METHOD FOR BENDING HYDROFORMED COOLING DEVICES AND BENT HYDROFORMED COOLING DEVICES

Abstract

A method for bending a cooling device for microlithographic projection exposure apparatuses includes: providing an unbent cooling device that includes a cavity; filling the cavity with a liquid cryogenic medium at least in a region of the cooling device that is to be bent; cooling the cooling device such that the medium present in the cavity cools below its melting temperature and thereby at least partially solidifies; and bending the cooling device such that the at least partially solidified medium prevents the cavity from closing during bending.

Claims

1. A method, comprising: a) disposing a liquid cryogenic medium in a cavity of a cooling device; b) after a), cooling the cooling device to at least partially solidify the cryogenic medium present in the cavity; and c) after b), bending the cooling device so that the at least partially solidified cryogenic medium prevents the cavity from closing during bending.

2. The method of claim 1, further comprising, before a), using hydroforming to provide the cavity.

3. The method of claim 1, further comprising, during c), maintaining a bending radius of less than approximately 100 millimeters.

4. The method of claim 1, further comprising, during c), maintaining a bending radius of less than approximately 50 millimeters.

5. The method of claim 1, wherein the cryogenic medium comprises water and at least one member selected from the group consisting of a salt and a surfactant.

6. The method of claim 1, wherein the cryogenic medium comprises water and secondary alcohol ethoxylate.

7. The method of claim 6, wherein the cryogenic medium further comprises a salt.

8. The method of claim 6, wherein the cryogenic medium further comprises at least one member selected from the group consisting of potassium phosphate, sodium silicate and sodium salt.

9. The method of claim 1, wherein the cryogenic medium comprises water and a salt.

10. The method of claim 1, wherein the cryogenic medium comprises water and at least one member selected from the group consisting of potassium phosphate, sodium silicate and sodium salt.

11. The method of claim 1, wherein the cryogenic medium comprises at least one member selected from the group consisting of a solution comprising water and a mixture comprising water.

12. The method of claim 1, wherein b) comprises at least partially disposing the cooling device in liquefied gas.

13. The method of claim 1, wherein b) comprises at least partially disposing the cooling device in liquid nitrogen.

14. The method of claim 1, further comprising, after c): heating the cooling device to liquefy the cryogenic medium; and removing the cryogenic medium from the cavity.

15. The method of claim 1, wherein a) comprises filling the cavity of the cooling device with the liquid cryogenic medium,

16. The method of claim 1, further comprising, after c), using the cooling device in a microlithographic projection exposure apparatus.

17. An apparatus, comprising: an illumination device comprising a plurality of optical elements; a projection lens comprising a second plurality of optical elements; and a cooling device comprising a first sheet and a second sheet different from the first sheet, wherein: the illumination device is configured to illuminate an object in an object plane of the projection lens; the projection lens is configured to image the illuminated object onto a light-sensitive material in an image plane of the projection lens; the cooling device comprises a cavity between the first and second sheets; the cavity has a bending radius of less than approximately 100 millimeters; and the cooling device is configured to cool at least one optical element selected from the group consisting of the first plurality of optical elements and the second plurality of optical elements.

18. The apparatus of claim 17, wherein the at least one optical element comprises a mirror.

19. The apparatus of claim 17, wherein: during use of the apparatus, light follows a path from a light source to the object via the illumination device and from the object to the light-sensitive material via the projection lens; and the first sheet comprises ribbing facing the path of the light.

20. The apparatus of claim 19, wherein the first sheet is thicker than the second sheet.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0029] Various exemplary embodiments are explained in more detail below with reference to the figures. The figures and the relative sizes of the elements shown in the figures in relation to one another should not be regarded as to scale. Rather, individual elements may be shown exaggerated in size or reduced in size to allow them to be represented better and for the sake of better understanding.

[0030] FIG. 1 shows a schematic representation of a detail of an unbent cooling device in a sectional view.

[0031] FIG. 2 shows a schematic representation of an unbent cooling device in plan view.

[0032] FIG. 3 shows a schematic representation of an unbent cooling device in plan view.

[0033] FIG. 4 shows a schematic representation of a detail of a bent cooling device in a sectional view, with a closed cavity in the region of the bending.

[0034] FIG. 5 shows a schematic representation of a detail of a bent cooling device according to the disclosure in a sectional view, with a cavity in the region of the bending, the cavity being filled with a solidified cryogenic medium.

[0035] FIG. 6 shows a schematic representation of a detail of a bent cooling device according to the disclosure in a sectional view, with a cavity in the region of the bending, the cavity having been freed of the cryogenic medium.

[0036] FIG. 7 shows a further schematic representation of a detail of a bent cooling device according to the disclosure in a sectional view, with a cavity in the region of the bending, the cavity having been freed of the cryogenic medium.

[0037] FIG. 8 shows the method steps for producing a bent cooling device according to the disclosure.

[0038] FIG. 9 shows an EUV system which includes a number of bent cooling devices according to the disclosure.

[0039] FIG. 10 shows a DUV system which can include bent cooling devices according to the disclosure.

DISCLOSURE OF EXEMPLARY EMBODIMENTS

[0040] FIGS. 1, 2 and 3 show schematic representations of substantially unbent cooling devices 100 that were known. These figures have already been described in more detail in the introductory part of the description.

[0041] FIG. 4 shows a schematic representation of a detail of a bent cooling device 100, the cooling device 100 not having been filled with a cryogenic medium 110 before the bending. The bending radius 114 lies in this case in the range of 100 mm to 5 mm. The solid lines show the contours of the cooling device 100 after the bending. The dashed lines show the contours of the cooling device 100 before the bending. It can be seen that the cavity 108 has become at least partially closed in the bent region. The cooling medium, optionally cooling water, which is not shown in the figures, cannot flow any longer in this closed region.

[0042] FIG. 5 shows a schematic representation of a detail of a bent cooling device 100, the cooling device 100 having been filled with a cryogenic medium 110 according to the disclosure before the bending. The cryogenic medium 110 has solidified and keeps the cavity 108 open during the bending, even in the bent region. The bending radius 114 lies in this case in the range of 100 mm to 5 mm.

[0043] FIG. 6 shows a schematic representation of a detail of the bent cooling device 100 from FIG. 5. In FIG. 6, the cryogenic medium 110 has been removed. The cavity 108 is open, even in the bent region. The bending radius 114 lies in this case in the range of 100 mm to 5 mm.

[0044] FIG. 7 shows a schematic representation of a detail of the bent cooling device 100 from FIG. 6. In addition to FIG. 6, in FIG. 7 the side of the thicker sheet 104 that is facing a beam path in the microlithographic projection exposure apparatus is provided with a ribbing 112.

[0045] FIG. 8 shows the method for producing a cooling device 100 according to the disclosure.

[0046] The first step S1 involves providing the substantially unbent cooling device 100, including at least one cavity 108. The at least one cavity 108 was produced by hydroforming. This unbent cooling device 100 is shown in FIGS. 1, 2 and 3, which have been described in more detail in the introductory part of the description.

[0047] In the second step S2, the at least one cavity 108 is filled with a liquid cryogenic medium 110, at least in a region to be bent of the cooling device 100.

[0048] In the third step S3, the cooling device 100 is cooled down such that the cryogenic medium 110 present in the cavity 108 cools below its melting temperature and thereby at least partially solidifies. The cryogenic medium 110 is a mixture of water and at least one active component and/or a solution of at least one active component in water, the active component including, for example, at least one surfactant, such as secondary alcohol ethoxylate, and/or at least one salt, such as potassium phosphate, sodium silicate or sodium salt. The cooling down of the cooling device 100 is performed, for example, by immersion in liquefied gas, such as liquid nitrogen.

[0049] In the fourth step S4, the cooling device 100 is bent. The at least partially solidified cryogenic medium 110 prevents closing of the cavity 108 during the bending. During the bending, a bending radius 114 of less than 100 mm, such as less than 50 mm, is maintained. See FIG. 5 in this respect.

[0050] In the fifth step S5, the bent cooling device 100 filled with the at least partially solidified cryogenic medium 110 is heated such that the cryogenic medium 110 is liquefied again and the liquefied cryogenic medium 100 can be removed from the at least one cavity 108 at least almost entirely without leaving any behind. FIGS. 6 and 7 show the end result.

[0051] According to FIG. 9, an illumination device in a microlithographic projection exposure apparatus 300 designed for EUV includes a field facet mirror 303 and a pupil facet mirror 304. The light from a light source unit including a plasma light source 301 and a collector mirror 302 is directed onto the field facet mirror 303. A first telescope mirror 305 and a second telescope mirror 306 are arranged in the light path downstream of the pupil facet mirror 304. A grazing incidence mirror 307, which directs the radiation that is incident on it onto an object field in the object plane of a projection lens including six mirrors 351-356, is arranged downstream in the light path. Arranged on a mask stage 320 at the location of the object field is a reflective structure-bearing mask 321, an image of which is projected with the aid of the projection lens into an image plane in which a substrate 361 coated with a light-sensitive layer (photoresist) is on a wafer stage 360. The force frame 380, which substantially carries the mirrors of the projection lens, and the sensor frame 370, which substantially serves as a reference for the position of the mirrors of the projection lens, are shown roughly schematically. Some bent pillow plates 100, which substantially enclose the EUV beam path, are shown by way of example. The bending of the pillow plates 100 is not shown in FIG. 9 for reasons of overall clarity.

[0052] FIG. 10 shows a schematic view of a DUV projection exposure apparatus 400, which includes a beam shaping and illumination device 402 and a projection lens 404. In this case, DUV stands for “deep ultraviolet” and denotes a wavelength of the working light of between 30 and 250 nm.

[0053] The DUV projection exposure apparatus 400 includes a DUV light source 406. For example, an ArF excimer laser that emits radiation 408 in the DUV range at for example 193 nm, may be provided as the DUV light source 406.

[0054] The beam shaping and illumination device 402 shown in FIG. 10 directs the DUV radiation 408 onto a photomask 420. The photomask 420 is formed as a transmissive optical element and may be arranged outside the beam shaping and illumination device 402 and the projection lens 404. The photomask 420 has a structure of which a reduced image is projected onto a wafer 424 or the like via the projection lens 404.

[0055] The projection lens 404 has a number of lens elements 428, 440 and/or mirrors 430 for projecting an image of the photomask 420 onto the wafer 424. In this case, individual lens elements 428, 440 and/or mirrors 430 of the projection lens 404 may be arranged symmetrically in relation to the optical axis 426 of the projection lens 404. It should be noted that the number of lens elements and mirrors of the DUV projection exposure apparatus 400 is not restricted to the number shown. More or fewer lens elements and/or mirrors may also be provided. Furthermore, the mirrors are generally curved on their front side for beam shaping.

[0056] An air gap between the last lens element 440 and the wafer 424 may be replaced by a liquid medium 432 which has a refractive index of >1. The liquid medium 432 may be for example high-purity water. Such a construction is also referred to as immersion lithography and has an increased photolithographic resolution.

[0057] Even though the disclosure has been described on the basis of specific embodiments, numerous variations and alternative embodiments will be apparent to a person skilled in the art, for example through combination and/or exchange of features of individual embodiments. Accordingly, it goes without saying for a person skilled in the art that such variations and alternative embodiments are also included by the present disclosure, and the scope of the disclosure is only restricted as provided by the appended patent claims and the equivalents thereof.

LIST OF REFERENCE SIGNS

[0058] 100 Particularly plate-shaped cooling device (=pillow plate) [0059] 102 Thinner sheet [0060] 104 Thicker sheet [0061] 106 Weld seam [0062] 108 Cavity (=cooling channel) [0063] 110 Cryogenic medium [0064] 112 Ribbing [0065] 114 Bending radius [0066] 300 EUV projection exposure apparatus (=EUV system) [0067] 301 to 360 Parts of the EUV projection exposure apparatus [0068] 370 Sensor frame [0069] 380 Force frame [0070] 400 DUV projection exposure apparatus (=DUV system) [0071] 402 to 440 Parts of the DUV projection exposure apparatus