Projection optical unit and projection exposure system

Abstract

The invention relates to a projection optical unit (10), in particular an EUV projection optical unit, comprising a housing structure (128), wherein the housing structure (128) has an interior space (140), which is at least partially enclosed by the housing structure (128), and a support section (146, 148, 150, 152), which extends outwardly from the housing structure (128) away from the interior space (140), wherein an optical element (102) of the projection optical unit (10) can be arranged at least partially within the interior space (140), wherein the housing structure (128) is a one-piece component, and wherein the housing structure (128) has a dimension in at least one spatial direction (x, y, z) of at least 2900 mm.

Description

[0001] The present invention relates to a projection optical unit, specifically an EUV projection optical unit, and to a projection exposure apparatus for EUV lithography having such a projection optical unit.

[0002] The contents of priority application DE 10 2024 200 608.4 are incorporated herein by reference in their entirety.

[0003] Microlithography is used to produce microstructured components, such as integrated circuits. Microlithography processes are performed using lithography equipment equipped with an illumination system and a projection system. An image of a mask (photomask) illuminated by the illumination system is then projected onto a substrate (e.g., a silicon wafer) via the projection system. This substrate is coated with a photosensitive layer (photoresist) and arranged in the image plane of the projection system to transfer the mask structure to the photosensitive coating on the substrate.

[0004] In an effort to achieve increasingly smaller structures in the production of integrated circuits, EUV lithography equipment is currently being developed that uses light with wavelengths ranging from 0.1 nm to 30 nm, particularly 13.5 nm. Since most materials absorb light at this wavelength, such EUV lithography equipment requires the use of reflective optical units (i.e., mirrors) instead of the refractive optical units (i.e., lens elements) used previously.

[0005] As mentioned above, the gradual development of photolithography equipment towards higher numerical apertures to enable imaging of smaller structures on substrates tends to produce increasingly larger optical units. However, this also necessitates that the housings accommodating these optical units be made larger. This required increase in the size of such housings may necessitate linking multiple sub-components together to form the housing. This linking of sub-components can negatively impact manufacturing costs, product performance, and lifespan. Improvements are needed.

[0006] In this context, the object of the present invention is to provide an improved projection optical unit.

[0007] Therefore, a projection optical unit, particularly an EUV projection optical unit, is proposed. The projection optical unit includes a housing structure having an internal space and support sections, the housing structure at least partially enclosing the internal space, the support sections extending outward from the housing structure away from the internal space, wherein optical elements of the projection optical unit can be at least partially arranged within the internal space, wherein the housing structure is a single-piece component, and wherein the housing structure has a dimension of at least 2,900 mm in at least one spatial direction.

[0008] Because the shell structure is a single, integrated component, the need to join different sub-components used to form the shell structure can be eliminated. Therefore, for example, the surface area of ​​the shell structure can be minimized to better ensure vacuum and cleanliness requirements within the EUV reference frame. The integrated design of the shell structure also reduces the number of joints and interfaces, resulting in a reduced risk of leakage and corrosion. Furthermore, due to the integrated construction, force flow can be dissipated in an optimized manner, considering the size of the structure.

[0009] The housing structure can be, for example, part of the housing of a projection optics unit. A projection optics unit is an optical system. Therefore, the terms "projection optics unit" and "optical system" can be used interchangeably as needed in this context. An optical system is part of a projection exposure apparatus used for EUV lithography. The housing can be a so-called load-bearing frame (or force frame) of the optical system. The housing can consist of multiple housing structures (e.g., two housing structures).

[0010] The shell structure is preferably shell-shaped or channel-shaped and encloses an internal space, such that the internal space is arranged within the shell structure. However, this does not preclude the internal space from opening towards the surrounding area of ​​the shell structure. For example, the internal space may be at least partially enclosed by the base of the shell structure, two opposing side walls, a rear wall, and a front wall.

[0011] The optical element is particularly a mirror, preferably an EUV mirror. However, the optical element can also be a lens element. In particular, the optical element can be suspended in or mounted on the housing structure. In its mounted state, the optical element is at least partially arranged within the internal space. However, this does not preclude the optical element or sections thereof from protruding beyond the internal space and into the surrounding environment of the housing structure.

[0012] The shell structure being "one-piece" or "monolithic" should be understood in the present context to specifically mean that the shell structure is not constructed from multiple sub-components placed together but forms a single component. Therefore, the shell structure can also be referred to as monolithic. Particularly preferred is that the shell structure is a monolithic material component. In the present context, "monolithic material" means that the shell structure is produced from the same material throughout. Support sections are also formed integrally with the shell structure, particularly monolithic in material. The shell structure can alternatively have designs that allow it to be converted into a welded construction.

[0013] Sub-components can be connected to the shell structure via material bonding. In the case of material bonding, the connected parts are held together by atomic or molecular forces. Material bonding is a non-releasable connection, which can only be separated by breaking the connecting device and / or the connected parts. Material bonding can be achieved, for example, by welding or fusion. In particular, the shell structure is made of metallic materials. Light metals, preferably aluminum alloys, can be used, for example, as materials for the shell structure.

[0014] The support section can be block-shaped or cuboid. The support section preferably extends outward from the aforementioned sidewall away from the internal space. With the aid of the support section, the shell structure can be supported or mounted on suitable supports, preferably on air supports, particularly on so-called air mounts. Therefore, the support section is used to support the shell structure. Therefore, the support section can also be referred to as a support section. Thus, the terms "support section" and "supporting section" can be used interchangeably as needed in the present context.

[0015] The shell structure is preferably assigned a coordinate system having a first spatial direction, a width direction or x-direction, a second spatial direction, a length direction or y-direction, and a third spatial direction, a height direction or z-direction. These directions are perpendicular to each other. For example, when viewed along the y-direction, the shell structure has a dimension of at least 2,900 mm. Along the x-direction, the shell structure can have a dimension of at least 1,000 mm, and similarly, along the z-direction, a dimension of at least 500 mm. In other words, the shell structure can have a length greater than 2,900 mm, a width greater than 1,000 mm, and a height greater than 500 mm.

[0016] According to one embodiment, the shell structure has reinforcing ribs.

[0017] The number and arrangement of stiffening ribs depend on the requirements. For example, two stiffening ribs may be provided. However, in principle, any number of stiffening ribs may be provided. Stiffening ribs increase the rigidity of the shell structure. "Stiffness" in this context should be understood specifically as the resistance of the body (in this case, the shell structure) to elastic deformation imposed by external loads, particularly forces or moments, and indicates the relationship between the load on the body and the deformation of the body. Stiffness is determined by the material and geometry of the body. Stiffening ribs are typically formed integrally or monolithically with the shell structure.

[0018] According to another embodiment, the reinforcing ribs extend through the interior space.

[0019] This specifically refers to reinforcing ribs arranged within the internal space. These reinforcing ribs can, for example, form a frame-like structure within the internal space that strengthens the shell structure. The reinforcing ribs can be connected to each other.

[0020] According to another embodiment, reinforcing ribs connect the first and second sidewalls of the shell structure to each other.

[0021] As described above, in addition to the first and second sidewalls, the shell structure may also have a base, a rear wall, and a front wall. Besides the sidewalls, reinforcing ribs may, for example, connect the rear wall to the front wall. Furthermore, different reinforcing ribs may, for example, connect the sidewalls to each other, connect the front and rear walls to each other, and / or connect the sidewalls to the rear and / or front walls. In this case, the aforementioned frame-like structure with reinforcing ribs is obtained.

[0022] According to another embodiment, the first sidewall and the second sidewall are connected to each other by means of the base, rear wall and front wall of the shell structure.

[0023] The support section, first sidewall, second sidewall, base, rear wall, and front wall form the shell structure as a single, integral component, particularly as a single material component. In this case, the support section is preferably integrally formed with the two sidewalls, particularly as a single material component. Two such support sections can be assigned to each sidewall.

[0024] According to another embodiment, the housing structure also has cooling channels that extend within the housing structure.

[0025] The cooling channel may specifically extend through the first sidewall, second sidewall, base, rear wall, and / or front wall. This specifically means that the cooling channel may be arranged within the first sidewall, second sidewall, base, rear wall, and / or front wall. Furthermore, the cooling channel may also pass through reinforcing ribs. In this case, the cooling channel is arranged within the reinforcing ribs.

[0026] According to another embodiment, the shell structure also has a perforation that penetrates the shell structure.

[0027] Perforations can be provided, for example, on the first sidewall, second sidewall, base, rear wall, and / or front wall. Perforations can serve different functions. For example, perforations reduce the weight of the housing structure. Furthermore, cables and / or liquid delivery lines can be guided through these perforations. Additionally, optical elements or components mounted on optical elements can be at least partially led out of the housing or from the housing structure through the perforations. Moreover, the beam path of the optical system (the path along which illumination radiation passes through the optical system) can pass through at least one perforation or multiple perforations.

[0028] According to another embodiment, the housing structure has a dimension of at least 500 mm in at least one additional spatial direction.

[0029] As described above, this means that the shell structure can have a length greater than 2,900 mm, a width greater than 1,000 mm, and a height greater than 500 mm. Alternatively, for example, the shell structure can also have a length greater than 500 mm, a width greater than 2,900 mm, and a height greater than 1,000 mm. Furthermore, the shell structure can also have a length greater than 1,000 mm, a width greater than 500 mm, and a height greater than 2,900 mm.

[0030] According to another embodiment, the shell structure has an end face, wherein the support section is arranged flush with the end face.

[0031] In the current context, "flush" specifically means that the support section and the end face are located in a common plane. Using the end face, a shell structure can be supported on another shell structure to form a shell. The end face is specifically formed by the side walls, rear wall, front wall, and support section. In other words, the corresponding upper edges or upper sides of the side walls, rear wall, front wall, and support section are located in a common plane, and the end face is also located in this common plane, or the common plane is formed by the end face. The end face is preferably located in or parallel to a plane spanning the x and y directions.

[0032] According to another embodiment, the shell structure has exactly four support sections.

[0033] Exactly two support sections can be assigned to each sidewall of the housing structure. This allows for four-point mounting of the housing structure. However, more than four support sections can also be provided. The support sections can be, for example, block-shaped. Two housing structures can also be connected to each other to form a housing using the support sections. To connect the two housing structures to each other, the support sections have, for example, screw connections and / or pin connections. Precision interfaces with an accuracy of less than 20 μm can be provided on the support sections. These precision interfaces can be used to position the two housing structures abutting against each other to form a housing and / or to position optical elements on the housing structure.

[0034] According to another embodiment, the shell structure is formed in a shell shape.

[0035] In the present context, "shell-shaped" specifically refers to a shell structure that at least partially encloses the aforementioned internal space. However, as mentioned above, the internal space is preferably open to the surrounding area of ​​the shell structure. If two shell structures are placed together to form a shell, the shell preferably completely encloses the internal space of both shell structures. However, this does not preclude access to the internal space from the surrounding area through the aforementioned perforations in the respective shell structures.

[0036] According to another embodiment, the projection optical unit also has optical elements, wherein the optical elements are at least partially arranged within the interior space of the housing structure.

[0037] An optical system can have multiple optical elements. However, only one optical element will be discussed below. The optical element is a mirror, specifically an EUV mirror. The optical element can be suspended in and thus mounted on the housing structure.

[0038] According to another embodiment, the projection optical unit also has at least two housing structures connected to each other, wherein these housing structures together form the housing of the projection optical unit.

[0039] The housing can be a load-bearing frame for an optical system as described above. Preferably, the housing has exactly two housing structures connected to each other. The housing can house the optical elements. This specifically means that the optical elements are arranged within the housing.

[0040] According to another embodiment, the projection optics unit has a sensor frame, wherein the sensor frame is at least partially arranged within the housing.

[0041] Specifically, the sensor frame is arranged within the internal space enclosed by the housing structure. The sensor frame can also be referred to as the sensor coordinate system. The housing can be connected to a fixed reference frame by means of one or more connecting elements. Furthermore, the sensor frame can be connected to the housing by means of one or more connecting elements. The connecting elements may have springs. In this context, "fixed reference frame" should be understood as referring to the region of the optical system that cannot move relative to the housing. The optical element can be adjusted or aligned in six degrees of freedom (specifically three translational and three rotational degrees of freedom) via the actuator unit. In this case, the sensor frame serves as a reference for changes in the relative position of the optical element. The optical element is connected to the housing via the actuator unit. The optical element can be connected to the actuator unit via a connecting element, which in turn is connected to the housing via another connecting element. For example, the target relative position of the optical element is maintained by means of closed-loop and open-loop control units. For this purpose, the closed-loop and open-loop control units can communicate with the actuator unit. The closed-loop and open-loop control units interact with the sensor frame such that, for example, sensor measurement optics are attached to the sensor frame, wherein the closed-loop and open-loop control units actuate the actuator unit based on sensor signals from these sensors in order to maintain the target relative position of the optics.

[0042] Furthermore, a projection exposure apparatus for EUV lithography with such a projection optical unit is proposed.

[0043] The projection exposure equipment is an EUV lithography equipment. EUV stands for "extreme ultraviolet" and indicates the wavelength of working light between 0.1 nm and 30 nm.

[0044] In the present context, "one / one" should not necessarily be interpreted as limited to exactly one / one element. Instead, multiple elements can be provided, such as two, three, or more elements. Any other numbers used herein should also not be construed as a precise limitation on the number of elements stated. More precisely, unless otherwise stated, upward and downward numerical deviations are possible.

[0045] The embodiments and features described for the projection optics unit are applicable to the proposed projection exposure device, and vice versa.

[0046] Further possible embodiments of the present invention include combinations of features or embodiments not explicitly mentioned in the description above or below in conjunction with exemplary embodiments. In such cases, those skilled in the art will also add various aspects as improvements or supplements to the corresponding basic form of the invention.

[0047] Further advantageous configurations and aspects of the invention are the subject of the dependent claims, and also the subject of exemplary embodiments of the invention described below. The invention will now be explained in more detail with reference to the accompanying drawings and preferred embodiments.

[0048] Figure 1 A schematic meridional cross-section of a projection exposure apparatus used for EUV projection lithography is shown. Figure 2 It shows the method for using according to Figure 1 A schematic diagram of an embodiment of the optical system of a projection exposure device; Figure 3 It shows according to Figure 2 A schematic plan view of the optical system; Figure 4 It shows according to Figure 2 Another schematic diagram of the optical system; Figure 5 It shows according to Figure 2 Another schematic diagram of the optical system; Figure 6 It shows the method for using according to Figure 2 A schematic perspective view of one embodiment of the housing structure of an optical system; Figure 7 It shows according to Figure 6 A schematic partial three-dimensional cross-sectional view of the shell structure; Figure 8 It shows according to Figure 6 A schematic plan view of the shell structure; Figure 9 It shows according to Figure 6 A schematic side view of the shell structure; and Figure 10 It shows according to Figure 6A schematic rear view of the shell structure.

[0049] Unless otherwise specified, the same reference numerals are used for identical or functionally equivalent elements in the accompanying drawings. It should also be noted that the illustrations in the drawings are not necessarily drawn to scale.

[0050] Figure 1 An embodiment of a projection exposure apparatus 1 (lithography apparatus), particularly an EUV lithography apparatus, is shown. In addition to the light source or radiation source 3, one embodiment of the illumination system 2 of the projection exposure apparatus 1 also includes an illumination optics unit 4 for illuminating the object field 5 in the object plane 6. In an alternative embodiment, the light source 3 may also be configured as a module separate from the rest of the illumination system 2. In this case, the illumination system 2 does not include the light source 3.

[0051] The photomask 7 is exposed and arranged in the object field 5. The photomask 7 is held by the photomask holder 8. The photomask holder 8 can be moved by the photomask shift driver 9, especially in the scanning direction.

[0052] Figure 1 A Cartesian coordinate system with x-direction x, y-direction y, and z-direction z is illustrated. The x-direction x extends vertically into the plane shown in the figure. The y-direction y extends horizontally, and the z-direction z extends vertically. The scan direction is along... Figure 1 The object extends in the y-direction (y). The object extends in the z-direction (z) perpendicular to the object plane (6).

[0053] The projection exposure apparatus 1 includes a projection optics unit 10. The projection optics unit 10 is used to image the object field 5 onto an image field 11 in an image plane 12. The image plane 12 extends parallel to the object plane 6. Alternatively, an angle other than 0° may exist between the object plane 6 and the image plane 12.

[0054] The structure on the photomask 7 is imaged onto the photosensitive layer of the wafer 13, which is arranged in the region of the image field 11 in the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be moved by a wafer shift driver 15, specifically along the y-direction. The shifting of the photomask 7 by the photomask shift driver 9 and the shifting of the wafer 13 by the wafer shift driver 15 can be implemented synchronously with each other.

[0055] Light source 3 is an EUV radiation source. Light source 3 specifically emits EUV radiation 16, also referred to below as used radiation, illumination radiation, or irradiation light. The wavelength of the radiation 16 used is specifically in the range of 5 nm to 30 nm. Light source 3 can be a plasma source, such as an LPP source (or laser-generated plasma, plasma generated by means of a laser) or a DPP source (or gas discharge-generated plasma). The light source can also be a synchrotron-based radiation source. Light source 3 can be a free-electron laser (or FEL).

[0056] Illumination radiation 16 emitted from light source 3 is focused by light collector 17. Light collector 17 may be a light collector having one or more elliptical and / or hyperboloidal reflective surfaces. The at least one reflective surface of light collector 17 may be illuminated by illumination radiation 16 at grazing incidence (or GI) (i.e., at an angle of incidence greater than 45°) or normal incidence (or NI) (i.e., at an angle of incidence less than 45°). Light collector 17 may be structured and / or coated, on the one hand to optimize the reflectivity of the light collector to the radiation used, and on the other hand to suppress external light.

[0057] Downstream of the light collector 17, the illumination radiation 16 propagates through the intermediate focal point in the intermediate focal plane 18. The intermediate focal plane 18 can represent the spacing between the radiation source module with the light source 3 and the light collector 17 and the illumination optical unit 4.

[0058] The illumination optics unit 4 includes a deflector 19 and a first facet mirror 20 disposed downstream of the deflector in the beam path. The deflector 19 may be a planar deflector or alternatively a mirror having a beam influence effect beyond pure deflection. Alternatively or additionally, the deflector 19 may be in the form of a spectral filter that separates the wavelength of light used by the illumination radiation 16 from intrusive light deviating from that wavelength. If the first facet mirror 20 is disposed in the plane of the illumination optics unit 4 that is optically conjugate to the field plane with respect to the object plane 6, then the first facet mirror is also referred to as a field facet mirror. The first facet mirror 20 includes a plurality of individual first facets 21, which may also be referred to as field facets. Figure 1 The text only shows some of these first facets 21 by way of example.

[0059] The first facet 21 can be implemented as a macrofacet, particularly a rectangular facet or a facet with an edge profile that is curved or part of a circle. The first facet 21 can be implemented as a planar facet, or alternatively as a facet with convex or concave curvature.

[0060] As is known, for example, from DE 10 2008 009 600 A1, the first facet 21 itself can also be composed of multiple individual mirrors, particularly multiple micromirrors, in their respective cases. The first facet mirror 20 can be specifically configured as a microelectromechanical system (MEMS system). For details, refer to DE 10 2008 009 600 A1.

[0061] Between the light collector 17 and the deflector 19, the illumination radiation 16 travels horizontally, that is, along the y-direction.

[0062] In the beam path of the illumination optical unit 4, the second small mirror 22 is arranged downstream of the first small mirror 20. If the second small mirror 22 is arranged in the pupil plane of the illumination optical unit 4, it is also called the pupil small mirror. The second small mirror 22 can also be arranged at a distance from the pupil plane of the illumination optical unit 4. In this case, the combination of the first small mirror 20 and the second small mirror 22 is also called a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1, EP 1 614 008 B1 and US 6,573,978.

[0063] The second facet 22 includes multiple second facets 23. In the case of a pupil facet, the second facet 23 is also referred to as the pupil facet.

[0064] The second facet 23 can also be a macrofacet, which may, for example, have circular, rectangular, or hexagonal boundaries, or alternatively, be a facet composed of micromirrors. See also DE 10 2008 009600 A1 in this regard.

[0065] The second facet 23 may have a planar reflective surface, or alternatively, a reflective surface with convex or concave curvature.

[0066] The illumination optics unit 4 thus forms a two-faceted system. This basic principle is also known as a fly-eye condenser (or fly-eye integrator).

[0067] It may be advantageous to arrange the second small mirror 22 imprecisely in a plane that is optically conjugate to the pupil plane of the projection optics unit 10. In particular, the second small mirror 22 may be arranged at an angle relative to the pupil plane of the projection optics unit 10, as described, for example, in DE 10 2017 220 586 A1.

[0068] With the aid of the second facet mirror 22, each of the first facets 21 is imaged into the object field 5. The second facet mirror 22 is the last beam shaping mirror in the beam path upstream of the object field 5, or in fact, the last mirror used for illumination radiation 16.

[0069] In another embodiment (not shown) of the illumination optics unit 4, a transfer optics unit may be arranged in the beam path between the second facet mirror 22 and the object field 5. This transfer optics unit is particularly helpful in imaging the first facet 21 into the object field 5. The transfer optics unit may have exactly one mirror, or alternatively two or more mirrors arranged one after another in the beam path of the illumination optics unit 4. The transfer optics unit may specifically include one or two normal incident mirrors (NI mirrors) and / or one or two grazing incident mirrors (GI mirrors).

[0070] exist Figure 1 In the illustrated embodiment, the illumination optical unit 4 has exactly three mirrors downstream of the light collector 17, specifically a deflecting mirror 19, a first small mirror 20, and a second small mirror 22.

[0071] In another embodiment of the illumination optical unit 4, the deflection mirror 19 is not required, so the illumination optical unit 4 can have exactly two mirrors downstream of the light collector 17, specifically a first facet mirror 20 and a second facet mirror 22.

[0072] Imaging the first facet 21 onto the object plane 6 via the second facet 23 or using the second facet 23 and the transfer optical unit is usually only an approximate imaging.

[0073] The projection optics unit 10 includes a plurality of mirrors Mi, which are sequentially numbered according to their arrangement in the beam path of the projection exposure device 1.

[0074] exist Figure 1 In the example shown, the projection optics unit 10 includes six mirrors M1 to M6. Similarly, alternatives with four, eight, ten, twelve, or any other number of mirrors Mi are possible. The projection optics unit 10 is a double-shielded optics unit. The penultimate mirror M5 and the last mirror M6 each have a through-hole for illumination radiation 16. The image-side numerical aperture of the projection optics unit 10 is greater than 0.5 and can also be greater than 0.6, and can be, for example, 0.7 or 0.75.

[0075] The reflective surface of mirror Mi can be implemented as a freeform surface without an axis of rotational symmetry. Alternatively, the reflective surface of mirror Mi can be designed as an aspherical surface with exactly one axis of rotational symmetry. Like the mirror of illumination optics unit 4, mirror Mi can have a highly reflective coating for illumination radiation 16. These coatings can be designed as multilayer coatings, particularly with alternating layers of molybdenum and silicon.

[0076] The projection optics unit 10 has a large object-image offset in the y-direction y-coordinate between the center of the object field 5 and the center of the image field 11. This object-image offset in the y-direction y-coordinate can be approximately the same as the z-distance between the object plane 6 and the image plane 12.

[0077] The projection optical unit 10 can have a particularly modified form. Specifically, the projection optical unit has different imaging scales βx and βy in the x-direction and the y-direction. The two imaging scales βx and βy of the projection optical unit 10 are preferably (βx, βy) = (+ / -0.25, + / -0.125). A positive imaging scale β indicates imaging without image flipping. A negative imaging scale β indicates imaging with image flipping.

[0078] Therefore, the projection optical unit 10 reduces its size in the x-direction (that is, in the direction perpendicular to the scanning direction) by a ratio of 4:1.

[0079] The projection optical unit 10 reduces its size by 8:1 in the y-direction (that is, in the scanning direction).

[0080] Other imaging scales are also possible. Imaging scales with the same sign and the same absolute value in both the x and y directions are also possible, for example, with absolute values ​​of 0.125 or 0.25.

[0081] Depending on the embodiment of the projection optics unit 10, the number of intermediate image planes in the x-direction (x) and y-direction (y) of the beam path between the object field 5 and the image field 11 may be the same or different. Examples of projection optics units with different numbers of such intermediate images in the x-direction (x) and y-direction (y) are known from US 2018 / 0074303 A1.

[0082] In each case, one of the second facets 23 is assigned to exactly one of the first facets 21 to form an illumination channel for illuminating the object field 5. This can produce illumination specifically according to Köhler's principle. The far field is decomposed into multiple object fields 5 by means of the first facets 21. The first facets 21 produce multiple images with intermediate focal points on the second facets 23 respectively assigned to them.

[0083] For the purpose of illuminating the object field 5, each of the first facets 21 is imaged onto the photomask 7 via an assigned second facet 23, wherein the images overlap each other. The illumination of the object field 5 is particularly made as uniform as possible. The object field preferably has a uniformity error of less than 2%. Field uniformity can be achieved by overlapping different illumination channels.

[0084] The illumination of the entrance pupil of the projection optical unit 10 can be geometrically defined by the arrangement of the second facets 23. The intensity distribution in the entrance pupil of the projection optical unit 10 can be set by selecting the illumination channels, particularly a subset of the second facets 23 that guide the light. This intensity distribution is also referred to as the illumination setup or illumination pupil filling.

[0085] The same preferred pupil uniformity can be achieved in the region where the illumination pupil of the illumination optical unit 4 is illuminated in a defined manner by reallocating the illumination channel.

[0086] The following describes further aspects and details of the illumination of the object field 5, particularly the entrance pupil of the projection optical unit 10.

[0087] The projection optics unit 10 may specifically have a concentric entrance pupil. The concentric entrance pupil may be accessible. Or it may be inaccessible.

[0088] The entrance pupil of the projection optics unit 10 is often not precisely illuminated by the second small mirror 22. When imaging the projection optics unit 10, the aperture rays typically do not intersect at a single point, as the projection optics unit images the center of the second small mirror 22 onto the wafer 13 telecentrically. However, it is possible to find a region where the distance between pairs of defined aperture rays becomes minimal. This region represents the entrance pupil or the region conjugate to it in real space. In particular, this region has a finite curvature.

[0089] It is possible that the projection optics unit 10 has different relative positions of the entrance pupils for the tangential beam path and the sagittal beam path. In this case, the imaging element, particularly the optical component of the transmission optics unit, should be positioned between the second small mirror 22 and the photomask 7. This optical element allows for consideration of the different relative positions of the tangential and sagittal entrance pupils.

[0090] exist Figure 1 In the arrangement of components of the illumination optical unit 4 shown, the second small mirror 22 is arranged in the region conjugate with the entrance pupil of the projection optical unit 10. The first small mirror 20 is arranged to be inclined relative to the object plane 6. The first small mirror 20 is arranged to be inclined relative to the arrangement plane defined by the deflection mirror 19. The first small mirror 20 is arranged to be inclined relative to the arrangement plane defined by the second small mirror 22.

[0091] Figure 2 A schematic diagram of one embodiment of an optical system 100 for a projection exposure device 1 is shown. Figure 3 A schematic plan view of the optical system 100 is shown. Reference is also made below. Figure 2 and Figure 3 .

[0092] Optical system 100 may be the projection optical unit 10 as described above, or a part of such projection optical unit 10. Therefore, optical system 100 may also be referred to as a projection optical unit. However, optical system 100 may also be the illumination system 2 as described above, or a part of such illumination system 2. Therefore, optical system 100 may also be alternatively referred to as an illumination system. However, it is assumed below that optical system 100 is the projection optical unit 10 or a part of such projection optical unit 10. Optical system 100 is suitable for EUV lithography. However, optical system 100 may also be suitable for DUV lithography.

[0093] Optical system 100 may include multiple optical elements 102, however, Figure 2 and Figure 3 Only one optical element is shown in the diagram. Therefore, only one optical element 102 will be discussed below. Optical element 102 can be one of mirrors M1 to M6. Optical element 102 includes an optically effective surface 104, such as a mirror surface. The optically effective surface 104 can be... Figure 2 The orientation is upward or downward.

[0094] An optically effective surface 104 is disposed on the front side 106 or the back side 108 of the optical element 102. It is assumed below that the optically effective surface 104 is disposed on the front side 106. The optically effective surface 104 can be achieved by means of a coating applied to the front side 106. The optically effective surface 104 is a mirror.

[0095] The optically effective surface 104 is suitable for reflecting illumination radiation 16, particularly EUV radiation, during operation of the optical system 100. According to... Figure 3 In the planar diagram, the optically effective surface 104 can have an oval or elliptical geometry. According to... Figure 3 In the plan view, the optical element 102 may have a triangular geometry. However, in principle, the geometry of the optical element 102 is determined as needed.

[0096] Optical element 102 has a back surface 108, facing away from the optically effective surface 104 or the front surface 106. The back surface 108 has no defined optical properties. This specifically means that the back surface 108 is not a mirror and therefore does not have reflective properties. However, this is not absolutely necessary. As mentioned above, the optically effective surface 104 can also be disposed on the back surface 108.

[0097] The optical element 102 or the optically effective surface 104 has six degrees of freedom, specifically three translational degrees of freedom in the first spatial direction (x-direction), the second spatial direction (y-direction), and the third spatial direction (z-direction), and three rotational degrees of freedom about the x-direction, the y-direction, and the z-direction, respectively. This means that the position and orientation of the optical element 102 or the optically effective surface 104 can be determined or described by means of these six degrees of freedom.

[0098] The “position” of optical element 102 or optical effective surface 104 should be understood to specifically refer to its coordinates relative to the x-direction, y-direction, and z-direction, or the coordinates of a measurement point disposed on optical element 102. The “orientation” of optical element 102 or optical effective surface 104 should be understood to specifically refer to its tilt relative to the three spatial directions x, y, and z. This means that optical element 102 or optical effective surface 104 may be tilted around the x-direction, y-direction, and / or z-direction.

[0099] This results in six degrees of freedom for the position and orientation of the optical element 102 or the optical effective surface 104. The “relative position” of the optical element 102 or the optical effective surface 104 encompasses both its position and its orientation. Therefore, the term “relative position” can be replaced by the phrase “position and orientation”, and vice versa.

[0100] Figure 2 Solid lines indicate the actual relative position IL of optical element 102 or optical effective surface 104, while dashed lines and reference numerals 102' and 104' indicate the target relative position SL of optical element 102 or optical effective surface 104. Optical element 102 can move from its actual relative position IL to its target relative position SL, and vice versa. For example, optical element 102 at the target relative position SL satisfies certain optical specifications or requirements that optical element 102 at its actual relative position IL does not meet.

[0101] To move optical element 102 from its actual relative position IL to its target relative position SL, optical system 102 can be adjusted or aligned. In this context, "adjustment" or "alignment" should be understood to specifically mean changing the relative position of optical element 102. For example, optical element 102 can move from its actual relative position IL to its target relative position SL, and vice versa. Therefore, adjustment or alignment of optical element 102 can be performed on all six of the aforementioned degrees of freedom.

[0102] Figure 4 Another schematic diagram of the optical system 100 is shown.

[0103] In addition to the optical element 102, the optical system 100 also has a housing 110 and a sensor frame 112 (or sensor coordinate system). The housing 110 is specifically the so-called load support frame (or force frame) of the optical system 100. Therefore, the terms "housing" and "load support frame" may be used interchangeably here as needed.

[0104] The housing 110 is connected to the fixed reference frame 116 by means of connecting elements 114. Multiple such connecting elements 114 may be present. The sensor frame 112 is connected to the housing 110 by means of connecting elements 118. Multiple such connecting elements 118 may be present. The housing 110 thus supports the sensor frame 112. The connecting elements 114 and 118 may have springs. In this context, "fixed reference frame" should be understood to mean the area of ​​the optical system 100 that cannot move relative to the housing 110.

[0105] As described above, the optical system 100 may have multiple optical elements 102; however, Figure 4 Only one optical element is shown. Optical element 102 can be adjusted or aligned in the aforementioned six degrees of freedom by means of actuator unit 120. Sensor frame 112 serves as a reference for changes in the relative position of optical element 102. Optical element 102 is connected to housing 110 via actuator unit 120. Optical element 102 can be connected to actuator unit 120 by means of coupling element 122, which in turn is connected to housing 110 by means of coupling element 124.

[0106] For example, the target relative position SL of the optical element 102, as described above, is maintained by means of a closed-loop and open-loop control unit 126. For this purpose, the closed-loop and open-loop control unit 126 can communicate with the actuator unit 120. The closed-loop and open-loop control unit 126 interacts with the sensor frame 112 such that sensors mounted on the sensor frame 112 measure the optical element 102, wherein, based on sensor signals from these sensors, the closed-loop and open-loop control unit 126 actuates the actuator unit 120 to maintain the target relative position SL of the optical element 102.

[0107] Figure 5 Another schematic diagram of the optical system 100 is shown.

[0108] Optical system 100 Figure 5 The diagram is shown in a greatly simplified manner, so optical elements 102 are not shown, for example. The optical system 100 can be configured such that the sensor frame 112 is at least partially arranged within the housing 110. The sensor frame 112 can also be placed entirely within the housing 110. Thus, the housing 110 serves as the outer shell of the sensor frame 112.

[0109] The sensor frame 112 may be at least partially made of ceramic material. The sensor frame 112 may be a single-piece component, particularly a component made entirely of the same material. In the present context, "single-piece" or "one-piece" means that the sensor frame 112 is not composed of different sub-components, but forms a single, integral component. In the present context, "made entirely of the same material" means that the sensor frame 112 is made entirely of the same material throughout.

[0110] As described above, the projection exposure device 1 is progressively developed in the direction of higher numerical aperture to enable imaging of smaller structures on the wafer 13, which tends to produce increasingly larger optical elements 102. However, this also requires the housing 110 to be set to a larger size.

[0111] When multiple sub-components are joined together, this required increase in the size of the housing 110 can negatively impact production costs, product performance, and service life. In developing the projection exposure apparatus 1 with a larger numerical aperture and introducing the larger housing 110 driven by it, the aim is to minimize the extent to which the overall structure of the housing 110 is composed of small parts.

[0112] The housing 110 can be made of metallic materials, particularly light metals. For example, aluminum alloy can be used for the housing 110. The housing 110 is preferably multi-piece. In the present context, "multi-piece" specifically means that the housing 110 can be constructed from at least two sub-components in the form of a housing structure, so that the housing 110 can be constructed around the sensor frame 112. However, in this case, the housing 110 is constructed from as few sub-components as possible. These aforementioned housing structures can be formed in a shell shape, particularly a semi-shell shape.

[0113] Figure 6 A schematic perspective view of an embodiment of the housing structure 128 for housing 110 is shown. Figure 7 A schematic partial three-dimensional cross-sectional view of the shell structure 128 is shown. Figure 8 A schematic plan view of the shell structure 128 is shown. Figure 9 A schematic side view of the housing structure 128 is shown. Figure 10 A schematic rear view of the housing structure 128 is shown. Reference is also made below. Figures 6 to 10 .

[0114] The shell 110 can be composed of multiple such shell structures 128, for example, two shell structures. The shell structures 128 can be constructed identically or differently. In the following discussion, only one shell structure 128 is addressed. The shell structure 128 is assigned a coordinate system as described above, which has a first spatial direction, a width direction or x-direction, a second spatial direction, a length direction or y-direction, and a third spatial direction, a height direction or z-direction. The x, y, and z directions are perpendicular to each other.

[0115] The housing structure 128 is a one-piece component, particularly a component made of a single material. For example, the housing structure 128 is made of aluminum alloy. The housing structure 128 preferably has dimensions of at least 2,900 mm along the y-direction (y), at least 1,000 mm along the x-direction (x), and at least 500 mm along the z-direction (z). In other words, the housing structure 128 can have a length greater than 2,900 mm, a width greater than 1,000 mm, and a height greater than 500 mm.

[0116] The shell structure 128 is shell-shaped and includes a base 130, two sidewalls 132 and 134, a rear wall 136, and a front wall 138, the two sidewalls being arranged parallel to each other. The rear wall 136 may be positioned perpendicular to the base 130. The front wall 138 may be oriented obliquely relative to the base 130. Therefore, the shell structure 128 encloses a cavity or internal space 140. In this case, the internal space 140 is defined by the base 130, sidewalls 132 and 134, rear wall 136, and front wall 138.

[0117] Reinforcing ribs 142 and 144 may extend through the interior space 140. The number and route of the reinforcing ribs 142 and 144 are determined as needed. For example, the reinforcing ribs 142 and 144 may connect the sidewalls 132 and 134 to each other. However, the reinforcing ribs 142 and 144 may also connect the rear wall 136 to the front wall 138. The optical element 102 (not shown) may be at least partially placed within the interior space 140. The reinforcing ribs 142 and 144 may also form a frame-like structure arranged within the interior space 140.

[0118] The reinforcing ribs 142 and 144 increase the stiffness of the shell structure 128. "Stiffness" in this context should be understood specifically as the resistance of the body (in this context, the shell structure 128) to elastic deformation imposed by external loads, particularly forces or moments, and indicates the relationship between the load on the body and the deformation of the body. Stiffness is determined by the material of the body and its geometry.

[0119] Multiple support sections 146, 148, 150, and 152 can be provided on each sidewall 132, 134. The support sections 146, 148, 150, and 152 can be block-shaped. The support sections 146, 148, 150, and 152 extend outward from the sidewalls 132, 134 away from the internal space 140. With the aid of the support sections 146, 148, 150, and 152, the shell structure 128 can be supported on suitable air bearings, particularly on so-called air mounts.

[0120] Regarding the shell structure 128, "integral" specifically means that the base 130, side walls 132, 134, rear wall 136, front wall 138, and / or support sections 146, 148, 150, 152 cannot be separated from each other in a non-destructive manner or without damage. Specifically, in the present case, "integral" means that the shell structure 128 is not composed of different sub-components, but rather that the base 130, side walls 132, 134, rear wall 136, front wall 138, and support sections 146, 148, 150, 152 form a common component, specifically the shell structure 128.

[0121] The shell structure 128 has an end face 153, which abuts against another shell structure (not shown) to form a shell 110. The end face 153 is formed by side walls 132, 134, a rear wall 136, a front wall 138, and support sections 146, 148, 150, 152. In other words, the respective upper edges or upper sides of the side walls 132, 134, rear wall 136, front wall 138, and support sections 146, 148, 150, 152 lie in a common plane, and the end face 153 also lies in this common plane, or the common plane is formed by the end face 153. The end face 153 lies in or is parallel to a plane spanned by the x-direction (x) and y-direction (y).

[0122] Any desired number of perforations 154, 156, 158, and 160 can be provided on the sidewalls 132 and 134. Additionally, a perforation 162 can be provided on the rear wall 136. Another perforation 164 can extend from the rear wall 136 into the base 130. Furthermore, the base 130 can have another perforation 166. The reinforcing ribs 142 and 144 can also have perforations 168 and 170.

[0123] Perforations 154, 156, 158, 160, 162, 164, 166, 168, and 170 can serve different functions. For example, perforations 154, 156, 158, 160, 162, 164, 166, 168, and 170 reduce the weight of the housing structure 128. Furthermore, cables and / or liquid delivery lines can be guided through perforations 154, 156, 158, 160, 162, 164, 166, 168, and 170.

[0124] Additionally, the optical element 102 or components mounted on the optical element 102 may extend from the housing 110 at least partially through the perforations 154, 156, 158, 160, 162, 164, 166, 168, and 170. Moreover, the beam path of the optical system 100 (the illumination radiation 16 passing through the optical system 100 along the beam path) may pass through at least one of the perforations 154, 156, 158, 160, 162, 164, 166, 168, and 170, or through multiple perforations 154, 156, 158, 160, 162, 164, 166, 168, and 170.

[0125] Cooling channel 172 can penetrate housing structure 128, in Figure 9 Only one cooling channel 172 is shown in a very highly schematic manner. The cooling channel 172 may be provided or installed in or on the base 130, side walls 132, 134, rear wall 136, front wall 138 and / or reinforcing ribs 142, 144.

[0126] The shell structure 128 is preferably shell-shaped and has an optimal stiffness / mass ratio for optimizing dynamic performance. The shell structure 128 may preferably have integral reinforcing ribs 142, 144 as described above. For example, the shell structure 128 may be given dimensions (as described above) of a length greater than 2,900 mm multiplied by a width greater than 1,000 mm multiplied by a height greater than 500 mm. The material used is preferably a metallic alloy suitable for lightweight construction, such as an aluminum alloy.

[0127] The housing structure 128 may include an integrated cooling system, for example, in the form of a cooling channel 172. This can be achieved through an integrally integrated cooling channel 172.

[0128] The housing structure 128 has precision interfaces with an accuracy of less than 20 μm. These precision interfaces can be used to vertically position two housing structures 128 to form housing 110 and / or to position optical elements 102 on housing structures 128. The exact form of housing structure 128 (particularly taking into account the elasticity and internal stress state of housing structure 128) is defined by the installation during acceptance measurements.

[0129] The surface area of ​​the monolithic housing structure 128 is minimized to ensure vacuum and cleanliness requirements in EUV environments. The monolithic design minimizes the number of joints and interfaces, thereby reducing the risk of leakage and corrosion.

[0130] The shell structure 128 is configured such that it can potentially be converted into a welded and / or fused construction of the materials bonded together. The shell structure 128 can also be configured such that it can potentially be converted into a construction having sub-components connected to each other by press-fit and / or form-fit devices.

[0131] Although the invention has been described based on exemplary embodiments, it can be modified in various ways.

[0132] List of reference numerals 1. Projection Exposure Equipment 2 Lighting System 3. Light source 4 Illumination Optical Unit 5. Field 6. Object plane 7. Light Mask 8. Photomask holder 9. Mask shifting driver 10 Projection Optical Units 11 Image Field 12 Image plane 13 chips 14. Chip Holder 15. Chip shift driver 16. Lighting radiation 17 light collector 18. Intermediate focal plane 19 Deflecting Mirror 20 First Small Mirror 21 First small noodle 22 Second Small Mirror 23 Second side 100 Optical System 102 Optical Components 102' Optical Components 104 Optical Effective Surface 104' Optical Effective Surface 106 Front 108 Back 110 Housing 112 Sensor Frame 114 Connecting elements 116 Fixed Reference Frame 118 Connecting elements 120 Actuator Unit 122 Connecting elements 124 Connecting elements 126 Closed-loop and open-loop control units 128 Shell Structure 130 base 132 Sidewall 134 Sidewall 136 Rear wall 138 Anterior Wall 140 Interior Space 142 Reinforcing Ribs 144 Reinforcing Ribs 146 Support Section 148 Support Section 150 Support Section 152 Support Section 153 end face 154 perforations 156 piercing 158 piercing 160 piercing 162 perforations 164 perforations 166 piercing 168 piercing 170 piercing 172 Cooling Channel M1 mirror M2 mirror M3 mirror M4 mirror M5 mirror M6 mirror xx direction yy direction The direction of zz.

Claims

1. A projection optical unit (10), particularly an EUV projection optical unit, said projection optical unit having a housing structure (128), wherein, The shell structure (128) has: The interior space (140), the shell structure (128) at least partially enclosing the interior space, and Support sections (146, 148, 150, 152), which extend from the shell structure (128) away from the internal space (140), The optical elements (102) of the projection optical unit (10) can be arranged at least partially within the internal space (140). The shell structure (128) is a one-piece component, and The shell structure (128) has a dimension of at least 2,900 mm in at least one spatial direction (x, y, z).

2. The projection optical unit as described in claim 1, wherein, The shell structure (128) has reinforcing ribs (142, 144).

3. The projection optical unit as described in claim 2, wherein, The reinforcing ribs (142, 144) extend through the interior space (140).

4. The projection optical unit as described in claim 2 or 3, wherein, The reinforcing ribs (142, 144) connect the first sidewall (132) and the second sidewall (134) of the shell structure (128) to each other.

5. The projection optical unit as described in claim 4, wherein, The first sidewall (132) and the second sidewall (134) are connected to each other by means of the base (130), rear wall (136) and front wall (138) of the housing structure (128).

6. The projection optical unit as claimed in any one of claims 1 to 5, the projection optical unit further comprising a cooling channel (172) extending within the housing structure (128).

7. The projection optical unit as claimed in any one of claims 1 to 6, wherein the projection optical unit further comprises a perforation (154, 156, 158, 160, 162, 164, 166, 168, 170) that penetrates the housing structure (128).

8. The projection optical unit as described in any one of claims 1 to 7, wherein, The shell structure (128) has a dimension of at least 500 mm in at least one other spatial direction (x, y, z).

9. The projection optical unit as described in any one of claims 1 to 8, wherein, The shell structure (128) has an end face (153), and wherein the support sections (146, 148, 150, 152) are arranged to be flush with the end face (153).

10. The projection optical unit as claimed in any one of claims 1 to 9, wherein, The shell structure (128) has exactly four support sections (146, 148, 150, 152).

11. The projection optical unit as claimed in any one of claims 1 to 10, wherein, The shell structure (128) is formed in a shell shape.

12. The projection optical unit as claimed in any one of claims 1 to 11, wherein the projection optical unit further comprises the optical element (102), wherein, The optical element (102) is arranged at least partially within the internal space (140) of the housing structure (128).

13. The projection optical unit as claimed in claim 12, wherein the projection optical unit further comprises at least two housing structures (128) connected to each other, wherein, The housing structure (128) together forms the housing (110) of the projection optical unit (10).

14. The projection optical unit as claimed in claim 13, wherein the projection optical unit further comprises a sensor frame (112), wherein, The sensor frame (112) is arranged at least partially within the housing (110).

15. A projection exposure apparatus (1) for EUV lithography, the projection exposure apparatus having a projection optical unit (10) as described in any one of claims 1 to 14.

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