Method and laser system for compensating for misalignment

Abstract

The invention relates to a method (21) for operating a laser system (1) and a correspondingly embodied laser system (1). In the method (21), a misadjustment (13) of the laser system is continuously monitored automatically in normal operation of the laser system (1). Then, in the event of a recognized misadjustment (13), at least one operating parameter (8) of the laser system (1) is determined, a change of which has an opposite effect to the corresponding misadjustment (13). Then, at least one operating parameter (8) thus determined is automatically adapted in order to compensate for the recognized misadjustment (13).

Description

Technical Field

[0001] The present invention relates in particular to a method for operating a laser system and a corresponding laser system. Background Technology

[0002] Today, laser systems are used in a wide variety of applications. Increasingly higher demands are being placed on them, particularly in terms of power capability, accuracy, and reliability. However, modern laser systems, for example, used in industrial applications, can be significantly complex. This can lead to situations where such laser systems operate inaccurately according to the intended target, i.e., they are misaligned, out of tune, or incorrectly calibrated. This can occur, for example, due to changing environmental conditions, degradation of individual components, or mechanical movement of passive optical elements, such as due to vibration. Avoiding this using conventional methods is either impractical or can result in disproportionately high costs, thus necessitating periodic manual maintenance in such cases. This requires, when necessary, completely or partially shutting down the laser system or placing it in maintenance or calibration operation, which can lead to expenses and costs, as well as reduced overall efficiency or productivity. Therefore, improvements are expected. Summary of the Invention

[0003] The objective of this invention is to achieve particularly robust operation and exceptionally high precision of laser systems in a particularly simple and efficient manner.

[0004] This task is solved by the subject matter of the independent claim or the main claim and dependent claims. Other possible configurations of the invention are given in the dependent claims, the description, and the drawings. Features, advantages, and possible configurations set forth within the scope of the description for one subject matter of the independent claim can be at least similarly regarded as features, advantages, and possible configurations of the corresponding subject matter of the other independent claims, as well as features, advantages, and possible configurations of any possible combination of the subject matter of the independent claim when necessary in combination with one or more dependent claims in the dependent claims.

[0005] The method according to the invention can be used to operate a laser system or laser facility, or applied while operating a laser system or laser facility. The method includes multiple method steps that can be automatically implemented during the normal operation of the corresponding laser system. Here, normal operation refers to the operation of the laser system in routine, productive use, i.e., not maintenance operation, testing operation, or setup or calibration operation. That is, during normal operation, the laser system can operate as prescribed and, for example, at full power without other restrictions.

[0006] In the method according to the invention, misalignment or misfit of the laser system is continuously monitored. This can be a deviation from the predefined target or rated behavior of the laser system, such as misorientation of the generated or emitted laser beam, causing the laser beam to, for example, fail to hit a pre-defined target point. This can be identified, for example, by means of a corresponding monitoring camera and / or other sensor. Here, for example, the monitoring of misalignment can be performed periodically or continuously at a pre-defined frequency, and / or triggered, for example, by one or more predefined triggering events.

[0007] Furthermore, in the method according to the invention, in the case of identified misalignment, at least one operating parameter of the laser system is determined, the change of which has an effect opposite to the direction of the misalignment, i.e., the corresponding deviation from the rated behavior. In the present case, the change of this or one operating parameter refers to a change in the actual value and / or rated value of that operating parameter. For example, a list or table or family of characteristic curves or the like can be pre-given, from which automatically changeable, i.e., adaptable, operating parameters and corresponding effects or functions can be obtained or read.

[0008] Then, in another method step according to the invention, the at least one determined operating parameter is automatically adapted, i.e., changed, to fully or at least partially compensate for, i.e., equalize the identified misalignment. That is, here, the at least one operating parameter can be used as an adjustment or control parameter to fully or partially achieve or restore the pre-given target or rated behavior of the laser system. This can result in the final adapted value of the at least one operating parameter being different from its nominal rated value in the overall optimally calibrated state of the laser system, i.e., set in a manner different from the nominal rated value, or can be set in a manner different from the nominal rated value.

[0009] The adaptation to the at least one operating parameter may mean or include a one-time or individual adaptation or continuous adjustment. In the latter case, for the at least one operating parameter or each operating parameter, the laser system may have a corresponding regulator, such as a PID regulator or a fuzzy regulator.

[0010] Because operating parameters can be determined and used to compensate for misalignment in the method according to the invention, and these parameters can be automatically adapted during the continuous normal operation of the laser system, the compensation or elimination of misalignment can be performed non-invasively. Therefore, there is no need to shut down the laser system, nor is manual maintenance or post-calibration required. Consequently, particularly robust or reliable continuous, i.e., permanent, operation of the laser system can ultimately be achieved with exceptionally high efficiency, i.e., a particularly high share of production time or useful time. This, in turn, can reduce the operating or production costs associated with the laser system compared to conventional methods.

[0011] This invention is based on the understanding that modern laser systems, due to their significant complexity, typically have a large number of different settable operating parameters, which can directly or indirectly affect different characteristics or operating states of the laser system, and thus enable corresponding, at least indirectly, control. Therefore, for example, if the true cause of the identified misalignment does not lie in the ultimately adapted operating parameters, the identified misalignment can also be effectively eliminated. Thus, with this invention, for example, even if the elimination of the true cause of the misalignment cannot be easily achieved, or for example, cannot be achieved without interrupting the operation of the laser system, but rather, for example, only within the framework of maintenance or repair intervention, effective, especially uninterrupted, operation or continued operation can be achieved during or after a laser system misalignment. Furthermore, this can be achieved particularly simply, with low cost and cost-effectiveness, because in principle, it is already possible to automatically set the corresponding operating parameters affecting the behavior of the laser system in conventional laser systems, or such automatic settableness can be achieved at relatively low cost. This can be achieved, for example, purely in a software-based manner, i.e., by means of corresponding control or adjustment programs. However, similarly, compared to designs that are less susceptible to misalignment and include appropriate control and management of environmental conditions, or the use of more precise and robust servo motors for optical elements, or the like, additionally required hardware (such as additional electronic regulators or valves or heating or cooling devices) can generally be installed relatively simply and cost-effectively in laser systems or added to existing laser systems.

[0012] The present invention also relates to a laser system or laser facility having at least one laser source, a conditioning or influencing device for conditioning or influencing a laser beam generated by the laser source, and optics, wherein the at least one laser source is at least one light source or beam source for laser. Here, the influencing device and optics are connected downstream of the laser source in the laser system along a predetermined beam propagation direction of the laser beam. In the present sense, conditioning or influencing a laser beam may, for example, mean or include amplification or modulation of the laser beam, or wavelength conversion, or chopping of the laser beam into individual laser pulses and / or the like. That is, for example, the conditioning or influencing device may be or may include an amplifier, and / or a modulator, and / or a wavelength converter, and / or a chopper. Furthermore, the laser system according to the invention has a monitoring device for automatically identifying misalignments of the laser system (particularly misalignments in the orientation and / or pre-defined characteristics of the laser beam), and a control device for controlling and / or adjusting at least one operating parameter of the laser system. The laser system according to the invention is hereby configured for implementing, particularly automatically or partially automatically, the method according to the invention. That is, the laser system according to the invention can be, or corresponds to, the laser system mentioned in the context of the method according to the invention. Similarly, the laser system according to the invention may have additional components or functions not explicitly mentioned herein, such as an electrical power supply, an RF power source or RF power supply (RF: radio frequency), a cooling system, a gas system, and / or the like. These components may form additional, independent devices of the laser system, or may, for example, be at least partially integral to the influencing device.

[0013] In one possible configuration of the invention, the laser system is configured to identify unintentional changes in the orientation of the laser beam and / or the output caustic surface and / or the laser power of the laser system as misalignment. A changed orientation of the laser beam, i.e., misalignment, can, for example, mean a displacement (Verschiebung) or tilt of the corresponding optical axis of the laser system. Such a changed orientation can be determined, in particular, at or after the output of the driving laser, excitation laser, amplifier, or preamplifier of the laser system. Similarly, the output caustic surface is determined, particularly in the beam propagation direction, after the preamplifier or main amplifier, especially after the amplifier through which the laser beam ultimately passes in the beam propagation direction of the laser system. The laser power can also be determined after one or the last amplifier of the laser system. Likewise, the laser power can be determined, for example, at multiple locations, particularly after and / or before multiple or all amplifiers of the laser system. The latter allows for more accurate localization of the misalignment and, if necessary, better coordinated responses or measures, i.e., selection and / or adaptation of the corresponding fit to the at least one operating parameter. Therefore, compensation for the mismatch can be achieved or reached when necessary using a minimum fit. Typically, based on the understanding upon which this invention is based, the mismatch described herein can be effectively influenced by one or more matched operating parameters, and is therefore particularly well suited for the applications of this invention.

[0014] In another possible configuration of the invention, the influencing device includes at least one amplifier for amplifying the laser beam, i.e., the intensity or power of the laser beam. The laser system is then configured to determine and adapt at least one operating parameter of the amplifier. In particular, the corresponding misalignment can be compensated using only one or more operating parameters of the amplifier or the means of feeding or supplying the amplifier. It has been shown that the amplifier or a single amplifier can provide multiple possibilities for effectively influencing the laser beam and thus compensating for the misalignment. Simultaneously, due to the use of one or more operating parameters of the amplifier, misalignment compensation can be achieved without moving the optics or interfering with the laser source, i.e., the actual generation of the laser. This can be particularly advantageous because optics can typically only be moved with limited precision, or the possibility of precise movement of the optics can lead to particularly high costs, and changes to the operating parameters of the laser source are generally not feasible.

[0015] In another possible configuration of the invention, the influencing device has multiple amplifiers, i.e., multiple amplifiers or amplifier stages connected in series, for amplifying the laser beam generated by the laser source. The laser system is then configured to automatically distribute the adaptation of at least one operating parameter across the multiple amplifiers. Here, for example, the total range of determined operating parameter adaptations can be distributed across the multiple amplifiers, and / or different operating parameters can be adapted to different amplifiers. This distribution can be uniform or non-uniform. For example, in the case of uniform distribution, if a determined operating parameter should be changed by a total of 10%, the same operating parameter can be changed by 5% in the first amplifier and similarly by 5% in the second amplifier. If two different operating parameters should be adapted, for example, the parameter can be changed in the first amplifier (i.e., adapting the first operating parameter) and in the second amplifier (i.e., adapting the second operating parameter). With the configuration proposed herein, on the one hand, excessive or unnecessarily strong changes in the behavior of individual amplifiers can be prevented. Thus, robust amplifier function can be maintained particularly reliably, and unexpected side effects from large changes in the operating parameters of individual amplifiers can be avoided. On the other hand, this allows for a particularly wide range of adaptations or compensation for particularly large misalignments. Thus, for example, the maximum adaptation or shift range for a given operating parameter may be limited in a single amplifier. Then, by fully utilizing the possible adaptation or shift ranges of multiple amplifiers for the same and / or multiple different operating parameters, a correspondingly stronger effect can be achieved.

[0016] According to another possible configuration of the invention, the at least one operating parameter is or controls a characteristic of the laser system that differs from the mechanical or angular position, or orientation, of the optical elements of the laser system that are loaded by the laser beam, i.e., directed towards or penetrated by it. In the context of this invention, the optical elements can be components of an optical device, particularly passive components, such as mirrors, lenses, or prisms. In other words, the position or orientation of the optical elements is not altered by adapting or changing the at least one operating parameter. More precisely, the at least one operating parameter can be, for example, an electrical operating parameter and / or a thermal operating parameter and / or a material parameter. With the configuration proposed herein, the laser system does not require the typically very expensive or cost-intensive possibility of automatic, precise setting for the optical elements, and automatic compensation for misalignment can still be achieved. Therefore, robust and reliable operation of the laser system can be achieved particularly simply and cost-effectively. Furthermore, this allows for or supports a particularly simple and compact construction of the laser system when necessary.

[0017] In another possible configuration of the invention, the laser system is configured to determine, i.e., select, at least one operating parameter from a pre-given list of operating parameters. This pre-given list includes at least: gas composition, gas replacement maintenance time, gas pressure, gas volumetric flow rate, gas temperature, coolant temperature, coolant volumetric flow rate, RF power, amplifier turn-off time, and pre-pulse laser power. The gas composition, gas replacement maintenance time, gas volumetric flow rate, gas temperature, and gas pressure can be applied to the volume within the laser system irradiated by the laser beam or the laser. There, these operating parameters can, for example, influence the refractive index or amplification factor, or contaminants or the like, to affect the laser beam. Whether, and if necessary, which or several of these operating parameters can be influenced in a given laser system can depend on the specific configuration. Thus, for example, in a laser system with continuous gas flow, the gas pressure can be adapted accordingly and continuously. In other laser systems, the gas pressure can be adapted, if necessary, only during or preferably during gas replacement, such as gas replacement combined with gas analysis.

[0018] To adapt to the gas composition, i.e., the gas mixture, additional helium can be introduced into the corresponding volume, or similarly. Adaptation of stack gas replacement maintenance time can, for example, fully utilize contamination and / or diffusion effects. To adapt, for example, the gas composition and / or gas pressure and / or gas temperature, molecular sieves, such as those made of zeolite materials, can be used, arranged in or on the corresponding gas volume. These molecular sieves can, in particular, be equipped with controllable heating and / or cooling devices. Thus, for example, the adsorption rate or the removal of previously adsorbed molecules can be automatically controlled. For example, the RF power can be the RF input power or RF supply power and / or reflected power of an amplifier, as mentioned elsewhere. This can be adapted, for example, by controlling the matching network between the RF power source and the device supplied with RF power, especially the amplifier. Similarly, here, adaptation can be performed or achieved, for example, by correspondingly controlling the duty cycle of the RF power source, especially in the case of a discontinuously pumped amplifier.

[0019] In summary, the operating parameters mentioned herein offer various, relatively easy-to-implement, or fully-utilizable, effective possibilities for compensating for the effects of misalignment. Adaptation to at least some of the mentioned operating parameters can be implemented purely in a software-based manner and therefore can be easily added to existing laser systems. The hardware or components that might be required for some of the mentioned operating parameters can be integrated into existing laser system designs relatively cost-effectively and simply compared to conventional laser systems.

[0020] In another possible configuration of the invention, the laser system is configured to automatically limit the adaptation of at least one operating parameter such that the adaptation does not fall below a predetermined lower threshold for the laser output power of the laser system. In other words, the laser system can be configured to specify or execute the at least one operating parameter based on, or taking into account, the power of the laser beam or laser output by the laser system. For example, the laser output power considered here could be the power of the laser beam at the laser system's mentioned, particularly the last amplifier, or directly after that amplifier, or in a target region where the laser beam generated by the laser system is pre-directed. Here, the laser system can also be configured to control or limit the adaptation of the at least one operating parameter such that the laser power remains within a predetermined range. In other words, the laser system can then consider not only a predetermined minimum power to be followed, but also a predetermined maximum power to be followed for the laser beam. Since the adaptation of different operating parameters can affect the laser output power, it is necessary to limit the adaptation or range of movement of the operating parameter accordingly.

[0021] If a larger fit or a larger range of movement of the operating parameter is nominally required to compensate for a identified misalignment, the laser system can be configured to additionally or alternatively determine and fit at least one other operating parameter that has a minor, no, or opposite effect on the laser output power. That is, here, the maximum fit range and / or the selection of one or more operating parameters to be fitted can be limited by a pre-defined minimum amplification to be followed by one of the amplifiers of the laser system, or elsewhere mentioned. That is, the pre-defined threshold can then be effectively pre-defined or associated with the minimum amplification of the amplifier, for example, also taking into account and incorporating losses occurring after the amplifier. By considering the laser output power in compensating for misalignment as proposed in the configuration described herein, it can be guaranteed that the laser system can always perform its intended task. For this purpose, for example, achieving at least a pre-defined minimum laser output power or a corresponding minimum amplification can be prioritized over complete compensation for the identified misalignment. In general, the configuration proposed herein can also benefit the particularly robust and reliable operation of the laser system.

[0022] In another possible configuration of the invention, the laser system is configured to adapt multiple operating parameters of the laser system in combination to compensate for corresponding misalignments. Specifically, the laser system can be configured to perform this based on the magnitude or intensity of the corresponding identified misalignment. This could mean, for example, that multiple operating parameters are determined and adapted to compensate for the misalignment only when the misalignment exceeds a predetermined magnitude or intensity, or only when a single operating parameter needs to be changed beyond a predetermined absolute or relative value or amount to fully compensate for the misalignment. Thus, smaller misalignments can be compensated more easily when necessary, while larger misalignments can be compensated without excessively altering a single operating parameter, thereby avoiding or reducing undesirable side effects when necessary. Furthermore, the configuration proposed herein can also automatically compensate for misalignments that cannot be fully compensated by adapting only a single operating parameter. Therefore, ultimately, particularly robust, reliable, and accurate operation of the laser system can be achieved or guaranteed, especially over a long period, when necessary.

[0023] In another possible configuration of the invention, the laser system is configured to adapt the at least one operating parameter by means of a pre-given model, particularly predictive adjustment. In other words, a model can be used here, for example, that can model or simulate the laser system or its behavior, specifically the effect of adapting or changing one or more operating parameters of the laser system. That is, therefore, then, if necessary, in multiple different parameterized simulations or model traversals, before actually adapting the operating parameters of the laser system, the range or extent of at least one operating parameter to be adapted and / or the adaptation of at least one operating parameter required to compensate for identified misalignments can be determined. Here, the model can also, if necessary, use or consider the corresponding current operating state of the laser system as an input or boundary condition. The configuration proposed herein enables particularly accurate and secure adaptation of the at least one operating parameter, and thus enables or supports particularly robust, prescribed, and low-interruption operation of the laser system.

[0024] As a basis or input for a model, one or more sensitivity curves can be used for a laser system, indicating, in particular, the effect of changes on one or more operating parameters based on the magnitude of the corresponding changes. For example, this type of sensitivity curve can be pre-defined, determined during operation, or adapted or updated based on data recorded during operation. For example, corresponding data can be obtained during the operation of multiple laser systems, i.e., measurement or sensor data recorded during operation, from which the sensitivity curves can be generated. Therefore, for a large number of different situations or conditions, the corresponding data can be obtained particularly quickly and easily, making the corresponding sensitivity curves correspondingly robust and capable of covering a particularly large state space or parameter space. If necessary, the corresponding data can be obtained without specific measurement or test runs of one or more laser systems, because in actual use, variations or fluctuations in different operating parameters, operating states, and conditions under which one or more laser systems operate are almost inevitable. In other words, the corresponding data can be obtained based on natural or unavoidable variations during the field use or production operation of one or more laser systems.

[0025] In one possible extension of the invention, the model is based solely on operational data, such as measurement data or sensor data, recorded from previous operation of the corresponding laser system itself. In other words, the model can be used only for the adaptation of one or more operating parameters to model or simulate the fit of the laser system to which identified misalignments should be compensated. That is, facility- or system-specific models, or system-specific models, can be used for the respective laser systems. Therefore, the individual characteristics or peculiarities of the respective laser system, which are not necessarily known in detail but can determine or influence the behavior of the respective laser system, can be automatically taken into account. This, in turn, enables a particularly high level of accuracy in the model and thus allows for the particularly precise determination of the fit necessary to compensate for the corresponding misalignments for one or more operating parameters. For this purpose, the laser system can be equipped with corresponding sensors or data detection devices to detect the current value or time-varying curve of one or more operating parameters of the corresponding laser system, as well as the corresponding characteristics or behavior or operating state of the laser system, as the basis or parameters of the model and / or the sensitivity curve on which the model is based. These could be, for example, sensors or data detection devices used for misalignment and operating parameters mentioned elsewhere.

[0026] In another possible configuration of the invention, the laser system additionally includes a moving device for directional movement of at least one element of the optics, particularly a passive element. That is, by means of this moving device or a corresponding moving device, one or more optical elements mentioned elsewhere, such as mirrors, lenses, prisms, or the like, can be moved automatically. This can, for example, mean or include translation, rotation, tilting, and / or similar movements. For example, the moving device may include a servo motor, particularly an electric servo motor, a coil, or an electromagnet for electromagnetic movement, a linear actuator, and / or the like. In the configuration proposed herein, the laser system is configured to compensate, at least as extensively as possible, for the identified misalignment only when maximum adaptation, i.e., by fully utilizing the maximum range of change or movement of the at least one operating parameter, is insufficient to fully compensate for the misalignment. That is, here, the moving device or possibility for compensating for misalignment by moving or changing the orientation of at least one element of the optics can be used or implemented as a fallback mechanism. For example, if compensation for offset by means of corresponding settings or adaptations of the operating parameters of one or more of the amplifiers mentioned elsewhere would result in, for example, the predetermined minimum amplification no longer being reached, then such a backoff scheme can be used. With the configuration presented herein, on the one hand, particularly accurate and flexible compensation can be achieved for relatively small offsets. However, on the other hand, particularly large offsets can ultimately also be compensated, at least as long as these offsets manifest as an error in the orientation or propagation direction of the laser beam.

[0027] Other features of the invention can be derived from the following description and accompanying drawings. The features and combinations of features mentioned above in the specification, as well as the features and combinations of features shown separately in the following description and / or accompanying drawings, may be used not only in the combinations given respectively, but also in other combinations or alone, without departing from the framework of the invention. Attached Figure Description

[0028] The attached diagram shows: Figure 1 A schematic diagram of a laser system with automatic misalignment compensation is shown. Figure 2 A schematic graph illustrating the effect of different operating parameters of a laser system on laser beam alignment is shown. Figure 3 A schematic graph is shown to illustrate the range in which laser beam alignment errors can be compensated; and Figure 4 An exemplary schematic process plan for operating a corresponding laser system is shown. Detailed Implementation

[0029] Components that are identical or have the same function are given the same reference numerals in the accompanying drawings.

[0030] Figure 1 A schematic and simplified diagram of a laser system 1 is shown. Here, the laser system 1 includes a laser source 2, which can generate one or more laser beams 3. Here, the laser source 2 can be a single beam source or light source, or it can include multiple beam sources or light sources. Similarly, the laser source 2 can include one or more preamplifiers.

[0031] The resulting laser beam 3 can be amplified within the laser system 1. For this purpose, the laser system 1 has at least one amplifier 4b. Amplifier 4b can be a single amplifier, or it can schematically represent multiple amplifiers or amplifier stages connected in series, for example.

[0032] Furthermore, the laser system 1 has an optical component, which is exemplarily identified here by a passive optical element 5 connected downstream of the amplifier 4b. The optical component may also have additional optical elements 5, which may also be arranged, for example, between the laser source 2 and the amplifier 4b. The optical component may include, for example, one or more lenses and / or one or more mirrors or the like as optical element 5. Additional active optical elements may also be included, such as acousto-optic modulators and / or electro-optic modulators.

[0033] Laser system 1 can, for example, be configured for EUV light generation. Here, the laser can be directed onto a target material or reactive material, such as a tin droplet, which can then emit EUV radiation. For efficient and stable operation of this process, the reactive material needs to be accurately irradiated by the laser target. Therefore, typically, laser system 1 is calibrated accordingly at a designated location of use. With proper calibration, the laser beam 3, amplified by amplifier 4b, can be output from laser system 1 as a correspondingly calibrated laser beam 6, which can then strike a pre-defined target 7, i.e., the aforementioned reactive material or a corresponding spatial area.

[0034] Amplifying the laser beam 3 within a feasible wavelength range with the highest possible efficiency and amplification power can be a complex task. Therefore, the laser system 1 may have or use a corresponding number of different operating parameters 8, schematically indicated herein. Exemplarily, multiple operating parameters are indicated herein, particularly relating to amplifier 4b. This may be, for example, a settable characteristic of a gas supply, RF power supply or high-frequency power supply, a cooling device, a molecular sieve capable of heating and / or cooling, and / or the like. To monitor and control or regulate these operating parameters 8, or their actual and rated values, the laser system 1 also has a corresponding control device 9. The control device 9 may, for example, be coupled to a device and / or sensor associated with the operating parameter 8 via a corresponding interface 10. To implement the measures or control processes described herein, the control device 9 may have corresponding electronics and / or circuit logic, schematically indicated herein by a processor 11 and a computer-readable data storage 12 coupled thereto. The processor 11 may, for example, be a microprocessor, microchip, microcontroller, or the like. The data storage 12 may store, for example, a corresponding running program or computer program, as well as a model and / or other data for the laser system 1, which may be pre-given if necessary. The model or the other data may then be implemented or processed by the processor 11.

[0035] In practice, during the operation of complex systems like laser system 1, unexpected situations inevitably arise, in which deviations from the optimal alignment of the corresponding system occur. This can have various causes, such as changes in environmental conditions, thermal effects that can cause changes in the thermal expansion of components of laser system 1, degradation or defects in individual components, mechanical movement of, for example, at least one passive optical element 5, unintentional alteration or incorrect setting of one of the operating parameters 8, and / or similar causes. Therefore, misalignment 13 can thus occur, as illustrated here. Such misalignment 13 can, for example, result in the production of a correspondingly misaligned laser beam 14 instead of the aligned laser beam 6, which is directed at or hits an incorrect or undesirable target 15 that is different from or does not hit the rated target 7.

[0036] In principle, this type of misalignment 13 can be eliminated or corrected by shutting down the laser system 1 or placing the laser system in a special calibration operating mode and then performing manual calibration. However, since this is laborious and may unintentionally interrupt the productive operation of the laser system 1, the laser system 1 is hereby configured to automatically compensate for the corresponding misalignment 13. This is achieved here by automatically adapting the settings or operating conditions of the laser system 1, in particular the settable operating parameters 8 of the optical amplifier 4b, taking into account pre-given requirements or boundary conditions as necessary.

[0037] To achieve this automatic adaptation, the laser system 1 also includes a monitoring device 16 for automatically identifying the misalignment 13. Furthermore, the control device 9 is configured to determine one or more of the operating parameters 8 that can be adapted, i.e., changed in value to compensate for the corresponding identified misalignment 13, and to then automatically adapt the corresponding at least one operating parameter 8 accordingly. Additionally, the laser system 1 also includes an automatically controllable moving device 17 for moving, particularly mechanically or geometrically, at least one optical element 5. This moving device 17 can also be automatically controlled by the control device 9.

[0038] Since it is not always easy to see within which ranges the operating parameters 8 can be moved without hindering or excessively impairing the function or task of the laser system 1, and what specific effects changes in one or more of the operating parameters 8 have on the characteristics or operation of the laser system 1, i.e., on laser beam orientation, a corresponding sensitivity analysis can be performed first. This can be done during the corresponding measurement or test runs or based on fluctuations or changes in the operating parameters 8 during continuous productive operation of the laser system 1. To illustrate, Figure 2 A schematic graph is shown. A plane extending in the x and y directions of space is shown here, which, for example, may be perpendicular to the calibrated laser beam 6 within the range of the nominal target 7. Correspondingly, the nominal target 7 is located at the center of the shown plane. Different sensitivity curves 18 are shown here, each indicating how a change in one of the configurable operating parameters 8 affects the laser beam orientation, i.e., laser beam alignment. It can be seen that different adaptations of the operating parameter 8 can result in different displacements in the x-direction and / or y-direction.

[0039] In practice, multiple operating parameters in operating parameter 8 can be set simultaneously or in combination. For example... Figure 3As schematically shown, this results in a corresponding possible range of movement or compensation 19. This compensation range 19 indicates a surface or spatial range within which the misalignment 13 can be compensated by automatically adapting to one or more of the operating parameters in the operating parameters 8. To further illustrate, a displacement 20 accompanying the misalignment 13 is shown here, causing the corresponding misaligned laser beam 14 to no longer hit the nominal target 7, but instead hit the corresponding erroneous target 15. Here, the erroneous target 15 is located within the compensation range 19. This means that the corresponding misalignment 13 can be compensated by adapting one or more of the operating parameters in the operating parameters 8 in a suitable manner according to the corresponding sensitivity curve 18, so that the nominal target 7 is subsequently hit again.

[0040] If the erroneous target 15 is outside the compensation range 19 under a large misalignment 13, the erroneous target 15 can be shifted closer to the rated target 7 if necessary by adapting one or more of the operating parameters in the operating parameters 8 accordingly, without ultimately reaching the rated target completely.

[0041] To further illustrate, Figure 4 An exemplary schematic flow plan 21 for operating laser system 1 is shown. In this method, in method step S1, data indicating the behavior and operating status of laser system 1 under different values ​​of operating parameter 8 may first be recorded or collected. Here, for example, the current environmental conditions and / or other parameters may also be detected. Depending on the requirements, the relevant data may be detected based solely on laser system 1 or based on one or more different laser systems 1. As indicated herein by the loop-like path, method step S1 may be performed repeatedly or continuously.

[0042] Based on the data collected in method step S1, the sensitivity curve 18 or the corresponding model of laser system 1 can be generated in method step S2.

[0043] Then, in method step S3, the possible compensation range 19 can be determined.

[0044] Then, during the continuous normal or productive operation of the laser system 1, monitoring of the misalignment 13 can be performed continuously or periodically in method step S4. For this purpose, for example, the rated target 7 and its surrounding range, which corresponds at least to the compensation range 19, can be observed using a monitoring device 16. For this purpose, the monitoring device 16 can be, for example, a camera or includes a camera. Similarly, for this purpose, a portion of the laser can be directed to the monitoring device 16 or a corresponding camera after leaving the amplifier, particularly after passing through an optics device or at least one optical element 5, in order to identify the misalignment 13. Monitoring of other types of misalignment 13 can also be performed using the monitoring device 16. For this purpose, for example, the monitoring device 16 can monitor the laser power at or after the output of the amplifier 4b using a corresponding sensor.

[0045] Then, in response to the identified misalignment 13, in method step S5, the control device 9 determines in what manner or within what range the operating parameters 8 can be adapted to compensate for the identified misalignment 13, and the adaptation can be performed automatically if necessary. If it is found here that the misalignment 13 cannot be fully compensated by adapting one or more operating parameters 8, the moving device 17 can be additionally or alternatively operated automatically to compensate for the misalignment 13. When the adaptation of at least one operating parameter 8 is combined with the movement of at least one optical element 5 by means of the moving device 17, the latter can be minimized if necessary. Thus, for example, when using anisotropic or optical element 5 that operates according to the direction of light incidence, corresponding undesirable effects on the laser can be avoided or minimized.

[0046] For example, during the continuous operation of the laser system 1, the automatic adaptation of the operating parameters 8 and / or the moving device 17 can be performed continuously or as a continuous adjustment. For this purpose, the control device 9 can form or implement a corresponding regulator, or the laser system 1 can have at least one corresponding regulator.

[0047] According to the method presented herein, one or more setting or control parameters of the laser system 1, particularly those of the amplifier 4b, can be automatically adapted to compensate for, i.e., correct, the offset 13 at or after the output of the amplifier 4b, without significantly affecting other important output parameters. The latter can be achieved, for example, by limiting the compensation range 19 accordingly based on pre-given requirements or boundary conditions. In the case of automatic compensation for the offset 13 presented herein, the corresponding cause of the offset may or may not be eliminated, depending on the corresponding cause and the controllability or setting possibilities of the laser system 1.

[0048] In summary, the described examples demonstrate how laser beam alignment control can be achieved and applied on laser facilities, for example, through amplifier settings.

[0049] List of reference numerals 1. Laser System 2. Laser source 3. Laser beam 4. Affecting devices 4b amplifier 5 Optical Device Components 6. Adjusted laser beam 7 Rated Target 8. Operating parameters 9. Control device 10 interfaces 11 processors 12 Data Storage 13 Disorders 14 Misaligned laser beam 15 Incorrect Targets 16. Monitoring devices 17. Mobile devices 18 Sensitivity Curve 19. Scope of Compensation 20 displacement 21 Process Planning S1-S5 Method Steps

Claims

1. A method (21) for operating a laser system (1), wherein, During normal operation of the laser system (1), automatically: - Continuously monitor the misalignment (13) of the laser system (1). - In the event of an imbalance (13), determine one of the following operating parameters (8) of the laser system (1): a change in the operating parameter has the opposite effect to the imbalance (13). - Adapt the determined operating parameters (8) to compensate for the identified misalignments (13).

2. A laser system (1), particularly a laser system for generating EUV light, the laser system having at least one laser source (2), an influencing device (4) and an optical component (5), a monitoring device (16) and a control device (9), the influencing device being used to influence the laser beam (3) generated by the laser source (2), the influencing device and the optical component being connected downstream of the laser source (2), the monitoring device being used to identify misalignment (13) of the laser system (1), wherein, The laser system (1) is configured to implement the method (21) according to claim 1.

3. The laser system (1) according to claim 2. Its features are, The laser system (1) is configured to identify changes in the orientation of the laser beam (6, 14) and / or changes in the output caustic surface and / or changes in laser power as misalignment (13).

4. The laser system (1) according to claim 2 or 3. Its features are, The influencing device (4) has an amplifier (4b) for amplifying the laser beam (3), and the laser system (1) is configured to determine and adapt an operating parameter (8) of the amplifier (4b) as the operating parameter (8).

5. The laser system (1) according to any one of claims 2 to 4. Its features are, The influence device (4) has multiple amplifiers (4b), and the laser system (1) is configured to distribute the adapter onto the multiple amplifiers (4b).

6. The laser system (1) according to any one of claims 2 to 5. Its features are, The operating parameter (8) is or controls the following characteristics of the laser system (1): the characteristics are different from the mechanical position of the optical device element (5) loaded by the laser beam (6, 14).

7. The laser system (1) according to any one of claims 2 to 6. Its features are, The laser system (1) is configured to determine the operating parameters (8) from the following list: gas composition, gas temperature, gas pressure, gas volumetric flow rate, gas replacement and maintenance time, coolant temperature, coolant volumetric flow rate, RF power, amplifier turn-off time, and pre-pulse laser power.

8. The laser system (1) according to any one of claims 2 to 7. Its features are, The laser system (1) is configured to limit the one operating parameter (8) so that it is not lower than a pre-given threshold for laser output power.

9. The laser system (1) according to any one of claims 2 to 8. Its features are, The laser system (1) is configured to, in particular, adapt multiple operating parameters (8) in combination to compensate for the misalignment (13) based on the magnitude of the identified misalignment (13).

10. The laser system (1) according to any one of claims 2 to 9. Its features are, The laser system (1) is configured to adapt the operating parameters (8) by means of adjustment based on a pre-given model, especially predictive adjustment.

11. The laser system (1) according to claim 10. Its features are, The model is based on the operational data recorded in previous runs of only the corresponding laser system (1).

12. The laser system (1) according to any one of claims 2 to 11. Its features are, The laser system (1) additionally has a moving device (17) for directional movement of at least one element (5) of the optical device (5), the laser system being configured to compensate for the misalignment (13) additionally or alternatively by means of the moving device (17) only when the identified misalignment (13) cannot be fully compensated by maximally adapting the operating parameters (8).

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