OPTICAL ASSEMBLY HAVING A THERMALLY CONDUCTIVE COMPONENT

Abstract

An optical assembly includes: an optical element, which is transmissive or reflective to radiation at a used wavelength and has an optically used region; and a thermally conductive component, which is arranged outside the optically used region of the optical element. The thermally conductive component can include a material having a thermal conductivity of more than 500 W m.sup.−1 K.sup.−1. Additionally or alternatively, the product of the thickness of the thermally conductive component in millimeters and the thermal conductivity of the material of the thermally conductive component is at least 1 W mm m.sup.−1 K.sup.−1.

Claims

1. An optical assembly, comprising: an optical element that is transmissive or reflective to radiation at a used wavelength, the optical element having an optically used region; and a thermally conductive component arranged outside the optically used region of the optical element, wherein at least one of the following holds: the thermally conductive component comprises a material with a thermal conductivity of more than 500 W m.sup.−1 K.sup.−1; and a product of a thickness of the thermally conductive component in millimeters and the thermal conductivity of the material is greater than 1 W mm m.sup.−1 K.sup.−1.

2. The optical assembly of claim 1, wherein the material has a thermal conductivity of more than 500 W m.sup.−1 K.sup.−1.

3. The optical assembly of claim 1, wherein the material has a thermal conductivity of more than 1000 W m.sup.−1 K.sup.−1.

4. The optical assembly of claim 1, wherein the material has a thermal conductivity of more than 1700 W m.sup.−1 K.sup.−1.

5. The optical assembly of claim 1, wherein the material has a thermal conductivity of more than 2000 W m.sup.−1 K.sup.−1.

6. The optical assembly of claim 1, wherein the product of a thickness of the thermally conductive component in millimeters and the thermal conductivity of the material is greater than 1 W mm m.sup.−1 K.sup.−1.

7. The optical assembly of claim 1, wherein the product of a thickness of the thermally conductive component in millimeters and the thermal conductivity of the material is greater than 10 W mm m.sup.−1 K.sup.−1.

8. The optical assembly of claim 1, wherein the product of a thickness of the thermally conductive component in millimeters and the thermal conductivity of the material is greater than 50 W mm m.sup.−1 K.sup.−1.

9. The optical assembly of claim 1, wherein the material comprises polycrystalline diamond and/or monocrystalline diamond.

10. The optical assembly of claim 1, wherein the material comprises carbon nanotubes.

11. The optical assembly of claim 1, wherein the material comprises a CVD material.

12. The optical assembly of claim 1, wherein the thickness of the thermally conductive component is less than 500 μm.

13. The optical assembly of claim 1, wherein the material comprises a metal.

14. The optical assembly of claim 13, wherein the material comprises an electroformed material.

15. The optical assembly of claim 1, wherein the material comprises a woven fabric.

16. The optical assembly of claim 1, wherein the material comprises a woven fabric, and the woven fabric comprises a metallic material and/or a carbon compound.

17. The optical assembly of claim 1, wherein the thermally conductive component is connected to the optical element.

18. The optical assembly of claim 1, wherein the thermally conductive component is connected to the optical element over at least one surface area at at least one isolated point.

19. The optical assembly of claim 1, wherein the thermally conductive component is connected to the optical element at a connection having a heat transfer coefficient of less than 1000 W m.sup.−2 K.sup.−1.

20. The optical assembly of claim 1, wherein the thermally conductive component is connected to the optical element via a material having a thermal conductivity of less than 1 W m.sup.−1 K.sup.−1.

21. The optical assembly of claim 1, wherein the thermally conductive component is connected to the optical element via a friction-locked connection.

22. The optical assembly of claim 1, wherein the thermally conductive component is arranged at a distance from the optical element.

23. The optical assembly of claim 1, wherein the thermally conductive component is arranged at a distance from the optical element, and the distance is between 100 μm and 1000 μm.

24. The optical assembly of claim 1, wherein the optical element is selected from the group consisting of a lens, a mirror, a plane-parallel plate and a microstructured element.

25. The optical assembly of claim 1, wherein the optical element comprises a material selected from the group consisting of quartz glass, crystalline quartz, a fluoride crystal, titanium-doped quartz glass, a glass ceramic, and a metal.

26. The optical assembly of claim 1, further comprising a heat source, wherein at least one side of the thermally conductive component is connected to the heat source.

27. The optical assembly of claim 26, wherein the heat source is a component configured so that current flows therethrough.

28. The optical assembly of claim 1, further comprising a heat sink, wherein at least one side of the thermally conductive component is connected to the heat sink.

29. The optical assembly of claim 28, wherein the heat sink is a cooler configured so that a gas or a liquid flows flow therethrough.

30. The optical assembly of claim 1, wherein the optical assembly is configured so that, during use of the optical assembly, at least part of the thermally conductive component is exposed to radiation which the thermally conductive component is configured to absorb.

31. The optical assembly of claim 1, wherein the optical assembly is configured so that, during use of the optical assembly, at least part of the thermally conductive component is exposed an evaporating liquid.

32. The optical assembly of claim 31, wherein the evaporation liquid comprises an immersion fluid.

33. The optical assembly of claim 1, wherein the thermal conductivity of the material is more than 500 W m.sup.−1 K.sup.−1; and the product of a thickness of the thermally conductive component in millimeters and the thermal conductivity of the material is greater than 1 W mm m.sup.−1 K.sup.−1.

34. An optical assembly, comprising: a device configured to position a light-sensitive substrate; and a thermally conductive component mounted on the device, wherein at least one of the following holds: the thermally conductive component comprises a material with a thermal conductivity of more than 500 W m.sup.−1 K.sup.−1; and a product of a thickness of the thermally conductive component in millimeters and the thermal conductivity of the material is greater than 1 W mm m.sup.−1 K.sup.−1.

Description

DRAWING

[0050] Exemplary embodiments are depicted in the schematic drawing and are explained in the following description. In the figures:

[0051] FIG. 1 shows a schematic representation of a projection exposure apparatus for immersion lithography with a lens element partially immersed in an immersion fluid,

[0052] FIGS. 2a-d show schematic representations of a number of process steps in the production of a thermally conductive component made of diamond,

[0053] FIGS. 3a-c show schematic representations of process steps for establishing a connection between the thermally conductive component and the lens element from FIG. 1,

[0054] FIGS. 4a-c show schematic representations of a number of process steps in the production of a thermally conductive component made of a metal,

[0055] FIG. 5 shows a schematic representation of a thermally conductive component in the form of a woven fabric that has been slipped onto a lens element,

[0056] FIG. 6 shows a schematic representation of a thermally conductive component for protecting another optical element of a projection lens from the waste heat of a manipulator,

[0057] FIG. 7 shows a representation analogous to FIG. 5 in which the thermally conductive element is used for protecting the other optical element from stray light, and

[0058] FIG. 8 shows a schematic representation of a detail of the optical assembly from FIG. 1 with a wafer table to which a thermally conductive component has been applied.

[0059] In the following description of the drawings, identical reference signs are used for identical or functionally identical components.

[0060] In FIG. 1, an optical assembly 10 in the form of a projection exposure apparatus for microlithography, to be more precise in the form of a wafer scanner, for the production of large-scale-integrated semiconductor components is schematically shown. The optical assembly 10 includes as a light source an excimer laser 11 for generating radiation 9 with a used wavelength λ.sub.B of 193 nm, other used wavelengths, for example 248 nm, also being possible. A downstream illumination system 12 generates in its exit plane a large, sharply delimited, very homogeneously illuminated image field adapted to the desired telecentricity properties of a downstream projection lens 13.

[0061] A device 14 for holding and manipulating a photomask (not shown) is arranged after the illumination system 12 such that the mask lies in the object plane 15 of the projection lens 13 and is movable in this plane for scanning operation in a traveling direction indicated by an arrow 16.

[0062] Following after the plane 15, which is also referred to as the mask plane, is the projection lens 13, which projects an image of the photomask at a reduced scale, for example at a scale of 4:1 or 5:1 or 10:1, onto a wafer 17 coated with a photoresist layer. The wafer 17 used as a light-sensitive substrate is arranged such that the plane substrate surface 18 with the photoresist layer substantially coincides with the image plane 19 of the projection lens 13. The wafer 17 is held by a device 20, which includes a scanner drive, in order to move the wafer 17 synchronously in relation to the photomask and parallel to it. The device 20 also includes manipulators for moving the wafer both in the z direction parallel to an optical axis 21 of the projection lens 13 and in the x and y directions perpendicular to this axis.

[0063] The projection lens 13 has as a final element adjacent to the image plane 19 an optical element 1 in the form of a plano-convex lens with a conical lens part 3, the end face 4 of which forms the last optical face of the projection lens 13 and is arranged at a working distance above the substrate surface 18. Arranged between the end face 4 and the substrate surface 18 is an immersion fluid 22, in the present case water, to be more precise ultrapure water, which increases the output-side numerical aperture of the projection lens 13. Via the immersion fluid 22, the imaging of structures on the photomask can take place with a higher resolution and depth of field than is possible if the intermediate space between the optical element 1 and the wafer 17 is filled with a medium with a lower refractive index, for example air. The gap that forms the intermediate space is generally between 2 mm and 4 mm.

[0064] In the example shown, the lens element 1 consists of synthetic, amorphous quartz glass (SiO.sub.2) and has a conical lens part 3, on the underside of which the end face 4 of the lens element 1 is formed. The radiation 9 produced by the light source 11 passes in a directed manner through the end face 4 of the lens element 1 that forms or delimits an optically used surface region of the lens element 1. A peripheral lateral surface 5, adjoining the end face 4, of the conical lens part 3 is partially wetted by the immersion fluid 22. The conical, radially inward lens part 3 is adjoined by a radially outward plane lens face 2. The radiation 9 of the light source 11 does not pass in a directed manner through either the lateral surface 5 of the conical lens part 3 or the plane lens face 2, i.e. they are outside the beam path of the used radiation 9.

[0065] It goes without saying that optical elements for immersion lithography do not necessarily have to have the plano-convex geometry described above; however, a conically shaped volume region 3 is typical for such optical elements. The optical element 1 may also consist of some other material that is transparent above a wavelength of 250 nm or 193 nm, for example of crystalline quartz glass (SiO.sub.2), barium fluoride (BaF.sub.2) or germanium dioxide (GeO.sub.2).

[0066] Droplets of the immersion fluid 22 may remain on the surface regions 2, 5 of the lens element 1 that are not immersed or only partially immersed in the immersion fluid 22. When these droplets evaporate, there is locally a cooling down of the quartz glass material of the lens element 1, which leads to a local change in the refractive index and also leads to the lens element 1 being deformed locally as a result of the thermal expansion. Both effects can lead to image errors, and are therefore undesired.

[0067] In order to prevent local cooling down of the lens element 1 by the evaporating immersion fluid 22, or to minimize the local temperature gradients thereby occurring, a thermally conductive component 6 (cf. FIG. 2d), the production process of which is described below on the basis of FIGS. 2a-d, is applied to the lens element 1.

[0068] FIG. 2a shows highly schematically a CVD coating apparatus 30, for applying a coating to a carrier body 31, which exactly replicates the relevant contours of the lens element 1, in the present example the contour of the conical lens part 3 with the plane end face 4 and also the radially outward plane lens face 2. The carrier body 31 is located in a coating chamber 32 of the CVD coating apparatus 30, to which precursor gases, in the example shown methane (CH.sub.4) and hydrogen (H.sub.2), are fed in by way of an inlet opening 33. The precursor gases are passed over an incandescent wire 34 and dissociate, the activation or dissociation additionally being intensified by an alternating field RF, which produces a plasma in the coating chamber 32. With suitably chosen operating parameters of the coating apparatus 30, carbon in the form of a diamond layer 37 is deposited on the carrier body 31.

[0069] For producing a polycrystalline or monocrystalline diamond layer 37 on the carrier body 31, it is desirable that the latter is heated up with the aid of a heating element 35 to a temperature of generally more than about 600° C. to 800° C. Materials from which the carrier body 31 is produced should have an (average) coefficient of thermal expansion that is similar at room temperature (22° C.) and at the temperature at which the coating is applied (here: about 800° C.). If this is the case, the deposited diamond layer 37 has few stresses and there are smaller geometrical changes when the carrier body 31 is removed (see below).

[0070] In the present case, i.e. with coating temperatures of about 800° C. or above, Si or SiO.sub.2 are suitable in particular as materials for the carrier body 31. Si offers the advantage over SiO.sub.2 of a high thermal conductivity, which leads to a uniform temperature distribution during the coating, and consequently to uniform layer properties. Many metals can in principle also be coated well, and consequently are suitable in principle as carrier bodies, but generally have much greater differences in the coefficient of thermal expansion in relation to diamond. In order to perfect further the geometry of the deposited diamond layer 37, a change in form as a result of stresses in the production of the diamond layer 37 may also be calculated and/or measured and provisioned for in the geometry or the form of the surface of the carrier body 31.

[0071] The depositing of the diamond layer 37 is carried out until it has a desired thickness D, which is typically more than 25 μm, advantageously more than 100 μm and generally no more than 500 μm. After the completion of the coating, the carrier body 31 is removed from the coating chamber 32 of the coating apparatus 30, as represented in FIG. 2b. On the carrier body 31 there is the diamond layer 37, the thickness of which is sufficient to form a self-supporting component.

[0072] As can be seen in FIG. 2c, the diamond layer 37 is scored into along a predetermined cutting contour 38, which in the example shown is circular, via a laser or by machining.

[0073] In an optional step which then follows, the diamond layer 37 may also be polished and/or microstructured.

[0074] In a step which then follows, the diamond layer 37 is detached from the carrier body 31, for example in that the material of the carrier body 31, for example Si or SiO.sub.2, is dissolved in hydrofluoric acid (HF), whereby a self-supporting component 6 made of diamond or a diamond body with a high thermal conductivity is formed, which is represented in FIG. 2d. The thermal conductivity of the diamond component 6 shown in FIG. 2d is at least 500 W m.sup.−1 K.sup.−1, it being possible with suitable choice of the coating parameters in the CVD process described above to achieve a thermal conductivity of more than 1000 W m.sup.−1 K.sup.−1, preferably of more than 1700 W m.sup.−1 K.sup.−1, ideally of more than 2000 W m.sup.−1 K.sup.−1. Before the self-supporting component 6 made of diamond is applied to the lens element 1, it may also be surface-modified.

[0075] The establishing of a connection between the thermally conductive component 6 shown in FIG. 2d and the lens element 1 from FIG. 1 is described below with reference to FIGS. 3a-c on the basis of the example of an adhesive connection. FIG. 3a shows the lens element 1 onto which a protective layer 40 that is UV resistant and absorbs the UV radiation 9 of the light source 11 has been applied in the region of the lateral surface 5 of the conical lens part 3 and also the radially outward plane lens face 2. The protective layer 40 serves the purpose of protecting an adhesive layer 41 shown in FIG. 3b that has been applied to the thermally conductive component 6 from degradation as a result of stray radiation from the interior of the lens element 1. It goes without saying that, in addition, such a protective layer 40 may also be applied to the inner side, i.e. the side facing the lens element 1, of the thermally conductive component 6 in order to shield the adhesive layer 41 from stray radiation from the environment.

[0076] FIG. 3c shows the composite made up of the lens element 1 and the thermally conductive component 6 after the drying of the adhesive layer 41. As described further above, the thermally conductive component 6 is used for avoiding local temperature changes or temperature gradients in the lens element 1 that could otherwise occur as a result of the evaporation of droplets of the immersion fluid 22. The locally produced cold of evaporation or the droplets form on the thermally conductive component 6 and, on account of its high thermal conductivity, are distributed over a large surface, so that high local temperature gradients no longer occur in the lens element 1.

[0077] In order to keep the heat transfer from the thermally conductive component 6 to the lens element 1 as small as possible, it is advantageous if the adhesive layer 41, and consequently the connection between the component 6 and the lens element 1, has a heat transfer coefficient of less than 1000 W m.sup.−2 K.sup.−1, preferably of less than 100 W m.sup.−2 K.sup.−1. It is also advantageous if the thermally conductive component 6 is connected to the lens element 1 by way of an adhesive 41 that has a thermal conductivity of less than 1 W m.sup.−1 K.sup.−1, preferably of less than 0.1 W m.sup.−1 K.sup.−1. The same also applies to the material of the UV-resistant protective layer 40. As shown in FIGS. 3a-c, the connection may be performed by way of an adhesive layer 41 applied over a surface area or areas, but it is also possible to apply the adhesive only at isolated points, i.e. at a number of adhesive bonding points, along the surface of the thermally conductive component 6 or of the surfaces 2, 5 or 6 to be connected, in order thereby to fix the thermally conductive component 6 to the lens element 1.

[0078] As an alternative to establishing a connection by adhesive bonding, the thermally conductive component 6 may also be connected to the lens element 1 in some other way, for example by so-called low-temperature bonding, in which the component 6 and the lens element 1 are heated up to no more than typically about 400° C. in order to produce the connection. An optical connecting or optical contact bonding of the thermally conductive component 6 to the lens element 1 is also possible. When a thermally conductive component 6 of a metal or of a metallic material is used, the connection may also be performed by soldering.

[0079] FIGS. 4a-c show a number of process steps for producing a thermally conductive component 6 of metal, in the example shown of copper. By analogy with FIG. 2a, FIG. 4a shows highly schematically a coating apparatus 30 for applying a coating to a carrier body 31, which exactly replicates the relevant contours of the lens element 1, in the present example the contour of the conical lens part 3 with the plane end face 4 and also the radially outward plane lens face 2 (cf. FIG. 3a). In a first step, the carrier body 31 is provided with a suitable passive layer (not shown), which prevents a permanent connection between the material used for the coating, in the present case copper, and the carrier body 31 and makes later separation possible. The carrier body 31 is arranged in an electrolysis vessel 50 with a liquid electrolyte 51, into which a copper anode 52 is immersed. The carrier body 31 is connected in an electrically conductive manner to the anode 52 by way of the liquid electrolyte and by way of a DC source 53 and forms the cathode of the electrochemical coating apparatus 30 shown in FIG. 4a. In the electrolysis or the electrolytic coating, the copper material of the anode 52 is deposited on the carrier body 31 used as a cathode. As an alternative, an anode 52, which consists of an insoluble material, may be used for the deposition and the metallic coating material, for example in the form of copper, is contained in the electrolyte or is added to it. With suitably chosen operating parameters of the coating apparatus 30, a copper layer 37 is deposited on the carrier body 31 and surrounds the carrier body 31 substantially completely.

[0080] The depositing of the copper layer 37 is carried out until it has a desired thickness D (cf. FIG. 4b). The desired thickness D depends on the thermal conductivity λ of the coating material used for the electrolytic coating. The depositing of the copper layer 37 is typically carried out until the following applies for the product of the thickness D (in mm) of the copper layer 37 forming the thermally conductive component 6 and the thermal conductivity λ of the copper material: Dλ>1 W mm m.sup.−1 K.sup.−1, preferably Dλ>10 W mm m.sup.−1 K.sup.−1, in particular Dλ>50 W mm m.sup.−1 K.sup.−1. In order to ensure good effectiveness of the thermally conductive component 6, the thickness D of the thermally conductive component 6 (cf. FIG. 4c) is at least 2.5 μm, 25 μm or 100 μm, because copper has a thermal conductivity of λ=400 W m.sup.−1 K.sup.−1.

[0081] After the completion of the coating, the coated carrier body 31 represented in FIG. 4b, also known as a master, is removed from the electrolysis chamber 50 of the coating apparatus 30. On the carrier body 31 there is the copper layer 37, the thickness D of which is sufficient to form a self-supporting thermally conductive component 6, which is represented in FIG. 4c.

[0082] As can be seen in FIG. 4b, to produce the thermally conductive component 6 the copper layer 37 is scored into along two predetermined cutting contours 38a, 38b, which in the example shown are circular, via a laser or by machining. As an alternative, the carrier layer 31 may be masked before the metal deposition, so that it is only provided with a copper layer 37 in a desired partial region. The passive layer applied before the coating makes it possible for the copper layer 37 to be detached from the carrier body 31 without being damaged. On account of the different coefficients of thermal expansion of the carrier body 31 and the component 6, the detaching operation can be assisted by rapidly supplying heat/cold. If desired, the carrier body 31 may be used for further electrolytic coating processes.

[0083] The thermally conductive component 6 detached from the carrier body 31 has on its radially outward edge a peripheral collar 54, which makes it easier to fasten the thermally conductive component 6 to the optical element 1 from FIG. 1 via a clamping connection. At the peripheral collar 54, the thermally conductive component 6 may be pressed by a peripheral mounting ring 55 in the radial direction against the lens element 1 (not shown in FIG. 4c), as indicated by arrows in FIG. 4c. The thermally conductive component 6 may possibly be slightly deformed (bent) thereby in the region of the peripheral collar 54, so that the latter adapts itself to the convex geometry of the lens element 1. A circular geometry of the collar 54 is advantageous because the thermally conductive component 6 is in this case free of undercuts, and can consequently be detached from the carrier body 31 in an easy way.

[0084] The mounting ring 54 forms a clamping connection, which fixes the thermally conductive component 6 in its position in relation to the lens element 1. The thermally conductive component 6 here abuts the lens element 1, i.e. it is not arranged at a distance from the lens element 1. Instead of the clamping connection 54, the thermally conductive component 6 may also be fixed in its position in relation to the lens element 1 via a screwing connection. Typically formed in this case in the thermally conductive component 6 are through-holes for screws, which can be fixed on a mount (not shown in FIG. 4c) of the lens element 1 or on a component, for example a mounting, of the projection lens 13. As an alternative, the thermally conductive component 6 may also be connected to the lens element 1 by a cohesive connection, for example by adhesive bonding or by soldering. It goes without saying that some other material, in particular a metal material, can be used instead of copper for producing the thermally conductive component 6.

[0085] FIG. 5 shows the lens element 1 from FIG. 1 having a thermally conductive component 6 the material of which forms a preformed metallic woven fabric 56. The preforming or production of the woven fabric 56 may be performed for example in a manner such as that used for the sheathing of cables. The preformed woven fabric 56 has a bend or a kink in the region of the transition between the plane lens face 2 and the lateral surface 5 of the conical lens part 3. The preformed thermally conductive component 6 consequently has a geometry that is adapted to the geometry of the lens element 1. In particular, the region of the woven fabric 56 that covers the conical lens part 3 or the lateral surface 5 may if desired be produced here with slightly smaller dimensions than the dimensions of the lateral surface 5 of the conical lens part 3 itself. In this way, this region of the woven fabric 56 can exert a mechanical stress on the conical lens part 3 during the attachment of the thermally conductive component 6. The mechanical stress can if desired prevent sliding of the thermally conductive component 6 on the lens element 1.

[0086] In the example shown in FIG. 5, the thermally conductive component 6 has a peripheral collar 54, which can be slipped onto the edge of the lens element 1 in order to fix the woven fabric 56 on the lens element 1. The radial force that the woven fabric 56 exerts on the edge of the lens element 1 is generally not great enough to fix the latter securely on the lens element 1. The woven fabric 56 may therefore be additionally fixed on the lens element 1, for example via a clamping connection 55 in the form of a peripheral mounting ring.

[0087] When a thermally conductive component 6 in the form of a woven fabric 56 is used, it may be that the penetration of the immersion fluid 22 into an intermediate space between the thermally conductive component 6 and the lens element 1 cannot be prevented completely. The thermally conductive component 6 allows any inhomogeneities in the temperature that may be caused by cold of evaporation to be distributed over the entire plane lens face 2 and also the lateral surface 5 of the conical lens part 3. Consequently, imaging errors of the lens element 1 can be reduced even when a not completely liquid-impermeable woven fabric 56 is used as the thermally conductive component 6. The thickness D of the thermally conductive component 6 is chosen such that the product of the thickness D and the thermal conductivity λ of the thermally conductive woven fabric 56 is more than 1 W mm m.sup.−1 K.sup.−1, preferably more than 10 W mm m.sup.−1 K.sup.−1, in particular more than 50 W mm m.sup.−1 K.sup.−1. As an alternative or in addition to metallic materials, for example Al, Ag, Cu, Cr, . . . , carbon compounds may also be used for producing the woven fabric 56.

[0088] FIG. 6 shows a further possibility for using the thermally conductive component 6, to be precise as a shielding for another lens element 7 of the projection lens 13 (cf. also FIG. 1). In the example shown, the thermally conductive component 6 is arranged between a heat source in the form of an actuator 42 and the further lens element 7. In the example shown, the thermally conductive component 6 is produced from diamond and is arranged outside the optically used volume region 4 of the further lens element 7 within which the radiation 9 of the light source 11 passes in a directed manner through the further lens element 7 (indicated by dashed lines in FIG. 6). The thermally conductive component 6 is adapted to the geometry or to the curvature of the further lens element 7 and is arranged at a distance A from the further lens element 7 that is about 500 μm. Typical values for the distance A between the further lens element 7 and the thermally conductive component 6 are between about 100 μm and about 1000 μm.

[0089] The actuator 42 is used for actuating or moving a mounting element 8 for the further lens element 7. For this purpose, the actuator 42 is passed through at times by current that is delivered by a voltage source 43. The actuator 42 is heated by the current flow and thereby changes its form in order to act on the mounting element 8 and displace the other lens element 7. The heating causes the actuator 42 to give off thermal radiation 44 (IR radiation) to the environment, in the example shown the proportion of the thermal radiation 44 that is incident on the lens element 1 being absorbed by the thermally conductive component 6.

[0090] In the example shown, the material of the thermally conductive component 6 is diamond, which represents a material that is transparent to the thermal radiation 44. To make the thermally conductive component 6 opaque to the thermal radiation, in the example shown in FIG. 6 a coating 6a that absorbs the thermal radiation 44 has been applied to the thermally conductive component 6 on the side that is facing the actuator 42.

[0091] The thermal radiation 44 that is taken up or absorbed by the thermally conductive component 6 is transmitted from it to the mounting 8 to which the thermally conductive component 6 is fastened. The mounting element 8 itself, or in the case shown a cooler 46 that is connected to the latter and is flowed through by a cooling medium, for example water, is used for dissipating the heat transmitted to the mounting element 8. It goes without saying that it is only by way of example that the mounting element 8, the thermally conductive component 6 and the actuator 42 are shown in FIG. 6 only on one side of the further lens element 7, and that conversely one or more thermally conductive components 6 may if desired be arranged in a distributed manner along the circumference of the further lens element 7, as long as a plurality of actuators are provided for the movement of the lens element 7. Unlike the situation shown in FIG. 6, the thermally conductive component 6 may if desired also extend annularly around the beam path of the used radiation 9.

[0092] FIG. 7 shows a representation analogous to FIG. 6 in which the thermally conductive component 6 is likewise used as shielding for the further lens element 7. However, the thermally conductive component 6 is in this case used for shielding stray radiation 45 that originates from the beam path of the radiation 9 of the light source 11. The wavelength of the stray radiation 45 generally corresponds to the used wavelength 4, or deviates only slightly from the used wavelength λ.sub.B. The diamond material of the thermally conductive component 6 is opaque to UV wavelengths (<220 nm), and therefore absorbs the stray radiation 45 without an additional coating. As described in connection with FIG. 6, the heat produced during the absorption of the stray radiation 45 is transported by the thermally conductive component 6 by way of the mounting element 8 to the cooler 46 and is removed by the latter or a cooling medium flowing in it.

[0093] Another application for a thermally conductive component 6 that has been produced in the way described in connection with FIGS. 2a-d is represented in FIG. 8, which shows in the form of a detail the projection lens 13 and also the wafer 17, used as a light-sensitive substrate, that is mounted on a wafer table 60 for positioning. The assembly shown in FIG. 6 differs from the assembly shown in FIG. 1 substantially in that the expansion of the immersion fluid 22 is restricted to a region 72 between the wafer 17 and the last optical element 1 of the projection lens 13. The wafer 17 is arranged here such that its plane substrate surface 18 substantially coincides with the image plane 19 of the projection lens 13. The wafer table 60, and with it the wafer 17, can be moved in the X direction via a displacing device that is not represented in FIG. 6, so that different regions on the wafer 17 can be moved to during the exposure.

[0094] Via a feeding device 70 and a suction extracting device 71, the immersion fluid 22 is on the one hand fed to the region 72 between the last optical element 1 and the wafer 17 and on the other hand is extracted from it, so that even during the movement of the wafer table 60 the immersion fluid 22 remains restricted to the region 72 between the feeding device 70 and the suction extracting device 71. The suction extracting device 71 generally works with a negative pressure with respect to the environment, so that the immersion fluid 22 can be easily taken up by way of an inlet 73. This allows a continuous (and dynamic) exchange of the immersion fluid 22 to take place, while it remains restricted to the partial region of the substrate surface 18 that is currently being used for the exposure.

[0095] The local wetting in the region 72 offers the advantage that only small amounts of immersion fluid 22 have to be accelerated during the displacement of the wafer table 60. There are thus no undesired turbulences in the immersion fluid 22, and wave formation on account of the inertia of the immersion fluid 22 can be avoided.

[0096] Mounted on the wafer table 60, to be more precise to its upper side 64, in the present example is a thermally conductive component 6 made of diamond, which is in the form of a plate. The fastening of the thermally conductive component 6 to the wafer table 60, which may be formed for example entirely or partially from cordierite or from Zerodur®, may be performed for example in the way described further above in conjunction with FIGS. 3a-c. With the aid of the thermally conductive component 6 it is possible to prevent parts of the immersion fluid or droplets that are not taken up by the suction extracting device 71 that reach a region of the upper side 64 of the wafer table 60 that is not covered by the wafer 17 and wet this region in an undesired way when there is a jerky movement of the wafer table 60 and/or the wafer 17 is exchanged for another wafer (for example in the X direction), from leading to a local lowering of the temperature of the material of the wafer table 60. In order to produce a temperature distribution that is as uniform as possible in the thermally conductive component 6, the latter may if desired be in connection with a heat source (not shown) or a temperature stabilizer in order to keep the thermally conductive component 6 at a constant temperature that coincides with the temperature of the heat source.

[0097] As an alternative to the use of CVD diamond as a material for the thermally conductive component 6, other materials may also be used, as long as they have the desired high thermal conductivity of more than 500 W m.sup.−1 K.sup.−1 at room temperature, for example carbon nanotubes. It is also possible to use other thermally conductive components 6 in the case of which the product of the thickness D of the thermally conductive component 6 and the thermal conductivity λ of the thermally conductive material has a value greater than 1 W mm m.sup.−1 K.sup.−1, preferably greater than 10 W mm m.sup.−1 K.sup.−1, in particular greater than 50 W mm m.sup.−1 K.sup.−1. If an optical assembly is operated at an operating temperature other than room temperature, for example at very low temperatures of less than about −195° C., there is a broader selection of materials that have the desired high thermal conductivity. At these temperatures, for example, sapphire may also be used as a material for the thermally conductive component.

[0098] Other application areas in which a thermally conductive component that is appropriately adapted in its geometry can be meaningfully used are for example mirrors for EUV lithography, the substrate materials of which, such as for example ULE® or Zerodur®, may likewise be protected via the thermally conductive component 6 from undesired local changes in temperature or from excessive local temperature gradients.