WO2007144125A2

WO2007144125A2 - Imaging device

Info

Publication number: WO2007144125A2
Application number: PCT/EP2007/005127
Authority: WO
Inventors: Karl-Heinz Schuster
Original assignee: Carl-Zeiss Smt Ag
Priority date: 2006-06-13
Filing date: 2007-06-11
Publication date: 2007-12-21
Also published as: WO2007144125A3; DE102006027609A1

Abstract

The invention relates to a lens system or a lens mirror system, in particular a projection objective, for imaging a pattern, in particular an object structure, that is arranged on an object plane of a lens system or the lens mirror system on an image plane of the projection objective with the aid of an immersion medium (2), that is arranged between an optical element (1) of the lens system or the lens mirror system and the image plane. A protective plate (13, 17) is arranged between the lens system and the immersion medium (2) and at least one means is arranged laterally on the element (1) and/or subsequently on the protective plate (3, 17) such that the sub pressure of the immersion medium (2) is much less on the external contour of the element (1), between the element (1) and the protective plate (3, 17) than on the immersion fluid itself. Suitable means are, for example, a seal, an intermediate immersion fluid, a surrounding lateral wall, supply and discharge lines for the exchange of the medium between the element (1) and the protective plate (3) or receiving means for adsorbing or absorbing an immersion agent (2).

Description

imaging device

The invention relates to a lens system or a lens mirror system, in particular a projection lens, for imaging a pattern, in particular an object structure, arranged in an object plane of the lens system or the lens mirror system, in particular the projection lens, into an image plane of the projection lens with the aid of a Immersion medium, which is arranged between an optical element of the lens system or the Linens mirror system and the image plane, wherein between the lens system or the lens mirror system and the immersion medium, a protective plate is arranged.

Photolithographic projection objectives are lens systems or lens mirror systems used to fabricate semiconductor devices and other finely-structured devices. They serve to project patterns of photomasks, or reticles, also called reticles, ie, object structures, onto a photosensitive layer-coated article of the highest resolution on a smaller scale. Increasing the numerical aperture contributes significantly to producing ever finer structures on the order of 50 nm or less. In addition to increasing the numerical aperture of the projection lens itself, immersion media, in particular immersion liquids, are also used for this purpose. The achievable resolution is thereby improved by the use of a medium having a high refractive index; the technique is called immersion lithography. Their advantage lies in the reduction of the effective working wavelength. At an unchanged light frequency, this makes it possible to reduce the effective wavelength in the medium, using established techniques for light generation, the choice of optical materials, the coating technique, etc. can be taken over unchanged. The use of immersion media is also the prerequisite for the use of projection lenses with highest numerical apertures in the range of 1 and in particular above.

At a wavelength of, for example, 193 nm used for the exposure, ultrapure water with a refractive index of n * 1.437 is characterized as a suitable immersion liquid. In the article "Immersion Lithography at 157 nm" by M. Switkes and M. Rothschild, J. Vac., Sei., Technol. B 19 (6), Nov. / Dec. 2001, pages 1 et seq., Immersion liquids are based on Polyfluoropolyethers (PFPE), which are sufficiently transparent at this operating wavelength and are compatible with some photoresist materials currently used in microlithography, for example, a tested immersion liquid has a refractive index of 1.37 at 157 nm.

Refractive projection lenses for microlithography are known from WO 03/077036 and WO 03/077037, which are suitable for immersion lithography because of their high image-side aperture. US Pat. Nos. 4,480,910 and 5,610,683 describe projection exposure systems provided for immersion lithography with devices for introducing immersion fluid between the projection objective and the substrate.

The use of ultrapure water poses problems due to the high aggressiveness of the water, which attacks crystal materials such as calcium fluoride, strontium fluoride, barium fluoride or lithium fluoride and renders them unusable in contact with the surface within a short time. The surface of optical components made of such a material must therefore be protected. This is done either by applying a ner thin layer or by wringing another plate as a protective plate or alternatively by a Zwischenimmersion between the device and the protective plate, wherein the Zwischenimmersion must not attack the material of the optical component. As a thin protective layer, a layer of quartz, α-sapphire or an extremely thin diamond layer is suitable. As a protective plate is a sprinkled plate made of quartz glass. These materials are sufficiently resistant to ultrapure water.

However, the problem of the strongly differing coefficients of expansion k of quartz glass (k = 0.54 ^· 10 ^-6 K ^-1 ) and calcium fluoride (when using a fused quartz glass plate and a crystal material forming a plano-convex lens as an optical component) k = 18.9 ^• 10 ^" 6K ^{" 1} ). This leads to geometric differences in length of 20 microns in the radial direction at a diameter of 50 mm and a temperature difference of more than 40 ° C, as for example when transported in a cargo hold of an aircraft (temperature of about - 20 ° C) and a Assembly or laboratory temperature of about 22 ° C occurs.

Conventional rigid seals in the connection area of the protective plate to the optical element, such as those resulting from soldering, ultrasonic welding, vapor deposition, etc., must fail here, since the geometric displacements lead to the failure of the rigid seals.

It is the object of the invention to remedy this situation and to provide an effective seal.

According to the invention, this object is achieved by a lens system or a lens mirror system of the type mentioned at the outset. solves that on the side of the element and / or subsequently to the protective plate at least one means is arranged, which causes the partial pressure of the immersion medium at the outer contour of the element, in particular between the element and the protective plate, is much lower than above the immersion liquid even.

The invention is based on the provision of a combined seal using a flexible seal while simultaneously providing a drying space within the component.

Advantageous developments of the invention will become apparent from the dependent claims, the description and the drawings.

In a development of the invention, it is advantageously provided that the means comprises a particularly flexible sealing means. For this purpose, a plurality of sealing bodies is suitable, which either have an elastic shape, for example in the form of a rubber ring, or are deformable as a plastic mass.

It is advantageous embodiment of the invention, according to the at least one channel for discharging the immersion medium from the area between the element and the protective plate is present. Since a seal, in particular a flexible seal, can never be completely sealed off against penetration of the immersion medium as a result of diffusion, in particular of interfacial diffusion, it is favorable to re-immerse the immersion medium which has penetrated into the region adjoining the optical element via a channel to remove, in particular continuously. The interfacial diffusion occurs at the interface between a flexible, laterally adjacent to the lens sealant and the lens itself or at the interface between a Lens protecting protective plate and the sealant on.

Preferably, a particular annular channel, in particular in the region of the outer contour of the protective plate and / or the element, for collecting particles of the immersion medium is further arranged between the element and the protective plate. This channel communicates with the channel for discharging the immersion medium.

Advantageously, the annular channel is at least partially formed by an introduced into the protective plate and / or in the element from the outside annular groove.

Advantageously, a lens system or a lens mirror system according to which a ring channel with a first conduit for supplying an inert medium and a second conduit for discharging the particles of the immersion medium is in communication. This makes it possible to achieve a continuous removal of diffused immersion medium from the vicinity of the optical component.

In one embodiment of the lens system or the lens mirror system, it is provided that the lines run at least partially through the interior of the element, in particular through its optically unused edge area. In particular, in a rectangular image format, for example, a format of 8 mm x 26 mm, this unused area can be very large, so that there is enough space to introduce lines or channels for ventilation in the edge area, without the lines or channels fall into the light-radiated area. Accordingly, not only an annular channel as described above may be present between the lens and the protective plate, but also a rectangular channel, for example, lying outside the light-irradiated area. In front- Preferably, the channel forms a self-contained structure to form a contiguous area which serves to vent the area between the lens and the protective plate. However, there may also be a plurality of mutually independent regions, for example channel-shaped interspaces, of recesses between the lens and the protective plate, each serving for venting and discharging an immersion medium which has penetrated into this space.

In an advantageous embodiment, a seal is used between the element and the protective plate, in particular adjacent to the annular channel.

It proves to be particularly advantageous if the seal is formed as a continuous ring seal of a solid elastic material, in particular as a butyl, silicone or acrylic seal. Alternatively, however, it is also possible to use another sealing compound. If the protective plate is very thin, for example, has a thickness of less than 50 microns, it follows despite different thermal expansion of the stiffness-determining element, ie the crystalline lens; the seal can then be stiff.

In one embodiment, the seal can be inserted between two at least substantially coplanar surfaces, which are formed on the one hand by the element and on the other hand by the protective plate. Alternatively, for example, it can be provided that the seal is arranged between two surfaces of the element and the protective plate that are essentially at an acute or a right angle.

It is advantageous if in the channel and / or in an additional, introduced between the element and the protective plate Chamber a receiving means is present as a carrier for receiving the immersion agent by a chemical reaction or due to adsorption or absorption.

Likewise, a lens system or a lens mirror system is advantageous in which the receiving means an indicator, in particular a color indicator, is attached, indicating the consumption of the receiving means due to the reaction, the adsorption or the absorption. Silica gel with cobalt chloride as a color indicator is suitable for this purpose. When the drying property of the silica gel is exhausted, the cobalt chloride changes color from blue to pink. It is significant that the desiccant remains chemically inert even after ingestion of water. It is understood that other materials than silica gel can be used.

It is advantageous to have a lens system or a lens mirror system in which the receiving means is introduced into a carrier which is adapted in particular to the shape of the channel and / or the chamber, in particular a cylindrical carrier, or into a plurality of, in particular cylinder-segment-shaped carriers.

Likewise, it is also conceivable that the carrier has a pore structure, wherein the receiving means is embedded in the pore structure. Such a pore structure can be realized for example by the use of foam glass or metal foam.

In another embodiment of the lens system or of the lens mirror system, a band impregnated with a receiving agent, in particular highly dried, or a band impregnated with the receiving means, in particular highly dried, cord is introduced into the annular groove as a carrier; Here is the tape or the Cord with advantage several times wound around the annular groove until it or they preferably completely fills the annular groove.

In a further embodiment of the lens system or the lens mirror system is provided that the element in the region of the arrangement of the means which cause the partial pressure of the immersion medium between the element and the protective plate is much lower than between the protective plate and the Pattern, in particular an object structure, in particular in the region of the channel or another contour for receiving a seal, a Schutzbedampfung is applied, which protects the element against water and / or UV radiation. The UV protection is provided in particular only in the edge area; As a result, the sealing material is at least largely protected against UV radiation. In this case, on an adjacent lens surface, but also on the protective plate, a UV protective layer may be applied, which consists in the case of a transmitted wavelength of 193 nm, for example zirconia (ZrO ₂ ).

In addition or as an alternative to the measures described above, a lens system or a lens mirror system can be designed so that the laterally arranged means consists of a rigid material, in particular of the same material or a similar material as the element, in particular of calcium fluoride, strontium fluoride, barium fluoride or lithium fluorine - Orid, or made of silica or glass, in particular quartz glass, is formed, wherein the protective plate and the means consist of the same material.

When using materials for the body forming the protective plate must be taken into account that in addition to the chemical resistance and the thermal expansion coefficient is of great importance. Here two cases have to be distinguished: the: a thin protective plate whose thickness is approximately between 5 microns and 100 microns, and a thick protective plate whose thickness is greater than about 100 microns and which may be up to about 10 mm thick.

The thermal expansion coefficient of the existing example of calcium fluoride (CaF ₂ ) lens material is predetermined by the choice of the optical material. As already known, the protective plate can consist of quartz glass, which, however, has an extremely small thermal expansion compared to calcium fluoride. However, boron nitride, which has a hexagonal crystal structure and whose optical axis is aligned parallel to the optical axis of the lens system, is also suitable as a further material for use at a wavelength of 248 nm. Boron nitride has a thermal expansion coefficient of 3.5 ^• 10 ^'6 K ^-1 .

Alternatively, sapphire (Al ₂ O ₃ ), whose crystallographic main axis must also be aligned parallel to the optical axis. Its thermal expansion perpendicular to the optical axis, ie adjacent to a, for example, made of calcium fluoride lens is 7.15 ^• 10 ^"6 K ^{" 1} .

Another suitable material is beryllium oxide (BeO), which also has a hexagonal crystal structure and whose thermal expansion is 5.64 ^· 10 ^-6 K ^-1 perpendicular to the direction of the optical axis.

Another material that can be used for the formation of the protective plate with light of the wavelength 248 nm is diamant. Its thermal expansion is 1.25 ^• 10 ^-6 K ^'1. Also suitable is magnesia spinel which has a thermal expansion of 6.97 ^• 10 ^{"has 6} ^{K' 1.} Also Scandiumaluminiumgranat (SC ₃ AI ₅ O 12) having a thermal expansion of 7,7 ^• 10 ^{~ 6} K ^'1 is suitable. In addition, other materials can be used, using both cubic-isotropic and uniaxial-anisotropic materials. The use of optically uniaxial materials, however, is based on the use of perpendicular or parallel polarized light, flat surfaces and low image-side telecentricity error of the projection system.

If birefringent materials are used, the plate thicknesses must be chosen so thin that the birefringence does not disturb the image structure.

When quartz glass or any of the materials listed above are blasted onto the last lens in the beam path, the thickness of the blasted guard plate must not exceed a thickness in the range between 5 μm and 100 μm to prevent sliding movement between the lens and the guard plate comes. A means attached to the side of the protective plate then preferably has an expansion coefficient which is adapted to that of the lens. Thus, in the case of calcium fluoride, it is preferably 18.9 ^· 10 ^-6 K ^-1 . Thus, the laterally mounted means is in turn made of calcium fluoride or of a metal or metal alloy which has the same or a similar thermal expansion, for example brass, which has a thermal expansion coefficient of 18 × 10 ^-6 K ^-1 To protect brass sufficiently against corrosion, it is preferably nickel-plated.

However, if the protective plate has a thickness that is considerably greater than 100 microns, for example, 0.5 mm to 10 mm, the inherent rigidity of the protective plate outweighs. In this case, it is not necessary to use a blower if a temperature range of a few degrees is exceeded. The Ansprengkräfte are no longer sufficient for such thicknesses of the protective plate, and it comes to shearing, which sometimes lead to permanent tension in the lens element.

Therefore, according to the invention, a connection between the protective plate to the last lens is provided such that the protective plate can slide without force relative to the lens. This can be achieved by using an immersion liquid, for example, having a thickness of less than 50 microns. It is also possible to use a thin film, for example an oil film. Alternatively, it is also possible to realize thin layers of a sufficiently elastic solid material, for example of Teflon (tetrafluoroethylene). However, these layers can only be a few nanometers thick.

If the protective plate has a thickness in the range between 0.5 and 10 mm, the coefficient of thermal expansion of the laterally applied means must be selected after that of the protective plate.

When the protective plate made of silicon dioxide having an expansion coefficient of 5.4 • 10 ^-6 K ^"1, is used as side-mounted means also preferably silicon dioxide is einge-. Alternatively, an iron-nickel alloy may, for example Invar or Superlnvar be used which has a thermal expansion coefficient of 1.0 ^• 10 ^-6 K ^-1 . For reasons of corrosion protection, the means consisting of an iron-nickel alloy must be nickel-plated.

If the protective plate is made of magnesium spinel, which has a coefficient of expansion of 6,97 · 10 ^-6 K ^-1 , a glass of bulkhead, for example Schott UBK 7, Schott K 50, Schott UK 50 or Schott BAK 4. These glasses each have a coefficient of expansion of 7.0 • 10 ^"6 K ^{" 1} . Alternatively comes in the case of the laterally mounted means in this case, a metal or a metal alloy into consideration.

By means of such a construction, a trough-shaped sheathing of the component to be protected against the immersion medium is created, which protects it, even if it is partly immersed in the immersion medium.

In this case, it is advantageous if the element in the area of the laterally arranged means at least partially has a conical periphery tapering in the direction of the side of the element covered by the protective plate, the means laterally covering the element itself likewise being at least partially cone-shaped ,

The laterally arranged means is preferably connected to the protective plate on the underside of the element to form a trough-shaped body.

In an advantageous embodiment, the laterally arranged means is glued to the protective plate or connected by a metal or a metal oxide, by welding or soldering to the protective plate or sprinkled on this.

In a further development of the lens system, the laterally arranged means is additionally bonded to the protective plate at an obtuse angle facing an inner side of the trough-shaped body, in particular by an inorganic adhesive.

According to the invention, it can be provided that the lens system has see the element and the laterally disposed means at a distance.

In another development, the agent in the region of the distance is covered with a serving as UV radiation protection coating. In addition, a vapor deposition can also be applied in the area between the protective plate and the underside of the lens.

As an additional measure for protecting the optical element can be provided that the means and the protective plate in the connection region on the outside of a Schutzbedampfung, in particular of silicon dioxide.

The means attached to the side of the optical element may in places have at least one recess in its inner and / or outer wall. A recess mounted on the inside has a joint function and increases the elasticity of the agent. The wall of the agent can be on the inside of several times over each other (viewed in the propagation direction of the light) provided with recesses. Also on the outer contour of the agent can recesses or depressions produce, for example, by milling. As a result, the rigidity decreases in the lower region, in order to allow an expansion or compression of the agent in the circumferential direction. On the other hand, the means, which has the shape of a ring remains stiff in its upper, facing away from the protective plate area, since this must be neither compressed nor stretched. Due to the remaining ribbing, the agent retains sufficient stability and rigidity.

An advantage of the invention is also that with the immersion medium only highly pure, non-degassing surfaces in In addition, a silicon dioxide-containing seal at the connection point between the protective plate and the side panel can be used in addition, as formed for example by a protective plate made of silica and a likewise made of silica lateral boundary.

In an optical component connected according to the invention with a protective plate, only temperature differences which are absorbed by the elastic structure of the arrangement can occur. The cavities present between the protective plate and the lateral protective means are always accessible to a gas flow introduced from the outside. Since the water level is always below the upper edge of the conical protective part, it is merely constructive to provide a simple splash guard from above for the space between the component, for example the calcium fluoride-based lens, and the laterally mounted means.

The invention also relates to a method for applying the protective plate and the agent to a cone-shaped peripheral element of a lens system, in particular a projection lens.

According to the invention, the method is characterized in that the element is held with its side to be covered by the protective plate upwards in a holder, that subsequently a laterally mounting a portion of a hollow cone forming means is placed over the circumference of the element until it is below the level the side to be covered by the protective plate has dropped, and that subsequently the protective plate is placed on the area to be covered by it, in particular it is blown up. This method is further developed in that the element together with the protective plate and the means to be attached laterally with each other are rotated together so that the protective plate is at least substantially below the element and that thereon the protective plate and the means are connected to a trough-shaped body. The agent is preferably sprinkled or glued to the protective plate or the protective body; however, it can also be linked to it in other ways.

A further method measure is that the means and / or the protective plate is sealed on the side facing away from the element, in particular in the transition region from the means to the protective plate, as by the vapor deposition or deposition of an oxide compound, in particular a quartz protective layer ,

An additional method step may be that the agent is provided on the outside at least partially with recesses, in particular by Abfrasen. In this case, for example, a rib structure can be generated.

An additional measure is advantageously that the protective plate and the means are glued together in the region of the obtuse angle formed between them.

The invention also relates to the use of a lens system or a lens mirror system in which in at least one optical element, the removal of particles of the immersion agent from a region between the protective plate and the element or from a region between the protective plate, the means and the element is provided. According to the invention, it is provided that an inert gas, in particular nitrogen or a noble gas, is conducted via a first line to the area in which the particles entrain and lead away from the area via a second line.

The invention avoids degradation of the optical component, in particular of a lens, by bringing a protective plate in front of the optical component, which protects it against the immersion medium, in particular the immersion liquid such as ultrapure water. Thus, an extension of the life of the lens within the projection lens and thus the entire optical system is achieved. As a rule, only the last element in the light path comes into contact with an immersion medium; However, the invention can also be used with advantage if it is the first element in the light path or an optical element arranged within the projection objective.

In general terms, an optical element with at least two optically active surfaces, at least one, at least one optical surface covering and at this, at least partially, applied to a contact surface protective body.

According to the invention, the optical element is characterized in that a gap is formed between the optical element and the protective body outside the contact surface.

In a further embodiment, the protective body is sprinkled in the region of the contact surface against the optical element; and a thin protective plate with a thickness in the range between 5 μm and 100 μm is applied both to the last optical element, ie in the direction of the immersion liquid, and to the protective body. blown up. This means that the protective body surrounds the optical element at its outer contour, so that this and the protective body form adjacent boundary surfaces, both of which are covered by the protective plate.

The gap is alternatively either open or closed. The gap is advantageously formed by a recess in the optical element and / or the protective body.

Preferably, the gap is closed by an adhesive and / or a sealant. Advantageously, it is provided that the intermediate space has an inlet and outlet for a fluid.

The invention also relates to the use of a partial pressure-reducing material used in the intermediate space, which reduces the partial pressure with respect to a substance, in particular with respect to an immersion medium. The material reduces the partial pressure, for example, by a chemical reaction or by adsorption of the immersion medium.

Advantageously, it is also provided that the optical element is a thick plano-convex or plano-concave lens, wherein the protective body covers at least the planar optical effective surface. The lens preferably contains calcium fluoride or a fluoride-containing material.

A protective body, which comprises a plane-parallel or at least almost plane-parallel plate in the region of the contact surface, proves to be advantageous.

Advantageously, the protective body comprises at least one edge element for at least partial overlapping of the optically non-effective edge surface of the lens.

Advantageously, the intermediate space is formed in the region of the plane-parallel plane-parallel or at least approximately plane-parallel plate and / or the edge element.

In addition, it can be provided that the gap annularly surrounds the contact surface with the plane-parallel plate in the vicinity of the edge or at the edge of the optical element.

Likewise, it is advantageous if the optical element with its protective body at least partially immersed in an immersion liquid.

Another advantageous embodiment of the invention consists in that the contact surface of the protective body on the optically effective surface is exposed to a reduced vapor pressure of the immersion liquid through the intermediate space. In addition, it can be provided that the lens is separated from the protective body via an intermediate immersion liquid.

The invention will be explained in more detail in exemplary embodiments with reference to the drawings.

1 shows a sectional view in the direction of the optical axis (vertical sectional view) through a lens arranged above an immersion medium and separated therefrom by a protective plate, FIG. 2 shows an enlarged detail from FIG. 1, FIG.

3 is a sectional view in the plane of the connection between the lens and the protective plate,

Fig. 4 - 9 enlarged detail views in the connection area between the protective plate and the lens in vertical section,

10, 11 are plan views of a plane of the protective plate, which is surrounded by a carrier or by a belt with a drying material,

12 is an enlarged sectional view in detail in the connection region of the protective plate to the lens with a drying agent,

13 a conically ground lens on its side facing the housing,

14 shows the lens according to FIG. 13 in conjunction with a protective body having a base plate and a side plate in a vertical sectional view, FIG.

15 is an enlarged detail of FIG. 15, wherein additionally a splice and a vapor-deposited layer are present,

16, 17, the side plate of FIG. 14 with additionally introduced on the inside depressions,

18, 19 processing steps for applying the protective body to the lens of FIG. 13, 14,

20 shows the connection region between the lens and the base plate and the side plate of the protective body,

21 shows the side plate with additional recesses introduced from the outside, FIG. 22 shows a sectional view in the direction of the optical axis (vertical sectional view) through a further lens arranged above a first immersion medium and separated therefrom by a protective plate and a second immersion medium, Fig. 23 is a sectional view through the lens of FIG. 22, wherein additionally a clamping device is provided for connection between the lens and the protective plate, and Fig. 24 is a further sectional view of a protected by a protective plate and a side shield lens in the optical axis direction.

A plano-convex lens 1 (FIG. 1, 2) introduced in a projection objective as the last optical element preferably consists of a fluoride crystal, preferably of calcium, strontium or barium fluoride. The use of fluoride crystal material for the final optical element is almost mandatory in systems for working wavelengths of 157 nm or less, since other optical materials, such as synthetic silica glass, are not sufficiently transparent for this wavelength. Even with systems operating at longer wavelengths, for example at 193 nm, the use of calcium fluoride for the last optical element may be beneficial, as this near-surface element is exposed to high levels of radiation exposure and calcium fluoride, unlike synthetic silica, is less prone to having radiation-induced density changes. However, since it is not resistant to ultrapure water, it is attacked rather quickly by it as the immersion medium 2, so that the lens 1 is separated from the immersion medium 2 by a protective plate 3 forming a rigid coating. The protective plate 3 consists, for example, of the silica or quartz glass inert to the water.

In order to prevent penetration of the immersion medium 2, the upper level laterally of the lens 1 protrudes higher than the upper level of the protective plate 3, in the connection region of the lens 1 and the protective plate 3, an annular seal 4 is provided, which is formed for example by a Butylabdichtungsmasse, especially a butyl rubber.

However, it is not possible to complete the flexible seal 4 Sealing of the lens 1 with respect to the immersion medium 2, so that even in the area between the seal 4, the lens 1 and the protective plate 3, a low partial pressure of the immersion medium 2 prevails. Therefore, on the inside of the seal 4 between the lens 1 and the protective plate 3, a cavity in the form of a chamber or a particular annular between the lens 1 and the protective plate 3 extending channel 5 is provided with a supply and a discharge channel 6, 7th is connected to the channel or the chamber 5 with an incoming via the Zuleitungska- 6 inert gas such. B. to purge nitrogen and thereby remove the immersed immersion medium 2 via the discharge channel 7.

The channels 6, 7 are introduced either in their lower part in the body of the lens 1, or they run as a whole within a the lens 1 as well as all the other components receiving housing 8. Whether the necessary for the formation of the channel or the chamber 5 contours are provided in the lens 1 or in the protective plate 3 or whether contours are provided in both the lens 1 and in the protective plate 3 depends essentially on the thickness of the protective plate 3 and the protective plate 34 (see Fig. 22, 23 ); This means that in the case of a thicker protective plate 3, 34, the contour is preferably introduced into the protective plate 3, 34.

Due to the elasticity of the seal 4, these shears between the lens 1 and the protective plate 3 can safely accommodate. During operation flows through - either continuously or at certain predetermined time intervals or when exceeding a predetermined maximum allowable partial pressure - a dry gas the cavity or the channel 5 and thus the edge of the Ansprengbereichs and keeps it dry in the sense that there Partial pressure of the immersion liquid is reduced and constantly kept at the lowest possible level.

The protective plate 3 can also advantageously in case of damage on site, d. H. on the projection lens, detached again and replaced with a replacement plate. For this purpose, the annular seal is separated with an extremely thin tool, and then the protective plate 3 is blasted off. A new plate is blown up and then again circumferentially sealed in the edge area. It is understood that the optical parameters such as the refractive index, the thickness, the optical path of the replacement plate must correspond to the previously attached plate 3.

The channel 5 may have different cross-sectional contours, for example a rectangular contour or a trough-shaped contour, as shown in FIGS. 4 and 5. In this case, the channel-forming recess is preferably made on the protective plate 3 in order to minimize the production costs. Alternatively or additionally, however, a corresponding channel-forming recess, for. B. an annular groove can be attached. Accordingly, the gasket 4 has various shapes. If it is formed by a plastically deformable mass, according to the embodiment shown in Fig. 4, in which the channel-forming recess forms a stepped edge of the protective plate 3, a collar 9 is inserted at the outer periphery of the stepped edge to prevent penetration of the sealing compound in prevent the channel 5 formed by the stepped edge of the protective plate 3, the sleeve 9 and the flat surface of the lens 1. The embodiment of FIG. 5, wherein the channel-forming recess, z. B. is an annular groove in the flat surface of the protective plate 3, which is approximately in the vicinity of the edge of the protective plate 3, this attached, is characterized in that very little sealing compound is required. According to a further embodiment (FIG. 6), a projection 10 projecting into the beginning of the channel 7 can be provided in the lens 1 above the channel 5, which projection is formed by the contour of the lens 1, ie the lens comprises at least a part of the lens Channel forming recess. In one embodiment, the recess required for the channel 5 and the seal 4 is formed by the lens 1.

In another embodiment of the invention (Figure 7), a recess (e.g., in the form of an annular groove) is formed in the lens 1 with a e.g. trapezoidal cross-section incorporated to form the channel 5. The contours illustrated in FIGS. 6, 7 can be produced, for example, by ductile turning of a calcium fluoride crystal, whereby this process must be carried out with low stress. This is achieved by low feed rates during processing, by the use of an abrasive with a fine and sharp bonded grain as abrasive, ductile turning in the micrometer range and, if necessary, by subsequent etching and polishing of the circumferential contour.

The channel 5 can be completely or partially filled by a drying agent 11 remaining permanently in it. As a result, ventilation holes in the lens 1 to form the channels 6, 7 omitted. The chamber or the channel 5 for receiving the drying agent 11 is preferably filled only after wringing the protective plate 3 with the desiccant 11. Subsequently, the seal 4 is attached. The space for the channel 5 and the gasket 4 is e.g. formed by removing the protective plate 3 at its upper outer edge, resulting in approximately a step-shaped edge on the protective plate 3.

Alternatively or additionally, the space for the channel 5 and the Seal 4 produced by removing the lower outer edge of the lens 1, as shown in FIG. 9. In this case, the protective plate 3 can advantageously be configured very thinly as an exploded plate, for example with a thickness lying between 5 μm and 100 μm; Also a macroscopic thickness of 1 mm is possible. In this case, however, the protective plate 3 is preferably protected by a few millimeters or even a few nanometers thick Teflon layer or with an organic immersion.

In addition, an indicator can be added to the desiccant 11, so that the state of the desiccant 11 can be recognized with regard to its functionality during the checking and regular cleaning of the protective plate 3. Then, when the capacity of the desiccant 11 is exhausted, as indicated by the indicator, the gasket 4 in the sealing gap can be opened to replace the desiccant 11. In order to be able to carry out this replacement process also on site simply, the desiccant 11 is preferably introduced into a carrier which has approximately the shape of a preferably movable, segmented and jacketed cylinder 12 (FIG. 10). The carrier 12 preferably has a pore structure and consists for example of a glass, in particular foam glass, or a metal, in particular metal foam, wherein the drying agent 11 is introduced into the pores. The segments of the carrier 12 are inserted radially from the outside into the annular gap forming the channel 5. Subsequently, this is sealed with the seal 4.

As an alternative to introducing the carrier 12 into the channel-forming gap, a band 13 (FIG. 11) provided with a material binding the immersion medium, preferably highly dried, preferably provided with a color indicator, can be used Put cord from outside into the channel 5. In this case, the band 13 or the cord contains the desiccant, ie the agent binding the immersion medium.

In addition, at the edge region of the lens 1, which also comes or may come into contact with the immersion medium 2, a protective vapor 14 (FIG. 12) can also be applied in order to prevent water or another immersion medium 2 from penetrating into the lens 1. The Schutzbedampfung 14 may additionally extend over the entire lower surface of the lens 1, where it is adjacent to the protective plate 3. In any case, it is ensured that at least the region below which the drying agent 11 or the band or the cords 13 or another element and / or the annular seal 4 is arranged is covered. In addition, an annular region 14a which adjoins this region inwardly and which is covered by the protective coating 14 is preferably also provided. The protective vapor 14 also protects the desiccant 11 or the carrier or tape or cords 13 against the UV light radiation, for example, the 193 nm wavelength radiation generated by an excimer laser.

The contour of a calcium fluoride lens 1 is made, for example, by grinding with a grinding wheel with grain bonded thereto, then turning with a diamond surface, and etching and polishing the contour. Subsequently, the final fit is made on the plane surface of the lens 1. Then the protective plate 3 is blown up. Then, for example, the wrapping of the annular groove 5 with strings or bands 13; then the sealing is done with a sealant. This is followed by a pass check of the entire component. For precise surface adaptation of one of the surfaces, for example the lens 1 or the protective plate 3, it is also possible, inter alia use a device for ion beam treatment (Ion Beam Figuring, Etching, Ablation).

Instead of the above-described sealing possibilities of an optical component, i. H. For example, a lens 1 with a protective plate 3 and a gasket 4, it can also be provided that this is protected by the use of a rigid protective body against contamination, while at the same time the required transmission of the optical component is maintained substantially.

For this purpose, the lens 1, which is preferably formed as a thick Plankonvex- lens, laterally in the region facing the housing 8 and the socket, ground so that it receives a conical peripheral boundary 15 (Fig. 13). A rigid body 16 (FIG. 14) can be put over the latter, the insides of which are essentially adapted to the contours of the lens 1. In particular on the underside of the lens 1, a base plate 17 belonging to the body 16 is blown against the lens 1. Further, the body 16 has a conical side plate 18 which conforms to the peripheral boundary 15 or preferably, slightly spaced from the peripheral region, this approximately follows. Instead of a single side plate 18, a plurality of individual segments may be present, which are firmly connected to each other and to the base plate 17, for example by an adhesive connection. The body 16 protrudes with its base plate 17 and its side plate 18 into the immersion medium 2 and protects the lens 1 against contamination with the immersion medium second

The base plate 17 and the side plate 18 of the protective body 16, which are preferably both made of the same material, for example of silicon dioxide (eg quartz), are preferably by being joined together by wringing, but in addition they may also be connected to one another by an adhesive 19 (FIG. 15), in particular also, for example, on the side facing the lens 1. On the outside of the body 16, in one embodiment, in particular in the transition region between the base plate 17 and the side plate 18, a rigid layer 20, for example also of silicon dioxide, is applied as protective vapor. The rigid connection of the base plate 17 and the side plate 18 enables various forms of sealing of the two parts of the body 16, which are also rigid. As a method of sealing, the use of a metal, an oxide, welding, soldering, diffusion soldering, etc. come into consideration. Since the base plate 17 is sprinkled against the lens 1, it absorbs expansions of the lens 1 depending on the quality of the application. In addition, on the lens 1, in particular on the wall 15, applied by vapor deposition layer 21, in particular of tantalum pentoxide, be applied.

In order to be able to compensate for a load on both the body 16 and the lens 1 as a result of a thermal expansion, at least one joint 22 (FIG. 16) is preferably additionally integrated into the side plate 18. Alternatively, there may be a plurality of hinges 22, 23, 24 (FIG. 17) each formed by recesses in the wall 18.

In order to be able to project the body 16 (FIG. 18) against the lens 1, it is first placed with its plane surface upwards in a holder 25, then only the conical side plate 18 is slipped over the conical wall 15 of the lens 1, until the planar surface 26 of the lens 1 protrudes above an edge 27 of the side plate 18, the lens now being received by a bearing 28. Then the lens 1 is rotated together with the side plate 18 by means of the holder 25 by approximately 180 ° (Fig. 19). Then, the side plate 18 is pushed by the wall 15 in the direction of the base plate 17 and sprinkled on this and / or glued to this in the region of the edge 27 or only firmly applied to the surface 26 of the lens 1. The connection of the base plate 17 of the body 16 with the side plate 18 is carried out, for example, by wringing laying and / or by gluing, in particular with an inorganic adhesive 29, which is introduced within a slot formed between the wall 15 and the side plate 18 and then this with the Base plate 17 connects.

After that, the body 16 can be sealed from its outside, for example by the vapor deposition or deposition of a quartz protective layer, which substantially or completely prevents penetration of the immersion medium 2 to the lens 1. Preferably, the slot 30 formed between the lens 1 and at least partially the side plate 18 may be aerated during operation of the projection lens, for example with dry nitrogen, to remove any traces of the immersion medium 2.

In order for the side plate or the protective cone 18 to withstand upsets without breaking, in particular in addition to or as an alternative to the joints 22 to 24 introduced on the inside of the side plate 18, recesses 31 (FIG. 21) are introduced on the outside of the side plate 18. This reduces the rigidity of the side plate 18, so that it can perform expansions or compressions. In the upper area 32, the side plate 18 remains stiff, because there are no recesses 30; Also, the straight shape of the downwardly extending rib structure formed by the recesses 18 contributes to the rigidity.

The advantage of the embodiment shown in Fig. 21 consists in that only inert materials come into contact with the immersion medium 2, namely, for example, exclusively silica (eg, quartz), as in the case of a seal 20 (see FIG. Temperature fluctuations occurring during transport are absorbed by the elasticity of the conical side plate 18. The blasting or other connection between the base plate 17 and the flat surface of the lens 1 always remains accessible via the slot or gap 30 of a ventilation by an inert gas.

Since the level of the immersion medium 2 always remains below the upper edge of the side plate 18, only a simple splash protection to protect the lens 1 in the area between this and the side plate 18 is necessary.

In another embodiment of the invention, a lens 33 (FIG. 22) is separated from the immersion medium 2 by a thick protective plate 34. The thickness of the protective plate 34, ie the extension in the direction of the optical axis A, is preferably in the range between 0.1 mm and 10 mm. Since the protective plate 34, if it had been exploded on the underside of the lens 33, would be at least partially blown off under thermal cycling, because the increasing stiffness with the plate thickness of the protective plate 34 generates shear forces in the direction of the cutting surface, which causes an uncontrolled blasting of the protective plate 34 effect, wherein the blasting could occur uncontrollably even after the termination of the load, according to the embodiment shown in Fig. 22, a second immersion medium 35 between the lens 33 and the protective plate 34 is provided as Zwischenimmersion. The immersion medium 35 allows the optical device to which the lens 33 belongs to, temperature differences of more than 20 ° C without affecting the technical performance and the quality of the can withstand optical imaging.

For example, decahydronaphthalene (decalin) or any other liquid which does not attack the lens 33, which consists for example of calcium fluoride, is suitable as the intermediate immersion liquid 35. At the side above the protective plate 34 there is either a single, conically shaped side plate 36, or there are a plurality of interconnected, in particular glued, side plates, the side plate 36 or the plurality of side plates respectively being connected to the protective plate, so that a total of a trough-shaped structure of the side plate 36 and the adjoining lateral plate assembly is formed; As a result, penetration of the outer immersion medium 2 into the region above the protective plate 34 is prevented. The side plate 36 or the plurality of side plates is preferably made of the same material or of a material having at least the same or approximately the same thermal properties as the protection plate 34, since the thermal behavior of the protection body formed by the protection plate 34 and the side plate 36 or the side plates is determined essentially by the lower protective plate 34.

Generally, in the presence of a side shield, such as in the form of the side plate 18 or side plate 36, the material selection of the side guard determines which material dominates the extent of the guard plate 3 and 34, respectively. In the case of a thin protective plate 3 whose expansion behavior is determined essentially by the properties of the lens 1, in the case of a thick protective plate 34 whose expansion behavior is determined by the protective plate 34 itself.

Preferably, between the side plate 36 and the lens 33 a clearance or gap 37 interposed, so that the Zwischenimmersionsflüssigkeit can be replaced. Furthermore, the protective body, consisting of the protective plate 34 and the side plate 36, can be actively and / or passively adjusted relative to the lens 33 by means of at least one holder 38 on a housing wall 39 of a housing receiving the lens system in order to achieve the desired imaging quality , The lens 33 is in turn connected via fasteners 40 to the housing wall 39.

In another embodiment (FIG. 23), the use of an additional adjusting device is not necessary since in this case the protective plate 34 is brought into abutment with the lens 33 by means of at least one contact surface 41. The contact surface 41 may be annular or in the form of a three-point support, wherein the contact surfaces 41 are outside the optically effective range. The attachment of the protective plate 34 takes place for example by means of a clamping device 42, wherein in addition sealing elements are provided at suitable locations in order to prevent penetration of the immersion medium 2 in the region between the lens 33 and the protective plate 34. The sealing elements are designed, for example, analogously to the embodiments, as they are illustrated with reference to Figures 1, 2, 4 - 8. However, the sealing elements can be dispensed with if a side guard 36 is present, as shown in FIG. 22 and attached in a corresponding manner.

In an alternative to this (FIG. 24), the lens 33 is protected on the underside by the protective plate 34 and laterally by the side protection 36. The protective plate 34 is blasted to the lens 33; it has only a small thickness, for example of 50 microns, and carries out an expansion of the lens 33 with. The side shield 36 extends in this embodiment not only laterally to the boundary with respect to the housing, but has an annular lower edge portion 43 as a protective body for protecting the lens 33, which limits the lens 33 down and also like the protective plate 34 to the lens 33rd is blasted. The lens 33 and the edge region 43 form towards the protective plate 34 out a flat boundary surface, to which the protective plate 34 is blasted.

In the zone between the edge region 43 and the protective plate 34 facing boundary layer, an annular channel or an annular gap 44 is provided, which is vented through at least one vent hole 45. It can, according distributed over the circumference, also be provided several vent holes.

Additionally or alternatively to the use of the side guard 36, a circumferential lateral seal, in particular a seal 46 formed by a sealant, may be provided.

It is understood that within the scope of the invention, those embodiments are also encompassed that arise through the combination or exchange of individual features of the embodiments illustrated in the drawings. In particular, different forms of lateral protection plates 18, 36 can be combined both with a protective plate 3 and with a protective plate 34.

Claims

claims

1. lens system or lens mirror system, in particular projection lens, for imaging a pattern arranged in an object plane of the lens system or the lens mirror system, in particular of the projection lens, in particular an object structure, into an image plane of the projection lens with the aid of an immersion medium (2) which is between ei - An optical element (1) of the lens system or the lens mirror system and the image plane is arranged, wherein between the lens system and the immersion medium (2) a protective plate (3, 17) is arranged, characterized in that the side of the element (1) and or at least one means is arranged adjacent to the protective plate (3, 17), which causes the partial pressure of the immersion medium (2) on the outer contour of the element (1), between the element (1) and the protective plate (3, 17) is much lower than over the immersion liquid itself.

2. Lens system or lens mirror system, in particular projection objective, for imaging a pattern arranged in an object plane of the lens system or the lens mirror system, in particular the projection objective, in particular an object structure, into an image plane of the projection objective with the aid of an immersion medium (2), which is located between a is arranged between the lens system and the immersion medium (2) a protective plate (34), characterized in that the side of the element (33) and / or subsequently to the protective plate (34) is arranged at least one means which causes the partial pressure of the im- Mersionsmediums (2) on the outer contour of the element (33), in particular between the element (33) and the protective plate (34), is much lower than above the immersion liquid itself, wherein between the element (33) and the protective plate (34) an intermediate immersion liquid (35) is present.

3. Lens system or lens mirror system according to claim 1 or 2, characterized in that the means comprises sealing means (4, 19, 20).

4. lens system or lens mirror system, in particular projection objective, for imaging a pattern arranged in an object plane of the lens system or the lens mirror system, in particular the projection objective, in particular an object structure, into an image plane of the projection objective with the aid of an immersion medium (2) which is between an optical element (1, 33) of the lens system or the lens mirror system and the image plane, wherein between the lens system and the immersion medium (2) a protective plate (3, 17, 34) is arranged, characterized in that the side of the element (1, 33 ) and / or subsequently to the protective plate (3, 17, 34) at least one means is arranged which causes the partial pressure of the immersion medium (2) on the outer contour of the element (1), in particular between the element (1 ) and the protective plate (3), is much lower than over the immersion liquid itself, in particular between the Elem ent (33) and the protective plate (34) a Zwischenimmersionsflüssigkeit (35) is present, wherein the means at least one of the protective plate (3, 17, 34) adjoining, in particular adhered to this or angeprengte, side wall (18, 36) ,

5. lens system or lens mirror system according to claim 4, characterized in that between the protective plate (3, 17, 34) and the at least one side wall (18, 36) sealing means (4, 19, 20) are mounted.

6. lens system or lens mirror system according to one of claims 1 to 5, characterized in that at least one channel (6, 7) for discharging the immersion medium (2) from the region between the element (1) and the protective plate (3) is present.

7. Lens system or lens mirror system according to one of claims 1 to 6, characterized in that between the element (1, 33) and the protective plate (3, 17, 34) a particular annular channel (5) or a chamber, in particular in Area of the outer contour of the protective plate (3, 17, 34) and / or the element (1, 33), arranged to collect particles of the immersion medium (2).

8. lens system or lens mirror system according to claim 7, characterized in that the channel (5) or the chamber at least partially by a in the protective plate (3, 17, 34) and / or in the element (1, 33) introduced from the outside Ring groove is formed.

9. lens system or lens mirror system according to claim 7 or 8, characterized in that the annular channel (5) with a first conduit (6) for supplying an inert medium and a second conduit (7) for discharging the particles of the immersion medium (2) communicates.

10. lens system or lens mirror system according to claim 9, characterized in that the lines (6, 7) at least partly through the interior of the element (1), in particular through its edge region, run through.

11. Lens system or lens mirror system according to any one of claims 1 to 10, characterized in that between the element (1) and the protective plate (3, 17, 34), in particular adjacent to the annular channel (5), a seal (4) is arranged.

12. lens system or lens mirror system according to claim 11, characterized in that the seal is formed as a continuous ring seal (4) made of a solid elastic material, in particular as butyl seal.

13. lens system or lens mirror system according to claim 11, characterized in that the seal is formed from a sealing compound (4).

14. Lens system or lens mirror system according to any one of claims 11 to 13, characterized in that the seal (4) between two at least substantially coplanar surfaces of the element (1) and the protective plate (3, 17, 34) is arranged.

15. Lens system or lens mirror system according to one of claims 11 to 14, characterized in that the seal (4) between two substantially at an acute or a right angle to each other surfaces of the element (1, 33) and the protective plate (3, 17 , 34) is arranged.

16. Lensensystem or lens mirror system according to one of claims 6 to 15, characterized in that in the channel and / or in an additional, between the element and the Protective plate introduced chamber receiving means (11, 12), in particular silica gel, as a carrier for receiving the immersion medium (2) by a chemical reaction or as a result of adsorption or absorption is present.

17 lens system or lens mirror system according to claim 16, characterized in that the receiving means (12) an indicator, in particular a color indicator, in particular cobalt chloride, is attached, which indicates the consumption of the receiving means due to the reaction, adsorption or absorption.

18. Lens system or lens mirror system according to claim 16 or 17, characterized in that the receiving means in a, in particular adapted to the shape of the channel and / or the chamber, in particular cylindrical, carrier (12) or in a plurality, in particular cylinder-segment-shaped carrier is introduced.

19. lens system or lens mirror system according to claim 18, characterized in that the carrier (12) has a pore structure, wherein the receiving means is embedded in the pore structure.

20. Lens system or lens mirror system according to claim 19, characterized in that the carrier (12) is made of silicon dioxide, of glass, of a metal, in particular of foam glass or of metal foam.

21 lens system or lens mirror system according to claim 8, characterized in that in the annular groove (5) impregnated with a receiving means, in particular hochgetrocknetes, band or impregnated with the receiving means, in particular highly dried, string is introduced as a carrier (12).

22. lens system or lens mirror system according to claim 21, characterized in that the band or the cord (12) is wound several times in the annular groove (5).

23. Lens system or lens mirror system according to one of claims 1 to 22, characterized in that on the element (1, 33) in the region of the arrangement of the means which cause the partial pressure of the immersion medium (2) between the element (1, 33 ) and the protective plate (3, 17, 34) is much smaller than between the protective plate (3, 34) and the pattern, in particular in the region of the channel (5) or another contour for receiving a seal, a Schutzbedampfung (20) is applied which protects the element (1, 33) against water and / or UV radiation.

24. Lensensystem or Linsenspiegelsystem according to one of claims 1 to 23, characterized in that the laterally arranged means (18, 36) made of a rigid material, in particular of the same material or a similar material as the element, in particular calcium fluoride, Strontium fluoride, barium fluoride or lithium fluoride, or from silica or glass, in particular quartz glass, is formed, wherein the protective plate or base plate (17) and the means (18, 36) consist in particular of the same material.

25. Lens system or lens mirror system according to claim 24, characterized in that the element (1, 33) in the region of the laterally arranged means (18) at least partially tapering in the direction of the protection plate covered side of the element tapered circumference ( 15) and that the means (18) is also at least partially conical.

26. Lens system or lens mirror system according to claim 25, character- ized in that the laterally arranged means with the protective plate (17) on the underside of the element (1) is connected to a trough-shaped body (16).

27. Lens system or lens mirror system according to any one of claims 24 to 26, characterized in that the laterally arranged means (18) bonded to the protective plate (17) or connected by a metal or a metal oxide, by welding or soldering or blasted to this is.

28. Lens system or lens mirror system according to claim 27, characterized in that the laterally arranged means (18) is glued to an inside of the trough-shaped body (16) facing the obtuse angle with the protective plate (17), in particular by an inorganic adhesive (29). ,

29. Lens system or lens mirror system according to one of claims 24 to 28, characterized in that there is a gap between the element (1) and the laterally arranged means (18).

30. Lens system or lens mirror system according to claim 29, characterized in that the means (1) is covered in the region of the distance with a coating serving as radiation protection.

31. Lensensystem or lens mirror system according to one of claims 24 to 30, characterized in that the means and the protective plate in the connection region on the outside of a Schutzbedampfung, in particular made of silicon dioxide.

32. lens system or lens mirror system according to one of claims 24 to 31, characterized in that the means in its inner and / or in its outer wall in places at least one recess.

33. A method for applying the protective plate and the means to a conically encircling element of a lens system or the lens mirror system, in particular a projection lens, characterized in that the element is held with its to be covered by the protective plate side up in a holder that then a side-mounting a portion of a hollow cone forming means is slipped over the circumference of the element until it has dropped below the level of the side to be covered by the protective plate, and placed thereon the protective plate placed on the surface to be covered by her especially sprinkled, will.

34. The method according to claim 33, characterized in that subsequently the element together with the protective plate and the means to be attached laterally are rotated together such that the protective plate lies at least substantially below the element and that subsequently the protective plate and the means to a trough-shaped Body are connected to each other, in particular by wringing or sticking.

35. The method according to claim 34, characterized in that the means and / or the protective plate on the off of the element from facing side, in particular in the transition region from the means to the protective plate, is sealed, in particular by the vapor deposition of a quartz protective layer.

36. The method according to any one of claims 33 to 35, characterized in that the means is provided on the outside at least partially with recesses, in particular by Abfrasen.

37. The method according to claim 36, characterized in that a rib structure is produced in the means.

38. Method according to claim 34, characterized in that the protective plate and the means are glued together in the area of the obtuse angle formed between them.

39. A method for removing particles of the immersion medium from a region between the protective plate and the element or from a region between the protective plate, the means and the element, in a lens system according to one of claims 1 to 32, characterized in that an inert gas, In particular, nitrogen or a noble gas is conducted via a first line to the area in which entrains the particles and leads away from the area via a second line.

40. Optical element (1) having at least two optically active surfaces, at least one, at least one optical surface covering and at this, at least partially, on a contact surface adjacent protective body (3), characterized in that between the optical element (1 ) and the protective body (3) outside of the contact surface, a gap (5) is formed, and that the protective body (3) in the region of the contact surface is blasted to the optical element (1).

41. An optical element (1) according to claim 40, characterized in that the intermediate space (5) is open.

42. Optical element (1) according to claim 40, characterized in that the intermediate space (5) is completed.

43. Optical element (1) according to any one of claims 40 to 42, characterized in that the intermediate space (5) is formed by a recess in the optical element (1) and / or the protective body (3).

44. An optical element (1) according to any one of claims 40 to 43, characterized in that the intermediate space (5) by an adhesive and / or a sealant (4) is completed.

45. Optical element (1) according to any one of claims 40 to 44, characterized in that the intermediate space (5) via an inlet and outlet (6, 7) for a fluid has.

46. An optical element (1) according to any one of claims 40 to 45, characterized in that in the intermediate space (5) a partial pressure-reducing material with respect to a substance, in particular with respect to an immersion medium (2) is arranged.

47. An optical element (1) according to any one of claims 40 to 46, characterized in that the optical element (1) is a thick plano-convex or plano-concave lens, wherein the protective body (3) covers at least the planar optical effective surface.

48. Optical element (1) according to claim 47, characterized net, that the lens contains calcium fluoride or a fluoride-containing material.

49. Optical element (1) according to claim 47 or 48, characterized in that: the protective body (3) comprises a plane-parallel or at least approximately plane-parallel plate in the region of the contact surface.

50. An optical element (1) according to any one of claims 47 to 49, characterized in that the protective body (3) comprises at least one edge element for at least partially covering the optically non-effective edge surface of the lens.

51. Optical element (1) according to any one of claims 40 to 50, characterized in that the intermediate space (5) in the region of the plane-parallel or at least almost plane-parallel plate (3) and / or the edge element is formed.

52. Optical element (1) according to claim 51, characterized marked, that the intermediate space (5) annularly surrounding the contact surface with the plane-parallel plate (3) in the vicinity of the edge or at the edge of the optical element (1).

53. Optical element (1) according to any one of claims 40 to 52, characterized in that the optical element (1) with its protective body (3) at least partially immersed in an immersion liquid (2).

54. Optical element (1, 33) according to claim 53, characterized in that exposed by the intermediate space (4, 35), the contact surface of the protective body (3, 34) on the optically active surface a reduced vapor pressure of the immersion liquid (2) is.

55. An optical element (1, 33) according to any one of claims 40 to 54, characterized in that the lens (33) via a Zwischenimmersionsflüssigkeit (35) of the protective body (34) is separated.

56. An optical element (1, 33) according to any one of claims 40 to 55, characterized in that the protective body (3, 34) by at least one clip or by a clamping device (42) with the lens (1, 33) is connected.

57. Optical element (1, 33) according to any one of claims 40 to 55, characterized in that the protective body (3, 34) and / or at least one of the protective body (3, 34) associated side plate (18, 36) and / or the optical element (1, 33) via a fastening (38, 40) with a housing or a housing wall (39) is connected.

58. An optical element (1, 33) according to any one of claims 40 to 55, characterized in that it is protected by a side guard (36) having an annular edge region (43) for protecting the optical element (1, 33), this limited in the direction of the protective body (3, 34).

59. An optical element (1, 33) according to claim 58, characterized in that the edge region (43) to the optical element (1, 33) blasted and / or glued to the optical element (1, 33) and / or sealed ,

60. An optical element (1, 33) according to any one of claims 40 to 55, characterized in that an annular channel or an annular gap (44) in the zone between an edge region (43) and the protective plate (34) facing boundary layer or Interface is provided.

61. The optical element according to claim 60, wherein the annular channel or the annular gap is vented via a vent bore.

62. An optical element (1, 33) according to claim 60 or 61, characterized in that it comprises a side guard (36) and / or a circumferential lateral seal, in particular a gasket formed by a seal (46).