DE102024202076A1 - Projection exposure system with a connecting element and method for designing the connecting element - Google Patents

Abstract

The invention relates to a projection exposure system (1,101) for semiconductor lithography, with a connecting element (30,40) for connecting two components of the projection exposure system (1,101), wherein the connecting element (30,40) has a hose (31,41). The projection exposure system (1,101) is characterized in that the hose (31,41) has at least one stiffening element (32,42.1,42.2,42.3).The invention further relates to a method for designing a connecting element (30,40) for a projection exposure system (1,101) for semiconductor lithography, wherein the connecting element (30.40) is designed to connect two components of the projection exposure system (1,101) and wherein the connecting element (30,40) has a hose (31,41), comprising the following method steps:- determining the occurring mechanical vibrations of a fluid flowing through the hose (31,41),- determining the arrangement of at least one stiffening element (32,42.1,42.2,42.3) on the hose (31,41).

Description

The invention relates to a projection exposure system with a connecting element and a method for designing the connecting element.

Projection exposure systems for semiconductor lithography are subject to extremely high requirements for image quality in order to be able to produce the desired microscopically small structures with as little error as possible. In a lithography process or a microlithography process, an illumination system illuminates a photolithographic mask, also known as a reticle. The light passing through the mask or the light reflected by the mask is projected by a projection optics onto a substrate (for example a wafer) coated with a light-sensitive layer (photoresist) and attached in the image plane of the projection optics in order to transfer the structural elements of the mask onto the light-sensitive coating of the substrate. The light used to image the mask onto the wafer is also referred to as the useful light of the projection exposure system. The requirements for the positioning of the image on the wafer and the intensity of the useful light are increased with each new generation, which leads to a higher heat load on the optical elements.

In cases of high heat load, it can be advantageous to control the temperature of the optical elements designed as mirrors in EUV projection exposure systems, i.e. in systems that are operated with electromagnetic radiation with a wavelength between 1 nm and 120 nm, in particular at 13.5 nm, using a water cooling system fed by a so-called water cabinet. Water-cooled mirrors and/or lenses can also be used in DUV projection exposure systems, i.e. in systems that are operated with electromagnetic radiation with a wavelength between 120 nm and 300 nm. The mirrors comprise fluid channels through which tempered water flows, thereby conducting the heat away from the optical effective surface, i.e. the mirror surface exposed to the light used to image the structural elements. Any dynamic or mechanical excitation must be avoided in order not to cause any disruption to the imaging processes of the projection exposure system. The excitations can be transmitted both via the supply and discharge lines of the tempered water, also known as structural mechanics, and via the fluid itself, i.e. the propagation of the mechanical vibrations in pressure waves in the water, which is also known as water pipe acoustics.

On the one hand, the water pipe acoustics can cause excitations through the flow of the fluid, i.e. the movement of the fluid in the fluid channel, which are referred to as flow-induced vibrations. On the other hand, mechanical excitations can be transmitted independently of the flow of the fluid, which are referred to as transferred excitations. The transferred excitations are caused, for example, by mechanical vibrations of supporting structures and are transferred to the fluid via the connection of the supply and discharge lines to these supporting structures. The flow-induced and transferred vibrations lead on the one hand to a change in the position of the mirrors and on the other hand to a deformation of the optical effective surface of the mirrors, with both disturbances having a negative influence on the image quality of the projection exposure system.

In order to reduce the described effects of flow-induced and transferred vibrations, hereinafter referred to as acoustic vibrations, a number of measures are already being taken in the state of the art, such as optimizing the fluid channels in the mirror, but also the supply lines from the water cabinet to the mirror. Due to the materials' tendency to outgas excessively and/or the risk of leakage due to mechanical damage, plastic hoses are not used as supply lines wherever possible. In the case of decoupling required in the connecting elements, plastic hose sections are enclosed in metal bellows or a metal bellows without a hose is used as a decoupling element. To dampen the acoustic vibrations, complex devices with passive (Helmholtz resonator) and active (actuator/sensor systems to reduce acoustic vibrations) components are also used. This has the disadvantage that the installation space required for the components must be available and/or the manufacturing costs are negatively affected.

The object of the present invention is to provide a device which eliminates the disadvantages of the prior art described above. A further object of the invention is to provide a method for designing a connecting element of a projection exposure system to reduce acoustic vibrations.

This object is achieved by a device and a method having the features of the independent claims. The subclaims relate to advantageous developments and variants of the invention.

A projection exposure system according to the invention for semiconductor lithography comprises a connecting element for connecting two components of the projection exposure system, wherein the connecting element has a hose. The projection exposure system is characterized in that the hose has at least one stiffening element. In the sense of the invention, a hose is defined by an outer shell that is elastic compared to a tube, which allows both a radial expansion or compression of the hose and a vibration of the hose relative to its longitudinal axis, such as a string of a musical instrument. Due to the radial expansion of the hose, mechanical vibrations transmitted via the fluid, the so-called acoustic vibrations, can be reduced by the material damping that occurs when the hose expands and contracts. A further reduction in the acoustic vibrations can be achieved by a suitable design of the natural frequencies and natural modes, whereby the acoustic vibrations can be reduced at least in individual frequencies or frequency ranges.

In a first embodiment, the stiffening element can be firmly connected to the hose at least in sections. The stiffening element can be connected to the hose, for example, at three points or surfaces arranged equidistantly on the circumference of the contact surface of the stiffening element.

In particular, the stiffening element can be connected to the hose around its entire circumference. This has the advantage that if the hose is compressed, no peeling forces act on the connection points in the radial direction, which increases the service life of the connection.

Furthermore, two segments of the hose created by the stiffening element can be of different lengths. The length of the segments influences the tendency of the hose to collapse when a force acts on it radially from the outside. Furthermore, the length of the segment influences the natural frequencies and natural modes of the segment in the radial and longitudinal directions already explained above. A different length of the two segments therefore enables two different damping effects of the segments on the fluid. In the sense of the invention, an existing hose which is arranged between two connection elements is divided into two segments by the at least one stiffening element. In the sense of the invention, a hose closed off by two connection elements therefore has no segment. This is only formed by the inventive arrangement of at least one stiffening element.

In a further embodiment, the distance between at least two stiffening elements or a connecting element and a connection element can be designed in such a way that a complete collapse of the segment can be prevented under operational loads. In the sense of the invention, complete collapse means contact between different areas of the inner surface of the hose, in particular a permanent "bonding" that is possible as a result. The operational loads, which in the sense of the invention are defined as the pressure difference between the areas inside and outside the hose, can, for example, be in a range of up to 101.3 kPa.

In a preferred embodiment, the stiffening element can be arranged on the outer circumference of the hose. The arrangement on the outer circumference has the advantage that the stiffening element cannot negatively influence the flow of the fluid flowing through the hose.

In particular, the hose can be arranged inside a tube. On the one hand, this has the advantage that the hose is protected from mechanical damage, especially during assembly of the projection exposure system. On the other hand, the tube prevents outgassing from the hose from reaching the area of the optical elements of the projection exposure system. This also prevents, for example, organic outgassing from coming into contact with the useful light used to image the structures onto a wafer, which can advantageously prevent the outgassing from splitting up and the resulting possible further contamination of the optical elements.

Furthermore, the stiffening element can be designed as a spacer between the hose and the pipe. As a result, the hose is at least non-positively connected via the spacers and an axial movement of the hose along its longitudinal axis can advantageously be avoided. A fixed distance between the stiffening elements or a connecting element and a stiffening element can ensure a stable natural frequency of the segment formed by the stiffening element.

In a further embodiment, the distance between hose and pipe can be designed in such a way that damping of acoustic vibrations is achieved by elastic expansion of the hose. The distance can determine the maximum expansion of the hose, which can adjust both the damping effect through material damping and the reduction of mechanical vibrations at certain frequencies.

As an alternative to arranging the stiffening element on the outer circumference of the hose, the stiffening element can be arranged on the inner circumference of the hose. This is particularly advantageous if a surrounding pipe is not required and/or the stiffening element has no negative influence on the fluid flowing in the pipe.

In a further embodiment, the stiffening element can be integrated into the hose. The integration can be achieved, for example, by inserting stiffening elements during the manufacture of the hose. The stiffening element can also be created by a locally increased wall thickness from the material of the hose, whereby the wall thickness in the area of the stiffening element can be significantly greater than the nominal wall thickness. The wall thickness depends, among other things, on the geometry of the hose, the number and distance of the stiffening elements from one another and the pressure difference and must be selected to suit the application.

Furthermore, the hose can have varying wall thicknesses within a segment. These are only small compared to the formation of stiffening elements explained above, but can, for example, enable damping of different frequencies or individual pressure pulses within a segment.

• - Ermittlung der auftretenden mechanischen Schwingungen eines den Schlauch durchströmenden Fluids.
• - Festlegung der Anordnung von mindestens einem Versteifungselemente am Schlauch.

A method according to the invention for designing a connecting element for a projection exposure system for semiconductor lithography, wherein the connecting element is designed to connect two components of the projection exposure system and wherein the connecting element has a hose, comprises the following method steps:

• - Determination of the occurring mechanical vibrations of a fluid flowing through the hose.
• - Determination of the arrangement of at least one stiffening element on the hose.

The mechanical vibrations can be determined as pressure changes or as transfer functions, i.e. the frequency-dependent change or amplification of the input pressure to the output pressure of a connecting element. The data determined in this way can then be used to determine the arrangement of the stiffening elements, i.e. the length of the segments.

Furthermore, at least one segment can have a predetermined natural frequency. Vibration of the segment at its natural frequency can not only cause pure material damping but also a reduction in individual frequencies of the acoustic vibrations.

In particular, the natural frequency can be designed in such a way that it resonates with a frequency of a mechanical vibration determined in the first method step. The resonance can be designed in such a way that the acoustic vibration is reduced, i.e. has a gain of significantly less than 1 in the transfer function. The reduction can affect a frequency range as well as a single frequency, whereby the reduction for the individual frequencies in the frequency range can be of different magnitudes.

Furthermore, the air gap between the hose and a pipe that at least partially surrounds it can be designed in such a way that the hose is protected from plastic expansion and/or bursting. The distance between the hose and the pipe (air gap) can therefore advantageously be designed in such a way that the damping effect is increased by material damping through the largest possible air gap and at the same time damage to the hose can be avoided. The air gap can also provide space for a laterally occurring natural frequency, i.e. vibration of the segment.

• 1 schematisch im Meridionalschnitt eine Projektionsbelichtungsanlage für die EUV-Projektionslithografie,
• 2 schematisch im Meridionalschnitt eine Projektionsbelichtungsanlage für die DUV-Projektionslithografie,
• 3a,b ein erste Ausführungsform der Erfindung,
• 4 eine weitere Ausführungsform der Erfindung, und
• 5 eine alternative Ausführung einer Vorrichtung.

In the following, embodiments and variants of the invention are explained in more detail with reference to the drawing.

• 1 schematic meridional section of a projection exposure system for EUV projection lithography,
• 2 schematic meridional section of a projection exposure system for DUV projection lithography,
• 3a ,b a first embodiment of the invention,
• 4 another embodiment of the invention, and
• 5 an alternative embodiment of a device.

In the following, first with reference to the 1 The essential components of a projection exposure system 1 for microlithography are described as an example. The description The basic structure of the projection exposure system 1 and its components are not to be understood as restrictive.

One embodiment of an illumination system 2 of the projection exposure system 1 has, in addition to a radiation source 3, an illumination optics 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 module separate from the rest of the illumination system. In this case, the illumination system does not include the light source 3.

A reticle 7 arranged in the object field 5 is illuminated. The reticle 7 is held by a reticle holder 8. The reticle holder 8 can be displaced via a reticle displacement drive 9, in particular in a scanning direction.

In the 1 For explanation, a Cartesian xyz coordinate system is shown. The x-direction runs perpendicular to the drawing plane. The y-direction runs horizontally and the z-direction runs vertically. The scanning direction runs in the 1 along the y-direction. The z-direction is perpendicular to the object plane 6.

The projection exposure system 1 comprises a projection optics 10. The projection optics 10 serves to image the object field 5 into an image field 11 in an image plane 12. The image plane 12 runs 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.

A structure on the reticle 7 is imaged onto a light-sensitive layer of a wafer 13 arranged in the area of the image field 11 in the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be displaced via a wafer displacement drive 15, in particular along the y-direction. The displacement of the reticle 7 on the one hand via the reticle displacement drive 9 and the wafer 13 on the other hand via the wafer displacement drive 15 can be synchronized with one another.

The radiation source 3 is an EUV radiation source. The radiation 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 has in particular a wavelength in the range between 5 nm and 30 nm. The radiation source 3 can be a plasma source, for example an LPP source (laser produced plasma, plasma generated using a laser) or a DPP source (gas discharged produced plasma, plasma generated by means of gas discharge). It can also be a synchrotron-based radiation source. The radiation source 3 can be a free-electron laser (FEL).

The illumination radiation 16 that emanates from the radiation source 3 is bundled by a collector 17. The collector 17 can be a collector with one or more ellipsoidal and/or hyperboloidal reflection surfaces. The at least one reflection surface of the collector 17 can be exposed to the illumination radiation 16 in grazing incidence (GI), i.e. with angles of incidence greater than 45° relative to the normal direction of the mirror surface, or in normal incidence (NI), i.e. with angles of incidence less than 45°. The collector 17 can be structured and/or coated on the one hand to optimize its reflectivity for the useful radiation and on the other hand to suppress stray light.

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 radiation source 3 and the collector 17, and the illumination optics 4.

The illumination optics 4 comprise a deflection mirror 19 and a first facet mirror 20 arranged downstream of this in the beam path. The deflection mirror 19 can be a flat deflection mirror or alternatively a mirror with a beam-influencing effect beyond the pure deflection effect. Alternatively or additionally, the deflection mirror 19 can be designed as a spectral filter which separates a useful light wavelength of the illumination radiation 16 from false light of a different wavelength. If the first facet mirror 20 is arranged in a plane of the illumination optics 4 which is optically conjugated to the object plane 6 as a field plane, it is also referred to as a field facet mirror. The first facet mirror 20 comprises a plurality of individual first facets 21, which are also referred to below as field facets. Of these facets 21, only one is shown in the 1 only a few examples are shown.

The first facets 21 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or partially circular edge contour. The first facets 21 can be designed as flat facets or alternatively as convex or concave curved facets.

As for example from the DE 10 2008 009 600 A1 As is known, the first facets 21 themselves can also 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, see the DE 10 2008 009 600 A1 referred to.

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

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

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.

The second facets 23 can also be macroscopic facets, which can be round, rectangular or hexagonal, for example, or alternatively facets composed of micromirrors. In this regard, reference is also made to the DE 10 2008 009 600 A1 referred to.

The second facets 23 can have planar or alternatively convex or concave curved reflection surfaces.

The illumination optics 4 thus forms a double-faceted system. This basic principle is also known as a honeycomb condenser (Fly's Eye Integrator).

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

With the help of the second facet mirror 22, the individual first facets 21 are imaged in the object field 5. The second facet mirror 22 is the last bundle-forming or actually the last mirror for the illumination radiation 16 in the beam path in front of the object field 5.

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

The lighting optics 4 have in the version shown in the 1 As shown, after the collector 17 there are exactly three mirrors, namely the deflection mirror 19, the field facet mirror 20 and the pupil facet mirror 22.

In a further embodiment of the illumination optics 4, the deflection mirror 19 can also be omitted, so that the illumination optics 4 can then have exactly two mirrors after the collector 17, namely the first facet mirror 20 and the second facet mirror 22.

The imaging of the first facets 21 by means of the second facets 23 or with the second facets 23 and a transmission optics into the object plane 6 is usually only an approximate imaging.

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

In the 1 In the example shown, the projection optics 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or another number of mirrors Mi are also possible. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 16. The projection optics 10 are doubly obscured optics. The projection optics 10 have a numerical aperture on the image side that is greater than 0.5 and can also be greater than 0.6 and can be, for example, 0.7 or 0.75.

Reflection surfaces of the mirrors Mi can be designed as free-form surfaces without a rotational symmetry axis. Alternatively, the reflection surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one rotational symmetry axis of the reflection surface shape. The mirrors Mi, just 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.

The projection optics 10 have a large object-image offset in the y-direction 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 can be approximately as large as a z-distance between the object plane 6 and the image plane 12.

The projection optics 10 can in particular be anamorphic. In particular, it has 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 means an image without image inversion. A negative sign for the image scale β means an image with image inversion.

The projection optics 10 thus leads to a reduction in the ratio 4:1 in the x-direction, i.e. in the direction perpendicular to the scanning direction.

The projection optics 10 leads to a reduction of 8:1 in the y-direction, i.e. in the scanning direction.

Other image scales are also possible. Image scales with the same sign and absolutely the same in the x and y directions, for example with absolute values of 0.125 or 0.25, are also possible.

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

Each of the pupil facets 23 is assigned to exactly one of the field facets 21 to form an illumination channel for illuminating the object field 5. This can result in particular in illumination according to the Köhler principle. The far field is broken down into a plurality of object fields 5 using the field facets 21. The field facets 21 generate a plurality of images of the intermediate focus on the pupil facets 23 assigned to them.

The field facets 21 are each imaged onto the reticle 7 by an associated pupil facet 23, superimposing one another, to illuminate the object field 5. The illumination of the object field 5 is in particular as homogeneous as possible. It preferably has a uniformity error of less than 2%. The field uniformity can be achieved by superimposing different illumination channels.

By arranging the pupil facets, the illumination of the entrance pupil of the projection optics 10 can be defined geometrically. By selecting the illumination channels, in particular the subset of the pupil facets that guide light, the intensity distribution in the entrance pupil of the projection optics 10 can be set. This intensity distribution is also referred to as the illumination setting.

A likewise 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.

In the following, further aspects and details of the illumination of the object field 5 and in particular of the entrance pupil of the projection optics 10 are described.

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

The entrance pupil of the projection optics 10 cannot usually be illuminated precisely with the pupil facet mirror 22. When the projection optics 10 images the center of the pupil facet mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, a surface can be found in which the pairwise determined distance of the aperture rays is minimal. This surface represents the entrance pupil or a surface conjugated to it in spatial space. In particular, this surface shows a finite curvature.

It may be that the projection optics have 10 different positions of the entrance pupil for the tangential and the sagittal beam path. In this case, an imaging element element, in particular an optical component of the transmission optics, between the second facet mirror 22 and the reticle 7. With the help of this optical element, the different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

In the 1 In the arrangement of the components of the illumination optics 4 shown, the pupil facet mirror 22 is arranged in a surface conjugated to the entrance pupil of the projection optics 10. The field facet mirror 20 is arranged tilted to the object plane 6. The first facet mirror 20 is arranged tilted to an arrangement plane that is defined by the deflection mirror 19.

The first facet mirror 20 is arranged tilted to an arrangement plane which is defined by the second facet mirror 22.

2 shows schematically in meridional section another projection exposure system 101 for DUV projection lithography, in which the invention can also be used.

The structure of the projection exposure system 101 and the principle of imaging is comparable to that in 1 described structure and procedure. Identical components are provided with a 100% difference 1 raised reference numerals, the reference numerals in 2 So start with 101.

In contrast to a 1 Due to the longer wavelength of the DUV radiation 116 used as useful light in the range from 100 nm to 300 nm, in particular from 193 nm, in the EUV projection exposure system 101 described, refractive, diffractive and/or reflective optical elements 117, such as lenses, mirrors, prisms, cover plates and the like, can be used for imaging or for illumination in the DUV projection exposure system 101. The projection exposure system 101 essentially comprises an illumination system 102, a reticle holder 108 for receiving and precisely positioning a reticle 107 provided with a structure, by means of which the later structures on a wafer 113 are determined, a wafer holder 114 for holding, moving and precisely positioning this wafer 113 and a projection lens 110 with a plurality of optical elements 117, which are held via mounts 118 in a lens housing 119 of the projection lens 110.

The illumination system 102 provides a DUV radiation 116 required for imaging the reticle 107 on the wafer 113. A laser, a plasma source or the like can be used as a source for this radiation 116. The radiation 116 is shaped in the illumination system 102 via optical elements such that the DUV radiation 116 has the desired properties with regard to diameter, polarization, shape of the wavefront and the like when it strikes the reticle 107.

The structure of the subsequent projection optics 101 with the lens housing 119 does not differ in principle from that in 1 described structure and is therefore not described further.

3 shows a detail of a connecting element 30 according to the invention designed as a hose 31. The connecting element 30 can be used to connect individual components, such as a tempered lighting system 2, 102 ( 1 , 2 ) a projection exposure system 1, 101 and a water cabinet for the provision and preparation of a tempering fluid.

The hose 31 has a stiffening element 32 at one point, which is arranged on the hose between the two connection elements 37.1, 37.2. The elements 32, 37.1, 37.2 are each firmly connected to the outside of the hose 31 via a contact surface 34.1, 34.2, 34.3. The stiffening element 32 divides the hose 31 into two segments 35.1, 35.2, which have the lengths l _S1 , l _S2 . The lengths l _S1 , l _S2 of the segments 35.1, 35.2 can be individually adjusted.

The hose 31 is connected to a pipe 36 ( 3b) tied together.

The stiffening element 32 also shortens the free hose length, i.e. the distance between the two connection elements 37.1, 37.2 of the hose 31. This advantageously prevents the hose 31 from collapsing completely in the event of a negative pressure in the hose or an overpressure outside the hose 31, i.e. opposing sections of the inner surface from touching each other. Depending on the size and duration of the negative pressure, this can lead to the hose 31 sticking together and thus to an infarction of the hose 31. The segment lengths I _S1 , I _S2 are therefore designed to be as long as possible so that contact between opposing areas of the inner surface of the hose 31 is advantageously avoided at the negative pressures to be expected.

3b shows the connecting element 30 with the hose 31 connected to the pipe 36 via the stiffening element 32 and the connecting elements 37.1, 37.2. The thickness of the elements 32, 37.1, 37.2 defines a distance d _RS between the outer surface of the hose 31 and the inner surface of the pipe 36, whereby the hose 31 is protected from damage by local plastic deformation or bursting in the event of excessive pressure. The distance d _SR is selected to be large enough that the hose 31 can expand when a pressure wave occurs in the fluid flowing through the hose 31. The expansion of the hose 31 in the area of the segments 35.1, 35.2 causes a damping of the pressure wave due to the material damping of the hose material.

If the segments 35.1, 35.2 are designed in such a way that their natural frequency corresponds to a frequency or the natural frequency of the hose 31 corresponds to the frequency of a pressure fluctuation transmitted in the fluid, the pressure fluctuation at this frequency can be cancelled out or greatly reduced by the phase-shifted vibrations of the hose 31. However, this effect is to be regarded as subordinate compared to the material damping due to the pressure fluctuations in the fluid that are difficult to predict and the natural frequency of the hose 31 that cannot be subsequently adjusted.

The tube 36 also has the function of protecting the hose 31 from mechanical damage, particularly during assembly of the projection exposure system. In the case of using a connecting element in a projection exposure system 1, 101 ( 1 , 2 ), the tube 36 can also accommodate other components, in particular the optical elements of the projection optics 10 ( 1 ) against outgassing of the hose 31.

4 shows a further embodiment of a detail of a connecting element 40, in which three stiffening rings 42.1, 42.2, 42.3 are arranged inside the hose 41 and are connected to it via the contact surfaces 44.1, 44.2, 44.3. The connecting elements are in the 4 not shown. This embodiment can be used in particular in cases in which the outgassing of the tube 31 is not critical, such as in the area outside the optical systems of a projection exposure system 1,101.

Alternatively, the stiffening elements can also be integrated into hose 31 or realized by a partially significantly increased wall thickness.

5 shows a further embodiment of a connecting element 50, not claimed here, which eliminates the same disadvantages of the connecting elements known from the prior art, wherein the features differ from the embodiments shown above. The connecting element 50 comprises a damping element designed as a hose 51, wherein the hose 51 is arranged in the fluid flow, i.e. the fluid flows around it. The damping effect of pressure fluctuations occurring in the fluid is based, as described above, mainly on the deformation of the hose 51, i.e. on the material damping of the material used for the hose 51.

The hose 51 is connected via an adapter 58 to a flange 57 formed on the pipe 56, wherein the adapter 58 is connected to the flange 57 at an interface 53.

The hose 51 is adequately protected from sticking together due to contact between opposing areas of the inner surface of the hose 51 in the event of excess pressure by the internal pressure present in the closed volume of the hose 51. The gas volume acting as a compressed spring in conjunction with the restoring force stored in the elastically deformed material of the hose 51 is sufficient in the vast majority of cases to also release any possible sticking.

At the same time, a system-related maximum increase in the pressure in the hose 51 by 1 bar, namely during a complete evacuation of the pipe 56, is also known, whereby a plastic deformation or bursting of the hose 51 can be easily avoided by a corresponding limitation of the internal pressure.

As an alternative to the 5 As shown in the hose 51, the damping element can also be made of a solid material. This can be adapted to the predetermined requirements by selecting a suitable material and stiffness. It is important to have sufficient elasticity and high material damping, which, as mentioned above, significantly influences the damping effect of the damping element.

list of reference symbols

1

projection exposure system

2

lighting system

3

radiation source

4

lighting optics

5

object field

6

object level

7

reticle

8

reticle holder

9

reticle displacement drive

10

projection optics

11

image field

12

image plane

13

wafer

14

wafer holder

15

wafer relocation drive

16

EUV radiation

17

collector

18

intermediate focal plane

19

deflecting mirror

20

faceted mirror

21

facets

22

faceted mirror

23

facets

30

connecting element

31

Hose

32

stiffening element

33

interface to the pipe

34

contact surface with hose

35.1,35.2

distance between connecting elements

36

Pipe

37.1,37.2

connecting element

40

connecting element

41

Hose

42.1-42.3

stiffening element

44

contact surface with hose

45.1,45.2

segments

50

connecting element

51

Hose

53

pipe interface

56

Pipe

57

flange

58

adapter flange

101

projection exposure system

102

lighting system

107

reticle

108

reticle holder

110

projection optics

113

wafer

114

wafer holder

116

DUV radiation

117

optical element

118

versions

119

lens housing

M1-M6

Mirror

IS1, IS2

segment length

dRS

distance between pipe and hose

QUOTES INCLUDED IN THE DESCRIPTION

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Cited patent literature

• DE 10 2008 009 600 A1 [0037, 0041]
• US 2006/0132747 A1 [0039]
• EP 1 614 008 B1 [0039]
• US 6,573,978 [0039]
• DE 10 2017 220 586 A1 [0044]
• US 2018/0074303 A1 [0058]

Claims (16)

Projection exposure system (1,101) for semiconductor lithography, with a connecting element (30,40) for connecting two components of the projection exposure system (1,101), wherein the connecting element (30,40) has a hose (31,41), characterized in that the hose (31,41) has at least one stiffening element (32,42.1,42.2,42.3). Projection exposure system (1,101) according to claim 1 , characterized in that the stiffening element (32,42.1,42.2,42.3) is firmly connected to the hose (31,41) at least in sections. Projection exposure system (1,101) according to claim 1 , characterized in that the stiffening element (32,42.1,42.2,42.3) is connected to the hose (31,41) over its entire circumference. Projection exposure system (1,101) according to one of the preceding claims, characterized in that two segments (35.1,35.2,45.1,45.2) of the hose (31,41) created by a stiffening element (32,42.1,42.2,42.3) are of different lengths. Projection exposure system (1,101) according to claim 4 , characterized in that the distance between at least two stiffening elements (32,42.1,42.2,42.3) or at least one connecting element (37.1,37.2) and one stiffening element (32) is designed such that a complete collapse of the segment (35.1,35.2,45.1,45.2) is prevented under operational loads. Projection exposure system (1,101) according to one of the preceding claims, characterized in that the hose (31,41) is arranged within a tube (36). Projection exposure system (1,101) according to one of the preceding claims, characterized in that the stiffening element (32,42.1,42.2,42.3) is arranged on the outer circumference of the hose (31,41). Projection exposure system (1,101) according to claim 7 , characterized in that the stiffening element (32,42.1,42.2,42.3) is designed as a spacer between the hose (31,41) and the pipe (36). Projection exposure system (1,101) according to claim 8 , characterized in that the distance between the hose (31,41) and the pipe (36) is designed such that a damping of acoustic vibrations is brought about by an elastic expansion of the hose (31,41). Projection exposure system (1,101) according to one of the Claims 1 until 6 , characterized in that the stiffening element (32,42.1,42.2,42.3) is arranged on the inner circumference of the hose (31,41). Projection exposure system (1,101) according to one of the Claims 1 until 9 , characterized in that the stiffening element (32,42.1,42.2,42.3) is integrated in the hose (31,41). Projection exposure system (1,101) according to one of the Claims 4 until 11 , characterized in that the hose (31,41) has varying wall thicknesses within a segment. Method for designing a connecting element (30,40) for a projection exposure system (1,101) for semiconductor lithography, wherein the connecting element (30.40) is designed to connect two components of the projection exposure system (1,101) and wherein the connecting element (30,40) has a hose (31,41), comprising the following method steps: - determining the occurring mechanical vibrations of a fluid flowing through the hose (31,41), - determining the arrangement of at least one stiffening element (32,42.1,42.2,42.3) on the hose (31,41). procedure according to claim 13 , characterized in that at least one segment (35.1,35.2,45.1,45.2) has a predetermined natural frequency. procedure according to claim 14 , characterized in that the natural frequency of the segment (35.1,35.2,45.1,45.2) resonates with a mechanical vibration occurring in a fluid. Method according to one of the Claims 13 until 15 , characterized in that an air gap (d _RS ) between the hose (31,41) and a pipe (36) is designed such that the hose (31,41) is protected against plastic expansion and/or bursting.

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