Radiation leading-out device and method of resonant cavity type extreme ultraviolet free electron laser

Abstract

The invention provides a radiation leading-out device of a resonant cavity type extreme ultraviolet free electron laser, which is characterized by comprising one or more first reflectors distributed on one side of a main shaft of a resonant cavity, and the first reflectors are arranged to receive one part of a radiation beam in the resonant cavity. And at least the radiation beam in the resonant cavity is reflected by the first reflector to obtain a leading-out beam. The invention also provides a corresponding radiation extraction system and method. According to the radiation leading-out device of the resonant cavity type extreme ultraviolet free electron laser, required FEL radiation is directly led out from the interior of the resonant cavity by using the multi-layer film reflecting mirror without hole digging, so that the condition that the center of the resonant cavity mirror of the resonant cavity type FEL device is punched is avoided, and the required FEL radiation is directly led out from the interior of the resonant cavity; the preparation difficulty of the resonant cavity mirror of the FEL and unstable factors of coating are reduced, the radiation output quality of the vibration cavity type EUV FEL is improved, and the amplification gain of the FEL is improved.

Description

Technical Field

[0001] The present invention belongs to the field of free electron lasers, and in particular relates to a radiation extraction device and method for a resonant cavity type extreme ultraviolet free electron laser. Background Art

[0002] For nearly 50 years, the development and growth of the semiconductor industry has been following Moore's Law. It can be said that the continuous reduction of the size of microchip transistors is driven by the development of lithography technology. However, in order to further reduce the feature size to 5 nanometers and below, extreme ultraviolet lithography (EUVL) technology has been proposed. EUVL has been proven to meet the industrial requirements of the next generation of semiconductor manufacturing.

[0003] The development of high-power extreme ultraviolet (EUV) light sources has received considerable attention in the past few years as a long-term key challenge in the implementation of technologies such as EUVL in high-volume manufacturing (HVM). Current industry interest is mainly focused on the wavelength of λ=13.5nm, which has been regarded as a cutting-edge technology for manufacturing new generation semiconductor devices at 5nm and below nodes.

[0004] The CO2 laser produced plasma (LPP) system is currently the mainstream light source solution, but because the LPP light source is prone to contamination and random effects on the EUV collection mirror, the system has obvious limitations on the output light power and cannot achieve technological breakthroughs in EUVL in terms of higher output light power.

[0005] Free electron laser (FEL), as an efficient, clean, high-power EUV light source, is one of the promising ways to solve this problem. This method relies on a mature superconducting accelerator technology to produce relativistic, high-current, high-repetition-rate electron beams that can produce kW-level EUV radiation when passed through an undulator tuned to the desired wavelength. In a free electron laser (FEL), a beam of electrons passes through a transverse periodic magnetic field to amplify the electromagnetic radiation.

[0006] In order to achieve high-power EUV-FEL (extreme ultraviolet free electron laser) output, a resonant cavity FEL (free electron laser) was proposed, such as Figure 1 As shown. Similar to conventional lasers, an amplifier or oscillator can be configured on both sides of the FEL undulator, which uses the interaction between the electron beam and the light stored in the oscillator to amplify the FEL light power. This method can significantly increase the proportion of electron beam energy converted into FEL radiation, and transmit the high-power radiation to the entrance of the FEL via the resonant cavity mirror 200. In order to achieve high reflection efficiency of the resonant cavity mirror, we use a Mo / Si multilayer film mirror suitable for 13.5nm radiation.

[0007] In the above FEL device, EUV radiation and the modulated relativistic electron beam are oscillated and amplified together in the resonant cavity formed by the multilayer film reflectors at both ends of the undulator. On the downstream multilayer film resonant cavity mirror 200, the required 13.5nm wavelength radiation is smaller than the modulation wavelength of the FEL, and the spot size is smaller. Therefore, the FEL pulse generated by the radiation section can be drawn out through the small hole in the center of the downstream resonant cavity, while ensuring that the radiation of other wavelengths is output less in the small hole. In this way, the EUV radiation of the FEL circulates in the resonant cavity while the radiation of the 13.5nm wavelength is continuously output.

[0008] However, technically, it is difficult to make a hole in a complete multilayer film reflector or to coat a substrate with a hole. In addition, due to the preparation process, the multilayer film surface error near the central hole area or the coating defects inside the multilayer film may affect the 13.5nm radiation output quality. At the same time, when a hole is made in the resonant cavity, the radiation at the center of the FEL spot is led out, destroying the spot structure. In this case, the lateral mode of the spot in the optical resonant cavity may be unstable, resulting in insufficient FEL amplification gain. This further leads to unstable output of the entire device or low output power.

[0009] Therefore, it is necessary to propose a new radiation extraction system for a high-power resonant cavity type extreme ultraviolet free electron laser so that the resonant cavity does not need to be dug and the radiation output quality of the resonant cavity type extreme ultraviolet free electron laser is improved. Summary of the invention

[0010] The object of the present invention is to provide a radiation extraction device and method for a resonant cavity type extreme ultraviolet free electron laser, so as to improve the radiation output quality of the resonant cavity type extreme ultraviolet free electron laser.

[0011] In order to achieve the above-mentioned purpose, the present invention provides a radiation extraction device of a resonant cavity type extreme ultraviolet free electron laser, comprising one or more first reflectors distributed on one side of the main axis of the resonant cavity, wherein the first reflectors are configured to receive a portion of the radiation beam in the resonant cavity, and an extraction beam is obtained at least by reflecting the radiation beam in the resonant cavity by the first reflectors.

[0012] There are multiple first reflectors, which are arranged along the main axis of the resonant cavity.

[0013] The directions of the light beams emitted by the plurality of first reflectors are consistent, or inconsistent; and / or

[0014] The direction of the outgoing light beam of each first reflector is a vertical direction, or a horizontal direction perpendicular to the main axis of the resonant cavity.

[0015] The radiation extraction device further comprises a reflector fixing slider slidable on the reflector fixing slide rail, a vertical telescopic device fixed on the reflector fixing slider, and a reflector rotating device arranged at the top of the vertical telescopic device and connected to the back mirror seat of the corresponding first reflector; and / or

[0016] All the first reflectors are mounted on the same reflector fixing slide rail.

[0017] The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser also includes a second reflector distributed on the other side of the main axis of the resonant cavity, and obtains an extracted light beam by twice reflecting the radiation light beam in the resonant cavity by the first reflector and the second reflector; the second reflector is located outside the optical path of the resonant cavity and is configured to receive the outgoing light beam from its corresponding first reflector, thereby playing a role in adjusting the reflection direction.

[0018] The number of the first reflector and the second reflector is multiple, and the first reflector and the second reflector correspond to each other one-to-one; or, the first reflector and the second reflector correspond to each other in a one-to-many or many-to-one manner; and / or the first reflector and the second reflector are both multi-layer film reflectors; and / or the radiation extraction device also includes a reflector fixing slider slidable on the reflector fixing slide rail, a vertical telescopic device fixed on the reflector fixing slide rail, and a reflector rotating device arranged at the top of the vertical telescopic device and connected to the back mirror seat of the corresponding first reflector or second reflector; and / or all the first reflectors are installed on the same reflector fixing slide rail, and all the second reflectors are installed on another reflector fixing slide rail.

[0019] On the other hand, the present invention provides a radiation extraction system for a resonant cavity type extreme ultraviolet free electron laser, comprising a resonant cavity type extreme ultraviolet free electron laser and a radiation extraction device as described above; the radiation extraction device is located in a vacuum region between an undulator and a resonant cavity mirror 200 inside the resonant cavity of the resonant cavity type extreme ultraviolet free electron laser.

[0020] On the other hand, the present invention provides a method for extracting radiation from a resonant cavity type extreme ultraviolet free electron laser, comprising: installing a radiation extraction device for the resonant cavity type extreme ultraviolet free electron laser as described above in the resonant cavity type extreme ultraviolet free electron laser; and moving a first reflector so that when the resonant cavity type extreme ultraviolet free electron laser is in an operating state, one or more first reflectors receive a portion of the radiation beam in the resonant cavity and reflect it to obtain an extracted beam.

[0021] The first reflector receives and reflects a portion of the radiation beam in the resonant cavity, which means that the first reflector receives at most 90% of the radiation beam in the resonant cavity; and / or the direction of the outgoing light beam of the first reflector is vertical or horizontal, perpendicular to the main axis of the resonant cavity; and / or the first reflector faces the undulator or turns away from the undulator, and the angle between the first reflector and the main axis of the resonant cavity is a fixed angle, which matches the designed reflection angle of the multilayer film reflector; and / or when there are multiple first reflectors, the multiple first reflectors are arranged in the resonant cavity according to a horizontal distribution along the main axis direction of the resonant cavity and a stepped height distribution, so as to respectively receive and reflect a portion of the radiation beam in the resonant cavity to obtain an outgoing light beam.

[0022] On the other hand, the present invention provides a radiation extraction method for a resonant cavity type extreme ultraviolet free electron laser, comprising: installing the radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser described above in the resonant cavity type extreme ultraviolet free electron laser; by moving the first reflector and the second reflector, when the resonant cavity type extreme ultraviolet free electron laser is in an operating state, one or more first reflectors receive a part of the radiation beam in the resonant cavity and reflect it to obtain an extracted beam, and the corresponding second reflector reflects the extracted beam from the first reflector.

[0023] The first reflector receives a portion of the radiation beam in the resonant cavity and reflects it, which means that the first reflector receives at most 90% of the radiation beam in the resonant cavity; and / or the direction of the outgoing light beam of the first reflector is vertical or horizontal, perpendicular to the main axis of the resonant cavity, and the direction of the outgoing light beam of the second reflector is parallel to the main axis of the resonant cavity; and / or the first reflector faces the undulator or turns away from the undulator, and the angle between the first reflector and the main axis of the resonant cavity is a fixed angle, which matches the designed reflection angle of the multilayer film reflector; and / or when there are multiple first reflectors for obtaining the outgoing light beam, the multiple first reflectors are arranged along The second reflectors are arranged in the resonant cavity according to the horizontal distribution and the stepped height distribution along the main axis direction of the resonant cavity, so as to respectively receive a part of the radiation beam in the resonant cavity and reflect it to obtain an outgoing beam; and / or when there are multiple second reflectors reflecting the outgoing beam, the multiple second reflectors are arranged according to the horizontal distribution and the stepped height distribution along the main axis direction of the resonant cavity, so as to reflect the outgoing beam from the first reflector; and / or the number of the first reflector and the second reflector are both multiple, and the first reflector and the second reflector correspond to each other one by one; or, the first reflector and the second reflector correspond to each other in a one-to-many or many-to-one manner.

[0024] The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser of the present invention uses a multilayer film reflecting mirror without holes to directly extract the required FEL radiation from the inside of the resonant cavity. This solution avoids drilling a hole in the center of the resonant cavity mirror of the resonant cavity type FEL device, and directly extracts the required FEL radiation from the inside of the resonant cavity, thereby reducing the difficulty of preparing the resonant cavity mirror of the FEL and the unstable factors of the coating, improving the radiation output quality of the resonant cavity type EUV FEL, and improving the FEL amplification gain.

[0025] At the same time, the radiation extraction device of the resonant cavity extreme ultraviolet free electron laser of the present invention uses a movable mirror fixing structure installed on a slide rail, which can realize single-point or multi-point simultaneous extraction of FEL beams from the inside of the resonant cavity FEL device, thereby realizing FEL beam expansion; when realizing multi-path extraction of FEL light, it provides source-end layout convenience for the subsequent FEL to be used as an EUV light source in an EUV lithography factory to implement multi-path parallel or serial optical path solutions, and can provide several kilowatts of EUV power to each of dozens of EUV lithography scanners, achieving breakthroughs in productivity, output and technical nodes.

[0026] The radiation extraction device of the resonant cavity extreme ultraviolet free electron laser proposed in this invention uses a combination of a reflector and a double reflector to realize the extraction of FEL beams in different directions from the inside of the resonant cavity FEL device, thereby realizing the extraction of the FEL beam parallel to or perpendicular to the undulator direction.

[0027] In addition, the radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser proposed in the present invention uses a reflector with a Mo / Si multilayer film as a coating as the main reflection path for extraction, which can achieve the extraction of EUV beams with higher reflection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of an existing resonant cavity FEL device.

[0029] Figure 2 It is a layout diagram of a radiation extraction device of a radiation extraction system of a resonant cavity type extreme ultraviolet free electron laser of the present invention relative to an undulator.

[0030] Figure 3A 4 is a schematic structural diagram of a radiation extraction device of a resonant cavity type extreme ultraviolet free electron laser according to a first embodiment of the present invention.

[0031] Figure 3B 4 is a schematic structural diagram of a radiation extraction device of a resonant cavity type extreme ultraviolet free electron laser according to a second embodiment of the present invention.

[0032] Figure 4A and Figure 4BIt is a schematic diagram of the principle of a radiation extraction method of a resonant cavity type extreme ultraviolet free electron laser according to the third embodiment of the present invention.

[0033] Figure 5 4 is a schematic diagram of the principle of a radiation extraction method for a resonant cavity type extreme ultraviolet free electron laser according to the fourth embodiment of the present invention.

[0034] Fig. 6A and Figure 6B 4 is a schematic diagram of the principle of a radiation extraction method for a resonant cavity type extreme ultraviolet free electron laser according to the fifth embodiment of the present invention.

[0035] Figure 7 4 is a schematic diagram of the principle of a radiation extraction method for a resonant cavity type extreme ultraviolet free electron laser according to a sixth embodiment of the present invention.

[0036] Fig. 8A and Figure 8B 4 is a schematic diagram of the principle of a radiation extraction method for a resonant cavity type extreme ultraviolet free electron laser according to the seventh embodiment of the present invention.

[0037] Fig.9A and Fig. 9B 4 is a schematic diagram of the principle of a radiation extraction method for a resonant cavity type extreme ultraviolet free electron laser according to an eighth embodiment of the present invention.

[0038] Fig. 10A and Fig. 10B 4 is a schematic diagram of the principle of a radiation extraction method for a resonant cavity type extreme ultraviolet free electron laser according to the ninth embodiment of the present invention.

[0039] Fig.11A and Fig. 11B 4 is a schematic diagram of the principle of a radiation extraction method for a resonant cavity type extreme ultraviolet free electron laser according to the tenth embodiment of the present invention.

[0040] Fig. 12A and Fig. 12B It is a schematic diagram of the principle of a radiation extraction method for a resonant cavity type extreme ultraviolet free electron laser according to the eleventh embodiment of the present invention.

[0041] Fig.13A and Fig. 13B 4 is a schematic diagram of the principle of a radiation extraction method for a resonant cavity type extreme ultraviolet free electron laser according to the twelfth embodiment of the present invention.

[0042] Fig.14 It is a schematic diagram of a reflector having a Mo / Si multilayer film structure.

[0043] Fig.15 It is a flow chart of the design method of Mo / Si multilayer film.

[0044] Figure 16A-16C It is a reflectivity curve corresponding to the determined structural parameters of the Mo / Si multilayer film.

[0045] Fig.17 This is the trace of the FEL beam passing through a multilayer film mirror.

[0046] Fig.18 This is the trace of the FEL beam passing through two multilayer film mirrors. DETAILED DESCRIPTION

[0047] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.

[0048] The working principle of the radiation extraction system of a resonant cavity type extreme ultraviolet free electron laser of the present invention is described in detail below.

[0049] Depend on Figure 1 It can be seen that for the existing resonant cavity EUV-FEL (extreme ultraviolet free electron laser), when the electron beam generating the FEL (free electron laser) oscillates back and forth upstream and downstream of the undulator 300, a 13.5nm FEL radiation beam is generated. Based on the existing resonant cavity EUV-FEL (extreme ultraviolet free electron laser), the present invention proposes various types of methods, devices and systems for splitting and extracting EUV beams inside a high-power resonant cavity free electron laser resonant cavity to provide multi-path sub-beams, avoiding the quality risks caused by the drilling of the resonant cavity mirror during the preparation process and the technical difficulties of reduced radiation quality, improving the beam quality of the EUV beam output by the EUV-FEL system, and laying the foundation for future beam line design.

[0050] The working principle of the radiation extraction system of a resonant cavity type extreme ultraviolet free electron laser of the present invention is that: after the electron beam of the FEL resonant cavity is extracted, a series of FEL radiation reflectors can be placed in the vacuum area inside the resonant cavity near the upstream and lower resonant cavity reflectors to extract part of the EUV radiation from the EUV beam being resonated, while at the same time not affecting the continued oscillation and amplification of the EUV radiation in the resonant cavity. It should be noted that the FEL radiation reflector here can be a total reflector that does not generate any transmitted light beam. The reflector can usually be a reflector coated with a multilayer film (the substrate of the mirror coated with a multilayer film is made of silicon, metal, etc.), and the coated multilayer film can be specially designed and prepared according to the reflection angle.

[0051] A radiation extraction system of a resonant cavity type extreme ultraviolet free electron laser of the present invention comprises a resonant cavity type extreme ultraviolet free electron laser and one or two sets of radiation extraction devices, wherein the radiation extraction devices are arranged at positions such as Figure 2As shown, the vacuum region between the undulator 300 and the resonant cavity mirror 200 inside the resonant cavity of the resonant cavity type EUV free electron laser is used to guide the radiation beam out from the side of the resonant cavity by causing a part of the radiation beam to undergo total reflection. Figure 2 As shown, since there is EUV radiation between both ends of the undulator 300 and the resonant cavity mirror 200, the radiation extraction system of the present invention may include two sets of radiation extraction devices located at both ends of the undulator 300. Two sets of the same or different radiation extraction devices are used to meet the radiation extraction requirements, and the direction of radiation extraction can be any direction from the cross section of the radiation beam parallel to the two ends of the undulator 300. For each set of radiation extraction devices, the beam extraction site is not limited to one, and a corresponding number of beam extraction sites can be arranged as regularly as possible within a limited range to meet engineering needs. It should be noted that Figure 2 The radiation extraction device is only used to indicate the relative position relationship between the radiation extraction device and the entire FEL device, as well as the beam extraction position of the radiation extraction device, and does not represent the specific structure and specific extraction situation of the radiation extraction device. The specific structure of the radiation extraction device is described in detail by the multiple embodiments below.

[0052] First embodiment: Radiation extraction device of a resonant cavity type extreme ultraviolet free electron laser for obtaining an extracted beam by single reflection

[0053] like Figure 3A The figure shows a radiation extraction device according to a first embodiment of the present invention, the radiation extraction device comprises one or more first reflectors 10 distributed on one side of the main axis of the resonant cavity, and the extracted beam is obtained by a single reflection of the radiation beam in the resonant cavity by the first reflector 10. When the number of the first reflector 10 is single, the EUV beam can be extracted in a single channel; when the number of the first reflector 10 is multiple, the EUV beam can be extracted in a multi-channel manner.

[0054] The plurality of first reflectors 10 are arranged along the main axis direction of the resonant cavity and are configured to receive a portion of the radiation beam (ie, the EUV beam being resonantly amplified) in the resonant cavity, thereby playing a reflective extraction role.

[0055] In this embodiment, the reflection surfaces of all the first reflection mirrors are arranged parallel to each other to guide the EUV to the same direction (eg, X direction or Z direction).

[0056] In other embodiments, the reflective surfaces of all the first reflectors may not be parallel to each other. When multiple first reflectors 10 work together, the direction of the outgoing light beam of each first reflector 10 is independent, and may be consistent or inconsistent (for example, when three first reflectors 10 are involved in the work, the three reflectors may simultaneously lead out to the X direction, or simultaneously lead out to the Z direction, or the three reflectors may each have a different leading direction), as long as the work of the first reflector 10 in front does not affect the work of other first reflectors 10 behind.

[0057] In this embodiment, all the first reflectors 10 are mounted on the same reflector fixing rail (ie, the first reflector fixing rail 30 ).

[0058] Second embodiment: Radiation extraction device of a resonant cavity type extreme ultraviolet free electron laser that obtains an extracted beam by two reflections

[0059] like Figure 3B The figure shows a radiation extraction device according to a second embodiment of the present invention, wherein the radiation extraction device comprises one or more parallel arranged first reflectors 10 distributed on one side of the main axis of the resonant cavity, and a second reflector 20 distributed on the other side of the main axis of the resonant cavity, and an extraction beam is obtained by twice reflecting the radiation beam in the resonant cavity by the first reflector 10 and the second reflector 20.

[0060] The first reflector 10 is arranged along the main axis direction of the resonant cavity and is configured to receive a portion of the radiation beam in the resonant cavity (i.e., the EUV beam being resonantly amplified), thereby playing a role of reflection and extraction; the second reflector 20 is located outside the optical path of the resonant cavity and is configured to receive the outgoing beam from the first reflector 10, thereby playing a role of adjusting the reflection direction.

[0061] In this embodiment, there are plural first reflectors 10 and plural second reflectors 20 , and the first reflectors 10 and the second reflectors 20 correspond to each other one by one.

[0062] In other embodiments, when the number of the first reflector 10 and the second reflector 20 is single, the EUV beam is extracted in a single channel; when the number of at least one of the first reflector and the second reflector is multiple, the EUV beam can be extracted in multiple channels. The first reflector 10 and the second reflector 20 can correspond to each other one by one, or can be used in a one-to-many or many-to-one manner, and the light beam in the resonant cavity is extracted by reflecting the light beam in the resonant cavity twice.

[0063] In this embodiment, when working, the reflective surfaces of all the first reflectors 10 are arranged parallel to each other, and the reflective surfaces of all the second reflectors 10 are parallel to the reflective surfaces of the first reflectors 10; all the first reflectors 10 are installed on the same reflector fixing rail (i.e., the first reflector fixing rail 30), and all the second reflectors 20 are installed on another reflector fixing rail (i.e., the second reflector fixing rail 40).

[0064] In other embodiments, during operation, the reflective surfaces of the first reflector 10 may be non-parallel to each other, and the first reflector 10 and the second reflector 20 corresponding to each other may be arranged in parallel or non-parallel.

[0065] In this embodiment, the angle between the reflection surface of all the first reflectors 10 and the main axis of the resonant cavity is a fixed angle, which matches the designed reflection angle of the multilayer film reflector. In this embodiment, the angle between the reflection surface of all the first reflectors 10 and the main axis of the resonant cavity is 45°.

[0066] The specific arrangement of all the first reflecting mirrors 10 and the second reflecting mirrors 20 in the first and second embodiments will be described below.

[0067] In the EUV band, two coating methods are usually used for total reflection mirrors:

[0068] a) Grazing incidence: A single-layer reflector coated on a silicon substrate, such as silicon carbide (SiC), rubidium (Ru), etc. The advantage is that it is easy to prepare. The disadvantage is that it can only be used at a small angle of grazing incidence.

[0069] b) A reflector with a multilayer film on a silicon substrate for large angle incidence. The multilayer film structure is composed of two single layers of materials stacked together. Each double layer of the multilayer film has a high electron density material layer A with uniform electron distribution, and a low electron density material layer B. The entire multilayer film structure is composed of these two materials alternately stacked and plated on a silicon substrate. For example: molybdenum (Mo) / silicon (Si) multilayer film structure. The advantage is that high reflectivity for EUV radiation can be achieved at large angles. The disadvantage is that the preparation process is complicated and usually requires the use of precise magnetron sputtering coating equipment.

[0070] In the present invention, both the first reflector 10 and the second reflector 20 are EUV multi-layer film reflectors to ensure high reflectivity requirements for EUV radiation at large angles.

[0071] The multilayer film of the multilayer film reflector can be Mo / Si multilayer film, which is one of the most standard multilayer films for wavelengths near 13.5nm, and the peak reflectivity near the wavelength of 13.5nm exceeds 60%. This mirror is widely used in EUV lithography, astronomy, attosecond science and other fields.

[0072] The front sides of the first reflector 10 and the second reflector 20 are coated with multi-layer films, while the back sides are not, so the reflection of EUV by the back sides of the mirrors can be almost ignored; and the radiation received by the back sides does not affect the outgoing light path, so the influence of the back sides can be ignored.

[0073] The first reflector 10 and the second reflector 20 may be flat or curved. If a flat surface is used, it mainly helps EUV light to turn, while if a curved surface is used, it mainly helps EUV light to achieve the functional requirements of turning and expanding.

[0074] All the first reflectors 10 are used to reflect a portion of the EUV beam being resonated and amplified in the resonant cavity, so that when the radiation extraction device is in operation, a portion of the EUV beam is still retained in the resonant cavity to continue to be resonated and amplified, and at least 10% of the beam energy is retained. Here, at least 10% is retained, which means that when the device is used, the reflector does not completely intercept all the EUV radiation beams in the resonant cavity, but leaks at least 10% of the radiation beams to continue to be transmitted in the resonant cavity.

[0075] The radiation extraction device further includes a reflector fixing slider 101 slidable on the reflector fixing slide rail, a vertical telescopic device 102 fixed on the reflector fixing slider 101, and a reflector rotating device 103 disposed at the top of the vertical telescopic device 102 and connected to the back mirror seat of the corresponding first reflector 10 or second reflector 20. Thus, the first reflector 10 and the second reflector 20 are installed on the reflector fixing slide rail.

[0076] Among them, the mirror rotation device 103 supports 360-degree rotation of the reflection surface of the first reflector 10 and the second reflector 20 (supports electrical control), which is used to adjust the reflection surface and reflection angle of the EUV multi-layer film reflector, and is fixed in the central area of ​​the back mirror seat of the reflector to adjust the reflection beam angle of the reflector.

[0077] The vertical telescopic device 102 connects the reflector rotating device 103 and the reflector fixing slider 101. It is telescopic (supports electrical control) and is used to adjust the relative position of the reflective surface of the reflector perpendicular to the main axis of the resonant cavity. It can also be used to adjust the proportion of the radiation beam emitted by the reflector relative to the total radiation beam in the resonant cavity.

[0078] The movable direction of the reflector fixing slider 101 is parallel to the main axis of the resonant cavity (ie Figure 3A and Figure 3B These can facilitate the positioning, sliding, disassembly, and maintenance of the reflector on the wall of the FEL resonant cavity.

[0079] According to Figure 3AThe radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser shown in the figure obtains the extracted light beam based on a single reflection. The radiation extraction device has four corresponding radiation extraction methods of the resonant cavity type extreme ultraviolet free electron laser, which will be specifically introduced in detail through the third to sixth embodiments below.

[0080] Third embodiment: Radiation extraction method of resonant cavity type extreme ultraviolet free electron laser

[0081] like Figure 4A and Figure 4B As shown, according to the third embodiment of the present invention, the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser specifically includes:

[0082] Step S301: Install the following in the resonant cavity EUV free electron laser: Figure 3A The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser shown;

[0083] Step S302: By moving the first reflector 10, when the resonant cavity type extreme ultraviolet free electron laser is in working state, only one first reflector 10 receives a part of the radiation beam in the resonant cavity and reflects it to obtain an outgoing beam, while the other first reflectors 10 are outside the optical path of the resonant cavity and therefore do not receive the radiation beam in the resonant cavity.

[0084] The first reflector 10 receives and reflects a portion of the radiation beam in the resonant cavity, which means that the first reflector 10 receives at most 90% of the radiation beam in the resonant cavity, and the remaining EUV beam continues to oscillate and amplify in the resonant cavity.

[0085] The direction of the outgoing light beam of the first reflector 10 is the z direction (ie, the vertical direction) in the figure. Figure 4A and Figure 4B The two different orientations of the reflective mirror surfaces in the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser of the third embodiment are respectively shown; specifically, the relative relationship between the resonant cavity and the EUV multilayer film reflector is: the first reflector 10 faces the undulator 300 or away from the undulator 300, and the angle between the first reflector 10 and the main axis of the resonant cavity is a fixed angle, which matches the designed reflection angle of the multilayer film reflector.

[0086] Fourth embodiment: Radiation extraction method of resonant cavity type extreme ultraviolet free electron laser

[0087] like Figure 5 As shown, according to the fourth embodiment of the present invention, the specific steps of the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser are basically the same as the radiation extraction method according to the third embodiment of the present invention, that is, specifically comprising:

[0088] Step S401: Install the following in the resonant cavity EUV free electron laser: Figure 3A The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser shown;

[0089] Step S402: By moving the first reflector 10, when the resonant cavity type extreme ultraviolet free electron laser is in working state, only one first reflector 10 receives a part of the radiation beam in the resonant cavity and reflects it to obtain an outgoing beam, while the other first reflectors 10 are outside the optical path of the resonant cavity and therefore do not receive the radiation beam in the resonant cavity.

[0090] The first reflector 10 receives and reflects a portion of the radiation beam in the resonant cavity, which means that the first reflector 10 receives at most 90% of the radiation beam in the resonant cavity, and the remaining EUV beam continues to oscillate and amplify in the resonant cavity.

[0091] The only difference between the third embodiment and the fourth embodiment is that in the fourth embodiment, the direction of the outgoing light beam of the first reflector 10 is the x direction in the figure.

[0092] Fifth embodiment: Radiation extraction method of resonant cavity type extreme ultraviolet free electron laser

[0093] like Fig. 6A and Figure 6B As shown, according to the fifth embodiment of the present invention, the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser specifically includes:

[0094] Step S501: Install the following in the resonant cavity EUV free electron laser: Figure 3A The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser shown;

[0095] Step S502: By moving the first reflector 10, when the resonant cavity type extreme ultraviolet free electron laser is in working state, multiple first reflectors 10 are arranged in the resonant cavity in a horizontal distribution and a stepped height distribution along the main axis direction of the resonant cavity, so as to respectively receive a part of the radiation beam in the resonant cavity and reflect it to obtain an outgoing beam, while other first reflectors 10 are outside the optical path of the resonant cavity and therefore do not receive the radiation beam in the resonant cavity.

[0096] Among them, multiple first reflectors 10 respectively receive and reflect a portion of the radiation beam in the resonant cavity, which means that all the first reflectors 10 receive at most 90% of the radiation beam in the resonant cavity, and the remaining EUV beam continues to oscillate and amplify in the resonant cavity.

[0097] In this embodiment, the direction of the outgoing light beam of the first reflector 10 is the z direction (ie, the vertical direction) in the figure.

[0098] Due to the stepped height distribution, the first reflectors 10 with different reflections reflect a portion of the radiation beam and the reflection of each does not affect the operation of the remaining first reflectors 10. Therefore, in other embodiments, when the multiple first reflectors 10 receive a portion of the radiation beam in the resonant cavity and reflect it, each first reflector 10 can lead the radiation beam to the X direction or the Z direction, so that the direction of the output beam of each first reflector 10 can be the X direction or the Z direction; the directions of the output beams of the multiple first reflectors 10 are independent of each other, and can be consistent or inconsistent (for example, in device A: when the output device is working, three reflectors are involved, and the three reflectors can be simultaneously led to the X direction, can be simultaneously led to the Z direction, or can each of the three reflectors have a different output direction).

[0099] Fig. 6A and Figure 6B The two different orientations of the reflective mirror surfaces in the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser of the fifth embodiment are respectively shown; specifically, the relative relationship between the resonant cavity and the EUV multilayer film reflector is: the first reflector 10 faces the undulator 300 or away from the undulator 300, and the angle between the first reflector 10 and the main axis of the resonant cavity is a fixed angle, which matches the designed reflection angle of the multilayer film reflector.

[0100] Sixth embodiment: Radiation extraction method of resonant cavity type extreme ultraviolet free electron laser

[0101] like Figure 7 As shown, according to the sixth embodiment of the present invention, the specific steps of the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser are basically the same as the radiation extraction method according to the fifth embodiment of the present invention, that is, specifically comprising:

[0102] Step S601: Install the following in the resonant cavity EUV free electron laser: Figure 3A The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser shown;

[0103] Step S602: By moving the first reflector 10, when the resonant cavity type extreme ultraviolet free electron laser is in working state, multiple first reflectors 10 are arranged in the resonant cavity in a horizontal distribution and a stepped height distribution along the main axis direction of the resonant cavity, so as to respectively receive and reflect a part of the radiation beam in the resonant cavity, while the other first reflectors 10 are outside the optical path of the resonant cavity and therefore do not receive the radiation beam in the resonant cavity.

[0104] Among them, multiple first reflectors 10 respectively receive and reflect a portion of the radiation beam in the resonant cavity, which means that all the first reflectors 10 receive at most 90% of the radiation beam in the resonant cavity, and the remaining EUV beam continues to oscillate and amplify in the resonant cavity.

[0105] The only difference between the sixth embodiment and the fifth embodiment is that in the sixth embodiment, the direction of the outgoing light beam of the first reflector 10 is the x direction in the figure (ie, the horizontal direction perpendicular to the main axis of the resonant cavity).

[0106] According to Figure 3B The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser shown in the figure obtains the extracted light beam based on a single reflection. The radiation extraction device has four corresponding radiation extraction methods of the resonant cavity type extreme ultraviolet free electron laser, which will be introduced in detail through the seventh to tenth embodiments below.

[0107] Seventh embodiment: Radiation extraction method of resonant cavity type extreme ultraviolet free electron laser

[0108] like Fig. 8A and Figure 8B As shown, according to the fourth embodiment of the present invention, the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser specifically includes:

[0109] Step S701: Install the following in the resonant cavity EUV free electron laser: Figure 3B The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser shown;

[0110] Step S702: By moving the first reflector 10 and the second reflector 20, when the resonant cavity type extreme ultraviolet free electron laser is in working state, only one first reflector 10 receives a part of the radiation beam in the resonant cavity and reflects it to obtain an outgoing beam, and the corresponding second reflector 20 reflects the outgoing beam from the first reflector 10, while the other first reflectors 10 are outside the optical path of the resonant cavity and therefore do not receive the radiation beam in the resonant cavity.

[0111] In a pair of mirrors (a first reflector 10 and a second reflector 20) that actually participate in the EUV reflection work, the first reflector 10 is used to receive and reflect a portion of the radiation beam in the resonant cavity, and the second reflector 20 is used to adjust the EUV extraction direction to the y direction, that is, parallel to the main axis direction of the resonant cavity.

[0112] The first reflector 10 receives and reflects a portion of the radiation beam in the resonant cavity, which means that the first reflector 10 receives at most 90% of the radiation beam in the resonant cavity, and the remaining EUV beam continues to oscillate and amplify in the resonant cavity. The direction of the outgoing beam of the first reflector 10 is the z direction (i.e., the vertical direction) in the figure.

[0113] Fig. 8A and Figure 8B The directions of two different mirror surfaces in the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser of the seventh embodiment are respectively shown; specifically, the relative relationship between the resonant cavity and the EUV multilayer film reflector is: the first reflector 10 faces the undulator 300 or away from the undulator 300, and the angle between the first reflector 10 and the main axis of the resonant cavity is a fixed angle, which matches the designed reflection angle of the multilayer film reflector; the second reflector 20 is parallel to the corresponding first reflector 10, or forms a 90° angle with the corresponding first reflector 10.

[0114] Eighth embodiment: Radiation extraction method of resonant cavity type extreme ultraviolet free electron laser

[0115] like Fig.9A and Fig. 9B As shown, according to the eighth embodiment of the present invention, the specific steps of the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser are basically the same as the radiation extraction method according to the seventh embodiment of the present invention, that is, specifically comprising:

[0116] Step S801: Install the following in the resonant cavity EUV free electron laser: Figure 3B The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser shown;

[0117] Step S802: By moving the first reflector 10 and the second reflector 20, when the resonant cavity type extreme ultraviolet free electron laser is in working state, only one first reflector 10 receives a part of the radiation beam in the resonant cavity and reflects it to obtain an outgoing beam, and the corresponding second reflector 20 reflects the outgoing beam from the first reflector 10, while the other first reflectors 10 are outside the optical path of the resonant cavity and therefore do not receive the radiation beam in the resonant cavity.

[0118] In a pair of mirrors (a first reflector 10 and a second reflector 20) that actually participate in the EUV reflection work, the first reflector 10 is used to receive and reflect a portion of the radiation beam in the resonant cavity, and the second reflector 20 is used to adjust the EUV extraction direction to the y direction, that is, parallel to the main axis direction of the resonant cavity.

[0119] The first reflector 10 receives and reflects a portion of the radiation beam in the resonant cavity, which means that the first reflector 10 receives at most 90% of the radiation beam in the resonant cavity, and the remaining EUV beam continues to oscillate and amplify in the resonant cavity.

[0120] The only difference between the eighth embodiment and the seventh embodiment is that, in the eighth embodiment, the direction of the outgoing light beam of the first reflector 10 is the x direction in the figure (ie, the horizontal direction perpendicular to the main axis of the resonant cavity).

[0121] Fig. 8A and Figure 8B The two different orientations of the reflective mirror surfaces in the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser of the seventh embodiment are respectively shown; specifically, the relative relationship between the resonant cavity and the EUV multilayer film reflector is: the angle between the first reflector 10 and the main axis of the resonant cavity is a fixed angle, which matches the designed reflection angle of the multilayer film reflector; the second reflector 20 is located in the positive x-direction or negative x-direction of the corresponding first reflector 10; the second reflector 20 is parallel to the corresponding first reflector 10, or forms a 90° angle with the corresponding first reflector 10.

[0122] Ninth embodiment: Radiation extraction method of resonant cavity type extreme ultraviolet free electron laser

[0123] like Fig. 10A and Fig. 10B As shown, according to the ninth embodiment of the present invention, the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser specifically includes:

[0124] Step S901: Install the following in the resonant cavity EUV free electron laser: Figure 3B The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser shown;

[0125] Step S902: By moving the first reflector 10 and the second reflector 20, when the resonant cavity type extreme ultraviolet free electron laser is in an operating state, multiple first reflectors 10 are arranged in the resonant cavity in a horizontal distribution and a stepped height distribution along the main axis direction of the resonant cavity, so as to respectively receive a part of the radiation beam in the resonant cavity and reflect it to obtain an outgoing beam; and for each first reflector 10, the corresponding second reflector 20 is arranged in a horizontal distribution and a stepped height distribution along the main axis direction of the resonant cavity to reflect the outgoing beam from the first reflector 10.

[0126] Among the multiple pairs of mirrors (first reflector 10 and second reflector 20) that actually participate in EUV reflection work, the first reflector 10 is used to receive and reflect a portion of the radiation beam in the resonant cavity, and the second reflector 20 is used to adjust the EUV extraction direction to the y direction, that is, parallel to the main axis direction of the resonant cavity.

[0127] The first reflector 10 receives and reflects a portion of the radiation beam in the resonant cavity, which means that the first reflector 10 receives at most 90% of the radiation beam in the resonant cavity, and the remaining EUV beam continues to oscillate and amplify in the resonant cavity.

[0128] The direction of the outgoing light beam of the first reflector 10 is the z direction (ie, the vertical direction) in the figure.

[0129] Due to the stepped height distribution, different first reflectors 10 reflect a portion of the radiation beam and their respective reflections do not affect the operation of the remaining first reflectors 10. Therefore, in other embodiments, when multiple first reflectors 10 receive and reflect a portion of the radiation beam in the resonant cavity, each first reflector 10 can lead the radiation beam to the x direction or the z direction, so that the direction of the outgoing beam of each first reflector 10 can be the x direction or the z direction; the directions of the outgoing beams of multiple first reflectors 10 are independent of each other and can be consistent or inconsistent. Similarly, different second reflectors 20 are independent of each other. The second reflector 20 is parallel to its corresponding first reflector 10, or forms a 90° angle with its corresponding first reflector 10; and the relative position of the second reflector 20 and its corresponding first reflector 10 is arbitrary, as long as the outgoing beam of the first reflector 10 can be received.

[0130] Fig. 10A and Fig. 10B The directions of two different reflective mirror surfaces in the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser of the ninth embodiment are respectively shown; specifically, the relative relationship between the resonant cavity and the EUV multilayer film reflector is: the first reflector 10 is facing the undulator 300 or away from the undulator 300, and the angle between the first reflector 10 and the main axis of the resonant cavity is a fixed angle, which matches the designed reflection angle of the multilayer film reflector; the second reflector 20 is parallel to the corresponding first reflector 10, or forms a 90° angle with the corresponding first reflector 10.

[0131] Tenth embodiment: Radiation extraction method of a resonant cavity type extreme ultraviolet free electron laser

[0132] like Fig.11A and Fig. 11BAs shown, according to the tenth embodiment of the present invention, the specific steps of the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser are basically the same as the radiation extraction method according to the ninth embodiment of the present invention, that is, specifically comprising:

[0133] Step S1001: Install the following in the resonant cavity EUV free electron laser: Figure 3B The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser shown;

[0134] Step S1002: By moving the first reflector 10 and the second reflector 20, when the resonant cavity type extreme ultraviolet free electron laser is in an operating state, multiple first reflectors 10 are arranged in the resonant cavity in a horizontal distribution and a stepped height distribution along the main axis direction of the resonant cavity, so as to respectively receive a part of the radiation beam in the resonant cavity and reflect it to obtain an outgoing beam; and for each first reflector 10, the corresponding second reflector 20 is arranged in a horizontal distribution and a stepped height distribution along the main axis direction of the resonant cavity to reflect the outgoing beam from the first reflector 10.

[0135] Among the multiple pairs of mirrors (first reflector 10 and second reflector 20) that actually participate in EUV reflection work, the first reflector 10 is used to receive and reflect a portion of the radiation beam in the resonant cavity, and the second reflector 20 is used to adjust the EUV extraction direction to the y direction, that is, parallel to the main axis direction of the resonant cavity.

[0136] The first reflector 10 receives and reflects a portion of the radiation beam in the resonant cavity, which means that the first reflector 10 receives at most 90% of the radiation beam in the resonant cavity, and the remaining EUV beam continues to oscillate and amplify in the resonant cavity.

[0137] The only difference between the tenth embodiment and the ninth embodiment is that, in the tenth embodiment, the direction of the outgoing light beam of the first reflector 10 is the x direction in the figure (ie, the horizontal direction perpendicular to the main axis of the resonant cavity).

[0138] Fig.11A and Fig. 11B The directions of two different reflective mirror surfaces in the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser of the tenth embodiment are respectively shown; specifically, the relative relationship between the resonant cavity and the EUV multilayer film reflector is: the first reflector 10 is facing the undulator 300 or away from the undulator 300, and the angle between the first reflector 10 and the main axis of the resonant cavity is a fixed angle, which matches the designed reflection angle of the multilayer film reflector; the second reflector 20 is located in the positive x-direction or negative x-direction of the corresponding first reflector 10; the second reflector 20 is parallel to the corresponding first reflector 10, or forms a 90° angle with the corresponding first reflector 10.

[0139] Example 11: Radiation extraction method of a resonant cavity type extreme ultraviolet free electron laser

[0140] like Fig. 12A and Fig. 12B As shown, according to the eleventh embodiment of the present invention, the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser shows the combined use of a lower side reflector and a plurality of upper side reflectors. The radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser specifically includes:

[0141] Step S1101: Install the following in the resonant cavity EUV free electron laser: Figure 3B The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser shown;

[0142] Step S1102: By moving the first reflector 10 and the second reflector 20, when the resonant cavity type extreme ultraviolet free electron laser is in working state, a first reflector 10 is arranged in the resonant cavity to receive a part of the radiation beam in the resonant cavity and reflect it to obtain an outgoing beam; and for the first reflector 10, the corresponding multiple second reflectors 20 are arranged in a horizontal distribution and a stepped height distribution along the main axis direction of the resonant cavity to reflect the outgoing beam from the first reflector 10.

[0143] Among the multiple pairs of mirrors (first reflector 10 and second reflector 20) that actually participate in EUV reflection work, the first reflector 10 is used to receive and reflect a portion of the radiation beam in the resonant cavity, and the second reflector 20 is used to adjust the EUV extraction direction to the y direction, that is, parallel to the main axis direction of the resonant cavity.

[0144] The first reflector 10 receives and reflects a portion of the radiation beam in the resonant cavity, which means that the first reflector 10 receives at most 90% of the radiation beam in the resonant cavity, and the remaining EUV beam continues to oscillate and amplify in the resonant cavity.

[0145] In this embodiment, the direction of the outgoing light beam of the first reflector 10 is the z direction (ie, the vertical direction) in the figure.

[0146] Fig. 12A and Fig. 12BThe directions of two different mirror surfaces in the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser of the eleventh embodiment are respectively shown; specifically, the relative relationship between the resonant cavity and the EUV multilayer film reflector is: the first reflector 10 is facing the undulator 300 or away from the undulator 300, and the angle between the first reflector 10 and the main axis of the resonant cavity is a fixed angle, which matches the designed reflection angle of the multilayer film reflector; the second reflector 20 is parallel to the corresponding first reflector 10, or forms a 90° angle with the corresponding first reflector 10.

[0147] Example 12: Radiation extraction method of a resonant cavity extreme ultraviolet free electron laser

[0148] like Fig.13A and Fig. 13B As shown, according to the twelfth embodiment of the present invention, the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser shows the combined use of multiple first reflectors 10 and a corresponding second reflector 20. The radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser specifically includes:

[0149] Step S1201: Install the following in the resonant cavity EUV free electron laser: Figure 3B The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser shown;

[0150] Step S1202: By moving the first reflector 10 and the second reflector 20, when the resonant cavity type extreme ultraviolet free electron laser is in working state, multiple first reflectors 10 are arranged in the resonant cavity in a horizontal distribution and a stepped height distribution along the main axis direction of the resonant cavity, so as to respectively receive a part of the radiation beam in the resonant cavity and reflect it to obtain an outgoing beam; and the corresponding same second reflector 20 reflects the outgoing beams from all the first reflectors 10.

[0151] Among the multiple pairs of mirrors (the first reflector 10 and the second reflector 20) that actually participate in the EUV reflection work, the first reflector 10 is used to receive and reflect a part of the radiation beam in the resonant cavity, and the second reflector 20 is used to adjust the extraction direction of EUV to the y direction, that is, the direction of the output light beam of the second reflector 20 is parallel to the main axis direction of the resonant cavity.

[0152] The first reflector 10 receives and reflects a portion of the radiation beam in the resonant cavity, which means that the first reflector 10 receives at most 90% of the radiation beam in the resonant cavity, and the remaining EUV beam continues to oscillate and amplify in the resonant cavity.

[0153] In this embodiment, the direction of the outgoing light beam of the first reflector 10 is the z direction (ie, the vertical direction) in the figure.

[0154] Fig.11A and Fig. 11B The directions of two different reflective mirror surfaces in the radiation extraction method of the resonant cavity type extreme ultraviolet free electron laser of the ninth embodiment are respectively shown; specifically, the relative relationship between the resonant cavity and the EUV multilayer film reflector is: the first reflector 10 is facing the undulator 300 or away from the undulator 300, and the angle between the first reflector 10 and the main axis of the resonant cavity is a fixed angle, which matches the designed reflection angle of the multilayer film reflector; the second reflector 20 is parallel to the corresponding first reflector 10, or forms a 90° angle with the corresponding first reflector 10.

[0155] As described above, the first reflector 10 and the second reflector 20 are both EUV multilayer reflectors to ensure the high reflectivity requirements of EUV radiation at large angles. A reflector with a multilayer film coated on a silicon substrate with large angle incidence, the multilayer film structure is composed of two single layers of materials stacked together, and each double layer of the multilayer film has a high electron density material layer A with uniform electron distribution, and a low electron density material layer B. The entire multilayer film structure is composed of these two materials alternately stacked and coated on a silicon substrate. For example: molybdenum (Mo) / silicon (Si) multilayer film structure.

[0156] The following uses Mo / Si multilayer film as an example to illustrate the design method of the EUV multilayer film reflector used by the first reflector 10 and the second reflector 20 .

[0157] like Fig.14 It can be seen that the Mo / Si multilayer film is a film structure composed of thin layers of Mo and Si stacked alternately. This structure is usually a periodic stacking of two materials. According to the Bragg formula, it can be known that this structure can efficiently reflect the incident EUV beam. Assume that the thickness of a single layer of Mo is d Mo , the refractive index is n Mo Assume the thickness of a single layer of Si is d Si , the refractive index is n Si See the reference [Als-Nielsen, Jens, McMorrow, Des. Principles of Modern X-ray Physics [M]. Fudan University Press, 2015], where the refractive index of Mo / Si multilayer film can be expressed as:

[0158] n=1-δ+iβ (1)

[0159] See the literature [Attwood D, Sakdinawat AX-rays and extreme ultraviolet radiation: principles and applications [M]. Cambridge university press, 2017] Assume that the thickness ratio of the single layer film is Γ = d Mo / (d Mo +d Si ), then according to formula (2), under normal incidence, after optimization, the thickness ratio of the two materials is Γ opt for:

[0160]

[0161] Therefore, substituting into the Bragg formula applicable to the multilayer film, the period thickness Δ of the multilayer film can be obtained:

[0162]

[0163] Where λ is the EUV radiation wavelength, Δ=d Mo +d Si is the period length of the multilayer film, and θ is the grazing incidence angle of the incident mirror.

[0164] By substituting the material coefficients, we can design EUV multilayer film structures for incident light at specific angles.

[0165] like Fig.15 As shown, the design of Mo / Si multilayers is mainly divided into the following steps:

[0166] Step A1: Determine the applicable wavelength band λ of the Mo / Si multilayer film and the grazing incidence angle θ of the incident reflective mirror.

[0167] Among them, under specific design requirements, the designed multilayer film has a usable incident and reflection angle adjustment range, within which high reflectivity can be achieved. Beyond this angle range, the reflectivity drops sharply.

[0168] Step A2: Obtain the refractive index values ​​n of Mo and Si in the corresponding applicable band λ Mo 、n Si ;

[0169] Step A3: Determine the multilayer film structure parameters, which include the thickness ratio of the two materials Γ opt and the periodic thickness Δ of the multilayer film.

[0170] The specific process of step A3 is as follows:

[0171] Step A31: According to the refractive index n of Mo Mo and the refractive index n of Si Si , calculate the thickness ratio Γ of the two materials according to formula (2) op t.

[0172] Step A32: Change the refractive index n of Mo Mo 、The refractive index of Si is n Si , grazing incidence angle θ and the resulting Γ opt , substituting into formula (3), we can obtain the period thickness Δ of the multilayer film.

[0173] Step A4: Calculating the reflectivity of the multilayer film according to the multilayer film structure parameters;

[0174] Among them, a suitable method is selected to calculate the reflectivity of the multilayer film, for example: Parratt's rigorous iteration method (see the literature [Als-Nielsen, Jens, McMorrow, Des. Principles of Modern X-ray Physics [M]. Fudan University Press, 2015]).

[0175] The steps to calculate the reflectivity of multilayer films using Parratt's rigorous iteration method are as follows:

[0176] Step A41: Substitute the designed wavelength λ, grazing incidence angle θ, and the refractive index n of Mo. Mo 、The refractive index of Si is n Si , and the obtained Γ opt , get the thickness of the multilayer film Δ, set the number of double-layer combinations of Mo and Si N Mo / Si Substitute Parratt's strict iteration method for an initial range (e.g. 1 to 150) to calculate the minimum number of layers N for maximum reflectivity max ;

[0177] Step A42: Set the initial number of layers N Mo / Si =N max .

[0178] Step A43: Calculate when the number of layers is N max The relationship between the reflectivity of the multilayer film and the incident angle and radiation wavelength is measured to confirm whether the reflection curve covers the incident angle and incident radiation wavelength we designed.

[0179] Step A5: Use Shadow software to perform optical tracing calculation on the reflection process of the multilayer film reflector having the above multilayer film structure parameters to obtain an optical tracing result, which is the distribution of light spots passing through the light reflector (the tracing result meets the required standard that the number of input light rays traced is consistent with the number of output light rays, which means that each light ray has been reflected and transmitted by the optical system);

[0180] Optical tracing uses the existing open source optical tracing platform Shadow, references [M. Sanchez del Rio. N. Canestrari, F. Jiang and F. Cerrina "SHADOW3: a new version of the synchrotron X-ray optics modelling package" J. Synchrotron Rad. (2011). 18, 708-716], [Manuel Sánchez del Río and Roger J. Dejus "XOP v2.4: recent developments of the x-ray optics software toolkit", Proc. SPIE 8141, Advances in Computational Methods for X-Ray Optics II, 814115 (23 September 2011); https: / / doi.org / 10.1117 / 12.893911].

[0181] Step A6: Optimizing the multilayer film structure parameters and the grazing incidence angle θ of the incident reflective mirror surface according to the calculation results of the reflectivity of the multilayer film and the optical tracing results;

[0182] Generally speaking, following the above steps A1-A5, the result of a single design can meet our needs and no iterative optimization is needed. However, iterative optimization may be required in some special cases. The optimized parameter is mainly the thickness ratio Γ of the two materials. opt and the grazing incidence angle θ of the incident mirror.

[0183] The steps of step A6 are as follows:

[0184] Step A61: Simultaneously traverse the grazing incidence angle θ and the thickness ratio of the monolayer film Γ=d Mo / d Si , calculate the reflectivity curve of the multilayer film, and examine whether the reflectivity curve contains the required incident angle and incident wavelength. (Traversal range: the appropriate angle range before and after the initial grazing incident angle, for example: the incident angle in the original design is 45°, then the traversal range is 44%-46%) (traversal range is Γ=0.1-0.9, traversal interval is 0.01-0.05);

[0185] Step A62: selecting a combination of a grazing incidence angle θ and a single-layer film thickness ratio Γ with the highest reflectivity;

[0186] Step A63: Use the result of the optimal combination to perform an optical tracing simulation and confirm that it can be used (the standard is that the number of input rays of the tracing is consistent with the number of output rays, which means that each ray has been reflected and transmitted by the optical system);

[0187] Step A64: If the requirements are met, the multilayer film design is terminated; if the requirements are not met, the grazing incidence angle θ is readjusted, and steps A61 and A62 are repeated until the requirements are met.

[0188] Experimental results:

[0189] Taking Mo / Si multilayer film at 45° grazing incidence 13.5nm EUV FEL radiation as an example, a periodic multilayer film design is performed, and the multilayer film structure parameters shown in Table 1 can be obtained.

[0190] Table 1: Mo / Si periodic multilayer film structural parameters at 45° grazing incidence 13.5nm multilayer film

[0191] FIG16 is a reflectivity curve of Mo / Si multilayer film. Fig.16A The relationship between the reflectivity of the multilayer film and the number of layers in the multilayer film is shown. Fig. 16B The relationship between the reflectivity of the multilayer film and the incident angle is shown. Fig. 16C The relationship between the reflectivity of the multilayer film and the wavelength of the radiation is shown. Fig.16A As shown in the figure, by calculating the reflectivity of 13.5nm EUV radiation at 45° grazing incidence on the surface of multilayer film mirrors with different numbers of layers, it is known that when N Mo / Si When it is 30, the maximum reflectivity is basically reached, so N max =30 is the design parameter of the double-layer film structure in this design example. We take 30 cycles as a calculation example and calculate the reflectivity of the multilayer film. Fig. 16B What is calculated is the reflectivity curve of the multilayer film structure in the EUV wavelength range of 9nm-18nm. It can be seen that the radiation wavelength λ corresponding to the highest reflectivity of the structure is 13.5nm (i.e., the central wavelength). Fig. 16C The reflectivity curve of the multilayer film structure at 30° to 60° is calculated. It can be seen that the highest reflectivity of the structure is around 45° (design incident angle), which meets the requirements of this design example.

[0192] By applying the above multilayer film on a flat mirror, we simulated a surface with a certain spatial divergence (σ X =0.038cm,σ Z =0.038cm) and angular divergence (σ X =44μrad,σ Z=44 μrad) of 13.5 nm FEL radiation at 45°. Reflection of a multilayer film reflector at grazing incidence.

[0193] When the FEL is extracted through one multilayer film reflector and two multilayer film reflectors, for 13.5nm radiation, the current multilayer film reflector supports the extraction device to achieve the FEL extraction effect through one or two mirrors. Fig.17 and Fig.18 The tracing effects of FEL extraction through one multilayer film reflector and two multilayer film reflectors are shown respectively. The corresponding optical path structure and the distribution of light spots before and after reflection are shown in the figure. From the tracing results, it can be seen that the light spot can be extracted through the reflector, indicating that the current multilayer film reflector design supports the extraction device to achieve the effect of FEL extraction through one or two reflectors.

[0194] The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The above embodiments of the present invention can also be modified in various ways. All simple, equivalent changes and modifications made according to the claims and the description of the present invention fall within the scope of protection of the claims of the present invention. The contents not described in detail in the present invention are all conventional technical contents.

Claims

1. A radiation extraction device for a resonant cavity type extreme ultraviolet free electron laser, characterized in that: It includes one or more first reflectors distributed on one side of the main axis of the resonant cavity, wherein the first reflectors are configured to receive a portion of the radiation beam in the resonant cavity, and an outgoing beam is obtained at least by reflecting the radiation beam in the resonant cavity by the first reflectors.

2. The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser according to claim 1, characterized in that: There are multiple first reflectors, which are arranged along the main axis of the resonant cavity.

3. The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser according to claim 2, characterized in that: The directions of the light beams emitted by the plurality of first reflectors are consistent, or inconsistent; and / or The direction of the outgoing light beam of each first reflector is a vertical direction, or a horizontal direction perpendicular to the main axis of the resonant cavity.

4. The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser according to claim 1, characterized in that: The radiation extraction device further comprises a reflector fixing slider slidable on the reflector fixing slide rail, a vertical telescopic device fixed on the reflector fixing slider, and a reflector rotating device arranged at the top of the vertical telescopic device and connected to the back mirror seat of the corresponding first reflector; and / or All the first reflectors are mounted on the same reflector fixing slide rail.

5. The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser according to claim 1, characterized in that: It also includes a second reflector distributed on the other side of the main axis of the resonant cavity, and obtains an outgoing light beam by reflecting the radiation light beam in the resonant cavity twice by the first reflector and the second reflector; the second reflector is located outside the optical path of the resonant cavity and is configured to receive the outgoing light beam from its corresponding first reflector, thereby playing a role in adjusting the reflection direction.

6. The radiation extraction device of the resonant cavity type extreme ultraviolet free electron laser according to claim 5, characterized in that: The number of the first reflector and the second reflector is plural, and the first reflector and the second reflector correspond to each other one by one; or, the first reflector and the second reflector correspond to each other in a one-to-many or many-to-one manner; and / or The first reflector and the second reflector are both multi-layer film reflectors; and / or The radiation extraction device also includes a reflector fixing slider that can slide on the reflector fixing slide rail, a vertical telescopic device fixed on the reflector fixing slider, and a reflector rotating device that is arranged at the top of the vertical telescopic device and connected to the back mirror seat of the corresponding first reflector or second reflector; and / or All the first reflectors are mounted on the same reflector fixing slide rail, and all the second reflectors are mounted on another reflector fixing slide rail.

7. A radiation extraction system for a resonant cavity type extreme ultraviolet free electron laser, characterized in that: It comprises a resonant cavity type extreme ultraviolet free electron laser and a radiation extraction device according to any one of claims 1 to 6; the radiation extraction device is located in a vacuum region between an undulator and a resonant cavity mirror inside the resonant cavity of the resonant cavity type extreme ultraviolet free electron laser.

8. A method for extracting radiation from a resonant cavity extreme ultraviolet free electron laser, characterized in that: include: Installing a radiation extraction device of a resonant cavity type extreme ultraviolet free electron laser according to any one of claims 1 to 4 in a resonant cavity type extreme ultraviolet free electron laser; By moving the first reflector, when the resonant cavity type extreme ultraviolet free electron laser is in operation, one or more first reflectors receive a portion of the radiation beam in the resonant cavity and reflect it to obtain an outgoing beam.

9. The radiation extraction method of a resonant cavity type extreme ultraviolet free electron laser according to claim 8, characterized in that: The first reflector receives and reflects a portion of the radiation beam in the resonant cavity, which means that the first reflector receives at most 90% of the radiation beam in the resonant cavity; and / or The direction of the outgoing light beam of the first reflector is a vertical direction or a horizontal direction perpendicular to the main axis of the resonant cavity; and / or The first reflector faces the undulator or turns away from the undulator, and the angle between the first reflector and the main axis of the resonant cavity is a fixed angle, which matches the designed reflection angle of the multilayer film reflector; and / or When there are multiple first reflectors, the multiple first reflectors are arranged in the resonant cavity in a horizontal distribution and a stepped height distribution along the main axis direction of the resonant cavity, so as to respectively receive a part of the radiation beam in the resonant cavity and reflect it to obtain an outgoing beam.

10. A method for extracting radiation from a resonant cavity extreme ultraviolet free electron laser, characterized in that: include: Installing a radiation extraction device of a resonant cavity type extreme ultraviolet free electron laser according to any one of claims 5-6 in a resonant cavity type extreme ultraviolet free electron laser; By moving the first reflector and the second reflector, when the resonant cavity type extreme ultraviolet free electron laser is in working state, one or more first reflectors receive a part of the radiation beam in the resonant cavity and reflect it to obtain an output beam, and the corresponding second reflector reflects the output beam from the first reflector.

11. The radiation extraction method of a resonant cavity type extreme ultraviolet free electron laser according to claim 10, characterized in that: The first reflector receives and reflects a portion of the radiation beam in the resonant cavity, which means that the first reflector receives at most 90% of the radiation beam in the resonant cavity; and / or The direction of the outgoing light beam of the first reflector is a vertical direction or a horizontal direction perpendicular to the main axis of the resonant cavity, and the direction of the outgoing light beam of the second reflector is parallel to the main axis direction of the resonant cavity; and / or The first reflector faces the undulator or turns away from the undulator, and the angle between the first reflector and the main axis of the resonant cavity is a fixed angle, which matches the designed reflection angle of the multilayer film reflector; and / or When there are multiple first reflectors for obtaining the extracted light beam, the multiple first reflectors are arranged in the resonant cavity in a horizontal distribution and a stepped height distribution along the main axis direction of the resonant cavity, so as to respectively receive a part of the radiation light beam in the resonant cavity and reflect it to obtain the extracted light beam; and / or When there are multiple second reflectors for reflecting the extracted light beam, the multiple second reflectors are arranged in a horizontal distribution and a stepped height distribution along the main axis direction of the resonant cavity to reflect the extracted light beam from the first reflector; and / or The number of the first reflector and the second reflector is plural, and the first reflector and the second reflector correspond to each other one by one; or, the first reflector and the second reflector correspond to each other in a one-to-many or many-to-one manner.

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