Laser sustained plasma source based on collisional liquid jets

Abstract

A laser-sustained broadband light source includes a gas containment structure and a plurality of jet nozzles. The jet nozzles are configured to direct a plurality of liquid jets of plasma-forming material in directions such that they collide with each other within the gas containment structure. The laser-sustained broadband light source further includes a laser pump source configured to generate an optical pump to sustain a plasma in the region of the gas containment structure at the collision points of the plurality of liquid jets; and a light collector element configured to collect broadband light emitted from the plasma.

Description

[0001] Cross Reference

[0002] This application claims priority to U.S. Provisional Application Serial No. 63 / 331,895, filed on April 18, 2022, the entirety of which is incorporated herein by reference. Technical Field

[0003] The present invention relates generally to plasma-based radiation sources, and more particularly to a laser-sustained plasma (LSP) broadband light source including multiple liquid jets to provide a stable high-density, low-velocity gas region within a low-density gas volume for LSP generation. Background Art

[0004] As the demand for integrated circuits with increasingly smaller device features continues to grow, the need for improved illumination sources for inspecting these ever-shrinking devices continues to grow. One such illumination source includes a laser-sustained plasma (LSP) radiation source. LSP light sources are capable of producing high-power, broadband light. LSP light sources operate by focusing laser radiation into a volume of gas, such as argon or xenon, to excite the gas into a plasma state capable of emitting light. This effect is often referred to as "pumping" the plasma.

[0005] The increase in the radiance of the LSP source requires maintaining the plasma in a high-pressure environment to achieve a higher gas density in the plasma region. Typical LSP sources based on high-density gases rely on high-pressure gas to achieve the required plasma density. For example, in a broadband plasma (BBP) source, the operating pressure is approximately 100 bar. High gas density can be achieved by using a high-pressure convection gas chamber volume or by using a high-pressure gas jet entering a low-pressure chamber volume. Flow fluctuations in the convection gas volume may cause plasma instability. Due to the need for large amounts of compressed gas, the solutions listed above also require additional safety management. In addition, due to the heating of the surrounding gas volume by the pump light, these plasmas may show limited brightness, thereby increasing the size of the plasma, and due to the fact that the absorbed light does not reach the center of the plasma, reducing the plasma temperature.

[0006] It has been proposed to use a liquid jet to provide a localized high-density gas delivered to the LSP. In this case, the LSP would burn near the surface of the liquid. The evaporating liquid rapidly expands into a low-pressure volume, providing a high-density gradient. The high local density and corresponding pressure cause rapid airflow through the plasma region, which can prevent the plasma from being sustained. To sustain the plasma in the supersonic airflow desired for such an arrangement, very high pump power (in excess of approximately 100 kW CW) is required.

[0007]

[0006] It would therefore be desirable to provide a system and method that addresses one or more of the shortcomings of previous approaches identified above. Summary of the Invention

[0008] According to one or more embodiments of the present disclosure, a laser-sustaining broadband light source is disclosed. In one embodiment, the light source comprises a gas containment structure. In one embodiment, the light source comprises a plurality of jet nozzles, wherein the plurality of jet nozzles are configured to direct a plurality of liquid jets to collide within the gas containment structure, wherein the plurality of liquid jets comprise a first liquid jet and at least a second jet. In one embodiment, the light source comprises a laser pump source configured to generate an optical pump to sustain a plasma at a collision point of the plurality of liquid jets in the region of the gas containment structure. In one embodiment, the light source comprises a light collector element configured to collect at least a portion of the broadband light emitted from the plasma. In one embodiment, the broadband light source can be incorporated into an optical characterization system, such as an optical inspection system or a metrology system.

[0009] According to one or more embodiments of the present disclosure, a method for broadband light generation is disclosed. In one embodiment, the method includes generating a plurality of liquid jets for collision within a gas containment structure, wherein the plurality of liquid jets include a first liquid jet and at least a second liquid jet. In one embodiment, the method includes generating an optical pump. In one embodiment, the method includes focusing the optical pump at a collision point of the plurality of liquid jets in a region of the gas containment structure to maintain a plasma in the region of the gas containment structure at the collision point of the plurality of liquid jets. In one embodiment, the method includes collecting a portion of the broadband light emitted from the plasma and delivering the portion of the broadband light to one or more optical elements external to the gas containment structure.

[0010] It should be understood that both the foregoing general description and the following detailed description are exemplary and illustrative only and do not necessarily limit the present disclosure. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the subject matter of the present disclosure. Together, the description and the drawings serve to illustrate the principles of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Those skilled in the art may better appreciate the numerous advantages of the present disclosure by referring to the accompanying drawings.

[0012] Figure 1A A simplified schematic diagram illustrating an LSP broadband light source having two liquid jets for supplying plasma generating material according to one or more embodiments of the present disclosure.

[0013] Figure 1BA conceptual diagram illustrating an LSP broadband light source having two liquid jets for supplying plasma generating material according to one or more embodiments of the present disclosure.

[0014] Figure 2 A simplified schematic diagram illustrating an LSP broadband light source with annular pump optics according to one or more embodiments of the present disclosure.

[0015] Figure 3 A simplified schematic diagram illustrating an optical characterization system implementing an LSP radiation source according to one or more embodiments of the present disclosure.

[0016] Figure 4 A flow chart depicting a method for generating broadband light is illustrated in accordance with one or more embodiments of the present disclosure. DETAILED DESCRIPTION

[0017] Reference will now be made in detail to the disclosed subject matter illustrated in the accompanying drawings. The present disclosure has been particularly shown and described with respect to certain embodiments and specific features thereof. The embodiments described herein are to be considered illustrative rather than restrictive. It will be readily apparent to those skilled in the art that various changes and modifications in form and details may be made without departing from the spirit and scope of the present disclosure.

[0018] Referring generally to Figures 1 to 4, a laser-sustained plasma (LSP) broadband light source having multiple impinging liquid jets is described according to one or more embodiments of the present disclosure. Embodiments of the present disclosure relate to an LSP broadband light source comprising two or more impinging high-density, high-velocity liquid jets in a low-gas-density environment. The impinging jets create a high-density, low-velocity, stable gas region at their collision point. The velocity at the collision point is near zero. At this collision point, the LSP can be generated by focusing the pump laser at this point. Having a near-zero velocity region helps ensure plasma sustainability at lower pump powers. Outside the high-pressure, low-velocity region, the gas expands freely. The outer region is the gas outflow region, characterized by lower gas density and increased velocity. The gas pressure drops rapidly depending on the distance from the collision point. For example, the pressure can drop from over 100 bar at the collision point of the jets to less than 20 bar within a few hundred microns (e.g., 200 to 500 microns) of the collision point. Even though the plasma is sustained in this peripheral region, due to the low gas density, the plasma is still optically thin, allowing efficient laser coupling to the central point of the plasma and also allowing light to be collected in these peripheral regions without reabsorption.

[0019] Figure 1AA simplified schematic diagram illustrating a broadband LSP light source 100 according to one or more embodiments of the present disclosure is shown. In an embodiment, the LSP broadband light source 100 includes a set of jet nozzles for generating a set of liquid jets to collide within a gas containment chamber 106. For example, the set of jet nozzles may include a first jet nozzle 102a and a second jet nozzle 102b for delivering target material jets 104a, 104b, respectively, to collide within a gas containment structure 106 (e.g., a chamber, lamp, or cell). The LSP source 100 may also include a laser pump source 108, a pump laser focusing optic 110, and a light collector element 120. It should be noted that Figure 1A The following describes a case where the gas containment structure 106 is a gas containment chamber. For the purposes of this disclosure, the gas containment structure will be referred to as the gas containment chamber 106. However, the scope of this disclosure should not be limited to chambers, as any gas containment vessel is within the scope of this disclosure. For example, the gas containment structure 106 may include, but is not limited to, a plasma chamber, a plasma cell, or a plasma lamp.

[0020] The LSP source 108 can be configured to generate a pump beam 112 that acts as an optical pump to sustain a plasma 116 at the collision point of the liquid jets 104a, 104b in the region of the chamber 106. The pump beam 112 can be focused by pump laser focusing optics 110. In an embodiment, the pump laser focusing optics 110 direct the pump beam 112 through a pump laser window 114 into the chamber 106 and focus the pump beam 112 to the collision point between the first liquid jet 104a and the second liquid jet 104b to generate and / or sustain the plasma 116. It should be noted herein that the pump laser focusing optics 110 can include any optical element known in the art for directing and / or focusing radiation, including but not limited to lenses, mirrors, prisms, polarizers, gratings, filters, or beam splitters.

[0021] The pump source 108 may include any pump source known in the art suitable for igniting and / or maintaining a plasma. For example, the pump source 108 may include one or more lasers (e.g., pump lasers). In one embodiment, the pump source 108 includes one or more continuous wave (CW) laser sources. For example, the pump source 108 may include one or more CW infrared laser sources. In one embodiment, the pump source 108 may include one or more pulsed lasers configured to provide pulsed laser light to the plasma 116. For example, the pump source 108 may include one or more pulsed lasers having a repetition rate greater than 50 kHz (e.g., greater than 100 kHz). In one embodiment, the pump source 108 may include a combination of one or more CW and one or more pulsed lasers.

[0022] The pump beam 112 may include radiation of any wavelength or range of wavelengths known in the art, including but not limited to infrared (IR) radiation, near infrared (NIR) radiation, ultraviolet (UV) radiation, visible radiation, or other radiation suitable for forming a plasma when incident on a suitable target material.

[0023] It is noted herein that, without departing from the spirit or scope of the present disclosure, the LSP broadband light source 100 may include one or more additional ignition sources for facilitating the creation of the plasma 116. For example, the chamber 106 may include one or more electrodes that may initiate and / or sustain the plasma 116.

[0024] In one embodiment, the broadband light 118 generated by the plasma 116 exits the chamber 106 through one or more apertures 122. For example, the light collector element 120 may be arranged to collect the broadband light 118 from the plasma 116 and, in turn, direct at least a portion of the collected broadband light through the one or more apertures 122. In one embodiment, the one or more apertures 122 include one or more windows (e.g., a material transparent to the broadband light). In one embodiment, the one or more apertures 122 are windowless and positioned in a wall of the chamber 106. The one or more apertures 122 may include, but are not limited to, holes, ports, outlets, vents, spaces, or any other opening that allows the broadband light 118 to exit the chamber 106 through a wall of the chamber 106, and may be windowed or windowless.

[0025] In one embodiment, the chamber 106 is fluidically coupled to a vacuum pump 126. In one embodiment, the pressure in the chamber 106 is maintained at a selected pressure. The vacuum pump 126 can remove gas (e.g., gas ejected from the plasma, buffer gas) from the chamber 106 to maintain the selected pressure in the chamber 106. It should be noted that the gas evacuation can be performed at the same rate as the total input flow from the jet. In addition, the pressure within the chamber 106 should be maintained at a sufficiently low level to reduce laser absorption around the plasma 116.

[0026] In one embodiment, the light collector element 120 includes one or more optical elements known in the art configured to collect the broadband light 118, including but not limited to one or more mirrors, one or more prisms, one or more lenses, one or more diffractive optical elements, one or more parabolic mirrors, one or more elliptical mirrors, and the like. It should be noted herein that the light collector element 120 can be configured to collect and / or focus the broadband light 118 generated by the plasma 116 for use in one or more downstream processes, including but not limited to imaging processes, inspection processes, metrology processes, photolithography processes, and the like. For example, the light collector element 120 can direct the broadband light 118 to a collection location 128. For example, the light collector element 120 can deliver infrared, visible, NUV, UV, DUV, and / or VUV radiation to downstream optical elements of any optical characterization system known in the art, such as, but not limited to, an inspection tool, a metrology tool, or a photolithography tool. In this regard, the broadband light 118 can be coupled to the illumination optics of an inspection tool, a metrology tool, or a lithography tool.

[0027] Figure 1B A conceptual diagram illustrating a broadband LSP light source 100 according to one or more embodiments of the present disclosure. Colliding jets 104a, 104b create a stable high-density, low-velocity region 130 at their collision point. Due to the jets' deflected individual momentum, the velocity of the gas in region 130 approaches zero. Having near-zero velocity helps ensure the persistence of plasma 116 at low pump powers. Outside of high-density, low-velocity region 130, the gas is free to expand into a gas outflow region 132, which is characterized by lower gas density and higher velocity.

[0028] In one embodiment, the gas pressure in the plasma 116 is between 50 and 500 bar. To achieve such pressures, the liquid jets 104a, 104b must have sufficient diameter and velocity. Such high pressures can be achieved at liquid jet velocities of approximately 50 to 200 m / s (e.g., 75 to 125 m / s). In one embodiment, the diameter of the jets 104a, 104b is 50 to 500 microns (e.g., 150 to 250 microns). The jets 104a, 104b can be completely evaporated by the heat and radiation from the plasma 116.

[0029] In an embodiment, the gas pressure drops rapidly depending on the distance from the collision point of the jets 104a, 104b. In this regard, the pressure can drop from over 100 bar to less than 20 bar within a few hundred microns (e.g., 200 to 500 microns) from the collision point. Furthermore, even if the plasma is maintained in this peripheral region, the plasma is still optically thin due to the low gas density, which allows for efficient laser coupling to the central region of the plasma 116 and also allows for light collection in the peripheral region of the plasma 116 without reabsorption of the broadband light 118.

[0030] Jets 104a and 104b may comprise any material suitable for generating a plasma. In one embodiment, the jets may comprise liquid jets of cryogenically cooled liquids. For example, the liquids may include, but are not limited to, liquid Ar, liquid Kr, liquid Xe, liquid N2, liquid CH4, liquid NH3, and the like. In one embodiment, the jets may comprise liquid jets maintained at room temperature. For example, the liquids may include, but are not limited to, liquid HO and the like. In one embodiment, one or more materials may be delivered as a solvent within a solute. For example, one or more salts (e.g., heavy metal salts) may be dissolved in a liquid (e.g., HO) and delivered to chamber 106 via jets 104a and 104b. In one embodiment, one or more materials may be delivered as a suspension within a liquid. For example, the suspension may include, but are not limited to, metals suspended in water, Xe suspended in liquid N2, and the like. In one embodiment, two or more materials may be delivered as a mixture. For example, the liquid mixture may include, but is not limited to, a mixture of Ar and Xe, a mixture of Ar, Kr, and Xe, and the like.

[0031] In an embodiment, the jets 104a, 104b may deliver a mixture of liquid and gas materials. For example, the jets 104a, 104b may include a gas-liquid mixture such as, but not limited to, Ar / Xe, Ar / Kr, and the like.

[0032] In an embodiment, the jets 104a, 104b may comprise a solid material. For example, the jets 104a, 104b may comprise solid H2O or solid Xe. It should be noted herein that solid jets may be employed in a lower pressure chamber that the liquid jets experience on their way to the collision point.

[0033] While much of the description has focused on describing an LSP source 100 having two jet nozzles 102a, 102b and two jets 104a, 104b, it should be noted herein that this description is provided for convenience and clarity only. It should be noted that the LSP source 100 is not limited to two jet nozzles and two jets, and that the LSP source 100 may include any number of jet nozzles and corresponding jets. For example, the LSP source 100 may include 2, 3, 4, 5, 6, 7, 8 (and so on) jet nozzles and corresponding jets.

[0034] Figure 2 A simplified schematic diagram illustrating a broadband LSP light source 100 according to one or more embodiments of the present disclosure. In this embodiment, the pump laser focusing optics 110 may include one or more annular optics. For example, the pump laser focusing optics 110 may include an annular mirror. For example, Figure 2As depicted in FIG, the pump laser focusing optics 110 may include an annular mirror positioned so that the center point of the mirror is co-located with the collision point between the first jet 104a and the second jet 104b. This arrangement will cause the pump laser from the pump source 108 (shown in FIG for clarity) to Figure 2 Pump illumination 112 (not shown) is directed to the collision point between the first jet 104a and the second jet 104b.

[0035] The generation of laser-sustained plasmas is also generally described in U.S. Patent No. 7,435,982, issued on October 14, 2008, which is incorporated herein by reference in its entirety. Plasma generation is also generally described in U.S. Patent No. 7,786,455, issued on August 31, 2010, which is incorporated herein by reference in its entirety. Plasma generation is also generally described in U.S. Patent No. 7,989,786, issued on August 2, 2011, which is incorporated herein by reference in its entirety. Plasma generation is also generally described in U.S. Patent No. 8,182,127, issued on May 22, 2012, which is incorporated herein by reference in its entirety. Plasma generation is also generally described in U.S. Patent No. 8,309,943, issued on November 13, 2012, which is incorporated herein by reference in its entirety. Plasma generation is also generally described in U.S. Patent No. 8,525,138, issued on February 9, 2013, which is incorporated herein by reference in its entirety. Plasma generation is also generally described in U.S. Patent No. 8,921,814, issued on December 30, 2014, which is incorporated herein by reference in its entirety. Plasma generation is also generally described in U.S. Patent No. 9,318,311, issued on April 19, 2016, which is incorporated herein by reference in its entirety. Plasma generation is also generally described in U.S. Patent No. 9,390,902, issued on July 12, 2016, which is incorporated herein by reference in its entirety. In a general sense, the various embodiments of the present disclosure should be interpreted as extending to any plasma-based light source known in the art.

[0036] Figure 3 A simplified schematic diagram illustrates an optical characterization system 300 implementing an LSP broadband light source 100 according to one or more embodiments of the present disclosure. In one embodiment, the system 300 includes the LSP light source 100, an illumination arm 303, a collection arm 305, a detector assembly 314, and a controller 318 including one or more processors 320 and a memory 322.

[0037] It should be noted herein that system 300 may include any imaging, inspection, metrology, lithography, or other characterization system known in the art. In this regard, system 300 may be configured to perform inspection, optical metrology, lithography, and / or any form of imaging on sample 307. Sample 307 may include any specimen known in the art, including, but not limited to, wafers, reticles, photomasks, and the like. It should be noted that system 300 may incorporate one or more of the various embodiments of LSP light source 100 described throughout this disclosure.

[0038] In one embodiment, the sample 307 is disposed on a stage assembly 312 to facilitate movement of the sample 307. The stage assembly 312 may include any stage assembly 312 known in the art, including but not limited to an XY stage, an R-theta stage, and the like. In one embodiment, the stage assembly 312 is capable of adjusting the height of the sample 307 during inspection or imaging to maintain focus on the sample 307.

[0039] In one embodiment, the illumination arm 303 is configured to direct the broadband light 118 from the LSP broadband light source 100 toward the sample 307. The illumination arm 303 may include any number and type of optical components known in the art. In one embodiment, the illumination arm 303 includes one or more optical elements 302, a beam splitter 304, and an objective lens 306. In this regard, the illumination arm 303 may be configured to focus the broadband light 118 from the LSP broadband light source 100 onto the surface of the sample 307. The one or more optical elements 302 may include any optical element or combination of optical elements known in the art, including but not limited to one or more mirrors, one or more lenses, one or more polarizers, one or more gratings, one or more filters, one or more beam splitters, and the like. It should be noted herein that the collection location 128 may include, but is not limited to, one or more of the optical element 302, the beam splitter 304, or the objective lens 306.

[0040] In one embodiment, system 300 includes a collection arm 305 configured to collect light reflected, scattered, diffracted, and / or emitted from sample 307. In one embodiment, collection arm 305 can direct and / or focus light from sample 307 to sensor 316 of detector assembly 314. It should be noted that sensor 316 and detector assembly 314 can include any sensor and detector assembly known in the art. Sensor 316 can include, but is not limited to, a CCD sensor or a CCD-TDI sensor. Furthermore, sensor 316 can include, but is not limited to, a line sensor or an electron bombardment line sensor.

[0041] In an embodiment, detector assembly 314 is communicatively coupled to controller 318, which includes one or more processors 320 and memory 322. For example, one or more processors 320 may be communicatively coupled to memory 322, wherein one or more processors 320 are configured to execute a set of program instructions stored on memory 322. In an embodiment, one or more processors 320 are configured to analyze the output of detector assembly 314. In an embodiment, the set of program instructions are configured to cause one or more processors 320 to analyze one or more characteristics of sample 307. In an embodiment, the set of program instructions are configured to cause one or more processors 320 to modify one or more characteristics of system 300 to maintain focus on sample 307 and / or sensor 316. For example, one or more processors 320 may be configured to adjust objective lens 306 or one or more optical elements 302 to focus broadband light 118 from LSP broadband light source 100 onto the surface of sample 307. By way of another example, the one or more processors 320 may be configured to adjust the objective lens 306 and / or the one or more optical elements 310 to collect illumination from the surface of the sample 307 and focus the collected illumination onto the sensor 316 .

[0042] It should be noted that system 300 can be configured in any optical configuration known in the art, including but not limited to a darkfield configuration, a brightfield orientation, and the like. System 300 can be configured as any type of metrology tool known in the art, such as but not limited to a spectroscopic ellipsometer with one or more illumination angles, a spectroscopic ellipsometer for measuring Mueller matrix elements (e.g., using a rotational compensator), a single-wavelength ellipsometer, an angle-resolved ellipsometer (e.g., a beam profile ellipsometer), a spectroscopic reflectometer, a single-wavelength reflectometer, an angle-resolved reflectometer (e.g., a beam profile reflectometer), an imaging system, a pupil imaging system, a spectral imaging system, or a scatterometer.

[0043] Additional details of various embodiments of the optical characterization system 300 are described in: U.S. Patent Publication No. 7,957,066 B2, entitled “Split Field Inspection System Using Small Catadioptric Objectives,” published on June 7, 2011; U.S. Patent Application Publication No. 2007 / 0002465, entitled “Beam Delivery System for Laser Dark-Field Illumination in a Catadioptric Optical System,” published on January 4, 2007; U.S. Patent No. 5,999,310, entitled “Ultra-broadband UV Microscope Imaging System with Wide Range Zoom Capability,” published on December 7, 1999; and U.S. Patent No. 5,999,310, entitled “Surface Inspection System Using Laser Line Illumination and Two-Dimensional Imaging,” published on April 28, 2009. and U.S. Patent No. 7,525,649, entitled “Illumination with Two Dimensional Imaging” by Wang et al.; U.S. Published Patent Application No. 2013 / 0114085, entitled “Dynamically Adjustable Semiconductor Metrology System,” published on May 9, 2013; U.S. Patent No. 5,608,526, entitled “Focused Beam Spectroscopic Ellipsometry Method and System,” published on March 4, 1997 by Piwonka-Corle et al.; and U.S. Patent No. 6,297,880, entitled “Apparatus for Analyzing Multi-Layer Thin Film Stacks on Semiconductors,” published on October 2, 2001 by Rosencwaig et al., each of which is incorporated herein by reference in its entirety.

[0044] The one or more processors 320 of the present disclosure may include any one or more processing elements known in the art. In this sense, the one or more processors 320 may include any microprocessor-type device configured to execute software algorithms and / or instructions. In an embodiment, the one or more processors 320 may be composed of a desktop computer, a mainframe computer system, a workstation, an image computer, a parallel processor, or other computer system (e.g., a networked computer) configured to execute a program configured to operate the system 300 and / or the LSP broadband light source 100, as described throughout this disclosure. It should be recognized that the steps described throughout this disclosure may be performed by a single computer system or, alternatively, by multiple computer systems. In general, the term "processor" may be broadly defined to encompass any device having one or more processing elements that execute program instructions from a non-transitory memory medium 322. Furthermore, different subsystems of the various systems disclosed may include processors or logic elements suitable for performing at least some of the steps described throughout this disclosure. Therefore, the above description should not be construed as limiting the present disclosure but rather merely illustrative.

[0045] The memory medium 322 may comprise any storage medium known in the art suitable for storing program instructions executable by the associated one or more processors 320. For example, the memory medium 322 may comprise a non-transitory memory medium. For example, the memory medium 322 may include, but is not limited to, read-only memory, random access memory, magnetic or optical storage devices (e.g., disks), tape, solid-state drives, and the like. In one embodiment, the memory 322 is configured to store one or more results and / or outputs of the various steps described herein. It should further be noted that the memory 322 may be housed in a common controller housing with the one or more processors 320. In alternative embodiments, the memory 322 may be remotely located relative to the physical location of the processors 320. For example, the one or more processors 320 may access remote storage (e.g., a server) accessible via a network (e.g., the Internet, an intranet, and the like). In one embodiment, the memory medium 322 maintains program instructions for causing the one or more processors 320 to perform the various steps described herein.

[0046] Figure 4 A flow chart depicting a method 400 for generating broadband light 118 in accordance with one or more embodiments of the present disclosure is described. It should be noted herein that the steps of method 400 may be implemented in whole or in part by the LSP broadband light source 100. However, it should be further recognized that method 400 is not limited to the LSP light source 100, as additional or alternative system-level embodiments may implement all or a portion of the steps of method 400.

[0047] In step 402, a set of liquid jets is generated and arranged to collide within a gas containment structure. In one embodiment, a plurality of liquid jet nozzles 102a, 102b deliver liquid jets 104a, 104b into a chamber 106 such that they collide at the plasma generation location. The jet nozzles 102a, 102b may be fluidically coupled to one or more material sources (e.g., volumes of liquid stored in one or more containers). For example, each jet nozzle 102a, 102b may be fluidically coupled to a single liquid container (not shown). By way of another example, each jet nozzle 102a, 102b may be fluidically coupled to separate, independent liquid containers. In this example, the jet nozzles 102a, 102b may provide jets of the same or different materials.

[0048] In step 404 , an optical pump is generated. In an embodiment, the pump source 108 generates laser illumination 112 that acts as an optical pump for the plasma 116 .

[0049] In step 406, an optical pump is focused onto a collision point of the plurality of liquid jets 104a, 104b in the region of the gas containment structure to sustain a plasma 116 at the collision point of the liquid jets in the region of the gas containment structure. For example, one or more pump focusing optics 110 may be used to focus pump illumination 112 through a window 114 and into the region of the chamber 106 at the collision point of the plurality of liquid jets 104a, 104b to sustain a plasma 116 at the collision point of the liquid jets 104a, 104b.

[0050] In step 408, a portion of the broadband light 118 is collected from the plasma 116. For example, the portion of the broadband light 118 may be collected and delivered through apertures 122 in the wall of the chamber 106 to one or more optical elements outside the chamber 106 at a collection location 128.

[0051] Those skilled in the art will recognize that for the sake of conceptual clarity, the components, operations, devices, objects, and accompanying discussions described herein are used as examples, and various configuration modifications are contemplated. Therefore, as used herein, the specific examples set forth and the accompanying discussions are intended to represent their more general class. In general, the use of any specific example is intended to represent its class, and the omission of specific components (e.g., operations), devices, and objects should not be considered limiting.

[0052] With respect to the use of substantially any plural and / or singular terms herein, those skilled in the art can translate from the plural to the singular and / or from the singular to the plural depending on the context and / or application. For clarity, various singular / plural arrangements are not explicitly set forth herein.

[0053] The subject matter described herein sometimes illustrates different components contained within or connected to other components. It should be understood that such depicted architectures are merely exemplary, and in fact many other architectures that achieve the same functionality can be implemented. In a conceptual sense, any component arrangement for achieving the same functionality is effectively "associated" so as to achieve the desired functionality. Therefore, any two components combined herein to achieve a specific functionality can be considered to be "associated" with each other so as to achieve the desired functionality, regardless of the architecture or intermediate components. Similarly, any two components so associated can also be considered to be "connected" or "coupled" to each other to achieve the desired functionality, and any two components that can be so associated can also be considered to be "coupleable" to each other to achieve the desired functionality. Specific examples of coupleable include, but are not limited to, physically compatible and / or physically interactive components, and / or wirelessly interactive and / or wirelessly interactive components, and / or logically interactive and / or logically interactive components.

[0054] In addition, it should be understood that the present invention is defined by the appended claims. Those skilled in the art will understand that, in general, the terms used herein and particularly in the appended claims (e.g., the body of the appended claims) are generally intended to be "open-ended" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "including but not limited to," and the like). Those skilled in the art will further understand that if a specific number of claim recitations is intended, such intention will be explicitly stated in the claims, and in the absence of such a statement, such intention does not exist. For example, to aid understanding, the following appended claims may contain the use of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed as implying that the introduction of a claim recitation by the indefinite article "a" or "an" limits any particular claim containing the introduced claim recitation to inventions containing only one such recitation, even if the same claim contains the introductory phrase "one or more" or "at least one" and an indefinite article such as "a" or "an" (e.g., "a" and / or "an" should generally be construed to mean "at least one" or "one or more"); the foregoing applies equally to the use of definite articles to introduce claim recitations. In addition, even if a specific number of introduced claim recitations is explicitly recited, those skilled in the art will recognize that the recitation should generally be construed to mean at least the recited number (e.g., the basic recitation of "two recitations" (without other modifiers) generally means at least two recitations or two or more recitations). Furthermore, in those instances where conventional expressions similar to “at least one of A, B, and C, and the like” are used, such construction is generally contemplated in the sense that one skilled in the art would understand the conventional expressions (e.g., “a system having at least one of A, B, and C” would include, but is not limited to, systems having only A, only B, only C, both A and B, both A and C, both B and C, and / or both A, B, and C, and the like). In those instances where conventional expressions similar to “at least one of A, B, or C, and the like” are used, such construction is generally contemplated in the sense that one skilled in the art would understand the conventional expressions (e.g., “a system having at least one of A, B, or C” would include, but is not limited to, systems having only A, only B, only C, both A and B, both A and C, both B and C, and / or both A, B, and C, and the like). Those skilled in the art will further understand that virtually any disjunctive conjunction and / or phrase, whether in the description, claims, or drawings, presenting two or more alternatives should be understood to contemplate the possibility of including one, either, or both of the items.For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

[0055] It is believed that the present disclosure and its many attendant advantages will be understood from the foregoing description, and it will be appreciated that various changes may be made in the form, construction, and arrangement of components without departing from the disclosed subject matter or sacrificing all of its material advantages. The forms described are illustrative only, and the appended claims are intended to cover and encompass such changes. Furthermore, it should be understood that the invention is defined by the appended claims.

Claims

1. A broadband light source, comprising: a gas containment structure; a plurality of jet nozzles, wherein the plurality of jet nozzles are configured to direct a plurality of liquid jets to collide within the gas containment structure, wherein the plurality of liquid jets include a first liquid jet and at least a second jet; a laser pump source configured to generate an optical pump to sustain a plasma at a collision point of the plurality of liquid jets in a region of the gas containment structure; and A light collector element is configured to collect at least a portion of the broadband light emitted from the plasma. 2 . The broadband light source of claim 1 , wherein the plurality of jet nozzles comprises two or more jet nozzles. 3 . The broadband light source of claim 2 , wherein the plurality of jet nozzles comprises three or more jet nozzles.

4. The broadband light source of claim 1, further comprising one or more pump focusing optics for focusing the optical pump into the gas containment structure to reach the collision point of the plurality of liquid jets.

5. The broadband light source of claim 4, wherein the one or more pump focusing optics comprise at least one of a lens or a mirror.

6. The broadband light source of claim 5, wherein the one or more pump focusing optics comprise one or more annular optical elements.

7. The broadband light source of claim 1, wherein the plurality of jet nozzles are fluidically coupled to one or more liquid sources.

8. The broadband light source of claim 1, wherein the high pressure region around the collision point is maintained at a pressure of at least 20 bar.

9. A broadband light source according to claim 8, wherein the low pressure region outside the high pressure region is maintained at a pressure of less than 20 bar.

10. The broadband light source of claim 1, wherein each of the plurality of jets has a diameter between 50 and 300 microns.

11. The broadband light source of claim 1 , wherein the velocity of each of the plurality of jets is between 10 m / s and 500 m / s.

12. The broadband light source of claim 1, wherein at least one of the plurality of liquid jets comprises a liquid jet of at least one of Ar, Kr, Xe, N2, H2O, CH4, and NH3.

13. The broadband light source of claim 1, wherein at least one of the plurality of liquid jets comprises a liquid jet of a material mixture.

14. The broadband light source of claim 1, wherein at least one of the plurality of liquid jets comprises a suspension of material in liquid.

15. The broadband light source of claim 1, wherein at least one of the plurality of liquid jets comprises a solvent containing a solute.

16. The broadband light source of claim 1, wherein the laser pump source comprises at least one of one or more CW lasers or one or more pulsed lasers.

17. The broadband light source of claim 1, wherein the gas containment structure comprises at least one of a plasma chamber, a plasma cell, or a plasma lamp.

18. A light source system comprising: A broadband light source comprising: a gas containment structure; a plurality of jet nozzles, wherein the plurality of jet nozzles are configured to direct a plurality of liquid jets to collide within the gas containment structure, wherein the plurality of liquid jets include a first liquid jet and at least one second jet; a laser pump source configured to generate an optical pump to maintain a plasma at a point of collision of the plurality of liquid jets in the region of the gas containment structure; and a light collector element configured to collect at least a portion of the broadband light emitted from the plasma; a set of illuminator optics configured to direct the broadband light from the light collector element to one or more samples; detector assembly; and A set of projection optics is configured to receive illumination from a surface of the one or more samples and direct the illumination from the one or more samples to the detector assembly.

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