Laser sustained plasma light source with conical window

Abstract

A LSP broadband light source is disclosed. The light source can include a gas containment structure for containing a gas. The light source can include a laser pump source configured to generate an optical pump to sustain a plasma within the gas containment structure to generate broadband light. The light source can include a tapered window configured to transmit broadband light through an aperture in a wall of the gas containment structure, the tapered window including a tapered section including a tapered surface, wherein the tapered surface is configured to deflect light impinging on a peripheral portion of the tapered window away from a portion of the gas containment structure to protect the portion of the gas containment structure.

Description

[0001] Cross-reference of related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 451,049, filed March 9, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to plasma-based radiation sources, and more specifically, to a high-power vacuum ultraviolet (VUV) laser-sustaining plasma (LSP) source having a conical window for deflecting broadband light away from a sealed region. Background Technology

[0004] Laser-sustaining plasma (LSP) sources are widely used in broadband inspection tools for semiconductor testing and imaging. Typically, a near-infrared (NIR) continuous-wave (CW) pumped laser is focused into a gas-containing container where plasma is ignited and sustained by absorbing the pumped laser radiation. This container can be a lamp (e.g., a glass bulb with or without electrodes for plasma ignition), 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 input and plasma light output), or a similar assembly. Various plasma containers have high internal pressures, reaching tens or even hundreds of 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 the 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 especially in the range of approximately 125 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 metallic chamber with multiple windows that couple laser light in and out of the chamber. While different materials can be used for the laser windows, few options exist for VUV generation. The most widely used are MgF2, which has a transmission cutoff wavelength of approximately 115 nm, or CaF2, which has a transmission cutoff wavelength of approximately 125 nm.

[0006] One of the most significant limitations to the operation of this VUV source is the trade-off between the actual window size and the amount of radiative heat load that the window and its sealing elements must withstand when constructing the high-pressure window used with the LSP source. Currently, the window can be sealed on three different surfaces, which determines how close the window sealing elements are positioned to the plasma. Figures 1A to 1CAs shown, the seals for the windows can be positioned on the front, side, or rear surface of the window, as shown in views 10, 20, and 30, respectively. In each case, broadband light 14 illuminates a given window assembly 10, 20, or 30. While a portion 18 of the broadband light 14 is transmitted through the central portion of the window 11, a portion 16 of the broadband light illuminates one or more portions of the window assembly, such as the seal 113. Due to the radiative heat load on the seal 113, the seal 113 degrades over time. Figure 2 Figure 40 shows a cross-section depicting a portion of the path of broadband light in more detail.

[0007] As shown, previous construction methods resulted in seals or structural elements placed very close to the window of a high-power plasma source being directly irradiated by the plasma light, leading to high thermal loads on the seals and / or sealing structural elements, whose cooling became a limiting factor for window performance. Therefore, it is desirable to provide a broadband LSP source that overcomes the limitations outlined above. Summary of the Invention

[0008] A laser-supplied plasma (LSP) broadband light source is disclosed. In some aspects, the LSP broadband light source includes: a gas containment structure for containing a gas; a laser pump source configured to generate an optical pump, wherein the laser pump source is configured to direct the optical pump into the gas containment structure to maintain a plasma within the gas containment structure, wherein the plasma generates broadband light; and a window configured to allow broadband light to transmit through an aperture within the wall of the gas containment structure, the window including a tapered section, the tapered section including a tapered surface, wherein the tapered surface is configured to deflect a portion of the light incident on a peripheral portion of the window away from the gas containment structure to protect one or more portions of the gas containment structure.

[0009] A semiconductor characterization system is disclosed. In some aspects, the characterization system includes a broadband light source. The broadband light source includes: a gas containment structure for containing a gas; a laser pump source configured to generate an optical pump, wherein the laser pump source is configured to direct the optical pump into the gas containment structure to maintain a plasma within the gas containment structure, wherein the plasma generates broadband light; and a window configured to allow broadband light to transmit through an aperture of the gas containment structure, the output optical window including a tapered segment, the tapered segment including a tapered surface, wherein the tapered surface is configured to deflect a portion of light incident on a peripheral portion of the window away from the aperture of the gas containment structure to protect one or more portions of the gas containment structure. In some aspects, the characterization system further includes: a set of illumination optics configured to direct broadband light from the broadband light source to one or more samples; a set of collection optics configured to collect light emitted from the one or more samples; and a detector assembly.

[0010] A method for generating VUV broadband light is disclosed. In some aspects, the method includes: containing a gas within a gas-containing structure; generating an optical pump and directing the optical pump into the gas-containing structure to maintain a plasma within the gas-containing structure to generate broadband light; deflecting a portion of the broadband light incident on a peripheral portion of a window away from pores within the wall of the gas-containing structure to protect one or more portions of the gas-containing structure; and transmitting the broadband light incident on a central portion of the window through pores within the wall of the gas-containing structure. In some aspects, a laser-sustaining broadband light source includes: a gas containment structure for containing a gas; a laser pump source configured to generate an optical pump, wherein the laser pump source is configured to direct the optical pump into the gas containment structure to maintain a plasma within the gas containment structure, wherein the plasma generates broadband light; and a window configured to allow broadband light to transmit through an aperture within the wall of the gas containment structure, the window including a tapered section, the tapered section including a tapered surface, wherein the tapered surface is configured to deflect a portion of light incident on a peripheral portion of the window away from the gas containment structure to protect one or more portions of the gas containment structure.

[0011] It should be understood that the foregoing general description and the following detailed description are merely illustrative and explanatory and are not intended to limit this disclosure. The accompanying drawings, which are incorporated in and form a part of this specification, illustrate the subject matter of this disclosure. The description and drawings together serve to explain the principles of this disclosure. Attached Figure Description

[0012] Those skilled in the art can better understand the advantages of this disclosure by referring to the accompanying drawings.

[0013] Figures 1A to 1CThis describes a method for sealing the window in a high-voltage LSP broadband light source.

[0014] Figure 2 A cross-sectional view illustrating the method of sealing the window in a high-voltage LSP broadband light source.

[0015] Figure 3 A simplified schematic diagram illustrating an LSP broadband light source with a tapered surface according to one or more embodiments of the present disclosure.

[0016] Figure 4A This illustration shows a cross-sectional view of a tapered window within a high-voltage LSP broadband light source according to one or more embodiments of the present disclosure.

[0017] Figure 4B A simplified schematic diagram illustrating a conical window within a high-voltage LSP broadband light source according to one or more embodiments of the present disclosure.

[0018] Figure 5A A cross-sectional view of a tapered surface having a convex surface for collimating and transmitting light through a tapered window, according to one or more embodiments of the present disclosure.

[0019] Figure 5B A cross-sectional view illustrating a conical surface having a concave surface for focusing and transmitting light through a conical window, according to one or more embodiments of the present disclosure.

[0020] Figure 6 A simplified schematic diagram illustrating a characterization system incorporating an LSP broadband light source according to one or more alternative and / or additional embodiments of the present disclosure.

[0021] Figure 7 This is a flowchart illustrating a method for generating VUV light using an LSP broadband light source according to one or more embodiments of the present disclosure, wherein the broadband light is deflected away from a portion of the window. Detailed Implementation

[0022] The disclosed subject matter will now be described in detail with reference to the accompanying drawings. This disclosure has been specifically shown and described with respect to particular embodiments and their specific features. The embodiments set forth herein are to be considered illustrative rather than restrictive. It will be readily apparent to those skilled in the art that various changes and modifications in form and detail may be made without departing from the spirit and scope of this disclosure.

[0023] General reference Figures 1A to 7 According to one or more embodiments of the present disclosure, a laser-suppressed plasma broadband light source having a conical window for deflecting light from a selected portion of a plasma chamber is described.

[0024] Embodiments of this disclosure relate to a broadband LSP source equipped with one or more tapered windows configured to deflect broadband light away from one or more portions of a chamber used to generate a plasma source. For example, embodiments of this disclosure may include tapered windows (e.g., polished conical surfaces) arranged to deflect broadband light emitted by the plasma away from one or more seals that form a seal between the window and the walls of the chamber.

[0025] Figure 3 This illustration shows a simplified schematic of an LSP broadband light source 100 having one or more conical windows according to one or more embodiments. In one embodiment, the light source 100 includes a gas containment structure 102 that contains one or more gases 103. For example, the gas containment structure 102 may contain one or more high-pressure gases (e.g., 50 to 300 atm). In one embodiment, the light source 100 includes a conical window 104 configured to allow broadband light to pass through an aperture 107 within the wall 105 of the gas containment structure 102. In one embodiment, the conical window 104 includes a conical segment that includes a conical surface 122. The conical surface 122 may be configured to deflect a portion 118 of light illuminating a peripheral portion of the conical window 104 away from the gas containment structure 102 to protect one or more portions 123 of the gas containment structure 102. For example, the conical window 104 may be configured to deflect illumination 118 away from one or more seals 123. In one embodiment, the tapered window 104 transmits some illumination 120 through its central surface 124 and through the aperture 107, while avoiding one or more seals 123. In another embodiment, the tapered surface 122 of the tapered window 104 internally reflects some illumination 121, such that the illumination 121 passes through the aperture 107 and avoids one or more seals 123. In yet another embodiment, the illumination 120, 121 passing through the aperture 107 is transmitted to one or more downstream optics 111.

[0026] The cone-shaped window can be used as an input or output window. Although window 104 has been depicted as an output window in this disclosure, this configuration should not be construed as limiting the scope of this disclosure, and in other embodiments, the window can be used as an input window. For example, window 110 can be replaced by window 104.

[0027] In one embodiment, the light source 100 includes a laser pump source 106 configured to generate an optical pump 108. The laser pump source 106 is configured to direct the optical pump 108 into a gas containment structure 102 to maintain a plasma 112 within the gas containment structure 102 to generate broadband light 116. For example, the laser pump source 106 and a focusing lens 109 can direct and focus the optical pump 108 into the gas containment structure 102 through a window 110 to maintain the plasma 112.

[0028] The laser pump source 106 may comprise any laser known in the art of plasma-based broadband light generation. In embodiments, the laser pump source 106 may comprise one or more continuous-wave (CW) pumped lasers and / or one or more pulsed lasers. The laser pump source 106 may be configured to emit infrared (IR) radiation, near-infrared (NIR) radiation, ultraviolet (UV) radiation, visible radiation, or other radiation suitable for forming plasma when incident on a suitable target material.

[0029] In an embodiment, the light source 100 includes one or more collecting optics 114. For example, the one or more collecting optics may include one or more mirrors and / or one or more lenses. For example, such as Figure 3 As shown, one or more collecting optics 114 may include a retroreflector configured to collect broadband light 116 from plasma 112 and redirect the illumination toward aperture 107 and through tapered window 104.

[0030] The gas contained within the gas containment structure 102 and used to generate plasma 112 may contain any gas or gas mixture suitable for broadband generation via a laser-supplied plasma source. For example, one or more gases may contain, but are not limited to, Ar, Xe, Kr, Ne, or He, or a mixture of two or more of Ar, Xe, Kr, Ne, or He.

[0031] The broadband light source 100 can be configured to emit broadband light in one or more spectral ranges, including UV light, VUV light and / or DUV light.

[0032] Figure 4A A cross-sectional view of a conical window 104 according to one or more embodiments of the present disclosure is shown. Broadband light 116 illuminates the conical window 104. The central portion 120 of the illumination 116 passes through the front surface 124 of the conical window 104 and through the aperture 107 of the wall 105, without illuminating one or more seals 123. The peripheral portion of the illumination 116 illuminates the conical surface 122 of the conical window 104. A first portion 118 of the light illuminating the conical surface 122 is deflected away from the conical window 104 and away from one or more seals 123. A second portion 121 of the light illuminating the conical surface 121 is internally reflected through the block of the conical window 104 and the aperture 107 of the wall 105, while avoiding one or more seals 123.

[0033] In one embodiment, the tapered surface 122 of the tapered window 104 may be polished to reflect a portion 119 of broadband light incident on the peripheral portion of the window 104 away from the apertures 107 in the wall 105 of the gas containment structure 102, thereby protecting one or more portions of the gas containment structure 102. In another embodiment, the tapered surface 122 comprises a polished tapered surface configured to scatter a portion 119 of light incident on the peripheral portion of the window 124 away from the apertures 107 in the wall 105 of the gas containment structure 102, thereby protecting one or more portions of the gas containment structure 102.

[0034] The conical window 104 can be formed from any optical material known in the art suitable for operation in high-pressure VUV light sources. For example, the conical window 104 can be formed from, but is not limited to, MgF2, CaF2, LiF, sapphire, quartz and the like.

[0035] Figure 4B A simplified cross-sectional view of a conical window 104 according to one or more embodiments of the present disclosure is shown. The conical window 104 may be formed as a monolithic structure having a conical cylindrical shape. For example, the conical window 104 may include a cylindrical body 126, a conical surface 122, and a face 124. In an embodiment, the conical surface 122 includes a conical surface. The conical surface may include one or more conical segments. Note that the scope of the present disclosure is not limited to this. Figure 4B The conical structure depicted is for illustrative purposes only.

[0036] Figures 5A to 5B A simplified cross-sectional view is shown for a conical window 104 having a convex lens surface according to one or more embodiments of the present disclosure. In an embodiment, the convex lens surface 130 may be formed at the central portion of the conical window 104. For example, as... Figure 5A As shown, the convex lens surface 130 can be configured to collimate light incident on the convex lens surface 130 of the conical window 104. As another example, such as... Figure 5B As shown, the convex lens surface 130 can be configured to focus light incident on the convex lens surface 130 of the conical window 104. The convex lens surface 130 may include, but is not limited to, a spherical lens surface. The surface of the conical window 104 can be modified to modulate broadband light in a desired manner. For example, the conical window 104 may include a lens surface or a filter surface.

[0037] Figure 6 This diagram illustrates a simplified schematic of an optical characterization system 600 incorporating a compact LSP broadband light source, according to one or more alternative and / or additional embodiments. In an embodiment, system 600 includes an LSP light source 100, an illumination arm 603, a collection arm 605, a detector assembly 614, and a controller 618 including one or more processors 620 and a memory 622.

[0038] It should be noted herein that system 600 may include any imaging, inspection, metrology, lithography, or other characterization system known in the art. In this regard, system 600 may be configured to perform inspection, optical metrology, lithography, and / or any form of imaging on sample 607. Sample 607 may comprise any sample known in the art, including, but not limited to, wafers, photomasks, photomasks, and the like. It should be noted that system 600 may be incorporated into one or more of the various embodiments of the LSP light source 100 described throughout this disclosure.

[0039] In one embodiment, sample 607 is positioned on stage assembly 612 to facilitate movement of sample 607. Stage assembly 612 may comprise any stage assembly 612 known in the art, including, but not limited to, XY stages, R-θ stages, and the like. In another embodiment, stage assembly 612 is capable of adjusting the height of sample 607 during inspection or imaging to maintain focus on sample 607.

[0040] In one embodiment, illumination arm 603 is configured to direct broadband light 117 from broadband LSP source 100 to sample 607. Illumination arm 603 may include any number and type of optical components known in the art. In one embodiment, illumination arm 603 includes one or more optical elements 602, beam splitter 604, and objective lens 606. In this regard, illumination arm 603 may be configured to focus broadband light 117 from broadband LSP source 100 onto the surface of sample 607. The one or more optical elements 602 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. Note that the collection location may include, but is not limited to, one or more of optical elements 602, beam splitter 604, or objective lens 606.

[0041] In one embodiment, system 600 includes a collection arm 605 configured to collect light reflected, scattered, diffracted, and / or emitted from sample 607. In another embodiment, collection arm 605 may guide and / or focus light from sample 607 onto sensor 616 of detector assembly 614. It should be noted that sensor 616 and detector assembly 614 may include any sensor and detector assembly known in the art. Sensor 616 may include, but is not limited to, a CCD sensor or a CCD-TDI sensor. Furthermore, sensor 616 may include, but is not limited to, a line sensor or an electron-bombarded line sensor.

[0042] In one embodiment, the detector assembly 614 is communicatively coupled to a controller 618 including one or more processors 620 and a memory 622. For example, one or more processors 620 may be communicatively coupled to the memory 622, wherein the one or more processors 620 are configured to execute a set of program instructions stored in the memory 622. In one embodiment, the one or more processors 620 are configured to analyze the output of the detector assembly 614. In one embodiment, the set of program instructions is configured to cause one or more processors 620 to analyze one or more characteristics of the sample 607. In another embodiment, the set of program instructions is configured to cause one or more processors 620 to modify one or more characteristics of the system 600 to maintain focus on the sample 607 and / or the sensor 616. For example, one or more processors 620 may be configured to adjust the objective lens 606 or one or more optical elements 602 to focus broadband light 117 from the broadband LSP light source 100 onto the surface of the sample 607. In another example, one or more processors 620 may be configured to adjust the objective lens 606 and / or one or more optical elements 610 to collect illumination from the surface of the sample 607 and focus the collected illumination onto the sensor 616.

[0043] It should be noted that system 600 can be configured as any optical configuration known in the art, including but not limited to dark field configurations, light field configurations, and the like. System 600 can be configured as any type of metrological instrument known in the art, such as but not limited to a spectral elliptometer with one or more illumination angles, a spectral elliptometer for measuring Mueller matrix elements (e.g., using a rotation compensator), a single-wavelength elliptometer, an angle-resolved elliptometer (e.g., a beam profile elliptometer), a spectral reflectometer, a single-wavelength reflectometer, an angle-resolved reflectometer (e.g., a beam profile reflectometer), an imaging system, a pupil imaging system, a spectral imaging system, or a scattering instrument.

[0044] Additional details of various embodiments of the optical characterization system 600 can be found in U.S. Patent Publication No. 7,957,066B2, entitled "Split Field Inspection System Using Small Catadioptric Objectives," published June 7, 2011; U.S. Patent Publication No. 2007 / 0002465, entitled "Beam Delivery System for Laser Dark-Field Illumination in a Catadioptric Optical System," published January 4, 2007; U.S. Patent Publication No. 5,999,310, entitled "Ultra-broadband UV Microscope Imaging System with Wide Range Zoom Capability," published December 7, 1999; and U.S. Patent Publication No. 28, 2009, entitled "Surface Inspection System Using Laser Line Illumination with Two Dimensional Imaging." U.S. Patent 7,525,649 entitled “Dynamically Adjustable Semiconductor Metrology System”, published May 9, 2013 by Wang et al.; U.S. Patent Publication 2013 / 0114085 entitled “Dynamically Adjustable Semiconductor Metrology System”, published May 9, 2013 by Piwonka-Corle et al.; U.S. Patent 5,608,526 entitled “Focused Beam Spectroscopic Ellipsometry Method and System”, published March 4, 1997 by Piwonka-Corle et al.; and U.S. Patent 6,297,880 entitled “Apparatus for Analyzing Multi-Layer Thin Film Stacks on Semiconductors”, published October 2, 2001 by Rosencwaig et al., the entire contents of which are each incorporated herein by reference.

[0045] One or more processors 620 of this disclosure may comprise any one or more processing elements known in the art. In this sense, one or more processors 620 may comprise any microprocessor-type device configured to execute software algorithms and / or instructions. In one embodiment, one or more processors 620 may comprise a desktop computer, host computer system, workstation, graphics computer, parallel processor, or other computer system (e.g., a network computer) configured to execute programs configured to operate system 600 and broadband LSP light source 100, as described throughout this disclosure. It should be appreciated that the steps described throughout this disclosure may be performed by a single computer system or (alternatively) multiple computer systems. Generally, the term “processor” may be broadly defined to encompass any device having one or more processing elements that execute program instructions from non-transitory memory media 622. Furthermore, different subsystems of the various systems disclosed may include processor or logic elements suitable for carrying out at least a portion of the steps described throughout this disclosure. Therefore, the foregoing description should not be construed as a limitation of this disclosure but is merely illustrative.

[0046] Memory medium 622 may comprise any storage medium known in the art suitable for storing program instructions executable by one or more associated processors 620. For example, memory medium 622 may comprise a non-transitory memory medium. For example, memory medium 622 may comprise, but is not limited to, read-only memory, random access memory, magnetic or optical memory devices (e.g., optical discs), magnetic tape, solid-state drives, and the like. In another embodiment, memory 622 is configured to store one or more results and / or outputs of the various steps described herein. It should be further noted that memory 622 may be housed in a common controller housing with one or more processors 620. In an alternative embodiment, memory 622 may be remotely located relative to the physical location of processor 620. For example, one or more processors 620 may access remote memory (e.g., a server) accessible via a network (e.g., the Internet, an intranet, and the like). In another embodiment, memory medium 622 holds program instructions for causing one or more processors 620 to perform the various steps described herein.

[0047] Figure 7 This document describes a process flow diagram of a method 700 for generating VUV light using a broadband LSP light source with a tapered window, according to one or more alternative and / or additional embodiments. It should be noted herein that the steps of method 700 may be fully or partially implemented by the broadband LSP light source 100. However, it is further appreciated that method 700 is not limited to the broadband LSP light source 100, and that additional or alternative system-level embodiments may perform all or part of the steps of method 700.

[0048] In step 702, method 700 includes containing a gas within a gas-containing structure. In step 704, method 700 includes generating an optical pump and directing the optical pump into the gas-containing structure to maintain plasma within the gas-containing structure to generate broadband light. In step 706, method 700 includes deflecting a portion of the broadband light incident on the peripheral portion of the window away from an aperture within the wall of the gas-containing structure to protect one or more portions of the gas-containing structure. In step 708, the method includes transmitting the broadband light incident on the central portion of the window through an aperture within the wall of the gas-containing structure.

[0049] Those skilled in the art will recognize that the components, operations, devices, objects, and accompanying discussions described herein are used as examples for conceptual clarity, and various configuration modifications are anticipated. Therefore, as used herein, the specific paradigms illustrated and the accompanying discussions are intended to represent their more general categories. In general, the use of any particular paradigm is intended to indicate its category, and the non-exclusivity of a particular component (e.g., operation), device, and object should not be considered limiting.

[0050] Regarding the use of any plural and / or singular terms in this document, those skilled in the art can convert them from plural to singular and / or from singular to plural as appropriate for the context and / or application. For clarity, various singular / plural substitutions are not explicitly described herein.

[0051] The objects described herein sometimes refer to different components contained within or connected to other components. It should be understood that such depicted architectures are merely exemplary, and many other architectures can in fact be implemented to achieve the same functionality. Conceptually, any arrangement of components achieving the same functionality is effectively “associated” to achieve the desired functionality. Therefore, without regard to architecture or intermediate components, any two components in this document combined to achieve a particular functionality can be considered “associated” with each other to achieve the desired functionality. Similarly, any two such associated components can also be considered “connected” or “coupled” to each other to achieve the desired functionality, and any two components that can be suchly associated can also be considered “coupleable” to each other to achieve the desired functionality. Specific examples of coupleability include, but are not limited to, physically interactive and / or wirelessly interactive and / or logically interactive components.

[0052] Furthermore, it should be understood that the invention is defined by the appended claims. Those skilled in the art will appreciate that, generally, the terms used herein and particularly in the appended claims (e.g., the body of the appended claims) are generally intended to be “open-ended” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “at least having,” the term “includes” should be interpreted as “including but not limited to,” etc.). Those skilled in the art will further appreciate that if a particular number of claims is intended to be introduced, this intention will be explicitly stated in the claims, and this intention will not exist where such a statement is absent. For example, to aid understanding, the appended claims may contain the introductory phrases “at least one” and “one or more” to introduce the claims. However, the use of such phrases should not be considered to imply that introducing a claim statement with the indefinite article "a" or "an" limits any particular claim containing such an introductory claim statement to an invention containing only one such statement, even when the same claim contains the introductory phrase "a or more" or "at least one" and an indefinite article such as "a" or "an" (e.g., "a" or "an" should generally be interpreted as meaning "at least one" or "a or more"); the same applies to the use of definite articles used to introduce a claim statement. Furthermore, even if a specific number of introductory claim statements is explicitly stated, those skilled in the art will recognize that such a statement should generally be interpreted as meaning at least the number stated (e.g., the bare statement "two statements" without other modifiers generally means at least two statements or two or more statements). Furthermore, in examples where a convention similar to "at least one of A, B, and C" is used, generally, a person skilled in the art will understand the meaning of the convention and anticipate this construction (e.g., "a system having at least one of A, B, and C" will 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.). In examples where a convention similar to "at least one of A, B, or C" is used, generally, a person skilled in the art will understand the meaning of the convention and anticipate this construction (e.g., "a system having at least one of A, B, or C" will 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 understand that transitional words and / or phrases (whether in the description, claims or figures) that present two or more alternative terms should be understood as potentially including one, any, or both of the terms.For example, the phrase “A or B” will be understood as containing the possibility of “A” or “B” or “A and B”.

[0053] It is believed that this disclosure and its many accompanying advantages will be understood from the foregoing description, and it will be appreciated that various changes can be made to the form, construction, and arrangement of the components without departing from the subject matter of the disclosure or sacrificing all its material advantages. The forms described are illustrative only, and the appended claims are intended to cover and encompass such changes. Furthermore, it should be understood that the invention is defined by the appended claims.

Claims

1. A laser-suppressed plasma broadband light source, comprising: A gas containment structure used to contain gas; A laser pumping source configured to generate an optical pump, wherein the laser pumping source is configured to direct the optical pump into the gas containment structure to maintain a plasma within the gas containment structure, wherein the plasma generates broadband light; and A window, configured to allow a portion of the broadband light to be transmitted through pores within the wall of the gas-containing structure, the window comprising a tapered section having a tapered surface, wherein: The conical surface is configured to deflect a portion of the broadband light illuminating the peripheral portion of the window away from one or more seals of the gas containment structure, thereby protecting one or more portions of the gas containment structure; and The conical surface is configured to reflect another portion of the broadband light within the conical section, allowing the other portion of the broadband light to pass through the aperture and bypass one or more portions of the gas-containing structure.

2. The broadband light source according to claim 1, wherein the window comprises a cylindrical window having the conical section.

3. The broadband light source according to claim 1, wherein the conical section includes a circular conical section.

4. The broadband light source of claim 1, wherein the tapered surface is configured to transmit a portion of the broadband light illuminating the peripheral portion of the window through the pores of the gas-containing structure.

5. The broadband light source of claim 1, wherein the central portion of the window is configured to transmit broadband light illuminating the central portion of the window through the aperture.

6. The broadband light source of claim 1, wherein the conical surface comprises a polished conical surface configured to reflect a portion of the broadband light illuminating the peripheral portion of the window away from the pores in the wall of the gas containment structure to protect one or more portions of the gas containment structure.

7. The broadband light source of claim 1, wherein the conical surface comprises a polished conical surface configured to scatter a portion of the broadband light illuminating the peripheral portion of the window away from the pores in the wall of the gas containment structure, thereby protecting one or more portions of the gas containment structure.

8. The broadband light source of claim 1, wherein the window includes a convex lens surface located at the center portion of the window, wherein the convex lens surface is configured to collimate or focus broadband light onto the center portion of the window.

9. The broadband light source according to claim 8, wherein the convex lens surface includes a spherical lens surface.

10. The broadband light source according to claim 1, wherein the window is formed of at least one of MgF2, CaF2 or LiF.

11. The broadband light source according to claim 1, wherein the window includes at least one of an output window or an input window.

12. The broadband light source according to claim 1, wherein the pressure of the gas within the gas containment structure is between 50 atm and 300 atm.

13. The broadband light source according to claim 1, wherein the broadband light transmitted through the window comprises at least vacuum ultraviolet light.

14. A characterization system, comprising: Broadband light sources, including: A gas containment structure used to contain gas; A laser pumping source configured to generate an optical pump, wherein the laser pumping source is configured to direct the optical pump into the gas containment structure to maintain a plasma within the gas containment structure, wherein the plasma generates broadband light; and A window, configured to allow a portion of the broadband light to be transmitted through the pores of the gas-containing structure, the window comprising a tapered segment, the tapered segment comprising a tapered surface, wherein: The conical surface is configured to deflect a portion of the light incident on the outer portion of the window away from one or more seals of the gas containment structure, thereby protecting one or more portions of the gas containment structure; and The conical surface is configured to reflect another portion of the broadband light within the conical section, allowing the other portion of the broadband light to pass through the aperture and bypass one or more portions of the gas-containing structure; A set of illumination optics configured to direct the broadband light from the broadband light source to one or more samples; A set of collecting optics configured to collect light emitted from the one or more samples; and Detector assembly.

15. The characterization system of claim 14, wherein the window comprises a cylindrical window having the tapered section.

16. The characterization system of claim 14, wherein the tapered section comprises a conical section.

17. The characterization system of claim 14, wherein the tapered surface is configured to transmit a portion of broadband light illuminating the peripheral portion of the window through the pores of the gas containment structure.

18. The characterization system of claim 14, wherein the central portion of the window is configured to transmit broadband light illuminating the central portion of the window through the aperture.

19. The characterization system of claim 14, wherein the tapered surface comprises a polished tapered surface configured to reflect a portion of broadband light illuminating the peripheral portion of the window away from the pores in the wall of the gas containment structure to protect one or more portions of the gas containment structure.

20. The characterization system of claim 14, wherein the tapered surface comprises a polished tapered surface configured to scatter a portion of broadband light illuminating the peripheral portion of the window away from the pores in the wall of the gas containment structure, thereby protecting one or more portions of the gas containment structure.

21. The characterization system of claim 14, wherein the optical window includes a convex lens surface located at the central portion of the optical window, wherein the convex lens surface is configured to collimate or focus broadband light onto the central portion of the optical window.

22. The characterization system of claim 21, wherein the convex lens surface includes a spherical lens surface.

23. The characterization system of claim 14, wherein the window is formed of at least one of MgF2, CaF2 or LiF.

24. The characterization system of claim 14, wherein the window includes at least one of an output window or an input window.

25. The characterization system of claim 14, wherein the pressure of the gas within the gas containment structure is between 50 atm and 300 atm.

26. The characterization system of claim 14, wherein the broadband light transmitted through the window comprises at least vacuum ultraviolet light.

27. A method for generating VUV broadband light, comprising: The gas is contained within the gas-containing structure; An optical pump is generated and directed into the gas containment structure to maintain the plasma within the gas containment structure to generate broadband light; A portion of the broadband light illuminating the outer portion of the window is deflected away from one or more seals of the gas containment structure, and another portion of the broadband light illuminating the outer portion of the window is reflected through pores in the wall of the gas containment structure to protect one or more portions of the gas containment structure. and Broadband light illuminating the central portion of the window is transmitted through the pores within the wall of the gas-containing structure.

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