Sapphire lamp for laser-maintained plasma broadband light source

Abstract

The invention discloses a laser maintained broadband light source. The light source may include a gas containment structure for plasma generation. The gas containment structure may include: a first portion formed from a first grade of sapphire; and a second portion formed of sapphire of a second grade. The first portion is coupled to one or more sections of the second portion of a second grade sapphire. The light source may include a sapphire-to-sapphire bond between the first grade sapphire of the first portion and the second grade sapphire of the second portion, thereby eliminating metal-to-sapphire braze and avoiding exposure of metal components to destructive UV and / or VUV light. The light source may include: a primary laser pump source configured to direct a primary pump beam into the gas containment structure to maintain a plasma; and a light collector element configured to collect broadband light emitted from the plasma.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 539,594, filed September 21, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to plasma-based broadband light sources, and more specifically, to high-power vacuum ultraviolet (VUV) laser-supplied plasma (LSP) light sources with sapphire-based lamps. Background Technology

[0004] Laser-supplied plasma (LSP) sources are widely used in broadband inspection tools used in semiconductor inspection and imaging. Generally, a near-infrared (NIR) continuous-wave (CW) pump laser is focused onto a container holding a gas, where a plasma is excited and sustained by the absorption of the pump laser radiation. This container can be a lamp (e.g., a glass bulb with or without electrodes for plasma excitation), a unit (e.g., an optomechanical assembly with transparent walls to allow laser and plasma radiation to enter and exit the unit), a chamber (e.g., a metal container with transparent windows for laser light input and plasma light output), or a similar combination. Various plasma containers have high internal pressures, reaching tens or exceeding one hundred atmospheres during operation. This high-pressure gas contained within the container is crucial for LSP operation. The plasma light is collected through the transparent walls or windows of the container and used as an illumination source for the inspection tool.

[0005] Various versions of such sources have been developed. Most of these sources are designed to operate in the visible (VIS) or ultraviolet (UV) spectral regions. When these sources are used to generate light in the vacuum ultraviolet (VUV) spectral region, and particularly in the range of about 125 nm to 150 nm, the choice of practical construction is relatively small and it is limited to relatively low pump power. A typical source for generating VUV light comprises a metal chamber with multiple windows that couple the laser light in and out of the chamber. In some cases, LSP sources utilize sapphire-based plasma units for plasma containment and generation. In such implementations, the connection between high-quality sapphire and the metal is fabricated via brazing. Thus, the metal material is located near the plasma. The proximity of the metal to the plasma creates difficulties in the thermal management of the source. For example, 12 kW of plasma radiation produces about 1 kW / cm². 2surface irradiance. This causes degradation of the brazing material and overheating of nearby metal components. Furthermore, if the metal components are moved further away from the plasma to alleviate the thermal management issues, then the system requires a larger number of high quality sapphire and additional anti-reflective (AR) coatings and sapphire surface polishing, significantly increasing the cost of the cell.

[0006] Accordingly, it would be desirable to provide a VUV broadband light source that overcomes the limitations outlined above. SUMMARY

[0007] A laser-sustained broadband light source is disclosed. In some aspects, the laser-sustained broadband light source includes a gas containment structure configured to house a gas. In some aspects, the gas containment structure includes a first portion formed of a first grade of sapphire and a second portion formed of a second grade of sapphire different from the first grade of sapphire. In some aspects, the first portion is coupled to one or more segments of the second portion of second grade sapphire. In some aspects, the light source includes a primary laser pump source, where the primary laser pump source is configured to direct a primary pump beam into the gas containment structure to sustain a plasma. In some aspects, the light source includes a collector element configured to collect at least a portion of broadband light emitted from the plasma.

[0008] A characterization system is disclosed. In some aspects, the characterization system includes a laser-sustained light source. In some aspects, the laser-sustained light source includes a gas containment structure configured to house a gas, where the gas containment structure includes a first portion formed of a first grade of sapphire and a second portion formed of a second grade of sapphire different from the first grade of sapphire, where the first portion is coupled to one or more segments of the second portion of second grade sapphire. In some aspects, the light source includes a primary laser pump source, where the primary laser pump source is configured to direct a primary pump beam into the gas containment structure to sustain a plasma, and a collector element configured to collect at least a portion of broadband light emitted from the plasma. In some aspects, the characterization system further includes a set of illumination optics configured to direct broadband light from the laser-sustained light source to one or more samples, a set of collection optics configured to collect light emanating from the one or more samples, and a detector assembly.

[0009] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the subject matter of the disclosure. The description, together with the drawings, serves to explain principles of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0010] The many advantages of the present disclosure can be better understood by references to the drawings in connection with the specific description of the embodiments.

[0011] Figure 1 A simplified schematic diagram of an LSP broadband light source including multiple grades of sapphire is illustrated in accordance with one or more embodiments of the present disclosure.

[0012] Figure 2A An assembled view of a gas containment structure including a first portion of a first grade of sapphire and a second portion of a second grade of sapphire is illustrated in accordance with one or more embodiments of the present disclosure.

[0013] Figure 2B A cross-sectional view of a gas containment structure including a first portion of a first grade of sapphire and a second portion of a second grade of sapphire is illustrated in accordance with one or more embodiments of the present disclosure.

[0014] Figure 2C An exploded view of a gas containment structure including a first portion of a first grade of sapphire and a second portion of a second grade of sapphire is illustrated in accordance with one or more embodiments of the present disclosure.

[0015] Figures 3A to 3C A series of shapes of a first portion of a first grade of sapphire is illustrated in accordance with one or more embodiments of the present disclosure.

[0016] Figures 4A to 4C A series of gas containment structures equipped with gas nozzles is illustrated in accordance with one or more embodiments of the present disclosure.

[0017] Figure 5 A gas containment structure including a sapphire flange is illustrated in accordance with one or more embodiments of the present disclosure.

[0018] Figures 6A to 6C A gas containment structure including a sapphire flange and an additional flange is illustrated in accordance with one or more embodiments of the present disclosure.

[0019] Figure 7 A gas containment structure including a terminated bulb is illustrated in accordance with one or more embodiments of the present disclosure.

[0020] Figure 8 A simplified schematic diagram of an optical characterization system incorporating an LSP broadband light source is illustrated in accordance with one or more embodiments of the present disclosure. DETAILED DESCRIPTION

[0021] Reference will now be made in detail to the disclosed subject matter, which is illustrated in the accompanying drawings. The present disclosure has been particularly shown and described with respect to certain embodiments and particular features thereof. The embodiments set forth herein are to be considered illustrative rather than limiting. Various changes and modifications can be made to the form and details of the disclosed subject matter without departing from the spirit and scope of the disclosure.

[0022] Reference is made generally to Figures 1 to 7 A sapphire-based VUV laser sustained plasma broadband light source is described in accordance with one or more embodiments of the disclosure.

[0023] Embodiments of the present disclosure relate to LSP broadband light sources that implement sapphire-based plasma cells constructed of different grades of sapphire material. Embodiments of the present disclosure utilize sapphire-to-sapphire bonding to directly bond a first sapphire portion of a first grade of sapphire (e.g., a UV grade or VUV grade sapphire) to a second sapphire portion (e.g., a lower quality sapphire) and / or a metallic component. For example, the first grade of sapphire can include a high quality optical grade sapphire capable of operating in the UV and VUV spectral range, while the second grade of sapphire can include a lower quality non-optical grade sapphire. Additional embodiments of the present disclosure include a first VUV grade sapphire section connected to a long non-VUV grade sapphire conduit (rather than a metallic conduit) to supply high pressure gas to the plasma lamp. This configuration avoids the need for metal-to-sapphire brazing and avoids metal-to-sapphire brazing exposure to UV light and high temperatures, resulting in improved mechanical stability of the light source. Various embodiments of the present disclosure allow non-sapphire elements to be moved away from highly damaging UV / VUV light and improve thermal performance of the light source due to the superior thermal conductivity of sapphire. This configuration results in a higher operating temperature range and easier lamp thermal management.

[0024] It should be noted that the various configurations discussed herein can be arranged in a flow-through configuration, a reverse vortex flow configuration, or a closed configuration.

[0025] Figure 1A schematic diagram illustrating an LSP broadband light source 100 according to one or more embodiments of the disclosure is shown. The LSP source 100 includes a plasma lamp (e.g., a plasma cell) including a gas containment structure 102. The gas containment structure 102 is configured to house a gas (e.g., Ar, Xe, or a mixture of gases) and to generate a plasma 106 within the gas containment structure 102. In embodiments, the gas containment structure 102 includes a first portion 108 formed of a first grade of sapphire and a second portion 111 formed of a second grade of sapphire that is different than the first grade of sapphire (e.g., a UV grade or a VUV grade). In embodiments, the first portion 108 is coupled to one or more segments of the second portion of the second grade of sapphire. The first portion 108 of the first grade of sapphire is at least partially transparent to illumination 109 from a pump source 110 and broadband radiation 112 emitted by the plasma 106.

[0026] The pump source 110 is configured to generate illumination 109 that serves as an optical pump for sustaining the plasma 106 within the gas containment structure 104. For example, the pump source 110 can emit a beam of laser illumination light suitable for pumping the plasma 106. In embodiments, a collector element 114 is configured to direct a portion of the optical pump to the gas housed in the gas containment structure 104 to excite and / or sustain the plasma 106. The pump source 110 can include any pump source known in the art suitable for exciting and / or sustaining a plasma. For example, the pump source 110 can include one or more lasers (e.g., pump lasers). In embodiments, the laser pump source 110 can include one or more continuous wave (CW) pump lasers and / or one or more pulsed lasers. For example, the laser pump source 106 can include, but is not limited to, a fiber laser, a thin-disk laser, a frequency-doubled laser, or a diode laser. The pump source can include a main pump source for sustaining the plasma and an excitation source for exciting the plasma. For example, the main pump source can include one or more CW pump lasers and the excitation source can include one or more pulsed lasers. Alternatively, the source 100 can include one or more electrodes for exciting the plasma.

[0027] The pump beam can 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 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 optical devices (e.g., a 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 prior to one or more downstream applications. The collector element 114 can collect one or more of 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, the broadband light 112 can be coupled to the illumination optics of an inspection tool, a metrology tool, or a lithography tool.

[0028] Figures 2A to 2C A schematic diagram illustrating a sapphire-based plasma cell 102 according to one or more embodiments of the present disclosure is shown. Figure 2A A top perspective view is shown. Figure 2B A cross-sectional view is shown. Figure 2C An exploded view is shown. In embodiments, the gas containment structure 102 includes a first portion 108 formed of a first grade of sapphire and a second portion 111 formed of a second grade of sapphire that is different than the first grade of sapphire. In embodiments, the first portion 108 is coupled to one or more segments 111a, 111b of the second portion of the second grade of sapphire. For example, the first portion 108 of the first grade of sapphire can be brazed to one or more segments 111a, 111b of the second portion of the second grade of sapphire. The second portion 111 of the second grade of sapphire can include a first segment 111a and a second segment 111b. In this regard, the first portion 108 of the first grade of sapphire can be brazed to the first segment 111a of the second portion of the second grade of sapphire and the second segment 111b of the second portion of the second grade of sapphire, thereby forming a flow-through path having a gas inlet and a gas outlet for circulating gas through the first portion 108.

[0029] In an embodiment, the gas containment structure 102 includes one or more metal conduits 113a, 113b. For example, one or more metal conduits 113a, 113b may be coupled to one or more segments 111a, 111b of a second portion of the second-grade sapphire. For example, a first metal conduit 113a may be coupled to a first segment 111a of the second portion of the second-grade sapphire, and a second metal conduit 113b may be coupled to a second segment 111b of the second portion of the second-grade sapphire. In this configuration, the metal conduits 113a, 113b are further removed from the plasma 106 due to the use of segments 111a, 111b of the second-grade sapphire, which reduces or eliminates metal exposure to high UV and / or high temperature conditions. The metal conduits 113a, 113b may be brazed to segments 111a, 111b of the second-grade (e.g., low-cost) sapphire. Metal conduits 113a and 113b can be connected to a high-pressure gas flow 115 (e.g., high-pressure flow such as Ar or Xe) that circulates through the gas containment structure.

[0030] In an embodiment, the first portion 108 of the first-grade sapphire comprises two or more segments coupled together to form the first portion 108. For example, as... Figure 2C As shown, a first portion 108 of a first-grade sapphire comprises a first side 108a and a second side 108b. For example, the first side 108a may be glued or otherwise adhered to the second side 108b to form a composite that functions as the first portion 108 of the first-grade sapphire. Once assembled, the first portion 108 of the first-grade sapphire is connected to one or more segments of a second portion of a second-grade sapphire. For example, first segments 111a and second segments 111b of the second portion of the second-grade sapphire may be coupled to the first portion 108 of the first-grade sapphire. In this respect, the first segments 111a and second segments 111b of the second portion of the second-grade sapphire serve as flanges to reinforce the mechanical coupling of the first sides 108a and 108b of the first portion 108 of the first-grade sapphire. It should be noted that the scope of this disclosure is not limited to the two components of the first portion 108 of the first-grade sapphire. It should be noted that the first portion 108 may be a single piece or a composite of any number (e.g., 1, 2, 3, 4, 5, 6, etc.) of components.

[0031] In embodiments, one or more surfaces of the first portion 108 of the first grade of sapphire are coated with one or more selected materials. For example, the first portion 108 of the first grade of sapphire can be coated with one or more anti-reflective coating materials. The anti-reflective coating can be deposited on the outer surfaces of the first portion 108 and / or on the inner surfaces of the first portion. It should be noted that constructing the first portion 108 of the first grade of sapphire allows for easier coating and / or polishing of the surfaces of the first portion 108, particularly the interior portion of the first grade of sapphire. In additional embodiments, the first portion 108 of the first grade of sapphire can be coated with one or more optical filtering materials to filter out light incident on or emitted from the plasma 106.

[0032] Figures 3A to 3C A range of shapes for the first portion 108 of the first grade of sapphire according to one or more embodiments of the disclosure is illustrated. It should be noted that the first portion 108 of the first grade of sapphire can assume any number of shapes. For example, the first portion 108 of the first grade of sapphire can include a cylindrical symmetric cross-section. It should be noted that any cylindrical symmetric cross-section can be used within the first portion 108 of the first grade of sapphire. In this regard, the shape of the first portion 108 of the first grade of sapphire can be selected such that it has cylindrical symmetry along the gas flow direction 115. Additionally, the first grade of sapphire can assume a custom shape / curvature in a direction perpendicular to the gas flow direction (i.e., the axis of symmetry) to reduce chromatic aberration and thereby improve the mechanical and optical performance of the light source 100. As Figure 3A As shown in FIG. 1 1 1, the first portion 108 of the first grade of sapphire can assume a simple cylindrical shape (e.g., a cylindrical tube). In this example, the first portion 108 can be sized to fit within the inner diameter of one or more segments 1 1 1 a, 1 1 1 b of the second portion of the second grade of sapphire (e.g., also a cylindrical tube). Alternatively, the first portion 108 can be sized to fit around the outer diameter of one or more segments 1 1 1 a, 1 1 1 b of the second portion of the second grade of sapphire.

[0033] As shown in FIG. 1 12, the first portion 108 of the first grade of sapphire can assume a compound cylindrical shape. In this example, the first portion 108 of the first grade of sapphire can have a stepped cross-sectional profile such that the outer step fits flush between segments 1 1 1 a, 1 1 1 b of the second grade of sapphire and the inner step extends beyond the opening to provide additional mechanical support to the light source 100. Figure 3B As shown in FIG. 1 13, the first portion 108 of the first grade of sapphire can include a cylinder with a spherical cross-section. It should be noted that any type of outwardly curved shape can be implemented within the first portion 108, such as but not limited to a spherical cross-section or an ellipsoidal cross-section. It should be noted that the scope of the disclosure is not limited to

[0034] Figure 3C As shown in FIG. 1 14, the first portion 108 of the first grade of sapphire can include a cylinder with a stepped cross-section. It should be noted that any type of outwardly curved shape can be implemented within the first portion 108, such as but not limited to a spherical cross-section or an ellipsoidal cross-section. It should be noted that the scope of the disclosure is not limited to Figures 3A to 3C ​The depicted example and can implement any shape having one or more cylindrical symmetric cross sections within the first portion 108 and / or the second portion 111 of the light source 100.

[0035] Figures 4A to 4C A series of gas containment structures 102 equipped with a gas nozzle is illustrated in accordance with one or more embodiments of the disclosure. In this embodiment, the gas containment structure 102 can include a gas nozzle 402. The gas nozzle 402 can be positioned along the high pressure gas flow 115 and located at the entrance of the plasma formation region. In embodiments, the gas nozzle 402 can be formed as an integral piece of the first portion 108 of the first grade sapphire. In this manner, the nozzle 402 and the first portion 108 form a single integral piece. Alternatively, the gas nozzle 402 can be formed as a separate piece (e.g., first grade sapphire, second grade sapphire, or another material) and coupled (e.g., glued) to the first portion 108 of the first grade sapphire. It should be noted that the nozzle 402 can be formed from the first grade sapphire (e.g., VUV grade sapphire) or the second grade sapphire based on the nozzle positioning and shape. Alternatively, the nozzle 402 can be formed from a non-sapphire material (e.g., but not limited to, metal, quartz, or glass) depending on the operational parameters of the source.

[0036] Figure 5 A gas containment structure 102 including a sapphire flange is illustrated in accordance with one or more embodiments of the disclosure. In embodiments, the gas containment structure 102 can include a cylindrical symmetric tube 111 of the second grade sapphire coupled to the first grade sapphire on a first end of the first grade tube 108. Additionally, the gas containment structure 102 can include a sapphire flange 502 coupled to the first grade of sapphire on a second end of the first grade tube 108. In this example, the gas containment structure 102 can be configured as a closed or open volume. For example, the second portion 111 of the second grade sapphire can be coupled to a metal tube 113 for receiving the high pressure gas flow 115. This arrangement can be used to build a reverse vortex gas flow.

[0037] Figures 6A to 6C A gas containment structure including a sapphire flange and an additional flange to form a closed volume is illustrated in accordance with one or more embodiments of the disclosure. In embodiments, the gas containment structure 102 can include a sapphire flange 502 and an additional flange 504. In this example, the gas containment structure 102 is configured as a closed volume having the additional flange 504 coupled to the second end of the second portion 111 of the second grade sapphire. The second flange 504 can be formed from the first grade sapphire, the second grade sapphire, or another material (e.g., metal).

[0038] Figure 7A gas containment structure 102 including a terminating bulb 702 according to one or more embodiments of the disclosure is illustrated. In this embodiment, a first portion of a first grade of sapphire can include a cylindrically symmetric bulb 702 terminated at a first end of the first portion 108. Additionally, a second portion 111 of a second grade of sapphire can include a cylindrically symmetric tube coupled to the cylindrically symmetric bulb 702. In this example, the gas containment structure 102 can be configured as an open or closed lamp. With the open configuration, a backflow gas flow can be established. With the closed configuration, the gas containment structure can include an additional flange 504 coupled to a second end of the second portion 111 of the second grade of sapphire.

[0039] Figure 8 A simplified schematic of an optical characterization system 800 incorporating a compact LSP broadband light source according to one or more alternative and / or additional embodiments is illustrated. In embodiments, the system 800 includes an LSP light source 100, an illumination arm 803, a collection arm 805, a detector assembly 814, and a controller 818 including one or more processors 820 and memory 822.

[0040] It is noted herein that the system 800 can comprise any imaging, inspection, metrology, lithography, or other characterization system known in the art. In this regard, the system 800 can be configured to perform inspection, optical metrology, lithography, and / or any form of imaging on a sample 807. The sample 807 can include any sample known in the art, including but not limited to wafers, reticles, photomasks, flat panel displays, and the like. It is noted that the system 800 can incorporate one or more of the various embodiments of the LSP light source 100 described throughout the disclosure.

[0041] In embodiments, the sample 807 is disposed on a stage assembly 812 to facilitate movement of the sample 807. The stage assembly 812 can include any stage assembly 812 known in the art, including but not limited to an X-Y stage, an R-0 stage, and the like. In embodiments, the stage assembly 812 adjusts the height of the sample 807 during inspection or imaging to maintain focus on the sample 807.

[0042] In an embodiment, the illumination arm 803 is configured to direct the broadband light 112 from the broadband LSP light source 100 to the sample 807. The illumination arm 803 can include any number and type of optical components known in the art. In an embodiment, the illumination arm 803 includes one or more optical elements 802, a beamsplitter 804, and an objective lens 806. In this regard, the illumination arm 803 can be configured to focus the broadband light 112 from the broadband LSP light source 100 onto a surface of the sample 807. The one or more optical elements 802 can 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 beamsplitters, and the like. It is noted herein that the collection location can include, but is not limited to, one or more of the optical elements 802, the beamsplitter 804, or the objective lens 806.

[0043] In an embodiment, the system 800 includes a collection arm 805 configured to collect light reflected, scattered, diffracted, and / or emitted from the sample 807. In another embodiment, the collection arm 805 can direct and / or focus the light from the sample 807 to a sensor 816 of a detector assembly 814. It is noted that the sensor 816 and the detector assembly 814 can include any sensor and detector assembly known in the art. The sensor 816 can include, but is not limited to, a CCD sensor or a CCD-TDI sensor. Further, the sensor 816 can include, but is not limited to, a line sensor or an electron bombarded line sensor.

[0044] In an embodiment, the detector assembly 814 is communicatively coupled to a controller 818 including one or more processors 820 and a memory 822. For example, the one or more processors 820 can be communicatively coupled to the memory 822, where the one or more processors 820 are configured to execute a set of program instructions stored on the memory 822. In one embodiment, the one or more processors 820 are configured to analyze the output of the detector assembly 814. In one embodiment, the set of program instructions are configured to cause the one or more processors 820 to analyze one or more properties of the sample 807. In another embodiment, the set of program instructions are configured to cause the one or more processors 820 to modify one or more properties of the system 800 in order to maintain focus on the sample 807 and / or the sensor 818. For example, the one or more processors 820 can be configured to adjust the objective lens 808 or the one or more optical elements 802 in order to focus the broadband light 117 from the broadband LSP light source 100 onto a surface of the sample 807. By way of another example, the one or more processors 820 can be configured to adjust the objective lens 806 and / or the one or more optical elements 810 in order to collect illumination from the surface of the sample 807 and focus the collected illumination on the sensor 816.

[0045] It should be noted that the system 800 can be configured in any optical configuration known in the art, including but not limited to a dark-field configuration, a bright-field configuration, and the like. The system 800 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 rotating 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 spectroscopic imaging system, or a scatterometer.

[0046] Additional details of various embodiments of the optical characterization system 800 are described in U.S. Pub. Pat. 7,957,066 B2, issued June 7, 2011, entitled "Split Field Inspection System Using Small Catadioptric Objectives"; U.S. Pub. Pat. App. 2007 / 0002465, published January 4, 2007, entitled "Beam Delivery System for Laser Dark-Field Illumination in a Catadioptric Optical System"; U.S. Pat. 5,999,310, issued December 7, 1999, entitled "Ultra-broadband UV Microscope Imaging System with Wide Range Zoom Capability"; U.S. Pat. 7,525,649, issued April 28, 2009, entitled "Surface Inspection System Using Laser Line Illumination with Two Dimensional Imaging"; U.S. Pub. Pat. App. 2013 / 0114085 to Wang et al., published May 9, 2013, entitled "Dynamically Adjustable Semiconductor Metrology System"; U.S. Pat. 5,608,526 to Piwonka-Corle et al., issued March 4, 1997, entitled "Focused Beam Spectroscopic Ellipsometry Method and System"; and U.S. Pat. 6,297,880 to Rosencwaig et al., issued October 2, 2001, entitled "Apparatus for Analyzing Multi-Layer Thin Film Stacks on Semiconductors", the entirety of each of which is incorporated herein by reference.

[0047] The one or more processors 820 of the present disclosure can include any one or more processing elements known in the art. In this sense, the one or more processors 820 can include any microprocessor type device configured to execute software algorithms and / or instructions. In one embodiment, the one or more processors 820 can be comprised of a desktop computer, mainframe computer system, workstation, image computer, parallel processor, or other computer system (e.g., networked computer) configured to execute a program configured to operate the system 800 and / or the broadband LSP light source 100, as described throughout the present disclosure. It should be recognized that the steps described throughout the present disclosure can be carried out by a single computer system or, alternatively, multiple computer systems. In general, the term "processor" can be broadly defined to encompass any device having one or more processing elements that execute program instructions from a non-transitory memory medium 822. Moreover, different subsystems of the various systems disclosed can include processors or logic elements suitable for carrying out at least a portion of the steps described throughout the present disclosure. Accordingly, the above description should not be interpreted as a limitation on the present disclosure and is for illustration only.

[0048] The memory medium 822 can include any storage medium known in the art suitable for storing program instructions executable by the associated one or more processors 820. For example, the memory medium 822 can include a non-transitory memory medium. For example, the memory medium 822 can include, but is not limited to, read-only memory, random access memory, magnetic or optical memory devices (e.g., magnetic disk), magnetic tape, solid state drives, and the like. In another embodiment, the memory 822 is configured to store one or more results and / or outputs of the various steps described herein. It should be further noted that the memory 822 can be housed in a common controller housing with the one or more processors 820. In alternative embodiments, the memory 822 can be remotely located with respect to the physical location of the processors 820. For example, the one or more processors 820 can access a remote memory (e.g., a server) that is accessible over a network (e.g., the Internet, an intranet, and the like). In another embodiment, the memory medium 822 maintains program instructions for causing the one or more processors 820 to carry out the various steps described throughout the present disclosure.

[0049] Those skilled in the art recognize that, for clarity of concept, the components, operations, devices, objects, and discussion attendant thereto described herein are used as examples and consider various configuration modifications. Thus, 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 inclusion of a particular component, e.g., operation, device, and object, should not be seen as limiting.

[0050] With respect to the use of substantially any plural and / or singular term herein, those having skill in the art can translate the contexts and / or applications from the plural to the singular and / or from the singular to the plural as is appropriate to the contexts and / or the application. For the sake of clarity, various singular / plural permutations are not explicitly set forth herein.

[0051] The herein described subject matter sometimes illustrates different components contained within, or connected with, other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as "associated with" each other such that the desired functionality is achieved, irrespective of architectures or intermediate components. Likewise, any two components so associated can also be viewed as being "connected" or "coupled" to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being "couplable" to each other to achieve the desired functionality. Specific examples of couplable include but are not limited to physically mateable and / or physically interacting components and / or wirelessly interactable and / or wirelessly interacting components and / or logically interacting and / or logically interactable components.

[0052] Moreover, it is to be understood that the invention is defined by the appended claims. Those skilled in the art will appreciate that, in general, terms used herein and especially in the appended claims (such as "including," "containing," "having," and the like) are open-ended terms (for example, the terms "including" and "having" should be interpreted as "including but not limited to"). It will be further understood that, unless otherwise specified, a specified number of an introduced claim recitation (such as "a ten recitation" or "at least one recitation") means that any combination of the specified number and the recitations can be used in the claim, i.e., one or more recitations can be used. It will be further understood that, unless otherwise specified, a specified number of an introduced claim recitation (such as "a ten recitation" or "at least one recitation") means that any combination of the specified number and the recitations can be used in the claim, i.e., one or more recitations can be used. It will be further understood that, unless otherwise specified, the use of the conjunctive "and" in the claims is not intended to mean that the claimed subject matter is limited to only the conjunctive "and" in the claims. It will be further understood that, unless otherwise specified, the use of the conjunctive "or" in the claims is not intended to mean that the claimed subject matter is limited to only the conjunctive "or" in the claims. It will be further understood that, unless otherwise specified, the use of the conjunctive "and" in the claims is not intended to mean that the claimed subject matter is limited to only the conjunctive "and" in the claims. It will be further understood that, unless otherwise specified, the use of the conjunctive "or" in the claims is not intended to mean that the claimed subject matter is limited to only the conjunctive "or" in the claims. It will be further understood that, unless otherwise specified, the use of the conjunctive "and" in the claims is not intended to mean that the claimed subject matter is limited to only the conjunctive "and" in the claims. It will be further understood that, unless otherwise specified, the use of the conjunctive "or" in the claims is not intended to mean that the claimed subject matter is limited to only the conjunctive "or" in the claims. It will be further understood that, unless otherwise specified, the use of the conjunctive "and" in the claims is not intended to mean that the claimed subject matter is limited to only the conjunctive "and" in the claims. It will be further understood that, unless otherwise specified, the use of the conjunctive "or" in the claims is not intended to mean that the claimed subject matter is limited to only the conjunctive "or" in the claims. It will be further understood that, unless otherwise specified, the use of the conjunctive "and" in the claims is not intended to mean that the claimed subject matter is limited to only the conjunctive "and" in the claims. It will be further understood that, unless otherwise specified, the use of the conjunctive "or" in the claims is not intended to mean that the claimed subject matter is limited to only the conjunctive "or" in the claims. It will be further understood that, unless otherwise specified, the use of the conjunctive "and" in the claims is not intended to mean that the claimed subject matter is limited to only the conjunctive "and" in the claims. It will be further understood that, unless otherwise specified, the use of the conjunctive "or" in the claims is not intended to mean that the claimed subject matter is limited to only the conjunctive "or" in the claims. It will be further understood that, unless otherwise specified, the use of the conjunctive "and" in the claims is not intended to mean that the claimed subject matter is limited to only the conjunctive "and" in the claims. It will be further understood that, unless otherwise specified, the use of the conjunctive "or" in the claims is not intended to mean that the claimed subject matter is limited to only the conjunctive "or" in the claims.For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

[0053] It is believed that the present disclosure and many of its attendant advantages will be understood by the foregoing description, and it will be apparent that various changes can be made in the form, construction and arrangement of the components without departing from the disclosed subject matter or without sacrificing all of its material advantages. The form described is merely exemplary and is intended to be within the scope of the appended claims as to be encompassed and covered thereby. Additionally, it is understood that the application is defined by the claims appended hereto.

Claims

1. A laser sustained broadband optical source comprising: a gas containment structure configured to house a gas, wherein the gas containment structure comprises: a first portion formed of a first grade of sapphire; a second portion formed of a second grade of sapphire different from the first grade of sapphire, wherein the first portion is coupled to one or more segments of the second portion of second grade sapphire; a primary laser pump source, wherein the primary laser pump source is configured to direct a primary pump beam into the gas containment structure to sustain a plasma; and a collector element configured to collect at least a portion of broadband light emitted from the plasma.

2. The broadband optical source of claim 1, wherein the first portion of the first grade of sapphire is brazed to one or more segments of the second portion of second grade sapphire.

3. The broadband optical source of claim 2, wherein the first portion of the first grade of sapphire is brazed to a first segment of the second portion of second grade sapphire and a second segment of the second portion of second grade sapphire.

4. The broadband optical source of claim 1, wherein the first portion of the first grade of sapphire comprises a first side and a second side, wherein the first side is cemented to the second side.

5. The broadband optical source of claim 1, wherein one or more surfaces of the first portion of the first grade of sapphire are coated with one or more selected materials.

6. The broadband optical source of claim 5, wherein the first portion of the first grade of sapphire is coated with one or more anti-reflection materials.

7. The broadband optical source of claim 1, further comprising one or more metal tubes coupled to one or more segments of the second portion of the second grade of sapphire.

8. The broadband optical source of claim 1, wherein the first portion of the first grade of sapphire comprises a cylindrical symmetric cross-section.

9. The broadband optical source of claim 8, wherein the first portion of the first grade of sapphire comprises a cylindrical symmetric tube.

10. The broadband optical source of claim 9, wherein the second portion of the second grade of sapphire comprises one or more cylindrical symmetric tubes.

11. The broadband optical source of claim 10, wherein the second portion of the second grade of sapphire comprises a first cylindrical symmetric tube coupled to the cylindrical symmetric tube of the first grade of sapphire on a first end and a second cylindrical symmetric tube coupled to the cylindrical symmetric tube of the first grade of sapphire on a second end.

12. The broadband optical source of claim 10, wherein the second portion of the second grade of sapphire comprises a first cylindrical symmetric tube coupled to the cylindrical symmetric tube of the first grade of sapphire on a first end and a sapphire flange coupled to the first portion of the first grade of sapphire on a second end of the first portion.

13. The broadband optical source of claim 12, further comprising an additional flange coupled to an end of the second portion of the second grade of sapphire to form a closed volume.

14. The broadband optical source of claim 10, wherein a first end of the cylindrical symmetric tube of the first grade of sapphire includes a sapphire gas nozzle.

15. The broadband optical source of claim 10, wherein the cylindrical symmetric tube of the first grade of sapphire comprises a cylinder.

16. The broadband optical source of claim 10, wherein the cylindrical symmetric tube of the first grade of sapphire comprises a cylinder having a spherical cross-section.

17. The broadband optical source of claim 10, wherein the cylindrical symmetric tube of the first grade of sapphire comprises a cylinder having an ellipsoidal cross-section.

18. The broadband optical source of claim 8, wherein the first portion of the first grade of sapphire comprises a cylindrical symmetric bulb terminated at a first end.

19. The broadband optical source of claim 18, wherein the second portion of the second grade of sapphire comprises a cylindrical symmetric tube coupled to the cylindrical symmetric bulb.

20. The broadband optical source of claim 19, further comprising an additional flange coupled to an end of the second portion of the second grade of sapphire to form a closed volume.

21. The broadband optical source of claim 1, wherein the gas containment structure is configured as a gas flow-through cell.

22. The broadband optical source of claim 1, wherein the gas containment structure is configured as a reverse vortex flow-through cell.

23. The broadband optical source of claim 1, wherein the gas containment structure is configured as a closed static cell.

24. The broadband optical source of claim 1, wherein the light collecting element comprises at least one of a mirror or a lens.

25. The broadband optical source of claim 24, wherein the light collector element comprises a reflector assembly.

26. The broadband optical source of claim 25, wherein the light collector element comprises at least one of an elliptical reflector assembly or a spherical reflector assembly.

27. The broadband optical source of claim 1, wherein the primary pump laser source comprises one or more continuous wave (CW) lasers.

28. The broadband optical source of claim 1, further comprising: pulsed excitation laser source, wherein the pulsed excitation laser source is configured to direct a pulsed laser beam into the gas to excite the plasma.

29. A plasma lamp comprising: a gas containment structure configured to house a gas, wherein the gas containment structure comprises: a first portion formed of a first grade of sapphire; a second portion formed of a second grade of sapphire different from the first grade of sapphire, wherein the first portion is coupled to one or more segments of the second portion of the second grade of sapphire, wherein at least the first portion is transparent to illumination from a pump laser and at least a portion of broadband light from a plasma generated within the gas containment structure.

30. A characterization system comprising: a laser sustained optical source comprising: A gas containment structure configured to house a gas, wherein the gas containment structure comprises: a first portion formed of a first grade of sapphire; a second portion formed of a second grade of sapphire different from the first grade of sapphire, wherein the first portion is coupled to one or more segments of the second portion of second grade sapphire; a primary laser pump source, wherein the primary laser pump source is configured to direct a primary pump beam into the gas containment structure to maintain a plasma; and a collector element configured to collect at least a portion of broadband light emitted from the plasma, wherein the characterization system further comprises: a set of illumination optics configured to direct broadband light from the laser- maintained light source to one or more samples; a set of collection optics configured to collect light emanating from the one or more samples; and a detector assembly.

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