Cone-shaped pocket laser-sustained plasma lamp

Abstract

A plasma lamp for use in a broadband plasma source of an inspection tool is disclosed. The plasma lamp includes a plasma bulb 200 configured to contain a gas within the plasma bulb 200 and generate a plasma. The plasma bulb 200 is formed from a material that is at least partially transparent to illumination from a pump laser and at least a portion of the broadband radiation emitted by the plasma. The plasma bulb 200 includes a conical pocket 202. The conical pocket 202 is configured to disrupt a plume rising from the plasma.

Description

[Technical field]

[0001] The present disclosure relates generally to broadband plasma lamps, and more particularly to a broadband plasma lamp with a plasma bulb having a conical pocket for controlling the convective environment within the plasma bulb. [Background technology]

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 63 / 344,412, entitled “TAPERED POCKET LASER-SUSTAINED PLASMA LAMP,” filed May 20, 2022, which is incorporated by reference in its entirety.

[0003] As the demand for integrated circuits with very small device features continues to grow, there is an increasing need for improved illumination sources used to inspect these very small devices. One such illumination source is the laser-sustained broadband plasma (BBP) source, which is capable of producing high-power broadband light. Laser-sustained BBP sources operate by focusing laser radiation into a volume of gas, e.g., argon or xenon, contained within a gas vessel, exciting the gas into a plasma state, which then emits broadband light. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent Application Publication No. 2021 / 0321508 [Patent Document 2] US Patent Application Publication No. 2016 / 0163516 Summary of the Invention [Problem to be solved by the invention]

[0005] The plume generated from the hot plasma in a BBP light source has a temperature of several thousand degrees Celsius. The relatively low density hot plume rises through the gas, accelerates, and impinges on the inner surface of the lamp. Typically, the hot plume rises and impinges directly on the top surface of the lamp's discharge chamber. This plasma convection plume phenomenon creates localized hot spot areas that are difficult to adequately cool. Plasma lamps are commonly formed from fused silica, which is a poor thermal conductor. As a result, plasma lamps formed from fused silica do not dissipate heat effectively, making thermal management difficult. It would therefore be advantageous to provide a plasma lamp design that overcomes the shortcomings of conventional approaches. [Means for solving the problem]

[0006] A plasma lamp is disclosed. In an embodiment, the plasma lamp includes a plasma bulb configured to trap a gas within the plasma bulb and generate a plasma. In an embodiment, the plasma bulb is formed from a material that is at least partially transparent to at least a portion of the illumination from a pump laser and the broadband radiation emitted by the plasma. In an embodiment, the plasma bulb includes a conical pocket, the conical pocket including at least one of a converging section or a diverging conical section, configured to disrupt 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 the plasma bulb such that a plasma is sustained within a body of the plasma bulb. In an embodiment, the method includes disrupting a portion of a plume rising from the plasma with a conical pocket in 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 the broadband light emitted from the plasma and directing a portion of the broadband light to one or more downstream applications.

[0008] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the present disclosure. The subject matter of the present disclosure is illustrated by the accompanying drawings, which are incorporated in and constitute a part of this disclosure and together with the description serve to explain the principles of the present disclosure.

[0009] The many advantages of the present disclosure may be better understood by those skilled in the art by reference to the following drawings. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of an LSP broadband light source 100 comprising a conical pocket plasma lamp in accordance with one or more embodiments of the present disclosure. [Figure 2A] 1A-1D are a series of simplified schematic diagrams of a plasma bulb having a conical pocket in accordance with one or more embodiments of the present disclosure. [Figure 2B] 1A-1D are a series of simplified schematic diagrams of a plasma bulb having a conical pocket in accordance with one or more embodiments of the present disclosure. [Figure 2C] 1A-1D are a series of simplified schematic diagrams of a plasma bulb having a conical pocket in accordance with one or more embodiments of the present disclosure. [Figure 2D]1A-1D are a series of simplified schematic diagrams of a plasma bulb having a conical pocket in accordance with one or more embodiments of the present disclosure. [Figure 2E] FIG. 2 is a simplified schematic diagram of a plasma bulb having a multi-stage tapered pocket in accordance with one or more embodiments of the present disclosure. [Diagram 3] FIG. 2 is a simplified schematic diagram of a plasma bulb having one or more electrodes in accordance with one or more embodiments of the present disclosure. [Figure 4A] 1A-1D are cross-sectional views of various types of shapes of plasma bulbs of plasma lamps in accordance with one or more embodiments of the present disclosure. [Figure 4B] 4B is a graph depicting a series of interior surface temperature curves taken along the vertical distance of the plasma bulb depicted in FIG. 4A in accordance with one or more embodiments of the present disclosure. [Diagram 5] FIG. 4C is a simplified schematic diagram of a light characterization system implementing the LSP broadband light source shown in any of FIGS. 1-4B, in accordance with one or more embodiments of the present disclosure. [Figure 6] FIG. 4C is a simplified schematic diagram of a light characterization system implementing the LSP broadband light source shown in any of FIGS. 1-4B, in accordance with one or more embodiments of the present disclosure. [Figure 7] FIG. 1 is a flow diagram illustrating a method for reducing heat transfer between a plasma and a plasma bulb in a laser-sustained plasma source in accordance with one or more embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Reference will now be made in detail to the disclosed subject matter, as illustrated in the accompanying drawings. The present disclosure has been particularly shown and described with reference to certain embodiments and detailed features thereof. The embodiments set forth herein are to be construed as illustrative and not limiting. It will be readily apparent to those skilled in the art that various changes and modifications in form and details may be made therein without departing from the spirit and scope of the present disclosure.

[0012] The embodiments of the present disclosure are directed to plasma lamps having plasma bulb designs suitable for controlling the convective environment within the plasma lamps utilized in the light sources of broadband plasma inspection tools. The convective control protects the walls of the discharge chamber of the plasma bulb from excessive heating by the improved convective plume of the plasma. This control is achieved by shaping the top of the exhaust chamber in the shape of a conical pocket with a wide neck to allow the gas flow to enter (e.g., a pocket shape with converging and / or diverging conical sections). The embodiments of the present disclosure are directed to plasma bulb designs that further increase the area where the plume contacts the inner surface of the plasma bulb. For example, a deep pocket conical shape adds distance between the plasma and the wall of the plasma bulb, ensuring that the flow breaks up and becomes chaotic before contacting the bulb wall. The flow spreads out, reducing the area of ​​contact between the plume and the bulb wall, reducing heat transfer to the wall and resulting in a lower operating temperature of the wall.

[0013] 1 shows a schematic diagram of an LSP broadband light source 100 in accordance with 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 trap a gas within the plasma bulb 104 and generate a plasma 106. In an embodiment, the plasma bulb 104 includes a conical pocket 108. The conical pocket 108 is configured to disrupt a plume rising from the plasma 106. The plasma bulb 104 is formed from 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.

[0014] The pump source 110 is configured to generate illumination 109 that acts as an optical pump to sustain the plasma 106 in the plasma bulb 104. For example, the pump source 110 can emit a beam of laser illumination 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 enclosed within the plasma bulb 104 to ignite and / or sustain the plasma 106. The pump source 110 can include any pump source known in the art suitable for igniting and / or sustaining a plasma. For example, the pump source 110 can include one or more lasers (e.g., pump lasers). The pump beam can include radiation of any wavelength or range of wavelengths known in the art, including, but not limited to, visible radiation, 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 can be collected via one or more additional optics (e.g., cold mirror 116) for use in one or more downstream applications (e.g., inspection, metrology, or lithography). The LSP light source 100 can include any number of additional optical elements, such as, but not limited to, a filter 118 or a homogenizer 120, to condition the broadband radiation 112 before one or more downstream applications. The collector element 114 can 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 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 lithography tool. In this regard, broadband light 112 may be coupled into the illumination optics of an inspection tool, a metrology tool, or a lithography tool.

[0015] 2A-2D show a series of conical pocket designs for use in the plasma bulb 104 of the plasma lamp 102 in accordance with one or more embodiments of the present disclosure. As shown in FIGs. 2A-2D, the conical pockets of the present disclosure can be formed by converging conical sections or a combination of converging and diverging conical sections to provide for the collapse of the plume rising from the plasma.

[0016] FIG. 2A shows a conical pocket plasma bulb 200 having a conical pocket 202. The conical pocket plasma bulb 200 also includes a body 204. For example, the body 204 may include an elliptical section. In an embodiment, the conical pocket 202 is integrated with the body 204 to disrupt the plume rising from the plasma before the plasma impacts the top of the plasma bulb 200. In this embodiment, the conical pocket 202 includes a conical section 206 having a non-uniform shape (e.g., the diameter of the pocket varies as a function of vertical position). It is noted that the shape of the plasma bulb is not strictly limited to a conical shape. Rather, the shape may deviate slightly from a perfect conical section as shown in FIG. 2A and may include inward and / or outward curvatures as desired. In an alternative embodiment, as shown in FIG. 2B, the conical pocket valve 210 may include a conical pocket 212, and the wall 214 of the portion of the plasma bulb 210 forming the conical pocket 212 may have a non-uniform thickness (e.g., the wall thickness varies as a function of vertical position). In an alternative embodiment, as shown in FIG. 2C, the conical pocket valve 220 may include a conical pocket 222 formed from a straight section 224 integrated with a narrowing conical section 226 (e.g., a converging conical section). In an alternative embodiment, as shown in FIG. 2D, the conical pocket valve 230 may include a conical pocket 232 formed from a widening section 234 integrated with a narrowing conical section 236 (e.g., a converging conical section). In an alternative embodiment, as shown in FIG. 2E, the valve may include a multi-step tapered pocket 240, and may include a tapered pocket 242 formed from a series of steps 244. The step 244 may be formed from a series of straight sections, with each successive section having a smaller diameter than the section below it.

[0017] The plasma bulbs 200-240 are shown without electrodes. It should be noted that this description should not be construed as limiting the scope of the present disclosure. Rather, in embodiments, each of the plasma bulbs 200-240 may be fabricated with or without electrodes. FIG. 3 illustrates a conical pocket plasma bulb 300 including an electrode 302, according to one or more embodiments of the present disclosure. In embodiments, the conical pocket plasma bulb 300 may include one electrode or multiple electrodes (e.g., a top electrode and a bottom electrode). One or more of the electrodes may comprise a metal rod.

[0018] 2A-3, the transmissive portions of the plasma bulbs 102, 200, 210, 220, 230, 240, and 300 may be formed from any material known in the art that is at least partially transmissive to the broadband light 112 generated by the plasma 106 and / or pump light 109. In embodiments, one or more of the transmissive portions of the plasma bulbs may be formed from any material known in the art that is at least partially transmissive to the VUV radiation, DUV radiation, UV radiation, NUV radiation, and / or visible light generated within the plasma bulb 104. Additionally, one or more of the transmissive portions of the plasma bulbs may be formed from any material known in the art that is at least partially transmissive to the 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 from any material known in the art that is transmissive to both radiation from the pump source 110 (e.g., an IR source) and radiation emitted by the plasma 106 (e.g., VUV radiation, DUV radiation, UV radiation, NUV radiation, and / or visible light). For example, one or more of the plasma bulbs described herein may be formed from fused silica glass.

[0019] The plasma bulb may contain any selected gas known in the art (e.g., argon, xenon, mercury, etc.) suitable for generating a plasma upon absorption of pump illumination. In an embodiment, focusing of pump illumination 109 from pump source 110 into a volume of gas causes absorption of energy (e.g., via one or more selected absorption lines) by the gas or plasma within the gas-containing structure, thereby "pumping" the gas species to generate and / or sustain the plasma 106. The light source 100 may be utilized to initiate and / or sustain the plasma 106 in a variety of gas environments. In an embodiment, the gas used to initiate and / or sustain the plasma 106 may include an inert gas (e.g., a noble or non-noble gas) or a non-inert gas (e.g., mercury). In an embodiment, the gas used to initiate and / or sustain the plasma 106 may include a mixture of gases (e.g., a mixture of multiple inert gases, a mixture of inert and non-inert gases, or a mixture of multiple non-inert gases). For example, suitable gases for implementation in light source 100 include Xe, Ar, Ne, Kr, He, N 2 , H 2 O, O 2 , H 2 , D 2 , F 2 , C.H. 4 , C.F. 6 The gases may include, but are not limited to, 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 to cover any gas suitable for sustaining a plasma in the plasma bulb.

[0020] 4A shows cross-sectional views of various types of shapes of plasma bulbs of a plasma lamp in accordance with one or more embodiments of the present disclosure. The various shapes depict the development of pockets that facilitate the flow of the plume and mix and spread the thermal energy from the plasma over a larger portion of the inner surface area of ​​the plasma bulb. Plasma bulb 402 does not include pockets and represents a baseline "control" plasma bulb.

[0021] Plasma bulbs 404 and 406 contain cylindrical pockets with narrow and wide necks, respectively. Computational fluid dynamics (CFD) simulations show that the inner diameter of the pocket's "neck" plays a significant role in the dynamics of the plume flow inside the pocket for a given pocket length. The narrow neck of bulb 404 disturbs the plume flow near the pocket entrance, causing the plume to dissipate and break up. In contrast, the wide neck of 406 allows the hot plume to rise undisturbed for most of the pocket's length until it reaches the top of the pocket. Plasma bulb 408 contains a conical pocket with the same wide neck as plasma bulb 406. The conical shape of the pocket of plasma bulb 408 ensures that the plume breaks up before it reaches the top surface of the bulb. The conical shape also has better streamlining, making cooling by the forced jet from above plasma bulb 408 more effective.

[0022] 4B shows a graph 410 depicting a series of interior surface temperature curves 412-418 taken along vertical distances of bulbs 402-408, respectively. Note that the bulb interior temperature is averaged circumferentially along the bulb's vertical axis as a function of vertical distance. The control valve 402 without the pocket exhibits the highest interior glass temperature because the plume typically impinges on the top surface, creating a localized hot spot in Region I.

[0023] The plasma bulb with the deep pocket shows a temperature distribution with the hottest region moving upward as a result of the plume flow dynamics. For the plasma bulb with the narrow neck cylindrical pocket 404, the plume interacts with the pocket boundary in region I, but the temperature magnitude shown in curve 414 is much smaller compared to the control plasma bulb 402 shown in curve 412. Note, however, that the thermal energy for the plasma bulb 404 is dissipated over a smaller surface area, making it more difficult to effectively cool by external forced convection. For the plasma bulb with the wide neck 406, the plume travels the length of the pocket, but also forms a hot spot region on the top surface in region II. Due to the normal plume impingement on the top curved surface, the hot region temperature of the plasma bulb 406 shown in curve 416 is higher than that of the plasma bulb 404 shown in curve 414. In the case of the plasma bulb 408 with a conical pocket, the wide neck allows for the entrapment of the undisturbed plume into the pocket, and the conical shape breaks up and dissipates the flow below region II, as evidenced by the temperature curve 418.

[0024] The conical deep pocket design of the plasma bulb 408 provides the most effective convection control within the plasma bulb, reducing convective heat transfer to the bulb walls compared to other designs, allowing for the safest conditions for lamp operation. It is noted that the scope of the present disclosure is not limited to the conical plasma bulb 408 of FIG. 4A. Rather, as previously discussed herein, the conical plasma bulb 408 illustrates an example of a conical plasma design. It is recognized herein that the various conical designs of the present disclosure may provide the same or similar advantages as the conical designs previously outlined herein.

[0025] 1-4B, pump source 110 may include any laser system known in the art capable of functioning as an optical pump to sustain a plasma. For example, pump source 110 may include any laser system known in the art capable of emitting radiation in the infrared, visible, and / or ultraviolet portions of the electromagnetic spectrum.

[0026] In embodiments, 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 embodiments, the pump source 110 may include one or more lasers configured to provide laser light at a substantially constant power to the plasma 106. In embodiments, the pump source 110 may include one or more modulated lasers configured to provide modulated laser light to the plasma 106. In embodiments, the pump source 110 may include one or more pulsed lasers configured to provide pulsed laser light to the plasma. In embodiments, the pump source 110 may include one or more diode lasers. In embodiments, the pump source 110 may include an ion laser. In embodiments, the pump source 110 may include one or more frequency converted laser systems. In embodiments, the pump source 110 may include a disk laser. In embodiments, the pump source 110 may include a fiber laser. In embodiments, the pump source 110 may include a broadband laser. In embodiments, the pump source 110 may include one or more non-laser light sources.

[0027] In embodiments, pump source 110 may include two or more optical sources. In embodiments, pump source 110 may include two or more lasers. For example, pump source 110 (or "pump sources") may include multiple diode lasers. In embodiments, each of the two or more lasers may emit laser radiation tuned to a different absorption line of the gas or plasma in pump source 100.

[0028] The collector element 114 may include any collector element known in the art of plasma generation. For example, the collector element 114 may include one or more ellipsoidal reflectors, one or more spherical reflectors, and / or one or more parabolic reflectors. The collector element 114 may be configured to collect broadband light of any wavelength known in the art of plasma-based broadband light sources from the plasma 106. For example, the collector element 114 may be configured to collect infrared light, visible light, ultraviolet light, NUV light, VUV light, and / or DUV light from the plasma 106.

[0029] FIG. 5 is a schematic diagram of a light characterization system 500 implementing the LSP broadband light source 100 illustrated in any of FIGS. 1-4B (or any combination thereof) in accordance with one or more embodiments of the present disclosure.

[0030] It is noted herein that system 500 may comprise any imaging, inspection, metrology, lithography, or other characterization / manufacturing system known in the art. In this regard, system 500 may be configured to perform inspection, optical metrology, lithography, and / or imaging on sample 507. Sample 507 may include any sample known in the art, including, but not limited to, wafers, reticles / photomasks, etc. It is noted that system 500 may incorporate one or more of the various embodiments of LSP broadband light source 100 described throughout this disclosure.

[0031] 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-θ stage, etc. In an embodiment, the stage assembly 512 may adjust the height of the sample 507 to maintain focus on the sample 507 during inspection or imaging.

[0032] In an embodiment, the set of illumination optics 503 is configured to direct illumination from the broadband light source 100 onto the sample 507. The set of illumination optics 503 may include any number and type of optical components known in the art. In an embodiment, the set of illumination optics 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 set of illumination optics 503 may be configured to focus 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.

[0033] In an embodiment, the collection optics set 505 is configured to collect light reflected, scattered, diffracted, and / or emitted from the sample 507. In an embodiment, the collection optics set 505, such as but not limited to a focusing lens 510, can direct and / or focus the 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 can include any sensor and detector assembly known in the art. For example, the sensor 516 can 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. Additionally, the sensor 516 can include, but is not limited to, a line sensor or an e-beam-illuminated line sensor.

[0034] 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, where the one or more processors 520 are configured to execute a set of program instructions stored in the memory 522. In an embodiment, the one or more processors 520 are configured to analyze an 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 to maintain focusing 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 one or more optical elements 502 to focus illumination from the LSP broadband light source 100 onto the surface of the sample 507. As another example, the one or more processors 520 may be configured to adjust the objective lens 506 and / or one or more optical elements 502 to collect illumination from the surface of the sample 507 and focus the collected illumination onto the sample 516.

[0035] 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 configurations, bright field configurations, and the like.

[0036] Figure 6 shows a simplified schematic block diagram of an optical characterization system 600 arranged in a reflectometry and / or ellipsometry configuration in accordance with one or more embodiments of the present disclosure. It should be noted that the various embodiments and components described with respect to Figures 1-5 can be extended to the system of Figure 6 and vice versa. System 600 may include any type of metrology system known in the art.

[0037] In an embodiment, system 600 includes LSP broadband light source 100 , an illumination optics set 616 , a collection optics set 618 , a detector assembly 628 , and a controller 518 .

[0038] In this embodiment, broadband illumination from LSP broadband light source 100 is directed to sample 607 via illumination optics set 616. In an embodiment, system 600 collects illumination emanating from sample 607 via collection optics set 618. Illumination optics set 616 may include one or more beam conditioning components 620 suitable for modifying and / or conditioning the broadband 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.

[0039] In an embodiment, the illumination optics set 616 may utilize a first focusing element 622 to focus and / or direct the beam onto a sample 607 disposed on the sample stage 612. In an embodiment, the collection optics set 618 may include a second focusing element 626 to focus the illumination from the sample 607.

[0040] In an embodiment, the detector assembly 628 is configured to capture illumination emanating from the sample 607 via the collection optics set 618. For example, the detector assembly 628 can receive illumination reflected or scattered from the sample 607 (e.g., by specular reflection, diffuse reflection, etc.). As another example, the detector assembly 628 can receive illumination generated by the sample 607 (e.g., emission associated with absorption of the beam, etc.). 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, etc.

[0041] The set of collection optics 618 may further include any number of collected beam adjusting 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.

[0042] 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 elements of a Mueller matrix (e.g., using a rotational compensator), a short-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 spectroscopic imaging system, or a scatterometer.

[0043] Descriptions of inspection / metrology tools suitable for implementation with various embodiments of the present disclosure can be found in U.S. Pat. No. 7,957,066, issued on June 7, 2011, entitled "Split Field Inspection System Using Small Catadioptric Objectives," U.S. Pat. No. 7,345,825, issued on March 18, 2018, entitled "Beam Delivery System for Laser Dark-Field Illumination in a Catadioptric Optical System," U.S. Pat. No. 5,999,310, issued on December 7, 1999, entitled "Ultra-broadband UV Microscope Imaging System with Wide Range Zoom Capability," U.S. Pat. No. 7,525,649, issued on April 28, 2009, entitled "Surface Inspection System Using Laser Line Illumination with Two Dimensional Imaging," U.S. Pat. No. 7,525,649, issued on January 5, 2016, entitled "Dynamically Adjustable Semiconductor Metrology No. 9,228,943, entitled "Focused Beam Spectroscopic Ellipsometry Method and System," by Piwonka-Corle et al., issued March 4, 1997; and U.S. Pat. No. 6,297,880, entitled "Apparatus for Analyzing Multi-Layer Thin Film Stacks on Semiconductors," issued October 2, 2001, all of which are incorporated herein by reference in their entireties.

[0044] FIG. 7 shows a flow diagram illustrating a method 700 for reducing heat transfer between a plasma and a plasma bulb in a laser-sustained plasma source in accordance with 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 so that a plasma is sustained within the body of the plasma bulb. In step 706, a portion of the plume rising from the plasma is disrupted by a conical pocket in 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 directed to one or more downstream applications.

[0045] It is further contemplated that each of the method embodiments described above may include any other step(s) of any other method described herein. Additionally, each of the method embodiments described above may be performed by any of the systems described herein.

[0046] Those skilled in the art will recognize that the components, operations, devices, objects, and accompanying discussion described herein are used as examples for conceptual clarity, and that various configuration modifications are contemplated. As a result, as used herein, the specific examples set forth and the accompanying discussion are intended to be representative of their more general classes. In general, the use of any specific example is intended to be representative of its class, and the absence of a specific component, operation, device, and object should not be construed as providing a limitation.

[0047] With respect to the use of substantially any plural and / or singular terminology herein, those of skill in the art can interpret the plural to singular and / or singular to plural as appropriate to the context and / or application, and the various singular / plural permutations have not been expressly set forth herein for the sake of clarity.

[0048] The subject matter described herein illustrates various components that are sometimes included within or connected to other components. It should be understood that such configurational manners depicted are merely exemplary, and that in fact many other configurational manners that achieve the same functionality can be implemented. In a conceptual sense, any configuration of components that achieves the same functionality is effectively "associated" such that the desired functionality is achieved. Thus, any two components that are combined herein to achieve a particular functionality can be considered to be "associated with" each other such that the desired functionality is achieved, regardless of the configurational manner or intervening components. Similarly, any two components so associated can also be considered to be "connected" or "coupled" to each other such that the desired functionality is achieved, and any two components so associateable can also be considered to be "couplable" to each other such that the desired functionality is achieved. Specific examples of being couplable include, but are not limited to, physically joinable and / or physically interacting components, and / or wirelessly interactable and / or wirelessly interacting components, and / or logically interacting and / or logically interacting components.

[0049] It should further be understood that the present invention is defined by the appended claims. In general, those skilled in the art will understand that the terms used herein, particularly in the appended claims (e.g., the body of the appended claims), are generally intended as "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," etc.). Those skilled in the art will further understand that if a specific number is intended in the introduced claim recitation, such intention will be expressly recited in the claim, and that in the absence of such recitation, no such intention exists. For example, as an aid to understanding, the following appended claims may include the use of the introductory phrases "at least one" and "one or more" to introduce the claim recitation. However, the use of such phrases should not be construed as suggesting that introducing a claim statement with the indefinite article "a" or "an" limits any particular claim containing the claim statement so introduced to an invention containing only one such statement, 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" and / or "an" should generally be construed to mean "at least one" or "one or more"). The same applies to the use of definite articles used to introduce claim statements. Moreover, those skilled in the art will recognize that when a particular number of claim statements introduced is explicitly stated, such a statement should generally be construed to mean at least the stated number (e.g., a minimal statement of "two statements" without other modifiers generally means at least two statements, or more than two statements).Furthermore, when a conventional expression similar to "at least one of A, B, and C, etc." is used, such a structure is generally intended in the sense that one of ordinary skill in the art would understand the conventional expression (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, etc.). When a conventional expression similar to "at least one of A, B, or C, etc." is used, such a structure is generally intended in the sense that one of ordinary skill in the art would understand the conventional expression (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, etc.). Those skilled in the art will further appreciate that virtually any disjunctive word and / or phrase presenting two or more alternative terms, whether in the specification, claims, or drawings, should be understood to contemplate the possibility of including one of those terms, either one of those terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

[0050] It will be believed that the present disclosure and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes in form, construction and arrangement of the elements may be made without departing from the disclosed subject matter or sacrificing all of its advantages. The described forms are merely illustrative, and it is intended that such modifications be embraced and included within the scope of the following claims. Moreover, it is to be understood that the invention is defined by the appended claims.

Claims

1. It is a plasma lamp, The plasma valve is configured to generate plasma by sealing a gas inside the plasma valve, and is formed of a material that is at least partially transparent to at least a portion of the illumination from the pump laser and the broadband radiation emitted from the plasma. Equipped with, A plasma lamp characterized in that the plasma valve comprises a conical pocket, the conical pocket including at least one of a converging section or an expanding conical section, and is configured to disturb a plume rising from the plasma.

2. A plasma lamp according to claim 1, characterized in that the conical pocket prevents heat transfer from the plasma to one or more walls of the plasma valve.

3. A plasma lamp according to claim 1, wherein the plasma bulb comprises a main body.

4. A plasma lamp according to claim 3, characterized in that the conical pocket is integrated with the main body such that it disturbs the plume rising from the plasma before the plasma collides with the top of the plasma valve.

5. A plasma lamp according to claim 3, wherein the main body comprises an elliptical section.

6. A plasma lamp according to claim 1, characterized in that the conical section has a non-uniform shape.

7. A plasma lamp according to claim 1, characterized in that the walls of the conical section are non-uniform.

8. A plasma lamp according to claim 1, characterized in that the conical section comprises a linear section integrated with a narrowing conical section.

9. A plasma lamp according to claim 1, characterized in that the conical section comprises a widening conical section integrated with a narrowing conical section.

10. A plasma lamp according to claim 1, further comprising one or more metal rods.

11. A plasma lamp according to claim 1, characterized in that the bulb is electrodeless.

12. A plasma lamp according to claim 1, One or more electrodes disposed within the valve, configured to initiate plasma generation within the valve. A plasma lamp characterized by further being equipped with [a certain feature].

13. The plasma lamp according to claim 1, wherein the gas enclosed in the gas enclosure structure is at least one kind of Xe, Ar, Ne, Kr, He, N ２ , H ２ O, O ２ , H ２ , D ２ , F ２ , CF ６ , or a mixture of two or more kinds of Xe, Ar, Ne, Kr, He, N ２ , H ２ O, O ２ , H ２ , D ２ , F ２ , or CF ６ and characterized in that it contains a mixture of these.

14. A plasma lamp according to claim 1, characterized in that the glass material of the plasma bulb includes a fused silica glass material.

15. It is a plasma lamp, The plasma valve is configured to generate plasma by sealing a gas inside the plasma valve, and is formed of a material that is at least partially transparent to at least a portion of the illumination from the pump laser and the broadband radiation emitted from the plasma. Equipped with, A plasma lamp characterized in that the plasma valve comprises a multi-stage tapered pocket, the multi-stage tapered pocket comprising a series of narrowing stepped sections, and configured to disturb the plume rising from the plasma.

16. A plasma valve configured to contain a certain volume of gas, A laser pump source configured to generate an optical pump for maintaining the plasma in the plasma valve, A laser-sustained plasma light source comprising: a focusing element configured to focus at least a portion of broadband light emitted from the plasma, wherein the plasma valve is formed of a material that is at least partially transparent to illumination from a pump laser and at least a portion of the broadband light emitted from the plasma, and the plasma valve comprises a conical pocket, the conical pocket including at least one of a converging section or an expanding conical section, configured to disrupt a plume rising from the plasma.

17. A characteristic evaluation system, A laser sustained light source, A plasma valve configured to contain a certain volume of gas, A laser pump source configured to generate a photopump for maintaining the plasma in the plasma valve, A laser-sustaining light source comprising: a focusing element configured to focus at least a portion of the broadband light emitted from the plasma, wherein the plasma valve is formed of a material that is at least partially transparent to illumination from a pump laser and at least a portion of the broadband light emitted by the plasma, and the plasma valve comprises a conical pocket, the conical pocket including at least one of a converging section or an expanding conical section, configured to disrupt a plume rising from the plasma, A set of illumination optics configured to guide broadband light from the aforementioned laser sustaining light source to one or more samples, A set of focusing optical systems configured to collect light emitted from one or more of the aforementioned samples, Detector assembly and A characteristic evaluation system characterized by comprising the following features.

18. To generate pump lighting, To maintain the plasma within the body of the plasma valve, a portion of the pump illumination is guided into the plasma valve, To reduce heat transfer from the plasma to one or more walls of the plasma valve, a portion of the plume rising from the plasma is disturbed by a conical pocket including at least one of a converging section or an expanding conical section. The process involves collecting a portion of the broadband light emitted from the plasma and directing a portion of the broadband light to one or more downstream applications. A method characterized by including the following.

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