TW202325452A - Method and device for back reflection protection using laser pulse interference - Google Patents

Abstract

The present application relates to methods and devices for back reflection protection by destructive interference of a returning laser pulse. An advancing laser pulse (30) is split. A first advancing laser pulse portion (30a) opposites a second advancing laser pulse portion (30b), passing through the first beam path (19). The two laser pulse portions (30a, 30b) at least partially superimposed constructively. The advancing laser pulse (30) will then be reflected, and the reflected, returning laser pulse will substantially travel the same distance as the advancing laser pulse (30). The first returning laser pulse portion, however, will pass through the first beam path (19) when the phase shift occurs. At least part of the second advancing laser pulse portion coincides on its way to the laser light source (14), especially when completely destructive superimpose occurs, so as to protect the laser light source (14) from the returning laser pulse.

Description

Method and device for back reflection protection using laser pulse interference

The invention relates to a method and a device for irradiating an object with a laser beam

It is known to irradiate an object with a laser beam, in particular for generating an extreme ultraviolet (EUV) beam. However, a problem with conventional techniques is that reflections, especially from objects, may damage the laser light source.

Although a reflection protection is known, this can generally only be used for intensity-limited laser pulses and only for polarized reflections.

The object of the present invention opposite to this is to deploy a method and a device that make it possible to achieve reflection protection for very high intensity laser pulses and/or protection against non-polarized reflections.

This function is achieved according to the invention by a method according to claim 1 and a device according to claim 11 . Dependents provide further clarification of preferences.

The functions according to the invention are thereby achieved by a method for irradiating an object with a laser beam, wherein the method specifies the following method steps: A) firing forward laser pulses from the laser source; B) splitting the forward laser pulse through the first beam splitter into first forward and second forward laser pulse portions; C) passing the first laser pulse portion through the first beam path; D) Constructive interference of the first advancing laser pulse portion with the second laser pulse portion at the second beam splitter on the path towards the object; E) reflections of forward laser pulses, especially on objects, whereby reentrant laser pulses are generated; F) dividing the reentrant laser pulse into the first reentrant laser pulse part and the second reentrant laser pulse part on the second beam splitter; G) The first reentrant laser pulse part passes through the first beam path, wherein the first reentrant laser pulse part will get a different phase shift from the first forward laser pulse part when passing through the first beam path, in such a way that the forward laser pulse At least part of the laser pulse and the reentrant laser pulse: i) by means of an adjustment element, adjusted to pass through reentrant laser pulses as opposed to passing through forward laser pulses; and/or ii) by means of a frequency offset device (23, 25); H) Destructively interfering with the reentrant first laser pulse portion and the reentrant second laser pulse portion at the first beam splitter on the path towards the laser source.

On the first beam splitter, the forward laser pulse is divided into first and second forward laser pulse parts, the first forward laser pulse part along the first beam path, the second forward laser pulse part along the second The beam path is directed to a second beam splitter. The first forward laser pulse is preferably diverted along the first beam path to the two reflective optical elements, thus resulting in a longer travel distance than the second forward laser pulse. At the second beamsplitter, the first and second forward laser pulse portions overlap again, with the first forward laser pulse portion traveling the distance along the first beam path and the second advancing laser pulse along the second The beam paths traverse different travel distances, preferably by about one or more wavelengths, such that the first and second advancing laser pulse portions constructively interfere at the second beamsplitter towards the object, while at the second A direction, such as the direction of the beam dump, will produce destructive interference.

After the forward laser pulse reflects off the object, the reentrant laser pulse first passes through the second beam splitter. At the second beam splitter, the reentrant laser pulse is split into first and second reentrant laser pulse portions. After passing through the first and second beam paths, the first and second reentrant laser pulse parts will overlap again on the first beam splitter at this time, and without considering the present invention, there will be no construction in the direction of the laser source. sexual, and destructive in other directions. In order to isolate the reentrant laser pulses to protect the laser source, the first and second reentrant laser pulse portions must achieve destructive overlap on the first beam splitter towards the laser source and in other directions, e.g. The directions of the beam dumps overlap constructively.

This is achieved in that the first reentrant laser pulse portion receives a different phase shift when passing through the first beam path than the first forward laser pulse portion when passing through the first beam path. If the phase of the first reentrant laser pulse portion along the first beam path is shifted by 180º compared to the phase of the first forward laser pulse portion, destructive interference will occur on the first beamsplitter in the direction of the laser source , while constructive interference occurs in another direction, for example towards other laser sources.

In this way, the first and second reentrant laser pulse portions overlap destructively in the direction of the laser source, the forward and/or reentrant laser pulses, or the first forward and/or reentrant laser pulse portions pass through an adjustment element.

The tuning element may be disposed along the first beam path between the first forward and return laser pulse portions passing between the two beam splitters. The adjustment element is preferably designed as an active adjustment element in this case. In this case, the adjusting element has in particular a first and a second adjusting position. It is best to plan an active adjustment element, which can be switched to the active state during the passage of the forward first laser pulse part and the return first laser pulse part. Although it is technically challenging, it can provide higher Possibility of protection against reflections of laser pulses of power, independent of the polarization of the back reflection.

Furthermore the tuning element may be configured to vary the wavelength of the first forward and/or reentrant laser pulse portion as it travels through the first beam path. The forward first laser pulse in the first adjustment position of the adjustment element can thereby cover a shorter or longer distance than the reentrant laser pulse in the second adjustment position of the adjustment element. The reentrant first laser pulse portion in the second adjustment position of the adjustment element preferably has a phase offset of 180° + n*360° relative to the forward first laser pulse portion in the first adjustment position of the adjustment element, where n is an integer (including zero). In other words, the wavelength at which the portion of the forward first laser pulse passes along the first beam path between the two beam splitters and the wavelength at which the portion of the reentrant first laser pulse passes along the first beam path between the two beam splitters , there will be a non-integer multiple of the half-wavelength difference between the reentrant and forward laser pulse portions. The wavelength difference is typically a few micrometers.

For the wavelength change, the adjustment element preferably has a piezoelectric element, whereby very fast switching times can be achieved in a constructively simple manner.

It is possible to achieve complete destructive interference on the path of the reentrant laser pulse leading to the laser light source, thereby protecting the laser light source to the greatest extent.

In addition, the adjusting element can be replaced or additionally have an optical element capable of actively adjusting its refractive index, for example, the adjusting element can have a photoelectric crystal for phase shifting, so that in the first adjusting position of the adjusting element, the advancing first light The part of the laser pulse can obtain a different phase shift than the part of the reentrant first laser pulse in the second adjustment position of the adjustment element. In this case, the phase offset in the first adjustment position or in the second adjustment position can also be zero (no phase offset). Preferably, the reentrant first laser pulse portion of the adjustment element in the second adjustment position has a phase offset of 180° + n*360° relative to the forward first laser pulse portion of the adjustment element in the first adjustment position (or vice versa ), where n is an integer (including zero).

The frequency shifting means may additionally or additionally shift the frequency of the reentrant laser pulses and/or the frequency of the forward laser pulses.

At this point the first and second forward laser pulse portions having a different frequency than the first and second reentrant laser pulse portions pass through the first and second beam paths, in other words, the first and second forward laser pulse First and second beam paths having a first frequency are passed through, and first and second reentrant laser pulse portions are passed through first and second beam paths having a second frequency.

At this time, in order to realize the destructive interference toward the laser source direction, the travel lengths along the first and second beam paths must be selected to meet the following two conditions: the travel length of the first reentrant laser pulse along the first beam path The difference between the length, and the length of travel of the second refracted laser pulse along the second beam path must be an integer multiple of one-half the wavelength of the refracted laser pulse at the second frequency plus or minus one. At the same time the difference between the length of travel traveled by the first advancing laser pulse along the first beam path and the length of travel traveled by the second advancing laser pulse along the second beam path must be the wavelength of the advancing laser pulse at the first frequency Integer multiples of .

The frequency shifting means may especially be an acousto-optic modulator (AOM) or a stimulated Brillouin scattering (SBS) mirror. On moving elements such as expanding plasma can also shift the frequency, in particular the object itself can be constructed as moving, expanding plasma on which the laser pulses reflect, allowing the reflection on the object itself to deflect the In this case, one or more frequency offset devices can be arranged in the beam path of the forward and/or reentrant laser pulse.

In particular the frequency offset means can be constructed switchable. If a switchable frequency offset device is used, such as an AOM, the forward laser pulses will pass in this first, for example off, adjustment position, wherein the frequency of the laser pulses is not affected. The folded pulse then passes through the frequency shifting device in a second adjusted position, wherein the frequency of the laser pulse is shifted. The disadvantage is that the frequency-shifted reentrant laser pulses no longer pass through the same optical axis as the forward laser pulses, but the frequency-shifted laser pulses can be diverted again to the first and/or second split, especially by optical elements that refract light device.

The frequency offset means are preferably constructed to offset the frequency of the forward and/or reentrant laser pulses by at most 1000 MHz and at least 20 MHz, preferably between 600 MHz and 30 MHz, especially 40 MHz.

In particular the advancing laser pulse can pass through the first frequency shifting means before passing through the first beam splitter and through the second frequency shifting means before passing through the second beam splitter. The reentrant laser pulse then passes through the second frequency shifting means before passing through the second beam splitter, and through the first frequency shifting means before and after passing through the first beam splitter. In this way it is possible to completely or partially compensate the frequency offset that acts on the second frequency offset means after passing through the second optical splitter. The first frequency shifting means will now shift the frequency of the advancing laser pulse by the same or about the same amount as the second frequency shifting means, only in the opposite direction of sign. It is especially advantageous if the forward laser pulse is amplified in one or more amplifiers after passing through the second beam splitter, so that there will be an optimum range of amplification at one or more frequencies, with different, different from this The frequency of the laser beam will not be amplified to an optimal degree. A comparatively large frequency offset without allowing the forward laser pulses to be amplified less efficiently in subsequent amplifiers.

The greater the amount of frequency shift between the forward laser pulse and the reentrant laser pulse, the first forward and reentrant laser pulse along the first beam path compared to the second forward and reentrant laser pulse along the second The difference in travel distances traveled by the beam paths is smaller, ensuring destructive interference in the direction of the laser source.

The distribution of the laser pulses on the beam splitter is preferably 50% each, that is to say equally divided. The two beam splitters are preferably part of a Mach-Zehnder interferometer. One of the implementation manners is to configure an actively operated adjustment element in the optical path of the Mach-Zehnder interferometer.

The emission of the forward laser beam is preferably a laser beam in the form of a seed source.

The first beam splitter and/or the second beam splitter may be built in the form of a partially transparent mirror, and the beam splitter may be built in the form of a single-sided metallized glass sheet.

Between the first and second beam splitters, especially the first forward and return laser pulse may pass through a telescope or other beam shaping elements, so that the possible irradiation intensity error and/or divergence of the first forward and return laser pulse can be obtained The compensation of the second forward and reentry laser pulses should be ensured in this way that the interference of the first and second forward and reentrant laser pulses is not affected as far as possible in space, while the first and second forward and reentrant Laser pulses interfere as completely destructively and constructively as possible.

In order to receive the part of the laser pulse that interferes constructively, a beam dump can be arranged on the first beam splitter and/or the second beam splitter.

Between the object and the second beam splitter, the laser pulses are preferably passed through an amplifier.

Amplifiers can be built in the form of amplifier chains.

In order to allow more time for the switching of the adjustment element, a delay path can be planned between the second beam splitter and the object.

A particularly preferred embodiment of the invention generates an advancing laser pulse EUV beam whereby an object can be built in the form of a tin can, wherein the expanding plasma is stimulated by the advancing laser pulse resulting in the emission of the EUV beam.

Functions consistent with the invention continue to be achieved by apparatus for launching objects, in particular for performing the methods described herein. The device has the following characteristics: a) a laser light source; b) a first beam splitter for splitting the forward laser pulse into a first forward laser pulse portion and a second forward laser pulse portion; c) a first beam path through which the first forward laser pulse portion passes; d) a second beam splitter for at least partial constructive interference between the first advancing laser pulse portion and the second advancing laser pulse portion on their way to and from the object; e) Objects for reflecting forward laser pulses and generating reentrant laser pulses; wherein the second beam splitter is configured to split the reentrant laser pulse into a first reentrant laser pulse portion and a second reentrant laser pulse portion; The apparatus configured therein has an adjustment element and/or a frequency offset device, on which the first reentrant laser pulse portion and the first forward laser pulse portion produce a different frequency offset, and The part of the reentrant first laser pulse will at least partially destructively interfere with the part of the reentrant second laser pulse on the first beam splitter on the way to the laser light source.

An adjusting element can in particular be arranged along the first beam path between the first and the second beam splitter. In particular the adjustment element can be switched between a first and a second adjustment position, in which case the adjustment element can be configured to vary the travel length of the first forward and return laser pulse portion along the first beam path. In addition, the adjusting element preferably has a piezo element, whereby very fast switching times can be achieved with constructive simplicity, in particular the adjusting element can be designed to vary the stroke length of the first beam path by half Or the half-wavelength of the first forward and retrace laser pulses of non-integer multiples.

Alternatively or additionally, the adjusting element can also be provided with an optical element, in particular whose refractive index can be actively controlled to be changed, for example an optoelectronic phase modulator. This adjustment element is preferably also arranged along the first beam path, so that the first reentrant laser pulse part can be phase shifted differently from the first forward laser pulse part, in particular the optical element can be constructed to align the first The part of the reentrant laser pulse moves 180º + n*360º (or vice versa), where n is an integer (including zero).

The frequency shifting device can be implemented as an acousto-optic modulator (AOM), a stimulated Brillouin scattering (SBS) mirror and/or a moving element such as an expanding plasma.

It is also possible for the device to have a plurality of frequency shifting means, in particular it is possible to have a first frequency shifting means (arranged towards the beam direction of the advancing laser pulse) before the first beam splitter, and a second frequency shifting means Configured after the second beam splitter.

The first and second frequency shifting means are then specifically designed to increase the frequency of the advancing laser pulses before the first beam splitter by a certain amount and to decrease it after the second beam splitter, in particular by the same or almost the same amount. The advantage of this is that a comparatively large frequency difference between the forward and return laser pulses can be chosen without the forward laser pulse being amplified with lower efficiency in the following amplifiers. In addition, the greater the frequency offset of the forward laser pulses compared to the reentrant laser pulses, the greater the frequency of the first forward and reentrant laser pulses along the first beam path than the second forward and reentrant laser pulses along the first beam path. A small difference in run length is selected between the runs traveled along the second beam path.

At this time, one or more telescopes can be arranged in the first beam path, so that the error and/or divergence of the beam intensity that may occur in the first forward and return laser pulse can be compensated by the second forward and return laser pulse. In this way it is ensured that the interference of the first and second forward and reentrant laser pulses is as spatially unaffected as possible and that the first and second forward and reentrant laser pulses are as completely destructive and constructive as possible put one's oar in.

The device may have an amplifier between the second splitter and the object, in particular possibly one or several _CO2 amplifiers connected in series.

In case the object itself is built as a plasma form frequency shifting device, the device can also be placed between the amplifier and the object.

The device can have at least one mirror, in particular a plurality of mirrors, for deflecting the laser beam. In particular the first forward and return laser pulses may be directed through the first beam path by a pair of mirrors.

The object is preferably constructed to emit the EUV beam, preferably the object is constructed in the form of a tin can.

Other advantages of the invention are provided in the description and drawings. Likewise, the features mentioned above and those that will be further implemented can also be applied individually or in multiple arbitrary combinations according to the present invention. The embodiments shown and described are not final but have more of an exemplary nature to illustrate the invention.

Figure 1a shows a device 10 for illuminating an object 12, the device 10 having a laser light source 14, a first beam splitter 16, a second beam splitter 18, a first beam path 19, an adjustment element 20, a A first beam dump 22 , a second beam dump 24 and an amplifier 26 .

The beam splitter 16,18 is preferably built into a single-sided metallized glass plate, allowing the reflected laser beam to obtain a phase jump or no phase jump depending on its incident surface on the beam splitter 16,18, and this beam splitter is called Considered to be a Mach-Zehnder interferometer architecture.

The laser light source 14 emits a laser beam 28, the laser beam 28 has a forward laser pulse 30, and the forward laser pulse 30 is divided into a first forward laser pulse part 30a and a second forward laser pulse part 30a at the first beam splitter 16. Radiation pulse portion 30b. The first forward laser pulse part 30a is guided to the second beam splitter 18 through the first beam path 19 and the adjustment element 20, whereas the second forward laser pulse part 30b is guided to the second beam splitter 18 without through the adjustment element 20.

The first forward laser pulse part 30a gets a phase jump of 180° or Pi according to its reflection on the first beam splitter 16, whereas the second forward laser pulse part 30b does not get it on the first beam splitter 16. phase jump.

A portion of the first forward laser pulse portion 30a passes through the second beam splitter 18 to the second beam dump 24 without a phase jump, and a portion of the first forward laser pulse portion 30a is reflected at the second beam splitter 18 to the amplifier 26 , thus obtaining a phase jump of 180º.

The second forward laser pulse portion 30b passes through the first beam splitter 16 without a phase jump, a portion of the second forward laser pulse portion 30b then passes through the second beam splitter 18 to the amplifier 26 without a phase jump, and a portion to The second beam dump 24, again, has no phase jumps.

From the second beam splitter 18 to the amplifier 26, the first forward laser pulse portion 30a and the second forward laser pulse portion 30b thus constructively interfere, while from the second beam splitter 18 to the second beam path 24 is the first The forward laser pulse portion 30a and the second forward laser pulse portion 30b interfere destructively such that at least a portion of the rejoined forward laser pulse 30 is directed to the amplifier 26 .

In the amplifier 26 , which is preferably implemented as an amplifier chain, the laser pulse 30 is amplified and then reaches the object 12 .

In the previous case the object 12 was implemented in the form of a tin can in which a plasma was generated by advancing laser pulses 30 resulting in the emission of an extreme ultraviolet (EUV) beam 32 .

FIG. 1 b shows the device 10 with reflected laser pulses 34 reflected by the object 12 . The reentrant laser pulse 34 is divided into a first reentrant laser pulse portion 34a and a second reentrant laser pulse portion 34b at the second optical splitter 18, and the first reentrant laser pulse portion 34a obtains a 180° phase jump at the second optical splitter 18 , otherwise, the second reentrant laser pulse portion 34b does not obtain a phase jump in the second beam splitter 18 .

The first refracted laser pulse portion 34a passes through the adjustment element 20 along the first beam path 19 on its way to the first beam splitter 16, whereas the second refracted laser pulse portion 34b passes through the adjustment element 20 on its way to the first beam splitter 16. The adjustment element 20 will not pass on the path.

A portion of the first reentrant laser pulse portion 34a passes through the first beam splitter 16 to the first beam dump 22 without phase jumping. A portion of the first reentrant laser pulse portion 34a is reflected at the first beam splitter 16 towards the laser light source 14, thereby obtaining a phase jump of 180°.

Part of the second reentrant laser pulse portion 34b goes to the laser source 14 through the first beam splitter 16 without phase jumping, and part of it goes to the first beam dump 22 without phase jumping.

Therefore, it can basically be expected that the first reentrant laser pulse portion 34a and the second reentrant laser pulse portion 34b will constructively interfere from the first beam splitter 16 to the laser light source 14, and produce destructive interference to the first beam dump 22. interference, the laser light source 14 is thus damaged.

The adjustment element 20 will thus switch from its first adjustment position shown in figure 1 a for the forward laser pulse 30 to its second adjustment position shown in figure 1 b for the reentrant laser pulse 34, whereby the adjustment element 20 will perform a reentry The path length of the laser pulse 34 is changed compared to the advancing laser pulse 30 , and the adjustment element 20 may also have a piezoelectric element.

At this time, the change of the stroke length of the adjustment element 20 will be defined as a phase shift of 180º+n*360º (n is an integer, where n may be 0) between the reentrant laser pulse 34 and the forward laser pulse 30, so the first reentrant Destructive interference occurs between the laser pulse portion 34 a and the second reentrant laser pulse portion 34 b going from the beam splitter 16 to the laser light source 14 , while constructive interference occurs when traveling to the first beam dump 22 . The laser light source 14 is protected against reentrant laser pulses 34 .

Figures 2a and 2b correspond to the device 10 in Figures 1a, 1b, but the adjustment element 20 shown in Figures 2a, 2b has a photoelectric crystal 36 for varying the first refracted laser pulse 34 relative to the first The phase of the laser pulse 30 is advanced.

For Figures 1a, 1b and 2a, 2b, it should be noted that the first laser pulse part 30a, 34a and the second laser pulse part 30b, 34b have the same stroke to the possible phase shift, and the stroke in the figure is only Drawn differently for display reasons, so the strokes can be arbitrarily chosen to be the same length at the ends.

The device 10 in Figures 3, 4 and 5 is equivalent to the device 10 shown in Figures 1a and 1b and 2a and 2b, but the device 10 in Figures 3, 4 and 5 is not along the first beam path 19 The adjustment element 20.

For this reason, there is a frequency shifting device 23 planned between the second beam splitter 18 and the object 12 in Figure 3, and the frequency of the forward laser pulse will be shifted by the frequency shifting device 23 after passing through the second beam splitter 18 . The length of travel along the first beam path 19 and along the second beam path 21 will be selected such that the second forward and return laser pulse portions 30b, 34b between the two beam splitters 16, 18 pass through the travel, allowing The frequency-shifted first and second reentrant laser pulse portions 30a, 30b destructively interfere in the direction of the first beam splitter 16 toward the laser source 14, while the frequency-shifted first and second forward laser pulses The radiation pulse portions 34a, 34b travel to the object 12 and constructively interfere.

In Figure 4 the object 12 is constructed as a frequency shifting device 23, such as an expanding plasma, the frequency of the forward laser pulse 30 is shifted on the object 12, and the reentrant laser pulse 34 has been directed towards the laser before passing through the amplifier 26. The direction of the radiation source 14 interferes destructively.

Fig. 5 shows the apparatus 10 with two frequency shifting devices 23, 25, one is arranged between the laser source 14 and the first beam splitter 16, and the other is between the second beam splitter 18 and the object 12, at this time The frequency of the advancing laser pulse 30 is shifted by a certain amount before passing through the first beam splitter 16 and shifted back by the same amount after passing through the second beam splitter 18 . After reflection on the object 13 , the frequency of the reentrant laser pulse 34 is likewise shifted by a certain amount before passing through the second beam splitter 18 and likewise shifted back after passing through the first beam splitter 16 . Amplifier 26 may be driven at a frequency driven by laser pulses generated in laser light source 14 .

In the embodiments according to Figures 3, 4 and 5, the first and second laser pulse portions (30a, 30b, 34a, 34b) travel different travel distances along the first and second beam paths 19, 21 Long, both beam paths 19, 21 are planned so that compared to the pulse length, the time required for the first laser pulse portion (30a, 34a) to pass through the first beam path 19 is the same as the time required for the second laser pulse portion (30b, 34b) The time difference in the time required to traverse the second beam path 21 is very short, thus ensuring that only a small fraction of the two laser pulse parts (30a, 30b, 34a, 34b) do not interfere.

Looking at all figures of the drawings, the invention generally relates to a reflection protection through destructive interference of refracted laser pulses 34 . A forward laser pulse 30 is divided into a first forward laser pulse portion 30a and a second forward laser pulse portion 30b through a first beam path 19 . The two laser pulse portions 30a, 30b will constructively overlap at least in part, after which the forward laser pulse 30 will be reflected, and the reflected reentrant laser pulse 34 will travel substantially the same distance as the forward laser pulse 30, but reentrant When the first laser pulse part 34a passes through the first beam path 19, it will overlap at least partly with the reentrant second laser pulse part 34b during the journey to the laser light source 14, so that the laser light source 14 The laser pulse 34 is protected against reentry.

10: Equipment 12: Object 14: Laser light source 16: The first beam splitter 18: Second beam splitter 19: First beam path 20: Adjustment components 21: Second beam path 22: The first beam collector 23: Frequency offset device 24: Second beam dump 25: Frequency offset device 26: Amplifier 28:Laser Beam 30: Forward Laser Pulse 30a: first laser pulse part 30b: Second laser pulse part 32: EUV Beam 34:Foldback Laser Pulse 34a: First laser pulse part 34b: Second laser pulse part 36: photoelectric crystal

Fig. 1a: A schematic diagram showing the apparatus of the first embodiment, with an element for adjusting the stroke length when advancing the laser pulse.

Figure 1b shows the device in Figure 1a when the laser pulses are folded back.

Fig. 2a shows a schematic diagram of a second embodiment of the apparatus with a refractive index modulating element as the laser pulse advances.

Figure 2b shows the device in Figure 2a when the laser pulses are folded back.

Figure 3 shows a schematic diagram of an apparatus of a third embodiment, with a frequency offset device attached.

Figure 4 shows a schematic diagram of a fourth embodiment of the apparatus, showing a frequency shifting device on an irradiated object.

Fig. 5 shows a schematic diagram of a fifth embodiment, with a frequency shifting device preceded by an interferometer, and a frequency shifted device reared by an interferometer.

10: Equipment

12: Object

14: Laser light source

16: The first beam splitter

18: Second beam splitter

19: First beam path

20: Adjustment components

22: The first beam collector

24: Second beam dump

26: Amplifier

28:Laser Beam

30: Forward Laser Pulse

30a: first laser pulse part

30b: Second laser pulse part

32: EUV Beam

Claims (15)

A method for irradiating an object (12) with a laser beam (28), the method comprising: A) an advancing laser pulse (30) emitting a laser beam (28) from a laser light source (14); B) splitting the forward laser pulse (30) into a first forward laser pulse portion (30a) and a second forward laser pulse portion (30b) through a first beam splitter (16); C) passing the first forward laser pulse (30a) through the first beam path (19); D) interference of the first laser pulse portion (30a) and the second laser pulse portion (30b) occurs through the second beam splitter (18); E) at least a portion of the rejoined advancing laser pulse (30) is reflected off the object (12), thereby producing a reentrant laser pulse (34); F) dividing the reentrant laser pulse (34) into a first reentrant laser pulse portion (34a) and a second reentrant laser pulse portion (34b) through the second beam splitter (18); G) The first reentrant laser pulse portion (34a) passes through the first beam path (19), wherein the first reentrant laser pulse portion (34a) gets a different phase shift than the first forward laser pulse portion (30a) , the way is at least a part of the forward laser pulse (30) and the reentrant laser pulse (34): i) by means of an adjustment element (20), the passage of the reentrant laser pulse (34) is adjusted relative to the passage of the forward laser pulse (30); and/or ii) by means of a frequency offset device (23, 25); H) At least a part of the first laser pulse portion (34a) of the reentrant laser pulse (34) meets with the second laser pulse portion (34b) of the reentrant laser pulse (34), passing through the first beam splitter (16) To a laser light source (14), where the first laser pulse portion (34a) destructively interferes with the second laser pulse portion (34b). The method according to claim 1, wherein in method steps C) and G), the forward and reverse first laser pulse parts (30a, 34a) are switched to a first adjustment position and a first adjustment position via an adjustment element (20) in method steps C) and G). Second adjustment position, wherein the adjustment element (20) passes the first advancing laser pulse portion (30a) in the first adjustment position in method step C) and the first advancing laser pulse portion (30a) in the second adjustment position in method step G). The reentrant laser pulse portion (34a) passes. The method according to claim 1 or claim 2, wherein the adjustment element (20) is additionally configured to adjust the length of travel along the first beam path (19), passing through the first adjustment position of the adjustment element (20) The forward first laser pulse portion (30a) of the first beam path (19) travels a shorter or longer distance than the reentrant first laser pulse (34a) at the second adjustment position of the adjustment element (20) , where the length of travel passed by the forward first laser pulse (30a) and the length of travel passed by the reentrant first laser pulse portion (34a), in particular, there will be a non-integer multiple of one half of the reentrant laser pulse portion (34a) difference in wavelength. Method according to any one of the preceding claims, wherein the adjustment element (20) has a piezoelectric element for changing the stroke length between the first adjustment position and the second adjustment position. The method according to any one of the preceding claims, wherein the adjustment element (20) has a photoelectric crystal (36) for phase shifting, allowing the advancing first laser pulse portion (30a) passing through the adjustment element (20) In the first adjustment position of the adjustment element (20) a different phase shift is obtained than in the second adjustment position of the adjustment element (20) of the folded first laser pulse portion (34a), wherein the phase shift corresponds in particular to A non-integer multiple of the half-wavelength of the reentrant laser pulse portion (34a). The method according to any one of the preceding claims, wherein the forward laser pulse (30) precedes method step B) and/or after method step D) and/or the reentrant laser pulse (34) precedes method step E) Before and/or after method step H), passing through a frequency shifting device (23, 25), in particular an acoustic optical modulator (AOM), a stimulated Brillouin scattering (SBS) mirror and/or an expansion Plasma. The method according to any one of the preceding claims, wherein the frequency offset means (23, 25) offset the frequency of the forward laser pulse (30) and/or reentrant laser pulse (34) by at most 1000 MHz and at least 20 MHz, preferably less than 100 MHz. The method according to any one of the preceding claims, wherein the forward laser pulse (30) is guided into an amplifier (26) in method step D), and the return laser pulse (34) is guided in method step F ) from the amplifier (26) to the second splitter (18). The method according to any one of the preceding claims, wherein in method step D) the advancing laser pulse (3) takes place constructively in the first laser pulse part (30a) and the second laser pulse part (30b) After the interference, a delay path is traversed by which the reentrant laser pulse ( 34 ) in method step E) is also traversed. The method according to any one of the preceding claims, wherein advancing laser pulses (30) are used to generate an extreme ultraviolet (EUV) beam (32). A device (10) for irradiating an object (12), in particular configured to emit an EUV beam, using a laser beam (28), in particular for carrying out the method according to any one of the preceding claims, having the following characteristics : a) a laser light source (14); b) a first beam splitter (16) is used to divide the forward laser pulse (30) from the laser light source (14) into a first forward laser pulse part (30a) and a second forward laser pulse part ( 30b); c) a first beam path (19) through which the first laser pulse portion (30a) passes; d) a second beam splitter (18) on which the first laser pulse portion (30a) constructively interferes at least in part with the second laser pulse portion (30b); e) an object (12) for reflecting forward laser pulses (30) and generating reentrant laser pulses (34); Wherein the reentry laser pulse (34) can be divided into a first reentry laser pulse (34a) and a second reentry laser pulse part (34b) on the second beam splitter (18); wherein the apparatus has an adjustment element (20) and/or a frequency shifting device (23, 25), additionally configured to generate and advance laser pulses in a first laser pulse portion (34a) of a reentrant laser pulse (34) (30) different phase shifts of the first laser pulse portion (30a); and Wherein the first reentrant laser pulse part (34a) destructively interferes with at least part of the second reentrant laser pulse part (34b) on the first beam splitter (16) leading to the laser light source (14). The device according to claim 11, wherein the adjustment element (20) is switchable into a first and a second adjustment position. The device according to claim 11 or 12, wherein the adjustment element (20) is arranged along the first beam path (19) such that the advancing first laser pulse portion (30a) passing through the first beam path (19) is adjusted In the first adjustment position of the element (20) travels a shorter or longer distance than the reentrant first laser pulse (34a) in the second adjustment position of the adjustment element (20), and/or the adjustment element (20) travels along is arranged along the first beam path (19), and has a photoelectric crystal (36) for phase shifting, so that the advancing first laser pulse portion (30a) passing through the first beam path is at the first A different phase shift results in the adjusted position than in the second adjusted position of the adjusted element ( 20 ) compared to the folded-back first laser pulse portion ( 34 a ). The device according to any one of claims 11 to 13, wherein the frequency shifting means (23, 25) are implemented as an acousto-optic modulator (AOM), a stimulated Brillouin scattering (SBS) mirror and/or Moving object, wherein it can be seen that the frequency shifting means (23, 25) are arranged in the beam direction of the advancing laser pulse (30), in particular after the second beam splitter (18) and/or after the first beam splitter ( 16) before. Apparatus according to any one of claims 11 to 14, wherein the apparatus (10) has an amplifier (26) allowing the forward laser pulse (30) to be directed to the amplifier after the second beam splitter (18) , and direct the reentrant laser pulse (34) from the amplifier to the second beam splitter (18).