Insert for an outer insert for an EUV radiation source

Abstract

An insert (bore) for an outer insert (8) for an EUV radiation source (1) is produced from a fibre-reinforced material.

Description

[0001] Insert for an outer insert for an EUV radiation source

[0002] The present patent application claims the priority of German patent application DE 10 2024 203 895.4, the contents of which are incorporated herein by reference.

[0003] The invention relates to an insert (bore) for an outer insert (carrier) for an EUV radiation source. The invention also relates to an insert for an EUV radiation source having such an inner insert. Furthermore, the invention relates to an EUV radiation source having such an insert and to an illumination system for a projection exposure apparatus, a mask inspection apparatus or a metrology system having such an EUV radiation source, and to a projection exposure apparatus and a metrology system having a corresponding illumination system. Finally, the invention relates to a method for producing an insert (bore) for an EUV radiation source.

[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. A problem addressed by the invention is that of improving an inner insert (bore) for an outer insert (carrier) for an EUV radiation source. This problem is solved by an insert according to the invention.

[0006] According to one aspect of the invention, the insert comprises at least partially a fibre-reinforced material. In particular, the insert can consist of fibre-reinforced material.

[0007] The insert can be made of a fibre-reinforced material.

[0008] It was found that this is linked to numerous advantages.

[0009] Use of a fibre-reinforced material allowed the coefficient of thermal expansion to be reduced significantly. This allowed thermal stresses to be reduced during operation. This led to a lower probability for the formation of cracks during operation.

[0010] Moreover, production costs could be reduced significantly.

[0011] Furthermore, the strength of the insert could be increased.

[0012] Finally, the thermal conductivity of the insert could be improved.

[0013] 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.

[0014] 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.

[0015] The bore insert may be produced from ceramics in particular.

[0016] According to one aspect, the inner insert may comprise, at least in part, silicon carbide (SiC), graphite or an isotropic SiSiC material. It can in particular consist of such a material. The inner insert can be made of silicon carbide (SiC), graphite or an isotropic SiSiC material. For example, an appropriate SiSiC material is available under the trade name Cesic®. In particular, the material may comprise diffusely arranged short fibres.

[0017] In particular, fibres with a length of no more than 1 mm, in particular no more than 0.3 mm and in particular no more than 0.1 mm, are referred to as short fibres. In particular, the proportion of such short fibres may be at least 90%.

[0018] According to one aspect, the insert may comprise a material having a coefficient of thermal expansion of at most 6 x 10-6 / K, in particular 4.5 x 10- 6 / K, in particular 4 x 10-6 / K, in particular 3 x 10-6 / K, in particular 2 x 10- 6 / K, in particular 1.5 x 10-6 / K. It can in particular consist of such a material.

[0019] The insert can be made of a material with a coefficient of thermal expansion of at most 6 x 10-6 / K, in particular 4.5 x 10-6 / K, in particular 4 x 10- 6 / K, in particular 3 x 10-6 / K, in particular 2 x 10-6 / K, in particular 1.5 x 10-6 / K.

[0020] This information may relate in particular to the fibres in the material. According to a further aspect, the insert may comprise continuous carbon fibres. In particular, the fibres may have a length of at least 1 cm, in particular at least 3 cm and in particular at least 5 cm. The proportion of fibres with such a minimum length may be at least 50% in particular, in particular at least 70% and in particular at least 90%. The proportion of short fibres, in particular fibres with a length of less than 3 cm, may be no more than 30% in particular, in particular no more than 20% and in particular no more than 10%. According to a further aspect, what are known as high temperature carbon fibres may serve as fibres for the insert. This can further improve the thermal conductivity. The thermal conductivity can be improved in the fibre direction in particular. As a result of aligning the fibres in one or more specific directions it is possible to influence the heat dissipation and the strength of the insert in a targeted maimer.

[0021] This can increase the strength of the insert and hence its service life.

[0022] According to another aspect, the insert may have a longitudinally extending internal passage channel.

[0023] According to a further aspect, the fibres of the insert may have a specific orientation. In particular, the fibres of the insert may be arranged obliquely to the longitudinal direction. In this case, an oblique arrangement of the fibres is understood to mean an arrangement in which the fibres are arranged neither parallel nor perpendicular to the longitudinal direction. In particular, the fibres may be arranged at an angle ranging from 20° to 70° with respect to the longitudinal direction. The orientation of the fibres can be predetermined in a targeted maimer when producing the insert. In particular, a wound tube or a fabric with appropriately oriented fibres may be used for the production of the insert.

[0024] According to a further aspect, the insert may comprise an inner portion, a middle portion and an outer portion in succession in the longitudinal direction, wherein the middle portion has a smaller diameter than the inner portion and the outer portion.

[0025] The outer portion may have an extent in the longitudinal direction that is at least 30%, in particular at least 50%, in particular at least 70% and in particular at least 100%, of an extent of the middle portion in the longitudinal direction. This aspect may be independent of other aspects, in particular independent of the use of a fibre-reinforced material for the bore. The aspects may also be combined with one another.

[0026] In particular, the portions may follow one another directly, in particular rest against one another.

[0027] According to the further aspect, the insert may also be formed in one piece. In this case, the middle portion and the outer portion in particular are formed together in one piece.

[0028] The inner portion may also be formed separately from the middle portion.

[0029] In this case, the term portion should be understood purely in a geometric sense. In particular, a portion need not be a separate constituent part thereto. The different portions may have different internal diameters in particular. In particular, they may be defined by way of their internal diameters. In this case, the middle portion may have the smallest internal diameter.

[0030] The outer portion may have an outwardly increasing internal diameter. In particular, it may take the form of a funnel.

[0031] The portions may have an identical external diameter in particular.

[0032] In particular, the portions may have an external diameter that remains the same over their extent in the longitudinal direction.

[0033] A further problem addressed by the invention is that of improving an outer insert (carrier) for a source chamber of an EUV radiation source.

[0034] This problem is solved by an insert having an inner insert according to the preceding description arranged in a passage channel.

[0035] The advantages are evident from those of the inner insert.

[0036] According to an aspect, the inner insert lies flat against the inside of the outer passage channel.

[0037] Another purpose of the invention is to improve an EUV radiation source.

[0038] According to one aspect of the invention, the EUV radiation source comprises a fibre-reinforced material. According to another aspect of the invention, it can be made, in particular at least partially, from a fibre-reinforced material. It has the advantages as described with respect to the insert.

[0039] According to another aspect of the invention, the EUV radiation source may comprise a source chamber having a fibre-reinforced material. In particular, the source chamber is at least partially made of a fibre-reinforced material. In particular, the source chamber is made of a fibre-reinforced material. The source chamber may consist of a fibre-reinforced material.

[0040] In addition, the source chamber can have a chamber wall with at least one chamber opening, an outer insert (carrier) inserted in the chamber opening with an outer passage channel extending in a longitudinal direction, and an inner insert (bore insert) inserted in the outer passage channel with an inner passage channel extending in the longitudinal direction. The chamber wall and / or the inner insert and / or the outer insert may comprise a fibre-reinforced material or be made of a fibre-reinforced material, in particular be at least partially made of such a material.

[0041] An EUV radiation source of this type can have the following features: EUV radiation source having a source chamber with a chamber wall having at least one chamber opening, a first insert inserted into the chamber opening and having an outer through-channel extending in a longitudinal direction, and an inner insert arranged in the outer passage channel and having an inner passage channel extending in the longitudinal direction. In this case, the source chamber can be made at least partially from a fibre- reinforced material. It can in particular consist of a fibre-reinforced material. It can in particular be formed according to the aforementioned description.

[0042] According to a further aspect of the invention, the source chamber may comprise an inner insert according to the preceding description.

[0043] An EUV radiation source of this kind can have the following features: EUV radiation source having a source chamber with a chamber wall having at least one chamber opening, a first insert inserted into the chamber opening and having an outer through-channel extending in a longitudinal direction, and an inner insert arranged in the outer passage channel and having an inner passage channel extending in the longitudinal direction.

[0044] In this case, the inner insert can be designed in particular in accordance with the above description.

[0045] The use of an inner insert according to the preceding description allows improvements to be made in an EUV radiation source, in particular an EUV xenon plasma source, in an illumination system for a projection exposure apparatus, in a mask inspection apparatus or a metrology system having such an EUV radiation source, in a projection exposure apparatus for EUV lithography and in a metrology system for inspecting a mask for EUV lithography. Furthermore, a lighting system for a projection exposure system, a mask inspection system or a metrology system can have an EUV radiation source with an outer insert (carrier).

[0046] A further problem addressed by the invention is that of improving a method for producing an insert for an EUV radiation source.

[0047] This problem is solved by a method having the following steps: winding a tubular main body, impregnating the fibres with an adhesive that is able to completely carbonize, pyrolysing the main body, infiltrating the main body with silicon or vapour depositing silicon carbide (SIC) on the main body, and mechanically processing the main body.

[0048] In this case, the main body may be longer in particular than the length of the insert to be produced. In particular, a plurality of such inserts may be produced from the main body. In particular, the length of the main body may be at least 10 cm, in particular at least 20 cm, in particular at least 30 cm, in particular at least 50 cm and in particular at least 1 m.

[0049] Phenolic resin in particular may serve as adhesive. The mechanical processing may in particular comprise the division of the main body into a plurality of parts. In so doing, the main body is severed perpendicular to the longitudinal direction in particular.

[0050] To pyrolyse the main body, the latter is heated to at least 700°C, in particular at least 800°C and in particular at least 900°C.

[0051] Pyrolysis may be implemented under the exclusion of oxygen in particular.

[0052] To infiltrate the main body with silicon, the main body or parts thereof may be heated together with silicon granulate in a chamber. The silicon may be fused on in the process. In an alternative to that or in addition, silicon carbide may be vapour deposited on the main body post pyrolysis. Chemical vapour deposition (CVD) may be provided to this end. This may lead to improved strength of the insert. In particular, what may be achieved thereby is that no uncrosslinked silicon is present in the material of the main body.

[0053] Excess silicon may subsequently be removed from the main body. A mechanical method may be provided to this end, for example sandblasting. Corundum in particular may be used as an abrasive. Excess silicon can be removed well as a result.

[0054] Mechanical processing, for example a turning method, can be used to produce the inner insert (bore) from the main body that was produced and treated thus.

[0055] The finishing may comprise one or more cleaning steps. Further features and details of the invention will become apparent from the description of exemplary embodiments with reference to the figures, in which:

[0056] Fig. 1 shows a schematic sectional drawing of an EUV radiation source,

[0057] 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,

[0058] Fig. 3 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 according to a variant,

[0059] Fig. 4 schematically shows a longitudinal section through an insert (bore) for an outer insert (carrier) of a source chamber of an EUV radiation source,

[0060] Fig. 5 schematically shows a mat for producing the insert according to Fig. 4 with fibres that are oriented in specific directions,

[0061] Fig. 6 shows a mat according to Fig. 5 with alternative fibre orientations,

[0062] Fig. 7 schematically shows a longitudinal section through an insert according to Fig. 4 with diffusely arranged short fibres and Fig. 8 schematically shows a view of the insert according to Fig. 7 in an unwound state.

[0063] Figure 1 illustrates a schematic sectional drawing of an exemplary embodiment of an EUV radiation source 1. Figures 2 and 3 show 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.

[0064] 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.

[0065] 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.

[0066] The upper chamber part 3 is also referred to as source chamber below.

[0067] The centre plate 5 has off-centred openings 6 and a central opening 7. 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.

[0068] 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.

[0069] 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).

[0070] 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.

[0071] 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.

[0072] The EUV radiation source 1 is an induction plasma current generator.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] The inner insert 11 may be thermally shrunk in the passage channel 10.

[0081] 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.

[0082] 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. It moreover comprises an outer portion 28 in the variant according to Figure 3. 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.

[0083] The inner portion 26, the middle portion 27 and the outer portion 28 may have substantially constant external diameters over their extent in the Ion- gitudinal direction 9. In particular, they may have identical external diameters. It is possible to manage without the outer portion 28, as depicted in Figure 2.

[0084] 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.

[0085] The middle portion 27 has a smaller internal diameter dm than the inner portion 26 with an internal diameter di, dm < di.

[0086] Different variants of the inner insert 11 are described in exemplary fashion below with reference to Figures 4 to 8.

[0087] In the variant of the inner insert 11 depicted schematically in Figure 1, the insert 11 is produced from a wound tube or fabric 31. It comprises successive layers 32 with fibres 33 of different orientations.

[0088] Figures 5 and 6 depict, by way of example, different orientations of the fibres 33 in two successive layers 32 in a wound state of the insert 11.

[0089] In particular, the fibres 33 have an oblique orientation with respect to the longitudinal direction 9. In particular, the fibres 33 are arranged at angles ranging from 20° to 70° with respect to the longitudinal direction 9. This led to particularly uniform wear-and-tear behaviour.

[0090] The geometry of the insert 11 is depicted in Figures 4 and 7 purely by way of example. In particular, this should not be construed as restrictive. In particular, the insert 11, or at least portions thereof, may also have a geometry deviating therefrom. According to the variant depicted in Figures 7 and 8, the material for the insert 11 comprises diffusely arranged short fibres.

[0091] A method for producing the insert 11 is described in exemplary fashion below.

[0092] A main body may be wound initially in order to produce the insert 11.

[0093] Continuous fibres may be used for the main body. Fabric mats may also be used.

[0094] A CNC winding machine may be provided for winding the main body.

[0095] The fibres are preferably impregnated with an adhesive that is able to completely carbonize.

[0096] The main body may be much longer than the length of the insert 11 to be produced. In particular, the main body may have a length of the order of 1 m. By preference, a plurality of inserts 11 may be manufactured from the main body.

[0097] The main body is subsequently pyrolysed.

[0098] To pyrolyse the main body, the latter is heated to approx. 1000°C in a furnace. In the process, the adhesive may be converted to pure carbon.

[0099] The method may subsequently comprise mechanical processing of the main body. The mechanical processing may optionally also be implemented at a later time. In particular, the main body may be subdivided into a plurality of shorter pieces.

[0100] The main body or the pieces may then be infiltrated with silicon.

[0101] For the infiltration with silicon, the component parts are placed into a furnace together with silicon granulate. There, the silicon may be liquefied by heating. In the process, it may consolidate in the main body or the pieces. Subsequently, the excess silicon is removed from the components. Mechanical processing, in particular sandblasting, may be provided to this end.

[0102] Lastly, there is final mechanical processing and cleaning. In the process, the component is turned to the envisaged final dimensions.

[0103] The description of the production method should not be construed as restrictive but as merely exemplary. Deviations and / or modifications of the method are possible.

Claims

Claims1. Insert (11) for an outer insert (8) for an EUV radiation source (1) characterized in that the insert (11) is at least partially made of a fibre-reinforced material.

2. Insert (11) according to Claim 1, characterized in that said insert comprises at least partially silicon carbide (SiC), graphite or an isotropic SiSiC material.

3. Insert (11) according to either of the preceding claims, characterized in that said insert comprises a material with a coefficient of thermal expansion of at most 6xlO-6 / K.

4. Insert (11) according to any of the preceding claims, characterized in that said insert comprises continuous carbon fibres.

5. Insert (11) according to any of the preceding claims, characterized in that said insert comprises high temperature carbon fibres.

6. Insert (11) according to any one of the preceding claims, characterized by an internal passage channel (12) extending in a longitudinal direction (9).

7. Insert (11) according to Claim 6, characterized in that the material of the insert (11) comprises fibres with an oblique orientation with respect to the longitudinal direction (9).

8. Insert (11) according to claims 6 or 7, characterized in that said insert comprises an inner portion (26), a middle portion (27) and an outer portion (28) in succession in the longitudinal direction (9),8.1 wherein the middle portion (27) has a smaller internal diameter (dm) than the inner portion (26) and the outer portion (28), and8.2 wherein the outer portion (28) has an extent (la) in the longitudinal direction that is at least 30% of an extent (lm) of the middle portion (27) in the longitudinal direction (9).

9. Insert (11) according to any of the preceding claims, characterized in that said insert is formed in one piece.

10. Insert (8) for an EUV radiation source (1), having10.

1. an outer passage channel (10) extending in a longitudinal direction (9), and10.2 an inner insert (11) according to any of the preceding claims arranged in the outer passage channel (10).

11. Insert (8) according to Claim 10, characterized in that the inner insert (11) lies flat against the inside of the outer passage channel (10).

12. EUV radiation source (1) comprising a fiber-reinforced material.

13. EUV radiation source (1) according to claim 12, characterized by a source chamber (2) comprising a fiber-reinforced material.

14. EUV radiation source (1) according to claim 13, characterized in that the source chamber has an inner insert (11) according to one of claims I to 9.

15. Illumination system for a projection exposure apparatus, a mask inspection apparatus or a metrology system, having an EUV radiation source (1) according to any of Claims 12 to 14.

16. Projection exposure apparatus for EUV lithography, comprising16.1 an illumination system according to Claim 15 for illuminating a reticle that is arranged in an object field, and16.2 a projection optics unit for imaging the reticle onto a wafer that is arranged in an image field.

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

18. Method for producing an insert (11) for an EUV radiation source (1), comprising the following steps:18.1 winding a tubular main body () from a fibre-containing material,18.2 impregnating the fibres with an adhesive that is able to completely carbonize,18.3 pyrolysing the main body,18.4 infiltrating the main body with silicon or vapour depositing silicon carbide (SIC) on the main body,18.5 mechanically processing the main body.

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