Free electron laser, light source device and photoetching machine system

Abstract

The invention relates to a free electron laser, a light source device and a photoetching machine system. The free electron laser comprises a resonant cavity; a first undulator group, the first undulator group is arranged in a manner that an emergent light path is located on a resonant light path of the resonant cavity, the first undulator group is configured to interact with an electron beam to generate modulated light radiation, and the modulated light radiation is configured to modulate the electron beam; and a second undulator group, the second undulator group being arranged such that its emergent light path is located outside the resonant light path of the resonant cavity, the second undulator group being located downstream of the first undulator group, and the second undulator group being configured to interact with the modulated electron beam to generate target optical radiation.

Description

Technical Field

[0001] This disclosure relates to the field of optical technology, and more specifically, to a free-electron laser, a light source device, and a lithography system. Background Technology

[0002] The world has entered an era of information and intelligence, with various electronic devices playing a wide role in production and daily life. Against this backdrop, high-end chip manufacturing has become increasingly important. Correspondingly, large-scale chip manufacturing has become a strategic and fundamental industry for a nation. Currently, chip manufacturing technology has entered the nanoscale. Extreme ultraviolet (EUV) lithography technology has become the key to achieving large-scale manufacturing of chips or integrated circuits at 7nm and below.

[0003] Currently, EUV lithography machines primarily use EUV light with a wavelength of 13.5nm. One approach involves generating EUV light using "Laser-produced plasma (LPP)" technology. Specifically, the basic principle of an LPP-EUV light source is to use a high-power carbon dioxide laser to bombard liquid tin to generate plasma, thereby producing EUV light with a wavelength of 13.5nm. Under the LPP technology approach, in a recent EUV lithography machine, a carbon dioxide gas laser of over 20kW bombards carefully optimized liquid tin droplets, achieving an output of EUV light power approaching 500W. However, this power only just meets the commercial standard for 3nm mass production and is far from satisfying the needs of the entire chip manufacturing industry. Therefore, there is an urgent need to develop new high-power EUV light sources to promote the development and large-scale application of EUV lithography technology. Summary of the Invention

[0004] One of the purposes of this disclosure is to provide a free-electron laser, a light source device, and a lithography system.

[0005] According to a first aspect of this disclosure, a free-electron laser is provided, comprising:

[0006] Resonant cavity;

[0007] A first undulator group is arranged such that its outgoing optical path is located on the resonant optical path of the resonant cavity, and the first undulator group is configured to interact with the electron beam to generate modulated optical radiation, wherein the modulated optical radiation is configured to modulate the electron beam; and

[0008] The second undulator group is arranged such that its outgoing optical path is outside the resonant optical path of the resonant cavity, the second undulator group is located downstream of the first undulator group, and the second undulator group is configured to interact with the modulated electron beam to generate target light radiation.

[0009] In some embodiments, the resonant cavity is configured to capture modulated optical radiation but not target optical radiation.

[0010] In some embodiments, the free-electron laser further includes:

[0011] A first electron beam guiding component is located upstream of the first undulator group and is configured to guide an electron beam to the first undulator group to interact with the first undulator group.

[0012] In some embodiments, the first electron beam guiding component includes:

[0013] A first diode magnet group, comprising one or more first diode magnets, is configured to guide an electron beam from outside the resonant optical path of the resonant cavity to the resonant optical path.

[0014] In some embodiments, the first electron beam guiding component further includes:

[0015] A first quadrupole magnet is located between the first dipole magnet group and the first undulator group. The center of the first quadrupole magnet is located in the direction of electron beam travel, and the first quadrupole magnet is configured to focus the electron beam.

[0016] In some embodiments, the free-electron laser further includes:

[0017] A second electron beam guiding component is located between the first undulator group and the second undulator group, and is configured to guide an electron beam to the second undulator group and modulate the spatial structure of the electron beam into the target structure.

[0018] In some embodiments, the target structure of the electron beam is a periodic structure with alternating dense and sparse areas, wherein the period of the target structure is equivalent to the wavelength of the target light radiation.

[0019] In some embodiments, the second electron beam guiding component includes:

[0020] The second diode magnet group, comprising one or more second diode magnets, is configured to guide an electron beam from the resonant optical path of the resonant cavity to outside the resonant optical path and modulate the spatial structure of the electron beam into a target structure, wherein the first undulator group and the second undulator group are arranged along the same extending direction.

[0021] In some embodiments, the second electron beam guiding component includes:

[0022] A second quadrupole magnet, the center of which is offset laterally in a direction perpendicular to the direction of electron beam travel, so that the direction of electron beam travel is deflected toward the second undulator array; and

[0023] The third dipole magnet group includes one or more third dipole magnets, the third dipole magnet group is located between the second quadrupole magnet and the second undulator group, and the third dipole magnet group is configured to modulate the spatial structure of the electron beam into the target structure;

[0024] The first undulator group and the second undulator group are arranged along different extension directions.

[0025] In some embodiments, the second quadrupole magnet is configured to deflect the direction of travel of the electron beam by 30–100 μrad or 100–300 μrad.

[0026] In some embodiments, the resonant cavity is formed by a first reflective component and a second reflective component disposed opposite to each other.

[0027] In some embodiments, at least one of the first reflective component and the second reflective component comprises a molybdenum / silicon multilayer film.

[0028] In some embodiments, the free-electron laser further includes:

[0029] A driving assembly mechanically connected to at least one of the first reflective element and the second reflective element, and the driving assembly being configured to switch the at least one of the first reflective element and the second reflective element between a first position forming the resonant cavity and a second position not forming the resonant cavity.

[0030] In some embodiments, the number of oscillators in the first oscillator group is less than the number of oscillators in the second oscillator group.

[0031] In some embodiments, the polarization direction of the undulators in the first undulator group is perpendicular to the polarization direction of the undulators in the second undulator group.

[0032] In some embodiments, the intensity of the modulated light radiation formed by the first undulator group is less than the intensity of the target light radiation formed by the second undulator group; and

[0033] The intensity of the modulated light radiation in the resonant cavity is less than the saturation intensity of the resonant cavity.

[0034] In some embodiments, the spacing between two adjacent undulators in the second undulator group is set based on undulator gradient.

[0035] In some embodiments, the wavelength of the target light radiation is 6.5–13.5 nm.

[0036] In some embodiments, the free-electron laser further includes:

[0037] A third quadrupole magnet is located between two adjacent undulators in the first undulator group or between two adjacent undulators in the second undulator group. The center of the third quadrupole magnet is located in the direction of travel of the electron beam, and the third quadrupole magnet is configured to focus the electron beam.

[0038] According to a second aspect of this disclosure, a light source device is provided, comprising:

[0039] An electron injector configured to generate an electron beam and accelerate the electron beam to a first preset energy;

[0040] A linear electron accelerator, located downstream of the electron injector, configured to accelerate an electron beam to a second preset energy, wherein the second preset energy is higher than a first preset energy; and

[0041] The free-electron laser described above is located downstream of the linear electron accelerator.

[0042] According to a third aspect of this disclosure, a lithography system is provided, including a free-electron laser or light source device as described above.

[0043] Other features and advantages of this disclosure will become clearer from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0044] The accompanying drawings, which form part of this specification, illustrate embodiments of this disclosure and, together with the specification, serve to explain the principles of this disclosure.

[0045] This disclosure will become clearer with reference to the accompanying drawings and the following detailed description, wherein:

[0046] Figure 1 A block diagram of a light source device according to an exemplary embodiment of the present disclosure is shown;

[0047] Figure 2 A schematic diagram of the structure of an electron injector in a light source device according to a specific example of the present disclosure is shown;

[0048] Figure 3 A schematic diagram of the structure of a linear electron accelerator in a light source device according to a specific example of the present disclosure is shown;

[0049] Figure 4 A schematic diagram of a folded structure in a linear electron accelerator according to a specific example of the present disclosure is shown;

[0050] Figure 5 A schematic diagram of a free-electron laser according to an exemplary embodiment of the present disclosure is shown;

[0051] Figure 6 A schematic diagram of a free-electron laser according to another exemplary embodiment of the present disclosure is shown;

[0052] Figure 7 A schematic diagram of a quadrupole magnet deflecting an electron beam in a free-electron laser according to a specific example of the present disclosure is shown;

[0053] Figure 8 A schematic diagram is shown of a free-electron laser in which an undulator modulates the energy of an electron beam according to a specific example of the present disclosure;

[0054] Figure 9 A schematic diagram is shown of a free-electron laser in which a group of diode magnets modulates the electron beam density according to a specific example of the present disclosure.

[0055] Note that in the embodiments described below, the same reference numerals are sometimes used across different figures to denote the same parts or parts having the same function, and repeated descriptions are omitted. In this specification, similar reference numerals and letters are used to denote similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0056] For ease of understanding, the positions, dimensions, and extents of the structures shown in the accompanying drawings and other materials may not represent actual positions, dimensions, and extents. Therefore, the disclosed invention is not limited to the positions, dimensions, and extents disclosed in the accompanying drawings and other materials. Furthermore, the drawings are not necessarily drawn to scale, and some features may be enlarged to show details of specific components. Detailed Implementation

[0057] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present disclosure.

[0058] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this disclosure or its application or use. Those skilled in the art will understand that they merely illustrate exemplary ways that can be used to implement this disclosure, and are not exhaustive.

[0059] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0060] To provide sufficiently high-power EUV light sources, the academic community has proposed various schemes distinct from LPP-EUV sources. One highly feasible scheme is the electron accelerator-driven EUV source, and among these, the most promising is currently the free-electron laser (FEL) technology based on a superconducting linear accelerator. Its basic principle is to use a relativistic electron beam with a certain energy generated by the accelerator to interact with a undulator (a periodically arranged array of magnets), thereby producing high-power EUV light with wavelengths satisfying a resonance relationship. Compared to LPP-EUV sources, the main advantages of FEL-EUV sources are higher average power, better beam quality, and the potential to develop new, shorter-wavelength lithography techniques. Theoretically, the average power of FEL-EUV sources can reach the order of 10 kW, while in LPP-EUV sources, due to the power limitations of the gas laser, it is difficult to increase the power of EUV light to above 1 kW.

[0061] Although accelerator-based FEL-EUV light sources are highly promising and are currently one of the hottest research topics in the international accelerator field, no mature EUV light source scheme or overall device design has yet been proposed that simultaneously satisfies the requirements of high-power coherence, continuous wave, acceptable cost, and physical feasibility. The specific reasons are as follows:

[0062] First, to generate EUV light sources with high average power and high conversion efficiency, a high-repetition-rate electron beam must be generated to drive the free-electron laser. However, to achieve a high repetition rate, linear accelerators must employ superconducting technology to handle the power input and thermal load brought about by the high-repetition-rate electron beam, which is currently difficult to achieve.

[0063] Secondly, in linear FEL-EUV light sources, the electron beam utilization rate is very low because it only passes through the undulator once. To obtain high-power EUV light, it is necessary to optimize the electro-optical conversion efficiency from the perspective of FEL operating principles, so that more electron beam power can be converted into EUV light for output. One approach is to use a resonant cavity FEL-EUV light source with higher conversion efficiency. However, this approach brings challenges in controlling the intracavity power and transverse mode, thus presenting design difficulties.

[0064] It is evident that there is still a gap in EUV light sources capable of outputting power in the kW range. Although accelerator-based FEL-EUV light sources have great potential, many problems still need to be solved.

[0065] To this end, this disclosure proposes a free-electron laser and a light source device incorporating the same. In the free-electron laser of this disclosure, by arranging a portion of the undulators such that their outgoing optical path is located on the resonant optical path of the resonant cavity, the electron beam is modulated by the optical radiation generated by this portion of the undulators, and another portion of the undulators (whose outgoing optical path is located outside the resonant optical path of the resonant cavity) interacts with the modulated electron beam from the resonant cavity, thereby more efficiently converting the energy of the electron beam into optical radiation, while reducing the power within the cavity and avoiding damage to the reflective components (e.g., multilayer mirrors) used to form the cavity by high-intensity radiation, so as to achieve a stable, high-power, cost-effective EUV light source with an average power of 1 to 10 kW and an output wavelength of 6.5 to 13.5 nm.

[0066] In one exemplary embodiment of this disclosure, such as Figure 1 As shown, the light source device may include an electron injector 100, a linear electron accelerator 200, and a free electron laser (undulator line) 300 arranged in sequence. Furthermore, in some embodiments, the light source device may also include common components such as beam diagnostic components, control components, laser components, synchronization components, mechanical collimation components, and data acquisition and processing components, as well as supporting facilities such as cryogenic facilities and public utilities, which are not limited herein.

[0067] The electron injector 100 is a crucial component of the light source device. As the source of the entire light source device, the electron injector 100 plays a vital role in determining the performance of the entire device. The electron injector 100 can be configured to generate an electron beam and accelerate it to a first preset energy so as to inject the electron beam into the downstream linear electron accelerator 200. In some embodiments, a photocathode injector / electron gun can be used to generate a high-brightness electron beam cluster and accelerate it to approximately 100 MeV.

[0068] In a specific example, such as Figure 2As shown, the electron injector 100 may include a very high frequency (VHF) electron source 110 (which may include a photocathode), solenoids 121-123, a bundler 130, a booster 140, a superconducting module 150, and a laser heater 160.

[0069] The photocathode can be located within the VHF electron source 110. A driving laser assembly can direct laser light onto the photocathode, thereby emitting an electron beam. The driving laser assembly can provide picosecond-level laser light, and correspondingly, the length of the electron beam cluster is also on the picosecond scale. A laser stacking method can be used to generate the driving laser for the VHF electron source 110, wherein the lateral cutoff Gaussian radius of the driving laser can be 0.62 mm, and the longitudinal distribution is a 10-20 ps flat-top (2 ps rise and fall edges). In some embodiments, the photocathode can be a replaceable cathode. This allows the cathode to be replaced online via a cathode rod after its quantum efficiency decreases. The VHF electron source 110 can generate an electron beam with a charge of 200 pC, a beam energy of 750 keV, and an acceleration gradient of 25 MV / m. In some embodiments, two electron sources 110 can be used, arranged in a V-shaped beamline structure, allowing one electron source 110 to operate while the other serves as a backup. By employing a replaceable cathode and two electron sources, the availability of the electron injector 100 can be greatly improved, ensuring the long-term stable generation of electron beams and thus lasers.

[0070] In some embodiments, the electron injector 100 may also include an electric field for accelerating the electron beam and a magnetic structure for changing the trajectory and shape of the electron beam. For example, the electron beam can be optimized to a low emissivity by adjusting the magnetic structure or the electromagnet current therein.

[0071] like Figure 2As shown, after the electron beam leaves the VHF electron source 110, the space charge force of the electron beam can be compensated for for the first time using solenoid 121. Then, the electron beam can enter a 1.3 GHz dual-cavity room-temperature focuser 130, which provides the electron beam with a low-energy head and high-energy tail chirp, enabling velocity compression during the subsequent drift. Since the energy of the electron beam exiting the focuser 130 is still relatively low, the space charge effect cannot be ignored. Therefore, another solenoid 122 can be placed immediately after the focuser 130 to compensate for the space charge effect. At this point, the energy of the electron beam is still low. To quickly increase the energy and suppress emission growth, a thruster 140 (e.g., a single 9-cell superconducting cavity) can be used to accelerate the electron beam, which then enters a third solenoid 123. The beam propagates further downstream. During drift, the emittance decreases further while the bundle length is compressed until it enters the superconducting module (CM0) 150. There, the electron beam energy increases, and the second cavity of the module is unloaded, allowing for further reduction in emittance and compression of the bundle length. After passing through the third cavity of the module, the electron beam energy increases significantly, and parameters such as bundle length and emittance become fixed, largely unaffected by the space charge effect. Further acceleration occurs, reaching an energy of 100 MeV at the exit of the electron injector 100, with a peak current of 25 A, a bundle length (RMS) of approximately 3 ps, and a normalized slice emittance less than or equal to 1 mm·mrad. Using the acceleration structure described above, the electron beam energy can be achieved at a reasonable level, ensuring it has sufficient energy (e.g., 100 MeV) before entering the linear electron accelerator 200 and suppressing the space charge effect.

[0072] Due to collective effects during electron beam acceleration (e.g., longitudinal space charge (LSC) and coherent synchrotron radiation (CSR)), the initial density modulation introduced by noise fluctuations and laser power fluctuations accumulates and generates energy modulation during acceleration and drift. This energy modulation and density modulation undergo multiple interconversions and amplifications, ultimately degrading the quality of the electron beam. The instability of the micro-bundle is directly related to the slice energy dispersion of the electron beam; the smaller the slice energy dispersion, the more pronounced the micro-bundle instability effect.

[0073] To suppress the instability effect of microclusters, methods such as... Figure 2The laser heater 160 shown increases the slicing energy dispersion of the electron beam. This laser heater 160 allows the electron beam to interact with the laser, thereby erasing microstructures within the electron beam and making the beam locally more uniform. In some embodiments, the laser heater 160 may include four diode magnets, a undulator, and a laser assembly. The laser heater 160 may have a symmetrical structure, with the undulator positioned between the second and third diode magnets. When the laser heater 160 operates, the electron beam passes sequentially through the first, second, and third diode magnets, the undulator, and the fourth diode magnet. The laser assembly of the laser heater 160 transmits infrared laser light that meets certain conditions. This infrared laser light passes through the second diode magnet and enters the undulator along with the electron beam. In the undulator, the injected laser interacts with the electron beam, generating a certain degree of uncorrelated energy dispersion, thereby suppressing the instability of the micro-bulb clusters. In addition, it should be noted that an increase in the slice energy dispersion will lead to a decrease in the radiation power of the electron beam in the undulator. Therefore, it is necessary to optimize the slice energy dispersion of the electron beam to achieve a reasonable balance between the instability of the micro-beam cluster and the radiation power of the undulator.

[0074] The entire electron injector 100 can generate multiple electron beam clusters per second and tune the electron beam energy, trajectory, and size to the parameters desired by the linear electron accelerator 200.

[0075] In a specific example, based on the VHF electron source 110, the electron injector 100 can achieve the following beam parameters:

[0076] Table 1. Electron beam parameters of the electron injector

[0077] parameter Design value unit energy 80-100 MeV charge 50-300 pC Bundle length (RMS) 1-3 ps Peak current 10-25 A Normalized slice emissivity <1 mm·mrad

[0078] like Figure 1As shown, in the light source device, the linear electron accelerator 200 (main accelerator) can be located downstream of the electron injector 100, and the linear electron accelerator 200 can be configured to accelerate the electron beam to a second preset energy higher than a first preset energy, for example, accelerating an electron beam with a repetition frequency on the order of MHz to a high relativistic energy. In some embodiments, the main accelerator based on a superconducting continuous wave operating mode can be used to increase the energy of the electron beam cluster to approximately 1000 MeV, increase the peak current of the electron beam from 25 A to greater than 500 A, and in this process, the main accelerator must also ensure that the beam current parameters such as the emittance of the electron beam do not deteriorate significantly, the current distribution is close to a flat-top distribution, and ensure the stability of parameters such as the trajectory, energy, current intensity, and arrival time of the electron beam, so as to meet the requirements for the electron beam to generate radiation in the downstream free electron laser 300. In some embodiments, the main accelerator can adopt a two-stage acceleration and single-stage compression layout, thereby enabling the length of the electron beam to be compressed from a few picoseconds to tens of femtoseconds while maintaining the transverse emittance, and increasing the peak current intensity of the electron beam to more than 500 A. Compared to room-temperature acceleration technology, superconducting linear accelerator technology can effectively increase the repetition rate of the electron beam without reducing the charge of a single cluster, achieving 10-1 times per second. 4 ~10 9 The pulse (at room temperature acceleration technology is approximately 10 pulses per second) 2 The pulsed electron beam significantly increases the average power of the electron beam, which in turn helps to increase the average power of the generated laser to meet the output power requirements of the EUV light source.

[0079] In a specific example, such as Figure 3 As shown, the linear electron accelerator 200 may include eight 1.3 GHz standard superconducting modules 211–218 (CM1–CM8), two 3.9 GHz superconducting modules 220 (CMH), a magnetic compressor (BC) 230, and a dechirper 240. Furthermore, in some embodiments, the linear electron accelerator 200 may also include associated focusing magnets and beam measurement components.

[0080] The electron beam at the exit of the electron injector 100 has an energy of approximately 100 MeV, a current intensity of approximately 25 A, and a beam length of approximately 1 mm. The first acceleration section L1 of the linear electron accelerator 200 (including standard superconducting modules 211, 212, and superconducting module 220) can accelerate the electron beam to approximately 300 MeV. The acceleration phase is selected before the peak phase, and the electron beam continuously accumulates energy dissipation during acceleration, forming an energy distribution with low head and high tail energy, suitable for electron beam compression. The third harmonic cavity (3.9 GHz) in the first acceleration section L1 can be used to linearize the energy chirp of the electron beam, allowing the electron beam to be compressed to a higher current intensity. The second acceleration section L2 of the linear electron accelerator 200 (including six standard superconducting modules 213–218) can accelerate the electron beam energy from 265 MeV to 1000 MeV. The phase of the second acceleration section L2 is selected at the peak to achieve maximum acceleration efficiency.

[0081] Furthermore, the compression assembly of the linear electron accelerator 200 consists of a single-stage magnetic compressor 230. After magnetic compression, the electron beam current is compressed from 25 A to 500 A, a compression factor of approximately 20. Additionally, significant correlated energy dispersion exists at the exit of the linear electron accelerator 200. This is because the beam must undergo a certain amount of chirp during magnetic compression, resulting in a large residual correlated energy dispersion, which is detrimental to subsequent radiative emission. Therefore, it is necessary to eliminate this dispersion. Unlike room-temperature accelerator structures, superconducting accelerator structures have a large beam aperture and a very weak tail field effect. Therefore, using the tail field to compensate for electron beam energy dispersion is ineffective. Simultaneously, due to the low acceleration gradient and relatively long wavelength of superconducting accelerator structures, using the RF phase of the accelerator structure to compensate for electron beam energy dispersion is not only extremely inefficient but also significantly wastes the effective acceleration gradient. To address these issues, the tail field generated by the pleated structure serving as the energy dispersion elimination section 240 can be used to compensate for electron beam energy dispersion. In a specific example, such as... Figure 4 As shown, a double-plate pleated structure 240 proposed by the Linear Accelerator Coherent Light Source (LCLS) can be used, where the distance between the two plates is 2a, and the beam passes through the pleated structure 240 along the XZ plane. In order to meet the requirements for eliminating energy dissipation in the main accelerator, the size of the gap in the pleated structure can be changed in practice, etc., which is not limited here.

[0082] In general, within the main accelerator, the electron beam is not only accelerated but also compressed. The electron beam generates energy chirps through the preceding accelerator structures, which are then linearized by a harmonic cavity. The chirped electron beam is compressed by a magnetic compression structure. The electron beam is compressed from the picosecond level to the 100 femtosecond level. The harmonic cavity is placed before the magnetic compression structure. In some embodiments, the harmonic cavity can be a non-superconducting structure to reduce cost. The magnetic compression structure is placed near the accelerator module with electron energies below 300 MeV. At the end of the main accelerator, residual energy chirps can be eliminated using an energy dissipation elimination section. In some embodiments, the energy dissipation elimination section can be a symmetrical petal-shaped pleated structure or two sets of orthogonally arranged planar pleated structures. The electron beam energy at the exit of the linear electron accelerator 200 will reach 1000 MeV, with a normalized emittance better than 1 mm·mrad and a relative energy dissipation better than 0.01%.

[0083] In a specific example, the linear electron accelerator 200 can achieve the following exit beam parameters:

[0084] Table 2. Exit beam parameters of the linear electron accelerator

[0085] parameter Design Specifications unit Beam energy ＞1000 MeV Slices can disperse ≤0.01 ％ Emittance ≤1 mm·mrad charge 50-200 pC Peak current ＞500 A repetition frequency 1-10M MHz

[0086] Furthermore, such as Figure 1 As shown, the free-electron laser 300 (undulator line) can be located downstream of the linear electron accelerator 200. It receives the high-energy electron beam from the linear electron accelerator 200 and, under the action of the undulator in the free-electron laser 300, converts the energy of the electron beam into target light radiation for output. This target light radiation can be further used in photolithography processes, etc. In the undulator line disclosed herein, mature and reliable outdoor planar undulator technology can be used to output high-power extreme ultraviolet (EUV) free-electron laser pulses. Based on the requirements of photolithography for the light source and current undulator technology, the FEL-EUV light source can be a magnetically tunable planar undulator. The FEL-EUV light source can cover the radiation range of 6.5-13.5 nm. In the undulator, the resonance relationship of the free-electron laser can be expressed as follows:

[0087]

[0088] Where, λ s λ is the resonant wavelength of the undulator. u Let be the period length of the undulator (in cm), n be the harmonic number, γ be the relativistic factor, and K be a magnetic field deflection parameter related to the magnetic field strength that must satisfy the resonance relationship, where K = 0.934B0λ. uB0 represents the peak magnetic field strength (in tons). Therefore, the wavelength of the target light radiation generated by the free-electron laser 300 is related to parameters such as the period length of the undulator. For example, to generate a target light radiation wavelength of 13.5 nm from the FEL-EUV light source, according to the above formula, a vacuum outdoor planar undulator with a period length of 26 mm and a single unit length of 4 m can be used to interact with the electron beam to generate the target light radiation. It is understood that the wavelength of the generated target light radiation can be changed by altering parameters such as the period length of the undulator; this is not a limitation here.

[0089] In exemplary embodiments of this disclosure, the free-electron laser 300 can operate in a mode based simultaneously on the principles of self-amplified spontaneous emission (SASE) and resonant cavity modes (including, for example, regenerative amplified free-electron laser (RAFEL) mode) to output desired target light radiation (e.g., outputting a high-performance EUV pulse with a single-pulse energy of 200 μJ and a repetition rate of 5 MHz). Specifically, as Figure 5 and Figure 6 As shown, the free-electron laser 300 of this disclosure may include a resonant cavity FEL assembly as a first stage and an FEL radiation amplification assembly as a second stage. The resonant cavity FEL assembly may include a resonant cavity and a first undulator group 320 arranged such that its outgoing optical path is located on the resonant optical path of the resonant cavity. The FEL radiation amplification assembly may include a second undulator group 330. The second undulator group 330 may be arranged such that its outgoing optical path is located outside the resonant optical path of the resonant cavity. In some embodiments, the second undulator group 330 may be disposed on the side opposite to another reflecting component of one reflecting component used to form the resonant cavity, such as... Figure 5 As shown, or in other embodiments, the second undulator group 330 may also be disposed between the two reflecting components used to form the resonant cavity, such as... Figure 6 As shown. By placing the second undulator group 330 between the two reflective components, the entire free electron laser 300 can avoid occupying too much space, making it more suitable for accelerators with low repetition rates (e.g., electron beam repetition rate less than 5 MHz).

[0090] The resonant cavity can be configured to trap modulated light radiation within it. In some embodiments, the resonant cavity can be formed by a first reflective element 311 and a second reflective element 312 disposed opposite to each other. The modulated light radiation in the resonant cavity can be continuously reflected by the first reflective element 311 and the second reflective element 312, thereby traveling back and forth within the resonant cavity and interacting with the electron beam within the resonant cavity, thereby achieving modulation of the electron beam. In some embodiments, especially when the modulated light radiation is in the ultraviolet band, in order to improve the reflectivity, the first reflective element 311 and the second reflective element 312 can use a molybdenum (Mo) / silicon (Si) multilayer film, which can achieve a reflectivity of over 69% near 13.5 nm, and correspondingly, the efficiency after two reflections in the resonant cavity is approximately 47%. However, it is understood that in other embodiments, other materials can be selected to form the first reflective element 311 and the second reflective element 312 according to the band in which the modulated light radiation is located, and this is not limited thereto.

[0091] like Figure 5 and Figure 6 As shown, the first undulator group 320 can be arranged such that its outgoing optical path is located on the resonant optical path of the resonant cavity, and the first undulator group 320 can be configured to interact with the electron beam to generate modulated optical radiation. The modulated optical radiation can be configured to modulate the electron beam. Since only the power of the optical radiation within the resonant cavity is used to modulate the energy of the electron beam, the power of the modulated optical radiation within the resonant cavity can be maintained at a low level; that is, the intensity of the modulated optical radiation within the resonant cavity can be less than the saturation intensity of the resonant cavity, and can even be much lower than the saturation intensity. Figure 8 As shown, the principle of energy modulation of the electron beam within the resonant cavity is as follows: the electron beam exchanges energy with the radiation field of the modulated optical radiation in the first undulator group 320. Due to the different phases of the interaction between the electrons and the radiation field, some electrons lose energy while others gain energy, ultimately forming an energy-time distribution of the electron beam similar to a sine or cosine curve, thus generating an energy-modulated electron beam. This modulation of the electron beam has the following three advantages: First, the power of the optical radiation within the resonant cavity is relatively low, which can greatly reduce the heat load on the first reflecting component 311 and the second reflecting component 312, reducing the cooling requirements; second, it is not necessary to extract the power of the optical radiation within the resonant cavity, thus eliminating the need for a coupling output component; third, it reduces the requirement for the gain factor of the resonant cavity, thereby reducing the requirements for the number and length of the undulators.

[0092] In a specific example, the first undulator group 320 within the resonant cavity may include two undulators. The gain of a single free-electron laser within the resonant cavity can easily reach 3 times, thus compensating for the loss of modulated light radiation caused by reflections at the first reflecting component 311 and the second reflecting component 312, and maintaining the power of the modulated light radiation within the resonant cavity. Here, the length of the unit containing each undulator can be 5m, where the length of each U26 undulator can be 4m, and the distance between two adjacent undulators can be 1m. Between two adjacent undulators, components such as a quadrupole magnet (e.g., a third quadrupole magnet as described later), a correction magnet, a phase shifter, and a beam position detector (BPM) can be arranged.

[0093] like Figure 5 and Figure 6 As shown, the second undulator group 330 can be located downstream of the first undulator group 320, and the second undulator group 330 can be configured to interact with the modulated electron beam to generate target light radiation. Specifically, the undulators enable the electron beam to be periodically deflected, allowing the electron beam to interact with the radiated light as it propagates coaxially, thereby generating and amplifying the radiated light. In some embodiments, the target light radiation can be EUV light used in processes such as photolithography. Because the electron beam has been modulated to the desired state, the second undulator group 330 can convert the energy of the electron beam into the energy of the target light radiation with higher efficiency, thereby generating target light radiation with the desired power. Figure 5 In a specific embodiment, the second undulator group 330 can be arranged on the side of one reflective component used to form the resonant cavity, opposite to the other reflective component, thereby preventing the generated target light radiation from damaging the reflective component used to form the resonant cavity. Figure 6In a specific embodiment, the second undulator group 330 can be arranged such that its outgoing optical path is outside the resonant optical path of the resonant cavity, but it can be located between the two reflective components of the resonant cavity. Since the radiation direction of the target light radiation generated by the second undulator group 330 has a certain deflection, it will not directly irradiate the reflective components used to form the resonant cavity, thus preventing damage to the reflective components. In some embodiments, the spacing between two adjacent undulators in the second undulator group 330 can be set based on undulator tapering technology. Specifically, since the output target light radiation has good coherence, tapering technology can further improve energy conversion efficiency, thereby increasing the output power of the target light radiation. The spacing between each undulator in the second undulator group 330 can gradually increase along the propagation direction of the electron beam. Thus, as the electron beam continuously loses energy, the magnetic spacing of the undulators increases, thereby correspondingly reducing the magnetic field strength of the undulators, maintaining the undulator resonance relationship, and thus continuously amplifying the emitted light. Employing Taper technology has the potential to improve the conversion efficiency of free-electron lasers, further increasing pulse energy and raising the average power of target light radiation to the order of nearly 10 kW. Furthermore, compared to the basic SASE mode, the FEL radiation generated by the free-electron laser disclosed herein exhibits better coherence, with the improvement brought by the Taper undulator being more significant. In addition, in some embodiments, to better eliminate interference from the radiation field within the resonant cavity to the downstream radiation field, the polarization direction of the undulators in the first undulator group 320 can be perpendicular to the polarization direction of the undulators in the second undulator group 330. For example, if the undulators in the second undulator group 330 are horizontally polarized, then the undulators in the first undulator group 320 are vertically polarized. However, it is understood that in some embodiments, the polarization direction of the undulators in the first undulator group 320 may not be perpendicular to the polarization direction of the undulators in the second undulator group 330; however, in this case, the resulting target light radiation may be relatively complex.

[0094] In some embodiments, the number of undulators in the first undulator group 320 may be less than the number of undulators in the second undulator group 330. For example, the number of undulators in the first undulator group 320 may be 1 to 2, while the number of undulators in the second undulator group 330 may be more than 2. Accordingly, the intensity of the modulated light radiation formed by the first undulator group 320 may be less than the intensity of the target light radiation formed by the second undulator group 330. On the one hand, the intensity of the modulated light radiation within the resonant cavity is maintained at a low level, ensuring the modulation effect of the electron beam while avoiding saturation or even damage to the resonant cavity, thus reducing cooling requirements; on the other hand, target light radiation with sufficient intensity can be generated based on the modulated electron beam to meet practical application requirements.

[0095] In some embodiments, such as Figure 5 and Figure 6 As shown, the free-electron laser may further include a first electron beam guiding component, which may be located upstream of the first undulator group 320 and may be configured to guide an electron beam to the first undulator group 320 to interact with the first undulator group 320.

[0096] The first electron beam guiding component can have various configuration options as needed. In a specific example, such as... Figure 5 and Figure 6 As shown, the first electron beam guiding assembly may include a first diode magnet group, which may include one or more first diode magnets 341, and the first diode magnet group may be configured to guide the electron beam from outside the resonant optical path of the resonant cavity to the resonant optical path, for example, from the outside of the resonant cavity to the inside of the resonant cavity. Figure 5 and Figure 6In the specific example shown, the first diode magnet group can be formed by four first diode magnets 341 arranged in a trapezoidal shape. The first first diode magnet 341 can be located to the left of the first reflective component 311, the second first diode magnet 341 can be located downstream of the first first diode magnet 341 and located to the upper left of the first reflective component 311, the third first diode magnet 341 can be located downstream of the second first diode magnet 341 and located to the upper right of the first reflective component 311, and the fourth first diode magnet 341 can be located downstream of the third first diode magnet 341 and located to the right of the first reflective component 311. In this way, each first diode magnet 341 can deflect the direction of travel of the electron beam, thereby guiding the electron beam from outside the resonant optical path of the resonant cavity to the resonant optical path, so that the electron beam can interact with the first undulator group 320 to achieve energy modulation of the electron beam. However, it is understandable that, depending on the position of the electron beam's direction of travel relative to the resonant cavity, one or more diode magnets or other types of magnets can be arranged in other ways to guide the electron beam onto the resonant optical path, without limitation.

[0097] In some embodiments, such as Figure 5 and Figure 6 As shown, the first electron beam guiding assembly may further include a first quadrupole magnet 342, which may be located between the first dipole magnet group and the first undulator group 320. The center of the first quadrupole magnet 342 may be located in the direction of electron beam travel, and the first quadrupole magnet 342 may be configured to focus the electron beam in order to better generate modulated light radiation.

[0098] In some embodiments, such as Figure 5 and Figure 6 As shown, the free-electron laser may further include a second electron beam guiding component, which may be disposed between the first undulator group 320 and the second undulator group 330, and the second electron beam guiding component may be configured to guide the electron beam to the second undulator group 330 and modulate the spatial structure of the electron beam into the target structure.

[0099] In some embodiments, the target structure of the electron beam can be a periodic structure with alternating dense and sparse areas, wherein the period of the target structure can be comparable to or equal to the wavelength of the target light radiation, thereby enabling the second undulator group 330 to better convert the energy of the electron beam into target light radiation to obtain target light radiation with sufficient power. For example, when it is desired to generate target light radiation with a wavelength of 13.5 nm, the spacing between the two adjacent densest parts of the electron beam can be 13.5 nm, or in other words, the spacing between corresponding positions of the two adjacent sparsest parts of the electron beam can be 13.5 nm.

[0100] Similarly, the second electronic guidance component can have various configuration options. In a specific example, such as Figure 5 As shown, the second electron beam guiding assembly may include a second diode magnet group, which may include one or more second diode magnets 351, and this second diode magnet group can be configured to guide the electron beam from the resonant optical path of the resonant cavity to outside the resonant optical path, and modulate the spatial structure of the electron beam into the target structure. Here, the first undulator group 320 and the second undulator group 330 can be arranged along the same extending direction. Figure 5 In the specific example shown, the second diode magnet group can be formed by four second diode magnets 351 arranged in a trapezoidal shape. The first second diode magnet 351 can be located to the left of the second reflector 312, the second second diode magnet 351 can be located downstream of the first second diode magnet 351 and located to the upper left of the second reflector 312, the third second diode magnet 351 can be located downstream of the second second diode magnet 351 and located to the upper right of the second reflector 312, and the fourth second diode magnet 351 can be located downstream of the third second diode magnet 351 and located to the right of the second reflector 312. In this way, each second diode magnet 351 can deflect the direction of travel of the electron beam, thereby guiding the electron beam from the resonant optical path of the resonant cavity to outside the resonant optical path, so that the electron beam can continue to interact with the second undulator group 330 to generate target light radiation. However, it is understandable that, depending on the position of the electron beam relative to the resonant cavity, one or more diode magnets or other types of magnets may be arranged in other ways to guide the electron beam to the second undulator group 330, without limitation.

[0101] Furthermore, the second diode magnet assembly can modulate the spatial structure of the electron beam to the target structure; this second diode magnet assembly can also be called the dispersion section. Specifically, after passing through the resonant cavity, the electron beam already possesses energy modulation. Further, the dispersion section can be used to convert the energy modulation of the electron beam into density modulation. For example... Figure 9 As shown, the basic principle of the dispersion section is: since the electron beam is modulated by the modulation light radiation in the resonant cavity, it has energy-time chirp, so the paths of electrons with different energies in the dispersion section will be different; when the electron beam passes through the dispersion section, the high-energy electrons will chase the low-energy electrons, thereby realizing the aggregation of electrons with different energies at the same position, and thus realizing the conversion of energy modulation to density modulation. Finally, micro-clusters can be generated at the target wavelength, forming an electron beam with micro-clusters. This electron beam then enters the second undulator group 330 to generate target light radiation.

[0102] In another specific embodiment, such as Figure 6As shown, the second electron beam guiding assembly may include a second quadrupole magnet 352 and a third dipole magnet group, the third dipole magnet group may include one or more third dipole magnets 353.

[0103] like Figure 6 and Figure 7 As shown, the center of the second quadrupole magnet 352 can be offset in a lateral direction perpendicular to the direction of electron beam travel, so that the direction of electron beam travel is deflected toward the second undulator group 330. In this case, the first undulator group 320 and the second undulator group 330 can be arranged along different extension directions. When the electron beam passes through the second quadrupole magnet 352, the deflection of the electron beam can be described by the following transfer matrix:

[0104]

[0105] Where x represents the lateral position of the electron beam, x' represents the travel angle of the electron beam, subscript 0 indicates the initial state, subscript 1 indicates the state after passing through the second quadrupole magnet 352, and f is the focusing length of the second quadrupole magnet 352. Therefore, after passing through the second quadrupole magnet 35, the travel angle of the electron beam is... This explains that when the electron beam does not pass through the center of the quadrupole magnet, an angular deflection occurs. Therefore, the desired deflection angle can be obtained by moving the quadrupole magnet, directing the electron beam toward the second undulator group 330. In some embodiments, the second quadrupole magnet 352 can be configured to deflect the electron beam's direction of travel by 30–100 μrad or 100–300 μrad. In this way, the spacing between the first undulator group 320 and the second undulator group 330 in the lateral direction perpendicular to the electron beam's direction of travel can be controlled within a certain range, preventing the entire free-electron laser 300 from occupying excessive space.

[0106] Furthermore, the third diode magnet group can be located between the second quadrupole magnet 352 and the second undulator group 330, and the third diode magnet group can be configured to modulate the spatial structure of the electron beam to the target structure, that is, the third diode magnet group can be used as a dispersive segment, as mentioned above. Figure 9 As detailed above.

[0107] In some embodiments, to enable the free-electron laser 300 to operate in multiple modes, it may further include a driving assembly mechanically connected to at least one of the first reflecting member 311 and the second reflecting member 312, and configured to switch the at least one of the first reflecting member 311 and the second reflecting member 312 between a first position forming a resonant cavity and a second position not forming a resonant cavity. Thus, by removing the reflector and turning off the corresponding diode magnet to close the resonant cavity, the electron beam can enter the second undulator group 330 directly without passing through the resonant cavity, allowing the free-electron laser 300 to operate in self-amplified spontaneous emission (SASE) mode.

[0108] In some embodiments, the free-electron laser may further include a third quadrupole magnet, which may be located between two adjacent undulators in a first undulator group or between two adjacent undulators in a second undulator group. The center of the third quadrupole magnet may be located in the direction of travel of the electron beam, and the third quadrupole magnet is configured to focus the electron beam to improve the quality of the electron beam.

[0109] In a specific example, the free-electron laser 300 can achieve the following output:

[0110] Table 3. Parameters of FEL-EUV light source

[0111] parameter Design Specifications unit oscillator period length 26 mm undulator magnetic field strength >1 T Total length of undulator 5m×10 m FEL wavelength 13.5 nm FEL peak power ～1 GW FEL pulse width >200 fs FEL average power >1 kW

[0112] Furthermore, this disclosure also proposes a lithography system that may include a free-electron laser or light source device as described above. Using the target light radiation generated by the aforementioned free-electron laser or light source device, especially EUV light radiation with wavelengths in the range of 6.5–13.5 nm, photolithography and other processes on the product can be performed, thereby achieving the desired chip or integrated circuit manufacturing.

[0113] In the technical solution of this disclosure, modulated light radiation is generated by the interaction of a first undulator group with an electron beam. This modulated light radiation modulates the electron beam, which then interacts with a second undulator group to generate target light radiation. Since the modulated light radiation is only used to modulate the energy of the electron beam, the power within the resonant cavity can be kept at a low level, thereby significantly reducing the heat load on the reflective components forming the resonant cavity and thus lowering the cooling requirements. Specifically, in conventional resonant cavity FELs, the output efficiency is between 10% and 90%. To achieve an output of 1kW or more, the power within the cavity must be at least 100W. However, in this disclosure, the power within the resonant cavity can be less than 10W. Furthermore, in the resonant cavity of this disclosure, there is no need to consider extracting the radiated light power from the cavity, thus eliminating the need for a coupling output component. In addition, since the gain requirement for the undulators within the resonant cavity is reduced, the requirements for the number and length of the undulators can be reduced. Furthermore, both theoretical and experimental studies have demonstrated that, compared to the basic SASE mode, the FEL radiation generated by the free-electron laser disclosed in this invention exhibits better coherence. Combined with undulator gradient technology, this results in a more significant power increase, further enhancing energy conversion efficiency and FEL output power. For example, in SASE mode, there is only a 2-fold power increase, while the disclosed technology achieves a 5-fold power increase. Simultaneously, theory shows that better coherence reduces power jitter, making the output more stable. In the light source device disclosed in this invention, the electron linear accelerator and free-electron laser based on superconducting radio frequency technology can generate fully coherent and stable extreme ultraviolet (EUV) radiation with an average power in the kilowatt range. Additionally, the average pulse energy of the generated EUV pulses can be approximately several hundred microjoules, and the full width at half maximum (FWHM) of the pulse length can be in the range of approximately hundreds of femtoseconds. Operating at an electron beam repetition frequency of 5 MHz, the average power of the generated target light radiation can reach 1 kW, and with undulator gradient technology, it has the potential to be further increased to 10 kW. The extreme ultraviolet light pulses generated by this disclosure are close to the Fourier transform limit, have good energy stability, good coherence, and high single-pulse flux, making them particularly suitable for nanolithography and extreme ultraviolet optical experiments.

[0114] The terms “left,” “right,” “front,” “back,” “top,” “bottom,” “upper,” “lower,” “high,” “lower,” etc., used in the specification and claims, if present, are for descriptive purposes and not necessarily for describing unchanging relative positions. It should be understood that such terms are interchangeable where appropriate, enabling embodiments of this disclosure described herein to operate, for example, in orientations different from those shown or otherwise described herein. For example, when the device in the drawings is reversed, a feature previously described as “above” other features may now be described as “below” other features. The device may also be oriented in other ways (rotated 90 degrees or in other orientations), in which case the relative spatial relationships will be interpreted accordingly.

[0115] In the specification and claims, when an element is described as being "on top of," "attached to," "connected to," "coupled to," or "in contact with" another element, the element may be directly located on top of, directly attached to, directly connected to, directly coupled to, or directly in contact with the other element, or one or more intermediate elements may be present. Conversely, when an element is described as being "directly" located on top of, directly attached to, directly connected to, directly coupled to, or directly in contact with another element, no intermediate elements are present. In the specification and claims, when a feature is arranged "adjacent" to another feature, it may mean that a feature has a portion overlapping with the adjacent feature or a portion located above or below the adjacent feature.

[0116] As used herein, the term “exemplary” means “serving as an example, instance, or illustration” and not as a “model” to be precisely copied. Any implementation described herein by example is not necessarily to be construed as preferred or advantageous over other implementations. Moreover, this disclosure is not limited to any theory expressed or implied as given in the field of art, background art, summary of invention, or detailed description.

[0117] As used herein, the term "substantially" means any minor variation resulting from design or manufacturing defects, device or component tolerances, environmental influences, and / or other factors. The term "substantially" also allows for differences from the perfect or ideal situation due to parasitic effects, noise, and other practical considerations that may exist in the actual implementation.

[0118] Furthermore, terms such as “first,” “second,” etc., may be used in this document for reference purposes only and are not intended to be limiting. For example, unless the context clearly indicates otherwise, the words “first,” “second,” and other such numerical terms relating to structures or elements do not imply order or sequence.

[0119] It should also be understood that when the term “including / contains” is used herein, it indicates the presence of the indicated feature, whole, step, operation, unit and / or component, but does not preclude the presence or addition of one or more other features, wholes, steps, operations, units and / or components and / or combinations thereof.

[0120] In this disclosure, the term “provide” is used broadly to cover all ways of obtaining an object, and therefore “provide an object” includes, but is not limited to, “purchasing,” “preparing / manufacturing,” “arranging / setting up,” “installing / assembling,” and / or “ordering” an object.

[0121] As used herein, the term “and / or” includes any and all combinations of one or more of the listed items in association. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. As used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise.

[0122] Those skilled in the art will recognize that the boundaries between the above operations are merely illustrative. Multiple operations may be combined into a single operation, a single operation may be distributed among additional operations, and operations may be performed with at least partial overlap in time. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be changed in various other embodiments. However, other modifications, variations, and substitutions are equally possible. Aspects and elements of all the embodiments disclosed above may be combined in any way and / or in combination with aspects or elements of other embodiments to provide multiple additional embodiments. Therefore, this specification and the accompanying drawings should be considered illustrative rather than restrictive.

[0123] While specific embodiments of this disclosure have been described in detail by way of example, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of this disclosure. The various embodiments disclosed herein can be combined in any way without departing from the spirit and scope of this disclosure. Those skilled in the art should also understand that various modifications can be made to the embodiments without departing from the scope and spirit of this disclosure. The scope of this disclosure is defined by the appended claims.

Claims

1. A free-electron laser, characterized in that, The free-electron laser includes: Resonant cavity; A first undulator group is arranged such that its outgoing optical path is located on the resonant optical path of the resonant cavity, and the first undulator group is configured to interact with the electron beam to generate modulated optical radiation, wherein the modulated optical radiation is configured to modulate the electron beam; and The second undulator group is arranged such that its outgoing optical path is outside the resonant optical path of the resonant cavity, the second undulator group is located downstream of the first undulator group, and the second undulator group is configured to interact with the modulated electron beam to generate target light radiation.

2. The free-electron laser according to claim 1, characterized in that, The resonant cavity is configured to capture modulated light radiation but not target light radiation.

3. The free-electron laser according to claim 1 or 2, characterized in that, The free-electron laser also includes: A first electron beam guiding component is located upstream of the first undulator group and is configured to guide an electron beam to the first undulator group to interact with the first undulator group.

4. The free-electron laser according to claim 3, characterized in that, The first electron beam guiding assembly includes: A first diode magnet group, comprising one or more first diode magnets, and configured to guide an electron beam from outside the resonant optical path of the resonant cavity to the resonant optical path; and A first quadrupole magnet is located between the first dipole magnet group and the first undulator group. The center of the first quadrupole magnet is located in the direction of electron beam travel, and the first quadrupole magnet is configured to focus the electron beam.

5. The free-electron laser according to claim 1 or 2, characterized in that, The free-electron laser also includes: A second electron beam guiding component is located between the first undulator group and the second undulator group, and is configured to guide an electron beam to the second undulator group and modulate the spatial structure of the electron beam into a target structure, wherein the target structure of the electron beam is a periodic structure with alternating density and sparseness, and the period of the target structure is equivalent to the wavelength of the target light radiation.

6. The free-electron laser according to claim 5, characterized in that, The second electron beam guiding assembly includes a second diode magnet group, which comprises one or more second diode magnets. The second diode magnet group is configured to guide the electron beam from the resonant optical path of the resonant cavity to outside the resonant optical path and modulate the spatial structure of the electron beam to the target structure. The first undulator group and the second undulator group are arranged along the same extending direction; or The second electron beam guiding assembly includes a second quadrupole magnet and a third diode magnet group. The center of the second quadrupole magnet is offset in a lateral direction perpendicular to the direction of travel of the electron beam, so that the direction of travel of the electron beam is deflected toward the second undulator group. The third diode magnet group includes one or more third diode magnets. The third diode magnet group is located between the second quadrupole magnet and the second undulator group, and the third diode magnet group is configured to modulate the spatial structure of the electron beam into the target structure. The first undulator group and the second undulator group are arranged along different extension directions.

7. The free-electron laser according to claim 1 or 2, characterized in that, The resonant cavity is formed by a first reflective component and a second reflective component arranged opposite to each other, wherein at least one of the first reflective component and the second reflective component comprises a molybdenum / silicon multilayer film; The free-electron laser further includes a driving assembly mechanically connected to at least one of the first reflective component and the second reflective component, and the driving assembly is configured to switch the at least one of the first reflective component and the second reflective component between a first position forming the resonant cavity and a second position not forming the resonant cavity.

8. The free-electron laser according to claim 1 or 2, characterized in that, The number of oscillators in the first oscillator group is less than the number of oscillators in the second oscillator group; and / or The polarization directions of the undulators in the first undulator group are perpendicular to the polarization directions of the undulators in the second undulator group; and / or The intensity of the modulated light radiation formed by the first undulator group is less than the intensity of the target light radiation formed by the second undulator group, and the intensity of the modulated light radiation in the resonant cavity is less than the saturation intensity of the resonant cavity. and / or The spacing between two adjacent undulators in the second undulator group is set based on the undulator gradient. and / or The wavelength of the target light radiation is 6.5–13.5 nm; and / or The free-electron laser further includes a third quadrupole magnet located between two adjacent undulators in the first undulator group or between two adjacent undulators in the second undulator group, the center of the third quadrupole magnet being located in the direction of electron beam travel, and the third quadrupole magnet being configured to focus the electron beam.

9. A light source device, characterized in that, The light source device includes: An electron injector configured to generate an electron beam and accelerate the electron beam to a first preset energy; A linear electron accelerator, located downstream of the electron injector, configured to accelerate an electron beam to a second preset energy, wherein the second preset energy is higher than a first preset energy; and The free-electron laser according to any one of claims 1 to 8 is located downstream of the linear electron accelerator.

10. A lithography machine system, characterized in that, The lithography system includes a free-electron laser according to any one of claims 1 to 8 or a light source device according to claim 9.

Images