Catadioptric projection objective lens, projection exposure equipment and projection exposure method

Abstract

A catadioptric projection objective for imaging a pattern arranged in an object plane (OS) of the projection objective into an image plane of the projection objective parallel to the object plane, the catadioptric projection objective comprising a plurality of optical elements comprising a plurality of lenses and a concave mirror (CM) and arranged along an optical axis between the object plane (OS) and the image plane (IS). The projection objective (PO) is designed as a dual-field projection objective and is designed to image a first effective object field (OF1) outside the optical axis in the object plane along a first projection beam path (RP1) in a first effective image field (IF1) 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, opposite the first object field with respect to the optical axis, in a second effective image field (IF2) outside the optical axis in the image plane along a second projection beam path (RP2). Each projection beam path comprises a first deflection unit (ULE1) for deflecting radiation from the object plane (OS) to the concave mirror and a second deflection unit (ULE2) for deflecting radiation from the concave mirror in the direction of the image plane (IS). These optical elements form a first lens part (OP1) for imaging each effective object field (OF1, OF2) of the object plane into a first real intermediate image (IMI1), a second lens part (OP2) for generating a second real intermediate image (IMI2) by means of radiation from the first lens part (OP1), and a third lens part (OP3) for imaging each effective object field (OF2) of the object plane into a second real intermediate image (IMI2) by means of radiation from the second lens part (OP3). And a third lens part for imaging a second real intermediate image (IMI2) in the image plane (IS). The concave mirror (CM) of the projection beam path is arranged in the region of the pupil plane (P2) between the first intermediate image and the second intermediate image, 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).

Description

[0001] Technical Field and Background Art

[0002] The following disclosure is based on the German patent application with application number 10 2022 205 272.2 filed on May 25, 2022. The disclosure content of this patent application is incorporated into the content of the present application by reference.

[0003] The present invention relates to a catadioptric projection objective lens for imaging a pattern arranged in an object plane of the projection objective lens into an image plane of the projection objective lens parallel to the object plane. In addition, the present invention also relates to a projection exposure device including such a projection objective lens and a projection exposure method that can be implemented with the projection objective lens.

[0004] Microlithography projection exposure methods are currently mainly used for the production of semiconductor components and other finely structured parts. A mask (reticle) is used here, which has or produces a pattern of the structure to be imaged, for example a line pattern of a layer of a semiconductor component. The pattern is arranged in the region of the object surface of the projection lens in a projection exposure device between the exposure system and the projection objective and is irradiated with exposure radiation provided by the exposure system in the region of the effective object field. The radiation changed by the pattern passes through the projection objective as a projection beam, which images the pattern onto the substrate to be exposed in the region of the effective image field optically conjugated to the effective object field. The substrate usually carries a layer (photoresist, photoresist coating) that is sensitive to the projection radiation.

[0005] When selecting a suitable projection exposure system and process for a lithography process, different technical and economic criteria have to be taken into account, which are based inter alia on the typical structure sizes of the structures to be produced in the exposure substrate.

[0006] In order to produce relatively fine, demanding structures, projection exposure systems with high-aperture projection objectives are used, which typically operate at an operating wavelength in the deep ultraviolet radiation (DUV) range, for example around 193 nm.

[0007] For the production of medium critical or non-critical layers with typical structure sizes significantly greater than 150 nm, projection exposure systems designed for operating wavelengths greater than 200 nm are usually used. In this wavelength range, purely refractive (dioptric) reduction lenses are usually used. The optical elements have a common rectilinear optical axis. The object field and the image field can be centered on the optical axis (on-axis field). In some cases, this makes it possible to expose the entire field in a stepping operation (step and repeat), thereby promoting high throughput (complete exposure per unit time).

[0008] For a long time, projection exposure systems for operating wavelengths of 365.5 nm ± 2 nm (so-called i-line systems) have been used. These projection exposure systems use the i-line of mercury vapor, wherein the natural width of the i-line is limited to a narrower used bandwidth Δλ, for example, of about 2 nm, by means of filters or other means. With this type of light source, a relatively broad wavelength band of ultraviolet light is used during projection, so that the projection objective must provide a relatively strong chromatic aberration correction in order to ensure low-error imaging even with such a broadband projection light with the desired resolution.

[0009] It is also suggested to use a catadioptric projection objective for this wavelength range (see document DE 10 2006022958A1), that is, the projection objective includes both a refractive optical element with refractive power, that is, a lens, and a reflective element with refractive power, that is, a curved mirror, and usually includes at least one concave mirror.

[0010] If a catadioptric projection objective is to be constructed without a polarization-selective physical beam splitter, and without pupil obstruction and without beam tilt, then if the system is constructed rotationally symmetrically, an off-axis field must be used, i.e. a configuration in which the effective object field and the effective image field are located outside the optical axis.

[0011] The size of the off-axis field is limited by geometrical requirements and performance. In particular, the full field cannot be realized (as in the case of a stepper), so exposure is performed in scanning mode. This requires greater technical effort to achieve high throughput.

[0012] Most conventional projection exposure apparatuses are designed so that a separate effective object field is imaged in a separate effective image field. There are also methods of using two optical paths simultaneously, for example to increase throughput.

[0013] Patent document US 8,634,060 B2 describes a projection exposure apparatus capable of exposing two patterns and two wafers simultaneously. Light from a single light source is sent alternately through two separate, identical projection systems by fast optical switching, each having an exposure system and projection objective.

[0014] Document US 2008 / 259440 A1 describes a projection exposure apparatus which operates with two masks and two separate exposure systems, wherein the projection beam path is converged in the projection objective by a prism.

[0015] Document US2010 / 0053738 (corresponding to document US 8,705,170 B1) describes a projection objective lens that uses a single mask and branches the projection light path in the projection objective lens with the aid of a deflection mirror, thereby forming two separate image-side lens components that create two image fields so that two wafers can be exposed simultaneously. A patent application filed at the same time (published as document US2010 / 0053583 A1) discloses a suitable exposure system that can illuminate two separate, spaced-apart exposure fields simultaneously on the same mask. A diffractive optical element or prism is provided to separate the radiation originating from the light source. A lens array (fly's eye lens) of a honeycomb concentrator is provided to homogenize the exposure radiation.

[0016] A projection exposure system with two projection beam paths is described, for example, in the document US 8,384,875 B2 using a schematic embodiment. Two exposure systems are provided for exposing the mask, which can be constructed separately or integrated into a common exposure system (FIG. 12). An example of a catadioptric projection objective is also schematically shown. Descriptive data for post-processing of the system are not disclosed. Summary of the invention

[0017] In this context, the technical problem to be solved by the present invention is to provide a practical solution for a catadioptric dual-field projection objective, a projection exposure device equipped with the catadioptric dual-field projection objective, and a projection exposure method that can be implemented using the catadioptric dual-field projection objective.

[0018] The technical problem is solved according to the invention by a catadioptric projection objective having the features of claim 1, a projection exposure device having the features of claim 13, and a projection exposure method having the features of claim 15. Advantageous further developments are given in the dependent claims. The statements of all claims are hereby incorporated into the content of this description.

[0019] According to the technical solution of the present invention, a catadioptric projection objective is provided, which has a plurality of optical elements, which are arranged along the optical axis between an object plane and an image plane parallel to the object plane. The projection objective is designed as a dual-field projection objective and is designed to image a first effective object field arranged in the object plane outside the optical axis along a first projection optical path into a first effective image field located in the image plane outside the optical axis, and simultaneously image a second effective object field arranged in the object plane outside the optical axis, which is opposite to the first object field relative to the optical axis, along a second optical path into a second effective image field located in the image plane outside the optical axis.

[0020] Each projection beam path comprises a first deflection unit and a second deflection unit, the first deflection unit being used to deflect radiation from the object plane to the concave mirror, and the second deflection unit being used to deflect radiation from the concave mirror in the direction of the image plane. Thus, the projection objective has at least two concave mirrors, preferably exactly two concave mirrors, i.e. one concave mirror per projection beam path.

[0021] The technical solution is characterized in that these optical elements constitute a first lens component, a second lens component and a third lens component, the first lens component is used to image each effective object field of the object plane into a first real intermediate image, the second lens component is used to generate a second real intermediate image using radiation from the first lens component, and the third lens component is used to image the second real intermediate image in the image plane, so that the concave mirror of the projection light path is arranged in the area of ​​the pupil plane 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.

[0022] The design method described provides the possibility of constructing a projection objective that works with two simultaneously usable fields of practically usable size while having a compact overall structure. In principle, the dimensioning of the deflection unit is complicated by the boundary conditions. If the deflection surface can be designed to be relatively large, a vignetting-free deflection of a larger field can be implemented relatively simply, but this usually results in a significant structural size. If the structural size is to be kept small, the reflection surface may become too small for the field to be projected, which increases the risk of vignetting. The condition for providing two intermediate images is that the actually usable field size of the object surface is projected or imaged in the image plane using a relatively small reflection mirror surface.

[0023] The two projection beam paths can be used selectively or alternatively to each other. In particular, it is possible to use two effective object fields outside the optical axis at the same time. As a result, compared with conventional projection objectives with only a single object field of the same size outside the optical axis, an area of ​​the substrate with twice the size can be exposed per unit time. As a result, a higher throughput can be achieved compared to conventional off-axis projection objectives.

[0024] Preferably, the optical element comprises a plurality of lenses and two concave mirrors. According to an improved scheme, a plurality of lenses are arranged along a first section of the optical axis. The first section extends coaxially with each other and is perpendicular to the object plane and the image plane. The concave mirror is arranged on the opposite side of the first section and defines a second section of the optical axis oriented transversely to the first section. The optical axis is thus folded. In general, the projection objective has a rotational symmetry with reference to the folded optical axis. The first section and the second section are located in a common plane, which is referred to as the axial plane here. The optical element is arranged and designed symmetrically with respect to the symmetry plane. The symmetry plane extends through the first section perpendicular to the axial plane. A first deflection unit and a second deflection unit are provided for each concave mirror, the first deflection unit being used to deflect radiation from the object plane to the concave mirror, and the second deflection unit being used to deflect radiation from the concave mirror to the direction of the image plane. The deflection units are respectively arranged on one side of the symmetry plane facing the associated concave mirror.

[0025] The concave mirrors can be arranged coaxially with respect to one another so that the second section is oriented perpendicularly to the first section. The projection objective then has an overall cross-shaped arrangement of the optical elements. Here, the two concave mirrors are arranged coaxially opposite one another on different sides of the symmetry plane.

[0026] It is also possible for the second section to be oriented transversely to the first section or the plane of symmetry at an angle other than 90°, which may be desirable, for example, for reasons of installation space.

[0027] The characteristic in this case is that the deflection units are respectively arranged on the side of the symmetry plane facing the corresponding concave mirror. This makes it possible to use two projection light paths in the projection objective, each of which leads from an off-axis effective object field to an optically conjugate effective image field. The two off-axis effective object fields can be arranged symmetrically with respect to the symmetry plane and at a distance therefrom on the mutually opposite sides, and the corresponding application also applies to the associated effective image field.

[0028] There are many examples of catadioptric projection objectives in the prior art, in which the optical axis is folded one or more times by 90° in order to integrate one or more concave mirrors into the projection beam path between the object plane and the image plane, so that unobstructed and vignetting-free imaging is possible. For the folding, a plane mirror (folding mirror) is usually used, which is inclined 45° relative to the incident side section of the optical axis in order to achieve a 90° fold by a single reflection. Conventionally, the plane mirror is arranged on the side of the optical axis facing away from the concave mirror.

[0029] According to an improved solution, this traditional method is abandoned. Instead, according to the provisions, the first deflection unit and the second deflection unit respectively have a first reflection surface and an adjacent second reflection surface, and the first reflection surface and the second reflection surface are inclined at different inclination angles relative to the symmetry plane around an inclination axis extending perpendicular to the first section and the second section, wherein the first reflection surface is arranged to deflect radiation from the object surface to the second reflection surface, and the second reflection surface is arranged to deflect radiation from the first reflection surface to the image plane. As a result, the deflection unit is not designed as a 45° plane mirror, but as a two-stage reflection deflection unit, which completes the change of the radiation angle of the incident radiation by reflection in two directly successive stages. In the present application, "directly" especially means that there are no other optical elements between the first reflection surface and the second reflection surface.

[0030] The deflection elements are preferably arranged in each case on the side of the symmetry plane which faces the corresponding concave mirror in each case, ie, on the same side as the associated concave mirror.

[0031] The first reflective surface and the second reflective surface of the deflection unit can together form a folding angle of 90°, which is required for the cross-shaped configuration of the projection objective. However, the folding angle can also differ from 90°.

[0032] The inclination angles of the first reflection surface and the second reflection surface are preferably matched to each other so that the radiation appearing on the first reflection surface and the second reflection surface parallel to the optical axis on the incident side is deflected at the same angle. For example, a deflection of 45° is provided, so that a total deflection of 90° is formed. The inclination angle is defined here as the angle formed by the surface normal of the reflection surface and the incident side section of the optical axis. Accordingly, it can be provided, for example, that the first inclination angle is 67.5° and the second inclination angle is 22.5°. However, in some cases it may make sense that both reflection surfaces are inclined so that the two reflection surfaces deflect the deflected radiation to different degrees.

[0033] The reflecting surfaces can be constructed on separate single reflectors, which can also be individually adjusted to each other accurately. It is also feasible that two or more reflecting surfaces of the deflection unit are constructed on a common support element. The support element can be constructed, for example, with four triangular prisms. The triangular prisms can be fixed together in the center of the star-shaped cross section of the deflection element. As an alternative, all the reflecting surfaces required for the deflection can be combined and designed as a composite prism with star-shaped sides. The composite prism can, for example, consist of a plurality of individual prisms that are bonded or sandblasted together.

[0034] The first and second reflecting surfaces can each be designed flat, i.e. as planes. Within the scope of 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, it is also possible to purposefully provide a larger deviation of the surface shape from a flat surface, for example in order to achieve a certain influence on the shape of the wavefront.

[0035] The intermediate image is located in or close to the field plane of the projection lens which is optically conjugated 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 which is optically conjugated to the first field plane. By the arrangement close to the field, it can be achieved in particular that the reflection surfaces used for deflection can be kept relatively small, respectively, so that a compact structural size of the deflection unit can be achieved. Preferably, the first deflection unit and the second deflection unit are arranged in a region where the value of the subaperture ratio SAR is less than 0.3. In particular, the intermediate image can be arranged between two single mirrors of the deflection unit.

[0036] The first lens component should have as little magnification as possible or as little drastic magnification as possible, so that the size of the intermediate image does not exceed or does not significantly exceed the size of the effective object field. According to an improved solution, the first lens component has a first imaging ratio β1, for which the condition 0.5≤|β1|≤2.0 applies. When this condition is met, it can be achieved that the relatively small-sized reflective mirror of the deflection unit can be completely and thus without vignetting to transmit or transmit the field size that is actually usable and large enough. If it is significantly below the lower limit, the first lens component has too strong a reduction effect, so that a relatively high aperture angle may appear in the area of ​​the deflection unit, so that the deflection cannot be achieved or can only be achieved with a small enough field size using a sufficiently small reflective mirror. On the other hand, if it exceeds the upper limit, the first lens component has too strong a magnification effect, so that the aperture angle of the deflection unit is still reduced, but the aperture angle must be set to a relatively large area in order to be able to completely reflect the relatively large intermediate image. The first lens component can be designed as a 1:1 system, and the magnification should generally not exceed a factor of 1.2. The value β1 of the imaging ratio of the first lens component can thus be in particular in the range of 1.2 or less. As a result, a two-stage deflection can be achieved within a particularly compact construction.

[0037] According to a further embodiment, it is preferably provided that the projection objective has a reduced imaging ratio and that the first lens element forms at most half of the reduction.

[0038] The projection objective is designed as a scanning system. During scanning, only a portion of the object field is imaged by the projection objective at any one time. Therefore, a scanning movement is required to carry out a single exposure step, in which adjacent sections of the mask are transferred stepwise to the substrate.

[0039] In order to transfer the complete pattern of a 6" mask in a single exposure step by means of scanning, the effective object field should have a width of 104 mm. According to one refinement, the projection objective is designed to have an object field diameter OBH of at least 107 mm. The projection objective can be designed so that each effective object field has a size of 104×56 mm and can maintain a spacing of 38 mm relative to the optical axis.

[0040] Some embodiments are characterized in that the image-side numerical aperture is less than 0.5, preferably in the range of 0.2 to 0.4.

[0041] The present invention also relates to a projection exposure method for exposing a radiation-sensitive substrate arranged in the image plane region of a projection objective using at least one image of a pattern of a mask arranged in the object plane region of the projection objective, wherein a projection objective according to the present invention is used.

[0042] In addition, the present invention also relates to a projection exposure device for exposing a radiation-sensitive substrate arranged in the area of ​​the image plane of the projection objective using at least one image of a pattern of a mask arranged in the area of ​​the object plane of the projection objective, the projection exposure device comprising: a primary radiation source for emitting primary radiation; an exposure system for receiving the primary radiation and for forming exposure radiation directed to the mask; and a projection objective for forming at least one image of the pattern in the area of ​​the image plane of the projection objective, wherein the projection objective is designed according to the present invention.

[0043] The projection objective enables two adjacent dies to be scanned simultaneously. This also allows double exposure.

[0044] The projection exposure apparatus preferably comprises a central control unit for controlling the functions of the projection exposure apparatus, wherein the control unit is configured in at least one operating mode to operate the exposure system and the projection objective so that adjacent dies can be scanned simultaneously in a double field. In another operating mode, a double exposure can be performed.

[0045] The two-stage reflection deflection unit of the method described in the present invention can be used independently and advantageously relative to the protection scope of the claims of the present invention, for example, it can be used in a catadioptric projection objective with a single field, that is, with only one single effective object field. Thus, the present invention relates to a catadioptric projection objective, which is used to image a pattern arranged in the object plane of the projection objective in an image plane of the projection objective parallel to the object plane, the catadioptric projection objective comprising a large number of optical elements, the optical elements comprising a plurality of lenses and concave mirrors, and arranged along the optical axis between the object plane and the image plane, so that the effective object field arranged in the object plane outside the optical axis is imaged in the effective image field located in the image plane outside the optical axis along the projection light path, wherein at least one two-stage reflection deflection unit is arranged in the projection light path, the deflection unit having a first reflection surface and a second reflection surface directly following, wherein the first reflection surface is arranged to deflect radiation from the object plane to the second reflection surface, and the second reflection surface is arranged to deflect radiation from the first reflection surface to the direction of the image plane.

[0046] In particular, it can be provided that a first deflection unit for deflecting radiation from the object plane to a concave mirror and a second deflection unit for deflecting radiation from the concave mirror to the direction of the image plane are arranged in the projection optical path, wherein the first deflection unit and / or the second deflection unit are constructed as a two-stage reflection deflection unit.

[0047] It is possible that both the first deflection unit and the second deflection unit are each configured as a two-stage reflective deflection unit. It is also possible that only one of the deflection units is configured as a two-stage reflective deflection unit and the other deflection unit is configured as a plane mirror, wherein the first deflection unit or the second deflection unit can be configured as a two-stage reflective deflection unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Further advantages and aspects of the invention are derived from the claims and the following description of an exemplary embodiment, which is explained in more detail below with reference to the drawings.

[0049] Figure 1 A schematic diagram showing a projection exposure apparatus according to an embodiment;

[0050] Figure 2 A schematic top view of the object plane of a projection objective with two effective off-axis object fields is shown;

[0051] Figure 3 A schematic overview diagram showing a first embodiment of a dual field exposure system with an integrating rod arrangement;

[0052] Figure 4 Show Figure 3 Detailed diagram of the integrating column device;

[0053] FIG. 5A to FIG. 5DDifferent schemes of integrating column devices of other embodiments are shown;

[0054] Figure 6 An integrating rod arrangement having two tapered output integrating rods is shown;

[0055] Figure 7 A schematic overview diagram shows an embodiment of a double-field exposure system with a grid element in a homogenization unit;

[0056] Figure 8 Specifically show Figure 7 Homogenization unit;

[0057] Fig. 9 shows a schematic meridional lens cross section of a projection objective according to a first embodiment;

[0058] Fig.10 Show Fig. 9 Magnified shot of the area of ​​the deflection unit in the projection objective;

[0059] FIG. 11A to FIG. 11C Three folding situations are shown comparatively;

[0060] FIG. 12A to FIG. 12B A scheme showing a scanner with a single field;

[0061] FIG. 13A to FIG. 13B A scheme showing a scanner with dual fields;

[0062] Fig.14 Schematic meridional lens cross-section of a catadioptric projection objective with two intermediate images, a concave mirror, a two-stage reflective deflection unit, and a single-stage deflection unit is shown. DETAILED DESCRIPTION

[0063] In the following description of preferred embodiments, the term "optical axis" refers to a straight line or a series of straight line segments passing through the center of curvature of an optical element. The optical axis is folded on a folding mirror (deflecting mirror) or other reflecting surface. In these examples, the object is a mask (reticle) with a pattern of an integrated circuit; it can also be another pattern, such as a grid. In these examples, the image is projected onto a wafer provided with a photoresist layer, which serves as a substrate. Other substrates, such as elements for liquid crystal displays or substrates for gratings, are also possible.

[0064] exist Figure 1An example of a microlithography projection exposure apparatus PBA is shown in , which can be used in the production of semiconductor components and other fine components and works with light or electromagnetic radiation in the ultraviolet region (UV) to achieve a resolution of up to several micrometers. A mercury vapor lamp is used as a primary radiation source or light source LS. It emits a broad spectrum of emission lines with relatively strong intensities I in the wavelength range with central 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).

[0065] The projection exposure apparatus is an i-line system, which uses only light from the i-line, i.e. UV light with a central operating wavelength of about 365.5 nm. The natural full bandwidth of the i-line is limited to a narrower used bandwidth Δλ, for example about 2 nm, by means of filters or other means.

[0066] The exposure system ILL connected downstream of the light source LS forms two larger exposure fields ILF1 and ILF2 with clear boundaries and basically uniform illumination and radiation angles in its exit surface ES using the light originating from the single primary light source. The radiation angles match the telecentricity requirements of the projection objective PO arranged at the rear in the optical path.

[0067] The optical components which receive the light from the light source and form the exposure radiation directed to the mask M are referred to as the exposure system ILL of the projection exposure apparatus. The exposure system is a double-field exposure system. Figures 3 to 8 An embodiment is described.

[0068] The exposure system ILL has means for setting different exposure modes (illuminance settings), and is able to switch between conventional on-axis exposure with different coherences σ and off-axis exposure (off-axis illumination).

[0069] Arranged downstream of the exposure system is a device RS for holding and manipulating a mask M (reticle) so that the pattern arranged on the reticle is located in the object plane OS of the projection objective PO, which coincides with the exit plane ES of the exposure system and is also referred to here as mask plane OS.

[0070] The substrate to be exposed is, for example, a semiconductor wafer W, which is held by a device WS, which includes a scanning drive to move the wafer in a scanning direction (y direction) perpendicular to the optical axis OA synchronously with the mask M. The device WS (also called "lens stage") and the device RS (also called "mask stage") are components of the scanning device that are controlled by a scanning control device, which is integrated in the central control device CU of the projection exposure apparatus PBA in this embodiment.

[0071] Figure 2A schematic top view of the object plane OS of the projection objective PO (equivalent to the exit surface ES of the exposure system) is shown. As exemplarily shown therein, the exposure system ILL uses the light of the light source to illuminate two off-axis exposure fields ILF1 and ILF2 in the exit surface (light mask surface, object plane of the projection objective). The off-axis exposure fields are respectively rectangular, can be clearly or flexibly delimited and are basically uniformly illuminated. Each exposure field defines an effective object field that is actually available under projection exposure, so that there is a defined effective object field OF1 and a second effective object field OF2 in the light mask surface. Two rectangular effective object fields of nominally the same size are located on opposite sides of the optical axis OA in the y direction, respectively, outside the optical axis and spaced apart, and have a height A measured parallel to the y direction. * and a width B measured perpendicular thereto (in the x-direction or cross-scan direction) * >A * Aperture ratio AR = B * / A * For example, it can be 2, 2.5, 3, 5, 10 or 15.

[0072] In this example, the effective rectangular fields (ie, those actually used for imaging) have widths B and * =104mm and height A * = 56 mm. The distance ABF (field distance) between the corresponding field edges in the y direction is the distance d from one field to the optical axis. * =2x38mm, plus a field height (56mm), which is 132mm. The circle OBC consists of a side B* (=104mm) in the x direction and 2* (A) in the y direction (scanning direction). * +d * A rectangle of )(=188mm) is produced.

[0073] The circle OBC, which is centered on the optical axis OA, surrounds the effective object fields OF1, OF2 and is tangent to their corners, represents the size of the object field circle in a rotationally symmetrical system, within which the optical correction at all field points must correspond to the specification. This also applies to all field points in the effective object field. The larger the object field must be, the more complex it becomes to correct aberrations. The size of the circle is parameterized here by the object field radius OBH or half of the object field diameter OBH, which at the same time corresponds to the maximum field height of the object field points. The object field height OBH is approximately 107 mm.

[0074] The effective image fields IF1, IF2 optically conjugated to the effective object fields OF1, OF2 in the image plane IS have the same shape as the associated effective object fields and the same aperture ratio between height A and width B, but the absolute field size is reduced by the imaging ratio β of the projection objective in the case of a reduction effect of the projection objective (where (|β|<1), i.e. A=|β|A *and B = |β|B * .

[0075] The distance ABF (field distance) between the edges of the effective object field located on the same side in the y direction, measured in the scanning direction (y direction), is selected so that the corresponding distance between the mutually corresponding longer edges of the effective image fields IF1, IF2 is exactly the length of the "bare die" to be exposed. This length is 33 mm under current standards. The term "bare die" in semiconductor and microsystem technology refers to a single unpackaged workpiece of a semiconductor wafer, as a single semiconductor chip without a housing or package.

[0076] Figure 3 A schematic overview of a first embodiment of an exposure system ILL is shown. A mercury vapor lamp with a focusing lens is used as the primary light source LS, which focuses and reflects the light into the entrance aperture of the exposure system. An alternative (not shown) is to use a laser as the light source, for example a tripled solid-state laser with a wavelength of approximately 355 nm.

[0077] Downstream of the primary light source is a pupil shaping unit PFU, which is constructed exclusively with refractive optical components and is designed to generate a defined, local (two-dimensional) intensity distribution in a pupil surface PUP downstream of the exposure system ILL, which is sometimes also referred to as secondary light source or exposure pupil. Due to the influence or formation of the main properties of the exposure radiation by this local intensity distribution, this pupil surface is also referred to as pupil shaping surface PUP.

[0078] The pupil shaping unit PFU can be set variably so that, depending on the control of the optical components of the pupil shaping unit, different local exposure intensity distributions in the circular exposure pupil can be set, such as a conventional exposure setting with a circular exposure spot centered on the optical axis AX, a dipole exposure or a quadrupole exposure.

[0079] The refractive field shaping system FFS is optically connected downstream of the pupil shaping unit PFU. It comprises optical components for forming an exposure intensity distribution in the exit surface ES of the exposure system from the light coming from the pupil shaping surface. The field shaping system FSF comprises a homogenization unit HOM for homogenizing the light received by the pupil shaping unit. The homogenization unit has a dual function, since the optical components are furthermore designed to split the exposure light into a first exposure radiation beam BS1 and a second exposure radiation beam BS2, which are spaced apart from each other and impinge on the exit surface. The field shaping system FFS comprises coupling optics EK, which concentrate the light coming from the pupil shaping surface and couple it into the entrance surface EF1 of the integrating rod arrangement ISA. This is in particular in the embodiment of the invention. Figure 4 Shown enlarged in .

[0080] The integrating rod device ISA comprises an input integrating rod IE, which has a planar incident surface EF1, a planar exit surface EF2 parallel to the incident surface, and four planar lateral surfaces forming a rectangular cross section. The input integrating rod is made of a material transparent to the exposure light. The light is mixed and homogenized inside the input integrating rod by multiple reflections on the uncoated or, if necessary, coated circumferential surfaces (lateral surfaces) of the integrating rod, and is emitted at least partially homogenized at the exit surface AF1. The input integrating rod has a continuous rectangular cross section and defines a longitudinal center axis, which is located on the optical axis AX of the exposure system.

[0081] The integrating rod device further comprises a first output integrating rod IA1 and a second output integrating rod IA2, wherein the first output integrating rod and the second output integrating rod respectively have incident surfaces EF2-1 and EF2-2 and exit surfaces AF2-1 and AF2-2. The two output integrating rods IA1 and IA2 respectively have a rectangular cross-sectional shape and a cross-sectional area which is substantially half of the cross-sectional area of ​​the input integrating rod IE.

[0082] The output integrating rods IA1, IA2 are arranged on diagonally opposite sides with a spacing relative to the optical axis AX of the exposure system. The first output integrating rod IA1 is optically coupled to the first sub-surface TF1 of the exit surface of the input integrator, so that the light emitted through the first sub-surface TF1 enters only the first output integrating rod IA1. The same also applies to the opposite side, where the light originating from the sub-surface TF2 enters the second output integrating rod IA2.

[0083] Two prisms P1 and P2 of the prism device PA are arranged between the input integrating rod IE and the two output integrating rods IA1 and IA2. The first prism P1 has a rectangular, flat incident surface, which directly follows the first sub-surface TF1 with an air gap LS in the middle and receives the radiation emitted from the sub-surface. The flat exit surfaces have the same size and are directly located in front of the incident surface of the first output integrating rod IA1 with an air gap in the middle. The prism also has two flat lateral surfaces oriented at an angle of 45° relative to the incident surface and the exit surface, and the lateral surfaces have a reflective coating respectively. The reflective coating can be mirror-treated, for example, by coating an aluminum layer or a dielectric layer.

[0084] Due to the double deflection on the mirror surfaces of the prisms that are offset parallel to each other, the light emerging from the sub-surface TF is deflected to a position further away from the optical axis. Each prism therefore optically couples one of the output integrating rods IA1, IA2 to the corresponding sub-surface TF1, TF1 of the exit surface AF1 of the input integrating rod and guides the light from a position close to the axis to a position away from the axis.

[0085] This device makes the light incident on the input integrating rod IE substantially evenly divided into two identical parts on the exit surface AF2-1 of the first output integrating rod and the exit surface AF2-2 of the second output integrating rod, and at the same time mixed by multiple internal reflections in both the input integrating rod and the output integrating rod.

[0086] Directly at the exit of the first output integrating column IA1 there is the intermediate field plane ZE of the exposure system. There an adjustable field diaphragm BL1 is arranged, which allows the actually available field size of the first exposure field IF1 to be continuously adjusted. A corresponding second field diaphragm BL2 is arranged at the exit of the second output integrating column.

[0087] The subsequent lens REMA, also called REMA lens, images the intermediate field plane of the mask system onto the exit surface of the exposure system or the object plane of the subsequent projection objective. The first exposure radiation beam generates a first exposure field ILF1 on one side of the optical axis AX, while the second exposure field ILF2 is exposed oppositely and at a distance from the optical axis by means of a second exposure radiation beam SB2.

[0088] FIG. 5A to FIG. 5C Several variations of this basic concept are shown. Figure 5A Variations of Figure 4 The difference of the above example is that the prisms P1 and P2 are replaced by a pair of triangular prisms, the hypotenuse surfaces of the triangular prisms are mirrored, the incident surface and the exit surface are flat and abut the upstream or downstream element across the air gap.

[0089] Figure 5B It is shown that further integrating columns ISW1 , ISW2 can be integrated between the input integrating column IE and the two output integrating columns IA1 , IA2 .

[0090] Figure 5C and Figure 5D It is shown that the prism arrangement PA which leads to the splitting into two exposure beam paths does not necessarily have to be coupled directly to the exit side of the incident integrating rod. Instead, further deflection elements and / or integrating rod elements can also be connected in between.

[0091] exist Figure 6 In the embodiment of the present invention, there is no intermediate prism and / or other optical element between the input integrating column IE and the two output integrating columns IA1 and IA2. In this embodiment, the two output integrating columns are respectively constructed as so-called "conical integrating columns". For each of the output integrating columns IA1, IA2, the size of the rectangular incident surface EF1, EF2 is substantially equivalent to half the area of ​​the exit surface AF1 of the input integrating column IE, so that the light emitted from the assigned sub-surface is completely coupled into the output integrating column. In contrast to the previous examples, the integrating columns each had a cross-sectional shape and a cross-sectional size that were constant over their length. Figure 6 In the embodiment of the invention, the cross-sectional area of ​​the output integrating rod changes continuously between the incident surface and the exit surface, so that the two exit surfaces AF2-1 and AF2-2 are arranged opposite to each other with a distance from the optical axis. Due to the increase in the angle when passing through the tapered integrating rod, different illumination may be required at the entrance of the input integrating rod, and the rod illumination is adjusted so that the light transmission efficiency conservation is not violated.

[0092] according to Figure 7 A further embodiment of an exposure system ILL is shown. For the sake of simplicity, functional components that are similar or correspond to those in the first exemplary embodiment have corresponding names. A significant difference from the previous exemplary embodiment is the structure and mode of operation of the homogenization unit HOM, which is essentially constructed with the aid of a modified honeycomb concentrator. Details on the structure and function are given in Figure 8 Shown in.

[0093] The homogenization unit HOM comprises a first grid arrangement RA1 having a plurality of refractive first grid elements RE1 which receive the light of the two-dimensional intensity distribution of the pupil shaping surface PUP and form therefrom a grid arrangement of secondary light sources SL1, SL2, etc., which are located behind the first grid element RE1 at a distance of approximately the focal length F1 relative to the first grid element. In this way, the exposure radiation beam from the pupil shaping surface is decomposed into a plurality of optical channels, wherein each illuminated first grid element and the associated secondary light source belong to its own optical channel.

[0094] There is also a second grid arrangement RA2 with refractive second grid elements RA2, which is optically arranged behind the first grid arrangement in the region of the secondary light source SL1 etc. and serves to absorb the light of the various optical channels and the secondary light sources and to contribute to at least partial superposition of the light from the different optical channels in the region of the exit surface or image plane of the exposure system ILL. This superposition achieves homogenization or averaging of the light intensity in the exit surface.

[0095] The cross-sectional area or the aperture of the first grid element RE1 determines the design of the illuminated exposure field and is rectangular in this example, for example. The first grid element RE1 is also referred to as field cell.

[0096] The second grid element RE2 is also called a pupil cell and is arranged close to the corresponding secondary light source. The second grid element images the first grid element RE1 via a downstream field lens onto the intermediate field plane FE of the exposure system. It is imaged onto the exit surface of the exposure system as in the previous example.

[0097] The homogenization unit is characterized in that each first grid element RE1 (as in a conventional honeycomb concentrator) still forms an optical channel belonging to the secondary light source.

[0098] However, each second grid element RE2 is not assigned to only one first grid element, but to two directly adjacent first grid elements, namely grid elements RE1-1 and RE1-2. The second grid elements are each formed by a lens element, which is divided into two differently designed segments. The first segment AB1 acts only on the light of the assigned first grid element in its optical channel. The second segment AB2 is formed integrally with the first segment and is only located in the adjacent second optical channel and accordingly affects its light propagation.

[0099] In this example, a first optical channel generated by one grid element R1-1 is influenced by the lower half of a subsequent second grid element or its first segment AB1 in such a way that light is introduced into a first exposure radiation beam BS1 via a field lens FL, while light coupled into the second optical channel by an adjacent first grid element R1-2 is influenced by the second segment AB2 of the second grid element in such a way that it is coupled into a second exposure radiation beam BS2, which propagates on the optical axis AX on an opposite side relative to the first exposure radiation beam.

[0100] In order to achieve different degrees of optical effects on the second grid element RE2, it is preferably provided that both the incident surface and the exit surface in the first segment AB1 and the second segment AB2 are designed to be non-spherical. The surface shape of the first segment and the second segment does not transition smoothly, but forms a folding line on the surface of the second grid element as a dividing line between the two segments.

[0101] This hybrid concept is thus characterized in that in the region of the pupil condenser (second grid element RE2), a dense arrangement of multiple refractive powers with two different surface shapes, alternating in the spatial direction, is provided. In particular, a dense arrangement of refractive powers with indistinct transitions is formed. The second grid element RE2 (pupil condenser) can be conceptually regarded as a lens consisting of off-axis lens segments, wherein preferably at least one side is aspherical and the size of the lens corresponds to the size of the associated field cell.

[0102] Fig. 9 A schematic meridional lens section of an embodiment of a catadioptric projection objective PO is shown, including a selected radiation beam, in order to illustrate the imaging beam path of the projection radiation extending through the projection objective during operation. The projection objective is designed as a demagnifying imaging system for imaging a pattern of a mask arranged in its object plane OS on its image plane LS oriented parallel to the object plane at a reduced scale, for example a scale of 1:4.

[0103] The projection objective is designed according to an embodiment of the present invention to be protected, and has a numerical aperture NA on the image side, which is in the range of 0.2 < NA < 0.4, for example, NA = 0.3.

[0104] The projection objective is configured as a two-field projection objective. The projection objective is designed to image a first effective object field OF1 arranged outside the optical axis OA in the object plane OS along a first projection optical path RP1 onto a first effective image field IF1 located outside the optical axis OA in the image plane IS, and at the same time to image a second effective object field OF2 arranged outside the optical axis and opposed to the first object field with respect to the reference optical axis along a second optical path RP2 onto a second effective image field IF2 located outside the optical axis in the image plane.

[0105] The projection objective includes a large number of optical elements, which include a plurality of lenses (for example, 15 to 25 lenses) and exactly two concave mirrors CM1, CM1, wherein exactly one concave mirror is provided in each projection optical path.

[0106] Most of the lenses (more than 50%, in particular 60% or more, or 70% or more, or 80% or more) are arranged along a first section OA1 of the optical axis OA, wherein the first sections extend coaxially perpendicular to the object plane OS and the image plane IS. The concave mirrors CM1, CM2 are arranged on opposite sides of the first section OA1, and define a second section OA2 of the optical axis, and the second section together with the first section defines an axial plane (this axial plane is located in the Fig. 9 mid-plane). In this example, the concave mirrors are arranged coaxially on opposite sides of the first section, and the second section OA2 of the optical axis is perpendicular to the first section OA1, thus forming a cross shape.

[0107] The optical elements are arranged mirror-symmetrically with respect to a symmetry plane SYM, and are configured to extend perpendicularly to the axial plane (here the mid-plane) through the first section OA1. In the corresponding projection optical paths, a first deflection unit ULE1 and a second deflection unit ULE2 are provided for each concave mirror. The first deflection unit is used to deflect the radiation from the object plane OS to the concave mirror, and the second deflection unit is used to deflect the radiation from the concave mirror in the direction of the image plane IS. The deflection units ULE1, ULE2 are respectively arranged on one side of the symmetry plane SYM facing the associated concave mirrors CM1 and MC2.

[0108] Between the mid-plane and the image plane, exactly two real intermediate images (collectively referred to as IMI) of the corresponding effective object field are formed in each projection optical path RP1, RP2, that is, IMI1-1, IMI2-1 in the first projection optical path and IMI1-2 and IMI2-2 in the second projection optical path (refer to Fig.10 ).

[0109] The first lens component OP1, which is composed only of transparent optical elements and is therefore refractive (dioptric), is designed to image the pattern in each irradiated effective object field slightly reduced (imaging ratio, for example, in the range of about 1.85:1 to about 1.75:1) in the first intermediate image IMI1-1, IMI1-2 of the corresponding projection optical path.

[0110] The catadioptric second lens component OP2 images the first intermediate image of the projection light path in the respectively corresponding second intermediate image IMI2 with substantially no size change. The second lens component OP2 has respective concave mirrors CM1, CM2 and three upstream connected double-pass lenses for each projection light path. In the second lens component, the projection light paths are separated and extend along separate optical paths through separate sub-lenses, after which they are brought together again in the area of ​​the second intermediate image IMI2 to form a commonly used lens. The second intermediate image IMI2 is located between the two single reflectors of ULE2, that is, at the second reflector of ULE2, and the projection light paths are still separated before being reconverged.

[0111] The refractive third lens component OP3 is designed to image the second intermediate images IMI2-2, IMI2-2 in a reduced scale in the image plane IS.

[0112] All lenses of the first lens unit OP1 and all lenses of the third lens unit OP3 and thus all lenses on the first section OA1 of the optical axis are shared for the two projection beam paths. The footprint of the projection beam paths on the individual lens surfaces, i.e. the surface areas respectively exposed to the radiation, are here respectively symmetrical about the symmetry plane SYM. Thus, any lens heating effects that may occur, in particular in the lenses close to the field, are substantially symmetrical about the symmetry plane, thereby simplifying any possible correction.

[0113] In each projection beam path, between the object plane and the first intermediate image, between the first intermediate image and the second intermediate image, i.e. between the second intermediate image and the image plane, there is a pupil surface or pupil plane P1, P2, P3, respectively, where the main radiation CR of the optical image intersects the optical axis OA. In the region of the pupil surface P3 of the third lens component OP3, an aperture stop of the system can be arranged. The pupil surface P2 in the catadioptric second lens component OP2 is adjacent to the corresponding concave mirror CM.

[0114] In order to support the chromatic correction, a negative assembly NG having at least one diverging negative lens is arranged in each of the two projection beam paths in the immediate vicinity of the associated concave mirror CM1, CM2 in a region close to the pupil. Here, the "region close to the pupil" refers to a region in which the marginal ray height (MRH) of the image is greater than the chief ray height (CRH). In the region of the negative assembly, the marginal ray height can be at least twice the chief ray height.

[0115] Background: Although the contributions of a lens with positive refractive power and a lens with negative refractive power to the total refractive power, field curvature and chromatic aberration in an optical system are opposite, a concave mirror has positive refractive power like a positive lens, but has the opposite effect on the field curvature compared to a positive lens. In addition, a concave mirror does not introduce chromatic aberration. Therefore, a refractive-reflective system component having a concave mirror close to the pupil and an adjacent negative lens (Schupmann achromat) is very suitable for a device for color reduction of a projection objective. A double-pass positive lens PL can be arranged between the corresponding deflection unit and the negative assembly, and the positive lens can also be omitted in other embodiments (see Table 3).

[0116] The extraordinary technical features relate to the design of the deflection units ULE1, ULE2. The deflection units are not constructed as single-reflection plane mirrors or deflection mirrors. Instead, the first deflection unit ULE1 and the second deflection unit ULE2 each have a substantially planar first reflection surface RF1 and a substantially planar second reflection surface RF2 following therefrom. The reflection surfaces are respectively inclined at different inclination angles relative to the symmetry plane SYM around an inclination axis extending perpendicular to the first section and the second section. The first reflection surface RF1 is used to deflect radiation from the object plane OS to the second reflection surface RF2, and the second reflection surface is used to deflect radiation from the first reflection surface RF1 to the direction of the object plane.

[0117] In each projection optical path, the first reflection surface RF1 is a surface that receives the radiation beam from the last lens of the first lens component OP1 and reflects it in the direction of the second reflection surface RF2 that follows it. It then reflects the radiation beam in the second lens component OP2 to the associated concave mirror CM. After reflecting on the concave mirror and passing through three upstream-connected lenses twice, the radiation beam then strikes the second deflection unit ULE2, whose first reflection surface RF1 deflects the radiation beam to the second reflection surface RF2, which reflects it in the direction of the first lens of the third lens component OP3.

[0118] If the tilt angle KW of the reflection surface is defined as the angle enclosed by the surface normal of the reflection surface and the incident side optical axis, the tilt angle of the first reflection surface on the first lens component side is 67.5°. For the second reflection surface immediately following in each optical path, the tilt angle is only 22.5°, which corresponds to the complementary angle of the first tilt angle and the 90° angle. The same applies to the second deflection unit ULE2, that is, the deflection unit that deflects the radiation beam from the corresponding concave mirror CM to the direction of the third lens component OP3, wherein the second segment OA2 of the optical axis belongs to the input side optical axis.

[0119] Relative to the incident side optical axis, a 90° deflection is achieved in two directly consecutive steps, i.e. once by x degrees and a second time by 90-x°. The two associated reflection surfaces of the deflection unit are each located on the same side of the symmetry plane SYM, i.e. on the side where the associated concave mirror CM is located.

[0120] The two reflection surfaces RF1 and RF2 of the deflection unit ULE are respectively optically close to the first intermediate image IMI1 of the assigned projection light path, so that the coverage area of ​​the radiation beam on the reflection surface is more or less a rectangle with chamfers and keeps a distance relative to the optical axis, but is still close to the optical axis. To be precise, there is a first intermediate image between the two reflection surfaces RF1 and RF2, by which the two reflection surfaces are close to the intermediate image. In the case where the first lens component OP1 has at most a very low magnification or a slightly reduced imaging ratio, the size of the intermediate image is not or only slightly larger than the size of the generated effective object field, so that a mirror with compact dimensions is sufficient to transmit the entire radiation beam to the optical element connected downstream without vignetting. This is particularly applicable to the reflection from the first reflection surface RF1 to the second reflection surface RF2, which can also have very compact dimensions because it is still in the optical vicinity of the first intermediate image, especially in the region where the subaperture ratio SAR is less than 0.3 in amplitude. The SAR is preferably 0.2 to 0.3.

[0121] Explanation: In the present invention, the optical proximity or optical distance of an optical surface to a reference plane (such as a field plane or a pupil plane) is described by the so-called subaperture ratio SAR. The subaperture ratio SAR of an optical surface is defined for the purpose of this application as follows:

[0122] SAR=sign(CRH) * (MRH / (|CRH|+|MRH|))

[0123] Here, MRH is the marginal ray height, CRH is the principal ray height, and the sign function sign(x) indicates the sign of x, where sign(0)=1 applies by convention. The principal ray height is understood to be the radiation height of the principal ray of the field point of the object field with the maximum longitudinal height in terms of magnitude. This radiation height is to be understood here as having a sign. The marginal ray height is understood to be the radiation height of the radiation with the maximum aperture starting from the intersection of the optical axis and the object plane. The field point does not necessarily contribute to the transfer of a pattern arranged in the object plane - in particular in off-axis image fields.

[0124] The subaperture ratio is a signed value that is a measure of the field proximity or pupil proximity to a plane in the optical path. By definition, the subaperture ratio is normalized to a value between -1 and +1, where the subaperture ratio is zero in each field plane and the subaperture ratio jumps from -1 to +1 in the pupil plane, or vice versa. A subaperture ratio of 1 in magnitude therefore determines the pupil plane.

[0125] Thus, a plane close to the field has a subaperture ratio close to 0, while a plane close to the pupil has a subaperture ratio close in magnitude to 1. The sign of the subaperture ratio indicates the position of the plane in front of or behind the reference plane.

[0126] The reflective surface can be designed nominally as a plane, ie a mathematical plane that does not exceed manufacturing tolerances. It is also possible to design a single or all reflective surfaces to have a defined deviation from a plane, so that the reflective surface can be used as a correction surface for aberrations, such as distortion, etc.

[0127] exist Fig. 9 In the exemplary examples of , the reflecting surfaces are each constructed as a single-sided mirror and are mounted in a specific holder. Fig.10 The example shows that every two deflection mirrors or reflective surfaces can be implemented in combination as a triangular prism. The triangular prism can be fixed together in the center of the star-shaped cross section of the deflection element. As an alternative, all mirror surfaces required for deflection can be combined and designed as a composite prism with star-shaped sides. This prism can, for example, consist of a plurality of individual prisms that are glued or sandblasted together.

[0128] To illustrate the advantages provided by this dual reflection deflection unit compared with the prior art, Fig.11A until Fig. 11C Three folding situations are shown for comparison. Fig.11A The "classical" folding in a catadioptric projection objective with a single concave mirror CM is shown. The first deflection mirror FS1, which reflects radiation from the object plane OS to the concave mirror CM, is located on the side of the part of the optical axis perpendicular to the object plane and the image plane facing away from the concave mirror. The same applies to the second deflection mirror, which deflects radiation from the concave mirror to the third lens element.

[0129] If two fields need to be used simultaneously, the folding mirrors of each field will block the light path of the opposite field, so that only a single field can be imaged.

[0130] In order to achieve (simultaneous) imaging of the two fields, the deflection units should each be located on the side of the optical axis facing the associated horizontal arm or concave mirror. Fig. 11B An attempt at implementation with a conventional flat mirror is shown. Fig. 11B The folding solutions in each case reflect the folding mirror FS in the other direction, i.e. the concave mirror is on the side opposite to the effective object field. In this case, the folding mirrors are in their respective beam paths. No functioning system is formed.

[0131] Fig. 11B and Fig. 11C The difference is that in Fig. 11C In the example, the radiation is located on the left side (object side) of the optical axis of the horizontal arm (OA2) on the first deflection unit and is located on the right side (image side) of OA2 after being reflected by the concave mirror on the second deflection unit. Fig. 11B Therefore, the second deflection unit must be located to the left of the first deflection mirror (ie, close to the object plane), and thus in the beam path from the object to the first deflection mirror.

[0132] In comparison, Fig. 11C The figure shows a deflection unit with two deflection mirrors each deflected by 90°, that is, a two-stage reflection, according to an embodiment of the present invention. It can be seen that the light paths to each concave mirror can be separated.

[0133] Some practical advantages in a dual-field projection lens are explained below. An increase in throughput (components exposed per unit time) can be achieved by the ability to expose two off-axis fields simultaneously. This is achieved in particular in the case of a projection objective in that the second lens component comprises two catadioptric sub-lenses, i.e. two horizontal arms, each of which comprises a concave mirror. The lens components comprising the concave mirrors are symmetrical about a symmetry plane, respectively. Here, the symmetry plane is an imaginary line extending through the optical axis OA and parallel to the wide side of the effective image field.

[0134] Ideally, the field distance ABBF between the two effective image fields in the scanning direction (y direction) should make the field (A * ) and the distance between the two fields is exactly equal to the width of the stepper field (see Figure 2 The situation shown in the physical field).

[0135] The double field can be used for scanning with double exposures or by means of the step-and-scan method.

[0136] In the first case, two identical structures must be arranged adjacent to each other on the mask or on the reticle. During scanning, the substrate, for example a wafer, is then exposed in rapid succession by a first field with the first structure and then by a second field with the second identical structure. During normal scanning, the very edge regions of the wafer are exposed only once. This can be avoided if there is overflow at the start of scanning. It is also conceivable to illuminate the second image field in the overflow region.

[0137] In the second case, two different structures can be arranged adjacently on the mask, which structures allow a double-sized structure to be combined. The necessary step-and-scan process will scan two fields and then jump to the next double field in one step.

[0138] Some features of the scan are described below with reference to the accompanying drawings. Fig. 12A The schematic top view shows a wafer on which a plurality of rectangular exposure unit dies having a standard format of 26 mm in width and 32 mm in length are arranged directly adjacent to each other. Fig. 12A and Fig. 12B The enlarged detail in the figure shows a typical conventional scanning process. Here, the wafer moves in a meandering manner under the projection objective or in the image field or scanning gap used for exposure. There are two different states. Fig. 12A , Fig. 12B In the scanning phase shown in the solid line, the substrate and mask or wafer and reticle move at a uniform and matching speed (depending on the imaging ratio of the projection objective) and the die is exposed. Each scanning process is followed by a change in direction, which is Fig. 12A , Fig. 12B The movement of the reticle is stopped here, while the wafer is moving. The movement includes a braking phase, a movement perpendicular to the scanning direction and a subsequent acceleration in the opposite direction. No exposure occurs during the change of direction, i.e. this phase is ineffective. Fig. 12A , Fig. 12B The time sequence of the two phases is shown schematically.

[0139] In comparison, Fig. 13B The scanning slits with dual fields and two rigid couplings are shown. Fig.13A 1 . It can be clearly seen that the scanning phase extends over the length of two directly consecutive dies, so that two dies can be exposed simultaneously during the scanning phase. Compared to the scanning phase, unproductive changes of direction occur half as often as in a conventional scanning process, in which a change of direction is performed after the scanning of one die, whereas in the case of a double field a change of direction is performed after the scanning of both dies has been completed.

[0140] To achieve this type of scanning, in this embodiment two scanning slits or effective object fields are arranged according to Fig.13A Arrangement.

[0141] In terms of the movement of the reticle and wafer, the scanning process in double exposure corresponds to the scanning process for a single field. Here, one die is exposed for the first time and the adjacent die is exposed for the second time. In contrast to the scanning process for a single field, the exposure of one of the two fields must be closed at the upper and lower edges of the wafer so that no more than the edge of the wafer is exposed.

[0142] The present example shows that a two-stage folding on two deflection units per projection beam path enables the use of a double field. Further application possibilities and advantages are achieved compared to a single folding. One example is the avoidance of the so-called "image flip" in a catadioptric projection objective with a single concave mirror and two intermediate images.

[0143] Such projection objectives offer advantages, for example, in terms of correction of chromatic aberrations, but have the disadvantage of producing an "image flip" during imaging. This means that features described on the mask in a right-handed coordinate system are described in the image plane using a left-handed coordinate system. This unfavorable property is due to the change in chirality 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 an odd number, this leads to an image flip. If the sum is an even number, an image flip is avoided. Fig.11A The classic projection lens and Fig.14 A comparison between the projection objectives PO-X and PO-X is used to explain this.

[0144] Should Fig.14The lens cross section through the catadioptric projection objective PO-X is shown, which images the effective object field outside the optical axis in the object plane into the off-axis effective image field in the image plane. Here, two real intermediate images IMI1-X and IMI2-X are formed between the object plane and the image plane. The projection objective has a single concave mirror with an upstream connected negative group to support the correction of the color image. The first deflection unit ULE1-X deflects the radiation from the object plane in the direction of the concave mirror. The second deflection unit ULE2-X deflects the radiation from 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. It has a first reflection surface RF1-X, which deflects the radiation from the object in the direction of the second reflection surface RF2-X that follows. It then deflects the radiation in the direction of the concave mirror. The two reflective surfaces can be arranged on separate independent mirrors, preferably constructed on a common support element, in order to fix the opposite orientation. There are two intermediate images and a total of four reflections between the object plane and the image plane, so that the sum of the intermediate images and the reflections is an even number. Thus, in conventional systems of this type (cf. Fig.11A ) in order to avoid an existing image flip. As an alternative, the first deflection unit can also be single-stage and the second deflection unit two-stage. As in conventional systems, the deflection mirror is arranged optically in the vicinity of the associated intermediate image, i.e. in the region close to the field.

[0145] The use of a two-stage reflective deflection unit of the type described in the present application is not limited to the exemplary embodiments. Such a deflection unit can also be used in a projection objective which generates only an intermediate image between the object plane and the image plane or generates a direct image without an intermediate image. The two-stage reflective deflection unit can be arranged after a plane mirror connected upstream and / or before a deflection mirror connected downstream in the projection beam path.

[0146] The following table summarizes the specific specifications of the two embodiments. Tables 1 and 1A apply to Fig. 9 Tables 2 and 2A are applicable to an embodiment that meets NA=0.3 and has no double optical path between the deflection unit and the concave mirror, which is not shown in the figure.

[0147] The specific specifications for the individual designs are summarized in a table in tabular form. Here, the column "SURF" indicates the number of the refractive or otherwise marked surface, the column "RADIUS" indicates the radius r of the surface (in mm), the column "THICKNESS" indicates the distance d (in mm) between the surface and the subsequent surface, which is called the thickness, and the column "MATERIAL" indicates the material of the optical component. The columns "INDEX1", "INDEX2" and "INDEX3" indicate the refractive index of the material at wavelengths of 365.5 nm (INDEX1), 364.5 nm (INDEX2) and 366.5 nm (INDEX3). The column "SEMIDIAM" indicates half of the available free radius or free optical diameter of the lens or optical element (in mm). The radius r = 0 (in the column "RADIUS") corresponds to a flat surface (i.e., planar). Some optical surfaces are aspherical. The table with the suffix "A" gives the corresponding aspherical data, where the aspherical surface is calculated according to the following rules:

[0148]

[0149] Here, the inverse of the radius represents the surface curvature, and h represents the distance of the surface point from the optical axis (i.e., the ray height). Thus, p(h) gives the arrow height, i.e., the distance of the surface point from the surface vertex in the z direction (the direction of the optical axis). The coefficients K, C1, C2, ... are shown in the table with the suffix "A".

[0150] Table 1

[0151]

[0152]

[0153] Table 1A

[0154]

[0155] surface

[0156]

[0157] Table 3A

[0158]

Claims

1. A catadioptric projection objective lens, for imaging a pattern arranged in an object plane (OS) of the projection objective lens into an image plane of the projection objective lens parallel to the object plane, the catadioptric projection objective lens comprising: a plurality of optical elements, which include a plurality of lenses and a concave mirror (CM) and are arranged between the object plane (OS) and the image plane (IS) along the optical axis, The projection objective (PO) is designed as a dual-field projection objective and is designed to image a first effective object field (OF1) arranged in the object plane outside the optical axis along a first projection optical path (RP1) in a first effective image field (IF1) located in the image plane outside the optical axis, and simultaneously image a second effective object field (OF2) arranged in the object plane outside the optical axis and opposite to the first object field relative to the optical axis along a second projection optical path (RP2) in a second effective image field (IF2) located in the image plane outside the optical axis, and Each projection optical path comprises a first deflection unit (ULE1) and a second deflection unit (ULE2), the first deflection unit being used to deflect radiation from the object plane (OS) to a concave mirror, and the second deflection unit being used to deflect radiation from the concave mirror in the direction of the image plane (IS); It is characterized in that these optical elements constitute a first lens component (OP1), a second lens component (OP2) and a third lens component (OP3), the first lens component is used to image each effective object field (OF1, OF2) of the object plane into a first real intermediate image (IMI1), the second lens component is used to generate a second real intermediate image (IMI2) using radiation from the first lens component (OP1), and the third lens component is used to image the second real intermediate image (IMI2) in the image plane (IS), and A concave mirror (CM) of a projection light path is arranged in the region of a pupil plane (P2) between the first intermediate image and the second intermediate image, 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).

2. The projection objective according to claim 1, characterized in that The lenses are arranged along a first section (OA1) of the optical axis, the first section extending coaxially with respect to each other and perpendicular to the object plane (OS) and the image plane (IS); The concave mirrors (CM1, CM2) are arranged on mutually opposite sides of the first section and define a second section (OA2) of the light-emitting axis, wherein the second section together with the first section defines an axis-emitting plane; The optical elements are arranged symmetrically with respect to a symmetry plane (SYM) and are configured to extend perpendicularly with respect to the axial plane through the first section (OA1); and The deflection units (ULE1, ULE2) are each arranged on a side of the symmetry plane (SYM) facing the associated concave mirror.

3. The projection objective according to claim 2, characterized in that The concave mirrors are arranged coaxially with respect to one another on mutually opposite sides of the first section and define a second section oriented perpendicularly to the first section.

4. The projection objective according to any one of the preceding claims, characterized in that The first deflection unit (ULE1) and the second deflection unit (ULE2) respectively have a first reflection surface (RF1) and an adjacent second reflection surface (RF2), wherein these reflection surfaces are inclined at different inclination angles relative to the symmetry plane around an inclination axis extending perpendicularly to the first segment and the second segment, the first reflection surface (RF1) is arranged to deflect radiation from the object plane (OS) to the second reflection surface (RF2), and the second reflection surface is arranged to deflect radiation from the first reflection surface toward the image plane (IS).

5. The projection objective according to claim 4, characterized in that The inclination angles of the first reflection surface and the second reflection surface are preferably matched to each other, so that the radiation appearing on the first reflection surface and the second reflection surface parallel to the optical axis on the incident side is deflected at the same angle.

6. The projection objective according to any one of the preceding claims, characterized in that The first deflection unit (ULE1) and the second deflection unit (ULE2) are arranged in a region where the value of the subaperture ratio SAR is less than 0.

3.

7. The projection objective according to any one of the preceding claims, characterized in that The first lens component has a first imaging ratio β1, and its applicable condition is 0.5≤|β1|≤2.0, wherein preferably, the applicable condition is |β1|≤1,2, and / or it is characterized in that the projection objective has a reduced imaging ratio and the first lens component produces at most half the reduction.

8. The projection objective according to any one of the preceding claims, characterized in that The numerical aperture on the image side is less than 0.5, wherein the numerical aperture is preferably in the range of 0.2 to 0.

4.

9. The projection objective according to any one of the preceding claims, 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 an even number.

10. A catadioptric projection objective lens, for imaging a pattern arranged in an object plane (OS) of the projection objective lens into an image plane of the projection objective lens parallel to the object plane, the catadioptric projection objective lens comprising: a plurality of optical elements, which include a plurality of lenses and a concave mirror (CM) and are arranged along the optical axis between the object plane (OS) and the image plane (IS), so that an effective object field (OF1) arranged in the object plane outside the optical axis is imaged in an effective image field (IF1) located in the image plane outside the optical axis along a projection optical path (RP1), At least one two-stage reflection deflection unit is arranged in the projection optical path, and the deflection unit has a first reflection surface (RF1) and an adjacent second reflection surface (RF2), wherein the first reflection surface (RF1) is arranged to deflect radiation from the object plane (OS) to the second reflection surface (RF2), and the second reflection surface (RF2) is arranged to deflect radiation from the first reflection surface toward the image plane (IS).

11. The projection objective according to claim 10, characterized in that A first deflection unit (ULE1) and a second deflection unit (ULE2) are arranged in the projection optical path, the first deflection unit is used to deflect radiation from the object plane (OS) to a concave mirror, and the second deflection unit is used to deflect radiation from the concave mirror toward the image plane (IS), and the first deflection unit (ULE1) and / or the second deflection unit (ULE2) are constructed as two-stage reflection deflection units.

12. The projection objective according to claim 10, characterized in that One of the deflection units is designed as a two-stage reflective deflection unit and the other deflection unit is designed as a plane mirror.

13. A projection exposure apparatus for exposing a radiation-sensitive substrate arranged in the region of an image plane of a projection objective using at least one image of a pattern of a mask arranged in the region of an object plane of the projection objective, the projection exposure apparatus comprising: an exposure system (ILL) for receiving light from a separate radiation source and for forming exposure radiation which exposes a first effective object field arranged in the object plane outside the optical axis of the projection objective and simultaneously exposes a second effective object field arranged in the object plane outside the optical axis and lying opposite the first effective object field; A catadioptric projection objective lens, which is designed to image the first effective object field along a first projection optical path in a first effective image field outside the optical axis and located in the image plane, and simultaneously image the second effective object field along a second projection optical path in a second effective image field outside the optical axis and located in the image plane; means for holding the mask between the exposure system and the projection objective so that the mask is arranged in the region of the object plane of the projection objective; means for holding a substrate so that a radiation-sensitive surface of the substrate is arranged in the region of an image plane of the projection objective; Characterized in that the projection objective (PO) is designed according to any one of Claims 1 to 12.

14. The projection exposure apparatus according to claim 13, characterized in that The exposure system comprises: a refractive pupil shaping unit (PFU) for receiving light from the primary light source (LS) and for forming a two-dimensional intensity distribution in a pupil shaping surface (PUP) of the exposure system, and a refractive field shaping system (FFS) optically connected downstream of the pupil shaping unit and having a homogenization unit (HOM) for homogenizing the light received by the pupil shaping unit and for splitting the exposure light into a first exposure radiation beam (SB1) and a second exposure radiation beam (SB2), Preferably, the homogenization unit (HOM) comprises an integrating column device or a first grid device (RA1) and a second grid device (RA2), The integrating rod device (ISA) comprises an input integrating rod (IE) having an incident surface (EF1) and an exit surface (AF1), a first output integrating rod (IA1) optically coupled to a first sub-surface (TF1) of the exit surface (AF1), and a second output integrating rod (IA2) optically coupled to a second sub-surface (TF2) of the exit surface (AF1), wherein the exit surface (AF2-1) of the first output integrating rod is assigned to a first exposure field (ILF1), and the exit surface (AF2-2) of the second output integrating rod is assigned to a second exposure field (ILF2); and The first grid arrangement (RA1) has first refractive grid elements (RE1) for receiving light of a two-dimensional intensity distribution and for forming a grid arrangement of secondary light sources (SL1, SL2, ...), and the second grid arrangement (RA2) connected downstream has second refractive grid elements (RE2) for receiving light of the secondary light sources (SL1, SL2) and for at least partially superimposing the light of the secondary light sources in the exit surface, Each first grid element (RE1) forms an optical channel, and each second grid element (RE2) is equipped with two adjacent first grid elements (RE1) and is formed by a lens element, wherein the lens element has a first segment (AB1) located in the first optical channel and a second segment (AB2) located in the second optical channel, and the segments have different surface shapes.

15. A projection exposure method for exposing a radiation-sensitive substrate using at least one image of a pattern of a mask, the method comprising the following steps: providing a mask between an exposure system of the projection exposure apparatus and the projection objective, such that the mask is arranged in the region of an object plane of the projection objective; Holding a substrate such that a radiation-sensitive surface of the substrate is arranged in the region of an image plane of the projection objective that is optically narrowed toward the object plane; exposing two exposure areas of the mask by exposure radiation from a separate prismatic light source provided by the exposure system; wherein two exposure radiation beams (BS1, BS2) are formed, wherein a first exposure radiation beam (BS1) is guided along a first exposure optical path to a first exposure field (ILF1) arranged in an exit surface (ES) of an exposure system outside the optical axis of a projection objective, and simultaneously a second exposure radiation beam (BS2) is guided along a second exposure optical path to a second exposure field (ILF) arranged in the exit surface opposite to the first exposure field (ILF1) with respect to the optical axis (AX) and outside the optical axis; The part of the pattern located in the exposure field is projected onto an associated image field on the substrate by means of a projection objective, Therein, a projection objective according to any one of claims 1 to 12 and / or a projection exposure apparatus according to claim 13 or 14 is used.

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