EUV light source with a beam position control device

Description

Hintergrund der Erfindung

[0001] The invention relates to an EUV light source, comprising a supply device for providing a target material, at least one pulsed laser source for emitting at least one pulsed laser beam, a beam guiding device for supplying the at least one pulsed laser beam from the at least one pulsed laser source into a radiation generation chamber and for the focused irradiation of the target material with the at least one pulsed laser beam within the radiation generation chamber, wherein the target material is designed to emit EUV radiation as a result of the irradiation.

[0002] An EUV light source is a radiation source used to emit EUV radiation. EUV radiation refers to electromagnetic radiation with a wavelength between approximately 5 nm and approximately 30 nm. EUV radiation is used primarily in the semiconductor industry. Compared to currently common lithography systems, which operate at wavelengths in the UV wavelength range, the use of EUV radiation for microlithographic manufacturing allows for the reliable production of components with significantly smaller feature sizes, thus leading to a corresponding increase in performance.

[0003] The EUV light source mentioned above is suitable for generating EUV radiation using an LPP ("Laser Produced Plasma") process. The target material, which is typically a metal, in particular tin, is preferably provided in droplet form by means of the provision device. Each droplet is then irradiated within the radiation generation chamber, for example, a vacuum chamber, with one or more laser pulses of the at least one laser beam. In the case of multiple laser pulses, these comprise, for example, one, two, or possibly more than two so-called pre-pulses and a so-called main pulse. The pre-pulse(s) serve to prepare the droplet for irradiation with the main pulse, in particular to heat, expand, vaporize, and / or generate a plasma.The subsequent irradiation of each droplet with a main pulse serves to convert the target material into the plasma state, resulting in the emission of EUV radiation.

[0004] Accordingly, the at least one pulsed laser beam can be, for example, at least one pre-pulse laser beam or one main pulse laser beam. The at least one pulsed laser source can then be, for example, at least one pre-pulse laser source or one main pulse laser source. A CO2 laser can be used as the pre-pulse laser source, for example, and a solid-state laser can be used as the skin pulse laser source.

[0005] The beam guiding device serves to guide the at least one pulsed laser beam from the at least one pulsed laser source into the radiation generation chamber. For this purpose, the beam guiding device typically comprises a plurality of optical elements, in particular a plurality of reflective optical elements. If multiple pulsed laser beams are involved, their beam paths can run separately from one another or at least coincide in sections. When using multiple pre-pulse laser beams, these can run at least partially collinear; however, this is not necessarily the case. For focused irradiation of the target material, the beam guiding device further comprises at least one optical element with which the at least one pulsed laser beam is focused.

[0006] A beam guidance device for an EUV radiation generation device is known from WO 2015 / 036025 A1. There, a paraboloidal mirror is used to superimpose two laser beams that impinge on a first and a second surface area of ​​the paraboloidal mirror. A telescope arrangement with two lenses is arranged in the beam path of the second laser beam. Their spacing can be adjusted to change the focus position of the second laser beam in a direction perpendicular to the direction of movement of the target material. Tiltable deflection mirrors can be used to change the focus position of the second laser beam along the direction of movement of the target material. Aufgabe der Erfindung

[0007] The object of the invention is to provide an EUV light source of the type mentioned above, which allows a precise positioning of the at least one focused pulsed laser beam on the target material and an adjustment of the angle of incidence and is preferably characterized by a high dynamic range and, at the same time, a high adjustment resolution. Gegenstand der Erfindung

[0008] This object is achieved by an EUV light source of the type mentioned at the outset, in which the beam guiding device for adjusting the spatial position of the at least one pulsed laser beam has at least one beam position adjusting device which comprises four mirrors in the form of two pairs of mirrors, wherein the four mirrors are each rotatable about exactly one axis of rotation and the axes of rotation of the two mirrors of the first pair of mirrors are aligned along a first spatial direction and the axes of rotation of the two mirrors of the second pair of mirrors are aligned along a second spatial direction.

[0009] For the purposes of this application, the spatial position of a laser beam is understood as the combination of its position and beam direction. Assuming that the laser beam intersects a given plane, the position of the laser beam can be described by the point of intersection with this plane. This results in a total of four degrees of freedom for the spatial position: two spatial coordinates to describe the point of intersection of the laser beam with the plane, and two angles to describe the beam direction.

[0010] The four mirrors can be designed to allow a complete rotation or only rotation within a limited angular range. For example, a separate drive can be provided for each mirror to rotate the mirrors. For the purposes of this application, a pair of mirrors is understood to mean a combination of two mirrors.

[0011] Using the at least one beam position adjustment device, the spatial position of the at least one pulsed laser beam can be precisely adjusted. This allows the target material, for example, a tin droplet, to be hit with high precision, typically to within one micrometer or less, while simultaneously adjusting the angle of incidence with an accuracy on the order of microradians. This ultimately leads to high efficiency of the EUV light source.

[0012] If the target material is irradiated with multiple pulsed laser beams, the beam guidance device can have multiple beam position adjustment devices. Each of the beam position adjustment devices can be used to adjust the spatial position of one of the pulsed laser beams. A single beam position adjustment device can also be used to adjust the spatial positions of several of the pulsed laser beams. In the latter case, however, the spatial positions cannot be adjusted independently of one another.

[0013] By simultaneously adjusting the position and beam direction, the pivot point of the laser beam can be set to any point in the propagation direction of the pulsed laser beam. In other words, by adjusting the mirrors, at least one laser beam can be rotated by any point (in the propagation direction of the pulsed laser beam). In addition to its application in EUV light sources, this is also fundamentally important for other optical setups, for example, to ensure good imaging quality and smaller apertures on the optical elements.

[0014] An important characteristic of the beam position adjustment device is the adjustment resolution of the spatial position of the pulsed laser beam achieved. Here, it is useful to consider the adjustment resolution for the beam direction and the position of the pulsed laser beam separately. The adjustment resolution for the beam direction is determined by the angular resolution, i.e. the resolution of the rotation of the mirrors, and thus depends on the drive used. The adjustment resolution for the position of the pulsed laser beam perpendicular to the first spatial direction results from the angular resolution and the distance between the two mirrors of the first mirror pair. The adjustment resolution for the position of the pulsed laser beam perpendicular to the second spatial direction results accordingly from the angular resolution and the distance between the two mirrors of the second mirror pair.

[0015] Compared to devices that use two mirrors rotatable around two axes to adjust the beam position of a laser beam. These mirrors can be adjusted either manually or motorically. Due to their two-axis design, these mirrors only allow slow adjustment processes with a cutoff frequency in the range of a few hertz, the beam position adjustment device enables orders of magnitude faster adjustment and thus greater dynamics. Mirrors that can only be rotated around one axis of rotation can also typically achieve a higher angular resolution, resulting in a correspondingly higher adjustment resolution of the spatial position of the pulsed laser beam.

[0016] Devices that allow the beam angle of a laser beam to be adjusted using mirrors that can be rotated around a single axis are also used in laser material processing, for example, in laser marking or remote laser welding. The tilting of the laser beam is achieved by rotating the mirrors, which reflect the – usually collimated – laser beam, using a suitable drive. To realize any tilting movement in two axes, two of these mirrors are arranged one behind the other. Focusing on the typically flat processing plane is achieved using F-theta lenses. To achieve a constant angle of incidence on the processing plane, a telecentric F-theta lens is typically used. However, such devices usually do not allow adjustment of the spatial position of the laser beam, but are generally limited to two (angular) degrees of freedom.

[0017] An exception is DE 10 2015 109 984 A1, which describes a scanner head for laser material processing with a beam positioning system for adjusting the laser beam position. In one embodiment, the system comprises four rotatable mirrors, each of which is designed to rotate only about a single respective axis of rotation. Two of the four mirrors are aligned along a first spatial direction, a third of the four mirrors is aligned along a second spatial direction, and a fourth of the four mirrors is aligned along a third spatial direction, with all three spatial directions perpendicular to one another. In an alternative embodiment, the beam positioning system for adjusting the laser beam position has two dual-axis mirrors, each tiltable about two axes of rotation.

[0018] In one embodiment, the first spatial direction and the second spatial direction are perpendicular to each other. This perpendicular arrangement achieves decoupling between the two pairs of mirrors for adjusting the spatial position.

[0019] In a further embodiment, the two mirrors of the first pair of mirrors follow one another directly in the beam path. This maximizes the resolution for adjusting the position of the at least one pulsed laser beam perpendicular to the first spatial direction, given the rotation resolution of the mirrors of the first pair of mirrors.

[0020] In a further development of this embodiment, the distance between the two mirrors of the first mirror pair is less than 150 mm.

[0021] In a further embodiment, the two mirrors of the second pair of mirrors follow one another directly in the beam path. This maximizes the resolution for adjusting the position of the at least one pulsed laser beam perpendicular to the second spatial direction, given the rotation resolution of the mirrors of the second pair of mirrors.

[0022] In a further development of this embodiment, the distance between the two mirrors of the second mirror pair is less than 150 mm.

[0023] In a further embodiment, the first mirror of the second mirror pair is arranged in the beam path before the first mirror pair, and the second mirror of the second mirror pair is arranged after the first mirror pair. In this case, the first mirror in the beam path, i.e. the first mirror of the second mirror pair, and the second mirror in the beam path, which is one of the mirrors of the first mirror pair, can have smaller apertures, which allows for greater dynamics in the adjustment angle. The third mirror in the beam path, which is the other mirror of the first mirror pair, and the fourth mirror in the beam path, i.e. the second mirror of the second mirror pair, require larger apertures. Due to the greater distance between the two mirrors of the second mirror pair, a smaller rotational movement of the mirrors is necessary to adjust the position of the pulsed laser beam perpendicular to the second spatial direction.This results in a lower resolution for adjusting the position of the pulsed laser beam perpendicular to the second spatial direction, but also in a greater adjustment dynamic, which can be advantageous in certain cases.

[0024] In principle, the alignment of the rotation axes of the four mirrors can also deviate from the alignments described here. For example, the rotation axes of the first and third mirrors in the beam path can be aligned along a first spatial direction, and the rotation axes of the second and fourth mirrors in the beam path can be aligned along a second spatial direction that is perpendicular to the first spatial direction. However, different alignments sometimes require additional mirrors to correct the spatial direction or lead to a dependency between the adjustment axes.

[0025] In a further embodiment, the beam position adjustment device has at least one galvanometer drive for rotating each of the four mirrors around its respective axis of rotation. Galvanometer drives enable particularly dynamic adjustment of the spatial position of the pulsed laser beam, in particular adjustment in the frequency range of more than 1 kHz. Galvanometer drives also allow high angular resolution, i.e., high resolution for the rotation of the mirrors. This results in a high adjustment resolution for the spatial position of the pulsed laser beam, in particular, a beam direction resolution corresponding to an angle of less than 1 µrad and a position resolution corresponding to a spatial distance of 1 µm or less.

[0026] Instead of galvanometer drives, controlled brushless motors, possibly with a gear ratio between the motor and the mirror, can be used to rotate the mirrors. So-called voice coil drives can also be used. However, the latter typically have a smaller adjustment range and do not allow for a full rotation.

[0027] In a further embodiment, the EUV light source comprises at least one beam position detection device for detecting the spatial position of the at least one pulsed laser beam and at least one control device for controlling the spatial position of the at least one pulsed laser beam by means of the at least one beam position adjustment device. The beam position detection device can, for example, comprise at least one position-sensitive sensor (e.g., a quadrant sensor) and / or at least one position-sensitive camera. By arranging a position-sensitive sensor or a position-sensitive camera in the near field of the pulsed laser beam, the position can be detected; by arranging it in the far field, the angle can be detected. By means of the control device, the spatial position of the pulsed laser beam can be adjusted to a desired target value.For example, the angle of incidence of the pulsed laser beam and its position on the target material can be kept constant. The high dynamic range enables the correction of vibrations and other dynamic disturbances. This is especially true when using galvanometer drives, which make the correction of higher-frequency disturbances that regularly occur in the EUV light sources mentioned above possible. These requirements cannot be met with two-axis angle-adjustable mirrors or laterally displaceable lenses.

[0028] In a further embodiment, the deflection angle of the pulsed laser beam at at least one of the four mirrors lies in an angular range between 30° and 90°, preferably between 60° and 90°. When a laser beam is reflected from a mirror, the deflection angle refers to the angle between the incident and reflected laser beam. It corresponds to twice the angle of incidence. The deflection angle of the pulsed laser beam at the four mirrors is fundamentally arbitrary. However, a deflection angle of less than or equal to 90° is advantageous in order to keep the dimensions of the mirrors small and to optimize the efficiency and polarization dependence of the mirror coatings.

[0029] In a further embodiment, a front side of at least one of the four mirrors has a highly reflective coating for the pulsed laser beam. A highly reflective coating on the front side leads to fewer radiation losses and thus a higher efficiency of the EUV light source. The reflectance of the coated front side of the mirror should be as high as possible, for example, more than 98%, preferably more than 99%. The highly reflective coating can, for example, be a dielectric multilayer coating that exhibits maximum reflection at the wavelength of the pulsed laser beam. The design of such a highly reflective coating is familiar to those skilled in the art.

[0030] In a further embodiment, a rear side of at least one of the four mirrors has an anti-reflective coating for the at least one pulsed laser beam. Such an anti-reflective coating can prevent unwanted double reflections and reduce heating of the mirror during operation of the EUV light source. The anti-reflective coating can also be a dielectric multilayer coating that exhibits minimal reflection at the wavelength of the pulsed laser beam.

[0031] In a further embodiment, a substrate of at least one of the four mirrors for the at least one pulsed laser beam has low absorption. The material can be, for example, a silicate glass, in particular fused silica. This reduces or prevents heating of at least one of the four mirrors during operation of the EUV light source.

[0032] In a further embodiment, the beam guiding device is designed to feed the pulsed laser beam to the beam positioning device in a collimated or divergent manner. In this case, collimated feeding is generally preferred.

[0033] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, with reference to the figures of the drawing, which illustrate details essential to the invention, and from the claims. The individual features can be implemented individually or in combination in a variant of the invention. Zeichnung

[0034] Examples of embodiments are shown in the schematic drawing and are explained in the following description. Fig. 1 a schematic representation of an EUV light source with a beam guiding device comprising a first beam position adjusting device for adjusting the spatial position of a first pulsed laser beam and a second beam position adjusting device for adjusting the spatial position of a second pulsed laser beam, Figs. 2a, b, c schematic detailed views of the first beam position adjusting device of the Fig. 1 EUV light source shown, which has four mirrors in the form of two pairs of mirrors, and Figs. 3a,c,b schematic detailed views of a variant of the Fign. 2a,b,c shown beam position adjustment device.

[0035] In Fig. 1 is an EUV light source 1 which shows a radiation generating chamber 2, a provisioning facility 3 to provide a target material 4, a first pulsed laser source 5, a second pulsed laser source 6and a beam guidance device 7 has.

[0036] The target material 4 is tin, which is provided in the form of droplets 4 by the supply device 3 within the radiation generation chamber 2. The droplets 4, which emerge from the supply device 3, move within the radiation generation chamber 2 along a predetermined trajectory. 8, which runs approximately in a straight line. In principle, however, the target material 4 can also be a different material, for example, a different metal. Furthermore, the delivery by the delivery device 3 does not have to be in droplet form.

[0037] The first pulsed laser source 5 emits a first pulsed laser beam 9 ; the second pulsed laser source 6 emits a second pulsed laser beam 10.The laser pulses of the first pulsed laser beam 9 and the second pulsed laser beam 10 can, for example, be pre-pulses and main pulses, respectively. The pulsed laser sources 5, 6 are, by way of example but not necessarily, CO2 lasers.

[0038] The first pulsed laser beam 9 and the second pulsed laser beam 10 are fed into the radiation generation chamber 2 by means of the beam guiding device 7. Furthermore, the target material 4 is irradiated with the pulsed laser beams 9, 10 in a focused manner using the beam guiding device 7. For these purposes, the beam guiding device 7 can comprise a plurality of transmissive and / or reflective optical elements (not shown here).

[0039] As a result of the irradiation with one or more laser pulses of the first pulsed laser beam 9 and one or more laser pulses of the second pulsed laser beam 10, the target material 4 is converted into the plasma state and EUV radiation is emitted 11, which is used by a collector mirror 12 which is arranged in the radiation generation chamber 2. The collector mirror 12 has an opening 13 through which the pulsed laser beams 9,10 pass.

[0040] Furthermore, the beam guiding device 7 has a first beam position adjusting device 14 for adjusting the spatial position of the first pulsed laser beam 9 and a second beam position adjusting device 15 for adjusting the spatial position of the second pulsed laser beam 10. The two beam position adjustment devices 14, 15 can be identical or different.

[0041] Finally, the EUV light source 1 additionally comprises a beam position detection device 16 for detecting the spatial position of the first pulsed laser beam 9 and a control device 17 for controlling the spatial position of the first pulsed laser beam 9 via the first beam position adjustment device 14. In the example shown, the beam position detection device 16 is part of the beam guidance device 7. However, this is not necessarily the case. The beam position detection device 16 comprises, by way of example but not necessarily, two position-sensitive sensors not shown here, e.g., a quadrant sensor and / or at least one position-sensitive camera. The control device 17 can be a conventional controller, for example, a PID controller.

[0042] Deviating from the example shown, the EUV light source can also comprise only one pulsed laser source or more than two pulsed laser sources. The target material 4 can also be irradiated with only one or more than two pulsed laser beams. Furthermore, the beam guiding device 7 can also have only one or more than two beam position adjustment devices. When using two or more than two pulsed laser beams, a beam position adjustment device can be provided for all or only for some or one of the pulsed laser beams. The spatial position of more than one pulsed laser beam can also be adjusted via a beam position adjustment device. The beam guiding device does not have to have a beam position adjustment device for each of the pulsed laser beams.Finally, beam position detection devices and corresponding control devices can be provided for all or only for some or only one of the beam position control devices.

[0043] The Fign. 2a,b,c show schematic detailed views of the first beam position adjustment device 14 of the Fig. 1 shown EUV light source 1, which serves to adjust the spatial position of the first pulsed laser beam 9 and four mirrors S1,S2,S3,S4 in the form of two pairs of mirrors P1,P2 The four mirrors S1, S2, S3, S4 are each rotated around exactly one axis A1,A2,A3,A4 Rotatable. The rotation axes A1, A2 of the two mirrors S1, S2 of the first mirror pair P1 are aligned along a first spatial direction n 1 . The rotation axes A3, A4 of the two mirrors S3, S4 of the second mirror pair P2 are aligned along a second spatial direction n 2 . A galvanometer drive G1, G2, G3, G4 is used for each of the four mirrors S1, S2, S3, S4 to rotate them. Alternatively, a different drive can be used to rotate at least one of the four mirrors S1, S2, S3, S4.

[0044] To simplify the description, a Cartesian coordinate system with three coordinate axes is used x,y,z The first spatial direction n 1 is parallel to the x-axis; the second spatial direction n 2 is parallel to the y-axis. In the example shown, the first spatial direction n 1 and the second spatial direction n 2 are therefore perpendicular to each other. However, the first spatial direction n 1 and the second spatial direction n 2 do not necessarily have to be perpendicular to each other.

[0045] In the Fign. 2a,b,c In the example shown, the two mirrors S1, S2 of the first mirror pair P1 directly follow one another in the beam path. Furthermore, the two mirrors S3, S4 of the second mirror pair P2 directly follow one another in the beam path. The first mirror S1 and the second mirror S2 of the first mirror pair P1 are the first and second mirrors in the beam path of the first pulsed laser beam 9, respectively. The first mirror S3 and the second mirror S4 of the second mirror pair P2 are the third and fourth mirrors in the beam path of the first pulsed laser beam 9, respectively.

[0046] In the Fign. 2a,b,c Each of the four mirrors S1,S2,S3,S4 is covered by another of the four mirrors S1,S2,S3,S4: In the Fig. 2a the second mirror S4 of the second mirror pair P2 is covered by the first mirror S3 of the second mirror pair P2. In the Fig. 2b the second mirror S2 of the first mirror pair P1 is covered by the first mirror S1 of the first mirror pair P1. Finally, in the Fig. 2c the first mirror S3 of the second mirror pair P2 is obscured by the second mirror S2 of the first mirror pair P1.

[0047] The pulsed laser beam 9 is also partially obscured. If the pulsed laser beam 9 runs directly behind one of the mirrors S1, S2, S3, S4, it is shown in dashed lines. Furthermore, the two mirror pairs P1, P2 are only partially Fig. 2a and the Fig. 2b identified as they are in the Fig. 2c shown representation partially overlap.

[0048] In the Fig. 2a is also the distance L 1 between the two mirrors S1,S2 of the first mirror pair P1, in the Fig. 2b The distance L2 between the two mirrors S3, S4 of the second mirror pair P2 is shown. In the example shown, the distances L 1 , L 2 are 100 mm. However, the distances L 1 , L 2 can also be larger or smaller and differ from each other. However, the distances L 1 , L 2 are preferably less than 150 mm.

[0049] As from the Fig. 2a The back shows 18 of the first mirror S1 of the first mirror pair P1 an anti-reflective coating 19 for the pulsed laser beam 9. Furthermore, the substrate 20 of the first mirror S1 of the first mirror pair P1 exhibits a low absorption for the pulsed laser beam 9. The material of the substrate 20 is quartz glass in the example shown, but it can also be another material, for example SiC, although SiC is not transmissive at a wavelength of around 1 µm. As can also be seen from the Fign. 2a und 2c also shows the front 21 of the first mirror S1 of the first mirror pair P1 a reflective coating 22 for the pulsed laser beam 9. In the example shown, the other three mirrors S2, S3, S4 also have a reflective coating on their respective front side and an anti-reflective coating on their respective back side for the pulsed laser beam 9, the illustration of which can be found in Fig. 2a,b,c has been omitted for simplification. In the example shown, the material of the respective substrate 20 also exhibits low absorption for the other three mirrors S2, S3, S4.

[0050] In the example shown, the deflection angle α of the pulsed laser beam 9 at all four mirrors S1, S2, S3, S4 at approximately 90°. The deflection angle α is shown here at the second mirror S4 of the second mirror pair P2 in the Fig. 2b However, the deflection angle α can also be greater or less than 90°. Preferably, the deflection angle α lies in an angular range between 30° and 90°, particularly preferably between 60° and 90°.

[0051] In the Fign. 3a , b,c is an alternative variant of the Fign. 2a,b,c shown beam position adjustment device 14 is shown schematically in three detailed views. Deviating from the Fign. 2a,b,c Here, the first spatial direction n 1 is parallel to the propagation direction of the pulsed laser beam 9 entering the beam position adjustment device 14, which corresponds to the y-axis, and the second spatial direction n 2 is parallel to the x-axis. Furthermore, in the Fign. 3a , b,c the first mirror S3 of the second mirror pair P2 is arranged in the beam path in front of the first mirror pair P1 and the second mirror S4 of the second mirror pair P2 is arranged in the beam path after the first mirror pair P1.

[0052] The first mirror S1 and the second mirror S2 of the first mirror pair P1 are the second and third mirrors in the beam path of the pulsed laser beam 9, respectively. The first mirror S3 and the second mirror S4 of the second mirror pair P2 are the first and fourth mirrors in the beam path of the pulsed laser beam 9, respectively.

[0053] In the Fig. 3a the second mirror S4 of the second mirror pair P2 is partially covered by the first mirror S3 of the second mirror pair P2 and the second mirror S2 of the first mirror pair P1 is completely covered by the first mirror S1 of the first mirror pair P1. In the Fig. 3b Furthermore, the two mirrors S1,S2 of the first mirror pair P1 are completely covered by the two mirrors S3,S4 of the second mirror pair P2. The two mirror pairs P1,P2 are also only in the Fig. 3a and the Fig. 3c identified as they are in the Fig. 3bshown representation overlap.

Claims

1. An EUV light source (1), comprising - a provisioning device (3) for providing a target material (4), - at least one pulsed laser source (5, 6) for the emission of at least one pulsed laser beam (9, 10), - a beam guiding device (7) for feeding the at least one pulsed laser beam (9, 10) from the at least one pulsed laser source (5, 6) to a radiation generation chamber (2), and for irradiating the target material (4) with the at least one pulsed laser beam (9, 10) in a focused manner inside of the radiation generation chamber (2), wherein the target material (4) is designed to emit EUV radiation (11) following the irradiation, wherein the beam guiding device (7) has at least one beam position adjusting device (14, 15) for adjusting the spatial position of the at least one pulsed laser beam (9, 10), the adjusting device comprising four mirrors (S1, S2, S3, S4) in the form of two pairs of mirrors (P1, P2), characterized in that each of the four mirrors (S1, S2, S3, S4) is rotatable about precisely one axis of rotation (A1, A2, A3, A4), respectively, and that the axes of rotation (A1, A2) of the two mirrors (S1, S2) of the first pair of mirrors (P1) are aligned along a first spatial direction (n1) and the axes of rotation (A3, A4) of the two mirrors (S3, S4) of the second pair of mirrors (P2) are aligned along a second spatial direction (n2).

2. The EUV light source (1) according to claim 1, characterized in that the first spatial direction (n1) and the second spatial direction (n2) are perpendicular to one another.

3. The EUV light source (1) according to claim 1 or 2, characterized in that the two mirrors (S1, S2) of the first pair of mirrors (P1) follow directly one after the other in the beam path.

4. The EUV light source (1) according to claim 3, characterized in that a distance (L1) between the two mirrors (S1, S2) of the first pair of mirrors (P1) is less than 150 mm cm.

5. The EUV light source (1) according to one of the preceding claims, characterized in that the two mirrors (S3, S4) of the second pair of mirrors (P2) follow directly one after the other in the beam path.

6. The EUV light source (1) according to claim 5, characterized in that a distance (L2) between the two mirrors (S3, S4) of the second pair of mirrors (P2) is less than 150 mm.

7. The EUV light source (1) according to claim 3 or 4, characterized in that the first mirror (S3) of the second pair of mirrors (P2) is arranged prior to the first pair of mirrors (P1) in the beam path and the second mirror (S4) of the second pair of mirrors (P2) is arranged after the first pair of mirrors (P1) in the beam path.

8. The EUV light source (1) according to one of the preceding claims, characterized in that the beam position adjusting device (14, 15) has at least one galvanometer drive (G1, G2, G3, G4) for rotating one of the four mirrors (S1, S2, S3, S4), in each case, about its respective axis of rotation (A1, A2, A3, A4).

9. The EUV light source (1) according to one of the preceding claims, characterized by: - at least one beam position detection device (16) for detecting the spatial position of the at least one pulsed laser beam (9, 10) and - at least one feedback control device (17) for feedback controlling the spatial position of the at least one pulsed laser beam (9, 10) by means of the at least one beam position adjusting device (14, 15).

10. The EUV light source (1) according to one of the preceding claims, characterized in that a redirection angle (α) of the pulsed laser beam (9, 10) on at least one of the four mirrors (S1, S2, S3, S4) lies within an angular range of between 30° and 90°, preferably between 60° and 90°.

11. The EUV light source (1) according to one of the preceding claims, characterized in that a front side (21) of at least one of the four mirrors (S1, S2, S3, S4) has a reflecting coating (22) for the pulsed laser beam (9, 10).

12. The EUV light source (1) according to one of the preceding claims, characterized in that a rear side (18) of at least one of the four mirrors (S1, S2, S3, S4) has an anti-reflecting coating (19) for the at least one pulsed laser beam (9, 10).

13. The EUV light source (1) according to one of the preceding claims, characterized in that a substrate (20) of at least one of the four mirrors (S1, S2, S3, S4) has a low absorption for the at least one pulsed laser beam (9, 10).

14. The EUV light source (1) according to one of the preceding claims, characterized in that the beam guiding device (7) is designed to feed the pulsed laser beam (9, 10) to the beam position adjusting device (14, 15) in a collimated or divergent form.