A multi-wavelength extreme ultraviolet tabletop light source based on absorption spectral lines

Abstract

This invention discloses a multi-wavelength extreme ultraviolet (EUV) benchtop light source based on absorption spectral lines, belonging to the field of special light source technology. This invention utilizes a high-power laser to ablate a target material with a high atomic number to generate continuous spectral emission in the EUV band. After being collected by a collecting mirror, the emission passes through a neutral or ionized gas to produce multi-wavelength absorption spectral lines with excellent monochromaticity. This is used for spectral calibration of EUV instruments and equipment, and can generate line spectra with monochromaticity reaching 6 × 10⁻⁶ in the 10–120 nm band. ‑5 This invention provides a high-brightness, tabletop light source with multiple wavelengths. By adjusting the laser power within the range of mW or even 100W, this isotropic, point-like incoherent light source can be easily expanded to an aperture of tens of centimeters, meeting the spectral calibration requirements of various devices and instruments.

Description

Technical Field

[0001] This invention belongs to the field of special light source technology, and in particular relates to a multi-wavelength extreme ultraviolet tabletop light source based on absorption spectral lines. Background Technology

[0002] Extreme ultraviolet (EUV) light sources have wide applications in numerous fields, including wafer and mask quality control equipment in the semiconductor industry, EUV lithography machines, multi-band astronomical instruments, and solar EUV spectroscopic instruments. EUV light source applications can be categorized into three types: imaging calibration, flux calibration, and spectral calibration. These applications are typically implemented using synchrotron radiation sources. However, synchrotron radiation sources, as rare large-scale scientific facilities, are not only expensive and have limited operating time, but also cannot be easily moved to production lines for real-time online operation. High-end equipment and instruments in the EUV band for industrial and scientific research require desktop, high-brightness EUV light sources.

[0003] Laser ablation of target materials generates high-temperature plasma that can emit high-brightness light with tunable wavelength. This laser-driven, tabletop high-brightness light source has been applied to extreme ultraviolet (EUV) lithography machines (UV light sources in the ~13.5nm band) [V. Bakshi, EUV lithography (B), Chap3A.29] and semiconductor metrology equipment (white light sources in the 170nm~2500nm range). Laser-driven tabletop light sources can generate average power of several watts or even hundreds of watts and have an emission volume of tens to hundreds of micrometers, which can basically meet the requirements of imaging calibration and flux calibration.

[0004] However, in the extreme ultraviolet (EUV) band of 10–120 nm, the spectral monochromaticity of laser-driven benchtop light sources is very poor. Taking the EUV lithography light source in the 13.5 nm band as an example, the best monochromaticity achieved so far is only 4% [Versolato et al, PSST 28, 083001 (2019); Nishihara et al, PoP 15, 056708 (2008), Proc. SPIE6921, 69210Y (2008).]. This poor monochromaticity cannot meet the requirements of spectral calibration. For example, in the research of solar EUV spectroscopic detection instruments, wavelength and spectral resolution calibration of spectrometers with spectral resolutions of 500–4000 nm is required. This requires the spectrometer to cover a spectral range with multiple line spectra, and the monochromaticity of each line spectra must be better than 0.2%–0.025%. Electrically excited xenon lamps, mercury lamps, halogen lamps, and electron beam-excited X-ray tubes can only cover the 115–2000 nm and 0.01–0.4 nm wavelength ranges, and cannot cover the 10–120 nm extreme ultraviolet (EUV) band. Therefore, there is currently no desktop spectral calibration light source that can be used for the 10–120 nm EUV band. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-wavelength extreme ultraviolet tabletop light source based on absorption spectral lines, which can produce line spectrum monochromaticity of 6×10⁻⁶ in the 10–120 nm wavelength range. -5 A high-brightness, tabletop light source with multiple wavelengths is used for spectral calibration of extreme ultraviolet instruments, solving the problems mentioned in the background technology.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] For high-power laser alpha ablation of high atomic number target materials, shorter wavelengths are preferred, such as 532 nm, 351 nm, or even 266 nm, but generally 1064 nm is sufficient. The intensity of the high-power laser alpha should be close to 1 × 10⁻⁶. 13 W / cm 2 Generally, it should not be lower than 1×10 10 W / cm 2 Shorter wavelengths of extreme ultraviolet (EUV) light require higher laser intensity; otherwise, the luminous efficiency of the EUV band will decrease drastically. Laser pulse widths longer than 1 ns, such as 1–10 ns, are more suitable. Shorter laser pulse widths, such as less than 0.2 ns, will lead to a decrease in the luminous efficiency of EUV light.

[0008] The type of neutral or ionized gas that produces absorption lines is selected based on the wavelength range required for spectral calibration. Inert gases, single-component gases, or compound gases can basically meet the spectral calibration requirements in the extreme ultraviolet band of 10–120 nm.

[0009] The spectral monochromaticity of a single spectral line can be found in the standard atomic and molecular database [Kramida A, Ralchenko Yu, Reader J, NIST ASD Team. NIST atomic spectra database (ver. 5.11). Gaithersburg, MD: National Institute of Standards and Technology; 2023, [Online]. Available: https: / / physics.nist.gov / asd [2024, January 31]; Phys. Rev. Lett. 69, 1171 (1992); Phys. Rev. Lett. 77, 3086 (1006); Rev. Sci. Instruments 63, 80 (1992); Chin. Phys. B 24, 123401 (2015); Phys. Rev. A 71,064701 (2005)]. Typically, the monochromaticity of a single absorption line can reach 6 × 10⁻⁶. -5 When the spectral resolution of the calibrated spectrometer is better than 150, it can distinguish two adjacent absorption lines. The monochromaticity of a single spectral line and the spacing between adjacent spectral lines can meet the spectral calibration requirements of common equipment with spectral resolutions of 500 to 4000.

[0010] For the vast majority of applications, the absorption spectrum of neutral gases is sufficient. However, in very specific cases, such as instruments measuring parameters in semiconductor manufacturing and celestial nebulae, spectral calibration using the absorption spectrum of ionized gases is necessary. In these situations, a separate high-power laser (be) can be used to ionize the neutral gas, or laser ablation of a solid or liquid target can generate ionized gas. Alternatively, electrodes can be placed on either side of the neutral gas, and a DC high voltage, radio frequency source, or microwave source can be applied to the electrodes to ionize the gas.

[0011] For spectral calibration requirements with a spectral resolution difference greater than 150, the laser that generates continuous spectrum emission in the extreme ultraviolet band can be turned off, and only the emission line spectrum of the ionized gas can be used for spectral calibration.

[0012] This invention relates to a multi-wavelength extreme ultraviolet (EUV) tabletop light source based on absorption spectral lines. It includes an optical element that establishes a beam path between a high-power laser a and a target location; continuously releasing the high-power laser a toward the target location to drive a high-atomic-number solid target at the target location to generate continuous spectrum emission in the EUV band; wherein the high-atomic-number solid target can be metals such as tungsten, tantalum, mercury, lead, uranium, samarium, and molybdenum, liquid metals, alloys, or compounds, but the high-atomic-number elements must constitute the majority of the alloy and compound to avoid a distinct line emission spectrum in the EUV band, ensuring that the laser-driven target point produces a smooth continuous spectrum.

[0013] The continuous spectrum emission in the extreme ultraviolet band is collected by a first and a second collecting mirror with near-grazing incidence. A beam of light used for spectral calibration is focused by the first collecting mirror into a first cavity channel containing a gas that produces absorption lines. The beam of light with absorption lines after passing through the first cavity channel of the gas is collected by a third collecting mirror with near-grazing incidence to the light exit port. A focal point or parallel light is formed at the light exit port for spectral calibration. Whether a focal point or parallel light is formed depends on the parameter requirements of the downstream instrument equipment.

[0014] Another beam of light, collected by the second collecting mirror, is split by a grating in the second cavity channel and then enters a detector for recording the spectrum. This beam is used to measure the spectrum of continuous spectrum emission in real time and to quantitatively give the absolute intensity of continuous spectrum emission.

[0015] The cavity space of the vacuum system is established by the beam path from the high-power laser a entering the target position to the light outlet and the beam path to the detector.

[0016] Furthermore, the optical elements that sequentially form the beam path include a first reflector, a first vacuum window, a first focusing mirror, and a second reflector. The beam emitted by the high-power laser a is introduced into the first vacuum window located in the cavity space by adjusting the position of the first reflector, and then the beam is focused by the first focusing mirror and then hit the target position by the second reflector.

[0017] Furthermore, the target location is a rotating target situated within the chamber space. The rotating target includes a rotating mechanism and a high atomic number solid target fixed to the rotating mechanism. The rotating mechanism can be a rotating stage. Placing the high atomic number solid target on the rotating stage ensures that each laser ablation site contains unablated new material, increasing the stability of the light source. Additionally, the high-speed rotating target can fling neutral target fragments away from the first and second collection mirrors of the extreme ultraviolet light, the laser focusing mirror, and the reflecting mirror, thereby extending the lifespan of these mirrors.

[0018] Furthermore, the continuous spectrum emission wavelength in the extreme ultraviolet band is in the range of 266 nm to 1064 nm; the laser intensity is 1 × 10⁻⁶. 10 W / cm 2 ~1×10 13 W / cm 2 .

[0019] Furthermore, the gas that produces the absorption lines includes a neutral gas or an ionized gas.

[0020] Furthermore, the gas includes ionized gas generated by ionizing neutral gas or ionized gas generated by laser ablation of a solid or liquid target.

[0021] Furthermore, the generation of the ionized gas by ionizing the neutral gas includes a high-power laser b, which is released toward the channel region where the neutral gas is located.

[0022] Furthermore, the beam path between the high-power laser b and the ionized gas also includes a third reflecting mirror and a second focusing mirror in sequence; the laser emitted by the high-power laser b is focused by the third reflecting mirror and then by the second focusing mirror to ionize the neutral gas and generate ionized gas.

[0023] Furthermore, the cavity space of the vacuum system where the beam path of the high-power laser a enters the target position is located; because the extreme ultraviolet band is strongly absorbed in the atmosphere, all components except for high-power laser a and high-power laser b are placed in the vacuum system, with a vacuum degree of at least 10. -3 Pa, the vacuum level at the light outlet depends on the requirements of the equipment or instrument to be calibrated.

[0024] Furthermore, the cavity space between the target location and the optical element is provided with an isolation layer for protection, and the isolation layer also includes an extreme ultraviolet filter to block target debris contamination and / or an airflow assembly to suppress target debris contamination.

[0025] In addition to the above, the chamber of the laser ablation rotating target can also be isolated from other optical components through an isolation layer. Specifically, it also includes a magnet to suppress target debris contamination, a rotating baffle to block target debris, a high-voltage power supply to generate ionized gas, a radio frequency source, a microwave source, and electrodes.

[0026] The present invention has the following beneficial effects:

[0027] 1. High-power lasers are used to ablate high atomic number target materials to generate continuous spectrum emission in the extreme ultraviolet band. This emission then passes through neutral or ionized gas to produce highly monochromatic, multi-wavelength absorption lines, with each line achieving a monochromaticity of 6 × 10⁻⁶. -5The spacing between adjacent spectral lines corresponds to a spectral resolution of around 150, which meets the spectral calibration requirements of common devices with spectral resolutions of 500 to 4000.

[0028] 2. This invention uses a high-power laser to drive the generation of a spectral calibration light source in the extreme ultraviolet band. Compared with large synchrotron radiation light sources, this light source equipment is small in size and light in weight, and can be made into small instruments that can be integrated into production lines and other instruments.

[0029] 3. High-power laser-driven light sources generate extreme ultraviolet (EUV) wavelengths. The power in the 10–120 nm EUV band can be adjusted within a wide range from mW to 100W by adjusting the laser power, which can meet the power requirements of various sensitivity devices and instruments.

[0030] 4. High-power laser-driven light sources can generate extreme ultraviolet light in the 10–120 nm band with an instantaneous power of up to 10 MW. The width of each extreme ultraviolet light pulse is comparable to that of the laser pulse, ranging from 1 to 10 ns or even shorter. Such short-pulse and instantaneously high-power light sources can be used for nanosecond time-resolved transient spectral calibration.

[0031] 5. The extreme ultraviolet spectral calibration light source generated by high-power laser driving is an incoherent point source. The size of the light source can be continuously adjusted from tens of micrometers to tens of centimeters within a very short distance of tens of centimeters using a collecting mirror. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a system diagram of the multi-wavelength extreme ultraviolet tabletop light source based on absorption spectral lines in Example 1;

[0034] Figure 2 The present invention provides the results of calibrating a spectrometer using the absorption lines of neutral helium gas.

[0035] Figure 3 This is a system diagram of the multi-wavelength extreme ultraviolet tabletop light source based on absorption spectral lines in Example 2;

[0036] Figure 4 The present invention provides the results of calibrating a spectrometer using the absorption lines of fluorine-ionized gas.

[0037] Figure 5This is a system diagram of neutral helium gas with an isolation layer in Example 5;

[0038] Figure 6 This is a system diagram of fluorine-ionized gas with an isolation layer in Example 5;

[0039] Figure 7 This is a system diagram of the airflow assembly with an isolation layer and an extreme ultraviolet filter using neutral helium gas in Example 6;

[0040] Figure 8 This is a system diagram of the airflow assembly with an isolation layer and an extreme ultraviolet filter utilizing fluorine ionized gas in Example 6;

[0041] The attached diagram lists the components represented by each number as follows:

[0042] 1-High-power laser a, 2-High-power laser b, 3a-First reflecting mirror, 3b-Second reflecting mirror, 3c-Third reflecting mirror, 4-First vacuum window, 5a-First focusing mirror, 5b-Second focusing mirror, 6-Rotating target, 7-Target position, 8-First collecting mirror, 9a-Neutral gas, 9b-Ionized gas, 10-Third collecting mirror, 11-Light outlet, 12-Second collecting mirror, 13-Grate, 14-Detector, 15-Vacuum system, 16-Isolation layer, 17a-First extreme ultraviolet filter, 17b-Second extreme ultraviolet filter, 18-Second vacuum window, 19-Airflow assembly. Detailed Implementation

[0043] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] This invention uses a high-power laser to drive a high atomic number target material to generate a continuous spectrum high-brightness light source, which is then absorbed by neutral gas 9a or ionized gas 9b to generate multi-wavelength absorption lines with extremely high monochromaticity for spectral calibration of extreme ultraviolet instruments and equipment.

[0045] Because the extreme ultraviolet (EUV) band is strongly absorbed in the atmosphere, all components except for high-power lasers a1 and b2 are placed inside the vacuum system 15, meaning the EUV light generation and transmission path is evacuated to a vacuum level of at least 10. -3 Pa, the vacuum level of the light outlet 11 is determined according to the requirements of the equipment or instrument to be calibrated. Example

[0046] See Figure 1A multi-wavelength extreme ultraviolet tabletop light source based on absorption spectral lines includes a high-power laser a1, a target position 7, a light outlet 11, and a detector 14. The cavity space of the vacuum system 15 is established by the beam path from the high-power laser a1 entering the target position 7 to the light outlet 11 and the detector 14.

[0047] In this embodiment, the vacuum system 15 evacuates the chamber space containing the extreme ultraviolet light generation and transmission path to 10°C. -3 Under a vacuum state of Pa, the vacuum degree of the light outlet 11 is 10. -5 Pa is a vacuum state.

[0048] An optical element that forms a beam path is set between the high-power laser a1 and the target position 7. By continuously releasing the high-power laser a1 toward the target position 7, the high atomic number solid target on the target position 7 is driven to produce continuous spectrum emission in the extreme ultraviolet band.

[0049] The optical elements that form the beam path in sequence include a first reflecting mirror 3a, a first vacuum window 4, a first focusing mirror 5a, and a second reflecting mirror 3b. The beam emitted by the high-power laser a1 is introduced into the first vacuum window 4 located in the cavity space by adjusting the position of the first reflecting mirror 3a. The beam is then focused by the first focusing mirror 5a and then hit the target position 7 by the second reflecting mirror 3b.

[0050] Among them, the high-power laser a1 uses a nanosecond laser, and the laser wavelength of the high-power laser a1 for ablating high atomic number solid targets is in the range of 266nm to 1064nm; the laser intensity is 1×10 10 W / cm 2 ~1×10 13 W / cm 2 Within the range of this embodiment, the nanosecond laser with laser parameters of 2J single pulse energy, 10ns laser pulse width, 532nm wavelength, and 10Hz repetition frequency is reflected by the first reflecting mirror 3a, enters the vacuum system from the atmospheric environment through the first vacuum window 4, is focused by the first focusing mirror 5a, and after being reflected by the second reflecting mirror 3b, it ablates the rotating tungsten target with a 50-micron focused focal spot to produce continuous spectrum emission in the extreme ultraviolet band of 10-120nm.

[0051] The continuous spectrum emission in the extreme ultraviolet band is collected by the first collecting mirror 8 and the second collecting mirror 12 with near-grazing incidence. Among them, one beam of light used for spectral calibration is focused by the first collecting mirror 8 into a first cavity channel containing a neutral gas 9a that produces absorption lines. The light beam with absorption lines after passing through the first cavity channel of neutral gas 9a is collected by a third collecting mirror 10 with near-grazing incidence to the light exit port 11. A focal point or parallel light is formed at the light exit port 11 for spectral calibration. Whether a focal point or parallel light is generated depends on the parameter requirements of the downstream instrument equipment.

[0052] Another beam of light is collected by the second collecting mirror 12 and then split by the second cavity channel before entering the detector 14 for recording the spectrum. A grating 13 is provided in the second cavity channel to split the collected light. This beam of light is used to measure the spectrum of continuous spectrum emission in real time and to quantitatively give the absolute intensity of continuous spectrum emission.

[0053] Both the first collecting mirror 8 and the second collecting mirror 12 are metal collecting mirrors.

[0054] In this embodiment, the laser power is 20W, the generated extreme ultraviolet continuous spectrum emission power is 2W, and a pair of grazing incident collection mirrors at an 80-degree angle are used to collect the continuous spectrum emission. The extreme ultraviolet light carrying absorption lines reaching the light outlet has a wavelength range of 10-120nm and a power of 2mW.

[0055] See Figure 2 The absorption spectrum measured by a certain extreme ultraviolet spectrometer to be calibrated is obtained when using neutral helium gas. The original monochromaticity of the measured spectrum is close to 1 / 18000. From the spectral broadening, the spectral resolution of this extreme ultraviolet spectrometer to be calibrated is 866. Example

[0056] See Figure 3 A multi-wavelength extreme ultraviolet tabletop light source based on absorption spectral lines includes a high-power laser a1, a target position 7, a light outlet 11, and a detector 14. The cavity space of the vacuum system 15 is established by the beam path from the high-power laser a1 entering the target position 7 to the light outlet 11 and the detector 14.

[0057] In this embodiment, the vacuum system 15 evacuates the chamber space containing the extreme ultraviolet light generation and transmission path to 10°C. -3 Under a vacuum state of Pa, the vacuum degree of the light outlet 11 is 10. -4 Pa is a vacuum state.

[0058] An optical element forming a beam path is provided between the high-power laser a1 and the target position 7. The high-power laser a1 is continuously released toward the target position 7, driving the high atomic number solid target at the target position 7 to produce continuous spectrum emission in the extreme ultraviolet band. The optical element forming the beam path in sequence includes a first reflector 3a, a first vacuum window 4, a first focusing mirror 5a, and a second reflector 3b. The beam emitted by the high-power laser a1 is introduced into the first vacuum window 4 located in the cavity space by adjusting the position of the first reflector 3a. Then, the beam is focused by the first focusing mirror 5a and then hit the target position 7 by the second reflecting mirror 3b.

[0059] Among them, the high-power laser a1 uses a nanosecond laser, and the laser wavelength of the high-power laser a1 for ablating high atomic number solid targets is in the range of 266nm to 1064nm; the laser intensity is 1×10 10 W / cm 2 ~1×10 13 W / cm 2 In this embodiment, the nanosecond laser with laser parameters of 1J single pulse energy, 1ns laser pulse width, 351nm wavelength, and 1kHz repetition frequency is reflected by the first reflecting mirror 3a, enters the vacuum system from the atmospheric environment through the first vacuum window 4, is focused by the first focusing mirror 5a, and is reflected by the second reflecting mirror 3b. The laser then ablates the rotating tungsten target with a 50-micron focused spot to produce continuous spectrum emission in the extreme ultraviolet band of 10-120nm.

[0060] The continuous spectrum emission in the extreme ultraviolet band is collected by the first collecting mirror 8 and the second collecting mirror 12 with near-grazing incidence. Among them, one beam of light used for spectral calibration is focused by the first collecting mirror 8 into a first cavity channel containing an ionized gas 9b that generates absorption lines. The beam of light with absorption lines after passing through the first cavity channel of the ionized gas 9b is collected by a third collecting mirror 10 with near-grazing incidence to the light exit port 11. A focal point or parallel light is formed at the light exit port 11 for spectral calibration. Whether a focal point or parallel light is generated depends on the parameter requirements of the downstream instrument equipment.

[0061] Another beam of light, collected by the second collecting mirror 12, is split by a second cavity channel with a grating 13 and then enters the detector 14 for recording the spectrum. This beam of light is used to measure the spectrum of continuous spectrum emission in real time and to quantitatively give the absolute intensity of continuous spectrum emission.

[0062] In this embodiment, the laser power is 1kW, the generated continuous spectrum emission power is 100W, and a pair of grazing incidence collecting mirrors at an 80-degree angle are used to collect the continuous spectrum emission. The extreme ultraviolet light carrying absorption lines that reaches the light outlet covers a wavelength of 10-120nm and has a power of 2.5W.

[0063] See Figure 4 This is the absorption spectrum of an ionized gas measured by an extreme ultraviolet spectrometer to be calibrated. Here, a nylon target is ablated using a laser to generate ionized fluorine gas. The density of the ionized gas is 1 × 10⁻⁶. 19 cm -3 The size is ~1mm. From the figure, it can be found that fluorine ionized gas has several known absorption lines in the 53-63eV region. The wavelength position and spectral resolution of this extreme ultraviolet spectrometer were determined using these known absorption lines.

[0064] See Figure 3 The gas that generates the absorption spectral line also includes ionized gas 9b generated by ionizing neutral gas 9a. The generation of ionized gas 9b includes a high-power laser b2, which is released towards the channel region where neutral gas 9a is located. The beam path between the high-power laser b2 and the ionized gas 9b also includes a third reflecting mirror 3c and a second focusing mirror 5b. The laser emitted by the high-power laser b2 is focused by the third reflecting mirror 3c and then by the second focusing mirror 5b to ionize neutral gas 9a and generate ionized gas 9b.

[0065] Ionized gas 9b is generated by ablation of a solid or gas target using another nanosecond laser with 1J single-pulse energy, 10ns laser pulse width, 1064nm wavelength, 1000Hz repetition frequency, and 100-micron focused focal spot.

[0066] Gases that generate absorption lines can also be ionized gas 9b generated by laser ablation of solid or liquid targets; or electrodes can be placed on both sides of neutral gas 9a, and DC high voltage, radio frequency source, microwave source, etc. can be applied to the electrodes to ionize neutral gas 9a.

[0067] The type of neutral or ionized gas that produces absorption lines is selected based on the wavelength range required for spectral calibration. Inert gases, single-component gases, or compound gases can basically meet the spectral calibration requirements in the extreme ultraviolet band of 10–120 nm.

[0068] See Figure 5 or Figure 6 An isolation layer 16 is provided in the cavity space between the second reflector 3b and the first collecting mirror 8 and the second collecting mirror 12 for protection. During the laser ablation of the rotating target, tiny particles or target fragments will be generated, which may damage the optical components in the cavity space. Therefore, the isolation layer 16, after leaving a channel for the beam to pass through, can block some of the particles from damaging the first collecting mirror 8 and the second collecting mirror 12, thereby improving the service life of the components.

[0069] See Figure 7 or Figure 8A protective isolation layer 16 is provided in the cavity space between the target position 7 of the laser ablation rotating target and the optical element. This isolation layer 16 prevents particulate matter from damaging the optical devices such as the first reflector 3a, the first vacuum window 4, the first focusing lens 5a, the second reflector 3b, the first collecting lens 8, and the second collecting lens 12.

[0070] As shown in the figure, the laser beam path is as follows: the laser generated by the high-power laser a1 passes through the first reflector 3a, the first vacuum window 4, the first focusing lens 5a to the second reflector 3b, and then through the second reflector 3b to the target position 7. A second vacuum window 18 is also fixed on the isolation layer 16. The laser beam passes through the second vacuum window 18 to the target position 7.

[0071] The continuous spectrum of extreme ultraviolet light generated by the high atomic number solid target on the rotating target 6 enters the first collecting mirror 8 and the second collecting mirror 12 through the channel on the isolation layer 16. A first extreme ultraviolet filter 17a is fixed on one side of the isolation layer 16 to block target debris contamination. An airflow assembly 19 for suppressing target debris contamination is provided on the other side of the isolation layer 16. The airflow assembly 19 is a trachet fixed in the cavity, with the outlet of the trachet facing the channel. The airflow blown out by the trachet blows the target debris away from the area where the isolation layer 16 is located, preventing the target debris from entering the cavity where the optical device is located.

[0072] While the gas is being blown in, the generated gas is extracted by the vacuum system 15, allowing the vacuum level in the chamber region where the rotating target 6 is located to be relatively low. In this embodiment, the outlet pressure of the airflow assembly 19 is ~100 Pa, the gas used is hydrogen, and the outlet diameter is ~1 mm.

[0073] In addition to the above, the chamber area where the laser ablation rotating target is located is isolated from other parts, and specifically includes magnets to suppress target debris contamination, rotating baffles to block target debris, high-voltage power supply to generate ionized gas, radio frequency source, microwave source and electrodes, etc.

[0074] Meanwhile, a second ultraviolet (EUV) filter 17b is also provided in a first cavity channel containing a neutral gas that generates absorption lines, which is focused by the first collecting mirror 8 through one of the beams used for spectral calibration. The neutral gas 9a or ionized gas 9b is formed into a closed space within the first cavity channel by the second UV filter 17b. On the one hand, the neutral gas 9a or ionized gas 9b is confined by the second UV filter 17b to prevent it from escaping into the external space. On the other hand, the second UV filter 17b suppresses target fragment contamination.

[0075] Among them, the first extreme ultraviolet filter 17a and the second extreme ultraviolet filter 17b are aluminum, zirconia, silicon or carbon nanotube films with a thickness of 50-200nm.

[0076] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A multi-wavelength extreme ultraviolet tabletop light source based on absorption spectral lines, comprising an optical element for establishing a beam path between a high-power laser a (1) and a target position (7); characterized in that: The high-power laser a (1) is continuously released toward the target position (7) to drive the high atomic number solid target at the target position (7) to produce continuous spectrum emission in the extreme ultraviolet band; The continuous spectrum emission that produces the extreme ultraviolet band is collected by the first collecting mirror (8) and the second collecting mirror (12) that are near-grazing incident; Among them, one beam of light used for spectral calibration is focused by the first collecting mirror (8) into a first cavity channel containing a gas that generates absorption lines, and the beam of light with absorption lines after passing through the first cavity channel of the gas is collected by a near-grazing third collecting mirror (10) to the light outlet (11). The gas that generates the absorption lines includes a neutral gas (9a) or an ionized gas (9b) generated by ionizing a neutral gas (9a), or an ionized gas (9b) generated by laser ablation of a solid or liquid target. Among them, the light collected by the second collecting mirror (12) is split by a grating (13) in the second cavity channel and then enters the detector (14) used to record the spectrum. The beam path from the high-power laser a (1) to the target position (7) to the light outlet (11) and the beam path to the detector (14) both establish a chamber space with a vacuum system (15).

2. The multi-wavelength extreme ultraviolet tabletop light source based on absorption spectral lines as described in claim 1, characterized in that, The optical elements that form the beam path sequentially include a first reflector (3a), a first vacuum window (4), a first focusing mirror (5a), and a second reflector (3b). The beam emitted by the high-power laser a (1) is introduced into the first vacuum window (4) located in the cavity space through the first reflector (3a), and then the beam is focused by the first focusing mirror (5a) and then hit the target position (7) through the second reflector (3b).

3. The multi-wavelength extreme ultraviolet tabletop light source based on absorption spectral lines as described in claim 1, characterized in that, The target position (7) is a rotating target (6) located in the chamber space. The rotating target (6) includes a rotating mechanism and a high atomic number solid target fixed in the rotating mechanism.

4. The multi-wavelength extreme ultraviolet tabletop light source based on absorption spectral lines as described in claim 1, characterized in that, The continuous spectrum emission wavelength in the extreme ultraviolet band is in the range of 266 nm to 1064 nm; the laser intensity is 1 × 10⁻⁶. 10 W / cm 2 ~1×10 13 W / cm 2 .

5. A multi-wavelength extreme ultraviolet tabletop light source based on absorption spectral lines as described in any one of claims 1, characterized in that, The vacuum level of the chamber space is at least 10. -3 Pa.

6. The multi-wavelength extreme ultraviolet tabletop light source based on absorption spectral lines as described in claim 1, characterized in that, The cavity space between the target location (7) and the optical element is provided with an isolation layer (16) for protection. The isolation layer (16) also includes an extreme ultraviolet filter (17a) to block target debris contamination and / or an airflow assembly (19) to suppress target debris contamination.

7. The multi-wavelength extreme ultraviolet tabletop light source based on absorption spectral lines as described in claim 1, characterized in that, The ionized gas (9b) is generated by ionizing neutral gas (9a) and includes a high-power laser b (2), which is released toward the channel region where the neutral gas (9a) is located.

8. The multi-wavelength extreme ultraviolet tabletop light source based on absorption spectral lines as described in claim 1, characterized in that, The beam path between the high-power laser b (2) and the ionized gas (9b) also includes a third reflecting mirror (3c) and a second focusing mirror (5b); the laser emitted by the high-power laser b (2) is focused by the third reflecting mirror (3c) and then by the second focusing mirror (5b) to ionize the neutral gas (9a) to generate ionized gas (9b).

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