EUV radiation source, insert for an EUV radiation source and insert for an insert for an EUV radiation source

Abstract

An inner insert for a passage opening in an outer insert for an EUV radiation source is embodied in multiple parts and/or has a plurality of sections that extend in the longitudinal direction and have different internal diameters (d.sub.i, d.sub.a).

Claims

1. An EUV radiation source, comprising a source chamber with a chamber wall having at least one chamber opening, a first insert, inserted into the chamber opening, with an outer passage channel extending in a longitudinal direction, and an inner insert, arranged in the outer passage channel, with an inner passage channel extending in the longitudinal direction, wherein the inner insert is embodied in two or more separate parts that adjoin one another in the longitudinal direction and has a plurality of sections that extend in the longitudinal direction and have different internal diameters (di, da), which are constant in the longitudinal direction.

2. The EUV radiation source of claim 1, wherein the inner insert is arranged in the outer passage channel such that it completely covers an inner wall, which extends parallel to the longitudinal direction from a first end region to a second end region, of the outer passage channel in the region of the first end region in the direction perpendicular to the longitudinal direction.

3. An insert configured to be disposed in a source chamber of an EUV radiation source, in which the source chamber comprises a chamber wall having at least one chamber opening, the insert comprising an outer passage channel extending in a longitudinal direction, and an inner insert, arranged in the outer passage channel, with an inner passage channel extending in the longitudinal direction, wherein the inner insert is embodied in two or more separate parts that adjoin one another in the longitudinal direction and has a plurality of sections that extend in the longitudinal direction and have different internal diameters (di, da), which are constant in the longitudinal direction.

4. The insert of claim 3, wherein the inner insert lies flat against the inside of the outer passage channel.

5. The insert of claim 3, wherein the inner insert is arranged in the outer passage channel such that it completely covers an inner wall, which extends parallel to the longitudinal direction from a first end region to a second end region, of the outer passage channel in the region of the first end region in the direction perpendicular to the longitudinal direction.

6. An illumination system for a projection exposure apparatus, a mask inspection apparatus or a metrology system, having an EUV radiation source with an insert according to claim 3.

7. A projection exposure apparatus for EUV lithography, comprising the illumination system according to claim 6 for illuminating a reticle arranged in an object field, and a projection optical unit for imaging the reticle onto a wafer arranged in an image field.

8. The projection exposure apparatus of claim 7, wherein the inner insert lies flat against the inside of the outer passage channel.

9. The projection exposure apparatus of claim 7, wherein the inner insert is arranged in the outer passage channel such that it completely covers an inner wall, which extends parallel to the longitudinal direction from a first end region to a second end region, of the outer passage channel in the region of the first end region in the direction perpendicular to the longitudinal direction.

10. A metrology system for inspecting a mask for EUV lithography, having the illumination system according to claim 6.

11. The illumination system of claim 6, wherein the inner insert lies flat against the inside of the outer passage channel.

12. The illumination system of claim 6, wherein the inner insert is arranged in the outer passage channel such that it completely covers an inner wall, which extends parallel to the longitudinal direction from a first end region to a second end region, of the outer passage channel in the region of the first end region in the direction perpendicular to the longitudinal direction.

13. The illumination system of claim 6, wherein the inner insert is produced at least partially from molybdenum or a molybdenum compound.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Further advantages and details of the invention will become apparent from the description of exemplary embodiments with reference to the figures. In the figures:

(2) FIG. 1 shows a schematic sectional drawing of an EUV radiation source,

(3) FIG. 2 shows a partially schematic sectional illustration through a detail from a source chamber of the EUV radiation source in the region of a passage channel, and

(4) FIG. 3 shows an illustration according to FIG. 2 with a variant of the inner insert in the passage channel.

DETAILED DESCRIPTION

(5) FIG. 1 illustrates a schematic sectional drawing of an exemplary embodiment of an EUV radiation source 1. The EUV radiation source 1 is part of an illumination system (not illustrated explicitly) of a projection exposure apparatus. For fundamental details, reference is made by way of example to DE 10 2017 212 352 A1, which is hereby fully incorporated in the present application as part thereof.

(6) The EUV radiation source 1 has a two-part source chamber 2 having an upper chamber part 3 and a lower chamber part 4. A center plate 5 is located between the upper chamber part 3 and the lower chamber part 4. The center plate 5 forms a chamber wall of the source chamber 2, in particular of the upper chamber part 3.

(7) The center plate 5 has eccentric openings 6 and a central opening 7.

(8) The center plate 5 can be embodied in multiple parts. It can have in particular a plate 18, which faces the source chamber 2 and to which a high voltage is able to be applied, and, separately therefrom, an outer base plate 19.

(9) 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 has a first passage channel 10 extending in a longitudinal direction 9.

(10) 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 carrier with the inner insert 11 is sometimes also referred to as “bore”.

(11) 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.

(12) During 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.

(13) The EUV radiation source 1 is an induction plasma current generator. Constituent parts of an illumination optical unit (not illustrated 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 optical unit is in particular a constituent part of an illumination system. The illumination system can comprise in particular one or more mirrors, in particular one or more facet mirrors. The illumination optical unit in particular serves for transferring illumination radiation, which has been generated by the EUV radiation source 1, to a mask having structures to be imaged. The mask is also referred to as reticle.

(14) FIG. 1 likewise schematically illustrates 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 A1, in particular to FIG. 23 and the associated description.

(15) The maintenance region 14 is sealable so as to be vacuum-tight with respect to an outer region 17 with the aid of a maintenance flap 16. The maintenance flap 16 can be opened for maintenance purposes. In the opened state of the maintenance flap 16, the maintenance region 14, and consequently the EUV radiation source 1, can be accessed. It is in particular 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. Details of the first insert 8 and in particular of the second insert 11 are described below with reference to FIG. 2. Corresponding embodiments of the inserts 8, 11 are advantageous independently of the remaining construction details of the EUV radiation source 1.

(16) The outer, first insert 8 is connected, for example via a plurality of screws, to the plate 18. It has in particular an electrical contact 21 to the plate 18. An O-ring is provided in the connection region between the first insert 8 and the plate 18.

(17) The first insert 8 is connected, for example via a plurality of screws, to the base plate 19. It has in particular an electrical contact 23 to the base plate 19. An O-ring is provided in the contact region between the first insert 8 and the base plate 19.

(18) The inner, second insert 11 lies circumferentially against the inner circumference of the first passage channel 10. It is arranged in particular substantially without play in the first passage channel 10. However, it can be arranged in the first passage channel 10 so as to be displaceable in the longitudinal direction.

(19) The inner insert 11 can be thermally shrunk in the passage channel 10. The inner insert 11 can also be soldered, welded or adhesively bonded to the passage channel 10. It can also be connected to the passage channel 10 with a form fit and/or by a material bond.

(20) In the variant illustrated in FIG. 2, the inner insert 11 is formed in two parts. It has in particular an inner part 26 and an outer part 27 adjoining the former in the longitudinal direction 9. The inner part 26 and the outer part 27 are formed by separate parts.

(21) The two parts 26, 27 are disposed next to one another.

(22) The inner part 26 and the outer part 27 have substantially constant external diameters over their extents in the longitudinal direction 9. They have in particular identical external diameters.

(23) The inner part 26 and the outer part 27 can be made from the same material. They can be made in particular from silicon carbide. It is also possible for one or both of these parts 26, 27 to be produced from molybdenum or a molybdenum compound. The inner part 26 and/or the outer part 27 can in particular consist of molybdenum or a molybdenum compound.

(24) The outer part 27 has a larger internal diameter than the inner part 26. The ratio of the internal diameter d.sub.a of the outer part 27 to the internal diameter d.sub.i of the inner part 26 lies in the range from 1.1 to 5, in particular in the range from 1.5 to 3.

(25) The outer part 27 extends in the longitudinal direction up to an inner end region 28 of the first passage channel 10. The first passage channel 10 is not covered in the region of its opposite, second end region by the insert 11.

(26) The outer part 27 is embodied in the manner of a sleeve. In particular, it is of a hollow cylindrical design. In particular, it can have a cross section with a circular outer circumference and a circular inner circumference.

(27) The inner part 26 is embodied in the manner of a sleeve. In particular, it is of a hollow cylindrical design. However, it has end-side bevels 30, 31.

(28) A variant of the inner, second insert 11 will be described below with reference to FIG. 3. Identical components have the same reference signs as in the variant according to FIG. 2.

(29) In this variant, the first passage channel 10 extends up to the inner end of the first insert 8 in the longitudinal direction 9. As opposed to the variant according to FIG. 2, it has no bevel. Accordingly, the outer part 27 of the insert 11 extends up to the end of the first insert 8 in the longitudinal direction 9.

(30) The outer part 27 in the variant according to FIG. 3 has approximately the same extent in the longitudinal direction 9 as the inner part 26.

(31) Generally, the two parts 26, 27 can have substantially identical extents in the longitudinal direction 9. It is also possible for the two parts 26, 27 to be formed with different extents in the longitudinal direction 9. The difference can be in particular more than 10%, in particular more than 20%, in particular more than 50%. It can be in particular less than 300%, in particular less than 200%, in particular less than 100%.

(32) The overall extent of the two parts 26, 27 in the longitudinal direction 9 lies in particular in the range from 2 cm to 15 cm, in particular in the range from 3 cm to 10 cm, in particular in the range from 4 cm to 8 cm.

(33) According to a variant, the two parts 26, 27 are not formed as separate parts but in one part. The inner, second insert 11 has two sections that extend in the longitudinal direction 9 and have different internal diameters d.sub.a, d.sub.i in this variant as well.

(34) A one-part design of the insert 11 makes the production of the insert 11 easier. It also simplifies the precise arrangement of the insert 11 in the passage channel 10.

(35) The insert 11 according to the variant illustrated in FIG. 2 being designed in two or more parts results in a reduction in the thermal stresses in the individual constituent parts of the insert 11. Hereby, the risk of the insert 11 breaking during the operation of the EUV radiation source 1 can be reduced.

(36) FIGS. 2 and 3 illustrate two-part variants of the insert 11. This should not be understood to be limiting. The insert 11 can also be embodied in one, three, four or more parts. Generally, it can have one, two, three, four or more constituent parts that are adjacent to one another in the longitudinal direction 9.

(37) Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. The separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments.

(38) Even though the invention has been described on the basis of specific embodiments, numerous variations and alternative embodiments will be apparent to the person skilled in the art, for example through combination and/or exchange of features of individual embodiments. Accordingly, it goes without saying for the person skilled in the art that such variations and alternative embodiments are also encompassed by the present invention, and the scope of the invention is restricted only within the meaning of the appended patent claims and the equivalents thereof.