TEMPERATURE MEDIUM LINE, OPTICAL SYSTEM AND PROJECTION ILLUMINATION SYSTEM

Abstract

A temperature control medium line (200A, 200B) for an optical system (100), comprising an outer hose (238), an inner hose (230A, 230B) arranged inside the outer hose (238) and made of a viscoelastic material, and a support element (212A, 212B) for radially supporting the inner hose (230A, 230B).

Description

[0001] The present invention relates to a temperature control medium line for an optical system, an optical system for a projection exposure system with such a temperature control medium line and a projection exposure system with such a temperature control medium line and / or such an optical system.

[0002] Microlithography is used to manufacture microstructured components, such as integrated circuits. The microlithography process is carried out using a lithography system, which includes an illumination system and a projection system. The image of a mask (reticule) illuminated by the illumination system is projected by the projection system onto a substrate, such as a silicon wafer, coated with a photosensitive layer (photoresist) and positioned in the image plane of the projection system. This transfers the mask structure onto the photosensitive coating of the substrate.

[0003] Driven by the pursuit of ever smaller structures in the fabrication of integrated circuits, EUV lithography systems are currently being developed that utilize light with wavelengths ranging from 0.1 nm to 30 nm, particularly 13.5 nm. Due to the high absorption of light of this wavelength by most materials, such EUV lithography systems require reflective optics, i.e., mirrors, instead of the previously used refracting optics, i.e., lenses.

[0004] In order to enable ever smaller feature sizes on the substrate, following Moore's Law, the demands placed on the EUV lithography systems used for production are constantly increasing. According to internal findings, current EUV lithography systems are equipped with cooling systems for the thermal stabilization of the mirrors and / or other structures.

[0005] Typically, the mirrors and / or structures to be cooled are connected by piping, which in turn is mounted on structures of the projection system itself. Due to its high heat capacity and availability, water is the preferred cooling medium. Especially in the development of water-cooled mirrors, their supporting structures, and infrastructure, pressure fluctuations and / or pulsations transported and transmitted via the cooling medium play a crucial role in the performance of the projection system and the image quality on the substrate. Pressure waves that propagate through the cooling medium at the speed of sound are subsequently referred to as Water Line Acoustics (WLA).

[0006] Sources or triggering mechanisms for thermal oscillations (WLA) are manifold. One example is flow-induced vibrations (FIV), which, depending on local geometric boundary conditions and the upstream and downstream flow conditions, cause persistent periodic and random fluctuations in the flow, particularly turbulence, of the cooling medium. These hydrodynamic fluctuations, namely turbulence, lead to the coupling of acoustic pressure waves, which propagate as WLA both downstream and upstream and, depending on the geometry of the piping, can result in standing waves.

[0007] Pressure and impulse fluctuations from the cooling medium lead to frequency-dependent dynamic excitation of the cooled components and the entire projection system. The sensitivity of the projection system components to incoming disturbances or vibrations also plays a role. Generally, pressure waves are reflected differently within the cooling unit depending on the geometric and acoustic boundary conditions as well as the materials used, resulting in frequency-dependent force amplitudes that act on the projection system. These disturbances negatively impact performance, for example, by affecting critical frequencies for mirror position control, causing mirror deformation due to pressure pulsations, or reducing the projection system's imaging accuracy.

[0008] To reduce the pressure fluctuations introduced into the cooling system to a specified level, design measures are required. These can be actively operated and / or controlled, or preferably, passive measures. Viscoelastic materials with gas inclusions represent one solution for reducing or suppressing pressure fluctuations in a cooling medium column. For example, the piping can have an inner tube made of a viscoelastic material that is in contact with the cooling medium. A gas-filled space can be provided between the inner tube and an outer tube of the piping.

[0009] Especially during the filling and emptying of the cooling system, operating conditions can arise in which the cooling system is subjected to a vacuum, for example, to ensure that all air is removed from the cooling system before filling with the cooling medium. If the viscoelastic inner tube were to completely collapse in such a scenario, all downstream components could no longer be properly emptied and dried. The same applies to other operating conditions or chosen piping designs where the pressure within the aforementioned gas space is greater than the pressure within the inner tube. This needs to be improved.

[0010] Against this background, one object of the present invention is to provide an improved temperature control medium line.

[0011] Accordingly, a temperature control fluid line for an optical system is proposed. The temperature control fluid line comprises an outer tube, an inner tube located inside the outer tube and made of a viscoelastic material, and a support element for radially supporting the inner tube.

[0012] The support element reliably prevents the inner tube from collapsing or bursting when a vacuum is applied to the temperature control fluid line. This allows downstream components of the optical system to be easily drained and dried. Furthermore, the support element also stabilizes the inner tube in the event of a design-related overpressure within a gas space between the outer and inner tubes. The support element thus also provides support when the pressure in the gas space exceeds the pressure inside the inner tube. This may be necessary, for example, due to specific operating conditions or special designs of the temperature control fluid line, such as an overpressure in the gas space.

[0013] Due to design considerations, it can be advantageous to adjust the pressure within the gas chamber to match the pressure of a temperature control medium flowing through the temperature control medium line. Consequently, the pressure within the gas chamber can be higher than atmospheric pressure, provided the pressure of the temperature control medium is also higher than atmospheric pressure. When the temperature control unit is inactive or the temperature control medium line is in transit, the pressure in the gas chamber is higher than the pressure within the inner tube. This can cause significant deformation of the elastic inner tube, potentially leading to collapse. The support element prevents collapse of the elastic inner tube in this scenario as well, reliably protecting it from substantial deformation and associated creep effects that could compromise its long-term functionality.

[0014] The optical system can be a projection optic of a projection exposure system or part of such a projection optic. Therefore, the optical system can also be referred to as a projection optic. However, the optical system can also be a lighting system of a projection exposure system or part of such a lighting system. The optical system preferably comprises at least one optical element. The optical element can be a mirror, in particular an EUV mirror. The optical system can comprise any number of optical elements.

[0015] The temperature control fluid line is preferably part of a temperature control unit for the optical system. The temperature control unit allows the optical element of the optical system to be cooled or heated. In this context, "temperature control" refers specifically to the process of adding or removing heat from the optical element using the temperature control unit. In particular, the temperature control unit allows the temperature of the optical element, especially an optically effective surface of the optical element, to be kept constant or within defined limits.

[0016] The outer hose is preferably a corrugated hose. However, the outer hose can also be a smooth hose. The fact that the inner hose is arranged "inside" the outer hose means, in particular, that the outer hose has an inner diameter that is larger than the outer diameter of the inner hose. The outer hose thus encloses or encapsulates the inner hose. A gas-filled space is preferably provided between the inner hose and the outer hose. The gas can be, for example, air or nitrogen.

[0017] In this context, a "viscoelastic" material is understood to be a material that exhibits partly elastic and partly viscous material behavior. Viscoelastic materials thus combine characteristics of both solids and liquids. The viscoelastic material can be a plastic material. In particular, fluororubber (FKM) is a viscoelastic material. Gas bubbles, especially air bubbles, can be trapped within the viscoelastic material. This means, in particular, that the viscoelastic material can contain gas inclusions. This increases the damping effect of the viscoelastic material for damping vibrations.

[0018] The support element can support the inner tube either by being located within the inner tube or by being integrated into the inner tube. "Within" in this context means, in particular, that the support element has an outer diameter that is smaller than the inner diameter of the inner tube. "Integrated" in this context means that the support element is surrounded or enclosed by the viscoelastic material. "Vacuum" in this context refers in particular to a negative pressure relative to the ambient pressure of the temperature control medium line. Specifically, the support element prevents the inner tube from collapsing to such an extent that at least a cross-section of the inner tube sufficient to apply the vacuum to the temperature control medium line remains open at all times. "Radial" means along or against a radial direction of the temperature control medium line.The radial direction is oriented in particular perpendicular to a symmetry or central axis of the temperature control medium line.

[0019] According to one embodiment, the support element is arranged inside the inner tube.

[0020] In this case, the support element and the inner tube are preferably two separate components. As mentioned previously, this means, in particular, that the outer diameter of the support element is smaller than the inner diameter of the inner tube. The inner tube can either rest directly against the support element, or a gap can be provided between the support element and the inner tube.

[0021] According to another embodiment, a gap is arranged between the support element and the inner tube.

[0022] During operation of the temperature control line, this gap is filled with the aforementioned temperature control medium, which flows through the line. The temperature control medium is a liquid. It can be water, particularly demineralized water. However, other liquids can also be used. The temperature control medium can also be referred to as a cooling medium.

[0023] According to another embodiment, the support element is fluid-permeable.

[0024] In this context, "fluid-permeable" means, in particular, that the temperature control medium can pass through the support element in a radial direction along the temperature control medium line. The temperature control medium then enters the aforementioned gap, which is located between the support element and the inner tube.

[0025] According to another embodiment, the support element has openings that penetrate the support element in a radial direction of the temperature control medium line.

[0026] Any number of openings can be provided. The openings can be evenly distributed around the central axis of the temperature control medium line.

[0027] According to another embodiment, the openings are slot-shaped and extend along a central axis of the temperature control medium line.

[0028] Alternatively, the openings can also be circular, oval, rectangular, or similar. Basically, the openings can have any geometry.

[0029] According to another embodiment, the support element is tubular, wire-shaped, grid-shaped and / or fabric-shaped.

[0030] In particular, the support element is flexible, so that the temperature control fluid line is also flexible. The support element can, for example, have a spiral geometry.

[0031] According to another embodiment, the coolant line has flange sections between which the support element is arranged, the support element being connected to the flange sections.

[0032] In particular, a first flange section and a second flange section are provided. The support element is rigidly connected to the flange sections. Several temperature control fluid lines can be connected to each other using the flange sections. Furthermore, the flange sections allow the temperature control fluid line to be connected to a temperature control channel, especially a cooling channel, an optical element as mentioned previously, or the like. Instead of a connection using the flange sections, material-bonded connections, especially welding, can also be used. A welded, screwed, clamped, and / or adhesive connection can also be provided.

[0033] According to another embodiment, the support element is connected to the flange sections in a multi-piece, single-piece, in particular single-piece material, force-fit, material-fit and / or form-fit manner.

[0034] A force-fit connection through forming and / or pressing is possible. "Multi-piece" can mean that the support element, for example, has two overlapping half-shells that are connected to the flange sections. "One-piece" or "single-part" in this context means, in particular, that the support element and the flange sections form a single component and are not composed of different sub-components. "One-piece material" in this context means that the support element and the flange sections are made entirely of the same material. For example, stainless steel can be used. In material-bonded connections, the joining partners are held together by atomic or molecular forces. Material-bonded connections are permanent connections that can only be separated by destroying the fasteners and / or the joining partners.Material-bonded connections can be made, for example, by gluing, soldering, welding, or vulcanizing. The support element and the flange sections can, for instance, be welded together. A form-fit connection is created by the interlocking or overlapping of at least two connecting partners. The support element and the flange sections can, for example, be clamped and / or bolted together.

[0035] According to another embodiment, the inner hose is connected to the flange sections by material bonding, force bonding and / or form bonding.

[0036] For example, the inner hose can be bonded to the flange sections. The inner hose can also be vulcanized to the flange sections. The outer hose is preferably also bonded to the flange sections. If the outer hose is made of metal, it can be welded to the flange sections.

[0037] According to another embodiment, the support element is integrated into the inner tube.

[0038] The fact that the support element is "integrated" into the inner tube means, in particular, that the support element and the inner tube are not separate components, but rather form a single, unified component. Specifically, the support element is located within the viscoelastic material of the inner tube.

[0039] According to another embodiment, the support element is materially bonded to the inner tube.

[0040] For example, the inner tube can be vulcanized to the support element. The support element and the inner tube are, in particular, permanently bonded together.

[0041] Furthermore, an optical system for a projection exposure system is proposed. The optical system comprises an optical element and a temperature control device for supplying or removing heat to or from the optical element, wherein the temperature control device includes such a temperature control medium line.

[0042] The optical system can comprise any number of optical elements. The optical elements are preferably mirrors, in particular EUV mirrors. The optical system can comprise any number of temperature control medium lines. The optical system is preferably a projection optic of the projection exposure system. However, the optical system can also be an illumination system.

[0043] According to one embodiment, the temperature control medium line fluidically connects a pump of the temperature control device to a temperature control channel of the optical element.

[0044] The temperature control channel can be a cooling channel and therefore also referred to as such. The optical element can have any number of temperature control channels. The temperature control medium line is, in particular, part of the piping system of the temperature control unit. The temperature control unit uses a pump to circulate the temperature control medium through the temperature control medium line in order to remove heat from the optical element or to supply heat to the optical element.

[0045] Furthermore, a projection exposure system is proposed. The projection exposure system includes such a temperature control medium line and / or such an optical system.

[0046] The projection exposure system can include any number of temperature control fluid lines. The projection exposure system can be an EUV lithography system. EUV stands for "Extreme Ultraviolet" and refers to a wavelength of the working light between 0.1 nm and 30 nm. The projection exposure system can also be a DUV lithography system. DUV stands for "Deep Ultraviolet" and refers to a wavelength of the working light between 30 nm and 250 nm.

[0047] The term "one" here is not necessarily to be understood as restricting the number to exactly one element. Rather, it can also refer to multiple elements, such as two, three, or more. Similarly, every other counter used here should not be interpreted as restricting the number to the exact number stated. Instead, numerical deviations, both higher and lower, are possible unless otherwise specified.

[0048] The embodiments and features described for the temperature control medium line apply accordingly to the proposed optical system and the proposed projection exposure system, and vice versa.

[0049] Other possible implementations of the invention also include combinations of features or embodiments described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In such cases, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0050] Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the exemplary embodiments of the invention described below. The invention will be explained in more detail below with reference to preferred embodiments and the accompanying figures. Fig. Figure 1 shows a schematic meridional section of a projection exposure system for EUV projection lithography; Fig. Figure 2 shows a schematic view of an embodiment of an optical system for the projection exposure system according to Fig. 1; Fig. Figure 3 shows a schematic sectional view of an embodiment of a temperature control medium line for the optical system according to Fig. 2; and Fig. Figure 4 shows a schematic sectional view of another embodiment of a temperature control medium line for the optical system according to Fig. 2.

[0051] In the figures, identical or functionally equivalent elements have been labelled with the same reference symbols, unless otherwise indicated. Furthermore, it should be noted that the representations in the figures are not necessarily to scale.

[0052] Fig. Figure 1 shows an embodiment of a projection exposure system 1 (lithography system), in particular an EUV lithography system. One embodiment of the illumination system 2 of the projection exposure system 1 has, in addition to a light or radiation source 3, an illumination optic 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a separate module from the rest of the illumination system 2. In this case, the illumination system 2 does not include the light source 3.

[0053] A reticule 7 arranged in the object field 5 is exposed. The reticule 7 is held by a reticule holder 8. The reticule holder 8 can be moved, particularly in a scanning direction, via a reticule displacement drive 9.

[0054] In the Fig. Figure 1 shows a Cartesian coordinate system with an x-direction x, a y-direction y, and a z-direction z. The x-direction x runs perpendicular to the plane of the drawing. The y-direction y runs horizontally, and the z-direction z runs vertically. The scan direction runs in the Fig. 1 along the y-direction y. The z-direction z runs perpendicular to the object plane 6.

[0055] The projection exposure system 1 comprises a projection optic 10. The projection optic 10 serves to image the object field 5 onto an image field 11 in an image plane 12. The image plane 12 is parallel to the object plane 6. Alternatively, an angle other than 0° between the object plane 6 and the image plane 12 is also possible.

[0056] A structure on the reticulum 7 is imaged onto a photosensitive layer of a wafer 13 located in the image plane 12 within the image field 11. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be moved, particularly along the y-direction y, via a wafer transfer drive 15. The movement of the reticulum 7 via the reticulum transfer drive 9 and of the wafer 13 via the wafer transfer drive 15 can be synchronized.

[0057] Light source 3 is an EUV radiation source. Light source 3 emits, in particular, EUV radiation 16, which is also referred to below as useful radiation, illumination radiation, or illumination light. The useful radiation 16 has a wavelength in the range between 5 nm and 30 nm. Light source 3 can be a plasma source, for example, an LPP source (Laser Produced Plasma) or a DPP source (Gas Discharged Produced Plasma). It can also be a synchrotron-based radiation source. Light source 3 can be a free-electron laser (FEL).

[0058] The illumination radiation 16 emanating from the light source 3 is focused by a collector 17. The collector 17 can be a collector with one or more ellipsoidal and / or hyperboloid reflective surfaces. The at least one reflective surface of the collector 17 can be illuminated by the illumination radiation 16 at grazing incidence (GI), i.e., with angles of incidence greater than 45°, or at normal incidence (NI), i.e., with angles of incidence less than 45°. The collector 17 can be structured and / or coated to optimize its reflectivity for the useful radiation and to suppress stray light.

[0059] After the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 can represent a separation between a radiation source module, comprising the light source 3 and the collector 17, and the illumination optics 4.

[0060] The illumination optics 4 comprise a deflecting mirror 19 and, downstream in the beam path, a first faceted mirror 20. The deflecting mirror 19 can be a planar deflecting mirror or, alternatively, a mirror with an effect that influences the beam shape beyond the mere deflection effect. Alternatively or additionally, the deflecting mirror 19 can be designed as a spectral filter that separates a useful wavelength of the illumination radiation 16 from stray light of a different wavelength. If the first faceted mirror 20 is arranged in a plane of the illumination optics 4 that is optically conjugate to the object plane 6 as the field plane, it is also referred to as a field faceted mirror. The first faceted mirror 20 comprises a plurality of individual first facets 21, which can also be referred to as field facets. Of these first facets 21, the following are in the Fig. 1 only some examples are shown.

[0061] The first facets 21 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or semicircular border contour. The first facets 21 can be designed as planar facets or alternatively as convexly or concavely curved facets.

[0062] As is known, for example, from DE 10 2008 009 600 A1, the first facets 21 can themselves each be composed of a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirror 20 can in particular be designed as a microelectromechanical system (MEMS system). For details, reference is made to DE 10 2008 009 600 A1.

[0063] Between the collector 17 and the deflecting mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction y.

[0064] In the beam path of the illumination optics 4, a second faceted mirror 22 is arranged downstream of the first faceted mirror 20. If the second faceted mirror 22 is arranged in a pupil plane of the illumination optics 4, it is also referred to as a pupil faceted mirror. The second faceted mirror 22 can also be arranged at a distance from a pupil plane of the illumination optics 4. In this case, the combination of the first faceted mirror 20 and the second faceted mirror 22 is also referred to as a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1, EP 1 614 008 B1, and US 6,573,978.

[0065] The second facet mirror 22 comprises a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

[0066] The second facets 23 can also be macroscopic facets, which may, for example, have round, rectangular, or hexagonal edges, or alternatively, facets composed of micromirrors. Reference is also made to DE 10 2008 009 600 A1 in this regard.

[0067] The second facets 23 can have planar or alternatively convex or concave curved reflective surfaces.

[0068] The illumination optics 4 thus form a double-faceted system. This basic principle is also known as a honeycomb condenser (English: Fly's Eye Integrator).

[0069] It can be advantageous not to arrange the second faceted mirror 22 exactly in a plane that is optically conjugate to a pupil plane of the projection optics 10. In particular, the second faceted mirror 22 can be arranged tilted relative to a pupil plane of the projection optics 10, as described, for example, in DE 10 2017 220 586 A1.

[0070] With the aid of the second faceted mirror 22, the individual first facets 21 are imaged into the object field 5. The second faceted mirror 22 is the last beam-shaping, or indeed the last, mirror for the illumination radiation 16 in the beam path before the object field 5.

[0071] In another embodiment of the illumination optics 4, not shown, a transmission optic can be arranged in the beam path between the second facet mirror 22 and the object field 5, which contributes in particular to imaging the first facets 21 into the object field 5. The transmission optic can have exactly one mirror, or alternatively two or more mirrors, arranged one behind the other in the beam path of the illumination optics 4. The transmission optic can, in particular, comprise one or two mirrors for normal incidence (NI mirrors) and / or one or two mirrors for grazing incidence (GI mirrors).

[0072] The lighting optics 4, in the version shown in the Fig. Figure 1 shows exactly three mirrors after the collector 17, namely the deflecting mirror 19, the first faceted mirror 20 and the second faceted mirror 22.

[0073] In a further embodiment of the lighting optics 4, the deflecting mirror 19 can also be omitted, so that the lighting optics 4 after the collector 17 can then have exactly two mirrors, namely the first faceted mirror 20 and the second faceted mirror 22.

[0074] The mapping of the first facets 21 by means of the second facets 23 or with the second facets 23 and a transmission optic into the object plane 6 is regularly only an approximate mapping.

[0075] The projection optics 10 comprise a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

[0076] In the Fig. In the example shown, the projection optics 10 comprise six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or any other number of mirrors Mi are also possible. The projection optics 10 is a doubly obscured optic. The penultimate mirror M5 and the last mirror M6 each have an aperture for the illumination radiation 16. The projection optics 10 has an image-side numerical aperture that is greater than 0.33 and can also be greater than 0.6, for example, 0.7 or 0.75.

[0077] The reflective surfaces of the mirrors Mi can be designed as freeform surfaces without an axis of rotational symmetry. Alternatively, the reflective surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflective surface shape. The mirrors Mi, like the mirrors of the illumination optics 4, can have highly reflective coatings for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

[0078] The projection optics 10 has a large object-image offset in the y-direction y between a y-coordinate of a center of the object field 5 and a y-coordinate of the center of the image field 11. This object-image offset in the y-direction y can be approximately as large as a z-distance between the object plane 6 and the image plane 12.

[0079] The projection optics 10 can be anamorphic. In particular, they have different image scales βx, βy in the x and y directions. The two image scales βx, βy of the projection optics 10 are preferably (βx, βy) = (+ / - 0.25, + / - 0.125). A positive image scale β indicates a projection without image inversion. A negative value for the image scale β indicates a projection with image inversion.

[0080] The projection optics 10 thus lead to a reduction in the x-direction x, that is, in the direction perpendicular to the scan direction, in a ratio of 4:1.

[0081] The projection optics 10 lead to a reduction of 8:1 in the y-direction y, that is, in the scan direction.

[0082] Other magnification ratios are also possible. Magnification ratios with the same sign and absolute value in the x and y directions (x, y), for example with absolute values ​​of 0.125 or 0.25, are also possible.

[0083] The number of intermediate image planes in the x and y directions x, y in the beam path between the object field 5 and the image field 11 can be the same or, depending on the design of the projection optics 10, different. Examples of projection optics with different numbers of such intermediate images in the x and y directions x, y are known from US 2018 / 0074303 A1.

[0084] Each 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 result, in particular, in illumination according to Köhler's principle. The far field is divided into a multitude of object fields 5 with the help of the first facets 21. The first facets 21 generate a plurality of images of the intermediate focus on the second facets 23 assigned to each of them.

[0085] The first facets 21 are each superimposed on a corresponding second facet 23 to illuminate the object field 5 on the reticle 7. The illumination of the object field 5 is particularly homogeneous. It preferably exhibits a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

[0086] The illumination of the entrance pupil of the projection optics 10 can be geometrically defined by arranging the second facets 23. By selecting the illumination channels, in particular the subset of the second facets 23 that carry light, the intensity distribution in the entrance pupil of the projection optics 10 can be adjusted. This intensity distribution is also referred to as the illumination setting or illumination pupil filling.

[0087] Another preferred pupil uniformity in the area of ​​defined illuminated sections of an illumination pupil of the illumination optics 4 can be achieved by a redistribution of the illumination channels.

[0088] Further aspects and details of the illumination of the object field 5 and, in particular, the entrance pupil of the projection optics 10 are described below.

[0089] The projection optics 10 can, in particular, have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

[0090] The entrance pupil of the projection optics 10 cannot always be illuminated exactly by the second faceted mirror 22. When the projection optics 10 image the center of the second faceted mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, a surface can be found where the pairwise determined separation of the aperture rays is minimized. This surface represents the entrance pupil or a surface conjugate to it in real space. In particular, this surface exhibits a finite curvature.

[0091] The projection optics 10 may have different entrance pupil positions for the tangential and sagittal beam paths. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second faceted mirror 22 and the reticle 7. This optical element can accommodate the different positions of the tangential and sagittal entrance pupils.

[0092] During the Fig. In the arrangement of the components of the illumination optics 4 shown in Figure 1, the second faceted mirror 22 is arranged in a plane conjugate to the entrance pupil of the projection optics 10. The first faceted mirror 20 is arranged tilted relative to the object plane 6. The first faceted mirror 20 is arranged tilted relative to an arrangement plane defined by the deflecting mirror 19. The first faceted mirror 20 is arranged tilted relative to an arrangement plane defined by the second faceted mirror 22.

[0093] Fig. Figure 2 shows a schematic view of an embodiment of an optical system 100 for the projection exposure system 1.

[0094] The optical system 100 can be a projection optic 10 as previously described, or part of such a projection optic 10. Therefore, the optical system 100 can also be referred to as a projection optic. However, the optical system 100 can also be an illumination system 2 as previously described, or part of such an illumination system 2. Therefore, the optical system 100 can alternatively be referred to as an illumination system. In the following, however, it will be assumed that the optical system 100 is a projection optic 10, or part of such a projection optic 10. The optical system 100 is suitable for EUV lithography. However, the optical system 100 can also be suitable for DUV lithography.

[0095] The optical system 100 can comprise several optical elements 102, of which in the Fig. However, only one is shown in Figure 2. Therefore, only one optical element 102 will be discussed below. The optical element 102 can be one of the mirrors M1 to M6. The optical element 102 comprises a substrate 104 and an optically effective surface 106, for example, a mirror surface. The substrate 104 can also be referred to as the mirror substrate. The substrate 104 can comprise glass, ceramic, glass-ceramic, or other suitable materials. The optically effective surface 106 is suitable for reflecting illuminating radiation 16, in particular EUV radiation. The optical element 102 can have any geometry. Fig. Figure 2 shows the optical element 102 and the optically effective surface 106 in a very simplified manner.

[0096] A large number of temperature control channels 108 run through the substrate 104, of which in the Fig. However, only one is shown in Figure 2. Therefore, only one temperature control channel 108 is referred to in the following. The temperature control channel 108 can also be called a cooling channel. The temperature control channel 108 can be introduced into the substrate 104 using a subtractive manufacturing process, for example, by deep-hole drilling. In the simplest case, the temperature control channel 108 can be – as shown in the Fig. Figure 2 shows the cooling channel running straight through the substrate 104. However, the cooling channel 108 can also be curved, for example, in a meandering shape. Not only can the optical element 102 have such a cooling channel 108, but any other components of the optical system 100, such as support structures of the optical element 102, can also have such a cooling channel 108.

[0097] The optical element 102 is associated with a temperature control device 110, which is part of the optical system 100. The temperature control device 110 can also be referred to as a cooling device. The temperature control channel 108 can be part of the temperature control device 110. With the aid of the temperature control device 110, the temperature control channel 108 can be flushed with a temperature control medium K, for example, in the form of demineralized water, in order to dissipate heat Q, which is introduced into the optical element 102, for example, by means of the illumination radiation 16, from the optical element 102. Conversely, heat Q can also be supplied to the optical element 102 with the temperature control medium K. However, it is assumed below that heat Q is dissipated with the aid of the temperature control medium K. Therefore, the temperature control medium K can also be referred to as a cooling medium. The temperature control medium K is a liquid.

[0098] The temperature control device 110 comprises, in addition to the temperature control channel 108, a pump 112, in particular a water pump, and a piping system 114 that fluidically connects an inlet and an outlet of the pump 112 to the temperature control channel 108. Preferably, the piping system 114 is – unlike in the Fig. Figure 2 shows the optical element 102 not being brought to the side, but rather to the rear. Suitable connection pieces can be provided on the optical element 102 for this purpose, to which the piping 114 can be flanged. The piping 114 can be flexibly deformable, at least in sections.

[0099] In order to enable ever smaller feature sizes on the wafer 13, in accordance with Moore's Law, the requirements for the projection exposure systems 1 used for production are also constantly increasing. According to internal findings, current projection exposure systems 1 have, as previously mentioned, temperature control units 110 for the thermal stabilization of the optical elements 102 and / or other structures. Temperature control channels 108 can be routed through both the optical elements 102 and the structures.

[0100] The optical elements 102 and / or structures to be cooled are typically connected to each other by a piping system 114, as previously mentioned, which in turn is attached to structures of the optical system 100 itself. Active cooling ensures both maximum heat dissipation and good controllability of the optical system 100. Due to its high heat capacity and availability, water is preferably used as the cooling medium K. The flowing cooling medium K also ensures improved heat transfer at the surfaces through which it flows, due to forced convection.

[0101] Specifically, in the development of water-cooled optical elements 102, their supporting structures and infrastructure, pressure fluctuations and / or pressure pulsations transported and transmitted via the temperature control medium K play a crucial role with regard to the performance of the optical system 100 and the image quality on the wafer 13. Pressure waves that propagate at the speed of sound in the temperature control medium K, such as approximately 1,500 m / s in an acoustically hard environment, are subsequently referred to as Water Line Acoustics (WLA).

[0102] Sources or triggering mechanisms for thermal oscillations (WLA) are manifold. One example is flow-induced vibrations (FIV), which, depending on local geometric boundary conditions and the upstream and downstream flow conditions, cause persistent periodic and random fluctuations in the flow, particularly turbulence, of the temperature control medium K. These hydrodynamic fluctuations, namely turbulence, lead to the coupling of acoustic pressure waves, which propagate as WLA both downstream and upstream and, depending on the geometry of the piping 114, can lead to standing waves.

[0103] Another triggering mechanism involves transmitted structural vibrations and the interaction between structural components and the temperature control medium K. Both the structural vibrations themselves and the interaction exhibit frequency-dependent amplitudes. For example, structural vibrations can be transmitted via the supports of the piping 114 to the pipe walls of the piping 114 and thus directly into a liquid column of the temperature control medium K. Temperature control channels 108 integrated directly into structural components can also absorb the structural vibration directly via the temperature control medium K itself. Additionally, acoustic disturbances from the surrounding environment can also affect the liquid column of the temperature control medium K.

[0104] WLA is caused by FIV only in an actively flowed temperature control unit 110 as previously described. The other mechanisms mentioned above can also occur in a system filled only with the temperature control medium K, without active flow. This means that a countermeasure, such as switching off pump 112, does not provide a general remedy, but only addresses FIV as the source.

[0105] The pressure and impulse fluctuations from the temperature control medium K and the resulting forces on the walls of the temperature control channels 108 lead to a frequency-dependent dynamic excitation of the cooled components and the entire optical system 100. The sensitivities of the components of the optical system 100 to incoming disturbances or vibrations also play a role. Generally, pressure waves are reflected differently in the temperature control unit 110 depending on the geometric and acoustic boundary conditions as well as the materials used, resulting in frequency-dependent force amplitudes that act on the optical system 100. These disturbances negatively affect performance, for example, critical frequencies for position control of the optical elements 102, deformation of the optical elements 102 due to pressure pulsations, or the imaging accuracy of the optical system 100.

[0106] To reduce the pressure fluctuations introduced into the temperature control unit 110 to a specified level, design measures are therefore required. These can be actively operated and / or controlled, or preferably passive. Viscoelastic materials with gas inclusions represent one solution for reducing or suppressing pressure fluctuations in the liquid column of the temperature control medium K. For example, the piping 114 can have an internal inner tube made of a viscoelastic material that is in contact with the temperature control medium K.

[0107] Especially during the filling and emptying of the temperature control unit 110, operating conditions can occur in which the unit is subjected to a vacuum, for example, to ensure that all air is removed from the unit before filling with the temperature control medium K. If the viscoelastic inner tube were to completely collapse in such a scenario, all downstream components could no longer be properly emptied and / or dried. This needs to be improved.

[0108] Due to design considerations, it may be advantageous to adjust the pressure within a gas-filled space between the inner tube and an outer tube of the piping 114 to the pressure of the temperature control medium K flowing through the piping 114. This means that the pressure within the gas space can be higher than atmospheric pressure, provided the pressure of the temperature control medium K is also higher than atmospheric pressure. When the temperature control unit 110 is inactive or when the piping 114 is being transported, the pressure in the gas space is higher than the pressure inside the inner tube. This can cause the elastic inner tube to deform significantly and potentially collapse. Deformations resulting from this collapse and the associated creep effects could compromise the long-term function of the elastic inner tube.

[0109] Fig. Figure 3 shows a schematic sectional view of an embodiment of a temperature control medium line 200A for the optical system 100.

[0110] The temperature control medium line 200A is part of the piping 114 of the temperature control unit 110. The piping 114 can have several such temperature control medium lines 200A. During operation of the temperature control unit 110, the temperature control medium K is pumped through the temperature control medium line 200A by means of the pump 112. The temperature control medium line 200A can be flexibly deformable.

[0111] The temperature control medium line 200A is assigned a symmetry or central axis 202, with respect to which the temperature control medium line 200A is rotationally symmetrical. The temperature control medium line 200A is also assigned a radial direction R, which is arranged perpendicular to the central axis 202 and oriented away from it.

[0112] The temperature control medium line 200A has a first flange section 204 and a second flange section 206. The flange sections 204 and 206 are each rotationally symmetrical about the central axis 202. Using the flange sections 204 and 206, several temperature control medium lines 200A can be connected to each other, or the temperature control medium line 200A can be connected to the temperature control channel 108. The first flange section 204 has an inlet or outlet opening 208 through which the temperature control medium K can enter or exit the temperature control medium line 200A. The second flange section 206 has an inlet or outlet opening 210 through which the temperature control medium K can enter or exit the temperature control medium line 200A.

[0113] A fluid-permeable support element 212A is arranged between the two flange sections 204 and 206. "Fluid-permeable" in this context means that the temperature control medium K can pass through the support element 212A along the radial direction R. The support element 212A is connected to the flange sections 204 and 206. The support element 212A can be integrally connected to the flange sections 204 and 206, particularly as a single piece of material. "Integrated" or "one-piece" in this context means that the support element 212A and the flange sections 204 and 206 form a single component and are not composed of different sub-components. "Made of material" in this context means that the support element 212A and the flange sections 204 and 206 are made entirely of the same material, such as stainless steel. The support element 212A can also consist of multiple parts. For example, the support element 212A can have two overlapping half-shells.

[0114] The support element 212A and the flange sections 204, 206 can also be joined by material bonding and / or form-fitting. In material bonding, the joining partners are held together by atomic or molecular forces. Material bonding connections are permanent connections that can only be separated by destroying the bonding agent and / or the joining partners. Material bonding can be achieved, for example, by gluing, soldering, welding, or vulcanizing. The support element 212A and the flange sections 204, 206 can, for example, be welded together. A form-fitting connection is created by the interlocking or overlapping of at least two joining partners. The support element 212A and the flange sections 204, 206 can, for example, be clamped and / or bolted together.A crimp connection or, more generally, a force-fit connection between the support element 212A and the flange sections 204, 206 is also possible.

[0115] The support element 212A is tubular and can be rotationally symmetrical about the central axis 202. The support element 212A comprises an inner surface 214 and an outer surface 216 facing away from the inner surface 214. The inner surface 214 and the outer surface 216 can be cylindrical. The inner surface 214 encloses or delimits an interior space 218 of the temperature control medium line 200A, through which the temperature control medium K flows.

[0116] As mentioned previously, the support element 212A is fluid-permeable, allowing the temperature control medium K from the interior 218 to flow through the support element 212A in the radial direction R. The fluid permeability of the support element 212A is achieved by providing it with a plurality of openings 220, 222, 224, 226, 228. These openings can have any geometry. For example, they can be circular, oval, rectangular, or the like. In the present case, the openings 220, 222, 224, 226, 228 are slot-shaped and extend along the central axis 202. The openings 220, 222, 224, 226, 228 can be arranged evenly distributed around the central axis 202. The support element 212A can also be made of a spiral wire, a mesh, or a fabric.In this case, fluid permeability is also present.

[0117] The temperature control medium line 200A further comprises an inner tube 230A. The support element 212A is housed within the inner tube 230A. Accordingly, the inner tube 230A has an inner diameter that is larger than the outer diameter of the support element 212A. The inner tube 230A includes an inner surface 232 and an outer surface 234 facing away from the inner surface 232. The inner surface 232 and the outer surface 234 can be cylindrical. The inner surface 232 of the inner tube 230A faces the outer surface 216 of the support element 212A. The inner tube 230A can also be referred to as the inner liner.

[0118] The inner surface 232 of the inner hose 230A can be in contact with the outer surface 216 of the support element 212A. Alternatively, as in the Fig. Figure 3 shows that a gap 236 filled with the temperature control medium K is provided between the inner surface 232 of the inner tube 230A and the outer surface 216 of the support element 212A. The temperature control medium K can therefore flow from the interior 218 into the gap 236 through the openings 220, 222, 224, 226, 228.

[0119] The inner hose 230A is a smooth hose. The inner hose 230A can be extruded. However, the inner hose 230A can also be a molded part, for example, an injection-molded part. The inner hose 230A is made of a viscoelastic material. The inner hose 230A can be made of fluororubber (FKM). The inner hose 230A is gas-tightly connected to the flange sections 204 and 206. The inner hose 230A can be bonded to the flange sections 204 and 206. For example, the inner hose 230A is glued or vulcanized to the flange sections 204 and 206. However, the inner hose 230A can also be force-fitted and / or form-fitted to the flange sections 204 and 206.

[0120] The temperature control medium line 200A further comprises an outer hose 238. The outer hose 238 is a corrugated hose. However, the outer hose 238 can also be a smooth hose. The inner hose 230A is enclosed within the outer hose 238, with the support element 212A being enclosed within the inner hose 230A. Accordingly, the outer hose 238 has an inner diameter that is larger than the outer diameter of the inner hose 230A. The outer hose 238 can be made of a plastic material. The outer hose 238 can also be made of a metal. The outer hose 238 has an inner surface 240 facing the outer surface 234 of the inner hose 230A. Facing away from the inner surface 240, the outer hose 238 has an outer surface 242.

[0121] A gap-shaped gas space 244, filled with a gas such as air or nitrogen, is provided between the inner hose 230A and the outer hose 238. The outer hose 238 is gas-tightly connected to the flange sections 204 and 206. In particular, the outer hose 238 is bonded to the flange sections 204 and 206. The outer hose 238 can be bonded or vulcanized to the flange sections 204 and 206. This applies if the outer hose 238 is made of a plastic material. Preferably, however, the outer hose 238 is made of a metal. The outer hose 238 is bonded to the flange sections 204 and 206, in particular by welding. A 100% tightness must be ensured.

[0122] During operation of the temperature control medium line 200A, the temperature control medium K flows through it. Because the support element 212A is fluid-permeable, the temperature control medium K can come into contact with the inner tube 230A. The viscoelastic material of the inner tube 230A suppresses or reduces pressure fluctuations in the liquid column of the temperature control medium K. Pressure disturbances in the liquid column of the temperature control medium K can communicate with the viscoelastic inner tube 230A, thus ensuring that its damping function is not compromised.

[0123] If a vacuum is applied to the temperature control fluid line 200A, the inner tube 230A presses against the support element 212A on the outside, preventing it from collapsing. All components downstream of the temperature control fluid line 200A can then be easily drained and / or dried. The support element 212A thus helps prevent the inner tube 230A from collapsing completely when a vacuum is present within the temperature control fluid line 200A.

[0124] Due to design considerations, it may be advantageous to match the pressure within the gas chamber 244 to the pressure of the temperature control medium K flowing through the temperature control medium line 200A. Consequently, the pressure within the gas chamber 244 can be higher than atmospheric pressure, provided the pressure of the temperature control medium K is also higher than atmospheric pressure. When the temperature control unit 110 is inactive or when the temperature control medium line 200A is in transit, the pressure in the gas chamber 244 is higher than the pressure within the inner tube 230A. This can cause the elastic inner tube 230A to deform significantly and potentially collapse. The support element 212A prevents the elastic inner tube 230A from collapsing in this case as well, thus reliably protecting it from significant deformation and associated creep effects that could compromise the long-term function of the elastic inner tube 230A.

[0125] Preferably, the openings 220, 222, 224, 226, 228 are designed as slots parallel to the flow direction of the temperature control medium K through the temperature control medium line 200A in order to minimize vortex shedding and associated disturbances. However, in addition to this preferred variant, it is also possible to make the support element 212A, for example, from a wire, particularly as a spiral, or to manufacture it from a fabric and / or mesh in any form.

[0126] The cross-sectional geometry of the support element 212A is variable. A circular cylindrical shape is preferred. However, oval or polygonal, especially extruded, profiles are also possible. A wire or wires in various shapes can also be used as the support element 212A. For example, a spiral shape, a braid, or a grid is possible. Various materials can be used for the support element 212A. For example, plastics, fibers, metals, or the like can be used. However, it must be ensured that the support element 212A protects the inner tube 230A from collapse or damage. The support element 212A can also be transferred to other WLA measures or dampers in the temperature control unit 110.

[0127] The temperature control medium line 200A offers the following advantages. It ensures trouble-free filling and emptying of the entire temperature control unit 110. Overstressing due to under- or overpressure of the inner hose 230A is avoided. In particular, it prevents creep effects within the viscoelastic inner hose 230A that could impair its function. Alternatively, the inner hose 230A could collapse by significantly increasing its wall thickness. However, this would have negative parasitic effects on the installation space and the dynamic damping properties of the inner hose 230A. By using the support element 212A, these undesirable parasitic effects either do not occur at all or are at least significantly reduced.

[0128] Fig.Figure 4 shows a schematic sectional view of another embodiment of a temperature control medium line 200B for the optical system 100.

[0129] The temperature control medium line 200B is essentially identical in design and function to the temperature control medium line 200A. Therefore, only the differences between the two versions of the temperature control medium line 200A and 200B will be discussed below.

[0130] The temperature control medium line 200B differs from the temperature control medium line 200A only in that the support element 212A and the inner tube 230A are not two separate components, but rather an inner tube 230B is provided into which a support element 212B, for example in the form of a spiral, is integrated. For example, the support element 212B can be overmolded or overvulcanized with a viscoelastic material, in particular an FKM, to form the inner tube 230B with the integrated support element 212B.

[0131] The support element 212B is not necessarily spiral-shaped. For example, a wire, fabric, or mesh can be vulcanized directly into the inner tube 230B as the support element 212B. Various materials are suitable for this purpose. Due to potential contact with the temperature control medium K, stainless steel is preferred.

[0132] Although the present invention has been described using exemplary embodiments, it can be modified in many ways. REFERENCE MARK LIST 1 Projection exposure system 2 Lighting system 3 light source 4 Lighting optics 5 object field 6 Object level 7 reticles 8 label holders 9 Reticle displacement drive 10 Projection optics 11 Image field 12 Image plane 13 wafers 14 wafer holders 15 wafer transfer drive 16 Lighting radiation 17 Collector 18 Intermediate focus plane 19 deflecting mirrors 20 first faceted mirror 21 first facet 22 second faceted mirror 23 second facet 100 optical system 102 optical element 104 Substrat 106 optically effective areas 108 Temperature control channel 110 Temperature control unit 112 Pump 114 Piping 200A temperature control fluid line 200B Temperature control fluid line 202 Central axis 204 Flange section 206 Flange section 208 Entrance or exit opening 210 Entrance or exit opening 212A Support element 212B Support element 214 interior surface area 216 outdoor area 218 Interior 220 Opening 222 Opening 224 Opening 226 Opening 228 Opening 230A inner hose 230B inner tube 232 interior surface area 234 outdoor area 236 gap 238 Outer hose 240 interior surface area 242 outdoor area 244 Gas chamber K tempering medium M1 mirror M2 mirrors M3 mirror M4 mirrors M5 mirror M6 mirrors Q Heat R Radial direction x x-direction y y-direction z z-direction QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] DE 10 2008 009 600 A1 [0062, 0066] US 2006 / 0132747 A1

[0064] EP 1 614 008 B1

[0064] US 6,573,978

[0064] DE 10 2017 220 586 A1

[0069] US 2018 / 0074303 A1

[0083]

Claims

[1] Temperature control medium line (200A, 200B) for an optical system (100), comprising an outer hose (238), an inner tube (230A, 230B) disposed within the outer tube (238) and made of a viscoelastic material, and a support element (212A, 212B) for radially supporting the inner tube (230A, 230B). [2] Tempering medium line according to claim 1, wherein the support element (212A) is arranged within the inner tube (230A). [3] Temperature control medium line according to claim 1 or 2, wherein a gap (236) is arranged between the support element (212A) and the inner tube (230A). [4] Temperature control medium line according to one of claims 1-3, wherein the support element (212A) is fluid-permeable. [5] Temperature control medium line according to claim 4, wherein the support element (212A) has openings (220, 222, 224, 226, 228) breaking through the support element (212A) in a radial direction (R) of the temperature control medium line (200A). [6] Temperature control medium line according to claim 5, wherein the openings (220, 222, 224, 226, 228) are slot-shaped and extend along a central axis (202) of the temperature control medium line (200A). [7] Temperature control medium line according to one of claims 1-6, wherein the support element (212A) is tubular, wire-shaped, grid-shaped and / or fabric-shaped. [8] Temperature control medium line according to one of claims 1-7, wherein the coolant line (200A) has flange sections (204, 206) between which the support element (212A) is arranged, and wherein the support element (212A) is connected to the flange sections (204, 206). [9] Temperature control medium line according to claim 8, wherein the support element (212A) is connected to the flange sections (204, 206) in a multi-piece, single-piece, in particular in a single-piece, force-fitting, material-fitting and / or form-fitting manner. [10] Temperature control medium line according to claim 8 or 9, wherein the inner tube (230A) is connected to the flange sections (204, 206) in a materially bonded, force-locked and / or form-locked manner. [11] Temperature control medium line according to claim 1, wherein the support element (212B) is integrated into the inner tube (230B). [12] Temperature control medium line according to claim 11, wherein the support element (212B) is integrally connected to the inner tube (230B). [13] Optical system (100) for a projection exposure apparatus (1), comprising an optical element (102) and a temperature control device (110) for supplying or dissipating heat (Q) to or from the optical element (102), wherein the temperature control device (110) comprises a temperature control medium line (200A, 200B) according to one of claims 1-12. [14] Optical system according to claim 13, wherein the temperature control medium line (200A, 200B) fluidically connects a pump (112) of the temperature control device (110) to a temperature control channel (108) of the optical element (102). [15] Projection exposure system (1) with a temperature control medium line (200A, 200B) according to one of claims 1-12 and / or an optical system (100) according to claim 13 or 14.

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