Tapered capsule laser continuous plasma lamp

Abstract

A plasma lamp in a broadband plasma source for inspection tools is disclosed. The plasma lamp includes a plasma bulb configured to hold a gas and generate a plasma within the plasma bulb. The plasma bulb is formed of a material that is at least partially transparent to illumination from the pump laser and at least a portion of the broadband radiation emitted by the plasma. The plasma bulb includes a tapered bladder. The tapered bladder is configured to interrupt a plume rising from the plasma.

Description

[0001] CROSS REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 344,412, filed on May 20, 2022, entitled TAPERED POCKET LASER-SUSTAINED PLASMA LAMP, pursuant to 35 U.S.C. §119(e), the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates generally to broadband plasma lamps, and more particularly to broadband plasma lamps equipped with a plasma bulb having a conical capsule for controlling a convective environment within the plasma bulb. Background Art

[0004] As the demand for integrated circuits with increasingly smaller device features continues to increase, the need for improved illumination sources for inspecting these permanent devices continues to grow. One such illumination source includes a laser-sustained broadband plasma (BBP) source that is capable of producing high-power broadband light. A laser-sustained BBP light source operates by focusing laser radiation into a volume of gas contained within a gas containment vessel to excite the gas (e.g., argon or xenon) into a plasma state, which in turn emits broadband light.

[0005] The plume originating from the hot plasma in the BBP light source has a temperature of thousands of degrees Celsius. The lower density hot plume rises upward through the gas, accelerates, and impinges on the inner surface of the lamp. Typically, the hot plume rises to impinge directly on the upper surface of the discharge chamber of the lamp. This plasma convection plume phenomenon creates local hot spots that are difficult to adequately cool. Plasma lamps are typically formed of fused quartz, which is a very poor conductor of heat. Therefore, plasma lamps formed of fused quartz do not distribute heat effectively, making thermal management difficult. Therefore, it would be advantageous to provide a plasma lamp design that overcomes the shortcomings of previous approaches. Summary of the invention

[0006] A plasma lamp is disclosed. In an embodiment, the plasma lamp comprises a plasma bulb configured to contain a gas and generate a plasma within the plasma bulb. In an embodiment, the plasma bulb is formed of a material that is at least partially transparent to illumination from a pump laser and at least a portion of broadband radiation emitted by the plasma. In an embodiment, the plasma bulb comprises a conical capsule, wherein the conical capsule comprises at least one of a converging section or a diverging conical section and is configured to interrupt a plume rising from the plasma. In an embodiment, the plasma lamp is incorporated into a laser sustained plasma (LSP) broadband light source. In an embodiment, the LSP broadband light source is incorporated into a characterization system, such as, but not limited to, an inspection system or a metrology system.

[0007] A method of reducing heat transfer between a plasma and a plasma bulb in an LSP broadband light source is disclosed. In an embodiment, the method includes generating pump illumination. In an embodiment, the method includes directing a portion of the pump illumination into a plasma bulb to maintain a plasma within a body of the plasma bulb. In an embodiment, the method includes interrupting a portion of a plume rising from the plasma using a conical bladder of the plasma bulb to reduce heat transfer from the plasma to one or more walls of the plasma bulb. In an embodiment, the method includes collecting a portion of broadband light emitted from the plasma and directing the portion of the broadband light to one or more downstream applications.

[0008] It should be understood that both the foregoing summary and the following detailed description are exemplary and explanatory only and do not necessarily limit the present disclosure. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate the subject matter of the present disclosure. The description and the drawings together serve to explain the principles of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Many of the advantages of the present disclosure may be better appreciated by those skilled in the art by referring to the accompanying drawings.

[0010] Figure 1 A schematic diagram illustrating an LSP broadband light source 100 equipped with a conical capsule plasma lamp according to one or more embodiments of the present disclosure.

[0011] Figures 2A to 2D A series of simplified schematic diagrams illustrating a plasma bulb having a tapered capsule according to one or more embodiments of the present disclosure.

[0012] Figure 2E A simplified schematic diagram illustrating a plasma bulb having a multi-step tapered capsule in accordance with one or more embodiments of the present disclosure.

[0013] Figure 3A simplified schematic diagram illustrating a plasma bulb having one or more electrodes according to one or more embodiments of the present disclosure.

[0014] Figure 4A Cross-sectional views illustrating various types of shapes of a plasma bulb of a plasma lamp according to one or more embodiments of the present disclosure.

[0015] Figure 4B The present invention describes one or more embodiments of the present invention. Figure 4A A graph of a series of internal surface temperature profiles obtained with vertical distance across the plasma bulb depicted in FIG.

[0016] Figure 5 According to one or more embodiments of the present disclosure Figures 1 to 4B A simplified schematic diagram of an optical characterization system for an LSP broadband light source as described in any of the above.

[0017] Figure 6 According to one or more embodiments of the present disclosure Figures 1 to 4B A simplified schematic diagram of an optical characterization system for an LSP broadband light source as described in any of the above.

[0018] Figure 7 Description A flow chart depicts a method of reducing heat transfer between a plasma and a plasma bulb in a laser sustained plasma source according to one or more embodiments of the present disclosure. DETAILED DESCRIPTION

[0019] 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 specific embodiments and specific features thereof. The embodiments set forth herein are to be regarded as illustrative and not restrictive. It should be readily apparent to one of ordinary skill in the art that various changes and modifications in form and detail may be made without departing from the spirit and scope of the present disclosure.

[0020] Embodiments of the present disclosure are directed to plasma lamps having a plasma bulb design suitable for controlling the convective environment within the plasma lamp utilized within a light source of a broadband plasma inspection tool. Convection control protects the walls of the discharge chamber of the plasma bulb from excessive heating by an improved convective plume of plasma. This control is achieved by molding the upper portion of the discharge chamber into a tapered capsule shape with a wide neck (e.g., a capsule shape with converging and / or diverging tapered sections) to allow airflow to enter. Embodiments of the present disclosure are directed to a plasma bulb design that further spreads out the area above which the plume contacts the inner surface of the plasma bulb. For example, the tapered shape of the deep capsule provides additional distance from the plasma and the walls of the plasma bulb and ensures that the flow is interrupted and becomes disordered before contacting the bulb wall. The airflow is diffused and reduces the contact area between the plume and the bulb wall, thereby reducing heat transfer to the wall and thus reducing the operating temperature of the wall.

[0021] Figure 1 A schematic diagram illustrating an LSP broadband light source 100 according to one or more embodiments of the present disclosure. The LSP source 100 includes a plasma lamp 102. The plasma lamp 102 includes a plasma bulb 104 configured to contain a gas and generate a plasma 106 within the plasma bulb 104. In an embodiment, the plasma bulb 104 includes a conical capsule 108. The conical capsule 108 is configured to interrupt a plume rising from the plasma 106. The plasma bulb 104 is formed of a material that is at least partially transparent to illumination 109 from a pump source 110 and broadband radiation 112 emitted by the plasma 106.

[0022] The pump source 110 is configured to generate illumination 109 for maintaining the plasma 106 within the plasma bulb 104, which acts as an optical pump. For example, the pump source 110 may emit a laser illumination beam suitable for pumping the plasma 106. In an embodiment, the collector element 114 is configured to direct a portion of the optical pump 109 to the gas contained in the plasma bulb 104 to ignite and / or maintain the plasma 106. The pump source 110 may include any pump source known in the art that is suitable for igniting and / or maintaining a plasma. For example, the pump source 110 may include one or more lasers (e.g., pump lasers). The pump beam may include radiation of any wavelength or range of wavelengths known in the art, including but not limited to visible light, IR radiation, NIR radiation, and / or UV radiation. The collector element 114 (e.g., an ellipsoidal mirror) is configured to collect a portion of the broadband radiation 112 emitted from the plasma 106. The broadband radiation 112 emitted from the plasma 106 may be collected via one or more additional optics, such as a cold mirror 116, for use in one or more downstream applications, such as inspection, metrology, or lithography. The LSP light source 100 may include any number of additional optical elements, such as, but not limited to, a filter 118 or a homogenizer 120, for conditioning the broadband radiation 112 prior to the one or more downstream applications. The collector element 114 may collect one or more of the visible, NUV, UV, DUV, and / or VUV radiation emitted by the plasma 106 and direct the broadband light 112 to one or more downstream optical elements. For example, the collector element 114 may deliver the 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 lithography tool. In this regard, the broadband light 112 may be coupled to the illumination optics of the inspection tool, the metrology tool, or the lithography tool.

[0023] Figures 2A to 2D A series of conical capsule designs for use in a plasma bulb 104 of a plasma lamp 102 according to one or more embodiments of the present disclosure are described. Figures 2A to 2D , it is shown that the conical capsule of the present disclosure can be formed by a converging conical section or a combination of converging and diverging conical sections to provide interruption of the plume rising from the plasma.

[0024] Figure 2AA conical capsule plasma bulb 200 is illustrated having a conical capsule 202. The conical capsule plasma bulb 200 also includes a body 204. For example, the body 204 may include an elliptical segment. In an embodiment, the conical capsule 202 is integrated with the body 204 to interrupt the plume rising from the plasma before the plasma impinges on the top portion of the plasma bulb 200. In this embodiment, the conical capsule 202 includes a conical segment 206 having a non-uniform shape (e.g., the diameter across the capsule varies depending on the vertical position). It should be noted that the shape of the plasma bulb is not strictly limited to a conical shape. Rather, as Figure 2A The shapes shown in FIG. 1 may deviate slightly from a perfect conical section and include inward and / or outward curvature as desired. In alternative embodiments, such as Figure 2B , the conical capsule bulb 210 may include a conical capsule 212, and the wall 214 of the portion of the plasma bulb 210 that forms the conical capsule 212 may have a non-uniform thickness (e.g., the thickness of the wall varies depending on the vertical position). In an alternative embodiment, as shown in FIG. Figure 2C , the conical capsule bulb 220 may include a conical capsule 222 formed by a straight section 224 integrated with a narrowing conical section 226 (e.g., a converging conical section). In an alternative embodiment, as Figure 2D , the conical capsule bulb 230 may include a conical capsule 232 formed by a widening conical section 234 (e.g., a diverging conical section) integrated with a narrowing conical section 236 (e.g., a converging conical section). In alternative embodiments, as Figure 2E , the bulb may include a multi-step tapered capsule 240 and include a tapered capsule 242 formed by a series of steps 244. The steps 244 may be formed by a series of straight sections, with each successive section having a smaller diameter than the section below it.

[0025] Plasma bulbs 200-240 are shown without electrodes. It should be noted that this depiction should not be interpreted as limiting the scope of the present disclosure. Rather, in embodiments, each of plasma bulbs 200-240 may be manufactured with or without electrodes. Figure 3 A conical capsule plasma bulb 300 including an electrode 302 is illustrated in accordance with one or more embodiments of the present disclosure. In embodiments, the conical capsule plasma bulb 300 may include one electrode or multiple electrodes (eg, top and bottom electrodes). One or more electrodes may include a metal rod.

[0026] Generally speaking Figures 2A to 3, the transmissive portions of the plasma bulbs 102, 200, 210, 220, 230, 240, and 300 may be formed of any material known in the art to be at least partially transparent to the broadband light 112 and / or the pump light 109 generated by the plasma 106. In embodiments, one or more transmissive portions of the plasma bulb may be formed of any material known in the art to be at least partially transparent to VUV radiation, DUV radiation, UV radiation, NUV radiation, and / or visible light generated within the plasma bulb 104. Furthermore, one or more transmissive portions of the plasma bulb may be formed of any material known in the art to be at least partially transparent to IR radiation, visible light, and / or UV light from the pump source 110. In embodiments, one or more transmissive portions of the plasma bulb may be formed of any material known in the art to be transparent to both radiation from the pump source 110 (e.g., an IR source) and radiation emitted by the plasma 106 (e.g., VUV, DUV, UV, NUV radiation, and / or visible light). For example, one or more of the plasma bulbs described herein may be formed from fused quartz glass.

[0027] The plasma bulb may contain any selected gas known in the art to be suitable for generating a plasma upon absorption of pump illumination (e.g., argon, xenon, mercury, or the like). In embodiments, focusing pump illumination 109 from pump source 110 into a gas volume causes energy to be absorbed by the gas or plasma within the gas containment structure (e.g., through one or more selected absorption lines), thereby "pumping" the gas species so as to generate and / or maintain plasma 106. Source 100 may be utilized to initiate and / or maintain plasma 106 in a variety of gas environments. In embodiments, the gas used to initiate and / or maintain plasma 106 may include an inert gas (e.g., a noble gas or a non-noble gas) or a non-inert gas (e.g., mercury). In embodiments, the gas used to initiate and / or maintain plasma 106 may include a mixture of gases (e.g., a mixture of inert gases, a mixture of inert and non-inert gases, or a mixture of non-inert gases). For example, gases suitable for implementation in source 100 may include, but are not limited to, Xe, Ar, Ne, Kr, He, N2, H2O, O2, H2, D2, F2, CH4, CF6, one or more metal halides, halogens, Hg, Cd, Zn, Sn, Ga, Fe, Li, Na, Ar:Xe, ArHg, KrHg, XeHg, and any mixtures thereof. The present disclosure should be construed as extending to any gas suitable for maintaining a plasma within a plasma bulb.

[0028] Figure 4ACross-sectional views illustrating various types of shapes of plasma bulbs of plasma lamps according to one or more embodiments of the present disclosure. The various shapes depict a series of capsules that enhance plume flow and mix and spread the thermal energy from the plasma over a larger portion of the interior surface area of ​​the plasma bulb. Plasma bulb 402 does not include capsules and represents a baseline "control" plasma bulb.

[0029] Plasma bulbs 404 and 406 include cylindrical bladders with narrow and wide necks, respectively. Computational fluid dynamics (CFD) simulations show that for a given bladder length, the inner diameter of the "neck" of the bladder plays an important role in the plume flow dynamics inside the bladder. The narrow neck of bulb 404 disturbs the plume flow near the bladder entrance, thereby causing the plume to dissipate and break up. In contrast, the wide neck of 406 allows the hot plume to rise undisturbed through most of the bladder length until it reaches the top of the bladder. Plasma bulb 408 includes a tapered bladder with the same wide neck as plasma bulb 406. The tapered shape of the bladder of plasma bulb 408 ensures that the plume breaks up before reaching the topmost bulb surface. The tapered shape is also preferably streamlined for more efficient cooling by forced jets from above plasma bulb 408.

[0030] Figure 4B Graph 410 is illustrated depicting a series of internal surface temperature profiles 412-418 taken along the vertical distance of bulbs 402-408, respectively. Note that the internal temperature of the bulb is averaged circumferentially as a function of vertical distance along the vertical axis of the bulb. The control bulb 402 without the capsule exhibits the highest internal glass temperature when the plume normally strikes the top surface, creating a local hot spot at region I.

[0031] The plasma bulb with the deep capsule exhibits a temperature distribution in which the hottest zone has moved upward due to the plume flow dynamics. In the case of the plasma bulb 404 with a cylindrical capsule with a narrow neck, the plume interacts with the capsule boundary at region I, but the magnitude of the temperature as shown by curve 414 is much smaller than that of the control plasma bulb 402 shown in curve 412. However, it should be noted that the heat energy in the case of the plasma bulb 404 is dissipated over a small surface area, making it more difficult to effectively cool by external forced convection. In the case of the plasma bulb 406 with a wide neck, the plume travels through the capsule length but also creates a hot spot at the topmost surface at region II. Due to normal plume impact at the topmost curved surface, the hot zone temperature of the plasma bulb 406 as shown in curve 416 is higher than that of the plasma bulb 404 as shown in curve 414. In the case of the plasma bulb 408 with a tapered capsule, the wide neck enables the capture of the undisturbed plume into the capsule, and the tapered shape interrupts and dissipates the flow below region II, as supported by the temperature curve 418.

[0032] The conical shape deep capsule design of the plasma bulb 408 provides the most effective convection control within the plasma bulb, reducing convective heat transfer to the bulb wall compared to other designs, achieving the safest conditions for lamp operation. It should be noted that the scope of the present disclosure is not limited to Figure 4A The conical shape plasma bulb 408 of FIG. Rather, as previously discussed herein, the conical shape plasma bulb 408 represents one example of a conical plasma design. It should be recognized herein that the various conical designs of the present disclosure may provide the same or similar benefits as the conical shape designs previously outlined herein.

[0033] Generally speaking Figures 1 to 4B , the pump source 110 may include any laser system known in the art that is capable of acting as an optical pump for maintaining a plasma. For example, the pump source 110 may include any laser system known in the art that is capable of emitting radiation in the infrared, visible, and / or ultraviolet portions of the electromagnetic spectrum.

[0034] In an embodiment, the pump source 110 may include a laser system configured to emit continuous wave (CW) laser radiation. For example, the pump source 110 may include one or more CW infrared laser sources. In an embodiment, the pump source 110 may include one or more lasers configured to provide laser light to the plasma 106 at a substantially constant power. In an embodiment, the pump source 110 may include one or more modulated lasers configured to provide modulated laser light to the plasma 106. In an embodiment, the pump source 110 may include one or more pulsed lasers configured to provide pulsed laser light to the plasma. In an embodiment, the pump source 110 may include one or more diode lasers. In an embodiment, the pump source 110 may include an ion laser. In an embodiment, the pump source 110 may include one or more frequency conversion laser systems. In an embodiment, the pump source 110 may include a disk laser. In an embodiment, the pump source 110 may include a fiber laser. In an embodiment, the pump source 110 may include a broadband laser. In an embodiment, the pump source 110 may include one or more non-laser sources.

[0035] In an embodiment, the pump source 110 may include two or more light sources. In an embodiment, the pump source 110 may include two or more lasers. For example, the pump source 110 (or "source") may include a plurality of diode lasers. In an embodiment, each of the two or more lasers may emit laser radiation tuned to a different absorption line of a gas or plasma within the source 100.

[0036] The light collector element 114 may include any light collector element known in the art of plasma generation. For example, the light collector element 114 may include one or more elliptical reflectors, one or more spherical reflectors, and / or one or more parabolic reflectors. The light collector element 114 may be configured to collect any wavelength of broadband light from the plasma 106 known in the art of plasma-based broadband light sources. For example, the light collector element 114 may be configured to collect infrared, visible, UV, NUV, VUV, and / or DUV light from the plasma 106.

[0037] Figure 5 According to one or more embodiments of the present disclosure Figures 1 to 4B Schematic diagram of an optical characterization system 500 for an LSP broadband light source 100 as described in any one of (or any combination thereof).

[0038] It should be noted herein that the system 500 may include any imaging, inspection, metrology, lithography, or other characterization / manufacturing system known in the art. In this regard, the system 500 may be configured to perform inspection, optical metrology, lithography, and / or imaging on a sample 507. The sample 507 may include any sample known in the art, including but not limited to a wafer, a reticle / photomask, and the like. It should be noted that the system 500 may be incorporated into one or more of the various embodiments of the LSP broadband light source 100 described throughout the present disclosure.

[0039] In an embodiment, the sample 507 is disposed on a stage assembly 512 to facilitate movement of the sample 507. The stage assembly 512 may include any stage assembly 512 known in the art, including but not limited to an XY stage, an R-theta stage, and the like. In an embodiment, the stage assembly 512 is capable of adjusting the height of the sample 507 to maintain focus on the sample 507 during inspection or imaging.

[0040] In an embodiment, the illumination optics set 503 is configured to direct illumination from the broadband light source 100 to the sample 507. The illumination optics set 503 may include any number and type of optical components known in the art. In an embodiment, the illumination optics set 503 includes one or more optical elements, such as but not limited to one or more lenses 502, a beam splitter 504, and an objective lens 506. In this regard, the illumination optics set 503 may be configured to focus the illumination from the LSP broadband light source 100 onto the surface of the sample 507. The one or more optical elements 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.

[0041] In an embodiment, the light collection optics set 505 is configured to collect light reflected, scattered, diffracted, and / or emitted from the sample 507. In an embodiment, the light collection optics set 505, such as but not limited to a focusing lens 510, may direct and / or focus light from the sample 507 to a sensor 516 of a detector assembly 514. It should be noted that the sensor 516 and the detector assembly 514 may include any sensor and detector assembly known in the art. For example, the sensor 516 may include but is not limited to a charge coupled device (CCD) detector, a complementary metal oxide semiconductor (CMOS) detector, a time delay integration (TDI) detector, a photomultiplier tube (PMT), an avalanche photodiode (APD), and the like. Furthermore, the sensor 516 may include but is not limited to a line sensor or an electron bombardment line sensor.

[0042] In an embodiment, the detector assembly 514 is communicatively coupled to a controller 518 including one or more processors 520 and a memory medium 522. For example, the one or more processors 520 may be communicatively coupled to the memory 522, wherein the one or more processors 520 are configured to execute a set of program instructions stored on the memory 522. In an embodiment, the one or more processors 520 are configured to analyze the output of the detector assembly 514. In an embodiment, the set of program instructions is configured to cause the one or more processors 520 to analyze one or more characteristics of the sample 507. In an embodiment, the set of program instructions is configured to cause the one or more processors 520 to modify one or more characteristics of the system 500 in order to maintain focus on the sample 507 and / or the sensor 516. For example, the one or more processors 520 may be configured to adjust the objective lens 506 or the one or more optical elements 502 in order to focus the illumination from the LSP broadband light source 100 onto the surface of the sample 507. By way of another example, the one or more processors 520 may be configured to adjust the objective lens 506 and / or the one or more optical elements 502 in order to collect illumination from the surface of the sample 507 and focus the collected illumination onto the sensor 516 .

[0043] It should be noted that system 500 may be configured in any optical configuration known in the art, including but not limited to dark field configuration, bright field orientation, and the like.

[0044] Figure 6 A simplified schematic diagram illustrating an optical characterization system 600 arranged in a reflectometer and / or ellipsometer configuration according to one or more embodiments of the present disclosure. Figures 1 to 5 The various embodiments and components described may be interpreted as extending to Figure 6 System 600 may include any type of metering system known in the art.

[0045] In an embodiment, system 600 includes LSP broadband light source 100 , illumination optics set 616 , collection optics set 618 , detector assembly 628 , and controller 518 .

[0046] In this embodiment, broadband illumination from the LSP broadband light source 100 is directed to the sample 607 via an illumination optics set 616. In an embodiment, the system 600 collects the illumination emitted from the sample 607 via a collection optics set 618. The illumination optics set 616 may include one or more beam conditioning components 620 adapted to modify and / or condition the broadband light beam. For example, the one or more beam conditioning components 620 may include, but are not limited to, one or more polarizers, one or more filters, one or more beam splitters, one or more diffusers, one or more homogenizers, one or more apodizers, one or more beam shapers, or one or more lenses.

[0047] In embodiments, illumination optics set 616 may utilize first focusing element 622 to focus and / or direct a light beam onto sample 607 disposed on sample stage 612. Collection optics set 618 may include second focusing element 626 to collect illumination from sample 607 in embodiments.

[0048] In an embodiment, the detector assembly 628 is configured to capture illumination emitted from the sample 607 through the collection optical device group 618. For example, the detector assembly 628 can receive illumination reflected or scattered from the sample 607 (e.g., via specular reflection, diffuse reflection, and the like). By way of another example, the detector assembly 628 can receive illumination generated by the sample 607 (e.g., luminescence associated with absorption of a light beam and the like). It should be noted that the detector assembly 628 can include any sensor and detector assembly known in the art. For example, the sensor can include, but is not limited to, a CCD detector, a CMOS detector, a TDI detector, a PMT, an APD, and the like.

[0049] The collection optical device group 618 may further include any number of collection beam conditioning elements 630 for directing and / or modifying the illumination collected by the second focusing element 626, including but not limited to one or more lenses, one or more filters, one or more polarizers, or one or more phase plates.

[0050] System 600 may 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.

[0051] Descriptions of inspection / metrology tools suitable for implementation in various embodiments of the present disclosure are provided in the following patents: U.S. Patent No. 7,957,066, entitled “Split Field Inspection System Using Small Catadioptric Objectives,” issued on June 7, 2011; U.S. Patent No. 7,345,825, entitled “Beam Delivery System for Laser Dark-Field Illumination in a Catadioptric Optical System,” issued on March 18, 2018; U.S. Patent No. 5,999,310, entitled “Ultra-broadband UV Microscope Imaging System with Wide Range Zoom Capability,” issued on December 7, 1999; U.S. Patent No. 5,999,310, entitled “Surface Inspection System Using Laser Line Illumination with Two Dimensional Imaging,” issued on April 28, 2009. No. 7,525,649, titled “Dynamically Adjustable Semiconductor Metrology System,” issued on January 5, 2016; No. 9,228,943, titled “Dynamically Adjustable Semiconductor Metrology System,” issued on January 5, 2016; No. 5,608,526, titled “Focused Beam Spectroscopic Ellipsometry Method and System,” issued on March 4, 1997 to Piwonka-Corle et al.; and No. 6,297,880, titled “Apparatus for Analyzing Multi-Layer Thin Film Stacks on Semiconductors,” issued on October 2, 2001, the entire contents of each of which are incorporated herein by reference.

[0052] Figure 7A flow chart is illustrated depicting a method 700 of reducing heat transfer between a plasma and a plasma bulb in a laser sustained plasma source according to one or more embodiments of the present disclosure. In step 702, pump illumination is generated. In step 704, a portion of the pump illumination is directed into the plasma bulb to sustain the plasma within the body of the plasma bulb. In step 706, a portion of the plume rising from the plasma is interrupted using a conical bladder of the plasma bulb to reduce heat transfer from the plasma to one or more walls of the plasma bulb. In step 708, a portion of the broadband radiation emitted from the plasma is collected and then to one or more downstream applications.

[0053] It should be further considered that each of the embodiments of the method described above may include any other steps of any other method described herein.In addition, each of the embodiments of the method described above may be performed by any of the systems described herein.

[0054] Those skilled in the art will recognize that the components, operations, devices, objects, and the accompanying discussions described herein are used as examples for conceptual clarity, 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 categories. In general, the use of any specific example is intended to represent its category, and the failure to include specific components, operations, devices, and objects should not be considered limiting.

[0055] With respect to the use of substantially any plural and / or singular terms herein, those skilled in the art may translate from the plural to the singular and / or from the singular to the plural as is appropriate to the context and / or application. For clarity, the various singular / plural permutations are not explicitly set forth herein.

[0056] The themes described herein sometimes illustrate different components contained in or connected to other components. It should be understood that such depicted architectures are only exemplary, and in fact many other architectures that realize the same functionality can be implemented. In a conceptual sense, any arrangement of components to realize the same functionality is effectively "associated" so that the desired functionality is realized. Therefore, any two components combined to realize a specific functionality herein can be considered to be "associated" with each other so that the desired functionality is realized, 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 realize the desired functionality, and any two components that can be so associated can also be considered to be "coupleable" to each other to realize the desired functionality. Specific examples that can be coupled include but are not limited to components that can be physically matched and / or physically interacted and / or components that can wirelessly interact and / or wirelessly interact and / or components that can logically interact and / or components that can logically interact.

[0057] 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" 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 should further understand that if a specific number of introduced claim recitations is intended, then such intention will be expressly recited in the claim, and in the absence of such recitation, such intention is absent. For example, to aid understanding, the appended claims below 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 such introduced claim recitation to inventions containing only one such recitation, even when 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" or "an" should generally be construed to mean "at least one" or "one or more"); the same is true of the use of definite articles used 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 such recitation should generally be construed to mean at least the recited number (e.g., the mere recitation "two recitations" without other modifiers generally means at least two recitations or two or more recitations). Furthermore, in those instances where a convention similar to “at least one of A, B, and C, and the like” is used, generally speaking, such construction is contemplated in the sense that a person skilled in the art would understand the convention (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 a convention similar to “at least one of A, B, or C, and the like” is used, generally speaking, such construction is contemplated in the sense that a person skilled in the art would understand the convention (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 any transitional word and / or phrase (whether in the specification, claims or drawings) that presents two or more alternative terms should be understood to contemplate the possibility of including one, either or both of the terms.For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

[0058] It is believed that the present disclosure and its many attendant advantages will be understood from the foregoing description, and it should be appreciated that various changes may be made to the form, construction, and arrangement of components without departing from the disclosed subject matter or sacrificing all of its significant advantages. The described form is 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 plasma lamp, comprising: a plasma bulb configured to contain a gas and to generate a plasma within the plasma bulb, the plasma bulb being formed of a material at least partially transparent to illumination from a pump laser and to at least a portion of broadband radiation emitted by the plasma, Wherein the plasma bulb comprises a conical capsule, wherein the conical capsule includes at least one of a converging section or a diverging conical section.

2. The plasma lamp of claim 1, wherein the conical capsule is configured to interrupt a plume rising from the plasma.

3. The plasma lamp of claim 1, wherein the conical capsule inhibits heat transfer from the plasma to one or more walls of the plasma bulb.

4. The plasma lamp of claim 1, wherein the plasma bulb comprises a body.

5. The plasma lamp of claim 4, wherein the conical sac is integrated with the body to interrupt the plume rising from the plasma before the plasma impinges on a top portion of the plasma bulb. The plasma lamp of claim 4 , wherein the body comprises an elliptical segment.

7. The plasma lamp of claim 1, wherein the tapered section has a non-uniform shape.

8. The plasma lamp of claim 1, wherein the wall of the tapered section is non-uniform.

9. The plasma lamp of claim 1, wherein the tapered section comprises a straight section integrated with a narrowing tapered section.

10. The plasma lamp of claim 1, wherein the tapered section comprises a widening tapered section integrated with a narrowing tapered section.

11. The plasma lamp of claim 1 , further comprising one or more metal rods.

12. The plasma lamp of claim 1, wherein the bulb is electrodeless.

13. The plasma lamp of claim 1, further comprising: One or more electrodes are disposed within the bulb, the one or more electrodes being configured to initiate plasma generation within the bulb.

14. The plasma lamp of claim 1, wherein the gas contained within the gas containment structure comprises at least one Xe, Ar, Ne, Kr, He, N2, H2O, O2, H2, D2, F2, CF6, or a mixture of two or more Xe, Ar, Ne, Kr, He, N2, H2O, O2, H2, D2, F2, or CF6.

15. The plasma lamp of claim 1, wherein the glass material of the plasma bulb comprises a fused silica glass material.

16. A plasma lamp comprising: a plasma bulb configured to contain a gas and to generate a plasma within the plasma bulb, the plasma bulb being formed of a material at least partially transparent to illumination from a pump laser and to at least a portion of broadband radiation emitted by the plasma, The plasma bulb comprises a multi-step tapered capsule, wherein the multi-step tapered capsule comprises a series of narrowing step-shaped sections.

17. The plasma lamp of claim 16, wherein the multi-step conical capsule is configured to interrupt a plume rising from the plasma.

18. A laser continuous plasma light source, comprising: a plasma bulb configured to contain a volume of gas; a laser pump source configured to generate optical pumping to sustain a plasma within the plasma bulb; and a light collector element configured to collect at least a portion of the broadband light emitted from the plasma, wherein the plasma bulb is formed of a material at least partially transparent to illumination from a pump laser and at least a portion of the broadband radiation emitted by the plasma, wherein the plasma bulb comprises a tapered capsule, wherein the tapered capsule includes at least one of a converging section or a diverging tapered section.

19. The laser continuous plasma light source of claim 18, wherein the conical capsule is configured to interrupt a plume rising from the plasma.

20. A characterization system comprising: Laser continuous light source, comprising: a plasma bulb configured to contain a volume of gas; a laser pump source configured to generate optical pumping to sustain a plasma within the plasma bulb; a light collector element configured to collect at least a portion of the broadband light emitted from the plasma, wherein the plasma bulb is formed of a material at least partially transparent to illumination from a pump laser and at least a portion of the broadband radiation emitted by the plasma, wherein the plasma bulb comprises a tapered capsule, wherein the tapered capsule includes at least one of a converging section or a diverging tapered section; an illumination optics set configured to direct broadband light from the laser continuous light source to one or more samples; a set of collection optics configured to collect light emitted from the one or more samples; and Detector assembly.

21. The characterization system of claim 20, wherein the conical capsule is configured to interrupt a plume rising from the plasma.

22. A method comprising: Producing pump illumination; directing a portion of the pump illumination into a plasma bulb to sustain a plasma within a body of the plasma bulb; interrupting a portion of a plume rising from the plasma using a conical bladder to reduce heat transfer from the plasma to one or more walls of the plasma bulb, wherein the conical bladder comprises at least one of a converging section or a diverging conical section; and A portion of the broadband light emitted from the plasma is collected and directed to one or more downstream applications.

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