Insert for a chamber wall of a source chamber of an EUV radiation source

Abstract

An insert (8) for a chamber wall of a source chamber (2) of an EUV radiation source (1) comprises a contact portion (31) of a contact surface, against which a contact element (50) rests extensively.

Description

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

[0002] The present patent application claims the priority of the German patent application DE 10 2024 203 897.0, the contents of which are incorporated herein by reference.

[0003] The invention relates to an insert for a chamber wall of a source chamber of an EUV radiation source. The invention also relates to an EUV radiation source having such an insert, an illumination system having such an EUV radiation source, and a projection exposure apparatus and a metrology system having a corresponding illumination 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 chamber wall of a source chamber of an EUV radiation source. In particular, the insert should be improved in view of temperature dissipation.

[0007] This problem is solved by an insert according to the invention. According to an aspect of the invention, the insert comprises a contact surface, against which a contact element rests extensively, in particular in a surface area.

[0008] Herein surface area denotes in particular an area with positive Lebesgue measure.

[0009] According to a further, independent aspect of the invention, a corresponding contact element can also partially rest against another contact surface, in particular a contact surface in or on a chamber wall of a source chamber of an EUV radiation source. This can improve the dissipation of heat from the source chamber.

[0010] The contact element may also be fully integrated into the insert. In particular, the contact element may be milled into the carrier. In so doing, the radial geometry is preferably milled first. The individual spring elements can subsequently be milled free.

[0011] In particular, at least sections of the contact element may have a surface that, in sections, forms portions of a lateral face of a cylinder or portions of a lateral face of a cone. In principle, curved surfaces are also possible.

[0012] 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. Together, the carrier with the inner insert (bore insert) is also referred to as a bore. The carrier may comprise a main body made of copper. The bore insert may be produced from ceramics in particular. This can improve the thermal conductivity and / or the electrical conductivity, especially from the insert to the chamber wall of the source chamber surrounding the latter.

[0013] An extensive contact should be understood to mean, in particular, a contact in which the contact area in two mutually perpendicular directions has a respective extent of at least 1 mm, in particular at least 2 mm, in particular at least 3 mm, in particular at least 5 mm and in particular at least 1 cm. In particular, the contact area may in each case be at least 50 mm2, in particular at least 100 mm2, in particular at least 200 mm2, in particular at least 300 mm2, in particular at least 500 mm2, in particular at least 1 cm2, in particular at least 2 cm2, in particular at least 3 cm2and in particular at least 5 cm2.

[0014] In particular, the resting area may have a quadrilateral form, in particular rectangular form, or a hexagonal form.

[0015] The contact element may extensively rest against the contact surface in a plurality of regions. In particular, it may have a respective extensive contact at its ends. The contact surface at the ends may rest against the insert in a region that has the shape of a lateral cylinder face or the shape of a conical section.

[0016] According to one aspect, the insert has a passage channel extending in a longitudinal direction, which is arranged in an insert wall. In particular, the insert may be surrounded by the insert wall on the periphery. According to an aspect, the contact element may have an elastically resilient form.

[0017] In particular, a split washer may serve as contact element.

[0018] The contact element may be produced as a bent and stamped part.

[0019] In particular, it may be produced from a part with a surface that takes the form of a free-form surface.

[0020] This allows particularly great flexibility when shaping the contact element.

[0021] According to an aspect, the contact portion may be arranged at an inner end of the insert in terms of the longitudinal direction.

[0022] In this context, the end of the insert facing the source chamber is referred to as inner end in particular.

[0023] In particular, the insert has a smaller external diameter at the inner end than at the outer end.

[0024] According to an aspect of the invention, the insert consists of a material that exhibits good thermal conductivity and / or good electrical conductivity.

[0025] In particular, a material exhibiting good thermal conductivity should in this context be understood to mean a material having a coefficient of thermal conduction of at least 100 W / mK, in particular at least 200 W / mK, in particular at least 300 W / mK and in particular at least 400 W / mK. In particular, a material exhibiting good electrical conductivity should be understood to mean a material having a conductivity of at least 5 106S / m, in particular at least 1 x 107S / m, in particular at least 3 x 107S / m and in particular at least 5x 107S / m.

[0026] In particular, the insert may consist of silver and / or copper and / or aluminium and / or compounds of these elements.

[0027] In particular, the insert may be made of a material with a thermal coefficient and / or an electrical conductivity that are at least equal to those of aluminium or copper, and in particular at least equal to those of silver.

[0028] The insert according to the invention may lead to improvements of an EUV radiation source, in particular of an EUV xenon plasma source.

[0029] According to an aspect, the contact element may rest extensively against the chamber wall.

[0030] In particular, it may rest extensively against the chamber wall in a central region.

[0031] In particular, the contact element may rest extensively against both the insert and the chamber wall. Particularly good thermal dissipation may be achieved in this way.

[0032] According to an aspect, the contact element may be prestressed in the inserted state of the insert. Particularly good thermal and / or electrical contact between the insert and the chamber wall may be achieved in this way.

[0033] In particular, the thermal deformations of the insert and / or of the chamber wall may also be compensated for by a prestressing of the contact element.

[0034] An EUV radiation source according to the previous description leads to an improved illumination system and hence to an improvement in a projection exposure apparatus or a metrology system.

[0035] Further advantages and details of the invention will become apparent from the description of an exemplary embodiment on the basis of the figures, in which:

[0036] Fig. 1 shows a schematic sectional drawing of an EUV radiation source,

[0037] 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,

[0038] Fig. 3 shows a schematic view of a contact element which forms extensive contacts at least in the inserted state of the insert and

[0039] Fig. 4 shows a schematic view of a moulded part from which the contact element according to Figure 3 can be produced. 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.

[0040] 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.

[0041] 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.

[0042] The upper chamber part 3 is also referred to as source chamber below.

[0043] The centre plate 5 has off-centred openings 6 and a central opening 7.

[0044] 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. 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.

[0045] 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).

[0046] 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.

[0047] 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.

[0048] The EUV radiation source 1 is an induction plasma current generator.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] Details of the first, outer insert (carrier) 8 and in particular of the second, inner insert (bore) 11 are described below with reference to Figures 2 and 3. Corresponding embodiments of the inserts 8, 11 are advantageous, independently of the remaining structural details of the EUV radiation source 1.

[0053] 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. 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.

[0054] 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.

[0055] The inner insert 11 may be thermally shrunk in the passage channel 10.

[0056] The inner insert 11 may also be soldered, welded or adhesively bonded to the passage channel 10. It may also be form-fittingly connected and / or integrally bonded to the passage channel 10.

[0057] 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 follow one another in the longitudinal direction 9. In particular, they may adjoin one another in the longitudinal direction 9.

[0058] 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.

[0059] 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. The middle portion 27 has a smaller internal diameter dm than the inner portion 26 with an internal diameter di, dm < di.

[0060] The insert 8 has a contact portion 31 at its inner end in the longitudinal direction 9.

[0061] A contact element may be provided for improving the thermal contact and / or the electrical conductivity between the insert 8 and the chamber wall that surrounds the latter. In particular, a split washer 50 may serve as contact element. In particular, this is an extensive contact split washer. The latter refers to a split washer which does not only have linear contacts 8 but leads to extensive contacts with the insert 8 and / or the chamber wall in the event of a proper arrangement of the insert 8 in a wall of the source chamber 2.

[0062] By way of example, Figure 3 shows such a split washer 50 in the deformed state, which is assumed when the insert 8 is inserted into the chamber wall.

[0063] The split washer 50 has a stripe-shaped or ring-shaped contact region 51.

[0064] The split washer has a quadrilateral contact region 52.

[0065] By way of example, Figure 4 depicts a moulded part 53, from which the split washer can be produced. In particular, the moulded part 53 is a bent and stamped part.

[0066] The moulded part 53 may have one or more free-form surfaces.

Claims

Claims1. Insert (8) for a chamber wall of a source chamber (2) of an EUV radiation source (1), comprising1.1 a passage channel (10) that extends in a longitudinal direction (9) 1.1.1 which is arranged in an insert wall,1.2 wherein the insert wall has at least one contact portion (31) with a contact surface,1.3 wherein a contact element rests extensively against the contact surface.

2. Insert (8) according to claim 1, characterized in that the passage channel (10) is surrounded circumferentially by the insert wall.

3. Insert (8) according to Claim 1 or 2, characterized in that the contact element has an elastically resilient form.

4. Insert (8) according to either of the preceding claims, characterized in that a split washer (50) serves as contact element.

5. Insert (8) according to any of the preceding claims, characterized in that the contact portion (31) is arranged at an inner end of the insert (8) in terms of the longitudinal direction (9).

6. Insert (8) according to any of the preceding claims, characterized in that said insert is made of a material with a coefficient of thermal conduction of at least 100 W / mK and / or an electrical conductivity of at least 5 104S / m.

7. EUV radiation source (1), comprising7.1 a source chamber (2) having7.1.1 a chamber wall comprising at least one chamber opening,7.1.2 an insert (8) inserted into the chamber opening,7.2 wherein the insert (8) is formed according to any of Claims 1 to 6.

8. EUV radiation source (1) according to Claim 7, characterized in that the contact element rests extensively against the chamber wall.

9. EUV radiation source (1) according to Claim 8, characterized in that the contact element is prestressed in the inserted state of the insert (8).

10. Illumination system for a projection exposure apparatus (), a mask inspection apparatus or a metrology system, having an EUV radiation source with an insert (8) according to any of Claims 1 to 6.

11. Projection exposure apparatus for EUV lithography, comprising11.1 an illumination system according to Claim 10 for illuminating a reticle that is arranged in an object field, and11.2 a projection optics unit for imaging structures of the reticle onto a wafer that is arranged in an image field.

12. Metrology system for inspecting a mask for EUV lithography, having an illumination system according to Claim 10.

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