Optical systems, especially lithography systems

Abstract

The present invention relates to an optical system, in particular to a lithography system, comprising a plate-shaped component (214), in particular a stop element, preferably a frame-shaped holder (216) for holding the component (214), and a plurality of webs (218a, b) for connecting the plate-shaped component (214) to the holder (216). The plate-shaped component (214) is preferably releasedly connected to the wire-shaped webs (218a, b), the plate-shaped component (214) is attached to a support structure, and the webs (218a, b) are releasedly connected to the support structure.

Description

Technology Field

[0001] Cross-reference regarding related applications

[0002] This application claims priority to German patent application No. 102020211663.6 filed on September 17, 2020, the entire disclosure of which is considered as part of the disclosure of this application and incorporated by reference. Background Technology

[0003] The present invention relates to an optical system, particularly a lithography system, comprising preferably a plate-shaped component, particularly a stationary element, preferably a frame-shaped holder, and a plurality of webs for connecting the component to the holder.

[0004] A lithography system may be a lithography device for exposing a wafer or other microlithography optical system, such as an inspection system, for example, a system for measuring or inspecting a mask, wafer, etc. used in lithography. The lithography system may be, in particular, an EUV lithography device or a DUV lithography device. EUV stands for "Extreme Ultraviolet" and indicates a wavelength of radiation used from 0.1 nm to 30 nm. DUV stands for "Deep Ultraviolet" and indicates a wavelength of radiation used from 30 nm to 250 nm.

[0005] The component held by the web or holder may be, for example, a manipulator element, particularly an actuator or a stop element. Stop elements are used for various purposes in optical systems, particularly in lithography systems, and are referred to, for example, as aperture stop, shield stop, field stop, stray light stop, external light stop, etc., depending on their function in the optical system.

[0006] The aperture stop serves to trim the work light radially relative to the beam path from the outside to the inside. The shield stop serves to cover the shield in the beam path. To this end, the shield stop cuts the inner portion of the work light—relative to the radial beam path. The outer light stop or stray light stop is often positioned in the intermediate image or intermediate image plane. The field stop is positioned in the field plane.

[0007] A shield stop is typically held in the beam path by a holder element, for example, a web, to connect the shield stop to a holder outside the beam path. Each of these holder elements blocks the beam path from a portion of the working light (used light) that contributes to imaging. Therefore, the holder elements are typically very thin and can be designed, for example, in the form of a thin wire, a thread, a spring, or a blade.

[0008] DE 10 2015 201 253 A1 describes a projection exposure apparatus having a shielding stop having an outer stop ring and an inner stop located inside a stop ring to block an inner region of a working light beam. The inner stop may be connected to the outer stop ring through a web and is held by the web. The web may be used as a heat-conducting element to dissipate heat from the inner stop.

[0009] DE 10 2017 219 266 A1 describes an optical system having a shield stop and a holder that holds the shield stop in a beam path. The optical system may have a separation device for separating thermal expansion from the shield stop to the holder. The separation device may include a spring, in particular a leaf spring, arranged between one of the webs and the holder. The shield stop may have a stop element and a plurality of webs, one side of which is connected to the stop element and the other side of which is connected to the holder. A spring may be arranged between one of the webs and the holder. The web may be formed as a one-piece with the stop element.

[0010] Thin holder elements have limited ability to provide sufficient rigidity against torque, which means that the shielded stop can only be stabilized when there is difficulty with tilt. Accordingly, DE 10 2019 205 959 A1 proposes shaping the peripheral area of ​​the stop so that when the stop is tilted about the tilt axis, the cross-sectional surface shielded by the stop remains constant, provided with a photonic crystal edge.

[0011] DE 10 2019 209 883 A1 proposes the use of a holding device for a shield stop in the pupil plane. The holding device includes an attachment element arranged outside the pupil plane to attach the holding device to a fixed world of the optical system. The attachment element may be designed as a wire or blade type and may be subjected to tensile force to support the holding device to the fixed world. The problem to be solved

[0012] The object of the present invention is to provide an optical system having an improved holder of a component, in particular a stationary element. means of solving the problem

[0013] This objective is achieved by an optical system of the type mentioned in the introduction, wherein the components are preferably releasedly connected to a wire-type web.

[0014] Unlike DE 10 2017 219 266 A1, which proposes that the stop element and the web be formed as a single piece, or unlike an integral connection in which the component is connected to the web, for example by welding, in the optical system according to the present invention, the component, particularly in the form of a stop element, is releasedly connected to the web. The releasely connected connection may be, for example, a clamping connection or a plug connection. Releasely connecting the component to the web simplifies the adjustment of the component. This is particularly advantageous in the case of a component in the form of a stop element where the photonic crystal edge must be accurately positioned relative to the beam path. Additionally, the releasely connected connection allows the component to be interchanged in a simple manner.

[0015] The web can be designed, for example, in a wire-like manner (in the form of a wire). This is particularly advantageous when preliminary tension is intended to be applied to the web (see below). However, in principle, it is also possible to design the web in the form of a thin blade, a thread, or a spring, for example. The web is typically extended in a straight line.

[0016] In one embodiment, at least one web spans the opening of the frame-type holder. In this embodiment, at least one web, specifically all webs, starts from a first position and extends along the frame-type holder to a second position on the opposite side of the frame-type holder. Thus, each web spanning the opening starts from the first position of the frame-type holder but does not terminate at the component, but rather extends further to the second position in the frame-type holder.

[0017] The geometry of the opening in the frame-type holder can be designed in various ways, for example, as a circular, elliptical, or rectangular shape. Each web may extend from the first side of the opening to the opposite side of the opening and, for example, perpendicularly to an additional web that also spans the opening. However, it is also possible for a web or multiple webs to extend, for example, along the diagonal of the rectangular or circular opening of the holder.

[0018] In another embodiment, the optical system comprises at least one preferably pre-tensioned spring, in particular in the form of a leaf spring, arranged between one of the webs and a holder. The spring enables pre-tension to be applied to each web. In particular, for details regarding the use of a spring to tension a wire-type web, refer to DE 10 2017 219 266 A1 mentioned in the introduction, the entire contents of which are incorporated by reference into this application. A web spanning an opening may, in each case, be pre-tensioned at the opposing end with the help of a spring.

[0019] In one embodiment, the optical system includes at least one length setting device for setting the length of at least one of the webs. The length setting device is preferably mounted on a pre-tensioned spring (and deflected together with said spring). The length setting device may have a winding element, for example, in the form of a cylindrical coil, and a (wire-type) web is wound on the winding element along a section of its length. The length of the web (outside the winding element) may be set by rotating the winding element about a longitudinal axis. The length setting device may also have (at least one) fixing element, for example, a clamping element, for fixing the winding element at an angular position with respect to the longitudinal axis. When the web has a desired length, the winding element is fixed at an angular position with the help of the fixing element, for example, by clamping the winding element in place so that it can no longer be rotated about a rotation axis.

[0020] By mounting a length setting device on a pre-tensioned spring, for example, a leaf spring, the web can be maintained in a pre-tensioned state even if the web length increases accidentally. Undesirable length increase can occur, for example, due to material yielding when the yield limit is exceeded or due to a rise in web temperature. When a length setting device is mounted on a pre-tensioned spring, the length setting device and the web connected thereto are deflected, and as a result, the pre-tension of the web can be maintained even in this case.

[0021] In one embodiment, a plate-shaped component, typically in the form of a stop element, is preferably attached to a support structure that does not protrude laterally beyond the plate-shaped component, and the web is releasedly connected to the support structure. The plate-shaped component may be attached to the support structure using a releasely connected connection or a permanent connected connection. In this case, the support structure forms an adapter to connect the plate-shaped component, which is typically very thin in this case, to the web. The support structure may be used to suspend the plate-shaped component or to support the plate-shaped component.

[0022] In this embodiment, the plate-shaped component typically has a very thin thickness of less than about 500 μm, for example, about 200 μm to 300 μm. The plate-shaped component may be, for example, a thin quartz glass plate produced by chemical etching or another very thin metal sheet (e.g., made of invar). If the component is a stationary element, the quartz glass plate typically has a reflective coating. The component may be connected integrally to the support structure, but it is also possible to connect the component to the support structure through form fit and / or force fit connections.

[0023] The material of the support structure may be, for example, Invar having a low coefficient of thermal expansion, or other suitable material specifically connected to the wire-type web in a releaseable manner. The releaseable connection between the support structure and the web may be realized, for example, by clamping the wire (possibly completely) into an indented recess of the support structure. However, the wire may also be guided through an opening or hole in, for example, a frame-type section of the support structure. With proper arrangement or alignment of the holes, the component may be positioned or maintained at a specific location in the optical system in this case.

[0024] In another embodiment, the plate-shaped component has at least one preferably rod-shaped retaining element (pin), and this rod-shaped retaining element includes a retaining section for a releaseable connection to one of the webs. The retaining element typically protrudes perpendicularly over the plate-shaped component. However, it goes without saying that the retaining element does not necessarily need to be aligned perpendicularly to the plate-shaped component. The retaining element may be formed as a single piece with the component, but the retaining element may also be pressed together with the component or connected to the component in other ways. The retaining element or retaining section is used to connect the component substantially in a point-like manner to each web. There are various possibilities for connecting the retaining section to the web:

[0025] In one improvement of this embodiment, the retaining section forms at least one preferably angled notch for a clamping connection to the web. In this case, the web is clamped to the notch. The notch may be designed (angled), for example, so that the wire web and the component are self-blocking. In this embodiment, typically, in each case, two retaining elements of the component are used for a releaseable connection to the web. These two retaining elements are preferably arranged opposite each other near the lateral edge of the component in each case. Various types of retaining elements may be provided to retain the component in two or more webs to ensure that the component and the wire web are self-blocking.

[0026] In an additional improvement, the retaining section forms at least one notch for wrapping with a wire-type web. In this improvement, the web (in this case, wire-type) is wound around the notch in the retaining section of the retaining element. To maintain the component in a desired position and alignment and to block its orientation, the wire-type web may be wound around an additional notch in the additional retaining element.

[0027] In another embodiment, the component has at least one recess or at least one hole through which the web is guided. This embodiment may be combined particularly with the previously described embodiment, in which the wire-type web is wound around the notch: in this case, one identical web may be wound around the notch of the retaining element and guided through the hole or recess to fix the orientation of the component. To fix the orientation of the component, it is advantageous for the distance between the wrapped retaining element and the hole or recess of the component to be as large as possible. This can be ensured, for example, by the hole / recess arranged at opposite edges of the retaining element and the component.

[0028] In one other embodiment, the hole is closed by a seal that surrounds the web and secures the web to the hole. In this case, the hole has a diameter larger than, for example, the wire web that is guided through the hole. To fix the position or orientation of the wire web relative to the hole, the wire web is embedded in the seal. An additional hole at the opposite periphery of the component may be used to guide the wire web through without being fixed to the component in this case, but it is also possible to secure an additional seal therein. The seal may be made of the same material as the wire web, for example, tungsten or rhenium.

[0029] In a further improvement of this embodiment, two holes are formed in the element, and a wire web is guided through the holes and wound around the component in a loop between the holes, more specifically around a section of the component formed between the two holes. In this way, a releaseable connection between the component and the wire web can also be ensured, allowing the component to be maintained in a desired alignment and position. In this case, the holes are typically through holes extending in a direction perpendicular to the plane of the component.

[0030] In another embodiment, the recess or hole has at least one curved section for bending the wire web when guided within the recess or hole and thereby securing or holding the web to or against the component. In this case, the wire web is held in the recess or hole or secured thereby by bracing and friction. Securing is understood to mean that the component cannot be easily displaced along the wire web due to bracing and / or friction. This embodiment is particularly advantageous when the component is pre-tensioned by a spring, as the wire web is bent to facilitate the securing of the component to the wire web, as described above. The recess may have a lid, that is, it may be formed in the manner of a hole having a curved section. In this case, the component may be held in place by friction.

[0031] To bend the wire web, the recess or hole is not formed as a straight line, but has at least one curved section between the first inlet end and the second outlet end of the web. It is not absolutely necessary for the recess or hole to have a width substantially corresponding to the width of the wire web. Rather, the recess or hole may have a much greater width than the wire web. In this case, the wire web may be bent at the recess or hole. For example, this can be achieved by guiding the wire web along the first sidewall of the recess or hole before the curved section of the recess or hole, and then guiding it along the second sidewall of the recess or hole after the curved section, which is laterally offset with respect to the first sidewall.

[0032] In the improvement of this embodiment, the curved section has an S-shaped geometry. In this case, the wire web can enter at the entrance end of the recess or hole and exit at the exit end of the recess or hole with a parallel offset resulting from the S-shaped section of the recess or hole. This guidance of the wire web has proven advantageous, particularly in the case of preliminary tensioning of the wire web (e.g., with the help of a leaf spring), because in this case, too large deflection of the wire web at the stop element is rather disadvantageous.

[0033] In another embodiment, the stop element forms a shield stop for blocking an internal portion of the beam path of an optical system. As previously described, the shield stop is designed to block or shield an internal portion of the cross-sectional area of ​​the beam path. The shield stop is typically used to cover a shield, such as a mirror, through which the beam path of the optical system extends. The shield stop, more specifically the outer boundary of the shield stop (corresponding to the outer photonic crystal edge), may be designed to correspond to a circular, elliptical, polygonal, particularly rectangular or square, or freeform shape. A shielded optical design, more specifically a projection system having a shielded pupil, is described, for example, in WO2006 / 069725 A1, the entire contents of which are incorporated by reference into the contents of this application.

[0034] The holder of the shield stop may typically be a support frame of an optical system to which the aperture stop is also attached, or a component connected to the support frame, for example, a stop module. However, the aperture stop may also be used as a holder for the shield stop, for example, as described in DE 10 2016 221 823 A1, the entire contents of which are incorporated by reference into the present application.

[0035] Instead of a shield stop, the component held by the holder may also be another type of stop element, e.g., an aperture stop, a stray light stop, a field stop, an ambient light stop, etc. Components that are not stop elements, e.g., actuators, etc., may also be held by the assistance of the web in the manner described above. Such components—including stop elements—may be held in a fixed alignment and at a fixed position in or with respect to the beam path of the optical system. For example, an aperture stop may be aligned in the manner described above so that the edge of the aperture stop forming the periphery of the aperture stop is precisely positioned at the periphery where the limit of the beam path of the optical system is realized.

[0036] In other embodiments, the component is preferably formed from a metal material selected from the group comprising aluminum, steel, or Invar. For example, a preferably plate-shaped component in the form of a stop element may be formed, for example, from a metal material, particularly a metal sheet. The use of a metal material having high thermal conductivity, particularly aluminum or copper, has proven advantageous for cooling components such as stop elements. Alternatively, the component may be formed from glass, for example, quartz glass, and may have a reflective coating.

[0037] In another embodiment, the optical system includes a projection system for imaging a photomask onto a wafer, and a stop element is arranged in the pupil plane region of the projection system. In this case, the optical system is designed as a lithography device and has a beamforming and illumination system in addition to the projection system. The illumination settings of the beamforming and illumination system are changed according to the structure being imaged onto the mask, which affects the radiated power or the thermal load of the stop element.

[0038] Further features and advantages of the present invention will become apparent from the following description of exemplary embodiments of the invention and the claims, with reference to the drawings illustrating details essential to the invention. Individual features of one variation of the invention may each be implemented individually or in any group of combinations. Brief explanation of the drawing

[0039] Exemplary embodiments are illustrated in the schematic drawings and described in the following description. In the drawings, FIG. 1a shows a schematic diagram of an EUV lithography apparatus, and FIG. 1b shows a schematic diagram of a DUV lithography apparatus, FIGS. 2A and 2B illustrate schematic diagrams of a shield stopper releasedly connected to a pre-tensioned wire-type web used to connect the shield stopper to a holder, and FIGS. 3a to 3c illustrate schematic diagrams of the shield stop of FIGS. 2a and 2b in which a wire-type web is releaseably connected to a support structure of the shield stop, FIGS. 4a and 4b illustrate schematic diagrams of a shield stop having a notched holder element to which a wire-type web is connected by clamping, and FIG. 5 illustrates a schematic diagram of a shield stop having a holder element having a notch for wrapping with a wire-type web and a hole for guiding the wire-type web, FIGS. 6A and 6B illustrate schematic cross-sectional views of two shielding stops having one and two holes, respectively, through which a wire-type web is guided, and FIGS. 7a to 7c illustrate schematic diagrams of a shield stop having a concave portion with a curved section having an S-shaped geometry for bending a wire-type web. In the following description of the drawing, the same reference number is used for identical or functionally identical components. Specific details for implementing the invention

[0040] FIG. 1a illustrates a schematic diagram of the configuration of an EUV lithography device (100A) comprising a beam forming and illumination system (102) and a projection system (104). The beam forming and illumination system (102) and the projection system (104) are each provided in a vacuum housing as shown in FIG. 1a, and each vacuum housing is evacuated with the help of an exhaust device (not shown). The vacuum housing is surrounded by a machine room (not shown) provided with a drive unit for mechanically moving or setting optical elements. Additionally, an electric controller, etc., may be provided in this machine room.

[0041] An EUV lithography device (100A) has an EUV light source (106A). A plasma source (or synchrotron) emitting radiation (108A) in the EUV range, for example, a wavelength range of 5 nm to 20 nm, may be provided as, for example, the EUV light source (106A). In a beam shaping and illumination system (102), the EUV radiation (108A) is focused and the desired operating wavelength is filtered from the EUV radiation (108A). The EUV radiation (108A) generated by the EUV light source (106A) has a relatively low transmittance through air, and for this reason, the beam guide space of the beam shaping and illumination system (102) and the projection system (104) is exhausted.

[0042] The beam shaping and illumination system (102) illustrated in FIG. 1a has five mirrors (110, 112, 114, 116, 118). After passing through the beam shaping and illumination system (102), EUV radiation (108A) is guided onto a photomask (reticle) (120). The photomask (120) can likewise be embodied as a reflective optical element and arranged outside the system (102, 104). Furthermore, the EUV radiation (108A) can be directed onto the photomask (120) by a mirror (122). The photomask (120) has a structure that is imaged onto a wafer (124), etc., in a reduced manner by a projection system (104).

[0043] The projection system (104) (also referred to as a projection lens) has six mirrors (M1 to M6) for imaging a photomask (120) on a wafer (124). It should be noted that the number of mirrors in the EUV lithography device (100A) is not limited to the number exemplified. More or fewer mirrors may also be provided. Furthermore, the front surface of the mirror is generally curved for beam shaping.

[0044] FIG. 1b illustrates a schematic diagram of a DUV lithography device (100B) comprising a beam forming and lighting system (102) and a projection system (104). As already described with reference to FIG. 1a, the beam forming and lighting system (102) and the projection system (104) may be arranged within a vacuum housing and / or surrounded by a machine room having a corresponding driving device.

[0045] The DUV lithography device (100B) has a DUV light source (106B). For example, an ArF excimer laser emitting radiation (108B) in the DUV range of 193 nm may be provided as the DUV light source (106B).

[0046] The beam shaping and illumination system (102) illustrated in FIG. 1b guides DUV radiation (108B) onto a photomask (120). The photomask (120) is embodied as a transmissive optical element and can be arranged outside the system (102, 104). The photomask (120) has a structure that is imaged onto a wafer (124), etc., in a reduced manner by a projection system (104).

[0047] The projection system (104) has a plurality of lens elements (128) and / or mirrors (130) for imaging a photomask (120) on a wafer (124). In this case, the individual lens elements (128) and / or mirrors (130) of the projection system (104) may be arranged symmetrically with respect to the optical axis (126) of the projection system (104). It should be noted that the number of lens elements and mirrors of the DUV lithography device (100B) is not limited to the number illustrated. More or fewer lens elements and / or mirrors may also be provided. Furthermore, the front surface of the mirror is generally curved for beam shaping.

[0048] The gap between the last lens element (128) and the wafer (124) can be replaced by a liquid medium (132) with a refractive index greater than 1. The liquid medium can be, for example, high-purity water. This configuration is also referred to as immersion lithography and increases resolution while imaging the photomask (120) onto the wafer (124).

[0049] FIG. 2a illustrates details of the EUV lithography device (100A) of FIG. 1a, more specifically, the projection system (104). The first mirror (M1) and the second mirror (M2) illustrated in FIG. 2a (see FIG. 1a) define a section of the beam path (200) of the projection system (104) or the EUV lithography device (100A). An aperture stop (202) having an aperture (204) with a circumferential edge (206) for defining the beam path (200) of the EUV lithography device (100A) at its outer edge (200a) is arranged between the first mirror (M1) and the second mirror (M2). The aperture stop (202) is used to determine the number of (entry-side) apertures of the projection system (104) by trimming the beam path (200) at the outer edge or by accurately defining the beam path.

[0050] A portion of the EUV radiation (108A) of the EUV lithography device incident on the area of ​​the aperture stop (202) adjacent to the edge (206) is absorbed by the material of the aperture stop (202), and as a result, the aperture stop is heated. In the example shown in FIG. 2a, the aperture stop (202) is designed in a plate shape and is made of a metal material, that is, a metal sheet. In particular, metal materials having a high thermal conductivity coefficient, such as aluminum, copper, or steel, have proven useful as materials for the aperture stop (202) (also shield stop (214) (see below)) because they allow direct cooling.

[0051] In the example illustrated in FIG. 2a, the aperture stop (202) is positioned just near the pupil plane (132) of the beam path (200) of the projection system (104). This arrangement is the reason why the aperture stop (202) is positioned at an angle (α) with respect to the horizontal plane forming the XY plane of the XYZ coordinate system.

[0052] The projection system (104) includes a perforation in one of the mirrors (M1 to M6), for example, a shield (not shown), through which the beam path (200) of the projection system (104) extends. The shield is intended to be covered with the help of a shield stop (214) to reduce the field dependence of the corresponding shielding, particularly (in the plane of the wafer (124)). The shield stop (214) is designed to cover or block an internal portion area (200b) of the beam path (200). That is, as part of the EUV radiation (108A) passes along the beam path (200) from the first mirror (M1) to the second mirror (M2), it is reflected or absorbed by the shield stop (214). The shield stop (214) is positioned entirely within the beam path (200) at or near the pupil plane (132), more specifically adjacent to the aperture stop (202). The shield stop (214) may have a reflective coating (not shown), and as a result, any heat introduction into the shield stop (214) is reduced. In the illustrated example, the shield stop (214) is designed as an elliptical plate and has an outer circumferential edge (220) used as a photonic crystal edge for shielding an inner portion region (200b) of the beam path (200), as can be easily identified in FIG. 2b. It goes without saying that the shield stop (214) does not necessarily have to have an elliptical design; rather, the outer boundary of the shield stop corresponding to the photonic crystal edge (220) may be designed to correspond to a circular, elliptical, polygonal, particularly rectangular or square, or a free shape.

[0053] The projection system (104) also includes a frame-type holder (216) that holds a shield stop (214) in the beam path (200). In the illustrated example, the holder (216) is attached to the stop module (228) of the projection system (104), more specifically to the side wall of the stop module (228). It is also possible for the holder (216) itself to form part of the stop module (228), or for the holder (216) to be embodied in the form of a support frame of the projection system (104) used to hold the mirrors (M1 to M6). The holding of the mirrors (M1 to M6) can be realized particularly by an actuator (e.g., a gravity compensator and / or a Lorentz actuator). As an alternative to the example illustrated in FIG. 2a, the aperture stop (202) itself can be used as a holder for the shield stop (214).

[0054] In the illustrated example, the shield stop (214) is connected to the holder (216) via two wire webs (218a, b), as can be seen in FIG. 2b. It goes without saying that the shield stop (214) may also be connected to the holder (216) via more than two wire webs (218a, b). The two wire webs (218a, b) extend across the opening (222) of the frame holder (216), that is, each web (218a, b) proceeding from one side of the frame holder (216), and do not terminate at the shield stop (214) but rather extend to the opposite side of the frame holder (216). In the example illustrated in FIG. 2b, the two wire webs (218a, b) extending across the opening (222) are aligned perpendicularly to each other, but this is not strictly necessary.

[0055] To thermally isolate the thermal expansion of the shield stop (214) from the holder (216), in the illustrated example, the projection system (104) has four spring elements in the form of leaf springs (224a-d) arranged between each end of the wire web (218a, b) and the frame holder (216). In the example illustrated in FIG. 2b, the leaf springs (224a-d) are mounted on each inner side of the frame holder (216). The leaf springs (224a-d) are pre-tensioned, that is, pre-tensioned the two wire webs (218a, b). For details regarding pre-tensioning using springs, refer once again to DE 10 2017 219 266 A1 mentioned in the introduction.

[0056] Likewise, as can be seen in FIG. 2b, the wire webs (218a, b) are not directly connected to the leaf springs (224a-d) but are connected via length setting elements (221a-d) (shown very schematically), which allow for setting the length of each wire web (218a, b). In the illustrated example, the length setting elements (221a-d) have a coil-shaped (cylindrical) winding element to which each end of one of the webs (218a, b) is attached. The winding element can be rotated around a longitudinal axis until each wire web (218a, b) has a desired length or tension. After tensioning, the winding element can be fixed at a desired angle position. The winding element can be fixed using a fixing element in the form of a clamping element that clamps the winding element between, for example, two clamping jaws. The clamping of the winding element is released only when the wire-type web (218a, b) needs to be (re)tensed.

[0057] Each length setting device (221a-d) is mounted on a pre-tensioned leaf spring (224a-d) and deflected together with the leaf spring. In this way, the pre-tension of the wire web (218a, b) is maintained even if the length of each wire web (218a, b) accidentally increases, for example, because the material of the web (218a, b) exceeds the yield limit or the web (218a, b) is heated.

[0058] As described above, the aperture stop (202) and the shield stop (214) are housed in a common stop module (228), and the stop module itself is part of a vacuum housing (not shown) that surrounds or encapsulates the (vacuum) environment of the second mirror (M2) (see FIG. 1a). The stop module (228) is mounted on the upper surface of a vacuum housing (226) (exemplified in FIG. 2a) that surrounds or encapsulates the first mirror (M1).

[0059] The shield stop (214) illustrated in FIGS. 2a and 2b is releasedly connected to the web (218a, b). Due to the releasely connected shield stop (214) to the web (218a, b), the adjustment is simplified and the exchange of the shield stop (214) becomes simpler. There are various possibilities for releasingly connecting the plate-shaped shield stop (214) to the web (218a, b), and some of these possibilities will be described in more detail below.

[0060] In the examples illustrated in FIGS. 3a through 3c, the shielding stop (214) is designed to be very thin and typically has a thickness (d) of less than about 500 μm, for example, about 200 μm to 300 μm. In the illustrated examples, the plate-shaped shielding stop (214) is designed as a quartz glass plate produced by chemical etching and having a reflective coating. Alternatively, the shielding stop (214) may also be formed as a thin metal sheet, for example, made of Invar.

[0061] In the example illustrated in FIGS. 3a and 3b, a thin plate-shaped shield stop (214) is attached to or held in place by a frame-shaped support structure (230) (adapter). As can be seen in FIG. 3a, a web (218a, b) is guided through a through hole (232) of the support structure (230) to releaseably connect the support structure (230) to the web (218a, b) and hold it in place. In the example illustrated in FIGS. 3a and 3b, the shield stop (214) is suspended from the frame-shaped support structure (230). To this end, an opening (234a, b) is formed in the shield stop (214), as can be seen in the cross-sectional view of FIG. 3b. A hook-shaped retaining element (236a, b) of a frame-type support structure (230) in which a shield stop (214) is suspended and maintained in that position is guided through an opening (234a, b). The hook-shaped retaining element (236a, b) can form a backward-curved profile in the material of the support structure (230) (e.g., Invar). In this case, the retaining element (236a, b) is initially guided through the opening (234a, b) of the shield stop (214) and then bent to create a hook-shaped or S-shaped geometry as shown in FIG. 3b.

[0062] In the example illustrated in FIG. 3c, the support structure (230) forms a support structure for a plate-shaped shield stop (214) designed as described in FIG. 3a and FIG. 3b. In this case, the shield stop (214) is attached to the upper surface of the support structure (230), for example, through an integral connection. In the example illustrated in FIG. 3c, the wire-shaped web (218a, b) is received in a recessed concave portion (238a, b) of the support structure (230) to which the wire-shaped web (218a, b) is (releaseably) clamped.

[0063] Likewise, as is evident in FIGS. 3a to 3c, the support structure (230) does not protrude laterally beyond the shield stop (214) so ​​as not to interfere with the function of blocking the inner part area (200b) of the beam path (200).

[0064] FIGS. 4a and 4b illustrate an example of a plate-shaped shield stop (214) held in place by six rod-shaped retaining elements (240a-f) (pins) on three wire-shaped webs (218a-c). Each of the three webs (218a-c) is releasedably connected to two of the six rod-shaped retaining elements (240a, b; 240c, d; 240e, f) in each case. In the illustrated example, each rod-shaped retaining element (240a-f) is pressed together with the material of the shield stop (214), but may also be attached to the shield stop (214) in a different way or formed as a single piece with the shield stop (214).

[0065] The rod-type retaining elements (240a-f) protrude vertically outward from the plane of the plate-type shielding stop (214) and, outside the plane of the shielding stop (214), have respective retaining sections (242d, 242e) for releaseable connection to respective wire-type webs (218b, 218c), as illustrated in FIG. 4a and 4b for the fourth and fifth rod-type retaining elements (240d, 240e). In the example illustrated in FIG. 4a and 4b, each retaining section (242d, 242e) has an angled notch (246d, 246e) to create a clamping connection with the associated wire-type web (218b, 218c). When a releaseable connection is established, the wire web (218b, 218c) is introduced into an angled notch (246d, 246e) designed so that the wire web (218b, 218c) and the shield stop (214) self-block. As can be seen in FIG. 4a, in each case, two of the retaining elements (240a, b; 240c, d; 240e, f) provided for connection to the same web (218a-c) are arranged on opposite sides in the outer peripheral region of the shield stop (214).

[0066] FIG. 5 illustrates a shield stop (214) having a rod-shaped retaining element (240a) that protrudes beyond the plane of the shield stop (214). The retaining element (240a) has a retaining section (242a) for a releaseable connection to a wire-shaped web (218a).

[0067] In the retaining section (242a), an annular circumferential notch (246a) is formed on the outer circumference of the rod-type retaining element (240a) to which the wire-type web (218a) is wound around the circumference. The hole (248) through which the wire-type web (218a) is guided is used to align the shield stop (214) or to block the orientation of the wire-type web (218a). In the example illustrated in FIG. 5, the hole (248) extends substantially radially outward and is formed on a protrusion on the side of the shield stop (214) located opposite the retaining element (240a). It goes without saying that, as an alternative to guidance through the hole (248), the wire-type web (218a) may also be wound around an additional rod-type retaining element to fix its orientation. FIG. 5 illustrates an example of a second wire-type web (218b) wound around each annular circumferential notch (246c, 246d) at two additional rod-type retaining elements (240c, 240d) positioned opposite each other. Likewise, it should be understood that at least one additional wire-type web may be connected to the shield stop (214) in a similar manner to fix its position in the beam path (200). Instead of being guided through the hole (248), the wire-type web (218a) may also be guided through a recess of the plate-type shield stop (214), for example, in the form of an indentation.

[0068] FIG. 6a illustrates a cross-sectional view of a shield stop (214) having a central opening as in FIG. 5. As in FIG. 5, a through hole (248) is formed in the shield stop (214) and aligned parallel to the plane in which the plate-shaped shield stop (214) extends. A wire-shaped web (218a) is guided through the hole (248). As can be seen in FIG. 6a, the hole (248) has a much larger diameter than the wire-shaped web (218a). To fix the position or orientation of the wire-shaped web (218a) relative to the hole (248), the wire-shaped web (218a) is embedded in a seal (250) that closes the hole (248) at one end. The seal portion (250) is releasedly connected to the hole (248), so that the wire web (218a) can be released from the shield stop portion (214). Likewise, as can be seen in FIG. 6a, the wire web (218a) is not secured to the hole (248) by an additional seal portion but is guided through the hole (248) at the other end of the shield stop portion (214). It goes without saying that such additional securing is also possible.

[0069] FIG. 6b illustrates an example of a shield stop (214) having two parallel holes (248a, b) that extend perpendicularly to the plate plane of the shield stop (214) and are arranged at a relatively small distance from each other. In this case, a wire-type web (218a) is guided through two adjacent holes (248a, b) and wound around a section of the shield stop (214) located between the two holes (248a, b) in a loop (252) manner so as to be releasedably connected to the shield stop (214) in this manner. In the manner shown in FIG. 6, the shield stop (214) can also be maintained in a desired position and alignment.

[0070] FIGS. 7a to 7c illustrate a shield stop (214) having a frame-shaped structure protruding over a plate-shaped region on a side facing away from the incident EUV radiation (100A), and four concave portions (254a-d) are formed in this structure. The frame-shaped structure and the plate-shaped region of the shield stop (214) are formed as a single piece in the illustrated example.

[0071] The first wire-type web (218a) is guided in the first and second recesses (254a, b) mounted at opposite positions along the frame-type structure. Correspondingly, the second wire-type web (254c, d) is guided in the third and fourth recesses (254c, d) likewise mounted at opposite positions along the frame-type structure of the shield stop (214).

[0072] As can be seen in FIGS. 7b and 7c, the concave portions (254a-d) each have a curved section (256a-d), and the curved section is used to slightly bend each wire-shaped web (218a, b) and thus hold the web at the shield stop (214) due to friction or bracing. Fixation is understood to mean that the shield stop (214) cannot be easily displaced along the wire-shaped web (218a, b) due to bracing and / or friction. The bending shown in FIGS. 7b and 7c is particularly advantageous when each wire-shaped web (218a, b) is pre-tensioned as shown in FIG. 2a, because pre-tensioning promotes fixation and holding of the shield stop (214) at the desired position and alignment.

[0073] As can be seen in FIG. 7c, the curved section (256c) is formed between the inlet end (258a) of the concave section (254c) and the outlet end (258b) of the concave section (254c), and in the illustrated example, has an S-shaped geometry. In the illustrated example, the wire web (218a) enters the concave section (254c) at the inlet end (258a) and exits at the outlet end (258b) of the concave section (254c), which has a parallel offset caused by the section (256c) of the concave section (254c) having an S-shaped curvature.

[0074] Likewise, as can be seen in FIGS. 7a through 7c, the width of each concave portion (254a-d) is much larger than the width of each wire-shaped web (218a, b) guided through the concave portion (254a-d). The bending of each web (218a, b) is realized by wire-shaped webs (218a, b) guided at the inlet end (258a) of the recess (254c) along the left side wall (260a) in the illustrated example and at the outlet end (258b) on the right side wall (260b) of the recess (254c) in the illustrated example, and the right wall (260b) of the recess (254c) is positioned slightly further to the left after the section (256c) having an S-shaped curvature than the left wall (260a) of the recess (254c) before the section (256c) having an S-shaped curvature. In this way, a slight lateral offset of the wire-shaped web (218b) is created when passing through the recess (254c) that causes the bending.

[0075] As can be seen in FIGS. 7b and 7c, the sidewalls (260a, 260b) have V-shaped indentations that protrude over the indentation and engage with each wire web (218a, b) in each section where the sidewalls are used to guide the wire webs (218a, b). Thus, the recesses (254a-d) also allow the shield stop (214) to be held or suspended in the beam path (200). Instead of the recesses (254a-d), it is also possible to use a hole or recess with a lid for holding or suspending the shield stop (214) in the beam path (200).

[0076] Instead of the aforementioned wire-type web (218a-c), it is also possible to connect various types of wire-type components, such as thin blades, threads, or spring-shaped webs, to the shield stop (214) in a releaseable manner. However, the wire-type web (218a-c) has proven to be particularly advantageous for causing preliminary tension. It goes without saying that instead of the shield stop (214), other components, such as other types of stops, such as the aperture stop (202) illustrated in FIG. 2a, the stray light stop, etc., may be attached to the holder (216) in the manner described above in a releaseable manner. Other components other than the stop element, such as actuators, may also be held releaseable to the web in the manner described above.

Claims

Claim 1 An optical system comprising a plate-shaped component (214), a frame-shaped holder (216) for holding the plate-shaped component (214), a plurality of webs (218a-c) for connecting the plate-shaped component (214) to the holder (216), and at least one length setting device (221a-d) for setting the length of one of the webs (218a, b), wherein the plate-shaped component (214) is detachably connected to the webs (218a-c), the plate-shaped component (214) is attached to a support structure (230), and the webs (218a, b) are detachably connected to the support structure (230). Claim 2 An optical system according to claim 1, wherein at least one web (218a-c) extends across the opening (222) of a frame-type holder (216). Claim 3 An optical system according to claim 1 or 2, further comprising at least one pre-tensioned spring (224a-d) arranged between one of the webs (218a-c) and the holder (216). Claim 4 In paragraph 3, the length setting device (221a-d) is mounted on a pre-tensioned spring (224a-d), an optical system. Claim 5 An optical system according to claim 1 or 2, wherein the support structure (230) does not protrude laterally beyond the plate-shaped component (214). Claim 6 An optical system according to claim 1 or 2, wherein the plate-shaped component (214) has at least one retaining element (240a-f) comprising a retaining section (242d, e) for a releaseable connection to one of the webs (218b, c). Claim 7 In claim 6, the retaining section (242d, e) has at least one notch (246d, e) for a clamping connection to one of the webs (218b, c), an optical system. Claim 8 In claim 6, the retaining section (242a) forms at least one notch (246a) for wrapping with one of the wire-type webs (218a), an optical system. Claim 9 An optical system according to claim 1 or 2, wherein the component (214) has at least one recess (254a-d) or at least one hole (248; ​​248a,b) in which the web (218a, b) is guided. Claim 10 An optical system in claim 9, wherein the hole (248) is closed by a seal (250) that surrounds the web (218a) and secures the web to the hole (248). Claim 11 An optical system according to claim 9, wherein two holes (248a, b) are formed in a component (214), a wire web (218a) is guided through the holes, and the wire web (218a) is wound around the component (214) in a loop (252) manner between the holes. Claim 12 An optical system according to claim 9, wherein the concave portion (254a-d) or hole has at least one curved section (256a-d) to bend the wire-shaped web (218a, b) when guided in the concave portion (254a-d) or hole and to secure the web to the component (214). Claim 13 In paragraph 12, the curved section (256a-d) is an optical system having an S-shaped geometry. Claim 14 An optical system according to claim 1 or 2, wherein the stopping element forms a shielding stopping portion (214) for blocking an inner portion region (200b) of the beam path (200) of the optical system (100A, 100B). Claim 15 An optical system according to claim 1 or 2, wherein the component (214) is formed of a metal material. Claim 16 An optical system according to claim 1 or 2, comprising a projection system (104) for imaging a photomask (120) onto a wafer (124), wherein a plate-shaped component (214) is a stationary element arranged in the pupil plane (132) region of the projection system (104).

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