DE102016210698A1 - Optical arrangement and method for operating the optical arrangement - Google Patents

Abstract

The invention relates to an optical arrangement (1), in particular for EUV lithography, comprising: at least one housing (4a), in which at least one reflective optical element (13, 14, 15) is arranged, which has a main body (13b, 14b , 15b) on which a reflective surface (13a, 14a, 15a) is formed, and at least one holder (21a, 21b; 22a, 22b; 23a, 23b) on which the base body (13b, 14b, 15b) of reflective optical element (13, 14, 15) is preferably movably mounted. The optical arrangement (1) comprises at least one sheath (16) which comprises at least the at least one holder (21a, 21b, 22a, 22b, 23a, 23b) and preferably the base body (13b, 14b, 15b) of the reflective optical element (13 , 14, 15) at least partially enveloped and the an ambient space (20) in which at least one of the sheath (16) wrapped portion of the holder, in particular the entire holder (21a, 21b, 22a, 22b, 23a, 23b) is arranged , seals against an interior (19) of the housing (4a) in which the reflective surface (13a, 14a, 15a) of the reflective optical element (13, 14, 15) is located, the shell (16) having at least one flexible portion (16a) for enabling movement manipulation of the optical element (13, 14, 15). The invention also relates to a method for operating such an optical arrangement (1).

Description

Background of the invention

The invention relates to an optical arrangement, in particular for EUV lithography, comprising: at least one housing, in which at least one reflective optical element is arranged, which has a base body, on which a reflective surface is formed, and at least one holder on which the main body of the reflective optical element is preferably movably mounted.

For the purposes of this application, an optical arrangement for EUV lithography or an EUV lithography system is understood to mean an optical system which can be used in the field of EUV lithography. In addition to an EUV lithography system, which is used for the production of semiconductor devices, the optical system can be, for example, an inspection system for inspecting a photomask used in an EUV lithography system (also referred to below as a reticle) for inspecting a semiconductor substrate to be patterned (described in US Pat Hereinafter also referred to as wafers) or a metrology system which is used for measuring an EUV lithography system or parts thereof, for example for measuring a projection system.

When using EUV radiation at wavelengths in the range between about 5 nm and about 30 nm, for example in EUV lithography systems, the contamination of reflective optical elements by contaminants is a particular problem. Contaminating substances can, for example, in an EUV light source in which a target material, for example in the form of tin droplets, is used to generate the EUV radiation and in which part of the tin droplets are vaporized and converted into the gas phase. However, contaminants can also be generated by components which are arranged in the vicinity of the reflecting optical elements, as a rule non-optical components, if they outgas or release into the environment contaminants.

In the US 2012/0086925 A1 a method for avoiding the passage of contaminating gaseous substances through an opening of an enclosure of an EUV lithography system is described, in which at least one of the contaminants deflecting, in particular its flow direction is directed counter-current gas flow in the region of the opening. The gas flow and the EUV radiation are generated in a pulsed manner and the pulse rate of the gas flow is determined as a function of the pulse rate of the contaminants released under the action of the pulsed EUV radiation.

In the US 8,585,224 B2 It is proposed to install in the interior of a housing, in which a reflective optical element is arranged, a vacuum housing which surrounds at least the reflective surface of the optical element. By the vacuum housing, a partial volume of the interior, which contains the optical surface of the optical element to be separated from the remaining interior of the housing (so-called "mini-environment"). This is intended to achieve an at least partial shielding of the optical surface from non-optical materials which are present in the remaining interior of the housing and which outgas any contaminating substances. Since movable optical elements are used in EUV lithography systems, the vacuum housing can be mounted such that a narrow gap remains between the vacuum housing and the surface of the reflective optical element. Alternatively, a flexible vacuum component (eg, a metal bellows (bellows)) may be provided to cover this gap. The vacuum housing typically has an opening which connects the sub-volume formed in the vacuum housing to the remainder of the interior of the housing to guide a purge gas flow from the sub-volume into the interior of the housing.

In the DE 10 2009 029 282 A1 a similar optical arrangement is described in which a sub-housing surrounds at least one incident on the optical element during operation of the optical arrangement beam. The interior of the sub-housing ("mini-environment") communicates with the exterior of the sub-housing via at least one opening in connection. In the region of the opening, at least one flow-guiding section is formed, which deflects a purge-gas flow extending from the interior to the exterior of the sub-housing through the opening at least once in its direction. If necessary, a gap may be formed between the sub-housing and the optical element, which permits positional manipulation of the optical element.

In the solutions proposed above, it is necessary that not only the existing in the interior of the sub-housing or the vacuum housing components meet high cleanliness requirements to avoid contamination of the existing reflective optical surfaces, but also the remaining, in the interior of the Housing arranged components. However, this leads to a high cleaning effort and also limits the selection of components and the materials that may be used in the environment of the optical elements. The necessity of suppressing contaminants (particles and outgassing) from the immediate surroundings of the reflective optical elements makes the optical arrangement very complex.

Due to the usually existing connection to the interior of the housing contamination can be prevented by the "mini-environments" usually only partially, i. due to the gaps or openings, the suppression rates may not always be sufficient, in particular for molecules containing Zn or Sn. Also, in this solution, it is necessary to construct very cleanly the components arranged in the mini-environment around the optical surfaces of the reflective optical elements, to manufacture and, if necessary, to control them for their cleanliness, e.g. by outgassing measurements. Generally common technical solutions such as lubrication, the arrangement of electronic boards, in the immediate vicinity of the optical surfaces must be completely eliminated as a rule.

Object of the invention

The object of the invention is to provide an optical arrangement and a method for operating such an optical arrangement in which contaminations are reduced at reflecting surfaces of optical elements, at the same time increasing the flexibility in the selection of arranged in the vicinity of the optical elements components ,

Subject of the invention

This object is achieved by an optical arrangement of the type mentioned, which has at least one sheath which at least partially surrounds at least the at least one holder and preferably the body of the reflective optical element and an ambient space in which at least one of the sheath e.g. annularly enveloped portion of the at least one holder, in particular the entire holder is arranged, seals against an inner space of the housing in which the optical surface of the reflective optical element is located, wherein the sleeve for facilitating movement manipulation of the optical element has at least one flexible portion ,

Through the envelope, the interior with the reflective surface can be vacuum-sealed or delimited from the surrounding space, so that the holder or section of the holder arranged in the surrounding space, as well as possibly existing components such as fastening elements, drives or actuators, electronics, Sensors in the critical area in or near the beam path, in which the reflective surface is arranged in the operation of the optical arrangement, can emit or outgas no contaminants. The contaminants may be both macroscopic particles, e.g. to deal with chips, as well as microscopic particles or atomic or molecular contaminants.

Unlike the existing solutions contaminants are not suppressed in this way, but it is their penetration into the beam path and thus the achievement of the reflective surfaces prevented. In this way, better and possibly more cost-effective holders or holders as well as drives or actuators for the reflective optical elements can be used. Through the use of improved holders or actuators, the positions of the reflective optical elements can be better controlled. Also, if necessary, there are great savings in the design, manufacture and manufacture of the optical assembly, especially if this is an EUV lithography equipment. In addition, the potentially more "dirty" technical solutions which would not be possible in the fulfillment of the cleanliness requirements previously imposed on the components arranged in the vicinity of the reflective optical elements can be used in the surrounding space.

In the case of a reflective optical element which is comparatively large and which therefore may have a plurality of holders, each holder can be surrounded individually, typically annular, with a flexible envelope. It proves to be advantageous that the reflective optical element or the base body itself is not burdened by the shell mechanically or only at the points where the main body of the optical element is already mechanically stressed by the contact with the holders already. Optionally, a respective holder may be only partially, ie only arranged along a portion in the surrounding space in which it is surrounded by the shell. In this case, the holder typically has a portion rigidly connected to the main body of the optical element, which is movable together with the main body and to which the shell is attached. A portion of this section typically projects into the interior and is not surrounded by the shell in this case. A further portion of the holder rigidly connected to a housing component of the housing of the optical arrangement and a portion of the portion of the holder connected to the main body of the optical element is typically arranged in the surrounding space and surrounded by the casing. Typically, it is inside the shell Surrounding portion of the holder, ie in the surrounding space, an actuator for moving the holder or the optical element.

The base body of the mirror is typically a substrate to which a reflective coating is applied. However, the base body can also have further components which are connected to the substrate and which are typically moved together with the latter relative to the housing. When the optical assembly is an EUV lithography system, the reflective surface is typically formed on a coating that is suitable for either normal incidence, i. for EUV radiation incident on the surface of the reflective optical element at angles of incidence typically less than about 45 ° to the surface normal, or for grazing incidence, i. for EUV radiation impinging on the surface of the reflective optical element at angles of incidence typically greater than about 60 ° to the surface normal.

In the first case, the reflective coating is typically a multilayer coating. Such a multilayer coating generally has alternating individual layers of a first material and a second material with different refractive indices. The multilayer reflective coating, and thus materials used for the monolayers, are typically optimized for reflection of EUV radiation at a given wavelength, which generally corresponds to the useful wavelength of the EUV lithography system in which the optical element is employed. For EUV radiation, which has a wavelength of approximately 13.5 nm, the materials are typically silicon and molybdenum.

A reflective coating designed for grazing incidence typically has a maximum of reflectivity at at least an incident angle greater than 60 °. Such a reflective coating is typically formed of at least one layer of a material that has a low refractive index and low absorption for the grazing incidence EUV radiation. The reflective coating may include a metallic material or be formed of a metallic material, for example Mo, Ru or Nb.

In one embodiment, the shell, in which the at least one holder is arranged, connects the main body of the reflective optical element to the housing. If a plurality of reflective optical elements are arranged in the housing, they can each be individually sealed with a sleeve against the respective bracket or against the interior in which the beam path is located.

In one embodiment, the sheath envelops a beam path formed in the interior of the housing during operation of the optical arrangement, in which the at least one reflective surface is arranged, completely and seals the beam path in the interior of the housing from the surrounding space. In this case, the beam path is completely enveloped or surrounded by a (optionally flexible) cover, in which ideally only the reflective surfaces of the reflective elements are arranged, so that the cover has a (nearly) hermetic seal against the interior Environmental space forms.

In a further development, the envelope which surrounds the beam path consists of flexible sections, ie the envelope has no rigid sections. In this case, the beam path may, for example, be surrounded by a substantially tubular shell in which ideally only the reflecting surfaces of the reflective optical elements are arranged. The shell may in this example be a flexible plastic component or the shell may be composed of a plurality of flexible plastic components, which are formed, for example, as films (eg ^Kapton® or ^Teflon® ). The sheath, which has only flexible portions, is usually detachably mounted in the housing or on the reflective optical elements, more precisely on their basic bodies, and can therefore be exchanged in a simple manner, if necessary.

If the optical path of the optical arrangement runs through two or more housings, the entire optical path of the optical arrangement may possibly be enveloped by a single coherent envelope, which as a rule has a plurality of interconnected flexible sections. For example, in the case of an optical arrangement in the form of an EUV lithography system, the beam path can be arranged from an EUV light source, which is arranged in a first housing, via an illumination system, which forms a second housing, to form a mask, which is optionally arranged in a further housing is completely surrounded by the shell. The same applies to the beam path leading from the mask to a photosensitive substrate (wafer), i. this can also be completely surrounded by the flexible sheath in housings lying between the mask and the wafer, for example a projection system.

In one embodiment, the interior of the housing communicates with at least one vacuum pump and is preferably gas-tightly isolated from the ambient space. The vacuum Pump is used to create a vacuum in the interior, which typically has an opening for connection to the vacuum pump. The vacuum pump (s) usually pump only the interior, ie they are typically not used for pumping the ambient space, as are used for this purpose usually own vacuum pumps. If the envelope completely surrounds the beam path in the housing, the opening for the vacuum pump is formed in the envelope. A further opening in the interior or in the shell is typically provided for the inlet of a background gas into the interior. If necessary, further openings can be provided in the shell or in the housing, which openings serve for the passage of the beam path, for example, to a further housing. Usually, or in normal operation, there is no connection to the ambient space, but the production of such a connection may possibly be necessary if a pressure equalization between the interior and the surrounding space is to take place (see below).

In one embodiment, the housing has at least one opening for the passage of the beam path and the at least one opening is sealed by a further flexible portion of the sheath. The further flexible section of the casing may in particular be a plastic component in the form of a (flexible) membrane, ie a very thin, flexible film. Although in principle there are no transparent materials for radiation in the EUV wavelength range, the further flexible section or the membrane may have a thickness which is so small that the beam path can pass through the membrane without a significant proportion of the EUV radiation being transmitted through the membrane. Radiation is absorbed. The flexible portion or the membrane may, for example, have a thickness of 50 μm or less, possibly of 10 μm or less, in particular of 1 μm or less. Such a membrane is also referred to as a so-called pellicle and is used in lithography for the protection of wafers or masks from contaminants, for example as described in US Pat US Pat. No. 7,829,248 B2 for a mask pellicle system for lithography, in which a pellicle is disposed in the vicinity of a transparent substrate of a mask.

The material of the membrane can be, for example, Si, Zr, Ru, Rh, Nb, Mo, B or silicon nitride, as described in US Pat US 2010/0195076 A1 which describes an optical membrane element for a lithography apparatus comprising at least one membrane layer and a frame which at least partially surrounds the at least one membrane layer and to which at least a part of the edge of the membrane layer is attached, wherein at least one clamping element is provided in order to clamp the membrane layer adjustable.

In a further embodiment, the holders of a plurality of reflective optical elements are arranged in a common surrounding space. For the purposes of this application, a common ambient space is understood to mean an ambient space which has a plurality of partial areas which communicate with one another through openings or which are formed by the space remaining in the housing outside the enclosure. Typically, a substantially uniform pressure prevails in the common ambient space, and the common ambient space can therefore typically be evacuated using a single vacuum pump. It is understood that instead of a common environment space, if necessary, a plurality of gas-tight separated environmental spaces may be provided in the optical arrangement.

If the ambient space is separated from the "clean" interior in a gastight manner, then not only the strict cleanliness requirements for the surrounding space are eliminated, but also the quantities of gas which otherwise escape from the "clean" interior through "gas dynamic locks" into the surrounding space. Therefore, the ambient space can be evacuated with much smaller and cheaper vacuum pump (s). These vacuum pump (s) can have a comparatively smaller pumping speed and must (as well as the other components of the environmental space) meet less stringent cleanliness requirements.

In a further embodiment, the housing in which the at least one optical element is arranged, double-walled, wherein the surrounding space extends at least partially in a space of the double-walled housing. In the case of the double-walled construction of the housing, partial regions of the common surrounding space, which are located in the housing and on which the holder (s) of a respective reflective optical element are arranged within the housing, can be connected to one another via the intermediate space.

Basically, the shell may consist of flexible and stiff sections. The flexible section (s) allow movement manipulation of the reflective optical elements in the housing or optionally at least mechanical decoupling of the reflective optical element (s) from the housing or remainder of the optical assembly. The rigid portions of the sheath may be formed, for example, by portions on the insides of the inner wall of the housing or by rigid portions of the sheath which For example, serve to connect a flexible portion of the shell with the housing or with the inner wall of the housing.

In one embodiment, at least one flexible portion of the shell is formed by a bellows, preferably of a metallic material. The flexible portion in this example is typically formed from a thin sheet of metal or one or more thin metal foils forming a diaphragm bellows or corrugated bellows. A corrugated metal bellows is typically hydraulically formed from a thin-walled tube. A metallic diaphragm bellows, sometimes called diaphragm bellows, is individually welded together in several operations from several corrugated metal rings. In addition, there are also galvanically shaped metal bellows, which are usually relatively small and can be made of nickel, for example. The metallic bellows described here generally have a thickness or a wall thickness between about 0.1 mm and 0.2 mm. The metallic material is preferably stainless steel, aluminum, Inconel ^® (a corrosion-resistant nickel-based alloy) or other metals which the to radiation, in particular EUV radiation and over other influences, for example, hydrogen radicals, which under Influence of EUV radiation generated in the interior are resistant.

In one embodiment, at least one flexible portion of the shell is formed by a flexible plastic component. As flexible plastic components thin plastic components may be used in particular, for example in the form of films, in particular in the form of Kapton ^® film (ie, a polyimide film) or in the form of Teflon ^® (ie polytetrafluoroethylene) film. These have the advantage that they are available at low cost. Flexible plastic components, such as rubber, may also be formed in the form of bellows, which are commonly referred to as bellows. Such bellows can be comparatively thick-walled and, for example, have a wall thickness of about 1 mm or more.

In a development, the plastic component has at least on its side facing the interior a shield or a protective layer. For protection against the above-mentioned influences, a protective layer of Al, Ru, Mo, Pt or the like can be applied to a respective plastic component at least on its side facing the interior or the protective layer can be laminated onto the plastic component. Alternatively or additionally, the plastic component may be provided with a shield e.g. be covered in stainless steel or aluminum. For example, in order to ensure flexibility of the sheath in this case, the shield may have two portions which are attached to different ends of the flexible portion of the sheath and whose free ends overlap each other to form a gap.

In a further development of the embodiment described above, the plastic component is electrically conductive at least on the side facing the interior, or this has an electrically conductive layer. The plastic material of the plastic component may itself be electrically conductive, but it is also possible to laminate on the plastic component (at least) an electrically conductive layer or to provide the plastic part with an electrically conductive coating to avoid electrostatic charging effects. If necessary, the electrically conductive layer can simultaneously form the protective layer.

In a further development, the flexible plastic component has a thickness of 50 μm or less, possibly of 10 μm or less, in particular of 1 μm or less. In particular, if a flexible portion of the envelope is needed, which is arranged in the beam path, e.g. To seal an opening in the housing, the use of a plastic component of small thickness, e.g. in the form of a film or a thin membrane, low.

In a further embodiment, the optical arrangement comprises at least one actuator for moving the reflective optical element in the interior of the housing, wherein the actuator is arranged in the surrounding space. As described above, not only the holder but also an actuator for moving the optical element may be disposed in the surrounding space. The actuator may serve to displace the optical element along a respective displacement path in three directions and to additionally rotate or tilt the optical element about three axes. As a rule, the entire actuator, ie both its passive components and its active components, is arranged in the surrounding space. As an actuator, for example, can serve a Lorentz actuator having active components such as coils and / or movable magnets, which serve to generate magnetic fields, which interact with passive, such as ferromagnetic components, which are usually on the main body of the respective reflective optical Elements are attached or connected to this. A respective holder may, for example, one or more thin-walled components, for example in the form of pots of materials such as stainless steel, aluminum, copper, ceramic, etc., which are so thin that for the movement of the optical Elements used magnetic fields without major losses can pass through them.

The sheath should be attached to the body in a manner that prevents excessive mechanical stress and concomitant deformation of the body of the reflective optical element. There are several possibilities for this:
In one embodiment, the base body of the reflective optical element for fastening the envelope has a circumferential collar. The base body typically has a first side facing the interior space, on which the reflective surface is formed, and a second side facing the surrounding space, to which the holder (s) typically engage. The collar typically runs around a circumferential side surface of the body. The circumferential collar is typically made of the material of the body and the body is generally formed integrally with the collar. The material of the base body may be a so-called zero-expansion material, for example, titanium-doped silica glass or a glass ceramic, for example, Zerodur ^®. The base body can also be made of a different material, for example of conventional quartz glass.

The sheath may have a portion for attachment to the collar which engages over the collar to produce a positive connection, but it is also possible that no portion extending beyond the collar is provided on the sheath, e.g. when gravity presses the underside of the collar against the shell and already in this way a sealing effect between the collar and the shell is achieved. In this case, it may be possible to dispense with an additional fixation of the shell on the collar.

The shell can also be firmly bonded, for example by gluing, to the base body. The resulting in the cohesive connection in the body tensions and deformations can be determined experimentally or by calculation and, if necessary, kept in the production of the body. It is understood that the cohesive connection of the shell with the base body can be made in particular also on the collar of the base body in order to reduce any deformations that may occur.

In a further embodiment, the optical arrangement comprises a spring element for clamping the sleeve to the base body of the reflective optical element. The shell can be clamped to the body, for which purpose preferably a spring element is used. The spring element may be, for example, a snap ring or a spiral spring (tension spring), which preferably surrounds the peripheral surface of the base body in an annular manner, so that it exerts well-defined forces on the base body of the reflective optical element. The deformations generated by the spring force can also be taken into account or kept in the production of the body of the reflective optical element. The spring element may optionally be attached to the main body on the existing there collar, the provision of a collar is not mandatory.

In a further embodiment, the optical arrangement comprises at least one overpressure flap for compensating a pressure difference between the interior space and the surrounding space. The overpressure flap may be formed in the shell itself, for example in a rigid portion of the shell, or it may be integrated into the shell. The overpressure flap is intended to prevent a pressure difference between the surrounding space and the interior from becoming too great. In principle, it is favorable if the pressure in the interior and the pressure in the surrounding space are approximately equal. In this way, it is possible to prevent the reflective optical element (s) from being exposed to large, uncontrolled mechanical forces resulting from such a pressure difference. The unavoidable pressure differences can be reduced or controlled by the above-described elastic portions of the sheath, for example in the form of bellows. It has proven to be advantageous if the pressure flap (s) can be opened in both directions (ie inwards and outwards), ie they open both at a sufficiently large pressure difference at which the pressure in the surrounding space is greater than in the interior as well as vice versa, ie when the Pressure in the interior is greater than the pressure in the ambient space. The greater the overpressure flaps are formed, the smaller is typically the pressure differential which can stress the reflective optical elements and the envelope. The overpressure flaps can be used in particular for the case that they have a comparatively large surface, for transport, pumping, venting, for the service and for accident cases.

The invention also relates to a method for operating an optical arrangement as described above, comprising: irradiating radiation, in particular of EUV radiation, onto the reflective surface of the at least one reflective optical element, and generating a pressure difference between the interior of the housing and the ambient space, wherein a pressure in the inner space is greater than a pressure in the surrounding space. At least during the operation of the optical arrangement, it is favorable if the pressure in the interior space in which the beam path extends is greater than the pressure in the surrounding space, so that contaminants can not escape from the surrounding space into the interior, for example if at Sheath leaks occur.

Preferably, the pressure difference between the pressure in the internal space and the pressure in the ambient space is less than 100 Pa, preferably less than 50 Pa, in particular less than 10 Pa. The pressure in the interior is typically less than about 100 Pa. As described above, it is favorable if the pressure in the interior space is greater than the pressure in the surrounding space. However, the pressure difference should not be too great to keep caused by the pressure difference forces on the shell and on the reflective optical elements at least in the operation of the optical arrangement as small as possible.

In a further variant, a gas is supplied to the interior, which differs from a gas present in the surrounding space, i. the gas supplied to the interior has a different chemical composition than the gas in the surrounding space. The gas-tight seal between the interior with the beam path and the surrounding space with the holders, actuators, circuit boards, cables u.ä. allows the use of different types of gas in the two spaces, i. independently of each other. While the interior with the beam path is preferably purged with high purity hydrogen (to which other high purity gases may be added), the remaining space, i. the ambient space, operated without rinsing or possibly rinsed with cheaper gases. These other gases (air, dry air, nitrogen, forming gas, noble gases, mixtures) need not necessarily be as pure as the gas supplied to the interior. In particular, the materials and components disposed in the environmental space no longer need to be resistant to hydrogen.

Further features and advantages of the invention will become apparent from the following description of embodiments of the invention, with reference to the figures of the drawing, which show details essential to the invention, and from the claims. The individual features can be realized individually for themselves or for several in any combination in a variant of the invention.

drawing

Embodiments are illustrated in the schematic drawing and will be explained in the following description. It shows

1 a schematic representation of an EUV lithography system with a arranged in a lighting system flexible envelope,

2 a schematic representation of a projection system of an EUV lithography system, in which a plurality of envelopes are arranged, which are each attached to the main body of a reflective optical element,

3a a schematic representation of a main body of a reflective optical element with a collar for attachment of a shell,

3b a schematic representation of a detail of a main body of a reflective optical element with an annular coil spring for clamping the shell,

4 a schematic representation of an optical element with a sheath which is attached to a protruding portion of a housing, as well as

5 a schematic representation of an optical element with two holders, which are completely or partially surrounded by a shell.

In the following description of the drawings, identical reference numerals are used for identical or functionally identical components.

In 1 is schematically an EUV lithography system 1 in the form of an EUV lithography system, which is a beam generation system 2 , a lighting system 3 and a projection system 4 which, in separate (vacuum) housings 2a . 3a . 4a housed and consecutively in one of an EUV light source 5 the beam generating system 2 outgoing beam path 6 that of the EUV light source 5 generated EUV radiation 6a are arranged.

As an EUV light source 5 For example, a plasma source or a synchrotron can serve. The from the light source 5 Exiting radiation in the wavelength range between about 5 nm and about 30 nm is first in a collimator 7 bundled. With the help of a subsequent monochromator 8th is filtered out by varying the angle of incidence, as indicated by a double arrow, the desired operating wavelength, which is about 13.5 nm in the present example. The collimator 7 and the monochromator 8th are designed as reflective optical elements.

The in the beam generation system 2 with regard to wavelength and spatial distribution, treated EUV radiation 6a gets into the lighting system 3 introduced, which a first and second reflective optical element 9 . 10 in the form of mirrors. The two reflective optical elements 9 . 10 conduct the EUV radiation 6a on a photomask 11 (Reticle) as another reflective optical element, which has a structure by means of the projection system 4 on a smaller scale on a wafer 12 is shown. These are in the projection system 4 a third and fourth reflecting optical element 13 . 14 provided in the form of EUV mirrors. It is understood that both the number of optical elements in each system 2 . 3 . 4 as well as their arrangement is to be understood only as an example and that in real systems, both the number and the arrangement of the reflective optical elements from the in 1 shown EUV lithography system 1 can distinguish.

The reflective optical elements 8th . 9 . 10 . 11 . 13 . 14 each have a reflective optical surface 8a . 9a . 10a . 11a . 13a . 14a on top of that, the EUV radiation 6a the EUV light source 5 is exposed. The reflective optical elements 8th . 9 . 10 . 11 . 13 . 14 , more precisely their basic body 8b . 9b . 10b . 11b . 13b . 14b comprising or formed from a substrate are one for EUV radiation 6a reflective coating, which is either for incident under normal or grazing incidence EUV radiation 6a is optimized and at the respective reflective surface 8a . 9a . 10a . 11a . 13a . 14a is formed.

To the impact of contaminants on the reflective optical surfaces 8a . 9a . 10a . 11a . 13a . 14a prevent or minimize, the EUV lithography system 1 a case 16 on that in 1 exemplary in the lighting system 3 is shown, but of course also in a housing 17 can extend in which the mask 11 is arranged, as well as from the mask 11 over the housing 4a of the projection system 4 up to another housing 18 in which the wafer 12 is arranged, ie the shell 16 can practically the entire beam path 6 the EUV radiation 6a surround.

At the in 1 example shown is the shell 16 made of flexible plastic components in the form of films and has three flexible, contiguous sections 16a -C on. The first paragraph 16a connects the housing 3a of the lighting system 3 at an opening 3b to the beam generating system 2 with the first reflective optical element 9 , The second section 16b connects the first reflective optical element 9 with the second reflective optical element 10 and the third section 16c connects the second reflective optical element 10 with the housing 3a of the lighting system 3 , at an opening 3c to the passage of the beam path 6 the EUV radiation 6a to the housing 17 in which the mask 11 is arranged.

The case 16 thus separates an interior 19 of the housing 3a of the lighting system 3 in which the beam path 6 the EUV radiation 6a runs and in which the two reflective surfaces 9a . 10a the reflective optical elements 9 . 10 are arranged from an environment space 20 in the case 3a of the lighting system 3 or seals the interior 19 essentially hermetic against the surrounding space 20 from. In the environment room 20 are exemplary two holders 21a . 21b for movable storage of the body 9b of the first optical element 9 as well as two holders 22a . 22b for movable storage of the body 10b of the second optical element 10 of the lighting system 3 shown. The holders 21a . 21b respectively. 22a . 22b support the respective optical element 9 . 10 on the housing 3a of the lighting system 3 and ideally couple them mechanically to the housing in this way 3a that causes vibrations of the case 3a not on the respective optical element 9 . 10 transfer. It is understood that for the movable mounting of a respective optical element 9 . 10 on the housing 3a more or possibly less than two holders 21a . 21b respectively. 22a . 22b can be provided.

In 1 also shown are each very strongly schematically two actuators 24a . 24b for moving or manipulating the movement of the first reflecting optical element 9 as well as two actuators 25a . 25b for moving or manipulating the movement of the second reflective optical element 10 , In the example shown serve the actuators 24a . 24b . 25a . 25b to that, the holders 21a . 21b respectively. 22a . 22b telescopically to change in length, as indicated by a double arrow. At the actuators 24a . 24b . 25a . 25b For example, they may be Lorentz actuators that generate magnetic fields to control the movement of the reflective optical elements 9 . 10 to effect. It is understood that the holder 21a . 21b respectively. 22a . 22b as well as the actuators 24a . 24b . 25a . 25b are shown very schematically and that there are other possibilities for their technical implementation, ie in particular the holder 21a . 21b . 22a . 22b be designed not telescopic.

When choosing the technology and materials for the corresponding components such as the holders 21a . 21b . 22a . 22b or the actuators 24a . 24b . 25a . 25b Affects the environment space 20 with the help of the shell 16 hermetically or substantially hermetically from the interior 19 is sealed so that contaminants that are in the ambient space 20 not in the interior 19 can reach. The cleanliness requirements to the surrounding space 20 are therefore lower than the cleanliness requirements, the interior 19 are to be made.

In the movement of the reflective optical elements 9 . 10 becomes the flexible shell 16 in a respective flexible section 16a -C deformed and possibly elastically stretched or compressed. The flexible shell 16 or the flexible sections 16a -C, from which it is formed, therefore allow a movement manipulation of the optical elements 9 . 10 , This has an advantageous effect that the range of motion of the optical elements 9 . 10 is usually low, ie they can only be moved or tilted over a relatively small distance. The thickness D of the shell 16 or the flexible sections 16a -C the case 16 or the film is typically small and may for example be less than about 150 microns.

The optical elements 9 . 10 in the interior 19 of the housing 3a of the lighting system 3 as well as the optical elements 13 . 14 of the projection system 4 and optionally the optical elements 7 . 8th the beam generating system 2 are operated under vacuum conditions in a residual gas atmosphere, which has a (static) pressure of a few pascals, in the present example of p _I = 10 Pa. To generate such a vacuum atmosphere in the interior 19 indicates the EUV lithography system 1 a vacuum pump 27 on, which has an opening in the shell 16 with the interior 19 communicates. For creating a vacuum atmosphere in the surrounding space 20 indicates the EUV lithography system 1 at the in 1 shown example, a separate vacuum pump 27a on. To generate a controlled residual gas atmosphere in the interior 19 is in the lighting system 3 also a gas supply 28 attached to the interior 19 over another opening in the shell 16 a gas 39a or optionally a gas mixture which may contain, for example, hydrogen and / or helium.

To forces acting on the flexible shell 16 as well as on the optical elements 9 . 10 act to minimize possible, should a pressure difference Ap = p _I - p _U between the (static) pressure p _I in the interior 19 and the (static) pressure p _U in the ambient space 20 not too big. To prevent the ingress of contaminants into the interior 19 even in the case to prevent or at least reduce that in the flexible shell 16 Leaks occur, it is typically useful, at least during operation of the EUV lithography system 1 the pressure p _I in the interior 19 greater than the pressure p _U in the surrounding space 20 , However, the pressure difference Δp should not be too large and, in particular, not more than about 100 Pa, possibly not more than about 50 Pa, in particular not more than about 10 Pa.

As described above, the casing is 16 or the flexible sections 16a -C in the example shown from plastic components in the form of a film, for example ^Kapton® or ^Teflon® formed. To the plastic shell 16 against degrading influences from the interior 19 to protect is the shell 16 at the interior 19 or the beam path 6 facing side of the flexible sections 16a -C each with a protective layer 29 provided, as exemplified in 1 for a small portion of the first flexible section 16a is indicated. The protective layer 29 For example, it may be formed of a material such as Al, Ru, Mo, Pt or the like. The protective layer 29 can be applied to the respective flexible section by a conventional coating method 16a -C the case 16 but it is also possible that the protective layer 29 is laminated. It is understood that a corresponding protective layer also on the surrounding space 20 facing side of the shell 16 can be applied.

Alternatively or in addition to the use of a protective layer 29 can be a respective flexible section 16a -C the case 16 at his the interior 19 facing side also with a shield 30 eg made of stainless steel or aluminum. To prevent the flexibility of the case 19 by the usually rigid shielding 30 Lost, the shield can be lost 30 for example, two subareas 30a . 30b have, at different ends of the flexible portion 16a the shell 16 are attached and whose free ends overlap each other to form a gap, as shown in FIG 1 exemplified for the first flexible section 16a the shell 16 is shown.

In order to prevent electrostatic charging, a respective flexible section 16a -C in the form of a film at least at its the interior 19 facing side at least one electrically conductive layer 29 exhibit. In the example shown, the protective layer 29 formed of an electrically conductive material, so that the protective layer at the same time the electrically conductive layer 29 forms. It is understood, however, that in the event that the protective layer 29 is formed of a non-electrically conductive material, an electrically conductive layer on the protective layer 29 can be applied. To prevent electrostatic charging may alternatively or additionally optionally also a respective flexible section 16a -C the case 16 be formed in the form of a film itself from an electrically conductive plastic.

At the in 1 example shown encloses the shell 16 the beam path 6 the EUV radiation 6a Not only, but this also has two more flexible sections 16d . 16e on, showing the cross section of the beam path 6 the EUV radiation 6a cover. The first of the two other flexible sections 16d is at the opening 3b between the case 2a the beam generating system 2 and the lighting system 3 and the second more flexible section 16e is at the opening 3c between the case 3a of the lighting system 3 and the housing 17 in which the mask 11 is arranged, attached and seals the respective opening 3b . 3c from. As in 1 can be seen, the beam path occurs 6 the EUV radiation 6a through the corresponding at the openings 3b . 3c formed flexible sections 16d . 16e through the shell 16 therethrough.

To the loss of radiation power of EUV radiation 6a when passing through the respective further flexible section 16d . 16e To minimize as possible, have the other flexible sections 16d . 16e , which are also formed in the form of a film or a thin membrane, a very small thickness D of less than 5 microns, possibly even less than 1 micron. The other flexible sections 16d . 16e For example, they may be formed in the manner of a pellicle as they are for the protection of the mask 11 be used. The other flexible sections 16d . 16e For example, Si, Zr, Ru, Rh, Nb, Mo, B, or silicon nitride may be formed, but other materials may be used for this purpose.

2 shows an example of a projection system 4 , also for the EUV lithography system 1 from 1 can be used. The projection system 4 points at the in 2 example shown in contrast to the in 1 shown three reflective optical elements 13 . 14 . 15 on. The three reflective optical elements 13 . 14 . 15 wise as in the 1 each shown a reflective surface 13a . 14a . 15a as well as a basic body 13b . 14b . 15b on, at the two holders 21a . 21b . 22a . 22b . 23a . 23b attack the body 13b . 14b . 15b to hold or relative to the housing 4a movable store. As in 1 is also in 2 each of the holders 21a . 21b . 22a . 22b . 23a . 23b an actuator 24a . 24b . 25a . 25b . 26a . 26b assigned to the respective basic body 13b . 14b . 15b to move, ie to this in the housing 4a to position and tilt suitable (typically in three spatial directions).

Unlike the one in 1 example shown in the in 2 shown example of each of the three reflective optical elements 13 . 14 . 15 a separate shell 16 on that the interior 19 in which the reflective surfaces 13a . 14a . 15a the reflective optical elements 13 . 14 . 15 are arranged, against a respective partial area or a respective partial volume of the surrounding space 20 seal, in each case two holders 21a . 21b . 22a . 22b . 23a . 23b as well as the associated actuators 24a . 24b . 25a . 25b . 26a . 26b are arranged. Each of the three cases 16 has a flexible section 16a as well as a rigid section 16f on. The flexible section 16a is on the body 13b . 14b . 15b a respective reflective optical element 13 . 14 . 15 fastened while the rigid section 16f on the housing 4a is attached. The attachment of the rigid section 16f the shell 16 on the housing 4a can be done for example by welding or otherwise.

Unlike the one in 1 example shown is the shell 16 at the in 2 Example shown formed from a metallic material, for example, aluminum, stainless steel, Inconel ^® or other materials, compared to the conditions in the residual gas atmosphere in the interior 19 , For example, to hydrogen radicals, are largely inert. The flexible section 16a the shell 16 is different from the rigid section 16f the shell 16 essentially in that the metallic material in the flexible section 16a has a smaller thickness and is designed in the manner of a metallic bellows, typically a corrugated bellows or a diaphragm bellows, to manipulate the movement of the respective optical element 13 . 14 . 15 to enable. At the in 2 The example shown is the flexible section 16a tubular around the respective central axis 31 a respective reflective optical element 13 . 14 . 15 arranged, with the cross section of the flexible section 16a essentially the cross section of the respective optical element 13 . 14 . 15 or the cross section through or around its respective holder 21a . 21b . 22a . 22b . 23a . 23b is similar or adapted to this cross-section. This arrangement typically minimizes the mechanical effects of the envelope 16 on the reflective optical elements 13 . 14 . 15 as well as their positioning. It is understood that even in the 2 shown a respective flexible section 16a the shell 16 instead of a typical metallic bellows may be formed by a flexible plastic component in the nature of a film or a (bellows) bellows. Also the rigid section 16f the shell 16 may be formed of a plastic material having a has higher rigidity than the flexible section 16a , The higher stiffness can be produced by a greater thickness and / or by a different composition of the plastic (plastic in place of rubber, glass fiber reinforced, ...).

At the in 2 the example shown are the partial volumes of the ambient space 20 in a respective case 16 one of the three optical elements 13 . 14 . 15 are formed, interconnected, through a gap 32 in the double-walled housing 4a between an outer housing wall 33a and an inner housing wall 33b is formed. The gap 32 and thus the surrounding space 20 stands with its own vacuum pump 27a in connection. The use of different vacuum pumps 27 . 27a is convenient to in the interior 19 To create a higher cleanliness of the vacuum than in the environmental space 20 the case is where the cleanliness requirements for the vacuum are lower, so there in addition to the holders 21a . 21b . 22a . 22b . 23a . 23b and the actuators 24a . 24b . 25a . 25b . 26a . 26b It is also possible to arrange further components which may possibly be a source of particles and outgassing and which, for example, in the form of cables, circuit boards, a media supply for controlling the temperature of the reflecting optical elements 13 . 14 . 15 etc. may be formed. The interior 19 gets through the covers 16 as well as through the inside of the inner housing wall 33b of the housing 4a limited. The corresponding sections of the inner housing wall 33b which the covers 16 connect together, may also be considered as rigid sections of a common shell, as in 1 the beam path 6 completely surrounds.

At the in 2 example shown is on the inner housing wall 33b of the housing an overpressure flap 34 formed, facing both towards the interior 19 as well as towards the gap 32 opens as soon as the pressure difference Δp = p _I - p _U between the pressure p _I in the interior 19 and the pressure p _U in the ambient space 20 exceeds a predetermined amount or a threshold, which may for example be about ± 100 Pa. Through the overpressure flap 34 can an excessive pressure difference | Δp | = p _I - p _{U are} compensated, which, for example, during transport of the EUV lithography system 1 , during pumping, ventilation, maintenance and in the event of an accident, ie a leak, is favorable to the reflective optical elements 13 . 14 . 15 as well as the covers 16 not to burden.

As in 1 will also be in 2 the interior 19 via a gas supply 28 a gas 39a fed, which typically contains hydrogen. In the environment room 20 there is a gas on the other hand 39b that is different from the one in the interior 19 supplied gas 39a different. The gastight demarcation between the interior 19 with the beam path 6 and the surrounding space 20 allows the use of different types of gas 39a . 39b , The ambient space 20 can be like in 2 is shown to be operated without rinsing or possibly rinsed with inexpensive gases. In the in the environmental space 20 The gases present may be, for example, air, dry air, nitrogen, forming gas, noble gases, mixtures, etc., which in particular do not necessarily have to be as pure as that of the interior 19 via the gas supply 28 supplied gas 39a ,

For fixing the flexible section 16a the shell 16 at the respective base body 13b . 14b . 15b a reflective optical element 13 . 14 . 15 There are different possibilities, of which 3a , b shown first reflective optical element 13 of the projection system 4 two options are described in more detail.

As in 3a can be seen, the body indicates 13b of the reflective optical element 13 a circumferential collar 35 on, on a circumferential side surface of the main body 13b is formed between a first page 36a of the basic body 13b at the reflective surface 13a is formed, and a second page 36b of the basic body 13b runs, which is the ambient space 20 is facing. At the second page 36b of the basic body 13b grab the in 3a not pictured holder 24a . 24b at.

The collar 35 is made of the same material as the main body 13b formed, which is in the example shown, a so-called zero-expansion material in the form of a titanium-doped quartz glass. In the example shown is the main body 13b with the collar 35 formed in one piece and forms a flange. The collar 35 runs on the circumferential side surface between the two opposite sides 36a . 36b of the basic body 13b of the reflective optical element 13 , It is understood that the collar 35 also in other ways, eg at the holders 21a . 21b facing side 36b of the basic body 13b , can be trained.

As in 3a can be seen, lies the shell 16 with one end of the flexible section 16a on the collar 35 and is fixed to this or attached or sealed. For attachment, the shell 16 on the collar 35 but it is also possible, the envelope 16 or the end of the flexible section 16a in another way cohesively or possibly positively to the collar 35 to fix. The gluing in the body 13b introduced stresses and deformations affect the shape or the geometry of the reflective surface 13a of the reflective optical element 13 and therefore can reduce its optical performance. To prevent this, the stresses or deformations that are caused by the bond can be determined in advance and in the manufacture of the body 13b be kept.

3b shows an example of the attachment of the shell 16 on the body 13b in which this on the main body 13b is clamped. The clamping can be done in different ways, for example by a coil spring 37 (Tension spring) is used, which is a ring around the circumferential side surface of the body 13b of the reflective optical element 13 forms and well-defined forces on the body 13b exercises, in the manner described above in the production of the body 13b can be compensated. In place of a coil spring 37 Also, a spring element in the form of a snap ring or the like can be used to the shell 16 on the body 13b clamp or seal. It is understood that the clamping of the shell 16 on the collar 35 from 3a can be done. Alternatively, of course, the clamping on a base body 13b done, no collar 35 having. In both cases it is favorable if the main body 13b a circumferential notch 38 has, in which the spring element, for example in the form of the coil spring 37 , can intervene, like this in 3b is shown.

In the 2 shown cases 16 are arranged so that they are in the interior 19 of the housing 4a with the beam path 6 penetrate into it, so that of a respective shell 16 surrounded, internal partial volume with the atmosphere or with the gas of the surrounding space 20 is filled. 4 shows an optical element 13 , which is in the case of the shell 16 ring-shaped partial volume of the interior 19 is located while the ambient space 20 outside the annular envelope 16 more precisely outside a flexible section 16a the shell 16 , extends. As in 4 is shown in this case, typically the housing 4a one in the interior 19 protruding section on the shell 16 surrounds or surrounds annularly. The flexible section 16a the shell 16 is at its upper end with the protruding portion of the housing 4a and at its lower end with the on the body 13b of the optical element 13 formed collar 35 connected to the in 4 shown example along the second page 36b of the basic body 13b runs.

5 shows a further possibility for mounting an optical element 13 which is attached to two holders 21a . 21b is held, with each of the two holders 21a . 21b from its own shell 16 is surrounded. The first of the two holders 21a is complete (annular) from the shell 16 More specifically, a flexible section 16a the shell 16 , surrounds and is at the back of the main body 13b of the optical element 13 attached, and typically on a non-illustrated collar (see above). The second holder 21b however, is only in one section of the annular envelope 16 surrounded, up to one on the holder 21b formed collar 40 ranges, on which a flexible section 16a the shell 16 is attached. A partial area or section of the second holder 21b that is between the collar 40 and the body 13b of the optical element 13 is thus in the interior 19 angeordenet. As in 5 can also be seen, is the actuator 24b of the second holder 21b in the surrounding space 20 arranged so that for the choice of a suitable actuator 24b the same degrees of freedom exist as described above. The collar 40 or the attachment of the flexible section 16a the shell 16 takes place in this example typically in a rigid on the body 13b of the optical element 13 attached section of the second holder 21b that with the optical element 13 is moved.

In summary, by using the shell 16 that have at least one flexible section 16a . 16a -E has the requirements for the cleanliness of the vacuum in the surrounding space 20 against the requirements for the cleanliness of the vacuum in the interior 19 be lowered significantly, leaving in the surrounding space 20 The use of materials and components is possible, which could not be used because of the high cleanliness requirements there so far. It is understood that the shell described above 16 not only in the EUV lithography system described above 1 but can also be used advantageously in other optical arrangements in which high cleanliness requirements exist.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2012/0086925 A1 [0004]
• US 8585224 B2 [0005]
• DE 102009029282 A1 [0006]
• US 7829248 B2 [0022]
• US 2010/0195076 A1 [0023]

Claims (20)

Optical arrangement ( 1 ), in particular for EUV lithography, comprising: at least one housing ( 3a . 4a ), in which at least one reflective optical element ( 9 . 10 ; 13 . 14 . 15 ) is arranged, which a basic body ( 9b . 10b ; 13b . 14b . 15b ), on which a reflective surface ( 9a . 10a ; 13a . 14a . 15a ) is formed, at least one holder ( 21a . 21b ; 22a . 22b ; 23a . 23b ), on which the main body ( 9b . 10b ; 13b . 14b . 15b ) of the reflective optical element ( 9 . 10 ; 13 . 14 . 15 ) is preferably movably mounted, characterized by at least one shell ( 16 ), which at least the at least one holder ( 21a . 21b . 22a . 22b . 23a . 23b ) and prefers the basic body ( 9b . 10b ; 13b . 14b . 15b ) of the reflective optical element ( 9 . 10 ; 13 to 15 ) at least partially enveloped and the an ambient space ( 20 ), in which at least one of the shell ( 16 ) wrapped portion of the at least one holder ( 21b ), in particular the entire holder ( 21a . 21b . 22a . 22b . 23a . 23b ), is arranged against an interior ( 19 ) of the housing ( 3a . 4a ), in which the reflective surface ( 9a . 10a ; 13a . 14a . 15a ) of the reflective optical element ( 9 . 10 ; 13 . 14 . 15 ), the envelope ( 16 ) at least one flexible section ( 16a c; 16a ) for enabling motion manipulation of the optical element ( 9 . 10 ; 13 to 15 ) having. An optical arrangement according to claim 1, wherein the envelope ( 16 ), in which the holder ( 21a . 21b . 22a . 22b . 23a . 23b ), the main body ( 13b . 14b . 15b ) of the reflective optical element ( 13 . 14 . 15 ) with the housing ( 4a ) connects. Optical arrangement according to Claim 1 or 2, in which the envelope ( 16 ) during operation of the optical arrangement ( 1 ) in the interior ( 19 ) of the housing ( 3a ) formed beam path ( 6 ), in which the at least one reflective surface ( 9a . 10a ) is completely enveloped and against the ambient space ( 20 ) seals. Optical arrangement according to Claim 3, in which the envelope ( 16 ), which the beam path ( 6 ), from flexible sections ( 16a -C) exists. Optical arrangement according to one of the preceding claims, wherein the interior ( 19 ) of the housing ( 3a . 4a ) with at least one vacuum pump ( 27 ) and gas-tight from the ambient space ( 20 ) is disconnected. Optical arrangement according to one of the preceding claims, in which the housing ( 3a ) at least one opening ( 3b . 3c ) for the passage of the beam path ( 6 ), and wherein the at least one opening ( 3b . 3c ) by another flexible section ( 16d . 16e ) of the envelope ( 16 ) is sealed. Optical arrangement according to one of the preceding claims, in which the holders ( 21a . 21b . 22a . 22b . 23a . 23b ) of a plurality of reflective optical elements ( 9 . 10 . 13 . 14 . 15 ) in a common environment space ( 20 ) are arranged. Optical arrangement according to one of the preceding claims, in which the housing ( 4a ), in which the at least one optical element ( 13 to 15 ) is arranged double-walled, wherein the surrounding space ( 20 ) at least partially in a space ( 32 ) of the double-walled housing ( 4a ). Optical arrangement according to one of the preceding claims, in which at least one flexible section of the envelope ( 16 ) by a bellows ( 16a ), preferably of a metallic material. Optical arrangement according to one of the preceding claims, in which at least one flexible section of the envelope ( 16 ) by a flexible plastic component ( 16a -E) is formed. An optical arrangement according to claim 10, wherein the flexible plastic component ( 16a -E) at least at its interior ( 19 ) facing side a shield ( 30 ) or a protective layer ( 29 ) having. Optical arrangement according to claim 10 or 11, in which the flexible plastic component ( 16a -E) at least on the interior ( 19 ) side facing electrically conductive or at least one electrically conductive layer ( 29 ) having. Optical arrangement according to one of claims 10 to 12, in which the flexible plastic component ( 16a -E) has a thickness (D) of less than 50 has μm. Optical arrangement according to one of the preceding claims, further comprising: at least one actuator ( 24a . 24b . 25a . 25b . 26a . 26b ) for moving the reflective optical element ( 9 . 10 ; 13 . 14 . 15 ) in the interior ( 19 ) of the housing ( 3a . 4a ), wherein the actuator ( 24a . 24b . 25a . 25b . 26a . 26b ) in the ambient space ( 20 ) is arranged. Optical arrangement according to one of the preceding claims, in which the basic body ( 13b ) of the reflective optical element ( 13 ) for fastening the envelope ( 16 ) a circumferential collar ( 35 ) having. Optical arrangement according to one of the preceding claims, further comprising: a spring element ( 36 ) for the clamping attachment of the shell ( 16 ) on the base body ( 13b ) of the reflective optical element ( 13 ). Optical arrangement according to one of the preceding claims, further comprising: at least one overpressure flap ( 34 ) for equalizing a pressure difference (Δp) between the interior ( 19 ) and the surrounding space ( 20 ). Method for operating an optical arrangement ( 1 ) according to one of the preceding claims, comprising: irradiation of radiation, in particular of EUV radiation ( 6a ), on the reflective surface ( 9a . 10a ; 13a . 14a . 15a ) of the at least one reflective optical element ( 9 . 10 ; 13 . 14 . 15 ), as well as generating a pressure difference (Δp) between the interior ( 19 ) of the housing ( 3a . 4a ) and the surrounding space ( 20 ), in which a pressure (p _I ) in the interior ( 19 ) is greater than a pressure (p _U ) in the ambient space ( 20 ). Method according to Claim 18, in which the pressure difference (Δp) between the pressure (p _I ) in the interior space ( 19 ) and the pressure (p _U ) in the ambient space ( 20 ) is less than 100 Pa. A method according to claim 18 or 19, wherein in the interior ( 19 ) a gas ( 39a ), which differs from one in the surrounding space ( 20 ) gas ( 39b ) is different.

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