Reflective and refractive 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 disclosures are based on the German patent application filed on 25 May 2022, file reference number 10 2022 205 272.2. The disclosures of that patent application constitute the contents of this application by reference.

[0002] The present invention relates to a reflective / refractive projection lens for imaging a pattern placed on the object surface of a projection lens onto the image plane of the projection lens parallel to the object surface. The present invention further relates to a projection exposure apparatus having such a projection lens, and a projection exposure method that can be performed with the help of the projection lens. [Background technology]

[0003] Today, microlithography projection exposure methods are primarily used to create semiconductor devices and other microstructured components. In this case, a mask (reticle) is used to support or create a pattern of the structure to be imaged, such as a line pattern of layers in a semiconductor device. The pattern is placed in 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 area of ​​the effective object field by 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 area of ​​the effective image field, which is optically conjugate to the effective object field. The substrate typically 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, particularly based on the typical structural size of the structure to be created within the exposed substrate, must be taken into consideration.

[0005] Projection lithography systems with high NA projection lenses typically operate at wavelengths within the deep ultraviolet (DUV) range, for example, around 193 nm, and are used to create relatively fine critical structures.

[0006] In contrast, to produce intermediate critical or noncritical layers with typical structural sizes significantly exceeding 150 nm, projection lithography systems designed for operating wavelengths exceeding 200 nm are traditionally 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 image field of view can be centered with respect to the optical axis (on-axial field of view). Therefore, in certain cases, exposure of the entire field of view in stepper mode (step and repeat) is possible, resulting in a high throughput rate (complete exposure per unit time).

[0007] Here, projection lithography systems (so-called i-line systems) for operating wavelengths of 365.5 nm ± 2 nm have been used for a long time. They use i-line mercury lamps, and their natural bandwidth is limited to a narrower usable bandwidth Δλ, e.g., approximately 2 nm, by filters or other means. During projection, ultraviolet light with a relatively wide wavelength range is used in this type of light source, and as a result, the projection lens must be subjected to relatively strong correction for chromatic aberration in order to ensure low-aberration imaging with the desired resolution, even with such broadband projection light.

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

[0009] If a reflective or refractive projection lens is constructed without a polarization-selective physical beam splitter and does not have pupil occlusion and beam aperture eclipse, the off-axis field of view must be used in a rotationally symmetric configuration of the system, i.e., in a configuration where the effective object field of view and the effective image field of view are outside 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 exposure is performed in scanning mode. This requires more technology to achieve high throughput.

[0011] Most conventional projection lithography systems are designed to image a single effective object field into a single effective image field. For example, some techniques use two beam paths simultaneously to increase throughput.

[0012] U.S. Patent No. 8,634,060 describes a projection lithography apparatus capable of simultaneously exposing two masks and two wafers. Light from a single light source is alternately delivered 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 operates with two separate masks and two separate illumination systems, wherein the projection beam paths within the projection lens are fused via a triangular prism.

[0014] U.S. Patent Application Publication 2010 / 0053738 (corresponding to U.S. Patent No. 8,705,170) describes a projection lens that uses a single mask and, with the help of a deflection mirror, splits the projection beam path within the projection lens so that two separate image-side lens portions are formed to produce two image fields, thereby enabling the simultaneous exposure of two wafers. A concurrently filed patent application (published as U.S. Patent Application Publication 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 homogenizing the illumination radiation.

[0015] A projection exposure apparatus with two projection beam paths is described, for example, in U.S. Patent Specification 8,384,875 using a schematic example. Two illumination systems are provided for illuminating the mask, which can be constructed separately from each other or integrated into a common illumination system (Figure 12). A schematic example of a reflective / refracting projection lens is also provided. Specification data for modifying the system is not disclosed. [Overview of the project]

[0016] Against this backdrop, the object of the present invention is to provide a practically feasible concept of a reflective / refractive dual-field projection lens, a projection exposure apparatus equipped therewith, and a projection exposure method that can be performed using the same.

[0017] This objective is achieved, according to the expression of the present invention, by a reflective / refracting 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 provided in the dependent claims. All claims are incorporated herein by reference.

[0018] According to the expression of the present invention, a reflecting and refraction projection lens is provided, comprising 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 is configured to image a first effective object field located outside the optical axis in the object plane into a first effective image field located outside the optical axis in the image plane, along a first projection beam path; and simultaneously, to image a second effective object field located outside the optical axis in the object plane and on the opposite side of the first object field with respect to the optical axis into a second effective image field located outside the optical axis in the image plane, along a second projection beam path.

[0019] Each projection beam path includes a first deflection unit for deflecting radiation coming from the object plane to a concave mirror, and a second deflection unit for deflecting radiation coming from the concave mirror towards the image plane. Thus, the projection lens has at least two concave mirrors, preferably exactly two, i.e., one 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 field of view of the object plane into a first real intermediate image, a second lens portion for generating a second real intermediate image by radiation coming from the first lens portion, and a third lens portion for imaging the second real intermediate image in the image plane; and a concave mirror in the projection beam path is positioned in a region of the pupil surface located between the first intermediate image and the second intermediate image, a first deflection unit is positioned optically close to the first intermediate image, and a second deflection unit is positioned optically close to the second intermediate image.

[0021] This design approach allows for the construction of a projection lens that functions with two simultaneously usable fields of view of a practical size, while maintaining an overall compact structural mass. In principle, the dimensional design of the deflection unit is complicated by boundary conditions. If the deflection surface can be designed to be relatively large, deflection without vignetting over larger fields of view can be achieved relatively easily, but this usually results in a considerable structural size. If the structural size is kept small, the reflective surface may become too small relative to the size of the field of view to be projected, increasing the risk of vignetting. By providing two intermediate images, conditions are created for projecting or imaging a practically usable field of view 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 substitutes for each other. In particular, it is possible to use two off-axis effective object fields simultaneously. This means that it is possible to expose twice the area of ​​the substrate per unit time compared to conventional projection lenses that have only one off-axis object field of the same size. This enables higher throughput than conventional off-axis projection lenses.

[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, here 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 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 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 opposite 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 extending from an off-axis effective object field optically conjugate to an effective image field. The two off-axis effective object fields 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.

[0027] Prior art for reflective and refractive projection lenses includes numerous examples in which the optical axis is folded back one or more times by 90° increments to combine one or more concave mirrors in the projection beam path between the object plane and the image plane, enabling an image without occlusion and vignetting. For folding, a planar mirror (folding mirror) tilted by 45° with respect to the incident portion of the optical axis is generally used to achieve 90° folding with a single reflection. Conventional planar mirrors are positioned on the side of the optical axis that faces away from the concave mirror.

[0028] According to one development, this conventional method should be abandoned. Instead, the first and second deflection units each have a first reflecting surface and a second reflecting surface immediately following it, and these reflecting surfaces are tilted at different angles of inclination with respect to the plane of symmetry around an inclination axis extending perpendicular to the first and second parts, with the first reflecting surface positioned to deflect radiation coming from the object plane to the second reflecting surface, and the second reflecting surface positioned to deflect radiation coming from the first reflecting surface toward the image plane. Thus, the deflection units are designed as two-stage reflecting deflection units rather than as 45° plane mirrors, and in either case, the two-stage reflecting deflection units result in a change in the beam angle of the incident radiation through reflection in two immediately consecutive stages. In this context, "immediately" specifically means that there are no other optical elements between the first and second reflecting surfaces.

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

[0030] The first and second reflective surfaces of the deflection unit together can 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 and second reflecting surfaces are preferably matched to each other such that each beam incident on the first reflecting surface parallel to the incident optical axis is deflected by the same angle at both the first and second reflecting surfaces. For example, a 45° deflection can be provided, resulting in an overall deflection of 90°. The inclination angle is defined here as the angle enclosed by the surface normal of the reflecting surface with the incident 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 inclin the two reflecting surfaces to deflect the deflected beam to different degrees.

[0032] Each reflective surface can be formed on a separate individual mirror, which can be individually and precisely adjusted relative to one another as needed. It is also possible to form two or more reflective surfaces of a deflection unit on a common carrier element. For example, the carrier element can consist of four triangular prisms. These triangular prisms can be mounted together in the center of the star-shaped cross-section of the deflection unit. Alternatively, all the reflective surfaces required for deflection can be combined and designed as a composite prism with star-shaped sides. A composite prism can, for example, consist of multiple individual prisms that are joined or crimped together.

[0033] The first and second reflective surfaces can be flat, i.e., formed as planes. Within manufacturing tolerances, the deviation from the plane can be in the range of a few percent or a few thousandths of the operating wavelength. However, a larger deviation of the surface shape from the plane may be introduced, for example, to achieve a specific effect on the wavefront shape.

[0034] The intermediate image is located in or near the field of view of the projection lens, which is optically conjugate to the object plane and the image plane. The first deflection unit is positioned optically close to the first field of view, and the second deflection unit is positioned optically close to the second field of view, which is optically conjugate to the first field of view. The near-field configuration allows, among other things, to keep the reflective surface used for deflection relatively small, and as a result, a compact structural size of the deflection unit is also possible. Preferably, the first and second deflection units are positioned in a region where the sub-aperture ratio SAR is less than 0.3 in absolute value. In particular, the intermediate image can be positioned between the two individual mirrors of the deflection unit.

[0035] The first lens portion should, if possible, not have a magnifying effect, or a strong magnifying effect, so that the size of the first intermediate image does not exceed or significantly exceed the size of the effective object field of view. According to one development, the first lens portion has a first imaging scale β1 to which the condition 0.5 ≤ |β1| ≤ 2.0 applies. When these conditions are met, it is possible to achieve the ability to transport or carry a sufficiently large field of view that is actually usable, completely and therefore without aperture vignetting by the relatively small mirror surface of the deflection unit. If it falls significantly below the lower limit, 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 cannot be achieved with a sufficiently small mirror surface, or deflection can only be achieved with a very small field of view. On the other hand, if it exceeds the upper limit, and as a result the first lens portion has too strong a magnifying effect, the aperture angle in the deflection unit will decrease, but the deflection unit must have relatively large dimensions so that it can completely reflect the relatively large intermediate image. The first lens portion can be a 1:1 system, and the magnification should not exceed 1.2x under normal circumstances. Therefore, the absolute value of the imaging scale β1 of the first lens portion can be in the range of 1.2 or less. Subsequently, two-stage deflection can be achieved, especially in compact installation spaces.

[0036] According to another formulation, the projection lens preferably has a reduction imaging scale, and the first lens portion produces a reduction of up to half.

[0037] The projection lens is designed as part of a scanner system. During scanning, only a portion of the object's field of view is imaged by the projection lens at any given moment. 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 scanning exposure step, the effective 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 so that each effective field of view is 104 mm × 56 mm in size 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, positioned in the image plane region of a projection lens, with at least one image of a mask pattern positioned in the object plane region of the projection lens, wherein the projection lens according to the present invention is used.

[0041] The present invention also relates to a projection exposure apparatus for exposing a radiation-sensitive substrate, positioned in the image plane region of a projection lens, with at least one image of a pattern of a mask, positioned in the object plane region of the projection lens, wherein the projection exposure apparatus includes a primary radiation source for emitting primary radiation, an illumination system for receiving 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 image plane region of the projection lens, wherein the projection lens is 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 in at least one operating mode, the control device is configured to operate the illumination system and projection lens so that two adjacent dies are scanned simultaneously by dual field of view. In another operating mode, dual exposure can be performed.

[0044] The type of two-stage reflective deflection unit described in this application can also be advantageously used, for example, further in a single-field reflective refractive projection lens, i.e., a reflective refractive projection lens having only one effective object field of view, notwithstanding the claimed invention. Accordingly, the disclosure also relates to a reflective refractive projection lens for imaging a pattern placed on the object plane of a projection lens onto the image plane of a projection lens parallel to the object plane, wherein the reflective refractive projection lens comprises a plurality of optical elements including a plurality of lens elements and a concave mirror, and comprises a plurality of optical elements positioned between the object plane and the image plane along the optical axis to image an effective object field of view located outside the optical axis in the object plane, along the projection beam path, and includes at least one two-stage reflective deflection unit having a first reflective surface and a second reflective surface immediately following it, wherein the first reflective surface is positioned to deflect radiation coming from the object plane to the second reflective surface, and the second reflective surface is positioned to deflect radiation coming from the first reflective surface toward the image plane.

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

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

[0047] Further advantages and aspects of the present invention will become apparent from the claims and the description of exemplary embodiments of the invention, which are described below with reference to the drawings. [Brief explanation of the drawing]

[0048] [Figure 1] This is a schematic diagram of a projection exposure apparatus according to one exemplary embodiment. [Figure 2] This is a schematic top view of the object plane of a projection lens with two effective off-axis object fields. [Figure 3] This is a schematic diagram of a first exemplary embodiment of a dual-view illumination system having an integrator rod configuration. [Figure 4] Figure 3 is a diagram showing the integrator rod configuration in detail. [Figures 5A-5D] Figures 5A to 5D show variations of the integrator rod configuration in other exemplary embodiments. [Figure 6] This diagram shows an integrator rod configuration with two tapered outlet integrator rods. [Figure 7] This is a schematic diagram of an exemplary embodiment of a dual-view illumination system having grid elements within a homogenization unit. [Figure 8] This figure shows the homogenization unit in detail. [Figure 9] This is a schematic cross-sectional view of a meridional lens element of a projection lens according to a first exemplary embodiment. [Figure 10] This figure shows an enlarged cross-section of the deflection unit region in the projection lens shown in Figure 9. [Figure 11A-11C] Figures 11A to 11C show a comparison of three different folding situations. [Figure 12A] This figure shows a variation of single-field scanning. [Figure 12B] This figure shows a variation of single-field scanning. [Figure 13A] This figure shows a variation of dual-field scanning. [Figure 13B] This figure shows a variation of dual-field scanning. [Figure 14] This is a schematic meridional lens element cross-section of a reflective-refracting projection lens having two intermediate images, a concave mirror, a two-stage reflective-deflection unit, and a single-stage deflection unit. [Modes for carrying out the invention]

[0049] In the following description of preferred embodiments, the term “optical axis” refers to a straight line or a sequence of straight sections passing through the center of curvature of the optical element. The optical axis is reflected by a folding mirror (deflection mirror) or other reflective surface. In this example, the object is a mask (reticle) with an integrated circuit pattern, which may also relate to different patterns of a grating, for example. In this example, the image is projected onto a wafer having a photoresist layer, and the wafer serves as a substrate. Other substrates are also possible, for example, a substrate for a liquid crystal display or a substrate for an optical grating.

[0050] Figure 1 shows an example of a microlithography projection exposure system (PBA), which can be used for the fabrication 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 the submicrometer. A mercury lamp functions as the primary radiation source or light source (LS). The lamp emits a broad spectrum with relatively high intensity I emission lines in the wavelength range with centroid wavelengths of approximately 436 nm (visible light, blue, g line), approximately 405 nm (visible light, violet, h line), and approximately 365.5 nm (near ultraviolet, UV-A, i line).

[0051] The projection exposure system 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 of, for example, approximately 2 nm, with the help of filters or by other means.

[0052] At the exit surface ES, the illumination system ILL connected downstream of the light source LS generates two large, clearly separated, and substantially homogeneously illuminated illumination fields ILF1 and ILF2 from the light from this single primary light source, at beam angles that in either case meet the telecentricity requirements of the projection lens PO located downstream of the optical path.

[0053] The optical elements formed from the light emission received from the light source LS and directed toward the reticle M are part of the illumination system ILL of the projection exposure apparatus. The illumination system is a dual-field illumination system. Exemplary embodiments are described below in reference to Figures 3 to 8.

[0054] The ILL lighting system has a device for setting different lighting modes (lighting settings), and can, for example, switch between conventional on-axis lighting and off-axis lighting with different degrees of coherence σ.

[0055] Downstream of the illumination system, a device RS for holding and manipulating the mask M (reticle) is positioned such that the pattern placed 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, also called the reticle plane OS.

[0056] The substrate to be exposed is, in an exemplary case, a semiconductor wafer W, which is held by a device WS that includes a scanner drive unit to move the wafer in the scanning direction (y-direction) in synchronization with a 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 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 the 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 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 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 * For example, the aspect ratio AR = B * / A * can be, for example, 2, 2.5, 3, 5, 10, or 15.

[0058] In the exemplary case, 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). * )(= 188 mm).

[0059] In a rotationally symmetric system, the circle OBC centered on the optical axis OA encloses the effective object fields OF1 and OF2, touching their corners and determining the size of the object field circle. Within this circle, optical corrections must meet the specifications at all field points. This also applies to all field points within the effective object field. The larger the object field must be, the more complex the aberration correction becomes. In this case, the size of the circle is parameterized by the object field radius OBH or half the object field diameter OBH, 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 IF1 and IF2 on the image plane IS, which are optically conjugate to the effective object fields OF1 and OF2, have the same shape and the same aspect ratio between height A and width B as the related effective object fields, but the absolute field size is reduced by the imaging scale β of the projection lens ((│β│<1), i.e., A=|β|A * and B=|β|B * That is the case.

[0061] In either case, the ABF (field of view distance), measured in the scanning direction (y-direction) between the edges of the effective object field 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 IF1 and IF2 is the length of the “die” to be accurately exposed. This length is 33 mm according to current standards. In semiconductor and microsystems 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 focusing mirror, which reflects and focuses the light into the entrance aperture of the illumination system. An alternative (not shown) uses a laser as the light source, for example, a triple-frequency solid-state laser with a wavelength of approximately 355 nm.

[0063] The primary light source is followed by a pupil shaping unit (PFU), which is constructed solely of refractive optical components and designed to generate a defined local (two-dimensional) intensity distribution on the subsequent pupil surface (PUP) following the illumination system (ILL), and is sometimes referred to as a secondary light source or illumination pupil. This pupil surface is also called the pupil shaping surface (PUP) because the essential properties of the illumination radiation are influenced or directed by this local intensity distribution.

[0064] The pupil shaping unit (PFU) can be variably adjusted, and as a result, depending on the control of the optical components of the pupil shaping unit, different local illumination intensity distributions within the circularly illuminated pupil can be set, for example, conventional illumination settings using a circular illumination spot centered on the optical axis AX, bipolar illumination, or 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 illumination exit surface ES 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 its optical components are designed to further split the illumination light into a first illumination beam (BS1) and a second illumination beam (BS2), which are incident on the exit surface at a distance from each other. The field shaping system (FFS) includes an input coupling optical unit (EK), which collects the light coming from the pupil shaping surface and couples it to the incident surface EF1 of the integrator rod configuration (ISA). This is shown in detail 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 sides forming a rectangular cross-section. The incident integrator rod is made of a material transparent to the illumination light. Within the incident integrator rod, the light is mixed by numerous total internal reflections on the uncoated or optionally coated outer surface (sides) of the integrator rod, thereby homogenizing and exiting from the exit surface AF1 in a form that is at least partially homogenized. The incident integrator rod has a continuously rectangular cross-section and defines a longitudinal central axis 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 inlet surface EF2-1 and EF2-2, respectively, and an outlet surface AF2-1 and AF2-2, respectively. The two exit integrator rods IA1 and IA2 each have a rectangular cross-sectional shape and a cross-sectional area substantially half that of the inlet integrator rod IE.

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

[0069] Between the inlet integrator rod IE and the two outlet integrator rods IA1 and IA2, the two prisms P1 and P2 of the prism configuration PA are positioned. The first prism P1 has a rectangular, flat inlet surface that directly connects to the first partial surface TF1 with an intermediate gap LS and receives radiation emanating from this partial surface. The flat outlet surface is of the same size and is located immediately in front of the inlet surface of the first outlet integrator rod IA1 with an intermediate gap. The prism further has two flat sides, which are oriented at a 45° angle to the inlet and outlet surfaces, and each has a reflective coating. They can be made reflective by applying, for example, an aluminum layer or a dielectric coating.

[0070] The two deflections on the mirror surface of the prism with parallel offset deflect the light emanating from the sub-plane TF to a position further away from the optical axis. Thus, each prism optically connects one of the exit integrator rods IA1, IA2 to the assigned sub-planes TF1, TF1 of the exit surface AF1 of the entrance integrator rod, guiding light from a position close to the axis to a position far from the axis.

[0071] Using this configuration, the light entering the incident integrator rod IE is evenly divided over substantially equal portions across the exit surface AF2-1 of the first exit integrator rod and the exit surface AF2-2 of the second exit integrator rod, and simultaneously mixed by numerous total internal reflections in both the incident and exit integrator rods.

[0072] The intermediate field of view ZE of the illumination system is located very close to the output end of the first output integrator rod IA1. An adjustable field diaphragm BL1 is positioned there, thereby allowing the actual usable field of view size of the first illumination field IF1 to be adjusted without limit. A corresponding second field diaphragm BL2 is positioned at the output end of the second output integrator rod.

[0073] The subsequent REMA lens, also known as the REMA lens, images the intermediate field of view of the reticle mask system onto the output surface of the illumination system or the object surface 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 help of the second illumination beam SB2.

[0074] Figures 5A to 5C show several variations of this basic concept. The variation in Figure 5A differs from the example in Figure 4 in that prisms P1 and P2 are replaced by a pair of triangular prisms. In both cases, the hypotenuses of the triangular prisms are reflective, and the incident and exit surfaces are flat and adjacent to the upstream or downstream element via a gap.

[0075] Figure 5B shows that additional integrator rods ISW1 and ISW2 can also be integrated between the inlet integrator rod IE and the two outlet integrator rods IA1 and IA2 in either case.

[0076] Figures 5C and 5D show that the prism configuration PA, which results in the splitting into two illumination beam paths, does not necessarily have to be directly coupled to the exit side of the ingress integrator rod. Rather, additional deflection elements and / or integrator rod elements can be interposed.

[0077] In the exemplary embodiment shown in Figure 6, there are no intermediate prisms and / or other optical elements between the inlet integrator rod IE and the two outlet integrator rods IA1 and IA2. In this exemplary embodiment, both outlet integrator rods are each designed as so-called “tapered integrators.” In each of the outlet integrator rods IA1 and IA2, the size of the rectangular inlet surfaces EF1 and EF2 substantially corresponds to half the area of ​​the outlet surface AF1 of the inlet integrator rod IE, and as a result, the light emanating from the allocated subsurface is, in either case, fully coupled to the outlet integrator rod. However, in the previous example, the integrator rods each have a constant cross-sectional shape and size over their length, whereas in the example of Figure 6, the cross-sectional area of ​​the outlet integrator changes continuously between the inlet and outlet surfaces, and as a result, the two outlet surfaces AF2-1 and AF2-2 are positioned at a distance from the optical axis and opposite each other in the diametrical direction with respect to the optical axis. By increasing the angle as the light passes through the tapered integrator rod, different illumination may be required at the entrance of the inlet integrator rod, and the rod illumination is adapted so as not to violate the conservation of étendue.

[0078] Next, different exemplary embodiments of the illumination system ILL will be described based on Figures 7 and subsequent figures. For clarity, functional groups having functions similar to or corresponding to those of the first exemplary embodiment will be indicated accordingly. A significant difference from the previous exemplary embodiment lies in the configuration and operation of the homogenization unit HOM, which is substantially constructed with the help of a modified fly-eye lens. Further details regarding the configuration and function are shown in Figure 8.

[0079] The homogenization unit HOM includes a first grid configuration RA1 having a number of first refractive grid elements RE1 that receive light from the two-dimensional intensity distribution of the pupil forming surface PUP and generate a grid configuration from it, such as secondary light sources SL1, SL2, etc. The grid configuration, such as secondary light sources SL1, SL2, etc., is formed downstream of the first refractive grid element RE1, approximately at a distance of the focal length F1 of the first grid element RE1. In this way, the illumination beam coming from the pupil forming surface is divided into a number of light channels, and each illuminated first grid element and associated secondary light source is part of a separate light channel.

[0080] There is a second grid configuration RA2 having a second refractive grid element RA2, which is optically downstream of the first grid configuration, for example, in the region of a secondary light source SL1, and receives light from each optical channel or secondary light source, and helps to contribute to the superposition of light coming from different optical channels in the region of the output surface or image plane of the illumination system ILL. This superposition results in homogenization of the light intensity at the output surface.

[0081] The cross-sectional area or aperture of the first grid element RE1 determines the shape of the illuminated field of view, which in this example is rectangular. The first grid element RE1 is also called the field of view honeycomb.

[0082] The second grid element RE2, also called the pupil honeycomb, is positioned near each secondary light source. They image the first grid element RE1 onto the intermediate field of view FE of the illumination system via a downstream field of view lens. The intermediate field of view is then imaged onto the exit surface of the illumination system, as in the example above.

[0083] A special feature of this homogenization unit is that each of the first grid elements RE1 generates an optical channel belonging to the secondary light source (similar to a conventional fly-eye lens).

[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 second grid element is formed by a lens element divided into two different shaped parts. The first part AB1 acts only on the light of the first grid element assigned to it within its optical channel. The second part AB2 is formed integrally with the first part and is positioned only in adjacent second optical channels, and accordingly affects their light propagation.

[0085] In this example, the first optical channel created by grid element R1-1 is influenced by the lower half or first portion AB1 of the subsequent second grid element so that the light is input to the first illumination beam BS1 via the field lens FL, while the light coupled to the second optical channel by the adjacent first grid element R1-2 is influenced by the second portion AB2 of the second grid element and consequently coupled to the second illumination beam BS2, which propagates on the opposite side of the optical axis AX relative to the first illumination beam.

[0086] To achieve a distinctly different optical effect in the second grid element RE2, preferably, both the incident and exit surfaces are provided to be aspherical in the first portion AB1 and the second portion AB2, respectively. The surface shapes of the first portion and the second portion do not smoothly merge with each other; rather, bend lines arise as separating lines between the two portions on the surface of the second grid element.

[0087] Thus, 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 part, 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 for clarifying 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 an object plane OS, at a scale, for example, a scale of 1:4, onto an image plane IS oriented parallel to the object plane.

[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, each having exactly one concave mirror in each of the projection beam paths, including a number of optical elements.

[0092] The majority of the lens elements (more than 50%, particularly more than 60%, or more than 70%, or more than 80%) are positioned along a first portion OA1 of the optical axis OA, and these first portions extend coaxially perpendicular to each other with respect to the object plane OS and the image plane IS. Concave mirrors CM1 and CM2 are positioned on either side of the first portion OA1 and define a second portion OA2 of the optical axis, which, together with the first portion, defines an axial plane (in the plane of the drawing in Figure 9). In this example, the concave mirrors are positioned coaxially to each other on either side of the first portion, and the second portion OA2 of the optical axis is perpendicular to the first portion OA1, thereby creating an intersection shape.

[0093] The optical elements are arranged and formed mirror-symmetric with respect to a plane of symmetry SYM that extends perpendicular to the axial plane (here, the plane in the drawing) through a first portion OA1. For each concave mirror, within its assigned projection beam path, there is 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 towards the image plane IS. Deflection units ULE1 and ULE2 are each positioned on the side of the plane of symmetry SYM facing their respective assigned concave mirrors CM1 and CM2.

[0094] Between the object plane and the image plane, two exact real intermediate images (commonly called IMIs) of the assigned effective field of view are generated in each of the projection beam paths RP1 and RP2, resulting in the exact IMI1-1 and IMI2-1 in the first projection beam path, and IMI1-2 and IMI2-2 in the second projection beam path (see Figure 10).

[0095] Constructed solely of transparent optical elements and therefore being refractive (dioptric), the first lens portion OP1 is designed such that the pattern in each of the illuminated effective object fields is imaged into the first intermediate images IMI1-1, IMI1-2 of the respective projection beam paths and slightly reduced (for example, an imaging scale in the range of approximately 1.85:1 to approximately 1.75:1).

[0096] The second reflective / refracting lens section OP2 images the first intermediate images of the projected beam path onto each second intermediate image IMI2 with substantially no change in size. The second lens section OP2 includes separate concave mirrors CM1, CM2 and three upstream double-pass lens elements for each of the projected beam paths. In the second lens section, the projected beam path separates and travels along separate optical paths through separate partial lenses, and then the projected beam path is recombined into a common lens element in the region of the second intermediate image IMI2. The second intermediate image IMI2 lies between the two individual mirrors of ULE2; that is, the projected beam path remains separated at the second mirror of ULE2 and is only recombined afterward.

[0097] The third refractive lens portion OP3 is designed to scale down the second intermediate images IMI2-1 and IMI2-2 and form an image on 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 therefore 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 each lens element, i.e., the respective surface area to which radiation strikes, is symmetric with respect to the plane of symmetry SYM. Therefore, possible lens heating effects, particularly in near-field lens elements, are substantially symmetric with respect to the plane of symmetry, and thus possible corrections are simplified.

[0099] In each projection beam path, pupil surfaces P1, P2, and P3 are positioned 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, where the principal ray CR of optical imaging intersects the optical axis OA. The aperture of this system may be positioned in the region of the pupil surface P3 of the third lens portion OP3. The pupil surface P2 in the reflective / refracting second lens portion OP2 is positioned very close to each concave mirror CM.

[0100] To assist with color correction, a negative group NG with at least one scattering negative lens is positioned in each of the two projection beam paths immediately adjacent to the associated concave mirrors CM1 and CM2 in the region near the pupil. Here, the "region near the pupil" is defined as the region where the peripheral ray height (MRH) of the image is higher than the principal ray height (CRH). The peripheral ray height within the negative group region can be at least twice the principal ray height.

[0101] To provide a background, the contributions of lens elements with positive refractive power and lens elements with negative refractive power to the total refractive power, field curvature, and chromatic aberration in the optical system act in opposite directions. However, a concave mirror has positive refractive power just like a positive lens element, but has a counterintuitive effect on field curvature compared to a positive lens element. In addition, a concave mirror does not introduce chromatic aberration. Therefore, a reflective refractive system portion with a concave mirror near the pupil and an adjacent negative lens (Schupmann achromatic) is a sufficiently suitable means for achromaticizing the projection lens. A double-pass positive lens element PL can be placed between each deflection unit and the negative group, and this can be omitted in other exemplary embodiments (see Table 3).

[0102] An exceptional technical feature concerns the design of the deflection units ULE1 and ULE2. They are not designed as standalone reflective planar mirrors or deflection mirrors. Instead, the first deflection unit ULE1 and the second deflection unit ULE2 each have a substantially flat first reflective surface RF1 and a substantially flat second reflective surface RF2 that is directly following it. Each reflective surface is tilted by different angles around inclination axes perpendicular to the first and second portions with respect to the plane of symmetry SYM. The first reflective surface RF1 is used to deflect radiation coming from the object plane OS to the second reflective surface RF2, and the second reflective surface is used to deflect radiation coming from the first reflective surface RF1 towards the image plane.

[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 toward the second reflecting surface RF2 immediately following. The reflecting surface RF2 then reflects the beam in the second lens portion OP2 toward the associated concave mirror CM. After being reflected by the concave mirror and passing through three upstream lens elements twice, the beam then enters the second deflection unit ULE2, where the first reflecting surface RF1 deflects the beam toward the second reflecting surface RF2, and the second reflecting surface RF2 reflects it toward the first lens element of the third lens portion OP3.

[0104] If the inclination angle KW of the reflecting surface is defined as the angle enclosed by the surface normal NOR of the reflecting surface with the incident optical axis, then the inclination angles of the first reflecting surface on the side of the first lens portion are 67.5° each. At the second reflecting surface immediately following in each beam path, the inclination angle is then only 22.5°, i.e., corresponding to the complementary angle of the first inclination angle, which sums to 90°. The same applies to the second deflection unit ULE2, i.e., which deflects the beams coming from each concave mirror CM toward the third lens portion OP3, where the second portion of the optical axis OA2 is considered to be the incident optical axis.

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

[0106] Both reflective surfaces RF1 and RF2 of the deflection unit ULE are positioned optically close to the first intermediate image IMI1 of the associated projected beam path, and as a result, the beam footprint on the reflective surfaces appears as a rectangle with more or less rounded corners, positioned at a distance from the optical axis but close to it. More specifically, the first intermediate image lies between the two reflective surfaces RF1 and RF2, and in this way, both reflective surfaces are close to the intermediate image. At imaging scales of the first lens portion OP1 with at most very small magnification or slight reduction, the size of the intermediate image is not larger than, or only slightly larger than, the size of the generated effective object field OF, and as a result, the mirror surface with compact dimensions is sufficient to reflect the entire beam to the downstream optical element without aperture vignetting. This is especially true for the reflection from the first reflecting surface RF1 to the second reflecting surface RF2, which can also be made very compact in size because it is still optically close to the first intermediate image, particularly in the 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 explanatory purposes, the optical proximity or optical distance of an optical surface to a reference plane (e.g., the field plane or pupil plane) is described in this application by the so-called sub-aperture ratio (SAR). For the purposes of this application, the sub-aperture ratio (SAR) of an optical surface is defined as follows: SAR=sign(CRH)·(MRH / (|CRH|+|MRH|)) Here, MRH represents the peripheral ray height, CRH represents the principal ray height, and the sign function sign(x) represents the sign of x, where by convention, sign(0)=1. The principal ray height is the ray height of the principal ray at the field of view point of the object field of view that has the maximum field of view height in absolute terms. The ray height should be understood here as being signed. The peripheral 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 of view point does not need to contribute to the transfer of patterns placed on the object plane, especially in the off-axis image field of view.

[0108] The sub-aperture ratio is a signed variable that measures the proximity of a plane in the beam path to the field of view or pupil. By definition, the sub-aperture ratio is normalized to a value between -1 and +1, where it is zero at each field of view plane and jumps from -1 to +1 or vice versa at the pupil plane. Thus, a sub-aperture ratio of 1 in absolute terms identifies the pupil plane.

[0109] Therefore, the near field of view has a sub-aperture ratio close to 0, while the near pupil has a sub-aperture ratio close to 1 in absolute terms. The sign of the sub-aperture ratio indicates the position of the anterior or posterior plane of the reference plane.

[0110] A reflective surface can be designed as a nominal plane, that is, it defines a mathematical plane excluding manufacturing tolerances. Individual reflective surfaces or all reflective surfaces can also be designed with a specified deviation from the plane, and as a result, the reflective surfaces can function as corrective surfaces for aberrations such as distortion.

[0111] In the schematic example in Figure 9, the reflective surfaces are each manufactured as individual mirrors and housed in separate mounts. The example in Figure 10 shows that in either case, two of the deflecting mirrors or reflective surfaces may be designed to be combined as a triangular prism. These triangular prisms can be mounted together in 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 star-shaped sides. The prism may consist of, for example, multiple individual prisms that are joined or crimped together.

[0112] To illustrate the advantages offered by such a dual-reflection deflection unit compared to prior art, Figures 11A–11C show three folding configurations for comparison. Figure 11A shows a "classic" folding configuration in a reflective refractive projection lens with a single concave mirror CM. The first deflection mirror FS1, which reflects radiation coming from the object plane OS to the concave mirror CM, is located on the side away from the concave mirror, in the portion of the optical axis that is perpendicular to the object plane and the image plane. The same applies to the second deflection mirror, which deflects rays coming from the concave mirror to a third lens portion.

[0113] If two fields of view can be used simultaneously, the folding mirrors in each field of view will block the beam paths of the opposite field of view. Therefore, it is only possible to image a single field of view.

[0114] To enable (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 concave mirror. Figure 11B shows an attempt at a conventional plane mirror embodiment. In the folding variation in Figure 11B, the folding mirror FS reflects in the other direction in either case; that is, the concave mirror is positioned on the opposite side of the effective object field of view. In this case, the folding mirror is positioned in its own beam path. As a result, no functional system exists.

[0115] The difference between Figure 11B and Figure 11C is that in Figure 11C, the ray is positioned to the left (object side) of the optical axis of the horizontal arm (OA2) in the first deflection unit, and after reflection by the concave mirror, it is positioned to the right (image side) of OA2 in the second deflection unit. In Figure 11B, this is the opposite. As a result, the second deflection unit must be to the left of the first deflection mirror (i.e., closer to the object plane), and therefore within the object-first deflection mirror beam path.

[0116] Figure 11C shows, for comparison, a reflection by two deflection mirrors for every 90° deflection according to an exemplary embodiment of the present invention, i.e., a reflection by a two-stage reflective deflection unit. It can be seen that separation of beam paths leading to individual concave mirrors can be achieved in this way.

[0117] The following text describes some practical advantages of dual-field projection lenses. Increased throughput (components exposed per unit time) can be achieved by the possibility of simultaneously exposing two off-axis fields of view. This is achieved in the projection lens by including, among other things, two reflective / refracting partial lenses, i.e., two horizontal arms, each containing a concave mirror, in the second lens portion. Each lens portion containing a concave mirror is symmetric with respect to the plane of symmetry. The axis of symmetry is an imaginary line extending through the optical axis OA and parallel to the wider side of the effective image field.

[0118] Ideally, the field of view distance ABBF between the two effective image fields in the scanning direction (y-direction) should be such that the sum of the slit width (A*) of one field of view and the distance between the two fields of view precisely corresponds to the width of the stepper field of view (see Figure 2, which shows the object field of view).

[0119] Dual-field imaging can be used with scanning for double exposure, or with the help of a step-and-scan method.

[0120] In the first case, two identical structures must be placed adjacent to each other on the reticle or mask. During scanning, the substrate, such as a wafer, is continuously exposed by a first field of view having the first structure, and then by a second field of view having two identical structures. During normal scanning, the far peripheral areas of the wafer are exposed only once. This can be prevented if the scan starts with some overflow. The second image field of view may be blocked in the overflow region.

[0121] In the second case, two different structures can be placed next to each other on the reticle, and these can be combined to form a structure twice the size. The required step-and-scan operation then scans the two fields of view, and then jumps to the next dual field of view in a stepping step.

[0122] The following diagrams are used to illustrate some of the special features of scanning. Figure 12A shows a schematic top view of a wafer equipped with a number of directly adjacent rectangular exposure units (DIEs) with current standard dimensions of 26 mm width and 32 mm length. An enlarged section of Figure 12A and Figure 12B show a typical conventional scanning operation. The wafer moves in a meandering manner under the projection lens or image field or scanning slit used for exposure. There are two distinct states. In the scanning phase, shown by solid lines in Figures 12A and 12B, the substrate and mask or wafer and reticle move at a uniform and adapted speed (depending on the imaging scale of the projection lens) and the die is exposed. After each scanning operation, a reversal occurs, which is indicated by a dashed line in Figures 12A and 12B. This stops the movement of the reticle while the wafer is moving. This movement includes a deceleration phase, movement perpendicular to the scanning direction, and then acceleration in the opposite direction. There is no exposure during the reversal, and therefore this phase is not productive. Figures 12A and 12B schematically show the time-series sequences of the two phases.

[0123] For comparison, Figure 13B shows different phases of scanning operation with the help of a projection exposure apparatus having a dual field and two rigidly coupled scanning slits having the shape schematically shown in Figure 13A. It is immediately apparent that the scanning phase now extends across the length of two directly consecutive dies, and as a result, both dies can be exposed simultaneously during the scanning phase. Compared to the scanning phase, the unproductive reversal is performed only half as much as in the classical scanning operation, in the case of the dual field, the reversal occurs only after scanning both dies, whereas in the classical operation, the reversal occurs after scanning the dies.

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

[0125] The double-exposure scanning operation corresponds to the single-field scanning operation in terms of reticle and wafer movement. In both cases, one die is exposed first, and an adjacent die is exposed a second time. The difference from the single-field scanning operation is that at the upper and lower periphery of the wafer, one of the illuminations in the two fields must be switched off to prevent exposure beyond the wafer periphery.

[0126] The previous example demonstrates that double-folding in two deflection units for each projection beam path enables the use of a dual field. There are other potential uses and advantages beyond single-folding. One example is avoiding so-called "image flip" with a reflective-refracting projection lens using a single concave mirror and two intermediate images.

[0127] Such projection lenses offer advantages, for example, in terms of correcting chromatic aberration, but have the disadvantage of generating "image flip" 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 undesirable characteristic arises from the fact that the left-right image changes 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 flip. If this sum is even, image flip is avoided. This will be explained below using a comparison of the classical projection lens shown in Figure 11A and the projection lens PO-X shown in Figure 14.

[0128] Figure 14 shows a cross-sectional view of lens elements passing through a reflective-refracting projection lens PO-X that images an effective object field of view in the object plane, located outside the optical axis, into an off-axis effective image field of view located within the 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. The first deflection unit ULE1-X directs radiation coming from the object plane towards the concave mirror. The second deflection unit ULE2-X directs radiation reflected by the concave mirror towards 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 reflective deflection unit. The first deflection unit ULE-X has a first reflective surface RF1-X that deflects radiation coming from the object towards the second reflective surface RF2-X immediately following it. Next, the first deflection unit ULE-X reflects the radiation in the direction of the concave mirror. Then, the two reflective surfaces can be placed on separate individual mirrors, preferably the two reflective surfaces are formed on a common carrier element to fix their orientation relative to each other. Between the object plane and the image plane, there are two intermediate images and a total of four reflections, so the sum of the intermediate images and reflections is even. Thus, image flipping (see Figure 11A) present in this type of conventional system is avoided. Alternatively, the first deflection unit can be a single stage, and the second deflection unit can be two stages. As in the classical system, each deflection mirror is placed optically close to the associated intermediate image, i.e., in the near-field of view region.

[0129] The use of the type of two-stage reflective deflection unit described in this application is not limited to the exemplary embodiments. Such a deflection unit can also be used in projection lenses that produce only one intermediate image between the object plane and the image plane, or that produce a direct image without an intermediate image. The two-stage reflective deflection unit may be positioned in the projection beam path behind an upstream planar mirror and / or before a downstream deflection mirror.

[0130] The following table summarizes the specifications of two exemplary embodiments. Tables 1 and 1A apply to the exemplary embodiment in Figure 9 with NA=0.3, and Tables 2 and 2A apply to an exemplary embodiment not shown in the image 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 format. The "Surface" column indicates the number of the refractive surface or surface with different properties; 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" show the refractive index of the material at wavelengths of 365.5 nm (Index 1), 364.5 nm (Index 2), and 366.5 nm (Index 3). The "Half-Diameter" column shows the usable 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 optical surfaces are aspherical. Tables with the subscript "A" show the corresponding aspherical data, and aspherical surfaces 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 reflective and refractive projection lens, wherein the projection lens is used to form an image of a pattern arranged on the object surface (OS) of the projection lens on the image plane of the projection lens parallel to the object surface, A number of optical elements, including lens elements and concave mirrors (CMs), arranged between the object plane (OS) and the image plane (IS) along the optical axis (OA). Includes, The projection lens (PO) is designed as a dual-field projection lens to image a first effective object field (OF1), located outside the optical axis in the object plane, into an effective image field (IF1) located outside the optical axis in the image plane, along a first projection beam path (RP1); and simultaneously image a second effective object field (OF2), located outside the optical axis in the object plane and opposite to the first object field with respect to the optical axis, into a second effective image field (IF2) located outside the optical axis in the image plane, along a second projection beam path (RP2). Each of the projection beam paths includes a first deflection unit (ULE1) for deflecting radiation coming from the object surface (OS) toward a concave mirror, and a second deflection unit (ULE2) for deflecting radiation coming from the concave mirror toward the image plane (IS). In the aforementioned reflective / refracting projection lens, The optical element comprises a first lens portion (OP1) for imaging each of the effective object fields (OF1, OF2) of the object surface into a first intermediate image (IMI1), a second lens portion (OP2) for generating a second intermediate image (IMI2) by radiation from the first lens portion (OP1), and a third lens portion (OP3) for imaging the second intermediate image (IMI2) into the image plane (IS). In the region of the 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 (ULE1) is positioned optically close to the first intermediate image (IMI1), and the second deflection unit (ULE2) is positioned optically close to the second intermediate image (IMI2). A reflective-refracted projection lens characterized in that the first deflection unit (ULE1) and the second deflection unit (ULE2) each have a first reflective surface (RF1) and a second reflective surface (RF2) immediately following it, wherein the reflective surface is tilted at different angles of inclination with respect to the plane of symmetry about an inclination axis extending perpendicular to the first and second portions, the first reflective surface (RF1) is arranged to deflect the radiation coming from the object surface (OS) to the second reflective surface (RF2), and the second reflective surface is arranged to deflect the radiation coming from the first reflective surface in the direction of the image plane (IS).

2. The lens is positioned along a first portion (OA1) of the optical axis that extends coaxially and perpendicularly to the object plane (OS) and the image plane (IS), The concave mirrors (CM1, CM2) are positioned on both sides of the first portion, defining 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 elements are arranged and formed symmetrically with respect to a plane of symmetry (SYM) that extends perpendicular to the axial plane through the first portion (OA1), The reflective and refractive projection lens according to claim 1, characterized in that the deflection units (ULE1, ULE1) are each arranged on the side of the plane of symmetry (SYM) facing the assigned concave mirror.

3. The reflective and refractive projection lens according to claim 2, characterized in that the concave mirrors are arranged coaxially with respect to the first portion on both sides of the first portion and define a second portion oriented perpendicular to the first portion.

4. The reflective-refracting projection lens according to claim 1, characterized in that the inclination angles of the first reflective surface and the second reflective surface are matched to each other such that each beam incident on the first reflective surface parallel to the incident optical axis is deflected by the same angle on the first reflective surface and the second reflective surface.

5. The reflectance and refractive projection lens according to claim 1 or 2, characterized in that 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.

6. The first lens portion satisfies the condition 0.5 ≤ |β 1 The first imaging scale β to which | ≤ 2.0 applies 1 The reflective or refractive projection lens according to claim 1 or 2, wherein the projection lens has a reduction in imaging scale, and the first lens portion produces a reduction of up to half.

7. A reflective or refractive projection lens according to claim 1 or 2, characterized in that the image-side numerical aperture is less than 0.

5.

8. A reflecting and refractive projection lens according to claim 1 or 2, characterized in that the sum of reflections and intermediate images in the projection beam path between the effective object field (OF) in the object plane (OS) and the effective image field (IF) in the image plane is even.

9. A reflective and refractive projection lens, wherein the projection lens is used to form an image of a pattern arranged on the object surface (OS) of the projection lens on the image plane of the projection lens parallel to the object surface, It consists of numerous optical elements, including multiple lens elements and concave mirrors (CMs). A first effective object field of view (OF1), positioned outside the optical axis within the object plane, is imaged onto an effective image field of view (IF1), positioned outside the optical axis within the image plane, along a first projection beam path (RP1). Therefore, a number of optical elements are arranged between the object plane (OS) and the image plane (IS) along the optical axis (OA). Includes, The projection beam path includes at least one two-stage reflective deflection unit comprising a first reflective surface (RF1) and a second reflective surface (RF2) immediately following it, wherein the first reflective surface (RF1) is positioned to deflect radiation coming from the object plane (OS) to the second reflective surface (RF2), and the second reflective surface (RF2) is positioned to deflect radiation coming from the first reflective surface toward the image plane (IS), so that the first and second reflective surfaces of the deflection unit together achieve a 90° folding angle, thus creating a reflective-refracting projection lens.

10. The reflective refractive projection lens according to claim 9, wherein the projection beam path includes a first deflection unit (ULE1) for deflecting radiation coming from the object surface (OS) toward the concave mirror, and a second deflection unit (ULE2) for deflecting radiation coming from the concave mirror toward the image plane (IS), and the first deflection unit (ULE1) and / or the second deflection unit (ULE2) are two-stage reflective deflection units.

11. The reflective refractive projection lens according to claim 9, characterized in that one of the deflection units is a two-stage reflective deflection unit and the other deflection unit is a planar mirror.

12. A projection exposure apparatus for exposing a radiation-sensitive substrate, placed in the image plane region of a projection lens, with at least one image of a mask pattern, placed in the object plane region of the projection lens, Illumination system (ILL) for receiving light from a single light source and shaping illumination radiation to illuminate a first effective object field located outside the optical axis of the projection lens in the object plane, and simultaneously illuminating a second effective object field located outside the optical axis in the object plane, on the opposite side of the first object field. A reflecting and refractive projection lens configured to image the first effective field of view into a first effective field of view positioned outside the optical axis in the image plane along a first projection beam path, and simultaneously to image the second effective object field into a second effective field of view positioned 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 area of ​​the object surface of the projection lens, A device for holding the substrate such that the radiation-sensitive surface of the substrate is positioned in the region of the image plane of the projection lens. In the projection exposure apparatus, including, A projection exposure apparatus characterized in that the projection lens (PO) is embodied as described in claim 1.

13. The aforementioned lighting system, A refractive pupil forming unit (PFU) receives light from a primary light source (LS) and generates a two-dimensional intensity distribution on the pupil forming surface (PUP) of the illumination system, A refractive field shaping system (FFS) located optically downstream of the pupil shaping unit includes a homogenization 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 projection exposure apparatus according to claim 12, characterized in that

14. A projection exposure method for exposing a radiosensitive substrate with at least one image of a mask pattern, The steps include: preparing the pattern between the illumination system of the projection exposure apparatus and the projection lens so that the pattern is positioned in the area of ​​the object surface of the projection lens; The step of holding the substrate such that the radiation-sensitive surface of the substrate is positioned in the region of the image plane of the projection lens which is optically conjugate to the object plane, The steps include illuminating the 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) located outside the optical axis of the projection lens within the emission surface (ES) of the illumination system, and simultaneously, the second illumination beam (BS2) is guided along the second illumination beam path to a second illumination field (ILF) located on the opposite side of the first illumination field (ILF1) with respect to the optical axis (AX), and outside the optical axis within the emission surface. The step of projecting the portion of the pattern positioned in the illumination field onto the assigned image field on the substrate with the help of the projection lens. Includes, A projection exposure method using the projection lens described in claim 1 and / or the projection exposure apparatus described in claim 12.

15. The reflecting and refractive projection lens according to claim 1 or 2, characterized in that the first lens portion has a first imaging scale β1 to which the condition |β1| ≤ 1.2 applies, and / or the projection lens has a reduction imaging scale, and the first lens portion produces a reduction of up to half.

16. The reflective or refractive projection lens according to claim 1 or 2, characterized in that the image-side numerical aperture is in the range between 0.2 and 0.

4.

17. The homogenization unit (HOM) has an integrator rod configuration, The integrator rod configuration (ISA) includes an inlet integrator rod (IE) having an inlet surface (EF1) and an outlet surface (AF1), a first outlet integrator rod (IA1) optically coupled to a first partial surface (TF1) of the outlet surface (AF1), and a second outlet integrator rod (IA2) optically coupled to a second partial surface (TF2) of the outlet surface (AF1), wherein the outlet surface (AF2-1) of the first outlet integrator rod is assigned to a first illumination field (ILF1), and the outlet surface (AF2-2) of the second outlet integrator rod is assigned to a second illumination field (ILF2). The projection exposure apparatus according to claim 13, characterized in that

18. The homogenization unit (HOM) has a first grid configuration (RA1) and a second grid configuration (RA1), The integrator rod configuration (ISA) includes an inlet integrator rod (IE) having an inlet surface (EF1) and an outlet surface (AF1), a first outlet integrator rod (IA1) optically coupled to a first partial surface (TF1) of the outlet surface (AF1), and a second outlet integrator rod (IA2) optically coupled to a second partial surface (TF2) of the outlet surface (AF1), wherein the outlet surface (AF2-1) of the first outlet integrator rod is assigned to a first illumination field (ILF1), and the outlet surface (AF2-2) of the second outlet 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 for secondary light sources (SL1, SL2, ...), and 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 superimposing the light from the secondary light sources at least partially on the output surface. Each first grid element (RE1) creates an optical channel, and each of the second grid elements (RE2) is formed by a lens element having a first portion (AB1) located in the first optical channel and a second portion (AB2) located in the second optical channel, the portions having different surface shapes. The projection exposure apparatus according to claim 13, characterized in that

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