then, the intermediate field surface is imaged onto the exit surface of the illumination system as in the above example.

[0083] 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.

[0084] 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 lens elements 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.

[0085] 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 viewing 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, which propagates on the opposite side with respect to the optical axis AX with respect to the first illumination beam.

[0086] 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.

[0087] Accordingly, the characteristics of this hybrid concept are 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 portion, and preferably, at least one of its sides is aspherical, and each size corresponds to the size of the associated field honeycomb.

[0088] 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 (image) the pattern of a mask arranged on the object plane OS onto an image plane IS oriented parallel to the object plane, for example, at a scale of 1:4.

[0089] 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.

[0090] The projection lens is designed as a dual-field projection lens. It images (image) a first effective object field OF1 arranged outside the optical axis OA in the object plane OS along a first projection beam path RP1 into a first effective image field IF1 located outside the optical axis OA in the image plane IS, and at the same time, images (image) a second effective object field OF2 arranged on the opposite side of the first object field with respect to the optical axis outside the optical axis in the object plane along a second projection beam path RP2 into a second effective image field IF2 located outside the optical axis in the image plane.

[0091] 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.

[0092] More than 50% of the lens elements, in particular more than 60%, or more than 70%, or more than 80%, are arranged along a first portion OA1 of the optical axis OA, and these first portions 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 portion OA1 and define a second portion OA2 of the optical axis, and the second portion OA2 of the optical axis, together with the first portion, 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 portion, and the second portion OA2 of the optical axis is perpendicular to the first portion OA1, thereby creating an intersecting shape.

[0093] 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 portion 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.

[0094] Exactly two real intermediate images (commonly called 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, resulting in 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).

[0095] Constructed only of transparent optical elements, thus the first lens portion OP1, which is refractive (dioptric), is designed such that the pattern in each of the illuminated effective object fields is imaged (image) 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).

[0096] The second refractive-reflective lens portion OP2 images the first intermediate image of the projection beam path to respective second intermediate images IMI2 without substantially changing the 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, and then 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 between the 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.

[0097] The third refractive lens portion OP3 is designed to image the second intermediate images IMI2-1, IMI2-2 scaled to the image plane IS.

[0098] 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 respective 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.

[0099] In each of the projection beam paths, pupil surfaces or pupil planes P1, P2, P3 where the chief ray CR of the optical imaging intersects the optical axis OA are disposed 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 disposed 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.

[0100] 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. Here, the "region close to the pupil" is a region where the marginal ray height (MRH) of the 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.

[0101] To provide background, the total refractive power, image field curvature, and contributions 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 positive refractive power in exactly the same way as a positive lens element and has an inverse effect on image field curvature compared to a 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 element PL can be disposed between each deflection unit and the negative group, which can also be omitted in other exemplary embodiments (see Table 3).

[0102] The exceptional technical features relate 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 each 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.

[0103] 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 subsequent second reflecting surface RF2. The reflecting surface RF2 then reflects the beam within the second lens portion OP2 to 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 to 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.

[0104] 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 subsequent second reflecting surfaces 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 unit 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.

[0105] Therefore, a 90° deflection with respect to the incident-side optical axis is achieved in exactly two immediately consecutive steps, specifically by the first x degrees and the second 90 - x degrees. The two mutually related reflecting surfaces of the deflection unit are positioned on the same side of the symmetry plane SYM, specifically on the side where the associated concave mirror CM is positioned.

[0106] Both reflecting surfaces RF1, RF2 of the deflection unit ULE are each positioned optically close to the first intermediate image IMI1 of the associated projection beam path, such that the footprint of the beam on the reflecting surface appears as a rectangle with more or less rounded corners, positioned at a distance from, 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 greater than, or only slightly greater than, the size of the generated effective object field of view OF, such that 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 reflection can also be made very compact in size, because this reflection is still optically close to 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.

[0107] For the purposes of explanation, the optical proximity 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 the present 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 the present 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 is to 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.

[0108] The sub-aperture ratio is a signed variable that is a measure near the field of view or near 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.

[0109] 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 in terms of absolute value. The sign of the sub-aperture ratio indicates the position of the front or rear surface of the reference plane.

[0110] 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.

[0111] 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 deflection 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 can 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.

[0112] To show the advantages provided by such a double reflection deflection unit as compared to 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.

[0113] When two fields of view can be used simultaneously, the folding mirrors of 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.

[0114] To enable imaging of two fields of view (simultaneously), the deflection unit should be positioned on the side of the optical axis facing the relevant 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.

[0115] The difference between FIGS. 11B and 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 by 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.

[0116] FIG. 11C shows, for comparison purposes, the folding by means of two deflection mirrors for every 90° deflection according to an exemplary embodiment of the present 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.

[0117] The following text describes 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 parts containing the concave mirrors are each symmetric with respect to a 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.

[0118] 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).

[0119] The dual field can be used in the scanning for double exposure or with the help of the step-and-scan method.

[0120] In the first case, two identical structures have to 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.

[0121] In the second case, two different structures can also be arranged adjacent to each other on the reticle, and these can be combined to form a structure twice as large. Next, 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.

[0122] 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 DIEs (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 not productive. Figures 12A and 12B schematically show the time-sequence sequence of the two phases.

[0123] 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, so 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 the die, while in the case of the double field of view the direction change is performed only after the scan of the two dies.

[0124] To enable this type of scanning, two scanning slits or effective image fields in an exemplary embodiment are arranged according to FIG. 13A.

[0125] The scanning operation by double exposure corresponds to the scanning operation of a single field with respect to reticle and wafer movement. In either case, one die is first exposed and the adjacent die is exposed a second time. 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.

[0126] 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.

[0127] Such a projection lens provides advantages, for example, with respect to the correction of chromatic aberration, but has the drawback 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.

[0128] FIG. 14 shows a cross-sectional view of a lens element passing through a refractive reflective 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 positioned 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 then 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, the image flip (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 optically close to the associated intermediate image, i.e., in the near-field region.

[0129] 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 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.

[0130] 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.

[0131] 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.

[0132]

Number

Number

[0133]

Table 1-1

Table 1-2

[0134]

Table 2

[0135]

Table 3-1

Table 3-2

[0136]

Table 4

Claims

1. A refractive-reflective projection lens for imaging a pattern arranged on an object plane (OS) of the projection lens onto an image plane of the projection lens parallel to the object plane, the projection lens comprising: a lens element and a concave mirror (CM), and a number of optical elements arranged between the object plane (OS) and the image plane (IS) along an optical axis (OA); comprising the projection lens (PO) is designed as a dual-field projection lens for imaging a first effective object field (OF1) arranged outside the optical axis in the object plane along a first projection beam path (RP1) onto an effective image field (IF1) located outside the optical axis in the image plane, and simultaneously imaging a second effective object field (OF2) arranged outside the optical axis in the object plane and on the opposite side of the first object field with respect to the optical axis along a second projection beam path (RP2) into a second effective image field (IF2) located outside the optical axis in the image plane; each of the projection beam paths includes a first deflection unit (ULE1) for deflecting radiation coming from the object plane (OS) towards 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); in the refractive-reflective projection lens the optical elements form a first lens portion (OP1) for imaging each of the effective object fields (OF1, OF2) of the object plane 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); a region of a pupil surface (P2) positioned between the first intermediate image and the second intermediate image is provided with the concave mirror (CM) of the projection beam path, the first deflection unit (FM1) is arranged optically close to the first intermediate image (IMI1), and the second deflection unit (FM2) is arranged optically close to the second intermediate image (IMI2). A refractive-reflective projection lens characterized by this.

2. The lens is arranged along a first portion (OA1) of the optical axis that extends 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 portion, define a second portion (OA2) of the optical axis, and the second portion (OA2) of the optical axis, together with the first portion, defines an axial plane. The optical element is arranged and formed symmetrically with respect to a symmetry plane (SYM) that extends perpendicular to the axial plane through the first portion (OA1). The reflection refraction projection lens according to claim 1, characterized in that the deflection units (ULE1, ULE1) are each arranged on the side of the symmetry plane (SYM) facing the assigned concave mirror.

3. The reflection refraction projection lens according to claim 2, characterized in that the concave mirrors are coaxially arranged with each other on both sides of the first portion and define a second portion directed at a right angle to the first portion.

4. The first deflection unit (ULE1) and the second deflection unit (ULE2) each have a first reflection surface (RF1) and a second reflection surface (RF2) immediately following. The reflection surfaces are tilted at different tilt angles with respect to the symmetry plane about an inclination axis extending perpendicular to the first and second portions. 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 is arranged to deflect the radiation coming from the first reflection surface in the direction of the image surface (IS). The reflection refraction projection lens according to any one of claims 1 to 3, characterized in that.

5. The reflection refraction projection lens according to claim 4, characterized in that the tilt angle of the first reflection surface and the tilt angle of the second reflection surface are preferably adapted to each other such that each beam incident parallel to the incident-side optical axis on the first reflection surface is deflected by the same angle at the first reflection surface and the second reflection surface.

6. The first deflection unit (ULE1) and the second deflection unit (ULE2) are arranged in a region where the sub-aperture ratio SAR is less than 0.3 in absolute value. The reflection refraction projection lens according to any one of claims 1 to 5, characterized in that.

7. The first lens portion has a first imaging scale factor β to which the condition 0.5 ≤ |β| ≤ 2.0 is applied 1 and the condition |β| ≤ 1.2 is preferably applied, and / or the projection lens has a reduced imaging scale factor, and the first lens portion generates a reduction of up to half, a refractive projection lens according to any one of claims 1 to 6, characterized in that. 1 having a condition |β| 1 ≤ 1.2 is preferably applied, and / or the projection lens has a reduced imaging scale factor, and the first lens portion generates a reduction of up to half, a refractive projection lens according to any one of claims 1 to 6, characterized in that.

8. The reflection refraction projection lens according to any one of claims 1 to 7, characterized in that the image-side numerical aperture is less than 0.5, and the numerical aperture is preferably in the range between 0.2 and 0.

4.

9. In the projection beam path between the effective object field of view (OF) within the object surface (OS) and the effective image field of view (IF) within the image surface, the sum of reflections and intermediate images is an even number, characterized in that the refractive-reflective projection lens according to any one of claims 1 to 8.

10. A refractive-reflective projection lens, which is the projection lens for imaging (image) a pattern arranged on the object surface (OS) of the projection lens onto the image surface of the projection lens parallel to the object surface, Comprising a plurality of lens elements and a number of optical elements including a concave mirror (CM), The first effective object field of view (OF1) arranged outside the optical axis within the object surface is imaged (image) along the first projection beam path (RP1) onto the effective image field of view (IF1) located outside the optical axis within the image surface For this purpose, a number of optical elements arranged between the object surface (OS) and the image surface (IS) along the optical axis (OA) Including, 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, and the first reflection surface (RF1) is arranged to deflect radiation coming from the object surface (OS) to the second reflection surface (RF2), and the second reflection surface (RF2) is arranged to deflect radiation coming from the first reflection surface in the direction of the image surface (IS), the refractive-reflective projection lens.

11. In the projection beam path, a first deflection unit (ULE1) for deflecting radiation coming from the object surface (OS) to the concave mirror and a second deflection unit (ULE2) for deflecting the radiation coming from the concave mirror in the direction of the image surface (IS) are arranged, and the first deflection unit (ULE1) and / or the second deflection unit (ULE2) is a two-stage reflection deflection unit, characterized in that the refractive-reflective projection lens according to claim 10.

12. One of the deflection units is a two-stage reflection deflection unit, and the other deflection unit is a plane mirror, characterized in that the refractive-reflective projection lens according to claim 10.

13. A projection exposure apparatus for exposing a radiation-sensitive substrate arranged in a region of the image surface of a projection lens with at least one image of a pattern of a mask arranged in a region of the object surface of the projection lens, An illumination system (ILL) for receiving light from a single light source, illuminating a first effective object field of view disposed outside the optical axis of the projection lens within the object plane, and simultaneously forming illumination radiation for illuminating a second effective object field of view disposed on the opposite side of the first object field of view outside the optical axis within the object plane. A catadioptric projection lens configured to image the first effective image field of view along a first projection beam path to a first effective image field of view located outside the optical axis within the image plane, and simultaneously image the second effective object field of view along a second projection beam path to within a second effective image field of view located outside the optical axis within the image plane. A device for holding the mask between the illumination system and the projection lens such that the pattern is disposed 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 disposed in the region of the image plane of the projection lens. Including, in the projection exposure apparatus. The projection exposure apparatus, characterized in that the projection lens (PO) is embodied as described in any one of claims 1 to 12.

14. The illumination system is A refractive pupil shaping unit (PFU) for receiving light from a primary light source (LS) and generating a two-dimensional intensity distribution on the 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 a first illumination beam (SB1) and a second illumination beam (SB2). Including The homogenizing unit (HOM) preferably has an integrator rod configuration or a first grid configuration (RA1) and a second grid configuration (RA1). The integrator rod configuration (ISA) includes an incident integrator rod (IE) having an incident surface (EF1) and an exit surface (AF1), a first exit integrator rod (IA1) optically coupled to a first partial surface (TF1) of the exit surface (AF1), and a second exit integrator rod (IA2) optically coupled to a second partial surface (TF2) of the exit surface (AF1). The exit surface (AF2-1) of the first exit integrator rod is assigned to a first illumination field (ILF1), and the exit surface (AF2-2) of the second exit integrator rod is assigned to a second illumination field (ILF2). The first grid configuration (RA1) includes a first refractive grid element (RE1) for receiving the light of the two-dimensional intensity distribution and generating a grid configuration of secondary light sources (SL1, SL2,...). The downstream second grid configuration (RA2) includes a second refractive grid element (RE2) for receiving the light from the secondary light sources (SL1, SL2) and at least partially overlapping the light from the secondary light sources at the exit surface. 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 the first optical channel and a second portion (AB2) positioned in a second optical channel, the portions having different surface shapes. The projection exposure apparatus according to claim 13, characterized in that.

15. A projection exposure method for exposing a radiation-sensitive substrate with at least one image of a mask pattern, comprising: Providing 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 plane 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 to the object plane; 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) arranged outside the optical axis of the projection lens within the exit surface (ES) of the illumination system. 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 projection lens according to any one of claims 1 to 12 and / or the projection exposure apparatus according to any one of claims 13 and 14 is used.

Images