Laser plasma extreme ultraviolet light source device and extreme ultraviolet light generation method thereof

Abstract

The invention discloses a laser plasma extreme ultraviolet light source device and an extreme ultraviolet light generating method thereof. The device comprises a liquid drop generator, a liquid drop generator, a liquid drop generator and an extreme ultraviolet light source, wherein the liquid drop generator is used for generating target micro-drops; the laser system is used for generating pre-pulse laser and main pulse vortex laser; the light beam focusing device is used for converging the laser beams output by the laser system onto the target microdroplet to generate high-temperature plasma; the extreme ultraviolet collecting device is used for collecting extreme ultraviolet light emitted by the plasma and converging the extreme ultraviolet light to the output window; the control signal synchronization device is used for controlling light emitting time of the laser system; the vacuum chamber is used for providing an environment for generating a plasma light source. Main pulse vortex laser generated by the laser system is used for heating the target microdroplet, so that the electron density of the plasma is improved, and the output intensity of extreme ultraviolet radiation is improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, specifically to a laser plasma extreme ultraviolet light source device and a method for generating extreme ultraviolet light. Background Technology

[0002] With the continuous development of the semiconductor industry, integrated circuits have become the core foundation of modern technology. In integrated circuit manufacturing processes, photolithography, as a key process, has undergone dozens of technological innovations and has now evolved to the extreme ultraviolet (EUV) lithography stage. Achieving EUV industrialization requires overcoming three core light source indicators: high stability, high cleanliness, and high-power radiation output. Currently, artificial EUV light sources mainly rely on four technical paths: synchrotron radiation sources, discharge plasma (DPP), laser plasma (LPP), and laser-assisted discharge plasma (LDP). Among these, laser plasma sources have become the most suitable solution for industrialization due to their significant advantages such as compact structure, ultra-high brightness, and low debris contamination. Its working principle involves bombarding a tin-based liquid droplet target with a high-power pulsed laser, instantly generating highly ionized plasma at millions of degrees Celsius. During this process, excited-state electrons undergo energy level transitions and release 13.5nm characteristic radiation, which is precisely collected by Mo / Si multilayer film mirrors to form a light source that meets the requirements of photolithography.

[0003] In LPP light sources, the output power is determined by the plasma luminescence efficiency and collection efficiency, with the luminescence efficiency being jointly determined by parameters such as plasma electron density and electron temperature. In existing technologies, researchers have controlled the plasma electron density by altering the target material morphology (droplets, aerosols, etc.) and topography (nanopores, nanotubes, microgrooves, etc.) or by changing the laser action mode (parallel dual-laser irradiation to generate collisional plasma). These methods allow for more complete interaction between the laser and the target material, increasing the extreme ultraviolet radiation yield. Regarding changing the target material morphology, targets with complex microstructures exhibit altered or lost surface microstructures after interaction with high-power lasers. Regarding changing the laser action mode, the optical system for dual-parallel laser irradiation of the target material is complex. The proposed solution using a vortex laser as the driving laser cleverly avoids the complexity of dual-parallel laser systems and can stably achieve a focusing effect on the plasma electron density, improving the light source's radiation efficiency and output power.

[0004] In conclusion, the invention of a method for increasing the intensity of extreme ultraviolet radiation using vortex lasers is of great significance. Summary of the Invention

[0005] The purpose of this application is to provide a method and light source device for improving extreme ultraviolet radiation intensity using a vortex laser, thereby solving the problems existing in the above-mentioned technical background. This method utilizes a vortex laser to bombard a target material, causing ionization of the target surface to generate plasma and emit 13.5 nm extreme ultraviolet radiation. The generated laser plasma is modulated through the ring-shaped light field of the vortex laser, changing the electron temperature density distribution and improving the plasma radiation efficiency, thus solving the problems of low efficiency and insufficient power in traditional light sources.

[0006] The first aspect of this application discloses a laser-plasma extreme ultraviolet light source device, the device comprising:

[0007] Droplet generator, used to produce tin microdroplets;

[0008] Laser system used to generate pre-pulse and main pulse vortex lasers.

[0009] A beam focusing device is used to focus the laser generated by a laser system onto tin microdroplets to produce high-temperature plasma.

[0010] An extreme ultraviolet light collection device is used to collect extreme ultraviolet light emitted by plasma and focus the extreme ultraviolet light onto the output window;

[0011] A control signal synchronization device is used to synchronize laser pulses to ensure that the laser pulses can accurately bombard the target droplets.

[0012] A vacuum chamber is used to provide an environment for generating high-temperature plasma.

[0013] A second aspect of this application discloses a method for generating extreme ultraviolet light using a laser-plasma extreme ultraviolet light source device. The device includes a laser system, a droplet generator, a beam focusing device, and an extreme ultraviolet light collecting device. The method includes:

[0014] Tin microdroplets are generated using a droplet generator;

[0015] The laser system generates pre-pulse and main pulse vortex lasers for target practice.

[0016] The generated laser beam is focused onto the surface of tin microdroplets using a beam focusing device to produce high-temperature plasma;

[0017] Extreme ultraviolet light emitted from the plasma is collected by an extreme ultraviolet light collection device and focused onto the output window.

[0018] The laser plasma extreme ultraviolet light source system and the method for generating extreme ultraviolet light described in the first and second aspects above have the following beneficial effects:

[0019] By employing a solid-state laser as the driving laser, high-repetition-rate, high-power lasers can be generated relatively easily. The vortex laser output by the laser system, as the main pulse, can create a focusing effect on the plasma, optimize the plasma electron density distribution, enhance the emission intensity of extreme ultraviolet light, and increase the output power of the light source. The solution proposed in this application can realize a laser plasma light source device with a vortex laser as the main pulse laser through simple modifications to existing light source generating devices, facilitating the upgrading of the light source process. Furthermore, by replacing the target material of the light source with gadolinium, the solution described in this invention can serve as an ultra-extreme ultraviolet light source with an output wavelength of 6.76 nm. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of the application and are used to explain the application, but do not constitute an undue limitation of the application. In the drawings:

[0021] Figure 1 This is a schematic diagram of a laser plasma extreme ultraviolet light source device according to an exemplary embodiment of this application;

[0022] Figure 2 For the purposes of this application Figure 1 The diagram shown illustrates the generation of extreme ultraviolet light.

[0023] Figure 3 For the purposes of this application Figure 2 A schematic diagram of a reflective phase plate is shown.

[0024] Figure 4 This is a flowchart illustrating an embodiment of a method for generating extreme ultraviolet light using a laser plasma extreme ultraviolet light source device according to an exemplary embodiment of this application. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, it should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit the scope of this disclosure. It should be understood that the specific embodiments described herein are only intended to provide a further understanding of this application. The illustrative embodiments and their descriptions are used to explain this application and do not constitute an improper limitation of this application. Obviously, the embodiments described in this application are merely some embodiments of the invention, and not all embodiments. Those skilled in the art can make various modifications and variations to this invention without departing from the spirit and scope of the invention. Therefore, if these modifications and variations of the invention fall within the scope of the claims of this invention and their equivalents, the invention also intends to include these modifications and variations.

[0026] It is understood that the terms "first," "second," etc., used in this invention may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0027] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0028] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising,” “including,” or “having,” etc., specify the presence of the stated feature, whole, step, operation, component, part, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof.

[0029] Currently, in the field of high-end semiconductor chip manufacturing, photolithography technology determines the performance level of chips. Due to the continuous miniaturization of chip manufacturing processes, more advanced photolithography technologies require shorter light source wavelengths. Therefore, the importance of extreme ultraviolet (EUV) light sources, one of the core components of next-generation photolithography technology, is becoming increasingly prominent. However, a major factor limiting the development of EUV light source technology is the difficulty in obtaining high-power, high-quality, and long-life EUV light sources.

[0030] A highly efficient and stable extreme ultraviolet (EUV) light source requires high conversion efficiency, which in turn necessitates high optical radiation efficiency from the plasma. However, at the physical level, the light source output is constrained by plasma physical parameters (electron temperature and electron density). Studies have shown that the optical radiation intensity of the plasma is directly proportional to the electron density, while the electron temperature affects the wavelength stability of the light source. Generally, the plasma electron density distribution is jointly determined by the initial morphology of the target material and the incident laser light field distribution. However, controlling the initial morphology of the target material is extremely difficult and challenging to achieve in droplet target light source systems.

[0031] To maximize the output power of the light source and minimize light source debris, this application employs a Laguerre Gaussian beam as the driving laser for the light source device. By controlling the generated laser plasma through the annular light field of the vortex laser, the electron temperature density distribution is altered, thereby improving the plasma radiation efficiency and solving the problems of low efficiency and insufficient power of traditional light sources.

[0032] Based on this, this application proposes an improved laser plasma extreme ultraviolet light source system, see [link to relevant documentation]. Figure 1 As shown. The laser plasma extreme ultraviolet light source system includes a laser system 1, a beam focusing device 2, a control signal synchronization device 3, a droplet generator 4, an extreme ultraviolet light collecting device 5, and a vacuum chamber 6.

[0033] In practice, the droplet generator 4 generates tin microdroplets of a certain size; the laser system 1 generates laser light, which is focused by the beam focusing device 2 and then irradiates the target microdroplet to generate plasma; the extreme ultraviolet light collection device 5 collects the extreme ultraviolet light emitted by the plasma and focuses it onto the output window.

[0034] The laser system 1 outputs a vortex laser to heat the target droplets and generate plasma. Compared to the CO2 lasers used in existing technologies, the laser system 1 uses a solid-state laser as the laser source. The extreme ultraviolet light collection device 5 is a multilayer film mirror designed to improve the reflectivity at the core wavelength.

[0035] It is worth noting that, considering the high photon energy characteristics of extreme ultraviolet light, it is extremely easy for any substance to absorb it; therefore, the light source is generated in vacuum chamber 6. The vacuum level is maintained at 10. -3 Below Pa.

[0036] Compared with existing dual-pulse laser plasma technology, this application uses a solid-state laser as the laser source, which can easily achieve high repetition rate and high power output. Furthermore, by simply modifying the optical path of existing dual-pulse technology, a laser plasma source device using a vortex laser as the driving laser can be easily obtained. This allows for relatively convenient upgrading of the process technology.

[0037] In some embodiments, see Figure 2 The laser system 1 includes a laser 11, a laser 12, a vortex beam generating device 14, and a beam combiner 13. The laser pulse output by laser 11 is a pre-pulse, and the laser pulse output by laser 12 is the main pulse. The main pulse laser is incident on the vortex beam generating device 14 and then combined with the pre-pulse laser in the beam combiner 13. The vortex beam generating device 14 is composed of a reflective phase plate. The beam combiner 13 is composed of dichroic mirrors. The control signal synchronization device 3 outputs a TTL level signal to control lasers 11 and 12.

[0038] In practical implementation, the control signal synchronization device 3 outputs two pulses with a certain delay between them. These two pulses control the emission timing of lasers 11 and 12, respectively. Each time, the main pulse Gaussian laser output by laser 12 passes through the reflective phase plate 14, generating a ring-shaped Laguerre-Gaussian vortex laser. After being combined with a pre-pulse by the beam combiner 13, the main pulse laser is focused onto the tin droplet by the beam focusing device 2. The lower-energy pre-pulse interacts with the tin droplet first, shaping the approximately spherical droplet into a flat disk or mist shape. Subsequently, the main pulse heats the shaped tin droplet, forming a high-temperature plasma. Because the main pulse's light field distribution is ring-shaped, the plasma converges towards the center due to the influence of the ring-shaped light field, increasing the plasma electron density in the central region and enhancing the output of extreme ultraviolet radiation.

[0039] In some embodiments, the reflective phase plate in the vortex laser generating device 14 can provide a spiral phase of 0–2π to the Gaussian incident laser to generate a vortex laser. The reflective phase plate is made of quartz material and has 32 steps, each step carrying a phase range of 0–2π. The phase plate dimensions are 120 mm × 80 mm × 20 mm. See also Figure 3 As shown. The dichroic mirror in the beam combining device 13 is made of fused silica material with a coating on its surface, which makes its transmittance for 532nm laser ≥95% and its reflectance for 1064nm laser ≥99% when incident at 45°.

[0040] Furthermore, under the phase modulation conditions provided by this phase plate, after the Gaussian laser is incident on the center of the phase plate and reflected, the laser beam receives phase modulation from the phase plate and carries a spiral phase of 0 to 2π in the frequency domain. At this time, the emitted laser beam appears as a vortex beam with a topological charge l = 1.

[0041] In some embodiments, laser 1 in the laser system mentioned in this application may be an Nd:YAG solid-state laser with an output wavelength of 532 nm; laser 2 may be an Nd:YAG laser with an output wavelength of 1064 nm.

[0042] In practical implementation, the laser pulses generated by the laser system can be enhanced by increasing the pump light energy, thereby increasing the output laser pulse energy. Vortex lasers with different topological charges can be achieved by replacing the reflective phase plate carrying different phase information. Furthermore, using a reflective phase plate can avoid damage to components caused by high-intensity laser energy.

[0043] It should be noted that the laser plasma extreme ultraviolet light source device can also have a camera (not shown in the figure) to monitor the droplets, which can provide real-time feedback on the ejection of the microdroplets and transmit the signal to the control signal synchronization device 3. Subsequently, the control signal synchronization device outputs TTL signals with different delays to control the laser 11 and the laser 12, so as to achieve stable and precise laser irradiation on the microdroplets.

[0044] Corresponding to the above-mentioned laser plasma extreme ultraviolet light source device example, this application also proposes an embodiment of an extreme ultraviolet light generation method for a laser plasma extreme ultraviolet light source device.

[0045] Figure 4 The diagram shown is a flowchart illustrating an embodiment of a method for generating extreme ultraviolet light using a laser plasma extreme ultraviolet light source device according to an exemplary embodiment. In the above... Figure 1 , Figure 2 and Figure 3 Based on the illustrated embodiment, the method for generating extreme ultraviolet light using a laser plasma extreme ultraviolet light source device includes the following steps:

[0046] Step S01: The droplet generator emits tin microdroplets into the vacuum chamber and simultaneously inputs a signal to the signal synchronization device.

[0047] Step S02: The signal synchronization control device sends a pulse signal command, and the laser emits laser light outward.

[0048] The main pulse laser is reflected by a reflective phase plate to generate a vortex laser. It is then combined with the pre-pulse laser at a beam combiner.

[0049] Step S03: After the combined laser beam is focused by the beam focusing device, it bombards the tin droplets to generate high-temperature plasma.

[0050] Among them, the pre-pulse with lower energy first interacts with the tin droplets, shaping the tin droplets into a disk-like or mist-like shape. Then, the main pulse vortex laser heats the shaped target material, generating high-temperature plasma and emitting extreme ultraviolet radiation.

[0051] Step S04: The extreme ultraviolet light collection device collects the extreme ultraviolet light emitted by the plasma and focuses it onto the output window.

[0052] For the specific implementation of steps 1 to 4 above, please refer to the above. Figures 1 to 3 The relevant descriptions of the illustrated embodiments will not be repeated here. This concludes the extreme ultraviolet light generation process.

[0053] This application proposes a scheme using a vortex laser as the driving laser for generating laser plasma. By leveraging the optical field distribution characteristics of the vortex laser, the electron temperature and electron density distribution of the plasma are altered, thereby improving plasma radiation efficiency and addressing the problem of insufficient light source power. Furthermore, based on existing dual-pulse laser plasma source technology, this scheme employs a high-power solid-state laser combined with a reflective phase plate. Through simple modifications to the light source generation device, a laser plasma source device using a vortex laser as the main pulse laser can be realized, facilitating easy upgrades to the light source process.

[0054] The above description does not provide detailed explanations of the technical aspects of each layer's patterning, etching, etc. However, those skilled in the art should understand that various technical means can be used to form layers and regions of the desired shape. Furthermore, to form the same structure, those skilled in the art can also design methods that are not entirely identical to those described above. Additionally, although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination.

[0055] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A laser plasma extreme ultraviolet light source apparatus, characterized by comprising: The device comprises: a droplet generator for generating target microdroplets; a laser system for generating pre-pulse laser and main pulse vortex laser; a beam focusing device for converging the laser generated by the laser system onto the tin microdroplets to produce high-temperature plasma. an extreme ultraviolet light collection device for collecting the extreme ultraviolet light emitted by the plasma and converging the extreme ultraviolet light to an output window; a control signal synchronization device for synchronizing the laser pulses to ensure that the laser pulses can accurately bombard the target microdroplets; a vacuum chamber for providing an environment for generating high-temperature plasma.

2. The apparatus of claim 1, wherein, The laser system comprises a solid-state laser, a vortex light generating device, and a beam combining device. The solid-state laser is composed of two Nd:YAG solid-state lasers, which output 532 nm and 1064 nm wavelength lasers respectively.

3. The vortex laser light generating device according to claim 2, wherein The vortex light generating device is composed of a reflective phase plate, which is made of quartz material and has 32 steps, carrying a phase range of 0-2π, and the size of the phase plate is 120mm×80mm×20mm.

4. The beam combining apparatus of claim 2, wherein The beam combining device is composed of a dichroic mirror, which is made of fused quartz material and has a coating on its surface, so that its transmittance for 532 nm laser is ≥95% and its reflectivity for 1064 nm laser is ≥99% at 45° incidence.

5. The apparatus of claim 1, wherein, The target material is tin.

6. The apparatus of claim 1, wherein, The laser beam in the laser system is composed of pre-pulse and main pulse vortex laser.

7. A method of generating extreme ultraviolet light by a laser plasma extreme ultraviolet light source apparatus, characterized by, The laser plasma extreme ultraviolet light source device comprises a droplet generator, a laser system, a beam focusing device, an extreme ultraviolet light collection device, and a vacuum chamber, and the method comprises: Generating target microdroplets by the droplet generator; Generating pre-pulse and main pulse vortex laser beams by the laser system. Focusing the laser beam generated by the laser system onto the target microdroplets by the beam focusing device to produce high-temperature plasma; Collecting the extreme ultraviolet light emitted by the plasma by the extreme ultraviolet light collection device and converging it to the output window.

8. The method of claim 7, wherein, The pre-pulse and main pulse vortex laser beams generated by the laser system comprise: Outputting 532 nm pre-pulse laser and 1064 nm main pulse laser by the solid-state laser of claim 2; After the main pulse laser passes through the vortex light generating device of claim 3, vortex laser is generated, and then after the pre-pulse and main pulse laser passes through the beam combining device of claim 4, it is outputted after beam combining.

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