Control device, control system, method for operating a control system

Abstract

A control system (19, 29, 33, 58) for frequency control of laser modules (20, 21) includes at least one laser module (20, 21) for generating laser radiation, at least one control device (1) coupled to or combinable to the laser module (20, 21), and at least one optical resonator (16, 23, 34) coupled to or combinable to the control device (1), wherein the control device (1) includes a semiconductor substrate (2), a first Pound-Dreyfus-Hall system (3, 4, 22) implemented on the semiconductor substrate (2), and at least one second Pound-Dreyfus-Hall system (3, 4, 22) implemented on the semiconductor substrate (2). The laser modules (20, 21) are coupled to a first Pound-Dreyfus-Hall system (3, 4, 22) of the control device (1) and may be coupled to at least a second Pound-Dreyfus-Hall system (3, 4, 22) of the control device (1), wherein the first Pound-Dreyfus-Hall system (3, 4, 22) is coupled to an optical resonator (16, 23, 34) and wherein the second Pound-Dreyfus-Hall system (3, 4, 22) may be coupled to an optical resonator (16, 23, 34), and wherein the number of Pound-Dreyfus-Hall systems (3, 4, 22) is greater than the number of laser modules (20, 21) or optical resonators (16, 23, 34).

Description

Technical Field

[0001] The present invention relates to a control device, including a semiconductor substrate and a first Pound-Drever-Hall system implemented on the semiconductor substrate.

[0002] The present invention also relates to a control system, a method for operating the control system, and a projection exposure apparatus including such a control system. Background Technology

[0003] The type of control device mentioned in the introduction is known in the prior art. In this regard, a control device comprising a semiconductor substrate and a first Pound-Drever-Hall system implemented on the semiconductor substrate is described, for example, in Idjadi et al., “Integrated Pound-Drever-Hall laser stabilization system in silicon,” Nature Communications 8, 1–9 (2017). In this case, the control device has the effect that the frequency of laser radiation emitted by the laser or laser module can be controlled or stabilized to a predefined reference frequency such that the frequency of the laser radiation is equal to the reference frequency. In that case, the reference frequency is generated by elements of the control device itself.

[0004] From Drever, RWP et al., “Laser phase and frequency stabilization using an optical resonator,” Appl. Phys. B. Photophysics Laser Chem. 31, 97–105 (1983), and documents WO2013 / 016249A2, US2013 / 0044772A1, WO2013 / 040143A2, Alnis et al., “Subhertz linewidth diode lasers by stable to vibrationally and thermally compensated ultralow-expansion glass Fabry-Perot cavities,” Phys. Rev. A–At. Mol. Opt. Phys. 88 (2008), and Zhao et al., “Sub-Hertz frequency stabilization of a commercial diode.” Laser (Subhertz Frequency Stabilized Commercial Diode Lasers), Opt. Commun., 283, 4696-4700 (2019), Toptica-Photonics, Inc., Catalog and Datasheets, Tunable Diode Lasers, Reprinted 2020, p. 41, and Biedermann, B., Menlo Systems ORS1500 Optical Reference System: Design and Performance (2013).

[0005] In view of the above background, the object of the present invention is to provide an improved control device and an improved control method.

[0006] This objective is achieved based on the features described below. Summary of the Invention

[0007] According to one aspect, at least one second Pound-Dreyfus Hall system is configured to be implemented on a semiconductor substrate. Therefore, at least two, particularly more than ten, and preferably more than 50 Pound-Dreyfus Hall systems are implemented on the semiconductor substrate. An advantage here is that a single component or a single control device is available, which includes, in particular, multiple Pound-Dreyfus Hall systems that can operate simultaneously. As an alternative to simultaneous operation, at least the second Pound-Dreyfus Hall system is particularly available for use or adoption as needed. For example, "as needed" means that at least the second Pound-Dreyfus Hall system is used or equipped as a backup system for the first Pound-Dreyfus Hall system, such that, particularly in the event of functional failure or severe degradation or impairment of the first Pound-Dreyfus Hall system, the second Pound-Dreyfus Hall system takes over or can take over the functions or tasks of the first Pound-Dreyfus Hall system. Furthermore, the control device can be manufactured in a cost-effective and space-saving manner because the corresponding Pound-Dreyfus Hall system is implemented or can be implemented on the same semiconductor substrate.

[0008] According to one embodiment, the first and at least the second Pound-Dreyfus-Hall system are individually operable. This provides the advantage that the Pound-Dreyfus-Hall systems are operable in a targeted manner, particularly independently of each other. As an example, this ensures that at least two Pound-Dreyfus-Hall systems can operate or be operable simultaneously or alternatively in a time-shifted manner relative to each other.

[0009] According to other embodiments, the control device includes at least one controller configured to drive the first and at least the second Pound-Dreyfus-Hall systems. An advantage here is that multiple Pound-Dreyfus-Hall systems can be driven in a simple manner, particularly by a single controller. The controller is preferably a separate controller, i.e., not implemented on the semiconductor substrate, and is connected to the control device, particularly in a wire-based manner, for signaling purposes.

[0010] According to other embodiments, the corresponding Pound-Dreyfus-Hall system is configured to include at least one driveable phase modulator unit and / or at least one photodetector unit. Specifically, by driving the phase modulator unit, the light radiation guided by the phase modulator is phase-modulated and / or frequency-modulated in a predefined manner. This ensures the ability to generate at least one sideband, i.e., a frequency band equidistant from the carrier frequency of the light radiation. The photodetector unit is used to detect or capture the light radiation guided by the Pound-Dreyfus-Hall system. The phase modulator unit and the photodetector unit are preferably connected to each other by one or more optical waveguide elements. The optical waveguide elements or corresponding optical waveguide elements are preferably formed of glass, polymer, and / or silicon nitride.

[0011] According to other embodiments, the photodetector unit is a separate component bonded to the control device. The advantage here is that it simplifies the manufacturing process for the control device, as the photodetector unit can be individually mounted on the semiconductor substrate. Preferably, the photodetector unit is bonded to the semiconductor substrate.

[0012] According to one embodiment, the Pound-Dreyfus-Hall system is configured to include at least one electronic component. This at least one or more electronic components are, for example, an amplifier, an oscillator, a low-pass or band-pass filter, a voltage-to-current converter, and / or an analog-to-digital converter.

[0013] According to one embodiment, the electronic components are configured as separate parts adhesively attached to the control device. The advantage here is that it simplifies the process for manufacturing the control device, as one or more electronic components can be individually assembled onto the semiconductor substrate. Preferably, one or more electronic components are bonded to the semiconductor substrate.

[0014] According to one embodiment, the semiconductor substrate comprises silicon and / or silicon nitride.

[0015] The control system according to the invention is characterized by at least one laser module for generating laser radiation, at least one control device coupled to or combinable to the laser module, and at least one optical resonator coupled to or combinable to the control device, wherein the control device comprises a semiconductor substrate, a first Pound-Dreyfus-Hall system implemented on the semiconductor substrate, and at least one second Pound-Dreyfus-Hall system implemented on the semiconductor substrate. An advantage here is that a particularly accurate and particularly fast control system for controlling the frequency, particularly the carrier frequency of the optical radiation from the laser module, is available. Preferably, the frequency or carrier frequency is controlled to a resonant frequency formed in the optical resonator. In particular, the control system ensures the controllability of the frequency or carrier frequency such that even if the resonant frequency changes, the frequency always remains equal to or equal to the resonant frequency. Furthermore, an advantage is provided that multiple laser modules can be operated and controlled in parallel by the control system. The optical resonator is preferably formed by two mirror elements arranged at a distance from each other. Preferably, the control system additionally includes at least one isolator and at least one delay plate, particularly a λ / 4 or λ / 2 plate or equivalent integrated component.

[0016] According to the present invention, the laser module is configured to be coupled to a first Pound-Dreyfus-Hall system of the control device and is also capable of being coupled to at least a second Pound-Dreyfus-Hall system of the control device. The advantage here is that the second Pound-Dreyfus-Hall system can be coupled to the laser module as needed. Therefore, the second Pound-Dreyfus-Hall system specifically serves as a backup system for the first Pound-Dreyfus-Hall system. In the event of a malfunction or error in the first Pound-Dreyfus-Hall system, the reliable functioning of the control device and control system is thus continued to be ensured.

[0017] According to one development example, the control system is configured to include at least two laser modules and at least three Pound-Dreyfus-Hall systems, wherein each laser module is coupled to a corresponding Pound-Dreyfus-Hall system of the control device, and wherein each laser module can be coupled to at least one third Pound-Dreyfus-Hall system of the control device. The advantage here is that the third Pound-Dreyfus-Hall system can be coupled to a laser module as needed, ensuring or continuing to ensure the reliable functioning of the control device and the control system even in the event of a malfunction or error in the coupled Pound-Dreyfus-Hall system.

[0018] According to the present invention, a first Pound-Dreyfus-Hall system is configured to be coupled to an optical resonator, and a second Pound-Dreyfus-Hall system is configured to be coupled to the optical resonator. The advantage here is that the second Pound-Dreyfus-Hall system can be coupled to the optical resonator as needed. Therefore, the second Pound-Dreyfus-Hall system serves as a backup system for the first Pound-Dreyfus-Hall system. In the event of a malfunction or error in the first Pound-Dreyfus-Hall system, the reliable functioning of the control device and control system is thus continued to be ensured.

[0019] According to one development example, the control system is configured to include at least two optical resonators and at least three Pound-Dreyfus-Hall systems, wherein each optical resonator is coupled to a corresponding Pound-Dreyfus-Hall system of the control device, and wherein each optical resonator can be coupled to at least a third Pound-Dreyfus-Hall system. The advantage here is that the third Pound-Dreyfus-Hall system can be coupled to one of the optical resonators as needed, ensuring or continuing to ensure the reliable functioning of the control device and control system even in the event of a malfunction or error in the coupled Pound-Dreyfus-Hall systems.

[0020] According to the present invention, the number of Pound-Dreyfus-Hall systems is set to be greater than the number of laser modules or optical resonators. This ensures that at least one Pound-Dreyfus-Hall system can be used as a backup or supplementary system. If the control system includes more laser modules than optical resonators, the number of Pound-Dreyfus-Hall systems is preferably greater than the number of laser modules. If the control system includes more optical resonators than laser modules, the number of Pound-Dreyfus-Hall systems is preferably greater than the number of optical resonators.

[0021] According to one development example, the number of Pound-Dreyfus-Hall systems is at least twice the number of laser modules or optical resonators.

[0022] According to one development example, the control system includes at least one drive unit configured to drive a first and at least a second Pound-Dreyfus-Hall system to achieve coupling or decoupling. The advantage here is that the corresponding Pound-Dreyfus-Hall system can be coupled or decoupled in a targeted and simple manner with a specific laser module and / or a specific optical resonator.

[0023] According to one embodiment, the driving unit is a matrix circuit, particularly an optical, photonic integrated, or fiber matrix circuit. The advantage here is that coupling and / or decoupling can be implemented particularly quickly.

[0024] According to one embodiment, the laser module is coupled to at least two Pound-Dreyfus-Hall systems. The advantage here is that the laser radiation from a single laser module can be directed, or may be directed, in parallel or simultaneously to two or more Pound-Dreyfus-Hall systems. Preferably, each of the Pound-Dreyfus-Hall systems is coupled to the same optical resonator. Alternatively, each of the Pound-Dreyfus-Hall systems is coupled to a corresponding optical resonator, wherein the optical resonators are different from each other. Optionally, the control system comprises at least two laser modules, wherein each of the at least two laser modules is coupled to at least two Pound-Dreyfus-Hall systems in each case.

[0025] According to one embodiment, the laser radiation from one Ponder-Dreyfus-Hall system coupled to a laser module and the laser radiation from another Ponder-Dreyfus-Hall system coupled to the laser module have a phase offset or frequency offset relative to each other. In this context, "phase offset" means that the frequency or carrier frequency of the laser radiation from one Ponder-Dreyfus-Hall system coupled to the laser module is not spaced apart from the frequency or carrier frequency of the laser radiation from the other Ponder-Dreyfus-Hall system coupled to the laser module, and is particularly equidistant from each other. Therefore, "phase offset" should be understood, in particular, as a frequency offset. "Equidistant" means that the frequency or carrier frequency of the laser radiation from one Ponder-Dreyfus-Hall system coupled to the laser module is an integer multiple of the frequency or carrier frequency of the laser radiation from the other Ponder-Dreyfus-Hall system coupled to the laser module. Specifically, the frequency or carrier frequency of the laser radiation from one Ponder-Dreyfus-Hall system coupled to the laser module and the frequency or carrier frequency of the laser radiation from the other Ponder-Dreyfus-Hall system coupled to the laser module form a frequency comb. Preferably, the interval between the frequency or carrier frequency of the laser radiation from one Pound-Dreyfus-Hall system coupled to the laser module and the frequency or carrier frequency of the laser radiation from another Pound-Dreyfus-Hall system coupled to the laser module is set to an integer multiple of the mode interval between at least two resonator modes corresponding to the optical resonator.

[0026] According to one embodiment, to generate a phase shift or frequency shift, a modulator unit is connected between the laser module and the Pound-Dreyfus-Hall system. The modulator unit is, for example, an electro-optic modulator or an electro-optic phase modulator. This provides the advantage that the phase shift or frequency shift can be generated in a simple manner, and thus particularly by a frequency comb formed by the frequency or carrier frequency of the laser radiation from one Pound-Dreyfus-Hall system coupled to the laser module and the frequency or carrier frequency of the laser radiation from another Pound-Dreyfus-Hall system coupled to the laser module. The electro-optic phase modulator is therefore preferably configured to generate multiple sidebands forming the frequency comb.

[0027] According to one embodiment, the modulator unit includes a combline spacing control unit.

[0028] According to one development example, the control system includes an additional photodetector unit, which can be connected to or connected to a reference light source.

[0029] According to one development example, the control system includes a first wavelength-selective optical switch and at least one second wavelength-selective optical switch. This provides the advantage that the frequency comb's deterministic or deterministic comb line (particularly for frequency control) is selectable or filterable.

[0030] The method according to the invention implements the control system described above in a method for operating a control system for frequency control of a laser module, the method comprising the steps of: a) operating one Pound-Dreyfus-Hall system of the control device and at least another Pound-Dreyfus-Hall system of the control device; b) coupling the laser module to one of the Pound-Dreyfus-Hall systems of the control device; c) detecting at least one actual value of a predefined electrical parameter of the one Pound-Dreyfus-Hall system; d) comparing the actual value with a predefined setpoint value; e) if a determined deviation between the actual value and the setpoint value is greater than a predefined limit deviation, decoupling the laser module from the one Pound-Dreyfus-Hall system; f) coupling the laser module to another Pound-Dreyfus-Hall system. This provides the advantages already mentioned. Other advantages and preferred features are apparent from the above description.

[0031] According to the method for frequency control of a laser module of a control system according to the present invention, the control system described above is implemented, the method comprising the steps of: a) coupling the laser module to at least one of the Pound-Dreyfus-Hall systems of the control device; b) generating laser radiation through the laser module and introducing the laser radiation into the Pound-Dreyfus-Hall system; c) introducing the laser radiation having a carrier frequency of the laser radiation into a phase modulator unit of the control device and generating at least one sideband; d) dividing the laser radiation into a first portion of radiation having a carrier frequency of the laser radiation and a second portion of radiation having a carrier frequency with a potential phase shift of the laser radiation; e) superimposing the first portion of radiation and the second portion of radiation; f) monitoring a predefined deviation between the first portion of radiation and the second portion of radiation; g) if it is identified that the deviation between the first portion of radiation and the second portion of radiation is greater than a predefined deviation, controlling the carrier frequency of the laser radiation, wherein the carrier frequency is controlled to be equal to a reference frequency. This provides the advantages already mentioned. Other advantages and preferred features are apparent from the above description.

[0032] According to one embodiment, frequency control is implemented based on the drive comb spacing control unit.

[0033] The illumination system of the projection exposure apparatus for EUV lithography according to the present invention comprises: a housing surrounding the interior, at least two optical elements arranged in the housing, wherein the at least two optical elements form an optical resonator, and the illumination system is characterized by a control system according to the above description. This provides the advantages already mentioned. Other advantages and preferred features will be apparent from the above description.

[0034] The projection system of the projection exposure apparatus for EUV lithography according to the present invention comprises: a housing surrounding the interior, at least one optical element disposed within the housing, wherein at least two optical elements form an optical resonator, the projection system being characterized by a control system according to the above description. This provides the advantages already mentioned. Other advantages and preferred features will be apparent from the above description.

[0035] The projection exposure apparatus for EUV lithography according to the present invention comprises an illumination system and a projection system, characterized by a control system as described above. This provides the advantages already mentioned. Other advantages and preferred features will be apparent from the above description. Attached Figure Description

[0036] The invention will be explained in more detail below with reference to the accompanying drawings. In this respect:

[0037] Figure 1 A schematic diagram of a control device according to an exemplary embodiment is shown.

[0038] Figure 2 A schematic diagram of a control system according to a first exemplary embodiment is shown.

[0039] Figure 3 A flowchart illustrating frequency stabilization or frequency control for a laser module according to an exemplary embodiment is shown.

[0040] Figure 4 A frequency curve of the laser module controlled by the control system according to a first exemplary embodiment is shown.

[0041] Figure 5 A schematic diagram of a control system according to a second exemplary embodiment is shown.

[0042] Figure 6 A schematic diagram of a control system according to a third exemplary embodiment is shown.

[0043] Figure 7 A frequency response curve of the controlled frequency of the laser module according to the second exemplary embodiment is shown.

[0044] Figure 8 A schematic diagram of a control system according to a fourth exemplary embodiment is shown.

[0045] Figure 9 A frequency response curve of the controlled frequency of the laser module according to a third exemplary embodiment is shown.

[0046] Figure 10 A flowchart of an operation control system according to an exemplary embodiment is shown, and

[0047] Figure 11 A projection exposure apparatus including a control system according to an exemplary embodiment is shown. Detailed Implementation

[0048] Figure 1 The simplified illustration shows a control device 1 according to a first exemplary embodiment. The control device 1 includes a semiconductor substrate 2 and a first Pound-Dreyfus-Hall system 3 and a second Pound-Dreyfus-Hall system 4 implemented on the semiconductor substrate 2. Optionally, more than two Pound-Dreyfus-Hall systems 3 and 4, particularly more than ten, preferably more than fifty, and optionally more than one hundred, are implemented on the semiconductor substrate 2.

[0049] The corresponding Pound-Dreyfus-Hall systems 3 and 4 include at least one phase modulator unit 5, at least one beam splitter element 6 formed, for example by one or more partially transmissive mirrors or particularly by coupled waveguides, and at least one photodetector unit 7. Preferably, the phase modulator unit 5, the beam splitter element 6, and the photodetector unit 7 are interconnected via optical waveguide elements 8. The waveguide element 8 is preferably formed of glass, polymer, silicon, and / or silicon nitride. The phase modulator unit 5, the beam splitter element 6, and the waveguide element 8 are preferably monolithically integrated in or implemented on the semiconductor substrate 2. The photodetector unit 7 is preferably monolithically integrated in or implemented on the semiconductor substrate 2. Optionally, the photodetector unit 7 is a separate component, particularly the semiconductor substrate 2, bonded to the control device 1, for example, by a bonding connection.

[0050] Furthermore, the corresponding Pound-Dreyfus-Hall systems 3 and 4 include at least one electronic component 9. In the present case, the corresponding Pound-Dreyfus-Hall systems 3 and 4 include multiple electronic components 9, particularly an electronic amplifier 10, an electronic hybrid element 11, an electronic oscillator 12, an electronic driver element 13 for driving the phase modulator 5, a low-pass filter element 14, a voltage-to-current converter 15, and an analog-to-digital converter (not shown here). Preferably, all electronic components 9 are monolithically integrated or embedded in the semiconductor substrate 2. Optionally, at least one of the electronic components 9 is a separate component, particularly the semiconductor substrate 2 of the control device 1, which is adhesively connected to the control device 1, particularly the semiconductor substrate 2 of the control device 1, for example, by a bonding connection. Optionally, all electronic components 9 form a component module 17, which is adhesively connected or connected to the control device 1, particularly the semiconductor substrate 2 of the control device 1, for example, by a bonding connection.

[0051] Both the first and second Pond-Dreyfus-Hall systems 3 and 4 are implemented as actuated. This ensures independent operation of the respective Pond-Dreyfus-Hall systems 3 and 4. To actuate the Pond-Dreyfus-Hall systems 3 and 4, the control device 1 includes a controller 18, which is connected to the Pond-Dreyfus-Hall systems 3 and 4 in terms of signaling.

[0052] Preferably, the control device 1 is implemented as a photonic integrated circuit.

[0053] Preferably, the semiconductor substrate 2 comprises silicon, silicon oxide, and / or silicon nitride.

[0054] Figure 2 A simplified illustration shows a control system 19 according to a first exemplary embodiment. The control system 19 includes at least one laser module 20 (in the present case, two laser modules 20, 21), a control device 1 (which includes three Pound-Dreyfus-Hall systems 3, 4, 22 according to an exemplary embodiment), and at least one optical resonator 16 (in the present case, two optical resonators 16, 23). The control system 19 is used for frequency control or frequency stabilization of the respective laser modules 20, 21, particularly the frequency or carrier frequency of the respective laser modules 20, 21. The laser modules 20, 21 are preferably implemented as tunable, continuously operable laser modules 20, 21, particularly laser diodes.

[0055] In the current configuration, one laser module 20 is coupled to the Pound-Dreyfus-Hall system 3, and another laser module 21 is coupled to the Pound-Dreyfus-Hall system 4. The term "coupled" in this configuration, based on the example of laser module 20 and the Pound-Dreyfus-Hall system 3, refers to the existence of a signaling connection between them. Laser radiation emitted by laser module 20 is thus guided into the Pound-Dreyfus-Hall system 3, specifically by waveguide element 8. The Pound-Dreyfus-Hall system 22 (not coupled to laser modules 20 and 21 in the current configuration) is, in the current configuration, a couplerable Pound-Dreyfus-Hall system.

[0056] Furthermore, optical resonator 16 is coupled to Pound-Dreyfus-Hall system 3 and optical resonator 23 is coupled to Pound-Dreyfus-Hall system 4. The term "coupled" in this context, based on the example of optical resonator 16 and Pound-Dreyfus-Hall system 3, refers to the existence of a signaling connection between optical resonator 16 and Pound-Dreyfus-Hall system 3. Laser radiation directed into Pound-Dreyfus-Hall system 3 is transmitted to optical resonator 16 via waveguide element 8. Pound-Dreyfus-Hall system 22 (which is not currently coupled to any optical resonators 16, 23) is, in this context, a couplerable Pound-Dreyfus-Hall system.

[0057] The control system 19 includes a drive unit 24 configured to drive each of the three Pound-Dreyfus-Hall systems 3, 4, 22 and / or the two laser modules 20, 21 in the current situation, particularly to couple one of the laser modules 20, 21 with one of the Pound-Dreyfus-Hall systems 3, 4, 22 and / or decouple one of the laser modules 20, 21 from one of the Pound-Dreyfus-Hall systems 3, 4, 22. The drive unit 24 includes a matrix circuit 25, particularly a high-frequency optical matrix circuit. The drive unit 24 or matrix circuit 25 preferably includes a plurality of signal inputs 26 and a plurality of signal outputs 27. Preferably, the corresponding signal inputs 26 can be connected to the corresponding laser module 20, 21, and the corresponding signal outputs 27 can be connected to the corresponding Pound-Dreyfus-Hall system 3, 4. The drive unit 24 is preferably connected to a controller 18 or a separate controller not shown herein for signaling purposes.

[0058] In the present case, the control system 19 includes an additional drive unit 28, which is specifically implemented as an optical matrix circuit 25 and is configured to drive each of the three Pound-Dreyfus-Hall systems 3, 4, 22 and / or each of the two optical resonators 16, 23 in the present case, in particular to implement coupling of one of the Pound-Dreyfus-Hall systems 3, 4, 22 with one of the optical resonators 16, 23 and / or decoupling of one of the Pound-Dreyfus-Hall systems 3, 4, 22 with one of the optical resonators 16, 23.

[0059] Preferably, the number of Pound-Dreyfus-Hall systems 3, 4, 22 is greater than the number of laser modules 20, 21 or optical resonators 16, 23. Preferably, the number of Pound-Dreyfus-Hall systems 3, 4, 22 is at least twice the number of laser modules 20, 21 or optical resonators 16, 23. This ensures that a sufficient number of additional, particularly couplerable, Pound-Dreyfus-Hall systems 3, 4, 22, or Pound-Dreyfus-Hall systems used as backups are always available.

[0060] Optionally, the control device 1 includes an optical isolator and / or delay plate, such as a λ / 4 plate, which are not shown here. The isolator and / or delay plate are preferably arranged between the control device 1 and the optical resonators 16, 23.

[0061] Optionally, at least one, and in particular all, of the laser modules 20 and 21 are part of the control device 1 itself. The laser modules 20 and 21 are therefore optionally implemented on the semiconductor substrate 2 of the control device 1.

[0062] Figure 3 A flowchart for frequency stabilization or frequency control of the laser module is shown. For simplicity, the method is described based on laser module 20, Pound-Dreyfus-Hall system 3, and optical resonator 16.

[0063] In the first step S1, the laser module 20 is coupled to the Pound-Dreyfus-Hall system 3. The coupling is achieved by the drive unit 24.

[0064] In the second step S2, the laser module 20 generates laser radiation with a predefined frequency (hereinafter referred to as the carrier frequency) and directs it into the Pound-Dreyfus-Hall system 3.

[0065] In the third step S3, the laser radiation is transmitted to the phase modulator 5. The phase modulator is driven to generate at least one sideband, and more particularly multiple sidebands. In this case, a "sideband" refers to a frequency that is equidistant from the carrier frequency of the laser radiation.

[0066] In the fourth step S4, laser radiation is transmitted to beam splitter element 15. A portion of the laser radiation with a carrier frequency (the first portion of the beam) is deflected in the direction of photodetector unit 7. Another portion of the laser radiation (the second portion of the beam) is directed in the direction of optical resonator 16. Optical resonator 16 is preferably formed by two mirror elements, or in particular coupled waveguide elements, arranged relative to each other at a predefined distance. The portion of the laser radiation illuminating optical resonator 16 is transmitted into optical resonator 16, reflected in optical resonator 16, returns to beam splitter 15, and is then deflected in the direction of photodetector unit 7. The other portion of the laser radiation (i.e., the laser radiation passing through optical resonator 16) also has a carrier frequency, which may have a frequency-dependent phase shift due to the complex reflectivity of optical resonator 16, in particular.

[0067] In the fifth step S5, the carrier frequency of the first beam is superimposed with the carrier frequency of the second beam and compared. This superposition is implemented in the photodetector unit 7.

[0068] Step S6 involves monitoring the deviation between the carrier frequency of the first partial beam and the carrier frequency of the second partial beam. This is achieved, in particular, by superimposing the carrier frequencies of the second and first partial beams and the sideband generated by the phase modulator 5. If the detected deviation is zero, which can be determined, for example, based on the photocurrent generated by the superposition, the method continues in step S2. If the carrier frequency of the laser module 20 is equal to the resonant frequency of the optical resonator 16, the deviation is zero. Additionally or alternatively, the deviation is zero if the carrier frequency of the first partial beam is equal to the carrier frequency of the second partial beam, wherein the carrier frequency of the second partial beam is equal to or must be equal to the resonant frequency of the optical resonator 16.

[0069] If the detected deviation is not zero, then in the seventh step S7, the carrier frequency of the laser module 20 is controlled to be equal to the resonant frequency of the optical resonator 16. This control is achieved by an electrical correction current or control current, which is based on photocurrent generation and is fed to the laser module 20 via the electronic component 9.

[0070] The advantage of both the control system 19 and the method is that the frequencies, or carrier frequencies, of the laser modules 20, 21 respond particularly quickly and accurately to changes (especially changes in length) of the optical resonators 16, 23. Therefore, the carrier frequency can be continuously controlled in a manner equal to the resonant frequency of the optical resonator 16. Embodiments with at least two Pound-Dreyfus-Hall systems 3, 4 on the same semiconductor substrate 2 ensure that multiple optical resonators 16, 23 can be monitored simultaneously and independently of each other in a cost-effective and space-saving manner, and thus the carrier frequencies of the multiple Pound-Dreyfus-Hall systems 3, 4 are continuously controllable.

[0071] Figure 4 An example frequency curve is shown, in which the carrier frequency, denoted by reference numeral 65 in the present case, is controlled. In this case, the sloping lines represent modes or resonant modes formed or potentially formed in the optical resonator 16. The length of the optical resonator 16 is represented on the x-axis (denoted by X in the present case), and the carrier frequency or laser frequency is represented on the y-axis (denoted by Y in the present case). Depending on the length of the optical resonator 16, the carrier frequency is controlled to keep it in the same mode. The tunability bandwidth of the laser module 20, denoted by reference numeral 60 in the present case, is preferably at least 100 GHz and at most 10,000 GHz, preferably at least 1,000 GHz and at most 10,000 GHz, and particularly preferably at least 1,000 GHz and at most 5,000 GHz.

[0072] Figure 5A simplified illustration shows a control system 29 according to a second exemplary embodiment. The control system 29 corresponds to... Figure 2 The control system 19 described herein differs in that it additionally includes an additional photodetector unit 30, such as a photodiode, particularly a quadruple photodiode. The additional photodetector unit 30 is a separate component or alternative part of the control device 1 itself, i.e., implemented on the semiconductor substrate 2 of the control device 1. The additional photodetector unit 30 is connected to a reference light source 31, which is configured to generate a reference carrier frequency or reference frequency in terms of signaling. Furthermore, at least one sideband, particularly multiple sidebands, is generated with respect to the reference carrier frequency. The reference light source 31 preferably includes a frequency comb generator, particularly a frequency comb, for generating at least one sideband. In the additional photodetector unit 30, the particularly controlled carrier frequency of the laser modules 20, 21 is superimposed with the reference carrier frequency or frequency comb. The photodetector unit 31 is connected to an evaluation unit 32 in terms of signaling. The evaluation unit 32 monitors the deviation between the carrier frequency and the reference carrier frequency or frequency comb. If the detected deviation is zero, i.e., if the carrier frequency equals the reference carrier frequency, then the length change of the optical resonator 16 is zero. If the detected deviation is not zero, i.e., the carrier frequency is not equal to the reference carrier frequency, the length change of the optical resonator 16 depends on the position or positional variation of the carrier frequency relative to the reference carrier frequency (especially relative to the corresponding one or more sidebands). In the present case, "length change" refers to the change in distance (e.g., due to lateral displacement) or positional variation (e.g., due to tilt) of the mirror elements of the optical resonators 16, 23 relative to each other.

[0073] Figure 6 The simplified illustration shows a control system 33 according to a third exemplary embodiment. In the present case, the control system 33 includes a laser module 20, a control device 1 (which includes at least two in an exemplary embodiment, and three in the present case, Pound-Dreyfus-Hall systems 3, 4, 22), and at least one optical resonator (in the present case, three optical resonators 16, 23, 34).

[0074] In the current configuration, laser module 20 is coupled to each of the three Pound-Dreyfus-Hall systems 3, 4, and 22. In this configuration, the carrier frequencies of the laser radiation guided into the respective Pound-Dreyfus-Hall systems have a phase shift or frequency shift relative to each other. To generate the phase shift or frequency shift, a modulator unit 35 is connected between laser module 20 and the Pound-Dreyfus-Hall systems 3, 4, and 22. Modulator unit 35 is preferably implemented as an electro-optic modulator. Preferably, modulator unit 35 is connected to controller 18 in signaling terms for being driven by controller 18. Specifically, the frequency comb is generated by the phase shift or frequency shift. This means that the carrier frequencies or comb lines of the respective laser radiation guided into the Pound-Dreyfus-Hall systems 3, 4, and 22 are equidistant from each other. In other words, the laser radiation coupled or potentially coupled to optical resonator 16 has a frequency comb spectrum. The latter is characterized by multiple frequencies with equal frequency intervals. Preferably, the frequency interval is selected as an integer multiple of the mode interval between at least two resonator modes of the optical resonator 16.

[0075] The advantage here is that, particularly for the current situation where each of the Pound-Dreyfus-Hall systems 3, 4, and 22 is coupled to the same optical resonator (in the current case, optical resonator 16), this single optical resonator 16 can be monitored by multiple Pound-Dreyfus-Hall systems 3, 4, and 22. It is especially advantageous that the tunability bandwidth of the laser module is limited, for example, to less than 1000 GHz, and particularly less than 100 GHz.

[0076] As an example, if the carrier frequency of the Pound-Dreyfus-Hall system 3 (referred to as the first carrier frequency 36 in the present case) is controlled based on the resonant frequency of the optical resonator 16, and if the carrier frequency reaches the tunability limit of the laser module 20, then it is preferable to drive another of the Pound-Dreyfus-Hall systems 4, 22. This driven Pound-Dreyfus-Hall system 4, 22 is particularly a Pound-Dreyfus-Hall system 4 in which a second carrier frequency 37 is introduced that is equidistant from the first carrier frequency. Frequency control is then achieved based on this second carrier frequency 37. If this second carrier frequency reaches the tunability limit of the laser module 20, then it is preferable to drive another of the Pound-Dreyfus-Hall systems 3, 22, for example, a Pound-Dreyfus-Hall system 4 in which a third carrier frequency 38 that is equidistant from the second carrier frequency 37 is introduced. The driving of the corresponding Pound-Dreyfus-Hall systems 3, 4, 22 depends on the development or current resonant frequency of the optical resonator 16.

[0077] Figure 7 It shows the results based on the information about Figure 6An example of a frequency curve diagram of the control system 33 that controls the carrier frequency.

[0078] The first carrier frequency 36, the second carrier frequency 37, the third carrier frequency 38, and other optional carrier frequencies are shown. If a limit is reached, i.e., the upper limit 39 or the lower limit 40 of the tunability of the laser module 20, the switch is made to the corresponding carrier frequency 36, 37, or 38. The bandwidth of the tunability of the laser module, i.e., the interval between the upper limit 39 and the lower limit 40, is currently at a maximum of 100 GHz, and more specifically at a maximum of 1000 GHz.

[0079] Figure 8 A simplified illustration shows a control system 58 according to a fourth exemplary embodiment. In this present case, the control system 58 includes a laser module 20, a control device 1 (which, according to an exemplary embodiment, includes at least two, and in this present case, three, Pound-Dreyfus-Hall systems 3, 4, 22), and at least one optical resonator 16. The control system also includes a first wavelength-selective optical switch 59 and a second wavelength-selective optical switch 60, as well as a drive unit 24 and a modulator unit 35.

[0080] In the current configuration, laser module 20 is coupled or can be coupled to each of the three Pound-Dreyfus-Hall systems 3, 4, 22. A frequency comb is generated from the carrier frequency of laser module 20 via modulator unit 35. The number of comb lines of the frequency comb preferably corresponds to the number of Pound-Dreyfus-Hall systems 3, 4, 22. This ensures that Pound-Dreyfus-Hall systems 3, 4, 22 are or can be locked to comb lines, or can be coupled to comb lines. In the current configuration, the comb line spacing between two comb lines of the frequency comb can be set in a variable manner, particularly by driving modulator unit 35 by controller 18. Preferably, modulator unit 35 includes a driveable comb line spacing control unit 61 configured to set the comb line spacing in a variable manner.

[0081] The frequency comb generated by the laser radiation is guided to phase modulator 5. The latter generates at least one sideband with respect to each generated comb line. The laser radiation is then split into a first beam 63 and a second beam 64 by beam splitter 62. The first beam 63 is guided to a first wavelength-selective optical switch 59. The second beam 64 is guided to optical resonator 16 and then to a second wavelength-selective optical switch 60. In this case, the first beam 63 is a beam with a carrier frequency. The second beam 64 (i.e., the laser radiation passing through optical resonator 16) also has a carrier frequency, which may have a frequency-dependent phase shift due to the complex reflectivity of the optical resonator 16.

[0082] Wavelength selective optical switches 59 and 60 are configured to switch or filter output comb lines or output frequencies from the three comb lines or input frequencies in the current condition. Wavelength selective optical switches 59 and 60 filter the same comb line in each condition, for example, filtering the first, second, or third comb line in each condition. The separately switched or filtered output comb lines are combined in a separate beam splitter 62 and passed to the photodetector unit 7, where the comb lines are superimposed.

[0083] Optionally, regarding Figure 2 The described control system 19 or about Figure 5 The described control system 29 includes wavelength-selective optical switches 59 and 60 and optionally comb-line spacing control unit 61.

[0084] Optionally, the control systems 33, 58 include at least two laser modules 20, 21, each of which is coupled to at least two Pound-Dreyfus-Hall systems 3, 4, 22 in each case.

[0085] Figure 9 It shows the results based on the information about Figure 8 An example of a frequency curve diagram of the control system 58 controlling the carrier frequency is shown. A first carrier frequency 36 or a first comb line, a second carrier frequency 37 or a second comb line, a third carrier frequency 38 or a third comb line, and optional other carrier frequencies or comb lines are shown. If the comb line locked or coupled to the resonator mode reaches the limit of the tunability of the laser module 20 (i.e., upper limit 39 or lower limit 40), the modulator unit 35, particularly the comb line spacing control unit 61, is driven.

[0086] Based on this, it is then possible to achieve, in particular, the nearest adjacent comb line or carrier frequency (comb line 66 in the current case), which in this case remains coupled or locked to the resonator mode, or to control the comb line spacing based on the corresponding coupled Pound-Dreyfus-Hall systems 3, 4, 22, and in particular, to further control it. This ensures that the comb lines always remain or locked to the resonator mode.

[0087] Preferably, the comb line spacing control unit 61 of the modulator 35 is driven at a predefined time point, such as a predefined duration before or when the limits 39 and 40 are reached.

[0088] Figure 10 A flowchart for operating control systems 19, 29, 33, and 58 is shown.

[0089] In the first step S1, one Pond-Dreyfus Hall system 3, 4, 22 of the control device 1 and at least one other Pond-Dreyfus Hall system 3, 4, 22 of the control device 1 are operated or perform operations. If the control device 1 includes more than two Pond-Dreyfus Hall systems 3, 4, 22, it is preferable to operate all Pond-Dreyfus Hall systems 3, 4, 22.

[0090] In the second step S2, laser modules 20 and 21 are coupled to one of the Pound-Dreyfus-Hall systems 3, 4, and 22 of the control device 1. Optionally or additionally, the Pound-Dreyfus-Hall systems 3, 4, and 22 coupled to laser modules 20 and 21 are coupled to optical resonators 16, 23, and 34.

[0091] In the third step S3, at least one actual value of a predefined electrical parameter of the Pound-Dreyfus Hall system 3, 4, 22 is detected. The electrical parameter is, for example, the capacitance or resistance of at least one electronic component 9 of the control device 1 and / or the capacitance or resistance of some other components of the Pound-Dreyfus Hall system 3, 4, 22, such as the capacitance or resistance of the photodetector unit 7.

[0092] In the fourth step S4, the actual value is compared with a predefined setpoint value. For example, the detected actual resistance is compared with the predefined setpoint resistance. If the deviation between the detected actual value and the setpoint value is less than or equal to the predefined limit deviation, the method continues in step S3.

[0093] If the deviation between the actual value and the setpoint value is detected to be greater than a predefined limit deviation, then in step S5, the non-functionality or critical functionality of the Pound-Dreyfus-Hall systems 3, 4, and 22 is identified, and laser modules 20 and 21 are decoupled from the non-functional Pound-Dreyfus-Hall systems 3, 4, and 22. Subsequently, laser modules 20 and 21 are coupled to another couplerable Pound-Dreyfus-Hall system 3, 4, and 22. Preferably, the non-functional Pound-Dreyfus-Hall systems 3, 4, and 22 are additionally decoupled from optical resonators 16, 23, and 34, and optical resonators 16, 23, and 34 are subsequently coupled to another couplerable Pound-Dreyfus-Hall system 3, 4, and 22. The corresponding coupling and / or decoupling is implemented by the drive unit 24 or the matrix circuit 25.

[0094] The advantage provided by this is that reliable monitoring of optical resonators 16, 23, and 34 is ensured or maintained even if one of the used or coupled Pound-Dreyfus-Hall systems 3, 4, and 22 fails or becomes inoperable.

[0095] Figure 11 A projection exposure apparatus 42 or EUV lithography apparatus for EUV lithography is shown according to an exemplary embodiment. The projection exposure apparatus 42 includes a beam generation system 43 with a driveable light source, an EUV light source 44 that generates working light in the present case, an illumination system 45, and a projection system 46.

[0096] According to this exemplary embodiment, the beam generation system 43 includes a first housing 47 that at least partially surrounds the interior of the beam generation system, the illumination system 45 includes a second housing 48 that at least partially surrounds the interior of the illumination system 45, and the projection system 46 includes a third housing 49 that at least partially surrounds the interior of the projection system 46. The first, second, and / or third housings 47, 48, and 49 are each implemented as part of the overall housing 50 of the projection exposure device 42, which is shown herein only in a simplified manner.

[0097] The projection exposure equipment 42 is operated under vacuum conditions, particularly the entire housing 50 or the partial housings 47, 48, and 49 that form the entire housing 50.

[0098] In the present case, EUV light emitted by EUV light source 44, which has a wavelength of at least 5 nm and at most 30 nm in the present case, is focused into the light collector reflector 51 of beam generating device 43 and then guided into illumination system 45.

[0099] In the present case, the illumination system 45 includes at least one first optical element and a second optical element 52, 53, which are implemented as mirrors or mirror elements in various cases. EUV light introduced into the illumination system 45 is guided by the optical elements 52, 53 onto a photomask 54 or a mask master, the structure of which is imaged onto the wafer 55 at a reduced scale by the projection system 46. For this purpose, the projection system includes third and fourth optical elements 56, 57, which are also implemented as mirrors or mirror elements in various cases.

[0100] According to this exemplary embodiment, the projection system 46 includes control systems 19, 29, 33, and 58. The control systems 19, 29, 33, and 58 are, in particular, wholly or preferably only partially arranged or may be arranged in the projection system 46.

[0101] As described above, the control systems 19, 29, 33, and 58 include at least one laser module 20 or 21 for generating laser radiation, at least one control device 1 coupled to or combinable to the laser module 20 or 21, and at least one optical resonator 16, 23, or 34 coupled to or combinable to the control device. Optionally, the control systems 19, 29, 33, and 58 additionally include at least one drive unit 24 and / or at least one modulator unit 35.

[0102] In the current configuration, the third and fourth optical elements 56 and 57 form optical resonators 16, 23, and 34. Control device 1 is connected to optical resonators 16, 23, and 34 via at least one optical waveguide 8 (e.g., optical fiber). Control systems 19, 29, 33, and 58, particularly control device 1, are connected to controller 18 in terms of signaling.

[0103] Optionally, both the projection system 46 and the illumination system 45 include more than two, particularly three, four, five, or more optical elements 52, 53, 56, 57. Optical resonators 16, 23, 34 are preferably formed by two optical elements arranged adjacent to each other in the beam path of the working light. The illumination system 45 can therefore also include one or more optical resonators 16, 23, 34. The optical resonators 16, 23, 34 of the projection system 46 and the illumination system 45 are preferably monitored by a single control system 19, 29, 33, 58 or a single control device 1. Optionally, the illumination system 45 includes a separate control device 1 or a separate control system 19, 29, 33, 58 assigned to it.

[0104] The advantage of frequency stabilization via control device 1 is that it allows for the detection or capture of changes in the corresponding optical resonators 16, 23, and 34, particularly changes in length, with exceptional accuracy and speed. Exceptional accuracy means that length or positional changes within the picometer range can be detected. Exceptional speed means that length or positional changes within the microsecond range can be detected.

[0105] As an example, if a change in the length of optical resonators 16, 23, 34 or a change in the position of the optical elements forming optical resonators 16, 23, 34 relative to each other is detected to be greater than a predefined limit, it is preferable to implement measures to correct or adjust, for example, the position or orientation of at least one optical element of resonators 16, 23, 34. In this case, correction is implemented such that the corrected length or position corresponds to a predefined setpoint length or a predefined setpoint position. Preferably, controller 18 drives at least one of optical elements 52, 53, 56, 57 or another element in projection system 42 configured to correct or adjust the orientation or position of optical elements 52, 53, 56, 57 or optical resonators 16, 23, 34.

[0106] Preferably, the control device 1 includes components for temperature regulation of the semiconductor substrate 2 and / or the Pound-Dreyfus-Hall systems 3, 4, 22, particularly for heating and / or cooling. Preferably, the control device 1 includes components for thermally insulating the semiconductor substrate 2 and / or the Pound-Dreyfus-Hall systems 3, 4, 22. Preferably, the control device 1 includes a housing in which the semiconductor substrate 2 and / or the Pound-Dreyfus-Hall systems 3, 4, 22 are at least partially disposed.

[0107] The use of control device 1 and / or control system 19, 29, 33, 58 is not limited to use with projection exposure equipment. Control device 1 and / or control system 19, 29, 33, 58 may also be used, for example, in or with optical coordinate measuring systems, in or with lidar (light detection and ranging) systems, or in or with optical coherence tomography (OCT) systems.

[0108] Preferably, the control system 19, 29, 33, 58 or the control device 1 includes a PID controller, wherein the D element of the PID controller is not equal to 0.

Claims

1. A control system (19, 29, 33, 58) for frequency control of laser modules (20, 21), comprising at least one laser module (20, 21) for generating laser radiation, at least one control device (1) coupled to or capable of being coupled to said at least one laser module (20, 21), and at least one optical resonator (16, 23, 34) coupled to or capable of being coupled to said at least one control device (1), wherein, The at least one control device (1) includes a semiconductor substrate (2), a first Pound-Dreyfus-Hall system implemented on the semiconductor substrate (2), and at least one second Pound-Dreyfus-Hall system implemented on the semiconductor substrate (2), wherein The at least one laser module (20, 21) is configured to be coupled to and decoupled from the first Pound-Dreyfus-Hall system of the at least one control device (1), and configured to be coupled to at least one second Pound-Dreyfus-Hall system of the at least one control device (1), and wherein The first Pound-Dreyfus-Hall system is coupled to the at least one optical resonator (16, 23, 34), and wherein the at least one second Pound-Dreyfus-Hall system is configured to be coupled to the at least one optical resonator (16, 23, 34), and wherein... The number of the first Pound-Dreyfus-Hall system and the at least one second Pound-Dreyfus-Hall system is greater than the number of the laser modules (20, 21) or optical resonators (16, 23, 34), and wherein... The laser radiation from the first Pound-Dreyfus-Hall system coupled to the laser modules (20, 21) and the laser radiation from the at least one second Pound-Dreyfus-Hall system coupled to the laser modules (20, 21) have a phase shift relative to each other, and wherein... The laser radiation frequencies or carrier frequencies of the first Pound-Dreyfus-Hall system coupled to the laser modules (20, 21) and the laser radiation frequencies or carrier frequencies of the at least one second Pound-Dreyfus-Hall system coupled to the laser modules (20, 21) are equidistant from each other.

2. The control system according to claim 1, characterized in that, At least one drive unit (24) is configured to drive the first Pound-Dreyfus-Hall system and at least one second Pound-Dreyfus-Hall system to perform coupling or decoupling.

3. The control system according to claim 2, characterized in that, The driving unit (24) is a matrix circuit (25).

4. The control system according to any one of claims 1 to 3, characterized in that, The at least one laser module (20, 21) is coupled to at least two of the first Pound-Dreyfus-Hall system and the at least one second Pound-Dreyfus-Hall system.

5. The control system according to claim 4, characterized in that, In order to generate the phase shift, the modulator unit (35) is connected between the at least one laser module (20, 21) and the first Pound-Dreyfus-Hall system, and between the at least one laser module (20, 21) and the at least one second Pound-Dreyfus-Hall system.

6. The control system according to claim 5, characterized in that, The modulator unit (35) includes a comb line spacing control unit (61).

7. The control system according to any one of claims 1 to 3, characterized in that, The control system includes an additional photodetector unit (30), wherein the photodetector unit (30) can be connected to or connected to a reference light source (31).

8. The control system according to any one of claims 1 to 3, characterized in that, The control system includes a first wavelength-selective optical switch (59) and at least one second wavelength-selective optical switch (60).

9. The control system according to any one of claims 1 to 3, characterized in that, The control system includes a PID controller, wherein the D element of the PID controller is not equal to 0.

10. The control system according to any one of claims 1 to 3, characterized in that, The first Pound-Dreyfus-Hall system and at least one second Pound-Dreyfus-Hall system are capable of being driven independently.

11. The control system according to claim 10, characterized in that, At least one controller (18) is configured to drive the first Pound-Dreyfus-Hall system and at least one second Pound-Dreyfus-Hall system.

12. The control system according to any one of claims 1 to 3, characterized in that, The first Pound-Dreyfus Hall system and the at least one second Pound-Dreyfus Hall system each include at least one drivable phase modulator unit (5) and / or at least one photodetector unit (7).

13. The control system according to any one of claims 1 to 3, characterized in that, The first Pound-Dreyfus-Hall system or the at least one second Pound-Dreyfus-Hall system includes at least one electronic component (9).

14. A method for operating a control system (19, 29, 33, 58) for frequency control of a laser module (20, 21), wherein the control system (19, 29, 33, 58) according to any one of claims 1 to 13 is implemented, the method comprising the steps of: a) Operate the first Pound-Dreyfus Hall system and the second Pound-Dreyfus Hall system of the control device (1); b) Couple the laser modules (20, 21) to one of the first Pound-Dreyfus-Hall systems of the control device (1); c) Detect at least one actual value of a predefined electrical parameter of the first Pound-Dreyfus-Hall system; d) Compare the at least one actual value with a predefined setpoint value; e) If the determined deviation between the at least one actual value and the setpoint value is greater than a predefined limit deviation, then the laser module (20, 21) is decoupled from the first Pound-Dreyfus-Hall system; f) Couple the laser modules (20, 21) to the second Pound-Dreyfus-Hall system. in The laser radiation from the first Pound-Dreyfus-Hall system coupled to the laser modules (20, 21) and the laser radiation from the second Pound-Dreyfus-Hall system coupled to the laser modules (20, 21) are phase-shifted relative to each other, and wherein... The laser radiation frequency or carrier frequency of the first Pound-Dreyfus-Hall system coupled to the laser modules (20, 21) and the laser radiation frequency or carrier frequency of the second Pound-Dreyfus-Hall system coupled to the laser modules (20, 21) are equidistant from each other.

15. A method for performing frequency control on a laser module (20, 21) of a control system (19, 29, 33, 58), wherein the control system (19, 29, 33, 58) according to any one of claims 1 to 13 is implemented, the method comprising the following steps: a) Couple at least one laser module (20, 21) to at least one of the first Pound-Dreyfus-Hall systems of the control device (1), b) Generate laser radiation through the at least one laser module (20, 21) and introduce the laser radiation into the first Pound-Dreyfus-Hall system; c) Introduce the laser radiation having the carrier frequency of the laser radiation into the phase modulator unit (5) of the control device (1) and generate at least one sideband. d) Divide the laser radiation into a first portion of radiation having a carrier frequency of the laser radiation and a second portion of radiation having a carrier frequency with a potential phase shift of the laser radiation; e) Superimpose the first portion of radiation and the second portion of radiation; f) Monitor a predefined deviation between the first portion of radiation and the second portion of radiation; g) If it is identified that the deviation between the first part of the radiation and the second part of the radiation is greater than a predefined deviation, then the carrier frequency of the laser radiation is controlled, wherein the carrier frequency is controlled to make it equal to the reference frequency; h) Decouple the at least one laser module from the first Pound-Dreyfus-Hall system; as well as i) Couple the at least one laser module to the at least one second Pound-Dreyfus-Hall system. in The laser radiation from the first Pound-Dreyfus-Hall system coupled to the laser module and the laser radiation from the at least one second Pound-Dreyfus-Hall system coupled to the laser module are phase-shifted relative to each other, and wherein... The laser radiation frequency or carrier frequency of the first Pound-Dreyfus-Hall system coupled to the laser module and the laser radiation frequency or carrier frequency of the at least one second Pound-Dreyfus-Hall system coupled to the laser module are equidistant from each other.

16. The method according to claim 15, characterized in that, The frequency control is implemented based on the drive comb line spacing control unit (61).

17. An illumination system (45) for a projection exposure apparatus (42) for EUV lithography, comprising: The housing (48) surrounding the interior, and at least two optical elements (52, 53) arranged in the housing (48), wherein the at least two optical elements (52, 53) form an optical resonator (16, 23, 34), characterized in that a control system (19, 29, 33, 58) is implemented according to any one of claims 1 to 13.

18. A projection system (46) for a projection exposure apparatus (42) for EUV lithography, comprising: The housing (49) surrounding the interior, and at least two optical elements (56, 57) arranged in the housing (49), wherein the at least two optical elements (56, 57) form an optical resonator (16, 23, 34), characterized in that a control system (19, 29, 33, 58) is implemented according to any one of claims 1 to 13.

19. A projection exposure apparatus (42) for EUV lithography, comprising: The lighting system (45) and projection system (46) are characterized by implementing a control system (19, 29, 33, 58) according to any one of claims 1 to 13.

20. The projection exposure apparatus (42) according to claim 19, characterized in that, The lighting system (45) is implemented according to claim 17 and / or the projection system (46) is implemented according to claim 18.

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