Apparatus for focusing laser radiation, and lithography system comprising an apparatus of this kind

Abstract

The present invention relates to a lithography system having an apparatus (3) for focusing laser radiation (11) onto a target region (40) in which a target material is arranged which emits extreme ultraviolet radiation (12), EUV radiation, when irradiated with the laser radiation (11), having an interior (30) and at least one focusing element (32, 33), in particular a mirror, arranged in the interior (30) for focusing the laser radiation (11), and having a radiation-absorbing element (35, 45, 55), in particular arranged in the interior (30), having an absorption surface (101) for absorbing laser radiation backscattered and / or reflected back by the target material, wherein the radiation-absorbing element (35, 45, 55) comprises a device for active cooling, in particular a cooling channel (102) for conducting a coolant.

Description

[0001] Device for focusing laser radiation and

[0002] Lithography system

[0003] The present invention relates to a device for focusing laser radiation onto a target area in which a target material is arranged that emits extreme ultraviolet radiation upon irradiation with the laser radiation. The device comprises an interior space and at least one focusing element, in particular a mirror, arranged in the interior space for focusing the laser radiation. Furthermore, the invention relates to a lithography system comprising such a device.

[0004] Such focusing devices are used to generate extreme ultraviolet radiation. Extreme ultraviolet radiation, also known as EUV radiation, refers to the spectral range of electromagnetic radiation between 10 nm and 121 nm, which is used in lithography systems to image fine, high-precision structures in microchip manufacturing. To generate this extreme ultraviolet radiation, a target material is typically placed in a target area. A laser generates pulsed laser radiation, which is amplified by one or more amplifiers and focused onto the target material in the target area by a focusing device.

[0005] During irradiation, the target material, for example a tin droplet, enters a plasma state in which extreme ultraviolet radiation is emitted. This also results in diffuse scattering and reflections of the laser radiation on the target material and on components located behind the target material in the propagation direction of the laser radiation. This laser light is, among other things, scattered and / or reflected back into the focusing device. Since the pulsed laser radiation used here is very energetic, large amounts of energy can be absorbed by the housing parts and optical components of the focusing device. This poses the risk that the performance of the focusing device or the entire system will be impaired by undesired heating or deformation of housing parts or optical components. Against this background, the task of preventing undesired heating or deformation arises.To reduce deformations of housing parts or optical components caused by backscattered and / or reflected laser radiation during the generation of EUV radiation.

[0006] To achieve this object, a device for focusing laser radiation according to patent claim 1 is proposed. This is a device for focusing laser radiation onto a target area in which a target material is arranged which emits extreme ultraviolet radiation, EUV radiation, upon irradiation with the laser radiation, with an interior space and at least one focusing element, in particular a mirror, arranged in the interior space for focusing the laser radiation, and with a radiation-absorbing element arranged in the interior space with an absorption surface for absorbing laser radiation backscattered and / or reflected back by the target material, wherein the radiation-absorbing element comprises a device for active cooling, in particular a cooling channel for guiding a coolant.

[0007] According to the invention, a radiation-absorbing element is provided which absorbs laser radiation backscattered and / or reflected by the target material and therefore reduces the scattering and reflection of the laser radiation, at least at the position where the radiation-absorbing element is located. This measure can reduce the effect of the laser radiation backscattered and / or reflected into the interior on other components, such as housing parts and optical components. As a result, unwanted heating or deformation of housing parts or optical components is reduced or prevented. The radiation-absorbing element further comprises a device for active cooling, so that heat energy generated by the absorption of the backscattered and / or reflected laser radiation by the radiation-absorbing element can be dissipated by the radiation-absorbing element.This also prevents unwanted heat transfer from the radiation-absorbing element to housing parts or optical components of the device.

[0008] The radiation-absorbing element can, for example, be plate-shaped, i.e., e.g., as a radiation-absorbing plate. Such a design offers the advantage that the radiation-absorbing element can be arranged on an inner contour of the interior. The radiation-absorbing element preferably comprises one or more fastening devices, for example, through-holes, by means of which the radiation-absorbing element can be fixed in the interior. In addition, the one or more fastening devices can also be designed as an elastic joint, for example, in the form of a floating bearing. Such a design can comparatively reduce the mechanical stress acting on the radiation-absorbing element.

[0009] The device for active cooling preferably comprises at least one cooling channel for conducting a coolant. The active cooling of the radiation-absorbing element can be effectively achieved via the coolant and can be controlled by adjusting the coolant flow. The coolant can be a cooling fluid, for example, water or oil. If the radiation-absorbing element has one or more cooling channels, these are preferably arranged at a distance from the highly absorbent surface structure, for example, inside the radiation-absorbing element or on a rear side of the radiation-absorbing element opposite the absorption surface.

[0010] The focusing element can be a mirror. The device for focusing laser radiation preferably comprises several mirrors. The mirrors can be configured to deflect the laser radiation and / or to focus the laser radiation.

[0011] According to an advantageous embodiment of the invention, the target area is located outside the interior space, and the device comprises an exit opening through which the laser radiation focused by means of the at least one focusing element can exit the device in the direction of the target area. The radiation-absorbing element is arranged in the interior space such that laser radiation backscattered and / or reflected by the target material and entering through the exit opening strikes the absorption surface without interacting with other elements in the interior space. In this respect, the radiation-absorbing element is preferably arranged in direct line of sight to the point in the target area at which the backscattering and / or backreflection occurs.Due to this arrangement, so to speak, in the direct field of view of the backscattered and / or back-reflected laser radiation, a large proportion of the total backscattered and / or back-reflected laser light can be absorbed by the radiation-absorbing element.

[0012] According to an advantageous embodiment of the invention, at least one interior trim element is arranged in the interior, which is configured such that laser radiation backscattered and / or reflected by the target material and entering through the exit opening impinges on the absorption surface after being reflected by the interior trim element in the interior. By means of an interior trim element configured in this way, backscattered and / or reflected radiation can be specifically scattered or reflected onto the radiation-absorbing element. In this respect, the radiation-absorbing element can indirectly absorb backscattered and / or reflected laser radiation.

[0013] According to an advantageous embodiment of the invention, the radiation-absorbing element comprises a base body made of a material, wherein the absorption surface is formed by a highly absorbent surface structure of the material of the base body. By using a highly absorbent surface structure of the material, a coating of the material can be omitted. Coatings often result in outgassing, which can lead to undesirable contamination during use under vacuum conditions. Such outgassing does not occur with an absorption surface formed by a highly absorbent surface structure. Furthermore, the material can be selected such that it is robust against the conditions prevailing in the interior.For example, when using the device to focus laser radiation in an EUV lithography system, exposure to EUV radiation and / or hydrogen radicals may occur. By eliminating the need for a coating, only the material needs to be selected based on these conditions.

[0014] According to an advantageous embodiment of the invention, the material is a metal, in particular aluminum. Such materials are resistant to the effects of hydrogen radicals.

[0015] According to an advantageous embodiment of the invention, the highly absorbent surface structure is formed from laser-induced periodic surface structures. Such surface structures are referred to as laser-induced periodic surface structures (LIPSS). This highly absorbent surface structure has microscopic dimensions and leads to a significant reduction in scattering and specular reflection.

[0016] According to an advantageous embodiment of the invention, the highly absorbent surface structure has structures with an extension perpendicular to a main extension plane of the absorption surface in the range from 10 micrometers to 15 micrometers, preferably in the range from 11 micrometers to 14 micrometers, for example in the range from 12 micrometers to 13 micrometers. Alternatively or additionally, the highly absorbent surface structure preferably has structures with an extension in the main extension plane of the absorption surface in the range from 5 micrometers to 30 micrometers, preferably in the range from 10 micrometers to 20 micrometers. Such highly absorbent surface structures have proven to be particularly strongly absorbent, in particular with regard to electromagnetic radiation with a wavelength of 10.6 micrometers.

[0017] According to an advantageous embodiment of the invention, the highly absorbent surface structure is configured such that it diffusely scatters 18% to 30% of the incident laser radiation and specularly reflects 0.01% to 1% of the incident laser radiation. A radiation-absorbing element configured in this way can significantly reduce the reflected radiation power compared to an unstructured surface, such as bare aluminum. The scattering and reflection properties of the highly absorbent surface structure can be determined, for example, using a so-called BRDF measurement known from the prior art, where BRDF stands for "bidirectional reflectance distribution function." Such a measurement can be performed, for example, using a so-called gonioreflectometer, by means of which the proportions of scattered and reflected radiation can be analyzed at different angles of incidence.

[0018] A further subject matter of the invention is a lithography system with a device for focusing laser radiation onto a target area in which a target material is arranged which emits extreme ultraviolet radiation, EUV radiation, when irradiated with the laser radiation, with an interior space and at least one focusing element, in particular a mirror, arranged in the interior space for focusing the laser radiation, and with a radiation-absorbing element, in particular arranged in the interior space, having an absorption surface for absorbing laser radiation backscattered and / or reflected back by the target material, wherein the radiation-absorbing element comprises a device for active cooling, in particular a cooling channel for guiding a coolant.

[0019] In the lithography system according to the invention, the same technical advantages and effects can be achieved as have already been explained in connection with the device for focusing laser radiation according to the invention.

[0020] The lithography system preferably comprises one or more radiation sources for generating laser radiation. Particularly preferably, the radiation sources are configured to generate pulsed laser radiation. The radiation sources can, for example, be radiation sources that generate laser radiation with a wavelength of 10.6 micrometers and / or 1 micrometer.

[0021] To amplify the laser radiation, the lithography system preferably has one or more optical amplifiers. The optical amplifier(s) are preferably arranged in the beam path of the lithography system between the respective radiation source and the aforementioned device for focusing laser radiation.

[0022] The target area in which the target material is arranged is preferably located outside the interior of the focusing device, in particular in a target chamber. The target material can be tin, in particular tin in droplet form. The EUV radiation generated in the target chamber can be guided to an exposure device via suitable radiation guide elements. The exposure device is preferably configured to expose semiconductor substrates, in particular semiconductor wafers.

[0023] According to an advantageous embodiment of the lithography system according to the invention, the radiation-absorbing element is arranged in a target chamber in which the target region is located or in an exposure device configured to use extreme ultraviolet radiation, EUV radiation, for exposure. Radiation-absorbing elements arranged in this way can absorb backscattered and / or reflected laser radiation in the target chamber or in the exposure device. In this way, unwanted heating or deformation of housing parts or optical components in the target chamber or the exposure device caused by backscattered and / or reflected laser radiation during the generation of EUV radiation can be reduced.

[0024] Alternatively or in addition to the advantageous embodiments explained above, the advantageous embodiments and features explained in connection with the device according to the invention can be used in the method.

[0025] Further details and advantages of the invention will be explained below with reference to the exemplary embodiments shown in the figures. Herein:

[0026] Fig. 1 shows a lithography system according to an embodiment of the invention in a block diagram; Fig. 2 shows a detail of the lithography system from Fig. 1 with a device for focusing laser radiation according to an embodiment of the invention in a schematic representation;

[0027] Fig. 3 shows a radiation-absorbing element according to Fig. 2 in a schematic sectional view;

[0028] Fig. 4 shows the absorption surface of the radiation-absorbing element from Fig. 1 in a schematic sectional view;

[0029] Fig. 5 is a diagram of the angle-dependent scattering of the radiation absorbing element of Fig. 3 at an angle of incidence of 10 degrees;

[0030] Fig. 6 is a diagram of the angle-dependent scattering of the radiation-absorbing element of Fig. 3 at an angle of incidence of 70 degrees;

[0031] Fig. 7 shows a device for focusing laser radiation according to a second embodiment of the invention in a schematic representation; and

[0032] Fig. 8 shows a device for focusing laser radiation according to a third embodiment of the invention in a schematic representation.

[0033] The illustration in Fig. 1 shows a lithography system 10 according to an embodiment of the invention. The lithography system 10 comprises at least one radiation source 1, by which, in particular, pulsed laser radiation 11 can be generated. Even if only one radiation source 10 is shown here, two radiation sources 1 can be provided, for example, to generate pre-pulses and main pulses of the laser radiation, which each follow one another in close temporal proximity and are focused on a target area 40.

[0034] Another component of the lithography system 10 is an optical amplifier 2, which optically amplifies the laser radiation 11 generated by the radiation source 1. To achieve greater amplification effects, several optical amplifiers 2 can be arranged in series, in contrast to the illustration in Fig. 1.

[0035] The amplified laser radiation 11 is then fed to a device 3, which focuses the laser radiation 11 onto a target area 40, in which a target material is arranged that emits extreme ultraviolet radiation, EUV radiation, when irradiated with the laser radiation. According to the exemplary embodiment, the target area 40 is arranged in a target chamber 4 in which vacuum conditions prevail. The target material can be tin, for example, which is provided in droplet form. Energy can be supplied to the tin droplet by a pre-pulse, for example pulsed laser radiation 11 with a wavelength of approximately 1 micrometer or approximately 10.6 micrometers, in order to precondition it for a main pulse, so that the tin droplet expands, vaporizes, ionizes and / or a weak or possibly strong plasma is generated.By applying a main pulse shortly following the pre-pulse, for example, pulsed laser radiation 11 with a wavelength of approximately 2 micrometers or approximately 10.6 micrometers, the majority of the material affected by the pre-pulse can be converted into the plasma state, generating extreme ultraviolet radiation 12, or EUV radiation. This EUV radiation 12 is then fed to an exposure device 5 of the lithography system 10, in which the EUV radiation 12 can be used to expose semiconductor substrates.

[0036] Fig. 2 shows, in a more detailed, but nevertheless schematic representation, the device 3 for focusing the laser radiation 11, the target chamber 4 and the exposure device 5 of the lithography system 10 according to Fig. 1. The laser radiation 11 enters the device 3 through an inlet opening 31. The device 3 for focusing the laser radiation 11 comprises a plurality of focusing elements 32, 33, here two mirrors, for focusing the laser radiation 11 onto the target area 40. While the focusing elements 32, 33 are arranged in an interior space 30 of the device 3, the target area is located outside this interior space in the target chamber 4. In this respect, the laser radiation 11 is deflected and focused by the focusing elements 32, 33 and exits from an exit opening 34 of the device 3 and into the target chamber 4. In the target chamber 4, the laser radiation 11 hits the target material, here a tin droplet.The EUV radiation resulting from the interaction between target material and incident laser radiation 11 is directed towards the exposure device 5.

[0037] However, since a certain proportion of the laser radiation is also scattered by the target material, measures have been taken in the lithography system 10 to reduce the effects of the backscattered and / or reflected laser radiation on housing parts and optical components. For this purpose, the device 3 for focusing the laser radiation 11 comprises a radiation-absorbing element 35 arranged in the interior 30, said element having an absorption surface 101 for absorbing laser radiation backscattered and / or reflected by the target material, said element comprising a device for active cooling. The radiation-absorbing element 35 reduces the scattering and reflection of laser radiation backscattered and / or reflected from the target area 40 and absorbs a large part of the corresponding energy, which is dissipated by the active cooling. This prevents unwanted heating orDeformations of housing parts or optical components caused by backscattered and / or reflected laser radiation are reduced.

[0038] The illustration in Fig. 2 shows an arrangement of the radiation-absorbing element 35 in the interior space 30 such that laser radiation backscattered and / or reflected by the target material and entering the interior space 30 of the device 3 through the exit opening 34 strikes the absorption surface 101 without interaction with other elements in the interior space 30. In this respect, the laser radiation backscattered and / or reflected from the target region 40 strikes the radiation-absorbing element 35 directly. Furthermore, an interior lining element 36 is also arranged in the interior space 30, which is configured such that laser radiation backscattered and / or reflected by the target material and entering through the exit opening 34 strikes the absorption surface 101 of the radiation-absorbing element 35 after reflection by the interior lining element 36.

[0039] As can be seen from the illustration in Fig. 2, it is alternatively or additionally possible for a radiation-absorbing element 45, 55 to be arranged in the target chamber 4 or the exposure device 5 in order to absorb laser radiation scattered into these areas and to protect the target chamber 4 or the exposure device 5 from heating and possible deformation.

[0040] Fig. 3 shows a schematic, side sectional view of a radiation-absorbing element 35, 45, 55, which can be used in the lithography system 10 according to Fig. 1. The radiation-absorbing element 35, 45, 55 has a plate-like configuration and an absorption surface 101, which, when installed as part of the lithography system 10, is oriented such that backscattered and / or retroreflected laser radiation can impinge on it. The radiation-absorbing element 35, 45, 55 is formed from a material, in the interior of which, i.e., at a distance from the absorption surface 101, at least one cooling channel 102 for conducting a coolant is arranged. The radiation-absorbing element 35, 45, 55 can be actively cooled via this cooling channel 102.

[0041] According to the exemplary embodiment shown here, the radiation-absorbing element 35, 45, 55 has a base body made of a metal, for example, aluminum. The absorption surface 101 is formed by a highly absorbent surface structure of this metal. The metal is not coated in the region of the absorption surface 101. This highly absorbent surface structure is formed from laser-induced periodic surface structures.

[0042] Fig. 4 schematically shows the highly absorbent surface structure with its periodic structures. These are generated using an ultrashort pulse laser and result in a large-area black marking of the material in the region of the absorption surface 101. The highly absorbent surface structure comprises structures with an extension H perpendicular to a main extension plane of the absorption surface 101 in the range of 10 micrometers to 15 micrometers. These structures comprise an extension B in the main extension plane of the absorption surface in the range of 5 micrometers to 30 micrometers.

[0043] The illustrations in Figs. 5 and 6 show the angle-dependent scattering ARS of the radiation-absorbing element 35, 45, 55 from Fig. 3 at an angle of incidence of 10 degrees (Fig. 5) and 70 degrees (Fig. 6). It can be seen that the intensity of the radiation scattered by the radiation-absorbing element 35, 45, 55 is low over a wide angle range, thus achieving a high intensity attenuation. The intensity maxima at +10° and +70° are specular reflections at the respective angle of incidence. At -10° and -70°, a sensor used for measurement blocks incoming radiation, which leads to the intensity minima. The intensity drops at + / -90 0 are caused by the angle of incidence of the light, due to which only minimal portions of the incident radiation are scattered and / or reflected at the highly absorbent surface structure of the absorption surface 101.

[0044] If one considers the entire angular space or integrates over it, one obtains the values ​​shown in Table 1 for the reflectance TS taking only diffuse scattering into account and the reflectance R taking only specular reflection into account.

[0045] Table 1 :

[0046] Angle of incidence 10° 30° 50° 70°

[0047] R [%] 0.004 0.005 0.06 1 .03 It can be seen that the highly absorbent surface structure of the absorption surface 101 is configured such that it diffusely scatters 18% to 30% of the incident laser radiation and specularly reflects 0.01% to 1% of the incident laser radiation.

[0048] Fig. 7 shows a schematic representation of a second embodiment of a device 3 for focusing the laser radiation 11, which can be used alternatively in the lithography system 10 according to Fig. 1. Fig. 7 also shows a part of the adjacent target chamber 4 with the target region 40. In the device 3 according to the second embodiment, laser radiation 11 enters the interior 30 of the device 3 through an inlet opening 31. To focus the laser radiation 11, a total of three focusing elements 32, 33, 33', here three mirrors, are provided in the second embodiment, by means of which the laser radiation 11 is focused onto the target region 40 in the target chamber 4. In this respect, the laser radiation 11 is deflected by the focusing elements 32, 33, 33', focused and exits from an exit opening 34 of the device 3 and into the target chamber 4.In the target chamber 4, the laser radiation 11 strikes the target material, in this case a tin droplet. The EUV radiation generated by the interaction between the target material and the incident laser radiation 11 can be guided via a beam guide element 41 of the target chamber 4 toward the exposure device (not shown in Fig. 7).

[0049] In the target area 40, laser radiation is backscattered and / or reflected back by the target material. This effect is illustrated in Fig. 7 by dashed arrows. To absorb this backscattered and / or reflected laser radiation, the device 3 comprises a radiation-absorbing element 35 arranged in the interior 30 with an absorption surface 101, which is arranged in the region of the inlet opening 31. The radiation-absorbing element 35 has a device for active cooling, which is designed as a cooling channel and is connected to a cooling device 37. The radiation-absorbing element 35, in particular its absorption surface 101, can be designed as described in connection with Figs. 3 to 6.

[0050] Fig. 8 shows a schematic representation of a third embodiment of a device 3 for focusing the laser radiation 11, which can also be used alternatively in the lithography system 10 according to Fig. 1. Fig. 8 also shows a part of the adjacent target chamber 4 with the target region 40. In the device 3 according to the third embodiment, laser radiation 11 enters the interior 30 of the device 3 through an inlet opening 31. To focus the laser radiation 11, a total of two focusing elements 32, 33, here two mirrors, are provided in the third embodiment, by means of which the laser radiation 11 is focused onto the target region 40 in the target chamber 4. In this respect, the laser radiation 11 is deflected by the focusing elements 32, 33, focused and exits from an exit opening 34 of the device 3 and into the target chamber 4.In the target chamber 4, the laser radiation 11 strikes the target material, in this case a tin droplet. The EUV radiation generated by the interaction between the target material and the incident laser radiation 11 can be guided via a beam guide element 41 of the target chamber 4 toward the exposure device (not shown in Fig. 8).

[0051] In the target area 40, backscattering and / or backreflection of laser radiation occurs at the target material. This effect is illustrated in Fig. 8 by dashed arrows. To absorb this backscattered and / or backreflected laser radiation, the device 3 comprises a radiation-absorbing element 35 arranged in the interior 30 with an absorption surface 101, which is arranged in the region of the outlet opening 34. The radiation-absorbing element 35 is preferably arranged such that it surrounds the outlet opening 34, in particular completely surrounds it. The radiation-absorbing element 35 has a device for active cooling, which is designed as a cooling channel and is connected to a cooling device 37. The radiation-absorbing element 35, in particular its absorption surface 101, can be designed as described in connection with Figs. 3 to 6.

[0052] Reference symbol:

[0053] 1 radiation source

[0054] 2 optical amplifiers

[0055] 3 Device for focusing the laser radiation

[0056] 4 Target chamber

[0057] 5 Exposure device

[0058] 10 Lithography system

[0059] 11 Laser radiation

[0060] 12 extreme ultraviolet radiation

[0061] 30 Interior

[0062] 31 Entrance opening

[0063] 32 Focusing element

[0064] 33 Focusing element

[0065] 34 Exit opening

[0066] 35 radiation-absorbing element

[0067] 36 Interior trim element

[0068] 37 Cooling device

[0069] 40 target area

[0070] 41 Beam guidance element

[0071] 45 radiation-absorbing element

[0072] 55 radiation-absorbing element

[0073] 100 basic bodies

[0074] 101 Absorption surface

[0075] 102 Cooling channel

[0076] ARS angle-dependent scattering

[0077] B Extension in the main plane of the absorption surface

[0078] H Extension perpendicular to the main plane of the absorption surface

[0079] 6 angles of incidence

Claims

Patent claims 1. Device for focusing laser radiation (11) onto a target area (40), in which a target material is arranged which emits extreme ultraviolet radiation (12), EUV radiation, when irradiated with the laser radiation (11), with an interior space (30) and at least one focusing element (32, 33), in particular a mirror, arranged in the interior space (30) for focusing the laser radiation (11), characterized by a radiation-absorbing element (35) arranged in the interior space (30) with an absorption surface (101) for absorbing laser radiation backscattered and / or reflected back by the target material, wherein the radiation-absorbing element (35) comprises a device for active cooling, in particular a cooling channel (102) for guiding a coolant.

2. Device according to claim 1, characterized in that the target area (40) is provided outside the interior space (30) and the device (3) comprises an exit opening (34) through which the laser radiation (11) focused by means of the at least one focusing element (32, 33) can exit the device (3) in the direction of the target area (40), wherein the radiation-absorbing element (35) is arranged in the interior space (30) in such a way that laser radiation backscattered and / or reflected back by the target material and entering through the exit opening (34) strikes the absorption surface (101) without interaction with other elements in the interior space (30).

3. Device according to one of the preceding claims, characterized in that at least one interior lining element (36) is arranged in the interior space (30), which is configured such that laser radiation backscattered and / or back-reflected by the target material and entering through the exit opening (34) strikes the absorption surface (101) after reflection by the interior lining element (36) in the interior space (30).

4. Device according to one of the preceding claims, characterized in that the radiation-absorbing element (35) has a base body (100) made of a material, wherein the absorption surface (101) is formed by a highly absorbent surface structure of the material of the base body (100).

5. Device according to claim 4, characterized in that the material is a metal, in particular aluminum.

6. Device according to claim 4 or, characterized in that the highly absorbent surface structure is formed from laser-induced periodic surface structures.

7. Device according to one of claims 4 to 6, characterized in that the highly absorbent surface structure has structures with an extension (H) perpendicular to a main extension plane of the absorption surface in the range from 10 micrometers to 15 micrometers and / or with an extension (B) in the main extension plane of the absorption surface in the range from 5 micrometers to 30 micrometers.

8. Device according to one of claims 4 to 7, characterized in that the highly absorbent surface structure is configured such that it diffusely scatters 18% to 30% of the incident laser radiation and specularly reflects 0.01% to 1% of the incident laser radiation.

9. Lithography system with a device (3) for focusing laser radiation (11) onto a target area (40), in which a target material is arranged which emits extreme ultraviolet radiation (12), EUV radiation, when irradiated with the laser radiation (11), with an interior space (30) and at least one focusing element (32, 33), in particular a mirror, arranged in the interior space (30) for focusing the laser radiation (11), characterized by a radiation-absorbing element (35, 45, 55), in particular arranged in the interior space (30), having an absorption surface (101) for absorbing laser radiation backscattered and / or reflected back by the target material, wherein the radiation-absorbing element (35, 45, 55) comprises a device for active cooling, in particular a cooling channel (102) for guiding a coolant.

10. Lithography system according to claim 9, characterized in that the radiation-absorbing element (45, 55) is arranged in a target chamber (4), in which the target area (40) is located or is arranged in an exposure device (5) which is configured to use the extreme ultraviolet radiation (12), EUV radiation, for exposure.

Images