Application for a source chamber of an EUV radiation source

Abstract

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

Description

[0001] The invention relates to an insert for a source chamber of an EUV radiation source. The invention also relates to an EUV radiation source with a corresponding insert. Finally, the invention relates to an illumination system for a projection exposure system, a mask inspection system, or a metrology system, as well as a projection exposure system and a metrology system.

[0002] In an EUV radiation source, useful radiation in the EUV range can be generated by igniting a source plasma in a source chamber of the EUV radiation source. US 2011 / 0089834 A1 describes an embodiment of an EUV radiation source with an electrode plasma generation device. An inductively coupled plasma source is known from EP 1 774 838 B1.

[0003] EUV radiation sources are used in lighting systems for projection exposure systems, particularly for EUV lithography, inspection systems, and metrology systems. A corresponding projection exposure system is known, for example, from WO 2009 / 100 856 A1.

[0004] DE 10 2020 206 876 A1 discloses an EUV radiation source with a multi-part insert in a chamber wall of a source chamber. DE 10 2021 207 565 B3 discloses a further embodiment of an EUV radiation source with an insert in a wall of a source chamber.

[0005] One object of the invention is to improve an insert for a source chamber of an EUV radiation source, in particular to reduce a temperature gradient in the insert.

[0006] This problem is solved by an insert according to the invention.

[0007] According to one aspect of the invention, the insert has one or more, in particular at least 3, heat pipes.

[0008] It can also have more than 3 heat pipes. The heat pipes allow for better heat distribution during operation, thus reducing temperature gradients.

[0009] The component in question is, in particular, a carrier for an inner insert (bore). 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 and the inner insert (bore insert) are also referred to as the bore.

[0011] The carrier can have a base body made of copper.

[0012] The bore insert can be made of ceramic, in particular.

[0013] From one perspective, a heat pipe can serve as a heat pipe.

[0014] This heat pipe can carry a liquid. The liquid can evaporate when its evaporation temperature is exceeded. In doing so, it can absorb heat from the component. The evaporated liquid can then condense again in a cooler area, releasing heat back to the component.

[0015] The heat pipe, in particular the heat tube, may contain a cavity. This cavity may be, in particular, a pressure-tight sealed cavity. A reduced pressure may prevail within the cavity. The ambient pressure within the cavity may be, in particular, in the range of 1 mbar to 50 mbar.

[0016] A granulate can be arranged within the cavity. This granulate can, in particular, contain copper. For example, powdered copper or a copper compound can serve as the granulate. The granulate allows the thermal conductivity to be made less dependent on the orientation of the heat pipe in space.

[0017] The heat pipes can be arranged entirely within the bore, and in particular, integrated into the bore. To produce a heat pipe integrated into the bore, a bore can be drilled into the bore. Copper powder or another granulate, especially copper-containing granulate, can be filled into the bore. The bore can then be sintered with the powder or granulate. Subsequently, evacuation can take place. Then, a liquid can be added and the bore sealed.

[0018] The liquid can be added once the system is evacuated. The heat pipe can then be sealed gas-tight, and in particular pressure-tight.

[0019] According to one aspect, the heat pipes can be arranged parallel to a passageway in the installation. In particular, they can be arranged parallel to the longitudinal direction of the passageway. They generally have at least one component in this direction.

[0020] The heat pipes can also be arranged at an angle to the longitudinal direction. This allows for better use of the available space during operation.

[0021] The heat pipes can be arranged closer to a central axis, and especially closer together, particularly in an area where the insert has a smaller outer diameter, than in an area where the insert has a larger outer diameter. For example, the heat pipes can be arranged along the surface of a conical area.

[0022] This allows the length of the heat pipes to be increased. This can lead to improved heat transfer during operation.

[0023] According to another aspect, the heat pipes can be arranged in bores within the insert. In particular, they can be positively fitted into recesses in the insert. They are preferably fitted into the insert, especially pressed in.

[0024] This results in a particularly advantageous heat transfer from the insert to the heat pipes.

[0025] According to another aspect, the heat pipes can be surrounded, at least in sections, by an elastic contact element.

[0026] This can further improve heat transfer.

[0027] The contact element can be made of indium, for example.

[0028] The heat pipes can, in particular, be completely surrounded by a corresponding contact element.

[0029] This further improves heat transfer. In particular, the use of an elastic contact element allows for compensation of differing thermal expansion rates between the heat pipes and the insert.

[0030] Another aspect is that the heat pipes can be installed in enclosed cavities. A sealing element can be used to close these cavities. This sealing element can be screwed, pressed, or clamped into the open end of the cavity.

[0031] Preferably, the heat pipes are arranged in a replaceable manner during use.

[0032] Another aspect is that the heat pipes can be arranged in sealed cavities within the insert. This ensures that they transfer the heat absorbed by the insert back to the insert.

[0033] A sealed cavity is understood to mean, in particular, that the cavity is sealed airtight, especially vacuum-tight, to the outside.

[0034] According to another aspect, the heat pipes are arranged in the outer longitudinal half of the insert. However, they can extend into the inner longitudinal half of the insert.

[0035] The outer half refers specifically to the side of the insert facing away from the source chamber. This is also the colder side of the insert during operation of the radiation source. This allows for particularly efficient use of the available installation space within the insert.

[0036] The heat pipes can have a length that is at least 30%, in particular at least 50%, in particular at least 70%, of the total longitudinal extent of the insert.

[0037] A greater length of the heat pipes leads to better heat distribution. Shorter heat pipes facilitate their installation.

[0038] An insert according to the preceding description leads to an improvement of an EUV radiation source. In particular, the lifespan of the radiation source can be improved with the aid of an insert according to the invention. This also allows for a reduction in the operating costs of the radiation source.

[0039] The radiation source can preferably be used in a lighting system for a projection exposure system, a mask inspection system or a metrology system.

[0040] The application according to the invention thus leads to an improvement of such plants and systems.

[0041] Further advantages and details will become apparent from the description of an exemplary embodiment with reference to the figures. These show: Fig. 1 a schematic sectional drawing of an EUV radiation source and Fig. 2 a partially schematic sectional view through section II from a source chamber of the EUV radiation source in the area of ​​a passage channel.

[0042] In Fig. Figure 1 shows a schematic sectional drawing of an exemplary embodiment of an EUV radiation source 1. Fig. Figure 2 shows a section of the same. The overall setup of the EUV radiation source 1 is merely exemplary and not intended to be restrictive to Figure 5. In particular, the arrangement of the access / maintenance openings of the radiation source may differ from the depicted design. The beam direction of the EUV radiation source 1 relative to the rest of the optics and the installation direction of the insert in the source chamber wall are independent of each other and can also be reversed.

[0043] The EUV radiation source 1 is part of an illumination system of a projection exposure system, which is not explicitly shown. For fundamental details, reference is made by way of example to DE 10 2017 212 352 A1, which is hereby fully integrated into the present application.

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

[0045] In the following, the upper chamber part 3 will also be referred to as the source chamber.

[0046] The central plate 5 has eccentric openings 6 and a central opening 7.

[0047] The central plate 5 can be made up of multiple parts. In particular, it can have a plate 18 facing the source chamber 2, which can be subjected to high voltage, and a separate 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 the "carrier". It has a first passage channel 10 extending in a longitudinal direction 9.

[0049] A second insert 11 is arranged in the first passage channel 10. The second insert 11 has a second passage channel 12 extending in the longitudinal direction 9. The support with the inner insert 11 is sometimes also referred to as a "bore".

[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 extending in the longitudinal direction 9.

[0051] In the operation of the EUV radiation source 1, the eccentric 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] EUV radiation source 1 is an induction plasma current generator.

[0053] The EUV radiation source 1 is connected to components of an illumination optics system (not explicitly shown) of a projection exposure system, a mask inspection system, or a metrology system. The illumination optics are, in particular, a component of an illumination system. The illumination system may, in particular, comprise one or more mirrors, especially one or more faceted mirrors. The illumination optics serve, in particular, to direct the illumination radiation generated by the EUV radiation source 1 to a mask containing structures to be imaged. The mask is also referred to as a reticulum.

[0054] Also shown schematically is in the Fig. 1. A maintenance area 14 adjoins the EUV radiation source 1. An interface with a dome aperture 15 is provided between the maintenance area 14 and the EUV radiation source 1. For details, refer to DE 10 2017 212 352 A1, in particular. Fig. 23 and related description, referenced.

[0055] Maintenance area 14 can be sealed vacuum-tight against an external area 17 by means of a maintenance hatch 16. The maintenance hatch 16 can be opened for maintenance work. When the maintenance hatch 16 is open, access to maintenance area 14 and thus to the EUV radiation source 1 is possible. In particular, it is possible to remove the two inserts 8 and 11 from the EUV radiation source 1 through maintenance area 14, for example, to replace them.

[0056] The following section describes, with reference to the figure, details of the first, outer insert (carrier) 8 and, in particular, the second, inner insert (bore) 11. Corresponding designs of the inserts 8 and 11 are advantageous regardless of the other design details of the EUV radiation source 1.

[0057] The outer, first insert 8 is connected to the plate 18, for example, by several screws 30. It has, in particular, an electrical contact 21 with the plate 18. An O-ring may be provided in the connection area between the first insert 8 and the plate 18.

[0058] The first insert 8 is connected to the base plate 19, for example, by a plurality of screws 30. It has, in particular, an electrical contact 23 with the base plate 19. An O-ring may be provided in the contact area between the first insert 8 and the base plate 19.

[0059] The inner, second insert 11 rests circumferentially against the inner circumference of the first passage channel 10. It is arranged in the first passage channel 10 with virtually no play. However, it can be arranged to be displaceable longitudinally within the first passage channel 10.

[0060] The inner insert 11 can be thermally shrunk into the passage channel 10. The inner insert 11 can also be soldered, welded, or bonded to the passage channel 10. In particular, it can be positively and / or materially bonded to the passage channel 10.

[0061] During the Fig. In the variant shown in Figure 2, the inner insert 11 has several sections. In particular, it has a first, inner section 26 and a second, middle section 27. Sections 26, 27, and 28 follow one another in the longitudinal direction 9. They can, in particular, be adjacent to each other in the longitudinal direction 9.

[0062] The inner section 26 and the middle section 27 can have substantially constant outer diameters along their longitudinal extent 9. In particular, they can have identical outer diameters.

[0063] The inner section 26 is sleeve-shaped. In particular, it is essentially hollow and cylindrical. However, it may have chamfers at its ends.

[0064] The middle section 27 has a smaller inner diameter dm than the inner section 26 with inner diameter di, dm < di.

[0065] Insert 8 may include recesses, in particular in the form of bores 40. The bores 40 serve to accommodate heat tubes, in particular in the form of heat pipes.

[0066] The bores can extend parallel to the longitudinal direction 9. They can also be arranged obliquely in the insert 8.

[0067] The heat pipes 41 are preferably arranged in a form-fitting manner in the bores 40.

[0068] To improve heat transfer from the insert 8 to the heat pipes 41, the heat pipes 41 can be surrounded by one or more elastic contact elements 42. The contact elements can also be omitted.

[0069] The receptacle for the heat pipes 41 can be sealed at its outer, open end by means of a sealing element 43.

[0070] Solder can serve as a sealing element 43. A liquid metal, in particular an indium-gallium alloy, or a thermally conductive adhesive, in particular epoxy-based, can also serve as a sealing element.

[0071] The heatpipes 41 can also be permanently integrated into the application 8.

[0072] The sealing element 43 can also be screwed, pressed, or clamped into the bore 40. This can facilitate the replacement of the heat pipes.

Claims

[1] Insert (8) for a source chamber (2) of an EUV radiation source (1) with one or more heat tubes. [2] Use (8) according to claim 1, characterized by , that a heat pipe (41) serves as the heat pipe. [3] Use (8) according to any of the preceding claims, characterized by , that a pressure-tight cavity sealed to the outside is formed in the heat pipe, in which a pressure of at most 500 mbar prevails. [4] Use (8) according to any one of the preceding claims, characterized by that a granulate is arranged in the heat pipe. [5] Use (8) according to any of the preceding claims, characterized by , that the heat pipes are arranged in a direction parallel to a passage channel (10) in the insert (8). [6] Use (8) according to any one of the preceding claims, characterized by , that the heat pipes are arranged in boreholes (40) in use. [7] Use (8) according to any of the preceding claims, characterized by , that the heat pipes are at least partially surrounded by an elastic contact element (42). [8] Use (8) according to any one of the preceding claims, characterized by , that the heat pipes are arranged in sealed cavities in the insert (8). [9] Use (8) according to any of the preceding claims, characterized by , that the heat pipes are arranged in sealed cavities in the insert (8). [10] Use (8) according to any of the preceding claims, characterized by , that the heat pipes are arranged in an outer half of the insert (8) in the longitudinal direction (9). [11] A method for producing an insert (8) according to any one of the preceding claims comprising the following steps: - Providing an insert (8) for a source chamber (2) of an EUV radiation source (1), - Drilling one or more holes into the insert, - at least partially filling the borehole with granules, - Sintering of the insert with the granules, - at least partial evacuation of the cavity formed by the borehole, - Introducing a liquid into the cavity, - gas-tight sealing of the cavity. [12] having an EUV radiation source (1) 12.

1. a source chamber (2) with 12.1.

1. a chamber wall having at least one chamber opening, 12.1.

2. an insert placed into the chamber opening (8), 12.

2. wherein the insert (8) is configured according to any one of claims 1 to 10. [13] Lighting system for a projection exposure system, a mask inspection system or a metrology system comprising an EUV radiation source (1) with an insert (8) according to any one of claims 1 to 10. [14] Featuring a projection exposure system for EUV lithography 14.

1. a lighting system according to claim 13 for illuminating a reticle arranged in an object field and 14.

2. a projection optic for imaging structures of the reticulum onto a wafer arranged in an image field. [15] Metrology system for inspecting a mask for EUV lithography with an illumination system according to claim 13.

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