Method for generating an EUV light beam, EUV driver laser for generating an EUV light beam and use

Abstract

A method for generating an EUV light beam (12) by converting a target material (36) into a plasma state using a plurality of laser beams (30), the method comprising: generating the plurality of laser beams (30) using a plurality of laser beam sources (20); and converting the target material (36) into the plasma state by irradiating the target material (36) with the plurality of laser beams (30). During the irradiation of the target material (36) with the plurality of laser beams (30), each laser beam (30) strikes the target material (36) for a time period (46). The time periods (46) overlap within a time interval (48).

Description

[0001] The invention relates to a method for generating an EUV light beam, an EUV driver laser for generating an EUV light beam and a use of the method and / or the EUV driver laser for the fabrication of an integrated circuit.

[0002] Extreme ultraviolet (EUV) light beams enable the precise and highly accurate imaging of fine structures, which is why EUV light beams are frequently used in lithography, a process that can therefore be called EUV lithography. Due to the advantage of precise and highly accurate imaging of fine structures, EUV lithography is suitable for the production of integrated circuits, especially for the manufacture of microchips.

[0003] An EUV light beam can be generated, for example, using an EUV driver laser, which typically comprises a gas laser and a target chamber. The target material of the EUV driver laser can be arranged within the target chamber. The gas laser can be configured to generate and / or amplify a laser beam. The laser beam can be directed at the target material, and upon impact, it can convert the target material into a plasma state such that the EUV light beam is generated by the target material.

[0004] The pulse energy required to convert the target material into the plasma state can typically be several hundred millijoules (mJ). At repetition rates in the range of 10 kHz to 100 kHz, particularly 40 kHz to 60 kHz, a laser beam with an average power of several kilowatts (kW) may be required. Therefore, CO2 lasers with an average power of over 30 kW are frequently used.

[0005] With a laser beam having an average power of over 30 kW and a pulse energy of over 200 mJ, all optics and components in the beam path, over which the laser beam is guided or through, must usually meet particularly high requirements to prevent damage by the laser beam.

[0006] If the optics and components are damaged, or if the CO2 laser fails, the EUV driver laser cannot generate an EUV light beam. Since EUV driver lasers are often integrated into complex systems, their failure results in high costs.

[0007] The invention aims to provide a method for generating an EUV light beam, an EUV driver laser, and a use of the method and / or the EUV driver laser for the manufacture of an integrated circuit, each of which enables the generation of an EUV light beam with short downtimes.

[0008] The invention solves this problem by providing a method with the features of claim 1, an EUV driver laser with the features of claim 10, and a use with the features of claim 14. Advantageous embodiments and further developments of the invention are set forth in the dependent claims.

[0009] A method according to the invention serves to generate an EUV light beam by converting a target material into a plasma state using a plurality, for example 3, 8, 15 or 20, of laser beams. The method comprises: generating the plurality of laser beams; and converting the target material into the plasma state by irradiating the target material with the plurality of laser beams. During the irradiation of the target material with the plurality of laser beams, each laser beam strikes the target material for a specific duration. Within a time interval, the durations overlap or superimpose on one another.

[0010] Advantageously, this allows the use of a single or multiple laser beam sources for generating the EUV light beam, all of which are commercially available. Commercially available laser beam sources are typically readily available, meaning that if one fails, a replacement can be quickly procured and replaced. This minimizes downtime during which the EUV light beam cannot be generated.

[0011] The EUV light beam can have a wavelength with a value in the range of 5 nm (nanometers) to 140 nm, in particular 10 nm to 120 nm.

[0012] The target material can be a metal, for example, tin. The target material can be in the form of droplets, for example, tin droplets. Forming the target material as tin droplets can be particularly advantageous for generating an EUV light beam due to a high yield of EUV radiation.

[0013] The target material can be arranged in a target chamber. In particular, the target material can be arranged in an interior space of the target chamber. The target chamber can be designed as a vacuum chamber. The target chamber can be filled with hydrogen at a pressure of 1 Pa (Pascal) to 10 -15 Pa, preferably 10 -3 Pa up to 10 -12 Pa, be filled. Alternatively, the target chamber can be in a vacuum state. In this vacuum state, a vacuum can exist within the interior of the target chamber.

[0014] Another aspect of the method is that it enables the use of laser beams with such low average power and / or low pulse energy for generating the EUV light beam that a single or multiple solid-state lasers can be used, thereby increasing the efficiency of EUV light beam generation. In particular, this can improve the energy efficiency of EUV light beam generation. In other words, the laser beam source(s) can be configured as a solid-state laser. The laser beam source(s) can preferably be configured as a fiber laser or a disk laser. Alternatively, the laser beam source(s) can be configured as a slab laser.

[0015] Preferably, a plurality of laser beam sources are provided for generating the plurality of laser beams. Each laser beam source can generate a single laser beam. The number of laser beam sources can be equal to the number of laser beams. The laser beam sources can be configured separately from one another. The laser beam sources can be operated independently of one another, in particular generating the laser beams independently of one another.

[0016] The laser beams can be designed to convert the target material into a plasma state, at least within the specified time interval. In other words, the target material can be irradiated by the laser beams in such a way that it is converted into a plasma state, at least within the specified time interval.

[0017] The majority of laser beams can be a multitude of laser beams. Each laser beam can propagate along a beam path. The beam paths of the majority of laser beams can differ from one another. Immediately before impacting the target material, the beam paths can have such a profile that a surface of a circular cone, particularly a straight one, is bounded by the beam paths. Each beam path can be a generatrix of the circular cone, particularly a straight one, immediately before impacting the target material. Such an arrangement of the beam paths allows for a particularly compact design.

[0018] The laser beams can be identical in shape. In particular, the laser beams can have the same beam properties. Each laser beam can have a wavelength in the range of 800 nm to 3000 nm, preferably 1900 nm to 2400 nm.

[0019] Every laser beam can be a pulsed laser beam. In particular, every laser beam can be formed by a single laser pulse. Therefore, a laser beam can also be understood to be a laser pulse. Alternatively, every laser beam is formed by a plurality of laser pulses. Each laser pulse can have a pulse duration with a value in the range of 10 fs (femtoseconds) to 800 ns (nanoseconds), in particular 1 ns to 100 ns. The laser pulses of the laser beams can be identical. In particular, the pulse duration and / or the repetition rate of the laser beams can be the same.

[0020] Each laser beam can have an average power in the range of 1000 W (watts) to 10000 W. Each laser beam can have a repetition rate of 50 kHz to 100 kHz.

[0021] The process can involve, after generating the majority of laser beams, focusing them onto the target material using a circular or ring-shaped arrangement of focusing elements, for example, in the form of lenses and / or curved mirrors. The number of focusing elements and the number of laser beams can be the same. Alternatively, the laser beams can be focused onto the target material using a single focusing element.

[0022] Each time period can describe the duration of irradiation of the target material with the laser beam.

[0023] Because the durations within the time interval overlap, the target material can be irradiated by all laser beams simultaneously during that interval. In other words, the majority of laser beams can irradiate the target material simultaneously during the time interval.

[0024] The time interval can have a value in the range of 10 fs to 800 ns, in particular 1 ns to 100 ns.

[0025] Another aspect of the method is that the pulse energy required to transition the target material into the plasma state only occurs at the target material itself during the specified time interval. Therefore, the requirements for the components through which the majority of laser beams pass can be reduced. Consequently, this method allows for the use of cost-effective optical components to focus the majority of laser beams onto the target material.

[0026] In a further development of the method, irradiating the target material with the majority of laser beams involves spatially superimposing the majority of laser beams at the location of the target material, particularly at a surface of the target material. This allows an intensity to be achieved at the location of the target material that is necessary to convert the target material into the plasma state.

[0027] Each laser beam can strike the target material in a specific area. These areas can overlap or superimpose, at least partially. Each area can be a region of the target material's surface.

[0028] In a further development of the method, each laser beam source is configured to receive a signal, in particular a trigger signal, and to generate the laser beam depending on the received signal. Generating multiple laser beams involves receiving signals from one or more laser beam sources. In the case of multiple laser beam sources, the signals are received by the majority of the laser beam sources with time differences. These time differences cause the durations for the time interval to overlap. In particular, this allows different travel times of the laser pulses from the laser beam sources to the target material to be balanced or compensated for by means of these time differences.If only a single laser beam source is available, the majority of laser beams can be generated by splitting an original laser beam produced by the laser beam source into several partial beams and amplifying them individually.

[0029] Each signal can be called a trigger signal. The number of signals can correspond to the number of laser beam sources. Each signal can be assigned to a specific laser beam source. This allows each laser beam source to be controlled independently of the others.

[0030] In a further development of the procedure, the process involves specifying a target time interval. Irradiating the target material with multiple laser beams includes adjusting the time interval to the specified target interval. This ensures that the laser beams irradiate the target material simultaneously for the duration of the target time interval.

[0031] Specifying the target time interval can include specifying a length or duration of the target time interval.

[0032] Controlling the time interval can involve changing or adjusting the time differences.

[0033] The target time interval can have a value that is equal to or less than 95%, 90% or 85% of a time duration.

[0034] In a further development of the method, irradiating the target material with the plurality of laser beams comprises coherent superposition or non-coherent superposition of the plurality of laser beams, in particular only at the location of the target material. Coherent superposition of the plurality of laser beams at the location of the target material is preferred.

[0035] Advantageously, coherent superposition, due to constructive interference, allows for higher power, particularly higher peak pulse power, at the target material compared to non-coherent superposition. Furthermore, non-coherent superposition simplifies the design of an EUV driver laser compared to coherent superposition because phase matching between the laser beams is not required.

[0036] In a further development of the method, each laser beam is coupled into a waveguide, in particular a fiber-optic waveguide, and coupled out of the waveguide before striking the target material. Advantageously, the use of waveguides, for example in the form of optical fibers or waveguide rods, eliminates the need for costly optical components for beam guidance. Another advantage is that the waveguides enable a relatively robust setup for generating the EUV light beam.

[0037] One or more laser beam sources can be configured as fiber-coupled sources. This allows for the rapid replacement of a single laser beam source or a single laser beam source among multiple sources if it malfunctions. Specifically, the waveguide connected to an output of the malfunctioning laser beam source can be connected to an output of a functioning laser beam source. By simply swapping the waveguide, a malfunctioning laser beam source can be replaced quickly, especially in a short amount of time. If necessary, functioning laser beam sources can be kept on hand so that, should a laser beam source fail, it can be replaced by swapping the waveguide.

[0038] The waveguides can be configured separately. Each waveguide can be assigned to a laser beam source. The number of waveguides can equal the number of laser beam sources.

[0039] If multiple laser beam sources are present, each laser beam can be coupled into the waveguide, especially immediately after leaving the laser beam sources.

[0040] In a further development of the method, the majority of laser beams are arranged in a circular pattern relative to each other immediately before striking the target material. This allows for a compact design while simultaneously achieving high intensity on the target material.

[0041] The distance between two adjacent laser beams can decrease as the distance to the target material decreases.

[0042] The term "immediately before impact" can be understood to mean a distance from the target material of no more than 5 cm (centimeters).

[0043] In a further development of the method, the majority of laser beams are guided through a single focusing lens to focus onto the target material. This can simplify the setup for generating the EUV light beam. Another advantage is that it can eliminate the number of optical components and reduce the adjustment effort. The focusing lens can be made of quartz glass.

[0044] In a further development of the method, the EUV light beam is guided over a collector device. The majority of laser beams are guided over or through the collector device. This allows for a more compact design.

[0045] The collector device can be configured to focus the EUV light beam emitted by the target material. The collector device can be a single piece. The collector device can have a concave EUV mirror. The target material can be placed at a focal point of the concave EUV mirror. The EUV mirror can be highly reflective for a wavelength of the EUV light beam, with a reflectance of over 60%, in particular over 75%, preferably over 90%, and more preferably over 95%.

[0046] The concave EUV mirror can have multiple openings. Each laser beam can pass through one opening before striking the target material. The number of openings can be equal to the number of laser beams. Alternatively, instead of openings, the collector device can include a laser beam mirror or deflection mirror for directing the laser beams onto the target material. The laser beam mirror can be concave. The laser beam mirror can surround the EUV mirror, in particular, it can be circumferential. The laser beam mirror can be a single piece or formed from multiple segments. If the laser beam mirror is formed from multiple segments, the number of segments can be equal to the number of laser beams. In particular, each laser beam can be associated with a segment that directs the laser beam onto the target material.

[0047] An EUV driver laser according to the invention is configured for generating an EUV light beam by converting a target material into a plasma state using a plurality of laser beams. The EUV driver laser comprises a plurality of laser beam sources, the target material, a target chamber, and a control unit. The plurality of laser beam sources are configured for generating the plurality of laser beams. The target material for generating the EUV light beam is arranged in the target chamber. The control unit is configured to send a signal to the laser beam sources. Each laser beam source is configured to receive the signal and generate the laser beam depending on the signal. The EUV driver laser is configured to perform a previously described method. The previously given description of the method can apply to identical or functionally equivalent features of the EUV driver laser.

[0048] The control unit may include an electrical computing unit, in particular a computer and / or a microcontroller.

[0049] In a further development of the EUV driver laser, the EUV driver laser features a collector device. The collector device is arranged relative to the target material such that the EUV light beam is guided over the collector device. Alternatively, the collector device can be arranged relative to the target material such that the majority of laser beams are guided over the collector device or the majority of laser beams are guided through the collector device.

[0050] In a further development of the EUV driver laser, the EUV driver laser features a plurality of waveguides. These waveguides are arranged such that the majority of laser beams are guided, at least partially, to the target material via the multiple waveguides.

[0051] One use according to the invention relates to the use of a previously described method and / or a previously described EUV driver laser for the fabrication of an integrated circuit.

[0052] Further advantages and advantageous embodiments of the invention can be seen from the figures, their description, and the claims. All features disclosed in the figures, their description, and the claims can be essential to the invention, both individually and in any combination. The figures show: Fig. 1 A schematic representation of an EUV driver laser with a collector device for focusing an EUV light beam, Fig. 2 a schematic sectional view of a plurality of laser beams of the EUV driver laser along a section line II-II according to Fig. 1, Fig. 3 a schematic representation of a time course of the irradiation of a target material of the EUV driver laser with the majority of laser beams, Fig. 4 a schematic representation of the target material during irradiation with the majority of laser beams, Fig. 5 a schematic representation of a further embodiment of a collector device, Fig. 6 a schematic sectional view of the collector assembly of Fig. 5, Fig. 7 a schematic representation of another embodiment of a collector device, Fig. 8 a schematic representation of another embodiment of a collector device, Fig. 9 a schematic representation of a further embodiment of a collector device, and Fig. 10 a schematic representation of another embodiment of a collector device.

[0053] Fig. Figure 1 shows an EUV driver laser 10 for generating an EUV light beam 12. Integrated circuits are fabricated in a wafer 14, which is designed as a semiconductor substrate, using the EUV light beam 12. For this purpose, the wafer 14 is coated with a coating 16. The coating 16 is a photoresist. The photoresist is exposed using the EUV light beam 12. Before striking the coating 16, the EUV light beam 12 passes through a mask 18, which locally blocks the EUV light beam 12. This exposes the coating 16 with a specific pattern, resulting in exposed and unexposed areas. The exposed and unexposed areas differ in their solubility. Therefore, the photoresist 16 can be removed from the exposed areas using a developing solution, but cannot be removed from the unexposed areas using the developing solution.After removal of the exposed photoresist, a structure forms on the coating 16, which acts as a local mask on the wafer 14. The masking of individual areas enables the fabrication of a functional layer in the wafer 14, for example by etching the unmasked areas, and thus the fabrication of integrated circuits.

[0054] The EUV driver laser 10 has a plurality of laser beam sources 20. In the illustrated embodiment, the EUV driver laser 10 has eight laser beam sources 20, wherein in Fig. For the sake of clarity, only three laser beam sources 20 are shown. However, it is also conceivable that the EUV driver laser 10 has more or fewer than eight laser beam sources 20. All laser beam sources 20 of the EUV driver laser 10 are identical in construction.

[0055] Each laser beam source 20 is designed as a fiber-coupled beam source. At one output of each laser beam source 20, an optical fiber 22 of the EUV driver laser 10 is arranged. Each optical fiber 22 has a first fiber connector 24 located at a free end of the optical fiber 22. Each first fiber connector 24 is plugged into a fiber port of the laser beam source 20. This positions a free end of a waveguide 26 of the optical fiber 22 at the output of the laser beam source 20.

[0056] The waveguide 26 of each optical fiber 22 is designed as an optical fiber. The waveguide 26 of each optical fiber 22 extends from the first fiber connector 24 to a second fiber connector 28 of the optical fiber 22. For the sake of clarity, in Fig. Figure 1 shows the optical fiber 22 in section. The second fiber connector 28 is arranged at another free end of the optical fiber 22. The second fiber connector 28 is arranged at another free end of the waveguide 26. The second fiber connectors 28 are arranged in a circular arrangement.

[0057] Each laser beam source 20 serves to generate a single laser beam 30. The laser beam sources 20 are designed separately from one another. The laser beam sources 20 can be operated independently of one another.

[0058] Each laser beam 30 is a pulsed beam. Each laser beam 30 can be formed by a single laser pulse with a pulse duration in the range of 10 fs to 800 ns. Each laser beam 30 is a single-mode laser beam whose diffraction coefficient M 2 has a value that is less than 1.3.

[0059] Each laser beam 30 is coupled into the waveguide 26 after being generated by the laser beam source 20, the free end of which is arranged at the output of the laser beam source 20.

[0060] Each waveguide 26 directs the laser beam 30 to the other free end of the waveguide 26. Each laser beam 30 couples out of the waveguide 26 at the other free end. The optical fiber 22 has the advantage that a complex beam guidance system for the laser beams 30 using mirrors and lenses can be almost completely eliminated.

[0061] After exiting the optical fibers 22, the laser beams 30 each pass through a collimation lens 32. Each optical fiber 22 is assigned one collimation lens 32. The number of collimation lenses 32 corresponds to the number of optical fibers 22 and the number of laser beam sources 20.

[0062] The second fiber connectors 28 are each received in a fiber connection, for example in the form of an LLK-D connector. The fiber connections are arranged in a circular or ring-shaped configuration. The collimation lenses 32 are attached to the fiber connections. This results in the collimation lenses 32 being arranged in a circular or ring-shaped configuration.

[0063] After passing through the collimation lenses 32, the laser beams 30 pass through a focusing lens 34, which focuses the laser beams 30 onto a target material 36 of the EUV driver laser 10. The focusing lens 34 is designed as a single lens. Therefore, all laser beams 30 pass through the same focusing lens 34. The laser beams 30 pass through the same focusing lens 34 at different positions.

[0064] In embodiments not shown, the EUV driver laser 10 has only a single laser beam source 20, which generates an original laser beam that is split into a plurality of partial beams by a beam splitter arrangement. The partial beams are then optically amplified in one or more optical amplifiers of an amplifier arrangement such that, after amplification, they form the plurality of laser beams 30. Such EUV driver lasers 10, not shown, can have phase modulation units for the partial beams and / or the laser beams 30, so that the partial beams and / or the laser beams 30 can be modulated with respect to their phase shift relative to each other. In these embodiments, it may be advantageous to generate a plurality of partial beams and to amplify them before or after amplification in the amplifier arrangement.The optical amplifiers are combined in groups to form the plurality of laser beams 30 to be directed at the target material 36. In a specific example, 40, 80, or 160 partial beams can be combined in groups of 5, 10, or 20 partial beams, respectively, to form one laser beam 30 of the plurality of laser beams 30. Of course, different numbers of partial beams and sizes of partial beam groups are also conceivable and possible.

[0065] In other embodiments not shown in detail, a plurality of laser beam sources 20 can be present, which also generate original laser beams, wherein these original laser beams are then amplified individually in one or a plurality of optical amplifiers of an amplifier arrangement, as described in the embodiments not shown in detail above.

[0066] The target material 36 is a tin droplet. The target material 36 is arranged in a target chamber 38 of the EUV driver laser 10. The target chamber 38 is a vacuum chamber. The pressure in the target chamber 38 is less than 10 -9 Pa.

[0067] When the laser beams 30 simultaneously strike the target material 36, the target material 36 is brought into a plasma state by means of the laser beams 30 and the target material 36 emits the EUV light beam 12.

[0068] The EUV light beam 12 emitted by the target material 36 is captured by a collector device 40 of the EUV driver laser 10 and directed onto the mask 18.

[0069] The collector device 40 has a concave EUV reflector. In this example, the EUV reflector is highly reflective for one wavelength of the EUV light beam 12, with a reflectance of over 90%. In other embodiments not shown, a reflectance of over 60% of the EUV reflector is sufficient.

[0070] To direct the laser beams 30 onto the target material 36, the EUV mirror has a central opening 42. The opening 42 is designed as a single, specifically continuous, hole. The laser beams 30 pass through the opening 42.

[0071] The EUV driver laser 10 has a control unit 44. The control unit 44 is designed as a computer.

[0072] The control unit 44 is configured to generate a plurality of signals and to send one of the signals to each laser beam source 20. Each signal is assigned to a laser beam source 20. The number of signals is equal to the number of laser beam sources 20.

[0073] The laser beam sources 20 are configured to receive the signals and generate the laser beams 30 depending on the signals. In other words, the generation of the laser beams 30 by the laser beam sources 20 is triggered by the signals. Each laser beam source 20 generates the laser beam 30 when it receives the signal assigned to it.

[0074] The control unit 44 generates and transmits the majority of signals with a time difference between them, so that the laser beam sources 20 generate the laser beams 30 such that each laser beam 30 strikes the target material 36 for a specific duration, and that these durations overlap within a time interval. As a result, the target material 36 is irradiated by all laser beams 30 simultaneously for the duration of the time interval.

[0075] The laser beams 30 can have different transit times from the laser beam sources 20 to the target material 36, which are balanced or compensated by means of the time differences of the signals, so that the laser beams 30 strike the target material 36 simultaneously for the duration of the time interval.

[0076] Fig. 2 shows the majority of laser beams 30 along a section line II-II according to Fig. 1. The distance between the section line II-II and the target material 36 is less than 5 cm. Fig. Figure 2 shows that the laser beams 30 are arranged in a circular pattern immediately before striking the target material 36. The distance between two adjacent laser beams 30 decreases with decreasing distance to the target material 36. In other words, the diameter of the circular arrangement of the laser beams 30 decreases with decreasing distance to the target material 36.

[0077] Fig. Figure 3 shows an example of the time course of the irradiation of the target material 36 for the in Fig. 1 three laser beams shown 30. In Fig. In Figure 3, a bar is shown for each of the three laser beams 30, representing the time period 46 for which the laser beam 30 hits the target material 36.

[0078] Fig. Figure 3 shows that the three laser beams 30 strike the target material 36 at different times, and the durations 46 differ from one another. For the three laser beams 30, there is a time interval 48 during which the laser beams 30 strike the target material 36 simultaneously. During this time interval 48, the target material 36 is irradiated with such high intensity by the laser beams 30 that it is brought into a plasma state.

[0079] The control unit 44 is predefined by a target time interval length or magnitude. The control unit 44 is configured to regulate the time interval 48 to the predefined target time interval. For this purpose, the control unit 44 is configured to determine or measure the time interval 48. Based on the determined or measured time interval 48, the control unit 44 modifies the time differences with which it transmits the majority of signals, and / or the duration of the signals, until the measured or determined time interval 48 equals the target time interval. This ensures that, for the duration of the target time interval, the intensity at the location of the target material 36 is sufficient to transition the target material 36 into the plasma state.

[0080] Fig. Figure 4 shows the target material 36 during time interval 48 and the in Fig. Figure 1 shows three laser beams 30. The three laser beams 30 superimpose spatially at the location of the target material 36, forming a superposition region 50. The target material 36 is located within the superposition region 50. The laser beams 30 are superimposed non-coherently at the location of the target material 36. It is also conceivable that the EUV driver laser 10 is configured to superimpose the laser beams 30 coherently at the location of the target material 36.

[0081] The intensity required to generate the EUV light beam is provided at the location of the target material 36 by temporally and spatially superimposing the laser beams 30. A single laser beam 30 cannot be designed to convert the target material 36 into the plasma state. Therefore, the laser beams 30 can have such a low intensity that they are guided section by section from the laser beam source 20 to the target material 36 by means of the fiber optic cables 22. This allows the EUV driver laser 10 to be designed to be particularly robust.

[0082] In Fig. 5 is another embodiment of the collector device 40 of the Fig. 1 shown, where the same reference numerals are used for identical and functionally equivalent elements, and in this respect, reference is made to the above explanations regarding the exemplary embodiment of the Fig. 1 can be referenced, so that essentially only the existing differences will be addressed.

[0083] The collector device 40 has a concave EUV mirror. The EUV mirror has a plurality of openings 52. Each opening 52 serves to guide a single laser beam 30 through the collector device 40. The openings 52 are arranged in an edge region of the EUV mirror. Fig. Figure 5 shows that the laser beams 30 emerge from openings 54 of the penetrations 52. The openings 54 are arranged in a circular pattern.

[0084] Fig. Figure 6 shows the collector setup 40 of the Fig. Figure 5 shows a cutaway view. The laser beams 30 emerge from the waveguides 26 at the other free ends of the waveguides, where the second fiber connectors 28 are arranged. Every second fiber connector 28 is received in a fiber termination, for example in the form of an LLK-D connector. The second fiber connectors 28 are arranged in a circular or ring-shaped configuration.

[0085] After exiting the optical fibers 22, the laser beams 30 each pass through a collimating lens 32 and a focusing lens 34. The collimating lenses 32 and the focusing lenses 34 are attached to the fiber connections. This results in the collimating lenses 32 and the focusing lenses 34 being arranged in a circular or ring-shaped configuration.

[0086] In contrast to the exemplary embodiment of the Fig. 1. The EUV driver laser 10 in the exemplary embodiment of the Fig. 6 a plurality of focusing lenses 34. A number of focusing lenses 34 is equal to a number of laser beams 30. Each laser beam 30 can be assigned a focusing lens 34 through which the laser beam 30 passes.

[0087] Fig. Figure 6 shows that the openings 52 pass obliquely through the EUV mirror. Each opening 52 extends along its longitudinal axis 56. The longitudinal axis 56 of each opening 52 forms an angle 62 with respect to an axis of symmetry 60 of the EUV mirror, with respect to which the EUV mirror is rotationally symmetric. The angle 62 has a magnitude in the range of 30° to 60°.

[0088] By arranging the openings 52 in an edge region of the EUV mirror, the area losses and power losses of the EUV mirror that occur due to the openings 52 are lower than in the embodiment of the Fig. 1, in which the laser beams 30 are guided through a single and centrally arranged opening 42.

[0089] In Fig. 7, Fig. 8, Fig. 9 to Fig. Figure 10 shows a further embodiment of the collector device 40, whereby the same reference numerals are used for identical and functionally equivalent elements and reference can be made to the previously made statements, so that essentially only the existing differences are discussed.

[0090] Fig. Figure 7 shows that the collector device 40 has a concave EUV mirror with a first region 64 and a second region 66. Within the first region 64, the EUV mirror has a coating that is highly reflective for the wavelength of the EUV light beam, with a reflectance of over 90% in this case, although a reflectance of over 60% is also present in embodiments not shown. Within the second region 66, the EUV mirror has a coating that is highly reflective for the wavelength of the laser beams 30, with a reflectance of over 90%.

[0091] The first area 64 is surrounded by the second area 66, in particular completely surrounded.

[0092] The coating of the first area 64 and the coating of the second area 66 form a playing surface 68 of the concave EUV mirror. The playing surface 68 has the shape of a surface segment of an ellipsoid.

[0093] The second fiber optic connectors 28 are arranged in a circular or ring-shaped configuration. The laser beams 30 emerge from the optical fibers 22. The laser beams 30 are focused by the focusing lens 34 onto a first focal point 70 of the playing surface 68. The laser beams 30 pass through the first focal point 70 and strike the second area 66, which focuses the laser beams 30 onto the target material 36. The target material 36 is positioned at a second focal point 72 of the playing surface 68.

[0094] Fig. Figure 8 shows that the collector assembly 40 comprises the concave EUV mirror 74 and a deflecting mirror 76 for directing the laser beams 30 onto the target material 36. The deflecting mirror 76 is highly reflective for the wavelength of the laser beams 30, with a reflectance of over 90%. The EUV mirror 74 and the deflecting mirror 76 are designed as two separate mirrors. The deflecting mirror 76 is arranged surrounding the EUV mirror 74.

[0095] The deflecting mirror 76 can be a single, ring-shaped component. The deflecting mirror 76 can be configured as a parabolic mirror. Alternatively, the deflecting mirror 76 can be formed from a plurality of segments surrounding the EUV mirror 74. Each of these multiple segments can be configured as an off-axis parabolic mirror.

[0096] A playing surface 78 of the deflecting mirror 76 has the shape of a surface section of an ellipsoid.

[0097] The second fiber connectors 28 are arranged in a circular or ring-shaped configuration. After exiting the optical fibers 22, the laser beams 30 each pass through a collimation lens 32. After passing through the collimation lens 32, the laser beams 30 are collimated. The collimated laser beams 30 are aligned parallel to each other. The collimated laser beams 30 strike the deflecting mirror 76, which focuses the laser beams 30 onto the target material 36. This eliminates the need for a focusing lens that the laser beams would otherwise have to pass through to be focused onto the target material 36.

[0098] In Fig. 9 has the playing surface 78 of the deflecting mirror 76 in contrast to the embodiment of the Fig. 8 the shape of a surface section of a hyperboloid. Therefore, after passing through the collimation lenses 32, the laser beams 30 each pass through a focusing lens 34. The laser beams 30 are focused onto the target material 36 by the focusing lens 34 and by the deflecting mirror 76.

[0099] In Fig.The deflecting mirror 76 is formed from a plurality of segments surrounding the EUV mirror 74. Each segment of the deflecting mirror 76 has a playing surface 80. The playing surface 78 of the deflecting mirror 76 is formed section by section from the mirror surfaces 80 of the segments. Each playing surface 80 of the segments has the shape of a surface section of an ellipsoid. Each playing surface 80 of the segments has a first focal point 82 and a second focal point 84. Each further free end of the waveguide 26 is arranged in the first focal point 82 of the segment of the deflecting mirror 76 that is associated with the optical fiber 22. The target material 36 is arranged at the second focal points 84 of the segments of the deflecting mirror 76. In other words, the segments are arranged relative to each other such that the second focal points 82 of the segments are coincident.This eliminates the need for a focusing lens and a collimating lens that the laser beams 30 have to pass through in order to be focused on the target material 36.

Claims

[1] Method for generating an EUV light beam (12) by converting a target material (36) into a plasma state using a plurality of laser beams (30), wherein the method comprises: - Generating the majority of laser beams (30), and - Converting the target material (36) into the plasma state by irradiating the target material (36) with the majority of laser beams (30), - wherein during the irradiation of the target material (36) with the plurality of laser beams (30) each laser beam (30) strikes the target material (36) for a duration (46), - where the time durations (46) overlap within a time interval (48). [2] Method according to claim 1, - wherein the irradiation of the target material (36) with the plurality of laser beams (30) comprises a spatial superposition of the plurality of laser beams (30) at the location of the target material (36). [3] Method according to any of the preceding claims, - wherein a plurality of laser beam sources (20) are present, which generate the plurality of laser beams (30), - wherein each laser beam source (20) is configured to receive a signal and generate the laser beam (30) depending on the signal, - wherein generating the plurality of laser beams (30) includes receiving the signals from the plurality of laser beam sources (20), - wherein the signals are received by the majority of the laser beam sources (20) with time differences to each other, - where the time differences cause the time durations (46) to overlap within the time interval (48). [4] Method according to any of the preceding claims, - the procedure involves: specifying a target time interval, - wherein the irradiation of the target material (36) with the plurality of laser beams (30) includes regulating the time interval (48) to the specified target time interval. [5] Method according to any of the preceding claims, - wherein the irradiation of the target material (36) with the plurality of laser beams (30) comprises a coherent superposition or a non-coherent superposition of the plurality of laser beams (30) at the location of the target material (36). [6] Method according to any of the preceding claims, - wherein each laser beam (30) is coupled into a waveguide (26), in particular a fiber optic waveguide (26), and is coupled out of the waveguide (26) before striking the target material (36). [7] Method according to any of the preceding claims, - wherein the majority of laser beams (30) are arranged in a circular arrangement relative to each other immediately before impacting the target material (36). [8] Method according to any of the preceding claims, - wherein the majority of laser beams (30) are guided over a single focusing element (34), in particular a focusing lens, for focusing on the target material (36). [9] Method according to any of the preceding claims, - wherein the EUV light beam (12) is guided over a collector device (40), - wherein the majority of laser beams (30) are guided over or through the collector device (40). [10] EUV driver laser (10) for generating an EUV light beam (12) by converting a target material (36) into a plasma state by means of a plurality of laser beams (30), wherein the EUV driver laser (10) comprises: - at least one laser beam source (20) for generating the majority of laser beams (30), - the target material (36), - a target chamber (38) in which the target material (36) is arranged for generating the EUV light beam (12), - a control device (44) designed to send a signal to the laser beam sources (20), - wherein each laser beam source (20) is configured to receive the signal and generate the laser beam (30) depending on the signal, - wherein the EUV driver laser (10) is configured to perform a method according to any one of the preceding claims 1 to 9. [11] EUV driver laser according to claim 10, - wherein a plurality of laser beam sources (20) are available for generating the plurality of laser beams (30). [12] EUV driver laser (10) according to one of the preceding claims 10 or 11, - wherein the EUV driver laser (10) has a collector device (40), - wherein the collector device (40) is arranged relative to the target material (36) such that the EUV light beam (12) is guided over the collector device (40), - wherein the collector device (40) is arranged relative to the target material (36) such that the majority of laser beams (30) are guided over the collector device (40) or the majority of laser beams (30) are guided through the collector device (40). [13] EUV driver laser (10) according to any one of the preceding claims 10 to 12, - wherein the EUV driver laser (10) comprises a plurality of waveguides (26), in particular fiber optic waveguides, - wherein the majority of waveguides (26) are arranged such that the majority of laser beams (30) are guided at least section by section to the target material (36) by means of the majority of waveguides (26). [14] Use of a method according to any one of claims 1 to 9 above and / or use of an EUV driver laser (10) according to any one of claims 10 to 12 above for the manufacture of an integrated circuit.

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