Support structure for a lighting optic of a projection exposure system

Abstract

A support structure (46) open on one side for a lighting optic (15) of a projection exposure system (1) for microlithography has a frame (46) extending in a longitudinal direction (37) with one or more means for increasing the stiffness of the frame (46), wherein ribs (48) and / or planar stiffening elements (47, 42, 43) serve as stiffening means.

Description

[0001] The invention relates to a support structure for an illumination optics system of a projection exposure system. The invention also relates to an illumination optics system, an illumination system, an optical system, and a projection exposure system with a corresponding support structure. Finally, the invention relates to a method for producing a micro- or nanostructured component and a component produced according to the method.

[0002] In illumination systems with a small central angle of incidence (Chief Ray Angle at Object, CRAO), the last optical element in the light path before the reticle is positioned close to the separation plane between the illumination system and the projection optics. A support structure is typically provided for the optical components. Due to the short distance to the separation plane, the space available for the support structure is limited in at least one direction.

[0003] An object of the invention is to improve a support structure for an illumination optics of a projection exposure system.

[0004] This object is achieved in particular by a supporting structure having the claimed features.

[0005] According to one aspect of the invention, the support structure has one or more means for increasing the rigidity of a frame. In particular, a selection of frames, struts, and flat stiffening elements can serve as stiffening means. Partition walls, in particular bulkheads, can also serve as stiffening elements. It has been shown that, in particular, a frame that is open on one side can be specifically stiffened by exploiting surface stiffness and / or arranging frames and / or struts. This can ensure that the support structure meets ever-increasing requirements, in particular with regard to its mechanical and dynamic properties. The support structure, in particular the frame, can in particular be designed such that at least the first natural frequency is greater than 100 Hz, in particular greater than 200 Hz, in particular at least greater than 400 Hz.

[0006] In the following, it is assumed that the projection optics and the illumination optics of a projection exposure system are essentially arranged in disjoint half-spaces separated from each other by a separation plane. The separation plane can be oriented, in particular, perpendicular to the object plane in which the reticle is arranged. The separation plane can be oriented, in particular, parallel to the cross-scan direction.

[0007] In the following, the longitudinal direction is defined as a direction parallel to the principal ray incident on the reticle or a direction perpendicular to the object field. The longitudinal direction generally deviates from a normal to the object plane by a maximum of 30°, in particular 20°, and in particular a maximum of 10°.

[0008] The support structure serves, in particular, to arrange optical components. It serves, in particular, to spatially fix optical components, particularly within the illumination optics. The support structure can be adjustable, in particular, relative to a reference system of the projection exposure system.

[0009] Within the lighting optics, the supporting structure itself can form a reference system.

[0010] According to one aspect, the frame is open at least in sections. The frame can, in particular, be open at least in sections on one side. It can, in particular, be open on a side facing the parting plane, in particular in the transverse direction, i.e., transversely, in particular perpendicularly, to the longitudinal direction.

[0011] The frame can have a total longitudinal extension that is at least as large, in particular at least one and a half times as large, in particular at least twice as large, as its maximum transverse extension. This has proven useful for arranging various components of the illumination optics on the frame.

[0012] The frames and / or stiffening elements can be profiled. They can have a T-profile, an H-profile, a C-profile, a V-profile, or an X-profile in cross-section. This can further increase rigidity in certain directions.

[0013] According to one aspect, the frame is open over at least 50%, in particular at least 60%, in particular at least 70%, in particular at least 80%, in particular at least 90% of its longitudinal extension, in particular completely, to one side in a direction transverse to the longitudinal direction. It can in particular be open in a direction perpendicular to the longitudinal direction.

[0014] The open side can in particular face the dividing plane between the illumination optics and the projection optics.

[0015] In a further aspect, the support structure has an outwardly flat boundary wall on the side to which the frame is open. This allows the support structure to be arranged as close as possible to the dividing plane between the illumination optics and the projection optics. The dividing plane can, in particular, be located in the area of ​​the free surface of the boundary wall.

[0016] According to a further aspect, the frame can have a triangular cross-section, a trapezoidal cross-section, or a pentagonal cross-section, at least in sections in the direction transverse, in particular perpendicular, to the longitudinal direction. Generally, the cross-section of the frame can be polygonal, at least in sections, in the direction transverse, in particular perpendicular, to the longitudinal direction.

[0017] The support structure can then be designed in particular such that the frame has a triangular cross-section at a first position in the longitudinal direction and a trapezoidal cross-section at a second position in the longitudinal direction.

[0018] Particularly high rigidities can be achieved through a triangular and / or trapezoidal and / or pentagonal cross-section.

[0019] A trapezoid is understood here, in particular, to be a trapezoid that is neither rectangular nor parallelogram-shaped. The trapezoid, in particular, has parallel bases of different lengths. This allows shear tolerances to be reduced, and in particular, avoided.

[0020] According to a further aspect, the frame can be bounded in the longitudinal direction by three or more triangular or trapezoidal stiffening plates. In particular, the frame can be bounded in the longitudinal direction by three triangular stiffening plates.

[0021] The frame may have a smallest convex envelope which is bounded exclusively by triangular and quadrangular, in particular trapezoidal, surfaces.

[0022] The frame can, in particular, have a pyramid-shaped smallest convex envelope. The base area of ​​the envelope can be trapezoidal, non-rectangular, or rectangular. The base area, in particular, faces the dividing plane. It can, in particular, be oriented parallel to the dividing plane.

[0023] The apex of the pyramid can be positioned vertically above a boundary edge of the base.

[0024] The flat stiffening elements, in particular the stiffening plates, can be attached in particular tangentially to a frame.

[0025] The frame can be designed with a C-shaped cross-section at least in sections.

[0026] According to a further aspect, the frame can have receptacles for receiving optical components at opposite ends in the longitudinal direction. The optical components can, in particular, be facet mirrors of the illumination optics.

[0027] In general, the frame can have connection points for attachments. The attachments can be, in particular, optical, mechanical, or electrical components, especially modules, of the projection exposure system, especially the illumination optics. The attachments can, in particular, have their own attachment housing.

[0028] By accommodating optical components and / or add-on parts, especially modules, in corresponding receptacles of the frame, the rigidity of the frame can be further improved. It is particularly possible to utilize the rigidity of the optical components and / or add-on parts, especially their housings, to stiffen the supporting structure.

[0029] The corresponding optical components and / or attachments can be permanently or detachably connected to the frame. They can be screwed, clamped, or welded to the frame. All types of positive or non-positive connection techniques are preferred. However, a material connection is not excluded.

[0030] According to a further aspect, one or more stiffening elements can be arranged inside the frame. These can be oriented parallel to the longitudinal direction, perpendicular to the longitudinal direction, or obliquely to the longitudinal direction.

[0031] Struts or plates can serve as stiffening elements. The plates can have recesses. The recesses can be conical, especially parabolic, or elliptical, especially circular.

[0032] Stiffening elements oriented transversely to the longitudinal direction are also called transverse stiffeners or transverse stiffening elements.

[0033] Stiffening elements oriented substantially parallel to the longitudinal direction can serve as separating plates between straight sections in a folded beam path, in particular a tightly folded beam path, of the illumination optics.

[0034] Within the supporting structure, especially within the frame, one, two, three, or more intermediate shelves can be arranged. These can serve as transverse stiffeners.

[0035] The support structure can in particular be designed such that it defines an interior space which is designed such that it enables an obstruction-free radiation path with individual straight sections each having a length of at least 1 m, in particular at least 1.5 m, in particular at least 2 m.

[0036] The subsections can in particular be designed such that they form radiation cone-shaped regions or frustoconical regions between an intermediate focus on the one hand and a first optical element, in particular a first facet mirror on the other hand and / or between the first optical element, in particular a first facet mirror and a second optical element, in particular a second facet mirror and / or between the second optical element, in particular a second facet mirror, a third optical element and / or a fourth optical element and / or the object field.

[0037] The main ray angle and / or the folding angles in the beam path of the illumination optics can in particular be no more than 10°, in particular no more than 7°, in particular no more than 6°.

[0038] It has been shown that the supporting structure according to the invention leads to cost and mass savings. Furthermore, the requirements for manufacturing accuracy could be reduced. The use of welded assemblies has resulted in greater design freedom. The proposed construction with frames and / or intermediate floors facilitates the separation of the supporting structure along these intermediate floors. These also provide the surfaces necessary for connecting the modules (bolted flanges or welded joints). This type of modularization is cost-effective because the raw blocks are smaller, can be manufactured more economically, and generally results in a lower degree of machining (and thus manufacturing effort and time) than with a large monolithic structure.

[0039] The mass saving is due, among other things, to the triangular, trapezoidal or polygonal basic shape, which allows for less voluminous (and thus lighter) supporting structures than the usual rectangular construction.

[0040] Further objects of the invention are to improve an illumination optics, an illumination system, an optical system for a projection exposure apparatus and a projection exposure apparatus.

[0041] These tasks are solved by the corresponding optics / systems with a support structure according to the previous description.

[0042] According to one aspect, at least one optical component can be supported by the support structure. In particular, it is possible to position one or two facet mirrors in the beam path of the illumination optics using the support structure. Due to the mechanical properties of the support structure, the optical components, in particular the mirrors, can be positioned with particular precision. If an arrangement of mirrors, in particular facet mirrors, on the support structure is described below, this is not to be understood as restrictive. The corresponding information can also refer to other optical components.

[0043] It is particularly possible to arrange optical components, in particular one or two facet mirrors, on the frame of the support structure, in particular to connect them to the frame. The two facet mirrors can in particular be arranged opposite one another. The two facet mirrors can in particular be connected to the frame at each end.

[0044] In particular, the support structure is arranged in the illumination optics in such a way that it is open towards the separation plane of the projection optics.

[0045] The support structure can in particular lie completely in a half-space facing away from the projection optics, which is defined by a plane perpendicular to the object plane, in particular parallel to the cross-scan direction.

[0046] According to one aspect, a central angle of incidence may be at most 10°, in particular at most 7°, in particular at most 6°.

[0047] According to a further aspect, a distance of the last optical element in the beam path of the illumination radiation in front of the reticle, in particular of the last mirror, in particular of the second facet mirror, to a plane delimiting the support structure towards the open side can be at most 10 cm, in particular at most 5 cm, in particular at most 3 cm, in particular at most 2 cm, in particular at most 1 cm.

[0048] According to a further aspect, an object-side numerical apparatus may be at least 0.3, in particular at least 0.5.

[0049] In addition to an illumination optics according to the preceding description, an illumination system comprises a radiation source for generating illumination radiation, in particular an EUV radiation source. An EUV radiation source can generate illumination radiation in the EUV range, in particular with a wavelength of less than 30 nm, in particular less than 15 nm.

[0050] An optical system comprises an illumination optics according to the previous description and a projection optics for transferring illumination radiation from the object field into an image field.

[0051] In addition to an illumination system according to the previous description, a projection exposure system has projection optics for transferring illumination radiation from the object field into an image field.

[0052] A method for producing a micro- or nanostructured component is improved by providing a projection exposure system according to the above description. The improved mechanical properties of the support structure allow the micro- or nanostructured components to be produced more precisely.

[0053] According to the method, a reticle with structures to be imaged is arranged in the object field of the illumination optics. The reticle structures are imaged onto a radiation-sensitive layer of a wafer arranged in the image field of the projection optics using illumination radiation, particularly in the EUV range. Further details of the method are known from the prior art, for example, WO 2019 / 174 996 A1, to which reference is hereby made.

[0054] Further advantages and details of the invention will become apparent from the description of exemplary embodiments based on the figures. They show: Fig. 1 schematically shows the components and the beam path in a projection exposure system, Fig. 2 schematically shows an arrangement of an optical component close to a separation plane between the illumination optics and the projection optics, Fig. 3 schematically shows an exemplary representation of a support structure for a lighting optic, Fig. 4 schematically shows a view of the supporting structure according to Fig. 3 from the top, Fig. 5 schematic representation of a support structure of a lighting optics with a highlighted frame and Fig. 6 schematically shows a view of the frame according to Fig. 5 to clarify further details.

[0055] A projection exposure system 1 for microlithography is used to produce a micro- or nanostructured electronic semiconductor component. A light or radiation source 2 emits EUV radiation 3 in the wavelength range, for example, between 0.2 nm and 30 nm, in particular between 0.1 nm and 15 nm.

[0056] Fig. 1 shows highly schematic main components of one of the projection exposure systems 1.

[0057] The radiation source 2 is part of a radiation source module. From the radiation source module, the illumination and imaging light 3 passes through an intermediate focus 4 and is guided from there by means of an illumination optics 15 to an object field 11 of the projection exposure system 1, in which a lithography mask 12 in the form of a reticle is arranged as the object to be projected.

[0058] The illumination optics 15 includes a field facet mirror 16 and a second facet mirror, which is referred to below as pupil facet mirror 17, even if it does not need to be arranged in a pupil plane, whose function corresponds to that which is known from the prior art and which is therefore in the Fig. 1 are shown only very schematically and without the corresponding EUV beam path.

[0059] After reflection by the field facet mirror 16, the EUV beam bundle impinges on the pupil facet mirror 17. The assignment of the individually actuatable sub-elements of the first optical element to those of the second optical element is determined depending on the desired illumination by the projection exposure system 1. To specify individual illumination angles, the illumination light 3 is thus guided sequentially along the illumination channel via pairs of one or more individual sub-elements of the first and second optical elements. These sub-elements are each individually tilted for control.

[0060] Via the pupil facet mirror 17 and possibly via a subsequent transmission optics (not shown), the individual light components are transferred into the illumination or object field 11 in a reticle or object plane 18 of a Fig. 1 also schematically shown projection optics 19 of the projection exposure system 1.

[0061] In a further embodiment of the illumination optics 15, in particular with a suitable position of an entrance pupil of the projection optics 19, the mirrors of the transmission optics in front of the object field 11 can also be omitted, which leads to a corresponding increase in the transmission of the projection exposure system 1 for the useful radiation beam.

[0062] The reticle 12, which reflects the useful radiation beam, is arranged in the object plane 18 in the area of ​​the object field 11. The reticle 12 is supported by a reticle holder 20, which can be displaced by a reticle displacement drive 21.

[0063] The projection optics 19 images the object field 11 into an image field 22 in an image plane 23. During projection exposure, a wafer 24 is arranged in this image plane 23. The wafer carries a light-sensitive layer that is exposed during projection exposure with the projection exposure system 1. The wafer 24 is supported by a wafer holder 25, which in turn can be displaced in a controlled manner via a wafer displacement drive 26.

[0064] During projection exposure, both the reticle 12 and the wafer are scanned synchronously in the scan direction by appropriately controlling the reticle displacement drive 21 and the wafer displacement drive 26. The wafer can be scanned in the x-direction during projection exposure at a scanning speed of typically 600 mm / s.

[0065] In the Fig. 2 schematically and exemplarily shows the installation space conditions between the last optical element 31 in the beam path of the illumination optics 15 and the reticle 12.

[0066] The illumination radiation 3 has a main beam direction 32. The main beam direction can be characterized by the main beam angle 33. The beam angle 33 is also referred to as the central angle of incidence on the reticle 12.

[0067] Schematically shown in the Fig. 2 a separation plane 34 between the illumination optics 15 and the projection optics 19. The separation plane 34 can in particular be oriented perpendicular to the object plane 18.

[0068] The separation plane 34 defines the virtual separation between the half-space in which the illumination optics 15 are arranged and the half-space in which the projection optics 19 are arranged.

[0069] With a small beam angle 33, the distance A between the last optical element 31 of the illumination optics 15 and the separation plane 34 is very small. In addition to the main beam angle 33, the distance A also depends on the size, in particular the extension of the last optical element 31 in the direction perpendicular to the separation plane 34.

[0070] The distance A is required for optical manufacturing processes and / or a module mechanism (not shown) enclosing the optical element 31.

[0071] For illustrative purposes only, the Fig. 2 also a beam 35 incident on the last optical element 31. In particular, if the beam path in the illumination optics 15 is tightly folded, the associated reduced installation space results in difficult requirements for a day structure 36 with which the optical components of the illumination optics are carried, ie positioned.

[0072] Such a support structure 36 is exemplary in the Fig. 3 and Fig. 4 shown.

[0073] The support structure 36 is open on one side. It has, in particular, an opening 38 extending in a longitudinal direction 37.

[0074] The longitudinal direction 37 can coincide with a normal object plane 18 or be parallel to such a normal direction.

[0075] The support structure 36 has a first receptacle 39 for receiving a first optical element. The first receptacle is Fig. 3 around the upper receptacle. This is not intended to be limiting. The support structure 36 can also be arranged differently oriented in the projection exposure system 1.

[0076] The first optical element, which can be arranged in the first receptacle 39, can be, in particular, a first facet mirror, in particular the field facet mirror 16. The first optical element is connected to the support structure 36 in the first receptacle 39, in particular fixedly or via a compensating element. The compensating element can serve, for example, to compensate for thermal expansion or for dynamic decoupling or adjustment of the optical elements. The optical element or the compensating element can, in particular, be screwed, clamped, or welded to the support structure 36.

[0077] At the opposite end in the longitudinal direction 37, the support structure has a second receptacle. The second receptacle 40 serves to accommodate a second optical element. The second optical element can be a second mirror, in particular a second facet mirror, in particular the pupil facet mirror 17.

[0078] In the Fig. 4, an open area 41 is visible. The illumination radiation 3 passes through the open area 41 from the last optical element 31 of the illumination optics 15 to the object field 11.

[0079] A plurality of transverse stiffeners 42 are arranged in the support structure 36. In particular, stiffening plates can serve as transverse stiffeners 42. The stiffening plates can each have recesses 45 that allow the obstructed passage of illumination radiation 3.

[0080] The recesses 45 can each be elliptical, in particular circular.

[0081] A longitudinal stiffener 43 is arranged in the support structure 36. A stiffening plate serves as the longitudinal stiffener 43. The longitudinal stiffener can be provided with a recess for the passage of EUV radiation 3. As shown in the Fig. 3 is shown by way of example and schematically, the recess 44 in the longitudinal stiffener 43 can be parabolic.

[0082] The support structure 36 encloses the beam path of the illumination optics 15 essentially in the shape of the letter C. The support structure 36 thus represents a structure that is open on one side.

[0083] Towards the open side, the support structure 36 has a flat boundary wall 49. The free surface of the boundary wall 49 can coincide with the parting plane 34. It is generally preferably oriented parallel to the parting plane 34.

[0084] By means of lateral projections 50, the support structure 36 can be arranged, in particular fastened, to supports in the projection exposure system 1.

[0085] To increase the rigidity, in particular the torsional rigidity of the support structure 36, the latter may have a frame 46. The frame 46 is shown by way of example in the Fig. 5. It is highlighted in the Fig. 5 and Fig. 6 shown purely schematically.

[0086] The frame 46 can be further stiffened using the frames 48. The frames 48 can form shaping ribs of the frame 46. An outer skin, particularly in the form of the stiffening plates 47, can then be applied to the frames.

[0087] The frame 40 with ribs 48 and / or stiffening plates 47 allows, particularly due to its regular structure, the production of small sections that can be combined to form the complete supporting structure 36. This allows for reduced costs and the required manufacturing accuracy.

[0088] Due to the triangular and / or trapezoidal cross-section, especially in combination with the frame construction, it is possible to save mass and volume and thus reduce the degree of machining compared to supporting structures with rectangular cross-sections.

[0089] The support structure 36 can be designed as a welded assembly. This offers greater design freedom due to advantageous segmentation.

[0090] Smaller raw material sections are also easier to obtain and are easier to produce and control in terms of their material quality and homogeneity. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2019 / 174 996 A1

[0053]

Claims

[1] Support structure (36) for an illumination optics (15) of a projection exposure system (1) for microlithography, comprising 1.

1. a frame (46) extending in a longitudinal direction (37), 1.1.

1. which only partially surrounds a radiation cross-sectional area in a plane perpendicular to the longitudinal direction (37) on the circumference, and 1.

2. one or more means for increasing the rigidity of the frame (46) selected from the following list: frames (48), struts, flat stiffening elements (47, 42, 43). [2] Support structure (36) according to claim 1, characterized by that the frame (46) is open over at least 50% of its extension in the longitudinal direction (37) to one side in the direction transverse to the longitudinal direction (37). [3] Support structure (36) according to claim 2, characterized by that it has an outwardly flat boundary wall (49) on the side towards which the frame (46) is open. [4] Support structure (36) according to one of the preceding claims, characterized by that the frame (46) has a triangular or trapezoidal or pentagonal cross-section at least in sections in the direction transverse to the longitudinal direction (37). [5] Support structure (36) according to one of the preceding claims, characterized by that the frame (46) is delimited in the longitudinal direction (37) by at least one triangular or trapezoidal stiffening plate (47). [6] Support structure (36) according to one of the preceding claims, characterized by that the frame (46) is delimited on the outside by three or four essentially triangular flat stiffening elements (47). [7] Support structure (36) according to one of the preceding claims, characterized by that the frame (46) has receptacles (39, 40) for receiving optical components at opposite ends in the longitudinal direction (37). [8] Support structure (36) according to one of the preceding claims, characterized by that one or more stiffening elements (42, 43) are arranged inside the frame (46). [9] Illumination optics (15) for a projection exposure system (1) for microlithography comprising 9.

1. a support structure (36) according to one of the preceding claims and 9.

2. at least one optical component which is carried by the support structure (36). [10] Illumination optics (15) according to claim 9, characterized by that the central angle of incidence (CRAO, chief ray angle at object) is at most 10°. [11] Illumination optics (15) according to one of claims 9 to 10, characterized by that a distance A of the last optical element (31) in the beam path in front of the reticle (12) to a plane (34) delimiting the support structure (36) towards the open side is at most 15 cm. [12] Illumination optics (15) according to one of claims 9 to 11, characterized by that the object-side numerical aperture (NAO) is at least 0.

3. [13] Illumination system for a projection exposure apparatus (1) for microlithography comprising 13.

1. an illumination optics (15) according to one of claims 9 to 12 and 13.

2. a radiation source (2) for generating illumination radiation (3). [14] Optical system for a projection exposure apparatus (1) for microlithography comprising 14.

1. an illumination optics (15) according to one of claims 9 to 12 and 14.

2. a projection optics (19) for transferring illumination radiation (3) from the object field (11) into an image field (22). [15] Projection exposure apparatus (1) for microlithography comprising 15.1 an illumination system according to claim 13 and 15.

2. a projection optics (19) for transferring illumination radiation (3) from the object field (11) into an image field (22). [16] Method for producing a micro- or nanostructured component comprising the following steps: 16.

1. Providing a projection exposure system (1) according to claim 15, 16.

2. Arranging a reticle (12) with structures to be imaged in the object field (11), 16.

3. Imaging the structures to be imaged onto a light-sensitive layer of a wafer (24) arranged in the image field (22). [17] Micro- or nanostructured component produced by a method according to claim 16.

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