Seed laser system for a radiation source

Abstract

Systems, apparatuses, and methods for dual-channel amplification of laser beams along a common beam path are provided. An example method can include generating a first laser beam and a second laser beam. Subsequently, the example method can include performing dual-channel amplification of the first laser beam and the second laser beam along a common beam path. In some aspects, the first laser beam can include a first wavelength, and the second laser beam can include a second wavelength different from the first wavelength.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Application No. 63 / 007,759, entitled “SEED LASER SYSTEM FOR RADIATIONSOURCE”, filed April 9, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to laser sources for use in, for example, lithography equipment and systems. Background Technology

[0004] A lithography apparatus is a machine that applies a desired pattern onto a substrate, typically onto a target portion of the substrate. Lithography apparatuses can be used, for example, in the fabrication of integrated circuits (ICs). In this context, a pattern forming apparatus, interchangeably referred to as a mask or photomask, can be used to generate a circuit pattern formed on a single layer of the formed IC. This pattern can be transferred onto a target portion (e.g., a portion comprising one or more dies) on a substrate (e.g., a silicon wafer). The transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (e.g., resist) provided on the substrate. Typically, a single substrate will contain a network of continuously patterned adjacent target portions. Conventional lithography apparatuses include so-called steppers and scanners, in which each target portion is irradiated by exposing the entire pattern onto the target portion at once, and in a scanner, each target portion is irradiated by scanning the pattern in a given direction (“scanning” direction) with a radiation beam while simultaneously scanning the target portion parallel or antiparallel (e.g., opposite) to that scanning direction. A pattern can also be transferred from a pattern forming apparatus to a substrate by imprinting the pattern onto the substrate.

[0005] As semiconductor manufacturing processes continue to advance, the size of circuit components continues to shrink, while the number of functional elements (such as transistors) in each device has steadily increased over the decades, following a trend commonly known as Moore's Law. To keep pace with Moore's Law, the semiconductor industry is pursuing technologies capable of creating increasingly smaller features. Photolithography equipment uses electromagnetic radiation to project patterns onto a substrate. The wavelength of this radiation determines the minimum size of the feature that can be patterned on the substrate. Typical wavelengths currently used are 365 nanometers (nm) (i-line), 248 nm, 193 nm, and 13.5 nm.

[0006] Extreme ultraviolet (EUV) radiation, such as electromagnetic radiation with wavelengths of about 50 nm or smaller (sometimes also referred to as soft X-rays) and including light with wavelengths of about 13.5 nm, can be used in or in conjunction with lithography equipment to create extremely small features in or on a substrate, such as a silicon wafer. Lithography equipment using EUV radiation with wavelengths in the range of 4 nm to 20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form even smaller features on a substrate compared to lithography equipment using radiation with wavelengths of, for example, 193 nm.

[0007] Methods for generating EUV light include, but are not limited to, converting a material containing elements such as xenon (Xe), lithium (Li), or tin (Sn) and having an emission line in the EUV range into a plasma state. For example, in one such method known as laser-generated plasma (LPP), plasma can be generated by irradiating a target material with an amplified beam, which may be referred to as a driving laser. The target material is interchangeably referred to as fuel in the context of an LPP source, such as in the form of material droplets, plates, strips, streams, or clusters. For this process, the plasma is typically generated in a sealed container (e.g., a vacuum chamber) and monitored using various types of metering equipment. Summary of the Invention

[0008] This disclosure describes various aspects of systems, apparatus, and methods for dual-pass amplification of different laser beams along a common beam path in, for example, a carbon dioxide (CO2) seed laser system for an EUV radiation source. In some aspects, this disclosure provides performing dual-pass amplification of laser beams, each with a different wavelength, along a common beam path. In some aspects, the wavelength of each laser beam and the corresponding radio frequency characteristics of an acousto-optic modulator positioned along the path of each laser beam can be matched to provide multi-wavelength acousto-optic modulation along the common beam path.

[0009] In some aspects, this disclosure describes a radiation source. The radiation source may include a laser system. The laser system may include a first laser source configured to generate a first laser beam. The laser system may also include a second laser source configured to generate a second laser beam. The laser system may further include a dual-channel amplifier configured to perform dual-channel amplification of the first laser beam along a common beam path. The dual-channel amplifier may also be configured to perform dual-channel amplification of the second laser beam along the common beam path.

[0010] In some aspects, the first laser beam may include a pre-pulsed laser beam. In some aspects, the second laser beam may include a main-pulsed laser beam. In some aspects, the laser system may be configured to use the pre-pulsed laser beam to impinge on a fuel target to generate a modified fuel target. In some aspects, the laser system may also be configured to use the main-pulsed laser beam to impinge on a modified fuel target to generate plasma at a plasma-forming region.

[0011] In some aspects, the first laser beam may include a first wavelength. In some aspects, the second laser beam may include a second wavelength different from the first wavelength. In some aspects, the second wavelength may be greater than approximately the first wavelength.

[0012] In some aspects, the laser system may also include a laser controller. In some aspects, the laser controller may be configured to determine the first wavelength based on the second wavelength. In other aspects, the laser controller may be configured to determine the second wavelength based on the first wavelength.

[0013] In some aspects, the laser system may further include an electro-optic modulator disposed between the second laser source and the dual-channel amplifier. In some aspects, the electro-optic modulator may be configured to output a first laser beam along a common beam path. In some aspects, the electro-optic modulator may also be configured to output a second laser beam along the common beam path. In some aspects, the electro-optic modulator may include a first single-crystal electro-optic modulator, a second single-crystal electro-optic modulator, and a third single-crystal electro-optic modulator. In some aspects, the electro-optic modulator may include a single-crystal electro-optic modulator and a dual-crystal electro-optic modulator. In some aspects, the electro-optic modulator may include a triple-crystal electro-optic modulator. In some aspects, the laser system may further include an acousto-optic modulator disposed along the common beam path between the electro-optic modulator and the dual-channel amplifier. In some aspects, the acousto-optic modulator may be configured to receive the first laser beam from the electro-optic modulator along the common beam path. In some aspects, the acousto-optic modulator may also be configured to receive the second laser beam from the electro-optic modulator along the common beam path. In some aspects, the acousto-optic modulator may also be configured to output the first laser beam to the dual-channel amplifier along the common beam path. In some aspects, the acousto-optic modulator can also be configured to output a second laser beam to a dual-channel amplifier along a common beam path. In some aspects, the acousto-optic modulator can also be configured to output the first laser beam at a first diffraction angle. In some aspects, the acousto-optic modulator can also be configured to output the second laser beam at a second diffraction angle. In some aspects, the second diffraction angle can be approximately equal to the first diffraction angle. In some aspects, the acousto-optic modulator can also be configured to generate a first acoustic grating based on a first radio wave at a first radio frequency, the first acoustic grating being configured to diffract the first laser beam. In some aspects, the acousto-optic modulator can also be configured to generate a second acoustic grating based on a second radio wave at a second radio frequency, the second acoustic grating being configured to diffract the second laser beam. In some aspects, a first mathematical product of a first wavelength and a first radio frequency is approximately equal to a second mathematical product of a second wavelength and a second radio frequency.

[0014] In some aspects, the laser system may further include an acousto-optic modulator disposed along a common beam path. In some aspects, the acousto-optic modulator may be configured to receive a first laser beam from a dual-channel amplifier along the common beam path. In some aspects, the acousto-optic modulator may also be configured to receive a second laser beam from the dual-channel amplifier along the common beam path. In some aspects, the acousto-optic modulator may also be configured to generate a modified first laser beam based on a first wavelength of the first laser beam. In some aspects, the acousto-optic modulator may also be configured to generate a modified second laser beam based on a second wavelength of the second laser beam. In some aspects, the acousto-optic modulator may also be configured to output the modified first laser beam to the dual-channel amplifier along the common beam path. In some aspects, the acousto-optic modulator may also be configured to output the modified second laser beam to the dual-channel amplifier along the common beam path. In some aspects, the acousto-optic modulator may also be configured to generate a first acoustic grating based on a first radio frequency of a first radio wave, the first acoustic grating being configured to diffract the first laser beam. In some aspects, the acousto-optic modulator can also be configured to generate a second acoustic grating based on a second radio frequency of a second radio wave, the second acoustic grating being configured to diffract a second laser beam. In some aspects, the acousto-optic modulator can also be configured to output a first laser beam at a first diffraction angle based on a first acoustic grating. In some aspects, the acousto-optic modulator can also be configured to output a second laser beam at a second diffraction angle based on a second acoustic grating. In some aspects, a first mathematical product of a first wavelength and a first radio frequency can be approximately equal to a second mathematical product of a second wavelength and a second radio frequency. In some aspects, the second diffraction angle can be approximately equal to the first diffraction angle. In some aspects, the dual-channel amplifier can also be configured to perform dual-channel amplification of the first laser beam based on a first amplification of the first laser beam and a second amplification of the modified first laser beam. In some aspects, the dual-channel amplifier can also be configured to perform dual-channel amplification of the second laser beam based on a third amplification of the second laser beam and a fourth amplification of the modified second laser beam.

[0015] In some aspects, the laser system may further include a laser isolation system disposed downstream of the dual-channel amplifier along a common beam path. In some aspects, the laser isolation system may be configured to receive a first laser beam amplified by the dual-channel amplifier along the common beam path. In some aspects, the laser isolation system may also be configured to receive a second laser beam amplified by the dual-channel amplifier along the common beam path. In some aspects, the laser isolation system may also be configured to generate an isolated first laser beam based on the dual-channel amplified first laser beam. In some aspects, the laser isolation system may also be configured to generate an isolated second laser beam based on the dual-channel amplified second laser beam. In some aspects, the isolated first laser beam may include a first isolation factor greater than 10,000. In some aspects, the isolated second laser beam may include a second isolation factor greater than 10,000.

[0016] In some aspects, the laser isolation system may include a first acousto-optic modulator positioned downstream of the dual-channel amplifier along the common beam path. Alternatively, in some aspects, the laser isolation system may also include a second acousto-optic modulator positioned downstream of the first acousto-optic modulator along the common beam path.

[0017] In some aspects, this disclosure describes an apparatus. The apparatus may include a first laser source configured to generate a first laser beam including a first wavelength. The apparatus may also include a second laser source configured to generate a second laser beam including a second wavelength. The apparatus may further include a dual-channel amplifier configured to perform dual-channel amplification of the first laser beam along a common beam path. The dual-channel amplifier may also be configured to perform dual-channel amplification of the second laser beam along the common beam path.

[0018] In some aspects, this disclosure describes a method for dual-channel amplification of two different laser beams along a common beam path. The method may include generating a first laser beam having a first wavelength from a first laser source. The method may also include generating a second laser beam having a second wavelength from a second laser source. The method may further include performing dual-channel amplification of the first laser beam along the common beam path using a dual-channel amplifier. The method may also include performing dual-channel amplification of the second laser beam along the common beam path using a dual-channel amplifier.

[0019] Other features and advantages, as well as the structure and operation of various aspects, are described in detail below with reference to the accompanying drawings. It should be noted that this disclosure is not limited to the specific aspects described herein. Such aspects are presented herein for illustrative purposes only. Additional aspects will be apparent to those skilled in the art based on the teachings contained herein. Attached Figure Description

[0020] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present disclosure and, together with the description, further serve to explain the principles of various aspects of the disclosure and to enable those skilled in the art to make and use various aspects of the disclosure.

[0021] Figure 1A This is a schematic diagram of an example reflective lithography apparatus based on some aspects of this disclosure.

[0022] Figure 1B This is a schematic diagram of an example transmission lithography apparatus based on some aspects of this disclosure.

[0023] Figure 2 Based on some aspects of this disclosure Figure 1A A more detailed schematic diagram of the reflective lithography apparatus shown.

[0024] Figure 3 This is a schematic diagram of an example photolithography unit based on some aspects of this disclosure.

[0025] Figure 4 This is a schematic diagram of an example radiation source for an example reflective lithography apparatus, based on some aspects of this disclosure.

[0026] Figure 5 This is a schematic diagram of an example laser system based on some aspects of this disclosure.

[0027] Figure 6 This is a schematic diagram of another example laser system based on some aspects of this disclosure.

[0028] Figure 7 This is a schematic diagram of another example laser system according to some aspects of this disclosure.

[0029] Figure 8 This is a schematic diagram of another example laser system according to some aspects of this disclosure.

[0030] Figure 9 This is an example method for dual-channel amplification of a laser beam along a common beam path, according to some aspects or parts of this disclosure.

[0031] Figure 10 It is an example computer system for implementing certain aspects or parts thereof of this disclosure.

[0032] The features and advantages of this disclosure will become more apparent from the following detailed description set forth in conjunction with the accompanying drawings, in which the same reference numerals consistently identify corresponding elements. In the drawings, unless otherwise stated, the same reference numerals generally indicate the same, functionally similar, and / or structurally similar elements. Additionally, generally, the leftmost numeral of the reference numerals identifies the drawing in which the reference numeral first appears. Unless otherwise stated, the drawings provided throughout this disclosure should not be construed as being drawn to scale. Detailed Implementation

[0033] This specification discloses one or more embodiments of the features incorporated herein. The disclosed embodiments(s) are merely illustrative of this disclosure. The scope of this disclosure is not limited to the disclosed embodiments. The breadth and scope of this disclosure are defined by the appended claims and their equivalents.

[0034] The described embodiments and references to "an embodiment," "embodiment," "example embodiment," etc., in the specification indicate that the described embodiments may include specific features, structures, or characteristics, but each embodiment may not necessarily include such specific features, structures, or characteristics. Furthermore, these phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with embodiments, it should be understood that, whether explicitly described or not, its influence in conjunction with other embodiments affects the knowledge of those skilled in the art regarding such features, structures, or characteristics.

[0035] Spatially relative terms such as “below,” “under,” “lower,” “above,” “on,” “upper,” etc., may be used in this document to describe the relationship between one element or feature and another element(s) as shown in the figure. In addition to the orientations shown in the figure, spatially relative terms are intended to cover different orientations of the device in use or operation. “Upper” may be oriented in other ways (rotated 90 degrees or otherwise) and the spatially relative descriptors used herein may be interpreted accordingly.

[0036] As used herein, the term "approximately / about" indicates a value of a given quantity that can vary based on a particular technique. Based on a particular technique, the term "approximately / about" can indicate a value of a given quantity that varies within, for example, 10–30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0037] Overview

[0038] In one example, a CO2 seed laser system for an EUV source may include a high-power seed system (HPSS) with a high-power seed module (HPSM). The HPSM may include a CO2 pre-pulse seed source, a CO2 master pulse seed source, and an amplifier. The CO2 pre-pulse seed source emits a pre-pulse beam that traverses the amplifier along a pre-pulse beam path. The CO2 master pulse seed source emits a master pulse beam that traverses the amplifier along a master pulse beam path different from the pre-pulse beam path. Before being output, the pre-pulse beam path can proceed from the CO2 pre-pulse seed source to a first electro-optic modulator (EOM), a first acousto-optic modulator (AOM), a second AOM, a delay line, an amplifier (e.g., first through the amplifier), a third AOM, and finally a fourth AOM. The master pulse beam path can proceed from the CO2 master pulse seed source to a second EOM, a fifth AOM, a sixth AOM, an amplifier (e.g., first through the amplifier), a seventh AOM, a delay line, another delay line, an eighth AOM, an amplifier (e.g., second through the amplifier), and a ninth AOM before being output. In short, the HPSM architecture uses different EOMs and AOMs for the prepulse and main pulse beams, increasing the optical, mechanical, and control complexity of the CO2 seed laser system. As another consequence of the multiple components required for the two beam paths, HPSM can result in high cost, long repair times, insufficient prepulse energy margin, insufficient prepulse blanking level performance, and insufficient product lifespan. Additionally, the prepulse beam passes through the amplifier only once, while the main pulse beam passes through it twice. Therefore, this HPSM architecture only achieves dual-channel amplification for the main pulse beam.

[0039] Conversely, some aspects of this disclosure provide laser systems (e.g., CO2 seed laser systems for EUV radiation sources) that use a common pre-pulse and main pulse beam path (referred to herein as the "common beam path") to provide dual-channel amplification of the pre-pulse and main pulse laser beams. In some aspects, the laser systems disclosed herein may include a first laser source (e.g., a CO2 pre-pulse laser source), a second laser source (e.g., a CO2 main pulse laser source), and a dual-channel amplifier. The first laser source emits a first laser beam (e.g., a pre-pulse laser beam) that traverses the dual-channel amplifier along the common beam path. The second laser source emits a second laser beam (e.g., a main pulse laser beam) that traverses the dual-channel amplifier along the common beam path. The common beam path may advance from the first and second laser sources to an EOM (e.g., a three-crystal EOM), a first AOM, a dual-channel amplifier (e.g., first through the dual-channel amplifier), a second AOM (and in some cases, a polarization rotator), a dual-channel amplifier (e.g., second through the dual-channel amplifier), a third AOM, and a fourth AOM before being output. In some respects, the laser system disclosed herein utilizes an EOM for pulse shaping and an AOM for optical isolation.

[0040] In some aspects, this disclosure provides dual-channel amplification of multiple laser beams using a common beam path. For example, some aspects of this disclosure can provide the generation of a first laser beam having a first wavelength and the generation of a second laser beam having a second wavelength different from the first wavelength. In another example, some aspects of this disclosure can provide dual-channel amplification of the first and second laser beams along a common beam path.

[0041] In some respects, the common prepulse and main pulse beam paths disclosed herein cause the prepulse and main pulse laser beam properties to respond to common mechanical and thermal interferences in the same way, which can lead to more stable system performance, essentially eliminating interference from differential prepulse and main pulse and the need for differential compensators for prepulse and main pulse.

[0042] In some aspects, the laser systems disclosed herein include a three-triggered EOM (e.g., a three-crystal EOM; a single-crystal EOM and a dual-crystal EOM; three single-crystal EOMs) positioned near the beginning of the combined beam path, providing a flexible architecture for controlling the “natural” and “fast” blanking level of the main pulse while reducing the pre-pulse blanking level (e.g., the undesired blanking level in the pre-pulse laser beam). In some aspects, the laser systems disclosed herein apply multiple triggers to the EOM crystal within the same fuel target spacing (e.g., a tin droplet spacing).

[0043] In some respects, the laser systems disclosed herein include AOMs that can also be used for isolation and power flow control. In some respects, the laser systems disclosed herein reduce the gating time for all AOMs to between approximately 500 nanoseconds (ns) and 1,000 ns, thereby resulting in isolation and self-excitation robustness.

[0044] The systems, apparatuses, methods, and computer program products disclosed herein have many exemplary aspects. For example, aspects of this disclosure provide a dual purpose for electro-optic and acousto-optic modulators to provide a common beam path for pre-pulse and main-pulse laser beams, thereby simplifying the laser system (e.g., reducing complexity by up to two times). In some aspects, the laser systems disclosed herein are further simplified based on the utilization of time-dependent gain, scintillation, and isolation in the laser system. In some aspects, the simplification of the laser systems disclosed herein results in reduced costs (e.g., 25%), reduced mean time to repair (e.g., from 30–40 hours to about 10 hours), smaller size (e.g., smaller volume, smaller footprint, or both), increased system availability, increased pre-pulse energy margin (e.g., a threefold increase, providing system operation with high repetition rates), increased pre-pulse blanking level performance, increased pre-pulse amplification (e.g., the laser system implements dual-channel amplification for both the pre-pulse and main-pulse laser beams), reduced pre-pulse and main-pulse differential interference, elimination of the need for pre-pulse and main-pulse differential compensators, and increased product lifespan.

[0045] However, it is beneficial to show example environments in which various aspects of this disclosure can be implemented before describing these aspects in more detail.

[0046] Example lithography system

[0047] Figure 1A and Figure 1B These are schematic diagrams of the lithography apparatus 100 and lithography apparatus 100', respectively, capable of realizing various aspects of this disclosure. Figure 1A and Figure 1B As shown, the lithography apparatus 100 and 100' are illustrated from a viewpoint (e.g., a side view) perpendicular to the XZ plane (e.g., the X-axis points to the right, the Z-axis points upward, and the Y-axis points away from the observer towards the page), while the pattern forming apparatus MA and the substrate W are shown from an additional viewpoint (e.g., a top view) perpendicular to the XY plane (e.g., the X-axis points to the right, the Y-axis points upward, and the Z-axis points away from the page towards the observer).

[0048] In some aspects, lithography apparatus 100 and / or lithography apparatus 100' may include one or more of the following structures: an irradiation system IL (e.g., an irradiator) configured to modulate a radiation beam B (e.g., a deep ultraviolet (DUV) radiation beam or an extreme ultraviolet (EUV) radiation beam); a support structure MT (e.g., a mask stage) configured to support a patterning apparatus MA (e.g., a mask, a photomask, or a dynamic patterning apparatus) and connected to a first positioner PM, the first positioner PM being configured to precisely position the patterning apparatus MA; and a substrate support, such as a substrate stage WT (e.g., a wafer stage), configured to support a substrate W (e.g., a wafer coated with resist) and connected to a second positioner PW, the second positioner PW being configured to precisely position the substrate W. Lithography apparatus 100 and 100' also have a projection system PS (e.g., a refractive projection lens system) configured to project a pattern imparted by the radiation beam B by the patterning apparatus MA onto a target portion C (e.g., a portion including one or more dies) of the substrate W. In the lithography apparatus 100, the pattern forming apparatus MA and the projection system PS are reflective. In the lithography apparatus 100', the pattern forming apparatus MA and the projection system PS are transmissive.

[0049] In some respects, during operation, the irradiation system IL can receive a radiation beam from the radiation source SO (e.g., via...). Figure 1B The beam delivery system BD is shown in the diagram. The illumination system IL can include various types of optical structures, such as refractive, reflective, antirefractive, magnetic, electromagnetic, electrostatic, and other types of optical components or any combination thereof, for guiding, shaping, or controlling radiation. In some aspects, the illumination system IL can be configured to modulate the radiation beam B to have a desired spatial and angular intensity distribution in its cross-section at the plane of the pattern forming apparatus MA.

[0050] In some aspects, the support structure MT can support the patterning apparatus MA according to the orientation of the patterning apparatus MA relative to the reference frame, the design of at least one of the lithography equipment 100 and 100', and other conditions such as whether the patterning apparatus MA is supported in a vacuum environment. The support structure MT can support the patterning apparatus MA using mechanical, vacuum, electrostatic, or other clamping techniques. The support structure MT can be, for example, a frame or stage that can be fixed or movable as needed. By using sensors, the support structure MT can ensure that the patterning apparatus MA is in the desired position, for example, relative to the projection system PS.

[0051] The term "patterning apparatus" MA should be interpreted broadly to refer to any apparatus that can be used to impart a pattern to the cross-section of the radiation beam B to create a pattern in a target portion C of the substrate W. The pattern imparted to the radiation beam B can correspond to a specific functional layer in the device created in the target portion C for forming an integrated circuit.

[0052] In some respects, the pattern forming apparatus MA can be transmissive (e.g., in... Figure 1B In the lithography equipment 100') or reflective type (such as in Figure 1A (In the lithography apparatus 100). The pattern forming apparatus MA can include various structures, such as a mask, a mask, a programmable mirror array, a programmable LCD panel, other suitable structures, or combinations thereof. The mask can include mask types such as binary, alternating phase-shift, or attenuation phase-shift, as well as various hybrid mask types. In one example, the programmable mirror array can include a matrix arrangement of small mirrors, each of which can be individually tilted to reflect the incoming radiation beam in different directions. The tilted mirrors can impart a pattern reflected by the matrix of small mirrors in the radiation beam B.

[0053] The term "projection system" PS should be interpreted broadly and can encompass any type of projection system, including refractive, reflective, antirefractive, magnetic, distorting, electromagnetic, and electrostatic optical systems, or any combination thereof, suitable for the exposure radiation used and / or suitable for other factors such as the use of an immersion liquid (e.g., on a substrate W) or a vacuum. A vacuum environment can be used for EUV or electron beam radiation because other gases can absorb excessive radiation or electrons. Therefore, a vacuum environment can be provided throughout the beam path by means of vacuum walls and vacuum pumps. Additionally, in some respects, any use of the term "projection lens" herein can be interpreted as synonymous with the more general term "projection system" PS.

[0054] In some aspects, lithography apparatus 100 and / or lithography apparatus 100' may be of the type having two (e.g., "dual-stage") or more substrate stages WT and / or two or more mask stages. In such a "multi-stage" machine, additional substrate stages WT can be used in parallel, or preparation steps can be performed on one or more stages while exposure is being performed using one or more other substrate stages WT. In one example, while another substrate W located on another substrate stage WT is being used to expose a pattern on another substrate W, subsequent exposure preparation steps for substrate W can be performed on substrate W located on one of the substrate stages WT. In some aspects, the additional stage may not be a substrate stage WT.

[0055] In some aspects, in addition to the substrate stage WT, the lithography apparatus 100 and / or lithography apparatus 100' may include a measurement stage. The measurement stage may be arranged to support sensors. The sensors may be arranged to measure the properties of the projection system PS, the properties of the radiation beam B, or both. In some aspects, the measurement stage may support multiple sensors. In some aspects, the measurement stage may be movable below the projection system PS when the substrate stage WT is moved away from the projection system PS.

[0056] In some aspects, lithography apparatus 100 and / or lithography apparatus 100' may also be of the type in which at least a portion of the substrate may be covered with a liquid (e.g., water) having a relatively high refractive index to fill the space between the projection system PS and the substrate W. Immersion liquids may also be applied to other spaces within the lithography apparatus, such as the space between the patterning apparatus MA and the projection system PS. Immersion techniques are used to increase the numerical aperture of the projection system. The term "immersion" as used herein does not mean that a structure such as the substrate must be immersed in the liquid, but only that the liquid is located between the projection system and the substrate during exposure. Various immersion techniques are described in U.S. Patent No. 6,952,253, entitled "LITHOGRAPHIC APPARATUS AND DEVICEMANUFACTURING METHOD," published October 4, 2005, the entire contents of which are incorporated herein by reference.

[0057] refer to Figure 1A and Figure 1B The irradiation system IL receives the radiation beam B from the radiation source SO. For example, when the radiation source SO is an excimer laser, the radiation source SO and the lithography apparatus 100 or 100' can be separate physical entities. In this case, the radiation source SO is not considered to be part of the lithography apparatus 100 or 100', and the radiation beam B is delivered via a beam delivery system BD (e.g., ...). Figure 1B (As shown) The beam delivery system BD transmits light from the radiation source SO to the irradiation system IL, including, for example, suitable directional mirrors and / or beam expanders. In other cases, such as when the radiation source SO is a mercury lamp, the radiation source SO may be a component of the lithography apparatus 100 or 100'. If desired, the radiation source SO and the irradiator IL together with the beam delivery system BD may be referred to as the radiation system.

[0058] In some aspects, the illumination system IL may include an adjuster AD for adjusting the angular intensity distribution of the radiation beam. Typically, at least the outer and / or inner radial ranges of the intensity distribution in the pupil plane of the illuminator (typically referred to as "σ-outer" and "σ-inner," respectively) can be adjusted. Additionally, the illumination system IL may include various other components, such as an integrator IN and a radiation collector CO (e.g., a focuser or collector optics). In some aspects, the illumination system IL can be used to adjust the radiation beam B to have a desired uniformity and intensity distribution in its cross-section.

[0059] refer to Figure 1A In operation, the radiation beam B can be incident on a patterning apparatus MA (e.g., a mask, a mask plate, a programmable mirror array, a programmable LCD panel, any other suitable structure or combination thereof), and can be patterned by a pattern (e.g., a design layout) present on the patterning apparatus MA, which can be supported on a support structure MT (e.g., a mask stage). In the lithography apparatus 100, the radiation beam B can be reflected from the patterning apparatus MA. After passing through the patterning apparatus MA (e.g., after being reflected from the patterning apparatus MA), the radiation beam B can pass through a projection system PS, which can focus the radiation beam B onto a target portion C of the substrate W or onto a sensor arranged at a stage.

[0060] In some respects, the substrate stage WT can be precisely moved, for example, to position different target portions C in the path of the radiation beam B, using a second positioner PW and a position sensor IFD2 (e.g., an interferometric device, a linear encoder, or a capacitive sensor). Similarly, a first positioner PM and another position sensor IFD1 (e.g., an interferometric device, a linear encoder, or a capacitive sensor) can be used to precisely position the patterning apparatus MA relative to the path of the radiation beam B.

[0061] In some aspects, the pattern forming apparatus MA and the substrate W can be aligned using mask alignment marks M1 and M2 and substrate alignment marks P1 and P2. Although Figure 1A and Figure 1B Simultaneously, substrate alignment marks P1 and P2 occupy dedicated target portions, but substrate alignment marks P1 and P2 can be located in the space between target portions. When substrate alignment marks P1 and P2 are located between target portions C, they are called scribing alignment marks. Substrate alignment marks P1 and P2 can also be arranged in the target portion C region as in-die marks. These in-die marks can also be used as metrological marks, for example, for overlap measurements.

[0062] In some respects, for illustrative purposes and not for limitation, one or more figures in this paper may utilize a Cartesian coordinate system. A Cartesian coordinate system comprises three axes: the X-axis, the Y-axis, and the Z-axis. Each of the three axes is orthogonal to the other two axes (e.g., the X-axis is orthogonal to the Y and Z axes, the Y-axis is orthogonal to the X and Z axes, and the Z-axis is orthogonal to the X and Y axes). A rotation about the X-axis is called an Rx rotation. A rotation about the Y-axis is called an Ry rotation. A rotation about the Z-axis is called an Rz rotation. In some respects, the X and Y axes define a horizontal plane, while the Z-axis is in the vertical direction. In some respects, the orientation of the Cartesian coordinate system may be different, for example, such that the Z-axis has a component along the horizontal plane. In some respects, another coordinate system, such as a cylindrical coordinate system, may be used.

[0063] refer to Figure 1B A radiation beam B is incident on a patterning apparatus MA supported on a support structure MT and patterned by the patterning apparatus MA. After passing through the patterning apparatus MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam onto a target portion C of the substrate W. In some aspects, the projection system PS may have a pupil conjugate with the illumination system pupil. In some aspects, the portions of the radiation can be emitted from the intensity distribution at the illumination system pupil and pass through the mask pattern without being affected by diffraction at the mask pattern MP, thus creating an image of the intensity distribution at the illumination system pupil.

[0064] The projection system PS projects an image MP' of a mask pattern MP onto a resist layer coated on a substrate W, wherein the image MP' is formed by a diffracted beam generated from radiation from the mask pattern MP by a distribution of intensity. For example, the mask pattern MP may comprise an array of lines and spacings. Radiation diffraction at the array, distinct from zero-order diffraction, generates a directional diffracted beam with a change in direction perpendicular to the lines. An undiffracted beam (e.g., a so-called zero-order diffracted beam) passes through the pattern without any change in its propagation direction. The zero-order diffracted beam passes upstream of the pupil conjugate of the projection system PS through an upper lens or upper lens group of the projection system PS to reach the pupil conjugate. The intensity distribution portion in the pupil conjugate plane and associated with the zero-order diffracted beam is an image of the intensity distribution in the pupil of the illumination system IL. In some aspects, the aperture device may be arranged at or substantially at the plane comprising the pupil conjugate of the projection system PS.

[0065] The projection system PS is arranged to capture not only the zeroth-order diffracted beam but also first-order or higher-order diffracted beams (not shown) by means of a lens or lens group. In some aspects, dipole illumination for imaging a line pattern extending in a direction perpendicular to the line can be used to utilize the resolution-enhancing effect of dipole illumination. For example, a first-order diffracted beam interferes with the corresponding zeroth-order diffracted beam at the level of the substrate W to create an image of the mask pattern MP at the highest possible resolution and process window (e.g., the available depth of focus combined with permissible exposure dose deviation). In some aspects, astigmatism can be reduced by providing a radiating pole (not shown) in the opposing confinement of the pupil of the illumination system. Furthermore, in some aspects, astigmatism can be reduced by blocking the zeroth-order beam associated with the radiating pole in the opposing confinement of the pupil of the projection system PS. This is described in more detail in U.S. Patent No. 7,511,799 entitled “LITHOGRAPHIC PROJECTION APPARATUS AND A DEVICE MANUFACTURING METHOD”, published on March 31, 2009, which is incorporated herein by reference in its entirety.

[0066] In some aspects, with the aid of a second positioner PW and a position measurement system PMS (e.g., a position sensor including an interferometric device, a linear encoder, or a capacitive sensor), the substrate stage WT is precisely moved, for example, to position different target portions C in the path of the radiation beam B at focused and aligned locations. Similarly, the first positioner PM and another position sensor (e.g., an interferometric device, a linear encoder, or a capacitive sensor) ( Figure 1B (Not shown) can be used to precisely position the patterning apparatus MA relative to the path of the radiation beam B (e.g., after mechanical retrieval from the mask library or during scanning). The patterning apparatus MA and the substrate W can be aligned using mask alignment marks M1 and M2 and substrate alignment marks P1 and P2.

[0067] Typically, the movement of the support structure MT can be achieved using long-stroke positioners (coarse positioning) and short-stroke positioners (fine positioning), which form part of the first positioner PM. Similarly, the movement of the substrate stage WT can be achieved using long-stroke and short-stroke positioners, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the support structure MT can be connected only to the short-stroke actuator or can be fixed. The patterning apparatus MA and the substrate W can be aligned using mask alignment marks M1 and M2 and substrate alignment marks P1 and P2. Although the substrate alignment marks (as shown) occupy dedicated target portions, they can be located in the space between the target portions (e.g., scribing alignment marks). Similarly, if more than one die is provided on the patterning apparatus MA, the mask alignment marks M1 and M2 can be located between the dies.

[0068] The support structure MT and patterning apparatus MA can be located within a vacuum chamber V, where an in-vacuum robot can be used to move the patterning apparatus (such as a mask) into and out of the vacuum chamber. Alternatively, when the support structure MT and patterning apparatus MA are located outside the vacuum chamber, an out-of-vacuum robot, similar to the in-vacuum robot, can be used for various transport operations. In some cases, both the in-vacuum and out-of-vacuum robots need to be calibrated for the smooth transfer of any payload (e.g., a mask) to a fixed motion support at a transfer station.

[0069] In some respects, lithography equipment 100 and lithography equipment 100' can be used in at least one of the following modes:

[0070] 1. In step mode, the support structure MT and substrate stage WT remain essentially stationary, while the entire pattern imparted by the radiation beam B is simultaneously projected onto the target portion C (e.g., a single static exposure). The substrate stage WT is then shifted in the X and / or Y directions so that different target portions C can be exposed.

[0071] 2. In the scanning mode, while the pattern imparted by the radiation beam B is projected onto the target portion C, the support structure MT and the substrate stage WT are scanned synchronously (e.g., single dynamic exposure). The velocity and direction of the substrate stage WT relative to the support structure MT (e.g., mask stage) can be determined by the (reduced) magnification and image inversion characteristics of the projection system PS.

[0072] 3. In another mode, the support structure MT supporting the programmable patterning apparatus MA remains substantially stationary, and the substrate stage WT moves or scans as the pattern imparted by the radiation beam B is projected onto the target portion C. A pulsed radiation source SO can be employed, and the programmable patterning apparatus is updated as needed, after each movement of the substrate stage WT or between successive radiation pulses during scanning. This operating mode can be readily applied to maskless lithography utilizing the programmable patterning apparatus MA (such as a programmable mirror array).

[0073] In some respects, the lithography equipment 100 and the lithography equipment 100' may adopt a combination and / or a variation or a completely different usage mode of the above-described usage modes.

[0074] In some aspects, such as Figure 1A As shown, the lithography apparatus 100 may include an EUV source configured to generate an EUV radiation beam B for EUV lithography. Typically, the EUV source may be configured in a radiation source SO, and the corresponding irradiation system IL may be configured to adjust the EUV radiation beam B of the EUV source.

[0075] Figure 2 The lithography apparatus 100 is shown in more detail. The lithography apparatus 100 includes a radiation source SO (e.g., a source collector device), an irradiation system IL, and a projection system PS. (See attached image.) Figure 2 As shown, the lithography apparatus 100 is illustrated from a viewpoint (e.g., a side view) perpendicular to the XZ plane (e.g., the X-axis points to the right and the Z-axis points upward).

[0076] The radiation source SO is constructed and arranged such that a vacuum environment can be maintained within the closed structure 220. The radiation source SO includes a source chamber 211 and a collector chamber 212, and is configured to generate and transmit EUV radiation. EUV radiation can be generated from a gas or vapor, such as xenon (Xe), lithium (Li), or tin (Sn), wherein EUV radiation from the emitting plasma 210 is created to emit radiation in the EUV range of the electromagnetic spectrum. The at least partially ionized EUV radiation emitting plasma 210 can be created, for example, by a discharge or a laser beam. For example, a partial pressure of approximately 10.0 Pascals (Pa) of Xe gas, Li vapor, Sn vapor, or any other suitable gas or vapor can be used to efficiently generate radiation. In some aspects, a plasma that excites tin is provided to generate EUV radiation.

[0077] Radiation emitted by EUV radiation-emitting plasma 210 is transmitted from source chamber 211 to collector chamber 212 via an optional gas barrier or contaminant trap 230 (e.g., in some cases also referred to as a contaminant barrier or vane trap), which is positioned within or after an opening in source chamber 211. The contaminant trap 230 may include a channel structure. The contaminant trap 230 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap 230 further indicated herein includes at least a channel structure.

[0078] Collector chamber 212 may include a radiation collector CO (e.g., a focuser or collector optics), which may be a so-called grazing incidence collector. The radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation passing through the radiation collector CO may be reflected from a grating spectral filter 240 to be focused into a virtual source point IF. The virtual source point IF is often referred to as the intermediate focus, and the source collector device is arranged such that the virtual source point IF is located at or near the opening 219 in the closed structure 220. The virtual source point IF is an image of the EUV radiation-emitting plasma 210. The grating spectral filter 240 is specifically used to suppress infrared (IR) radiation.

[0079] Subsequently, radiation passes through an illumination system IL, which may include a faceted field mirror assembly 222 and a faceted pupil mirror assembly 224. The faceted field mirror assembly 222 and the faceted pupil mirror assembly 224 are arranged to provide a desired angular distribution of the radiation beam 221 at the patterning apparatus MA, and to provide a desired uniformity of radiation intensity at the patterning apparatus MA. When the radiation beam 221 is reflected at the patterning apparatus MA supported by the support structure MT, a patterned beam 226 is formed, and the patterned beam 226 is imaged by the projection system PS via reflective elements 228 and 229 onto a substrate W supported by a wafer stage or substrate stage WT.

[0080] More components than are typically shown in the irradiation system IL and projection system PS. Optionally, the grating spectral filter 240 may be present depending on the type of lithography equipment. Furthermore, more than... Figure 2 The mirror shown is a multi-mirror mirror. For example, with Figure 2 In contrast, the projection system PS can contain 1 to 6 additional reflective elements.

[0081] like Figure 2As shown, the radiation collector CO is depicted as a nested collector having grazing incidence reflectors 253, 254, and 255, as an example only of a collector (or collector mirror). The grazing incidence reflectors 253, 254, and 255 are arranged symmetrically about the optical axis O, and this type of radiation collector CO is preferably used in combination with a discharge-generated plasma (DPP) source.

[0082] Example lithography unit

[0083] Figure 3 The image shows a lithography unit 300, sometimes also called a lithography pool or cluster. For example... Figure 3 As shown, the lithography unit 300 is illustrated from a viewpoint (e.g., a top view) perpendicular to the XY plane (e.g., the X-axis points to the right and the Y-axis points upward).

[0084] Lithography equipment 100 or 100' may form part of lithography unit 300. Lithography unit 300 may also include one or more devices for performing pre-exposure and post-exposure processes on a substrate. For example, these devices may include a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a chiller CH, and a baking plate BK. A substrate processor RO (e.g., a robot) picks up substrates from input / output ports I / O1 and I / O2, moves them between different processing devices, and transfers them to the loading chamber LB of lithography equipment 100 or 100'. These devices, generally referred to collectively as tracks, are under the control of a track control unit TCU, which is itself controlled by a supervisory control system SCS, which also controls the lithography equipment via a lithography control unit LACU. Therefore, different devices can be operated to maximize throughput and processing efficiency.

[0085] Example radiation source

[0086] Figure 4 The image shows an exemplary reflective lithography apparatus (e.g., Figure 1A An example of the radiation source SO in a lithography device 100. Figure 4 As shown, the radiation source SO is illustrated from a viewpoint (e.g., a top view) perpendicular to the XY plane described below.

[0087] Figure 4The radiation source SO shown is of the type that can be referred to as a laser-generated plasma (LPP) source. A laser system 401, which may include, for example, a carbon dioxide (CO2) laser, is arranged to deposit energy into a fuel target 403' via one or more laser beams 402, such as one or more discrete tin (Sn) droplets supplied from a fuel target generator 403 (e.g., a fuel emitter, droplet generator). According to some aspects, the laser system 401 may be a pulsed, continuous-wave, or quasi-continuous-wave laser, or may operate in a pulsed, continuous-wave, or quasi-continuous-wave manner. The trajectory of the fuel target 403' (e.g., droplets) emitted from the fuel target generator 403 may be parallel to the X-axis. According to some aspects, one or more laser beams 402 propagate in a direction parallel to the Y-axis, which is perpendicular to the X-axis. The Z-axis is perpendicular to both the X and Y axes and typically extends into (or out of) the plane of the page, but in other aspects, other configurations are used. In some embodiments, the laser beam 402 may propagate in a direction different from that parallel to the Y-axis (e.g., in a direction different from that orthogonal to the X-axis direction of the trajectory of the fuel target 403').

[0088] In some aspects, one or more laser beams 402 may include a pre-pulse laser beam and a main pulse laser beam. In these aspects, laser system 401 may be configured to use the pre-pulse laser beam to impinge on each fuel target 403' to generate a modified fuel target. Laser system 401 may also be configured to use the main pulse laser beam to impinge on each modified fuel target to generate plasma 407.

[0089] Although tin is referenced in the following description, any suitable target material can be used. The target material can be, for example, in liquid form and can be, for example, a metal or alloy. The fuel target generator 403 may include a nozzle configured to guide tin (e.g., in the form of a fuel target 403' (e.g., discrete droplets)) along a trajectory toward the plasma formation region 404. Throughout the specification, references to “fuel,” “fuel target,” or “fuel droplets” should be understood to refer to the target material (e.g., droplets) emitted by the fuel target generator 403. The fuel target generator 403 may include a fuel emitter. One or more laser beams 402 are incident on the target material (e.g., tin) at the plasma formation region 404. Laser energy is deposited into the target material to create a plasma 407 at the plasma formation region 404. During the deexcitation and recombination of ions and electrons in the plasma, radiation, including EUV radiation, is emitted from the plasma 407.

[0090] EUV radiation is collected and focused by radiation collector 405 (e.g., radiation collector CO). In some aspects, radiation collector 405 may include a near-vertical incident radiation collector (sometimes more generally referred to as a vertical incident radiation collector). Radiation collector 405 may be a multilayer structure arranged to reflect EUV radiation (e.g., EUV radiation having a desired wavelength such as about 13.5 nm). According to some aspects, radiation collector 405 may have an elliptical configuration with two focal points. As discussed herein, the first focal point may be located at plasma formation region 404, and the second focal point may be located at intermediate focal point 406.

[0091] In some respects, the laser system 401 may be located at a relatively long distance from the radiation source SO. In this case, one or more laser beams 402 can be transmitted from the laser system 401 to the radiation source SO by means of a beam delivery system (not shown) including, for example, suitable directional mirrors and / or beam expanders and / or other optical devices. The laser system 401 and the radiation source SO can be considered together as a radiation system.

[0092] Radiation reflected by radiation collector 405 forms a radiation beam B. Radiation beam B is focused at a point (e.g., intermediate focus 406) to form an image of plasma formation region 404, which acts as a virtual radiation source for irradiation system IL. The point where radiation beam B is focused may be referred to as the intermediate focus (IF) (e.g., intermediate focus 406). Radiation source SO is arranged such that intermediate focus 406 is located at or near the opening 408 in the closed structure 409 of radiation source SO.

[0093] A radiation beam B is transmitted from a radiation source SO to an illumination system IL, which is configured to modulate the radiation beam B. The radiation beam B passes through the illumination system IL and is incident on a patterning apparatus MA supported by a support structure MT. The patterning apparatus MA reflects the radiation beam B and patterns it. After reflection from the patterning apparatus MA, the patterned radiation beam B enters a projection system PS. The projection system includes multiple mirrors configured to project the radiation beam B onto a substrate W supported by a substrate stage WT. The projection system PS can apply a reduction factor to the radiation beam to form an image with features smaller than the corresponding features on the patterning apparatus MA. For example, a reduction factor of 4 can be applied. Although in Figure 2 The projection system PS is shown as having two mirrors, but the projection system may include any number of mirrors (e.g., six mirrors).

[0094] The radiation source SO may also include Figure 4Components not shown in the diagram. For example, a spectral filter can be provided in the radiation source SO. The spectral filter is essentially transmissive to EUV radiation, but essentially blocks radiation of other wavelengths, such as infrared radiation.

[0095] The radiation source SO (or radiation system) may also include a fuel target imaging system for acquiring images of the fuel target (e.g., droplets) in the plasma formation region 404, or more specifically, images of the shadow of the fuel target. The fuel target imaging system can detect light diffracted from the edges of the fuel target. Reference to images of the fuel target below should also be understood as images of the shadow of the fuel target or images of the diffraction pattern caused by the fuel target.

[0096] The fuel target imaging system may include photodetectors, such as CCD arrays or CMOS sensors; however, it should be understood that any imaging device suitable for acquiring images of the fuel target may be used. It should be understood that, in addition to photodetectors, the fuel target imaging system may also include optical components, such as one or more lenses. For example, the fuel target imaging system may include a camera 410, such as a light sensor or a combination of a light detector and one or more lenses. The optical components may be selected such that the light sensor or camera 410 acquires near-field and / or far-field images. The camera 410 may be located at any suitable location within the radiation source SO, from which the camera has one or more markers provided on the plasma formation region 404 and the radiation collector 405. Figure 4 (Not shown in the image) line of sight. However, in some aspects, it may be necessary to position the camera 410 away from the propagation path of one or more laser beams 402 and away from the trajectory of the fuel target emitted from the fuel target generator 403 to avoid damage to the camera 410. According to some aspects, the camera 410 is configured to provide an image of the fuel target to the laser controller 411 via connection 412. Connection 412 is shown as a wired connection, but it should be understood that connection 412 (and other connections mentioned herein) can be implemented as a wired connection or a wireless connection or a combination thereof.

[0097] like Figure 4 As shown, the radiation source SO may include a fuel target generator 403 configured to generate fuel targets 403' (e.g., discrete tin droplets) and emit them toward the plasma formation region 404. The radiation source SO may also include a laser system 401 configured to strike one or more fuel targets 403' with one or more laser beams 402 to generate plasma 407 at the plasma formation region 404. The radiation source SO may also include a radiation collector 405 (e.g., a radiation collector CO) configured to collect the radiation emitted by the plasma 407.

[0098] Example laser system

[0099] Figure 5 This is a schematic diagram of an example laser system 500 according to some aspects of this disclosure. In some aspects, the example laser system 500 may include a first laser source 502 (e.g., a CO2 prepulse seed laser source), a second laser source 504 (e.g., a CO2 main pulse seed laser source), a beam path combiner 506 (e.g., a dichroic beam splitter (DBS), a thin-film polarizer (TFP), a beam multiplexer, or any other suitable optical structure or combination of optical structures), an EOM 508 (e.g., a three-crystal EOM, a three-trigger EOM), a first AOM 510, a dual-channel amplifier 512, a second AOM 514, and a laser isolation system 516, which includes a third AOM 518, and in some optional aspects, a fourth AOM 520. Additionally or alternatively, in some aspects, the example laser system 500 may include a reference... Figure 4 The laser system described 401, reference Figure 6 Example laser system 600 described, reference Figure 7 Example laser system 700 described, reference Figure 8 The example laser system 800 described herein, or any combination thereof, describes any structure, technology, or feature.

[0100] In some aspects, the first laser source 502 may be configured to generate a first laser beam (e.g., a pre-pulse laser beam) traveling along a first beam path 582 to the beam path combiner 506. In some aspects, the second laser source 504 may be configured to generate a second laser beam (e.g., a main pulse laser beam) traveling along a second beam path 584 to the beam path combiner 506. In some aspects, the beam path combiner 506 may be configured to combine the first beam path 582 and the second beam path 584 to generate a common beam path 586 for both the first and second laser beams.

[0101] In some aspects, the first and second laser beams can travel from the output of the beam path combiner 506 to the input of the EOM 508 along a first portion 586a of the common beam path 586. In some aspects, the first and second laser beams can travel from the output of the EOM 508 to the input of the first AOM 510 along a second portion 586b of the common beam path 586.

[0102] In some aspects, the first and second laser beams can travel from the output of the first AOM 510 to the first input of the dual-channel amplifier 512 along a third portion 586c of the common beam path 586. In some aspects, after first passing through the dual-channel amplifier 512, the first and second laser beams can travel from the first output of the dual-channel amplifier 512 to the input of the second AOM 514 along a fourth portion 586d of the common beam path 586. In some aspects, the first and second laser beams can travel from the output of the second AOM 514 to the second input of the dual-channel amplifier 512 along a fifth portion 586e of the common beam path 586.

[0103] In some cases, the example laser system 500 may include a polarization rotator positioned along a common beam path 586 after the second AOM 514 and before the second input of the dual-channel amplifier 512. The polarization rotator may be configured to rotate the polarization of the first laser beam, the second laser beam, or both by any suitable degree of rotation, such as 90 degrees.

[0104] In some respects, after the second pass through the dual-channel amplifier 512, the first and second laser beams can travel along the sixth portion 586f of the common beam path 586 from the second pass output of the dual-channel amplifier 512 to the input of the third AOM 518.

[0105] In some aspects, the first and second laser beams can travel from the output of the third AOM 518 to the input of the fourth AOM 520 along the seventh portion 586g of the common beam path 586. In some aspects, the first and second laser beams can travel from the output of the fourth AOM 520 along the eighth portion 586h of the common beam path 586. In some aspects, the fourth AOM 520 can be optional and not included in the laser isolation system 516.

[0106] As a basis for some embodiments, the example laser system 500 may include a first laser source 502 configured to generate a first laser beam (e.g., one of one or more laser beams 402). The example laser system 500 may also include a second laser source 504 configured to generate a second laser beam (e.g., another of one or more laser beams 402). The example laser system 500 may also include a dual-channel amplifier 512 configured to perform dual-channel amplification of the first laser beam along a common beam path 586. The dual-channel amplifier 512 may also be configured to perform dual-channel amplification of the second laser beam along the common beam path 586.

[0107] In some aspects, the first laser beam may include a pre-pulse laser beam. In some aspects, the second laser beam may include a main pulse laser beam. In some aspects, the pre-pulse laser beam and the main pulse laser beam may be time-separated for a duration of less than about 3 microseconds (e.g., about 2 microseconds). In some aspects, the example laser system 500 may be configured to use the pre-pulse laser beam to impinge on a fuel target (e.g., one of fuel targets 403') to generate a modified fuel target. In some aspects, the example laser system 500 may also be configured to use the main pulse laser beam to impinge on the modified fuel target to generate plasma (e.g., plasma 407) at a plasma formation region (e.g., plasma formation region 404).

[0108] In some aspects, the first laser beam may include a first wavelength. In some aspects, the second laser beam may include a second wavelength different from the first wavelength. In some aspects, the second wavelength may be greater than approximately the first wavelength.

[0109] In some aspects, the AOM (e.g., a first AOM 510, a second AOM 514, a third AOM 518, a fourth AOM 520, any other suitable AOM or structure, or any combination thereof) can be configured to generate a first acoustic grating based on a first radio wave at a first radio frequency, the first acoustic grating being configured to diffract a first laser beam. In some aspects, the AOM can also be configured to generate a second acoustic grating based on a second radio wave at a second radio frequency, the second acoustic grating being configured to diffract a second laser beam. In some aspects, the AOM can also be configured to output the first laser beam at a first diffraction angle based on the first acoustic grating. In some aspects, the AOM can also be configured to output the second laser beam at a second diffraction angle based on the second acoustic grating. In some aspects, a first mathematical product of a first wavelength of the first laser beam and a first radio wave at a first radio frequency can be approximately equal to a second mathematical product of a second wavelength of the second laser beam and a second radio wave at a second radio frequency. In some aspects, the second diffraction angle can be approximately equal to the first diffraction angle, such that the diffracted first laser beam and the diffracted second laser beam follow a common beam path. In some respects, the mathematical multiplication between the optical wavelength of light and the radio frequency represents the "acousto-optic" effect in AOM.

[0110] In an exemplary example, the first wavelength of the first laser beam and the first radio frequency of the first radio wave can be approximately 10.26 micrometers and approximately 41.29 MHz, respectively, and the second wavelength of the second laser beam and the second radio frequency of the second radio wave can be approximately 10.59 micrometers and approximately 40 MHz, respectively. Therefore, the first mathematical product of the first wavelength of the first laser beam and the first radio frequency of the first radio wave can be approximately 423.64, and the second mathematical product of the second wavelength of the second laser beam and the second radio frequency of the second radio wave can be approximately 423.60, with the second mathematical product being approximately equal to the first mathematical product.

[0111] In some aspects, the example laser system 500 may also include a laser controller (e.g., laser controller 411, example computing system 1000). In some aspects, the laser controller may include an AOM radio frequency (RF) driver configured to drive the AOM (e.g., by generating an AOM control signal configured to instruct the AOM to generate radio waves, generate acoustic wave packets, generate acoustic gratings, and perform other suitable operations, and transmitting the generated AOM control signal to the AOM). In some aspects, the laser controller may be configured to provide dual-wavelength operation of the AOM (e.g., prepulse and main pulse) using a wavelength-matched RF frequency technique to provide diffraction of the prepulse laser beam and the main pulse laser beam in the same direction. For example, the laser controller may be configured to determine a first wavelength of the first laser beam and a first RF of the first radio wave based on a second mathematical product of a second wavelength of the second laser beam and a second RF of the second radio wave, as shown in Equations 1 and 2.

[0112]

[0113] λ PP f a，PP =λ MP f a，MP (2)

[0114] Where θ B λ represents the diffraction angle. PP f represents the wavelength of the pre-pulsed laser beam. a,PP λ represents the radio frequency (RF) used to generate a acoustic grating within the AOM to diffract the pre-pulsed laser beam. MP f represents the wavelength of the main pulse laser beam. a,MP This represents the radio frequency (RF) used to generate a acoustic grating within the AOM to diffract the main pulse laser beam, and V a This represents the velocity of sound in the AOM (e.g., the velocity of sound in Ge if the AOM includes a germanium (Ge) crystal). In an exemplary example, based on electronic information indicating that the second wavelength and the second radio frequency are approximately 10.59 micrometers and approximately 40 MHz, respectively, the laser controller can determine that the first wavelength and the first radio frequency can be approximately 10.26 micrometers and approximately 41.29 MHz, respectively. In other aspects, the laser controller can be configured to determine the second wavelength and the second radio frequency based on a first mathematical product of the first wavelength and the first radio frequency. In some aspects, dual-wavelength operation of the AOM can be provided by changing the RF driver connected to the AOM without altering the AOM itself.

[0115] In some aspects, to provide dual-wavelength operation of the AOM, the laser controller (e.g., using an AOMRF driver) can be configured such that the radio frequency applied to the AOM is matched to a specific wavelength of the incident light, such that the product of the two remains constant. In some aspects, to provide dual-wavelength operation of the AOM, the laser controller can also be configured to control the power balance between the two laser beams by, for example, controlling the amplitude of the acoustic wave applied to the AOM for a given laser beam. In an exemplary example, the laser controller can be configured to generate and transmit an AOM control signal configured to instruct the AOM to: generate a first acoustic wave packet having a frequency, amplitude, and packet arrival time matched to a first laser beam; and apply the first acoustic wave packet to the first laser beam. The AOM control signal can also instruct the AOM to: generate a second acoustic wave packet having a frequency, amplitude, and packet arrival time matched to a second laser beam; and apply the second acoustic wave packet to the second laser beam. In some aspects, the first and second acoustic wave packets can be different. For example, the second acoustic wave packet can have a different frequency, amplitude, and packet arrival time than the first acoustic wave packet. In some aspects, by matching the RF frequencies, the laser controller can be configured to preserve a common beam path via the same diffraction angle. In some aspects, by controlling the amplitudes of different acoustic wave groups, the laser controller can be configured to achieve a desired power balance between the first and second laser beams. In some aspects, by matching the arrival times of the acoustic groups, the laser controller can be configured to achieve optical isolation in the absence of an incident laser pulse.

[0116] In some aspects, the example laser system 500 may further include an EOM 508 disposed between the second laser source 504 and the dual-channel amplifier 512. In some aspects, the EOM 508 may be configured to output a first laser beam along a common beam path 586. In some aspects, the EOM 508 may also be configured to output a second laser beam along the common beam path 586. In some aspects, the EOM 508 may include a first single-crystal EOM, a second single-crystal EOM, and a third single-crystal EOM. In some aspects, the EOM 508 may include a single-crystal EOM and a dual-crystal EOM. In some aspects, the EOM 508 may include a triple-crystal EOM.

[0117] In some aspects, the example laser system 500 may further include a first AOM 510 disposed along a common beam path 586 between the EOM 508 and the dual-channel amplifier 512. In some aspects, the first AOM 510 may be configured to receive a first laser beam from the EOM 508 along the common beam path 586. In some aspects, the first AOM 510 may also be configured to receive a second laser beam from the EOM 508 along the common beam path 586. In some aspects, the first AOM 510 may also be configured to output the first laser beam to the dual-channel amplifier 512 along the common beam path 586. In some aspects, the first AOM 510 may also be configured to output a second laser beam to the dual-channel amplifier 512 along the common beam path 586. In some aspects, the first AOM 510 may also be configured to output the first laser beam at a first diffraction angle. In some aspects, the first AOM 510 may also be configured to output the second laser beam at a second diffraction angle. In some respects, the second diffraction angle can be approximately equal to the first diffraction angle (e.g., as described above with reference to Equation 1).

[0118] In some aspects, the example laser system 500 may also include a second AOM 514 disposed along a common beam path 586. In some aspects, the second AOM 514 may be configured to receive a first laser beam from a dual-channel amplifier 512 along the common beam path 586. In some aspects, the second AOM 514 may also be configured to receive a second laser beam from the dual-channel amplifier 512 along the common beam path 586. In some aspects, the second AOM 514 may also be configured to generate a modified first laser beam based on a first wavelength of the first laser beam. In some aspects, the second AOM 514 may also be configured to generate a modified second laser beam based on a second wavelength of the second laser beam. Additionally or alternatively, in some aspects, the second AOM 514 may also be configured to generate a modified first laser beam based on a first rotation of the first polarization of the first laser beam, and a modified second laser beam based on a second rotation of the second polarization of the second laser beam, for example, to improve the efficiency of the second AOM 514. In some aspects, the second AOM 514 can also be configured to output a modified first laser beam to the dual-channel amplifier 512 along a common beam path 586. In some aspects, the second AOM 514 can also be configured to output a modified second laser beam to the dual-channel amplifier 512 along a common beam path 586. In some aspects, the dual-channel amplifier 512 can also be configured to perform dual-channel amplification of the first laser beam based on a first amplification of the first laser beam and a second amplification of the modified first laser beam. In some aspects, the dual-channel amplifier 512 can also be configured to perform dual-channel amplification of the second laser beam based on a third amplification of the second laser beam and a fourth amplification of the modified second laser beam.

[0119] In some aspects, the example laser system 500 may also include a laser isolation system 516 (e.g., optical isolation) disposed downstream of the dual-channel amplifier 512 along a common beam path 586. In some aspects, the laser isolation system 516 may be configured to receive a first laser beam amplified by the dual-channel amplifier 512 along the common beam path 586. In some aspects, the laser isolation system 516 may also be configured to receive a second laser beam amplified by the dual-channel amplifier 512 along the common beam path 586. In some aspects, the laser isolation system 516 may also be configured to generate an isolated first laser beam based on the dual-channel amplified first laser beam. In some aspects, the laser isolation system 516 may also be configured to generate an isolated second laser beam based on the dual-channel amplified second laser beam. In some aspects, the isolated first laser beam may include a first isolation factor greater than 10,000. In some aspects, the isolated second laser beam may include a second isolation factor greater than 10,000. In some respects, the laser isolation system 516 may include one or more Faraday isolators instead of AOM or EOM.

[0120] In some aspects, the laser isolation system 516 may include a third AOM 518 disposed downstream of the dual-channel amplifier 512 along the common beam path 586. Optionally, in some aspects, the laser isolation system 516 may also include a fourth AOM 520 disposed downstream of the third AOM 518 along the common beam path 586.

[0121] In some respects, the use of isolation, scintillation control, and periodic time-dependent gain extraction in the example laser system 500 can provide simplification of the example laser system 500 and stable operation of the dual-channel amplifier 512. In one exemplary example, the gain in the example laser system 500 can be very dynamic and change by a factor of approximately 3500 over a time period of approximately 20 microseconds (e.g., between two sequential pre-pulse laser beam pulses and between two sequential main pulse laser beam pulses). For example, for the main pulse laser beam, the gain in example laser system 500 begins with the gain extracted from the previous pulse, increases due to continuous RF pumping until it reaches a maximum small-signal gain (e.g., the gain including the dual-channel amplifier 512), decreases based on the gain extracted from the pre-pulse portion (e.g., the gain extracted from the main pulse laser beam due to reflection of the pre-pulse laser beam), increases again due to continuous RF pumping, decreases based on the gain extracted from the first main pulse portion (e.g., the gain extracted from the main pulse laser beam as it first passes through the dual-channel amplifier 512), increases again due to continuous RF pumping, and subsequently decreases based on the gain extracted from the second main pulse portion (e.g., the gain extracted from the main pulse laser beam as it passes through the dual-channel amplifier 512 for the second time). In some aspects, the effect of plasma reflection also affects the gain in example laser system 500.

[0122] In some respects, isolation, scintillation control, and gain extraction techniques may include, but are not limited to, extracting gain from the dual-channel amplifier 512 using: (i) the time-dependent gain characteristics before and after the pre-pulse laser beam and the main pulse laser beam; (ii) the distribution of gain, scintillation, and isolation along the optical path in the example laser system 500; (iii) isolation of the small-signal gain in the example laser system 500 relative to the small-signal gain in the example laser system 500; and (iv) an appropriate amount of isolation at a suitable location in the optical system of the example laser system 500.

[0123] Figure 6This is a schematic diagram of an example laser system 600 according to some aspects of this disclosure. In some aspects, the example laser system 600 may include a first laser source 602 (e.g., a CO2 pre-pulse seed laser source), a second laser source 604 (e.g., a CO2 main pulse seed source), a beam path combiner 606 (e.g., a DBS, TFP, beam multiplexer, or any other suitable optical structure or combination thereof), a first EOM 608 (e.g., a single-crystal EOM, a single-trigger EOM), an EOM system 609 (e.g., a dual-crystal EOM, a dual-trigger EOM), a first AOM 610, a dual-channel amplifier 612, a second AOM 614, and a polarization rotator 615. In some aspects, the EOM system 609 may include a second EOM (e.g., a single-crystal EOM, a single-trigger EOM), a third EOM (e.g., a single-crystal EOM, a single-trigger EOM), and a TFP pair disposed between the second and third EOMs. Additionally or alternatively, in some aspects, the example laser system 600 may include a reference... Figure 4 The laser system described 401, reference Figure 5 Example laser system 500 described, reference Figure 7 Example laser system 700 described, reference Figure 8 The example laser system 800 described herein may include any structure, technology, or feature described herein. In some aspects, the example laser system 600 may include one or more metrology or safety-related components, such as one or more polarization sensors, power sensors, spectrometers, attenuators (e.g., step attenuators, continuously variable attenuators), polarizers, filters, shielding elements, beam splitters, photoelectromagnetic sensors (PEM), photomultipliers (PM), metrology beam pickups, coatings (e.g., optical coatings), actuators (e.g., servo motors, servo controllers), any other suitable structures or components, and any combination thereof.

[0124] In some aspects, the first laser source 602 may be configured to generate a first laser beam (e.g., a pre-pulsed laser beam) traveling along a first beam path to mirrors 621 and 622 and beam path combiner 606. In some aspects, the second laser source 604 may be configured to generate a second laser beam (e.g., a main pulsed laser beam) traveling along a second beam path to mirror 623, waveplate 624 (e.g., a quarter-wave plate or half-wave plate), TFP 625a, TFP 625b and beam path combiner 606. In some aspects, the beam path combiner 606 may be configured to combine the first beam path with the second beam path to generate a common beam path 686 for both the first and second laser beams.

[0125] In some aspects, the first and second laser beams can travel along a common beam path 686 from the output of the beam path combiner 606 to the inputs of mirror 626, lens 627 (e.g., a 635 mm lens), and first EOM 608. In some aspects, the first and second laser beams can travel along a common beam path 686 from the output of first EOM 608 to the inputs of mirror 628, TFP 629a, TFP 629b, and EOM system 609. In some aspects, the first and second laser beams can travel along a common beam path 686 from the output of EOM system 609 to the inputs of TFP 630a, TFP 630b, lens 631 (e.g., a 300 mm lens), and first AOM 610.

[0126] In some aspects, the first and second laser beams can travel along a common beam path 686 from the output of the first AOM 610 to mirrors 632 and 633, lens 634 (e.g., a 600mm lens), mirror 635, lens 636 (e.g., a 1300mm lens), mirror 637, TFP 638, and the first input of the dual-channel amplifier 612. In some aspects, after the first pass through the dual-channel amplifier 612, the first and second laser beams can travel along the common beam path 686 from the first output of the dual-channel amplifier 612 to TFP 639, lens 640 (e.g., a 950mm lens), mirror 641, mirror 642, lens 643 (e.g., a 600mm lens), and the input of the second AOM 614.

[0127] In some aspects, the first and second laser beams can travel from the output of the second AOM 614 to the input of the polarization rotator 615. In some instances, the polarization rotator 615 can be configured to rotate the polarization of the first laser beam, the second laser beam, or both by any suitable degree of rotation, such as 90 degrees. For example, the first polarization of the first laser beam entering the input of the polarization rotator 615 can be P-polarized, and the second polarization of the first laser beam exiting the output of the polarization rotator 615 can be S-polarized. In another example, the third polarization of the second laser beam entering the input of the polarization rotator 615 can be P-polarized, and the fourth polarization of the second laser beam exiting the output of the polarization rotator 615 can be S-polarized. In some respects, the first and second laser beams can travel along a common beam path 686 from the output of the polarization rotator 615 to the second input of mirrors 644, 645, 646 (e.g., a -508mm lens), 647 (e.g., a 381mm lens), 648, 649, 650, TFP 639, and the dual-channel amplifier 612.

[0128] In some aspects, after passing through the dual-channel amplifier 612 for the second time, the first and second laser beams can propagate along a common beam path 686 from the second pass output of the dual-channel amplifier 612 to TFP 639, reflector 651, reflector 652, and reflector 653. In some aspects, after being reflected from reflector 653, the first and second laser beams can travel along the common beam path 686 to a laser isolation system comprising a third AOM and a fourth AOM.

[0129] Figure 7 This is a schematic diagram of a portion of an example laser system 700 according to some aspects of this disclosure. In some aspects, the example laser system 700 may include a first laser source 702 (e.g., a CO2 prepulse seed laser source), a second laser source 704 (e.g., a CO2 main pulse seed source), a beam path combiner 706 (e.g., a DBS, TFP, beam multiplexer, or any other suitable optical structure or combination of optical structures), a first EOM 708 (e.g., a single-crystal EOM, a single-trigger EOM), and an EOM system 709 (e.g., a dual-crystal EOM, a dual-trigger EOM), the EOM system 709 including a second EOM 754 (e.g., a single-crystal EOM, a single-trigger EOM) and a third EOM 756 (e.g., a single-crystal EOM, a single-trigger EOM). Additionally or alternatively, in some aspects, the example laser system 700 may include a reference... Figure 4 The laser system described 401, reference Figure 5 Example laser system 500 described, reference Figure 6 Example laser system 600 described, reference Figure 8 The example laser system 800 described herein, or any combination thereof, describes any structure, technology, or feature.

[0130] In some aspects, the first laser source 702 can be configured to generate a first laser beam (e.g., a pre-pulsed laser beam) traveling along a first beam path to the beam path combiner 706. In some aspects, the second laser source 704 can be configured to generate a second laser beam (e.g., a main pulsed laser beam) traveling along a second beam path to the waveplate 724 (e.g., a quarter-wave plate or half-wave plate), the TFP 725, and the beam path combiner 706. In some aspects, the beam path combiner 706 can be configured to combine the first beam path with the second beam path to generate a common beam path 786 for both the first and second laser beams.

[0131] In some aspects, the first and second laser beams can travel along a common beam path 786 from the output of the beam path combiner 706 to the input of the first EOM 708. In some aspects, the first and second laser beams can travel along a common beam path 786 from the output of the first EOM 708 to the inputs of TFP 729a, TFP 729b, and the EOM system 709. In some aspects, the first and second laser beams can travel along a common beam path 786 from the output of the EOM system 709 to TFP 730a and TFP 730b. In some aspects, after transmission through TFP 730b, the first and second laser beams can travel along a common beam path 786 to the AOM (e.g., see reference 1). Figure 5 The first AOM 510 described, reference Figure 6 The first AOM 610 described herein or any other suitable component.

[0132] In an exemplary example of the example architecture of EOM system 709, EOM system 709 may include a second EOM 754, TFP 755a, TFP 755b, and a third EOM 756. In some aspects, the input of EOM system 709 may correspond to a point along common beam path 786, located after the output of TFP 729b and before the input of the second EOM 754. In some aspects, the output of EOM system 709 may correspond to a point along common beam path 786, located after the output of the third EOM 756 and before the input of TFP 730a. In some respects, the first and second laser beams can travel along a common beam path 786 through the EOM system 709 in the following sections: (i) from the input of the second EOM 709 to the input of the second EOM 754; (ii) from the output of the second EOM 754 to the input of TFP 755a, TFP 755b and the third EOM 756; and (iii) from the output of the third EOM 756 to the output of the EOM system 709.

[0133] Figure 8This is a schematic diagram of a portion of an example laser system 800 according to some aspects of this disclosure. In some aspects, the example laser system 800 may include a first laser source 802 (e.g., a CO2 prepulse seed laser source), a second laser source 804 (e.g., a CO2 main pulse seed source), a first EOM 808 (e.g., a single-crystal EOM, a single-trigger EOM), a beam path combiner 806 (e.g., a DBS, TFP, beam multiplexer, or any other suitable optical structure or combination of optical structures), and an EOM system 809 (e.g., a dual-crystal EOM, a dual-trigger EOM), the EOM system 809 including a second EOM 854 (e.g., a single-crystal EOM, a single-trigger EOM) and a third EOM 856 (e.g., a single-crystal EOM, a single-trigger EOM). Additionally or alternatively, in some aspects, the example laser system 800 may include references... Figure 4 The laser system described 401, reference Figure 5 Example laser system 500 described, reference Figure 6 Example laser system 600 described, reference Figure 7 The example laser system 700 described herein, or any combination thereof, describes any structure, technology, or feature.

[0134] In some aspects, the first laser source 802 may be configured to generate a first laser beam (e.g., a pre-pulse laser beam) traveling along a first beam path to the beam path combiner 806. In some aspects, the second laser source 804 may be configured to generate a second laser beam (e.g., a main pulse laser beam) traveling along a second beam path to the first EOM 808, TFP 825a, TFP 825b, and the beam path combiner 806. In some aspects, the beam path combiner 806 may be configured to combine the first beam path with the second beam path to generate a common beam path 886 for both the first and second laser beams.

[0135] In some aspects, the first and second laser beams can travel along a common beam path 886 from the output of the beam path combiner 806 to the input of the EOM system 809. In some aspects, the first and second laser beams can travel along the common beam path 886 from the output of the EOM system 809 to TFP 830a and TFP 830b. In some aspects, after transmission through TFP 830b, the first and second laser beams can travel along the common beam path 886 to the AOM (e.g., see reference 1). Figure 5 The first AOM 510 described, reference Figure 6 The first AOM 610 described herein or any other suitable component.

[0136] In an exemplary example of the example architecture of EOM system 809, EOM system 809 may include a second EOM 854, TFP 855a, TFP 855b, and a third EOM 856. In some aspects, the input of EOM system 809 may correspond to a point along the common beam path 886, located after the output of beam path combiner 806 and before the input of the second EOM 854. In some aspects, the output of EOM system 809 may correspond to a point along the common beam path 886, located after the output of the third EOM 856 and before the input of TFP 830a. In some respects, the first and second laser beams can travel along a common beam path 886 through the EOM system 809 in the following sections: (i) from the input of the EOM system 809 to the input of the second EOM 854; (ii) from the output of the second EOM 854 to the input of TFP 855a, TFP 855b and the third EOM 856; and (iii) from the output of the third EOM 856 to the output of the EOM system 809.

[0137] Example process for amplifying a laser beam

[0138] Figure 9 This is an example method 900 for dual-channel amplification of a laser beam along a common beam path, according to some aspects or portions thereof of this disclosure. The operation described with reference to example method 900 can be performed by or according to, as described above with reference to Figure 1- Figure 8 and the following Figure 10 To perform any system, device, component, technology or combination thereof described.

[0139] At operation 902, the method may include generating a first laser beam (e.g., a pre-pulsed laser beam) having a first wavelength from a first laser source (e.g., first laser source 502, first laser source 602, first laser source 702, first laser source 802). In some aspects, the generation of the first laser beam may be achieved using suitable mechanical or other methods, and includes the generation according to the above-referenced Figure 1- Figure 8 and the following references Figure 10 Any aspect or combination of aspects described to generate the first laser beam.

[0140] At operation 904, the method may include performing dual-channel amplification of the first laser beam by dual-channel amplifiers (e.g., dual-channel amplifier 512, dual-channel amplifier 612) along common beam paths (e.g., common beam paths 586, 686, 786, 886). In some aspects, the dual-channel amplification of the first laser beam may be implemented using suitable mechanical or other methods, and includes, according to the above reference to FIG1- Figure 8 and the following references Figure 10 Any aspect or combination of aspects described is used to perform dual-channel amplification of the first laser beam.

[0141] At operation 906, the method may include generating a second laser beam (e.g., a main pulse laser beam) having a second wavelength from a second laser source (e.g., second laser source 504, second laser source 604, second laser source 704, second laser source 804). In some aspects, the generation of the second laser beam may be achieved using suitable mechanical or other methods, and includes, according to the above reference to Figure 1— Figure 8 and the following references Figure 10 Any aspect or combination of aspects described can be used to generate a second laser beam.

[0142] At operation 908, the method may include performing dual-channel amplification of the second laser beam along a common beam path by a dual-channel amplifier. In some aspects, the dual-channel amplification of the second laser beam may be implemented using suitable mechanical or other methods, and includes, according to reference Figure 1— Figure 8 and the following references Figure 10 Any aspect or combination of aspects described herein may be used to perform dual-channel amplification of the second laser beam.

[0143] Example computing system

[0144] The aspects of this disclosure can be implemented in hardware, firmware, software, or any combination thereof. The aspects of this disclosure can also be implemented as instructions stored on a machine-readable medium, which can be read and executed by one or more processors. A machine-readable medium can include any mechanism for storing or transmitting information in a machine-readable form (e.g., a computing device). For example, a machine-readable medium can include read-only memory (ROM); random access memory (RAM); disk storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagation signals (e.g., carrier waves, infrared signals, digital signals, etc.). Furthermore, firmware, software, routines, instructions, and combinations thereof can be described herein as performing certain actions. However, it should be understood that such descriptions are for convenience only, and such actions are actually generated by a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, or combinations thereof, and in doing so, cause an actuator or other device (e.g., a servo motor, a robotic device) to interact with the physical world.

[0145] Various aspects, for example, can use such as Figure 10 The example computing system 1000 shown is implemented by one or more computing systems, such as the example computing system 1000. The example computing system 1000 may be a special-purpose computer capable of performing the functions described herein, such as: [reference needed]. Figure 4 Laser controller 411 as described; Reference Figure 5Example laser system 500 described; Reference Figure 6 Example laser system 600 described; Reference Figure 7 Example laser system 700 described; Reference Figure 8 The example laser system 800 described; any other suitable system, subsystem, or component; or any combination thereof. The example computing system 1000 may include one or more processors (also referred to as a central processing unit or CPU), such as processor 1004. Processor 1004 is connected to communication infrastructure 1006 (e.g., a bus). The example computing system 1000 may also include multiple user input / output devices 1003, such as monitors, keyboards, pointing devices, etc., that communicate with communication infrastructure 1006 via multiple user input / output interfaces 1002. The example computing system 1000 may also include main memory 1008 (e.g., one or more main storage devices), such as random access memory (RAM). Main memory 1008 may include one or more levels of cache. Control logic (e.g., computer software) and / or data are stored in main memory 1008.

[0146] The example computing system 1000 may also include auxiliary storage 1010 (e.g., one or more auxiliary storage devices). Auxiliary storage 1010 may include, for example, a hard disk drive 1012 and / or a removable storage drive 1014. The removable storage drive 1014 may be a floppy disk drive, a magnetic tape drive, an optical disk drive, an optical storage device, a magnetic tape backup device, and / or any other storage device / drive.

[0147] The removable storage drive 1014 can interact with the removable storage unit 1018. The removable storage unit 1018 includes a computer-usable or readable storage device on which computer software (control logic) and / or data are stored. The removable storage unit 1018 can be a floppy disk, magnetic tape, optical disc, DVD, optical storage disc, and / or any other computer data storage device. The removable storage drive 1014 reads from and / or writes to the removable storage unit 1018.

[0148] According to some aspects, the auxiliary storage 1010 may include other means, tools, or other methods for allowing computer programs and / or other instructions and / or data to be accessed by the example computing system 1000. Such means, tools, or other methods may include, for example, a removable storage unit 1022 and an interface 1020. Examples of removable storage units 1022 and interfaces 1020 may include a program box and box interface (such as those found in video game devices), a removable memory chip (such as an EPROM or PROM) and associated socket, a memory stick and USB port, a memory card and associated memory card slot, and / or any other removable storage unit and associated interface.

[0149] The example computing system 1000 may also include a communication interface 1024 (e.g., one or more network interfaces). The communication interface 1024 enables the example computing system 1000 to communicate and interact with any combination of remote devices, remote networks, remote entities, etc. (individually and collectively referred to as remote device 1028). For example, the communication interface 1024 may allow the example computing system 1000 to communicate with the remote device 1028 via a communication path 1026, which may be wired and / or wireless, and may include any combination of LAN, WAN, Internet, etc. Control logic, data, or both may be transmitted to and from the example computing system 1000 via the communication path 1026.

[0150] The operations described in the foregoing aspects of this disclosure can be implemented in a wide variety of configurations and architectures. Therefore, some or all of the operations described in the foregoing aspects can be performed in hardware, software, or both. In some aspects, tangible non-transitory devices or articles of art include tangible non-transitory computer-usable or readable media on which control logic (software) is stored, also referred to herein as computer program products or program storage devices. This includes, but is not limited to, example computing system 1000, main memory 1008, secondary memory 1010, and removable storage units 1018 and 1022, and tangible articles embodying any combination of the foregoing. When executed by one or more data processing devices (such as computing system 1000), such control logic causes such data processing devices to operate as described herein.

[0151] Based on the teachings contained in this disclosure, it will be helpful to those skilled in the art to use methods different from those in this disclosure. Figure 10 It will be apparent from the data processing apparatus, computer system, and / or computer architecture shown that various aspects of this disclosure can be made and used. Specifically, various aspects of this disclosure can be operated using software, hardware, and / or operating system implementations different from those described herein.

[0152] While specific references may be made herein to the use of lithography equipment in IC manufacturing, it should be understood that the lithography equipment described herein may have other applications, such as the fabrication of integrated optical systems, magnetic domain memory, flat panel displays, LCDs, thin-film magnetic heads, and the guiding and inspection of patterns. Those skilled in the art will understand that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered synonymous with the more general terms “substrate” or “target portion,” respectively. Before or after exposure, the substrate mentioned herein may be processed in, for example, a tracking unit (typically a tool for applying a resist layer to the substrate and developing the exposed resist), a metering unit, and / or an inspection unit. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Furthermore, for example, to create multilayer ICs, the substrate may be processed more than once, such that the term “substrate” as used herein may also refer to a substrate that already contains multiple processed layers.

[0153] It should be understood that the wording or terminology used herein is for descriptive rather than limiting purposes, and that the terminology or terminology used herein should be interpreted by those skilled in the art based on the teachings herein.

[0154] As used in this article, the term "substrate" describes the material on which a layer of material is added. In some respects, the substrate itself may be patterned, and the material added on top of it may also be patterned, or left unpatterned.

[0155] The embodiments disclosed herein are illustrative and not limiting. Other suitable modifications and adaptations to various conditions and parameters commonly encountered in the art (which will be apparent to those skilled in the art) are within the spirit and scope of this disclosure.

[0156] While specific aspects of this disclosure have been described above, it should be understood that these aspects may be practiced in ways other than those described. The description is not intended to limit the embodiments of this disclosure.

[0157] It should be understood that the Detailed Description section (not the Background, Summary, and Abstract sections) is intended to interpret the claims. The Summary and Abstract sections may set forth one or more, but not all, exemplary embodiments conceived by (multiple) inventors, and are therefore not intended to limit the embodiments and the appended claims in any way.

[0158] The functional building blocks illustrated above, illustrating the implementation of specific functions and their relationships, describe some aspects of this disclosure. For ease of description, the boundaries of these functional building blocks are arbitrarily defined herein. Alternative boundaries can be defined as long as the specified functions and their relationships are properly executed.

[0159] The foregoing description of specific aspects of this disclosure will fully reveal the general nature of these aspects, enabling others to readily modify and / or adapt these specific aspects for various applications by applying the knowledge of those skilled in the art, without departing from the general concepts of this disclosure, and without requiring excessive experimentation. Therefore, based on the teachings and guidance presented herein, such adaptations and modifications are intended within the meaning and scope of equivalents of the disclosed aspects.

[0160] Other aspects of this disclosure are set forth in the following numbered clauses.

[0161] 1. A radiation source, comprising:

[0162] Laser system, including:

[0163] A first laser source is configured to generate a first laser beam;

[0164] A second laser source is configured to generate a second laser beam; and

[0165] The dual-channel amplifier is configured as follows:

[0166] Along the common beam path, perform dual-channel amplification of the first laser beam; and

[0167] A dual-channel amplification of the second laser beam is performed along the common beam path.

[0168] 2. The radiation source as described in Clause 1, wherein the first laser beam comprises a pre-pulsed laser beam.

[0169] 3. The radiation source as described in Clause 2, wherein the second laser beam comprises the main pulse laser beam.

[0170] 4. The radiation source as described in Clause 3, wherein the laser system is configured as follows:

[0171] A modified fuel target is generated by bombarding a fuel target with a pre-pulsed laser beam; and

[0172] A modified fuel target is bombarded with a master pulse laser beam to generate plasma in the plasma-forming region.

[0173] 5. The radiation source as described in Clause 1, wherein:

[0174] The laser system also includes an electro-optic modulator disposed between the second laser source and the dual-channel amplifier; and

[0175] The electro-optic modulator is configured as follows:

[0176] The first laser beam is output along the common beam path; and

[0177] A second laser beam is output along the common beam path.

[0178] 6. The radiation source according to Clause 5, wherein the electro-optic modulator comprises:

[0179] First single-crystal electro-optic modulator;

[0180] A second single-crystal electro-optic modulator; and

[0181] The third single-crystal electro-optic modulator.

[0182] 7. The radiation source according to Clause 5, wherein the electro-optic modulator comprises:

[0183] Single-crystal electro-optic modulator; and

[0184] Dual-crystal electro-optic modulator.

[0185] 8. The radiation source as described in Clause 5, wherein the electro-optic modulator includes a three-crystal electro-optic modulator.

[0186] 9. The radiation source as described in Clause 5, wherein:

[0187] The laser system also includes an acousto-optic modulator positioned along the common beam path between the electro-optic modulator and the dual-channel amplifier; and

[0188] The acousto-optic modulator is configured as follows:

[0189] The first laser beam is received from the electro-optic modulator along the common beam path;

[0190] The second laser beam is received from the electro-optic modulator along the common beam path;

[0191] The first laser beam is output to a dual-channel amplifier along the common beam path; and

[0192] The second laser beam is output to the dual-channel amplifier along the common beam path.

[0193] 10. The radiation source as described in Clause 9, wherein:

[0194] The acousto-optic modulator is also configured as follows:

[0195] The first laser beam is output at the first diffraction angle; and

[0196] The second laser beam is output at the second diffraction angle; and

[0197] The second diffraction angle is approximately equal to the first diffraction angle.

[0198] 11. The radiation source as described in Clause 1, wherein:

[0199] The first laser beam includes a first wavelength; and

[0200] The second laser beam includes a second wavelength that is different from the first wavelength.

[0201] 12. The radiation source as described in Clause 1, wherein:

[0202] The laser system also includes an acousto-optic modulator positioned along a common beam path; and

[0203] The acousto-optic modulator is configured as follows:

[0204] The first laser beam is received from the dual-channel amplifier along the common beam path;

[0205] The second laser beam is received from the dual-channel amplifier along the common beam path;

[0206] A modified first laser beam is generated based on the first wavelength of the first laser beam.

[0207] A modified second laser beam is generated based on the second wavelength of the second laser beam.

[0208] Along the common beam path, the modified first laser beam is output to a dual-channel amplifier; and

[0209] The modified second laser beam is output to the dual-channel amplifier along the common beam path.

[0210] 13. The radiation source as described in Clause 12, wherein:

[0211] The acousto-optic modulator is also configured as follows:

[0212] A first acoustic grating is generated based on a first radio frequency of a first radio wave, and the first acoustic grating is configured to diffract a first laser beam.

[0213] A second acoustic grating is generated based on a second radio frequency of a second radio wave, and the second acoustic grating is configured to diffract a second laser beam;

[0214] Based on a first acoustic grating, a first laser beam is output at a first diffraction angle; and

[0215] Based on the second acoustic grating, a second laser beam is output at a second diffraction angle;

[0216] The first mathematical product of the first wavelength and the first radio frequency is approximately equal to the second mathematical product of the second wavelength and the second radio frequency; and

[0217] The second diffraction angle is approximately equal to the first diffraction angle.

[0218] 14. The radiation source according to Clause 12, wherein the dual-channel amplifier is further configured to perform dual-channel amplification of the first laser beam based on:

[0219] First amplification of the first laser beam; and

[0220] The second amplification of the modified first laser beam; and

[0221] The dual-channel amplification of the second laser beam is performed based on the following:

[0222] The third amplification of the second laser beam; and

[0223] The fourth amplification of the modified second laser beam.

[0224] 15. The radiation source as described in Clause 1, wherein:

[0225] The laser system also includes a laser isolation system positioned downstream of the dual-channel amplifier along the common beam path; and

[0226] The laser isolation system is configured as follows:

[0227] Along the common beam path, the first laser beam, amplified by the dual channels, is received from the dual-channel amplifier;

[0228] Along the common beam path, a second laser beam, amplified by the dual-channel amplifier, is received;

[0229] Based on the first laser beam amplified by dual channels, an isolated first laser beam is generated; and

[0230] An isolated second laser beam is generated based on the second laser beam amplified by dual channels.

[0231] 16. The radiation source as described in Clause 15, wherein:

[0232] The isolated first laser beam includes a first isolation factor greater than 10,000; and

[0233] The isolated second laser beam has a second isolation factor of more than 10,000.

[0234] 17. The radiation source as described in Clause 15, wherein the laser isolation system includes an acousto-optic modulator disposed downstream of the dual-channel amplifier along a common beam path.

[0235] 18. The radiation source as described in Clause 1, wherein:

[0236] The first laser beam includes a first wavelength; and

[0237] The second laser beam includes a second wavelength greater than approximately the first wavelength.

[0238] 19. An apparatus comprising:

[0239] A first laser source is configured to generate a first laser beam;

[0240] A second laser source is configured to generate a second laser beam; and

[0241] The dual-channel amplifier is configured as follows:

[0242] Along the common beam path, perform dual-channel amplification of the first laser beam; and

[0243] A dual-channel amplification of the second laser beam is performed along the common beam path.

[0244] 20. A method comprising:

[0245] A first laser beam is generated from a first laser source;

[0246] A second laser beam is generated from a second laser source;

[0247] The first laser beam is amplified in two channels along the common beam path by a dual-channel amplifier; and

[0248] The second laser beam is amplified in two channels along the common beam path by a dual-channel amplifier.

[0249] The breadth and scope of this disclosure should not be limited by any of the foregoing exemplary aspects or embodiments, but should be defined solely by the appended claims and their equivalents.

Claims

1. A radiation source, comprising: Laser system, including: A first laser source is configured to generate a first laser beam; A second laser source is configured to generate a second laser beam; and The dual-channel amplifier is configured as follows: Along the common beam path, perform dual-channel amplification of the first laser beam; Along the common beam path, dual-channel amplification of the second laser beam is performed; and An acousto-optic modulator is disposed along the common beam path, the acousto-optic modulator being configured to: The first laser beam is received from the dual-channel amplifier along the common beam path; The second laser beam is received from the dual-channel amplifier along the common beam path; A modified first laser beam is generated based on the first wavelength of the first laser beam. A modified second laser beam is generated based on the second wavelength of the second laser beam; The modified first laser beam is output to the dual-channel amplifier along the common beam path; and The modified second laser beam is output to the dual-channel amplifier along the common beam path. The dual-channel amplifier is also configured to: The dual-channel amplification of the first laser beam is performed based on the following: First amplification of the first laser beam; and The modified second amplification of the first laser beam; and The dual-channel amplification of the second laser beam is performed based on the following: The third amplification of the second laser beam; and The fourth amplification of the modified second laser beam.

2. The radiation source according to claim 1, wherein the first laser beam comprises a pre-pulsed laser beam.

3. The radiation source according to claim 2, wherein the second laser beam comprises a main pulse laser beam.

4. The radiation source according to claim 3, wherein the laser system is configured as follows: The pre-pulsed laser beam is used to impinge on the fuel target to generate a modified fuel target; and The modified fuel target is struck with the main pulse laser beam to generate plasma in the plasma-forming region.

5. The radiation source according to claim 1, wherein: The laser system further includes an electro-optic modulator disposed between the second laser source and the dual-channel amplifier; and The electro-optic modulator is configured as follows: The first laser beam is output along the common beam path; and The second laser beam is output along the common beam path.

6. The radiation source according to claim 5, wherein the electro-optic modulator comprises: First single-crystal electro-optic modulator; Second single-crystal electro-optic modulator; as well as The third single-crystal electro-optic modulator.

7. The radiation source according to claim 5, wherein the electro-optic modulator comprises: Single-crystal electro-optic modulator; as well as Dual-crystal electro-optic modulator.

8. The radiation source according to claim 5, wherein the electro-optic modulator comprises a three-crystal electro-optic modulator.

9. The radiation source according to claim 5, wherein: The laser system further includes an acousto-optic modulator disposed between the electro-optic modulator and the dual-channel amplifier along the common beam path; and The acousto-optic modulator is configured to: The first laser beam is received from the electro-optic modulator along the common beam path; The second laser beam is received from the electro-optic modulator along the common beam path; The first laser beam is output to the dual-channel amplifier along the common beam path; as well as The second laser beam is output to the dual-channel amplifier along the common beam path.

10. The radiation source according to claim 9, wherein: The acousto-optic modulator is further configured to: The first laser beam is output at a first diffraction angle; and The second laser beam is output at a second diffraction angle; and The second diffraction angle is approximately equal to the first diffraction angle.

11. The radiation source according to claim 1, wherein: The first laser beam includes a first wavelength; and The second laser beam includes a second wavelength that is different from the first wavelength.

12. The radiation source according to claim 1, wherein: The acousto-optic modulator is further configured to: A first acoustic grating is generated based on a first radio frequency of a first radio wave, and the first acoustic grating is configured to diffract the first laser beam. A second acoustic grating is generated based on a second radio frequency of a second radio wave, and the second acoustic grating is configured to diffract the second laser beam. Based on the first acoustic grating, the first laser beam is output at a first diffraction angle; as well as Based on the second acoustic grating, the second laser beam is output at a second diffraction angle; The first mathematical product of the first wavelength and the first radio frequency is approximately equal to the second mathematical product of the second wavelength and the second radio frequency; and The second diffraction angle is approximately equal to the first diffraction angle.

13. The radiation source according to claim 1, wherein: The laser system further includes a laser isolation system disposed downstream of the dual-channel amplifier along the common beam path; and The laser isolation system is configured as follows: Along the common beam path, the first laser beam, amplified by the dual channels, is received from the dual-channel amplifier; Along the common beam path, a second laser beam amplified by the dual-channel amplifier is received; Based on the first laser beam amplified by dual channels, an isolated first laser beam is generated; as well as An isolated second laser beam is generated based on the second laser beam amplified by dual channels.

14. The radiation source according to claim 13, wherein: The isolated first laser beam includes a first isolation factor greater than 10,000 times; and The isolated second laser beam includes a second isolation factor greater than 10,000.

15. The radiation source of claim 13, wherein the laser isolation system includes an acousto-optic modulator disposed downstream of the dual-channel amplifier along the common beam path.

16. The radiation source according to claim 1, wherein: The first laser beam includes a first wavelength; and The second laser beam includes a second wavelength greater than approximately the first wavelength.

17. An apparatus comprising: A first laser source is configured to generate a first laser beam; A second laser source is configured to generate a second laser beam; The dual-channel amplifier is configured as follows: Along the common beam path, perform dual-channel amplification of the first laser beam; as well as Along the common beam path, dual-channel amplification of the second laser beam is performed; and An acousto-optic modulator is disposed along the common beam path, the acousto-optic modulator being configured to: The first laser beam is received from the dual-channel amplifier along the common beam path; The second laser beam is received from the dual-channel amplifier along the common beam path; A modified first laser beam is generated based on the first wavelength of the first laser beam. A modified second laser beam is generated based on the second wavelength of the second laser beam; The modified first laser beam is output to the dual-channel amplifier along the common beam path; as well as The modified second laser beam is output to the dual-channel amplifier along the common beam path. The dual-channel amplifier is also configured to: The dual-channel amplification of the first laser beam is performed based on the following: First amplification of the first laser beam; and The second amplification of the modified first laser beam; as well as The dual-channel amplification of the second laser beam is performed based on the following: The third amplification of the second laser beam; as well as The fourth amplification of the modified second laser beam.

18. A method comprising: A first laser beam is generated from a first laser source; A second laser beam is generated from a second laser source; The first laser beam is amplified in two channels along the common beam path by a dual-channel amplifier; The dual-channel amplifier performs dual-channel amplification of the second laser beam along the common beam path; An acousto-optic modulator positioned along the common beam path performs the generation of a modified first laser beam based on a first wavelength of the first laser beam. The acousto-optic modulator performs the generation of a modified second laser beam based on the second wavelength of the second laser beam; The dual-channel amplifier performs the dual-channel amplification of the first laser beam based on the following: First amplification of the first laser beam; as well as The second amplification of the modified first laser beam; as well as The dual-channel amplifier performs the dual-channel amplification of the second laser beam based on the following: The third amplification of the second laser beam; as well as The fourth amplification of the modified second laser beam.

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