Insert for a source chamber of an EUV radiation source

Abstract

An insert (8) for a source chamber (2) of an EUV radiation source (1) comprises one or more heat tubes (41).

Description

[0001] Insert for a source chamber of an EUV radiation source

[0002] The present patent application claims the priority of the German patent application DE 10 2024 203 896.2, the contents of which are incorporated herein by reference.

[0003] The invention relates to an insert for a source chamber of an EUV radiation source. Moreover, the invention relates to an EUV radiation source having a corresponding insert. Finally, the invention relates to an illumination system for a projection exposure apparatus, a mask inspection apparatus or a metrology system, and to a projection exposure apparatus and a metrology system.

[0004] Used radiation in the EUV range can be created in an EUV radiation source by igniting a source plasma in a source chamber of the EUV radiation source. US 2011 / 0089834 Al describes an embodiment of an EUV radiation source having an electrode plasma generation device. EP 1 774 838 Bl discloses an inductively coupled plasma source.

[0005] EUV radiation sources are used in illumination systems for projection exposure apparatuses, in particular for EUV lithography, inspection apparatuses and metrology systems. A corresponding projection exposure apparatus is known from WO 2009 / 100 856 Al, for example.

[0006] A problem addressed by the invention is that of improving an insert for a source chamber of an EUV radiation source, in particular reducing a temperature gradient in the insert.

[0007] This problem is solved by an insert according to the invention. According to an aspect of the invention, the insert comprises one or more heat tubes, in particular at least 3 heat tubes.

[0008] It may also comprise more than 3 heat tubes. With the aid of the heat tubes, it is possible to better distribute the heat in the insert and hence reduce a temperature gradient.

[0009] The insert is a carrier for an inner insert (bore) in particular. The inner insert is also referred to as a bore insert. The outer insert, which is inserted into a chamber wall of a source chamber of an EUV radiation source, is also referred to as a carrier.

[0010] Together, the carrier with the inner insert (bore insert) is also referred to as a bore.

[0011] The carrier may comprise a main body made of copper.

[0012] The bore insert may be produced from ceramics in particular.

[0013] According to an aspect, a heat pipe may serve as a heat tube.

[0014] This heat pipe may conduct a liquid. The liquid may evaporate should an evaporation temperature be exceeded. It may absorb heat from the insert in the process. The evaporated liquid may recondense in a colder region and transmit heat to the insert in the process.

[0015] The heat tube, in particular the heat pipe, may comprise a cavity. This may be a pressure-tightly closed-off cavity in particular. In particular, there may be a reduced pressure within the cavity. In particular, the ambient pressure within the cavity may range from 1 mbar to 50 mbar.

[0016] A granulate may be arranged in the cavity. In particular, the granulate may comprise copper. For example, powdered copper or a copper compound may serve as a granulate. The granulate may render the thermal conductivity more independent of the orientation of the heat tube in space.

[0017] In particular, the heat pipes may be arranged completely within the bore, in particular integrated in the bore. To produce a heat pipe integrated into the bore, a bore insert may be introduced into the bore. Copper powder or another granulate, in particular a copper-containing granulate, may be filled into the bore insert. Thereupon, the bore with the powder or granulate may be sintered. This may be followed by an evacuation. A liquid may be added subsequently, and the bore insert may be closed off.

[0018] The liquid may be supplied in the evacuated state. Subsequently, the heat pipe may be closed off in gas-tight, in particular pressure-tight, fashion.

[0019] According to an aspect, the heat tubes may be arranged in the insert in a direction parallel to a passage channel. In particular, they may be arranged in parallel with the longitudinal direction of the passage channel. In general, they have at least one component in this direction.

[0020] The heat tubes may also be arranged obliquely to the longitudinal direction. As a result, the space available in the insert can be better utilized.

[0021] Especially in a region in which the insert has a smaller external diameter, the heat tubes may be arranged closer to a central centre axis, in particular closer together, than in a region in which the insert has a larger external diameter. For example, the heat tubes may be arranged along the surface of a conical region.

[0022] The length of the heat tubes may be increased as a result. This may lead to improved heat transport in the insert.

[0023] According to a further aspect, the heat tubes may be arranged in bore inserts in the insert. In particular, they may be arranged form-fittingly in cutouts in the insert. By preference, they are fitted into the insert, in particular pressed into the insert.

[0024] This leads to a particularly advantageous heat transfer from the insert to the heat tubes.

[0025] According to a further aspect, at least sections of the heat tubes may be surrounded by an elastic contact element.

[0026] This may further improve the heat transfer.

[0027] For example, the contact element may be made of indium.

[0028] In particular, the heat tubes may be fully surrounded by an appropriate contact element.

[0029] This may further improve the heat transfer. In particular, different thermal expansions of the heat tubes and the insert may be compensated for with the aid of an elastic contact element. According to a further aspect, the heat tubes may be arranged in closed-off cavities in the insert. A closure element may serve to close the cavities. The closure element may be screwed, pressed or wedged into the open end of the cavity.

[0030] By preference, the heat tubes are interchangeably arranged in the insert.

[0031] According to a further aspect, the heat tubes may be arranged in sealed cavities in the insert. This can ensure that the heat absorbed from the insert is emitted back to the insert.

[0032] In particular, a sealed cavity is understood to mean that the cavity is closed off to the outside in airtight fashion, in particular in vacuum-tight fashion.

[0033] According to a further aspect, the heat tubes are arranged in an outer half of the insert in terms of the longitudinal direction. However, they may extend in the inner half of the insert in terms of the longitudinal direction.

[0034] In particular, the outer half is the side of the insert distant from the source chamber. In particular, this is the colder side of the insert during the operation of the radiation source. This allows particularly good use to be made of the installation space available in the insert.

[0035] The heat tubes may have a length that is at least 30%, in particular at least 50% and in particular at least 70% of the overall extent of the insert in the longitudinal direction. A greater extent of the heat tubes leads to better heat distribution. A shorter embodiment of the heat tubes facilitates the arrangement thereof in the insert.

[0036] An insert according to the description above leads to an improvement of an EUV radiation source. In particular, the longevity of the radiation source may be improved with the aid of an insert according to the invention. In particular, this also allows a reduction in the costs associated with operation of the radiation source.

[0037] The radiation source may preferably be used in an illumination system for a projection exposure apparatus, a mask inspection apparatus or a metrology system.

[0038] The insert according to the invention thus leads to an improvement in such apparatuses and systems.

[0039] Further advantages and details will become apparent from the description of an exemplary embodiment on the basis of the figures, in which:

[0040] Fig. 1 shows a schematic sectional drawing of an EUV radiation source and

[0041] Fig. 2 shows a partially schematic sectional illustration through detail II from a source chamber of the EUV radiation source in the region of a passage channel.

[0042] Figure 1 illustrates a schematic sectional drawing of an exemplary embodiment of an EUV radiation source 1. Figure 2 shows a portion of same. The overall structure of the EUV radiation source 1 is purely exemplary and should not be construed as restrictive. In particular, the arrangement of the access / service openings of the radiation source may deviate from the depicted embodiment. The beam direction of the EUV radiation source 1 with respect to the remaining optics unit and the installation direction of the insert in the source chamber wall are independent of one another and may also be reversed.

[0043] The EUV radiation source 1 is part of an illumination system (not depicted explicitly) of a projection exposure apparatus. For fundamental details, reference is made by way of example to DE 10 2017 212 352 Al, which is hereby fully incorporated in the present application as part thereof.

[0044] The EUV radiation source 1 comprises a two-part source chamber 2 with an upper chamber part 3 and a lower chamber part 4. A centre plate 5 is located between the upper chamber part 3 and the lower chamber part 4. The centre plate 5 forms a chamber wall of the source chamber 2, in particular of the upper chamber part 3.

[0045] The upper chamber part 3 is also referred to as source chamber below.

[0046] The centre plate 5 has off-centred openings 6 and a central opening 7.

[0047] The centre plate 5 may be formed in multiple parts. In particular it may comprise a plate 18 which faces the source chamber 2 and to which a high voltage can be applied and, separately therefrom, an outer base plate 19.

[0048] A first insert 8 is inserted into the central opening 7. The first insert 8 forms an outer insert. The first insert 8 is also referred to as "carrier". It comprises a first passage channel 10 that extends in a longitudinal direction 9.

[0049] A second insert 11 is arranged in the first passage channel 10. The second insert 11 comprises a second passage channel 12 that extends in the longitudinal direction 9. The carrier with the inner insert 11 is sometimes also referred to as a "bore" (bore insert).

[0050] The first passage channel 10 is also referred to as the outer passage channel. The second passage channel 12 is also referred to as the inner passage channel. The two passage channels 10, 12 have a common longitudinal axis 13 that extends in the longitudinal direction 9.

[0051] During operation of the EUV radiation source 1, the off-centred openings 6 and the central opening 7, in particular the passage channels 10, 12, serve for the passage of a source plasma ignited in the chamber parts 3, 4.

[0052] The EUV radiation source 1 is an induction plasma current generator.

[0053] Constituent parts of an illumination optics unit (not depicted explicitly) of a projection exposure apparatus, of a mask inspection apparatus or of a metrology system are connected to the EUV radiation source 1. The illumination optics unit is a constituent part of an illumination system in particular. The illumination system may comprise one or more mirrors in particular, in particular one or more facet mirrors. The illumination optics unit serves in particular for transferring illumination radiation generated by the EUV radiation source 1 to a mask with structures to be imaged. The mask is also referred to as reticle. Figure 1 likewise schematically depicts a maintenance region 14 adjacent to the EUV radiation source 1. An interface having a dome stop 15 is provided between the maintenance region 14 and the EUV radiation source 1. For details, reference is made to DE 10 2017 212 352 Al, in particular to Figure 23 and the associated description.

[0054] With the aid of a maintenance hatch 16, the maintenance region 14 is seal- able so as to be vacuum-tight with respect to an outer region 17. The maintenance hatch 16 may be opened for maintenance purposes. In the opened state of the maintenance hatch 16, the maintenance region 14, and consequently the EUV radiation source 1, can be accessed. In particular, it is possible for the two inserts 8, 11 to be removed from the EUV radiation source 1 through the maintenance region 14, for example in order to exchange them.

[0055] Details of the first, outer insert (carrier) 8 and in particular of the second, inner insert (bore) 11 are described below with reference to the figure. Corresponding embodiments of the inserts 8, 11 are advantageous, independently of the remaining structural details of the EUV radiation source 1.

[0056] The outer, first insert 8 is connected, for example via a plurality of screws 30, to the plate 18. In particular, it has an electrical contact 21 to the plate 18. An O-ring may be provided in the connection region between the first insert 8 and the plate 18.

[0057] The first insert 8 is connected, for example via a plurality of screws 30, to the base plate 19. In particular, it has an electrical contact 23 to the base plate 19. An O-ring may be provided in the contact region between the first insert 8 and the base plate 19. The inner, second insert 11 lies circumferentially against the inner circumference of the first passage channel 10. In particular, it is arranged substantially without play in the first passage channel 10. However, it may be arranged in the first passage channel 10 so as to be displaceable in the longitudinal direction.

[0058] The inner insert 11 may be thermally shrunk in the passage channel 10. The inner insert 11 may also be soldered, welded or adhesively bonded to the passage channel 10. In particular, it may also be form-fittingly connected and / or integrally bonded to the passage channel 10.

[0059] In the variant depicted in Figure 2, the inner insert 11 comprises a plurality of portions. In particular, it comprises a first, inner portion 26 and a second, middle portion 27. The portions 26, 27, 28 follow one another in the longitudinal direction 9. In particular, they may adjoin one another in the longitudinal direction 9.

[0060] The inner portion 26 and the middle portion 27 may have substantially constant external diameters over their extent in the longitudinal direction 9. In particular, they may have identical external diameters.

[0061] The inner portion 26 has a sleeve-like form. In particular, it has a substantially hollow cylindrical form. However, it may be chamfered at the ends.

[0062] The middle portion 27 has a smaller internal diameter dm than the inner portion 26 with an internal diameter di, dm < di. Cutouts, in particular in the form of bore inserts 40, may be provided in the insert 8. The bore inserts 40 serve to accommodate heat tubes, in particular in the form of heat pipes.

[0063] The bore inserts may extend parallel to the longitudinal direction 9. They may also be arranged obliquely within the insert 8.

[0064] The heat pipes 41 are preferably form-fittingly arranged in the bore inserts 40.

[0065] To improve the heat transfer from the insert 8 into the heat pipes 41, the heat pipes 41 may be surrounded by one or more elastic contact elements 42. The contact elements may also be dispensed with.

[0066] The receptacle for the heat pipes 41 may be sealed at its outer, open end by means of a sealing element 43.

[0067] Solder, in particular, may serve as sealing element 43. A liquid metal, in particular an indium gallium alloy, or a thermally conductive adhesive, in particular based on epoxy, may also serve as sealing element.

[0068] The heat pipes 41 may also be securely integrated in the insert 8.

[0069] The sealing element 43 may also be screwed or pressed into the bore insert 40 or wedged into the latter. This may facilitate an exchange of the heat pipes.

Claims

Claims:

1. Insert (8) for a source chamber (2) of an EUV radiation source (1) having one or more heat tubes.

2. Insert (8) according to Claim 1, characterized in that a heat pipe (41) serves as a heat tube.

3. Insert (8) according to either of the preceding claims, characterized in that a cavity pressure-tightly closed-off to the outside and having a pressure therein of the order of no more than 500 mbar is formed in the heat tube.

4. Insert (8) according to any of the preceding claims, characterized in that a granulate is arranged in the heat tube.

5. Insert (8) according to any of the preceding claims, characterized in that the heat tubes are arranged in the insert (8) in a direction parallel to a passage channel (10).

6. Insert (8) according to any of the preceding claims, characterized in that the heat tubes are arranged in bore inserts (40) in the insert.

7. Insert (8) according to any of the preceding claims, characterized in that at least sections of the heat tubes are surrounded by an elastic contact element (42).

8. Insert (8) according to any of the preceding claims, characterized in that the heat tubes are arranged in closed-off cavities in the insert (8).

9. Insert (8) according to any of the preceding claims, characterized in that the heat tubes are arranged in sealed cavities in the insert (8).

10. Insert (8) according to any of the preceding claims, characterized in that the heat tubes are arranged in an outer half of the insert (8) in terms of the longitudinal direction (9).

11. Method for producing an insert (8) according to any of the preceding claims, comprising the following steps: providing an insert (8) for a source chamber (2) of an EUV radiation source (1), introducing one or more bore inserts into the insert, at least partially filling the bore insert with a granulate, sintering the insert with the granulate, at least partially evacuating the cavity formed by the bore insert, introducing a liquid into the cavity, gas-tightly sealing the cavity.

12. EUV radiation source (1), comprising12.1 a source chamber (2) having12.1.1 a chamber wall comprising at least one chamber opening,12.1.2 an insert (8) inserted into the chamber opening,12.2 wherein the insert (8) is formed according to any of Claims 113. Illumination system for a projection exposure apparatus, a mask inspection apparatus or a metrology system, having an EUV radiation source (1) with an insert (8) according to any of Claims 1 to 10.

14. Projection exposure apparatus for EUV lithography, comprising14.1 an illumination system according to Claim 13 for illuminating a reticle that is arranged in an object field, and14.2 a projection optics unit for imaging structures of the reticle onto a wafer that is arranged in an image field.

15. Metrology system for inspecting a mask for EUV lithography, having an illumination system according to Claim 13.

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