Analysis of low energy x-ray fluorescence emitted from sample in atmospheric environment

Abstract

The invention relates to analysis of low energy X-ray fluorescence emitted from a sample in an atmospheric environment. A system for X-ray analysis, the system comprising: (a) an X-ray analysis assembly: (i) disposed in an X-ray housing, the X-ray housing configured to maintain a controlled first pressure, and (ii) configured to direct a first X-ray beam toward a sample positioned outside the X-ray housing at a second pressure different from the first pressure, and generate a signal indicative of a second X-ray beam emitted from the sample in response to the first X-ray beam impacting the sample; and (b) a window assembly disposed between the X-ray analysis assembly and the sample, and configured to (i) seal the X-ray housing to maintain a pressure difference between the first pressure and the second pressure, and (ii) pass the first X-ray beam and the second X-ray beam, and the window assembly includes a window layer made of a material transparent to the first X-ray beam and the second X-ray beam.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application 63 / 649,378, filed May 19, 2024, the disclosure of which is incorporated herein by reference. Invention Field

[0003] This invention relates generally to X-ray analysis, and more particularly to methods and systems for analyzing low-energy X-ray fluorescence emitted from samples located in an atmospheric environment. Background of the Invention

[0004] Several techniques have been developed for measuring X-ray fluorescence emitted from samples located in the atmospheric environment.

[0005] For example, Japanese patent application JP 2001-105636 A describes an X-ray fluorescence analyzer that includes a measuring unit and a movable unit. The measuring unit includes a first opening, a measuring chamber, an X-ray source for irradiating a first X-ray into the first opening, an X-ray detector for detecting a second X-ray, an intake / exhaust device for intake / exhaust of the measuring chamber, and a gas introduction device for introducing gas into the measuring chamber. Invention Overview

[0006] The embodiments of the present invention described herein provide a system for X-ray analysis, the system comprising: (a) an X-ray analysis assembly (i) disposed within an X-ray housing configured to maintain a controlled first pressure, and (ii) configured to direct a first X-ray beam toward a sample positioned outside the X-ray housing at a second pressure different from the first pressure, and to generate a signal indicating a second X-ray beam emitted from the sample in response to the first X-ray beam striking the sample; and (b) a window assembly disposed between the X-ray analysis assembly and the sample, and configured to (i) seal the X-ray housing to maintain a pressure difference between the first and second pressures, and (ii) allow the first and second X-ray beams to pass through, and said window assembly comprising a window layer made of a material transparent to the first and second X-ray beams.

[0007] In some embodiments, the window layer comprises a silicon-nitrogen compound. In other embodiments, the window layer comprises a film of graphene or silicon carbide (SiC). In yet another embodiment, the X-ray analysis assembly includes one or more detectors configured to generate a signal in response to the detection of a second X-ray beam, and the window layer is conductive and configured to prevent electrons and charged particles emitted from the sample from: (i) adhering to the sample-facing window surface of the window layer, and (ii) entering one or more detectors.

[0008] In some embodiments, the X-ray analysis assembly includes one or more detectors configured to generate signals in response to the detection of a second X-ray beam, and the system further includes a charge trap integrated within the X-ray housing and configured to prevent electrons and charged particles from entering the detectors. In other embodiments, a sample is placed on a stage configured to move the sample along at least one axis, and the system further includes a processor configured to control the stage to move the sample relative to the X-ray housing along the axis and to position a first surface of the sample at a distance of less than 0.5 mm from a window surface of the window layer facing the first surface. In yet another embodiment, the second pressure includes atmospheric pressure, and the processor is configured to control the flow of helium or nitrogen between the first and second surfaces.

[0009] In some embodiments, the window assembly includes a window layer made of the material formed on an additional layer, and the additional layer: (i) has lower transparency to the first and second X-ray beams compared to the window layer; and (ii) has openings for the passage of the first and second X-ray beams. In other embodiments, the openings are less than 5 mm, and the window layer has a thickness of less than 0.5 μm.

[0010] In some embodiments, the X-ray analysis assembly has an X-ray source comprising: (i) an anode having an anode metal film configured to emit a first X-ray beam having a given energy, the anode metal film (a) having a density greater than 8.3 × 10⁻⁶. 4 (b) The electrical conductivity S / m is formed on a substrate having a thermal conductivity greater than 300 W / (m·K) at 600 °C; and (ii) one or more cathode emitters configured to generate an electron beam directed to an anode to generate a first X-ray beam, the second pressure including atmospheric pressure, and the second X-ray beam including X-ray fluorescence (XRF) emitted from the sample at a depth of less than 1000 nm.

[0011] According to embodiments of the present invention, a method for generating an X-ray analysis system is further provided, the method comprising disposing an X-ray analysis component within an X-ray housing configured to maintain a controlled first pressure, the X-ray analysis component being configured to direct a first X-ray beam toward a sample positioned outside the X-ray housing at a second pressure different from the first pressure, and generating a signal indicating a second X-ray beam emitted from the sample in response to the first X-ray beam impacting the sample. A window assembly is coupled to the X-ray housing, the window assembly being configured to: (i) seal the X-ray housing to maintain a pressure difference between the first and second pressures; and (ii) allow the first and second X-ray beams to pass through, and the window assembly comprising a window layer made of a material transparent to both the first and second X-ray beams.

[0012] The invention will be more fully understood from the following detailed description of embodiments thereof, taken in conjunction with the accompanying drawings, in which: Brief description of the attached diagram

[0013] Figure 1 This is a schematic side view of an X-ray analysis system according to an embodiment of the present invention; and

[0014] Figure 2 This is a schematic illustration of a method for generating according to an embodiment of the present invention. Figure 1 The flowchart of the system's method. Detailed Implementation

[0015] Overview

[0016] Measuring and analyzing semiconductor devices using X-ray analysis systems (such as X-ray fluorescence (XRF) systems) typically requires strict control over X-ray beam characteristics, such as, but not limited to, the X-ray beam energy. In some cases, X-ray applications require positioning the sample in an atmospheric environment; however, it should be noted that the intensity of the X-ray beam is generally reduced in an atmospheric environment compared to a vacuum environment.

[0017] The embodiments of the invention described herein provide methods and systems for achieving accurate and precise measurements of low-energy X-ray fluorescence when a sample is positioned in an atmospheric environment.

[0018] In some embodiments, the system for X-ray analysis (referred to herein as the system for brevity) includes an X-ray analysis assembly having at least the following: (i) an X-ray source configured to direct an X-ray beam to impact a surface of a sample (in this example, a semiconductor wafer on which layers and structures are formed); (ii) X-ray optics configured to control the characteristics and orientation of the X-ray beam; and (iii) a detector subassembly configured to receive fluorescence radiation excited from the sample in response to the impacting X-ray beam. The system also includes a chuck configured to hold the sample and a stage configured to move the sample relative to the X-ray analysis assembly.

[0019] In some embodiments, the static components of the XRF system (e.g., X-ray source, X-ray optics, and X-ray detector) are positioned in an environment with low X-ray absorption, such as in a vacuum or in a helium-filled container. In one embodiment, in both cases (e.g., vacuum or helium), the system's (vacuum) chamber has an opening and includes a rigid window that is transparent to (low-energy) X-rays and is configured to seal the opening of the chamber, thereby maintaining a vacuum in the chamber (i.e., maintaining a pressure difference between the vacuum in the chamber and the atmospheric environment outside the chamber, as described below). In some embodiments, the window is typically made of a ceramic material, such as, but not limited to, a silicon-nitrogen compound, such as Si3N4 or any other suitable compound; or (ii) graphene made of carbon (not a ceramic material) typically extracted from graphite and made of pure carbon; or (iii) a silicon and carbon compound (e.g., SiC). In this embodiment, the window has a thickness of less than about 1 μm (e.g., equal to or less than about 0.5 μm), and the graphene has a film shape. In other embodiments, the window may comprise any other suitable rigid material that is transparent to low-energy X-rays, does not significantly deteriorate upon X-ray exposure, and provides sufficient mechanical strength to withstand and maintain a pressure difference of approximately one (1) atmosphere between the two faces of the window. The window material is chosen to be free of trace amounts of contaminating elements, such as chlorine, which could introduce unwanted X-ray emissions and interfere with measurements of the element of interest.

[0020] In some embodiments, the sample is placed in an atmospheric environment very close to the window. In this example, the distance (also referred to herein as the air gap) between (i) the outer surface of the window and (ii) the outer surface of the sample facing the window is between about 100 μm and 500 μm, or any other suitable distance less than about 1 mm. In this configuration, the X-ray path, excitation, and detection occur primarily in a controlled vacuum environment, with only a small air gap between the sample and the X-ray window, as described above.

[0021] In some embodiments, the system includes a chuck configured to hold the sample and a stage configured to move the sample relative to the X-ray analysis assembly. The movement of the stage is controlled to move laterally, generally parallel to the sample surface (e.g., in the XY plane), and to maintain the aforementioned 100 μm–500 μm air gap during XRF measurements and analysis. In some embodiments, the system includes a proximity sensor configured to output a signal indicating the air gap distance to reduce X-ray attenuation and variations in X-ray energy that may occur due to small fluctuations in the sample's environmental conditions. In some embodiments, and depending on application requirements, the 100 μm–500 μm air gap may additionally be filled with a continuous gas flow (e.g., helium or nitrogen), resulting in less attenuation of X-ray energy compared to using air or other gases, or to remove X-ray spectral lines that may interfere with the measurement, most notably argon (Ar) lines.

[0022] In some embodiments, the window is made of a conductive material, such as SiC and graphene described above, to reduce (and preferably prevent) the entry of electrons (and charged particles) emitted from the sample into the aforementioned detector of the system. Additionally or alternatively, the system includes a magnetically based charge trap integrated within a vacuum chamber, for example, between the sample and the detector, and configured to prevent electrons and charged particles from entering (one or more) the detector(s). The configuration of the window and charge trap is described below. Figure 1 Detailed description is provided.

[0023] System Description

[0024] Figure 1 This is a schematic side view of an X-ray analysis system 11 according to an embodiment of the present invention.

[0025] In some embodiments, system 11 includes an X-ray fluorescence (XRF) analysis system, but at least some of the embodiments described in this disclosure, with necessary modifications, are applicable to other types of X-ray analysis systems and other types of systems for analyzing and / or processing semiconductor-based samples during very large-scale integration (VLSI) processes for manufacturing integrated circuit (IC) devices.

[0026] In some embodiments, system 11 includes (i) an X-ray source 12 configured to receive power from a power supply unit (PSU) 26 and emit an X-ray beam 23 toward sample 30. In this example, sample 30 comprises a silicon wafer having layers and structures patterned using any suitable VLSI process.

[0027] In some embodiments, the X-ray source 12 may comprise a conventional wire-wire electron source or a more advanced system, such as a cold (reservoir) cathode or a LaB6 (also referred to herein as Lab6) emitter (not shown), provided by: (i) Incoatec GmbH, Max-Planck-Str. 2, 21502 Geisthachter, Germany; or (ii) Excillum AB, Jan Stenbecks Torg 17, 164 40 Hista, Sweden.

[0028] In some embodiments, a tube having a cold (storage) and lanthanum hexaboride (LaB6) cathode emitter is configured to emit low-energy X-rays (which can operate at lower voltages (e.g., about 35 kV) and higher currents (e.g., about 1.8 mA) compared to conventional X-ray tubes (such as the aforementioned wire sources). The anode of source 12 (not shown) may comprise the elemental metals rhodium (Rh) or copper (Cu), or an alloy having an X-ray emission line particularly suitable for exciting low-energy X-rays (e.g., Rh Lα emission at about 2.7 keV) in sample 30. The anode metal may be deposited as a film on a substrate with high thermal conductivity (e.g., thick copper, diamond, or silicon carbide (SiC)). In this embodiment, the thermal conductivity of the substrate is greater than 300 W / (m·K) at a temperature of about 600°C.

[0029] In other embodiments, the anode may comprise pure SiC (without any metal) configured to emit a silicon Ka line and some continuous radiation. The advantage of this line is that it does not efficiently excite fluorescence from the thick silicon substrate of the sample, thus facilitating the measurement of emission from thin films deposited on surface 13 of sample 30. For example, when a thin aluminum (or any other) layer (e.g., having a thickness of less than about 50 nm) is deposited on the silicon substrate of sample 30, using a silicon Ka line does not excite fluorescence radiation from the silicon substrate, but rather from the thin aluminum layer, resulting in fluorescence radiation from the thin aluminum layer and low background radiation from the silicon substrate. Therefore, more efficient XRF analysis of the thin aluminum layer is achieved compared to using an anode material other than SiC. For example, based on the sample material, approximately 25% attenuation is obtained in the Rh Lα emission of XRF emitted from sample 30 at depths less than about 100 nm or less than about 1000 nm. In alternative embodiments, system 11 can be used to measure light elements down to the fluorine Ka line, thereby enabling the measurement of thin films of aluminum (K line) and germanium (L line).

[0030] In some embodiments, system 11 includes an X-ray optics 14 disposed between source 12 and sample 30, the X-ray optics 14 being configured to shape beam 23 to form a shaped spot 32, for example, at a predefined measurement site on surface 13 of sample 30. In some embodiments, the X-ray optics 14 can be selected to further optimize the setup for certain applications. For multicolor excitation, for example, single-capillary or multi-capillary optics can be used to provide a high incident flux with a wide range of energies (e.g., approximately a few keV) directed at sample 30. In some applications where low background is more advantageous than high flux, a crystal or multilayer monochromator (not shown) can be used to reduce the energy range to the energies around the characteristic emission lines (e.g., Cu Ka) of the tube.

[0031] In some embodiments, system 11 includes one or more X-ray detectors 16 configured to receive fluorescent radiation, referred herein as beam 25, which is excited from sample 30 in response to the interaction between sample 30 and X-ray beam 23 impacting thereon.

[0032] In some embodiments, system 11 may include approximately four or more detectors 16, which may be arranged in a ring array around optics 14 to increase the detection efficiency of X-rays from beam 25. In some embodiments, at least one (and typically each) detector 16 may include a semiconductor device, such as a silicon drift detector (SDD), connected to an energy dispersion detector that simultaneously measures the intensity of energy across a wide range and outputs a signal to processor 22.

[0033] Additionally or alternatively, at least one detector 16 may be configured in a wavelength dispersion setting having a moving crystal element for selecting one or more discrete energies and a proportional counter for determining the intensity of the selected line. Wavelength dispersion settings typically offer higher energy resolution compared to energy dispersion settings, which can be advantageous for low-energy analysis.

[0034] In some embodiments, the X-ray source 12, X-ray optics 14, and detector 16 are housed within an X-ray housing, which in this example, for simplicity, is within a vacuum chamber 15 (also referred to herein as chamber 15). Furthermore, in the context of this disclosure, the combination of the X-ray source 12, X-ray optics 14, and detector 16 is referred to herein as X-ray analysis assembly 10. In other embodiments, components of the X-ray analysis assembly 10 are positioned in an environment with low X-ray absorption (other than a vacuum), such as in a helium-filled container. In this configuration, vacuum chamber 15 is replaced by a chamber configured to contain helium. In some embodiments, a mixture of the aforementioned energy-dispersive detector and wavelength-dispersive detector may be present within vacuum chamber 15.

[0035] In some embodiments, system 11 includes computer 20, which includes processor 22, interface 24, and display (not shown). Processor 22 is configured to control various parts and components of system 11 as described below and to process electrical signals received from detector 16. Interface 24 is configured to exchange electrical signals between processor 22 and corresponding parts and components of system 11.

[0036] In some embodiments, processor 22 includes a general-purpose computer programmed with software to perform the functions described herein. For example, the software may be downloaded to the computer electronically via a network, or the software may alternatively or additionally be provided and / or stored on a non-transitory tangible medium, such as magnetic storage, optical storage, or electronic storage. Additionally or alternatively, computer 20 includes any suitable type of central processing unit (CPU), or graphics processing unit (GPU), or tensor processing unit (TPU), digital signal processor (DSP), or any other suitable type of application-specific integrated circuit (ASIC). All of the above processing units are specifically configured to accelerate deep learning workloads in neural networks that can be used to analyze signals received from detector 16.

[0037] In some embodiments, system 11 includes a mounting, such as a motorized stage 40 configured to move in one or more of the XYZ directions and to rotate and tilt on a rotation axis and a tilt axis (not shown). System 11 also includes a chuck 21 mounted on stage 40 and configured to hold sample 30. Movement of stage 40 is controlled by processor 22 in the XYZ coordinate system of system 11, as described below, and stage 40 and chuck 21 are designed to allow the incident beam 23 to directly impact surface 13 of sample 30.

[0038] In some embodiments, the stage 40, chuck 21, and sample 30 (and optionally additional movable parts) are placed in an atmospheric environment. As described above, the static components of the X-ray analysis assembly 10 are placed in a vacuum (within the vacuum chamber 15) or in another environment with low X-ray absorption, such as in helium, or with argon gas (which is typically present in the atmosphere at about 1%) removed using near-pure nitrogen to remove parasitic peak signals from argon gas.

[0039] In some embodiments, system 11 includes a rigid window assembly 33 that is transparent to X-rays (of high or low energy, as described below) and is configured to seal an opening in chamber 15 (as described below) to maintain a vacuum (or maintain helium pressure) in chamber 15. In other words, window assembly 33 is configured to seal chamber 15 to maintain (vacuum or helium) pressure and prevent gas leakage into or out of chamber 15. Furthermore, window assembly 33 is configured to allow the following to pass: (i) the X-ray beam 23 out of chamber 15; and (ii) the low-energy fluorescence beam 25 into chamber 15. As described above, beam 25 is excited from sample 30 in response to the interaction between sample 30 and X-ray beam 23. The spectral intensity of the X-ray fluorescence indicates the elemental composition of one or more layers in sample 30 at the shaped spot 32. It should be noted that beam 25 propagates in an atmospheric environment that absorbs some energy, thereby reducing the energy of beam 25. System 11 is configured to operate with a low-energy beam 25, typically ranging from about 0.6 keV to 3 keV.

[0040] In some embodiments, system 11 includes cable 52 configured to connect processor 22 (via interface 20) to: (i) PSU 26 and / or X-ray source 12 to control the size, shape, intensity, and orientation of beam 23; (ii) detector 16 to receive a signal indicating beam 25 emitted from sample 30 and detected by detector 16; (iii) distance sensor 18 to measure the distance between window assembly 33 and sample 30 (as will be described in detail below); and (iv) stage 40 to control the movement and position of sample 30 relative to X-ray analysis assembly 10 via closed-loop control.

[0041] In some embodiments, additional sensors (such as, but not limited to, pressure sensors, temperature sensors, and humidity sensors) may be incorporated into system 11 to monitor environmental conditions in the gap (with a distance 66 described below) between the surface 29 of window layer 55 and the surface 13 of sample 30. In some embodiments, readings from these sensors may be included in measurement data analysis to illustrate changes in the environment surrounding sample 30 over time.

[0042] Referring now to Illustration 19, a portion of window assembly 33 and sample 30 having surface 13 is shown. In some embodiments, window assembly 33 includes window layer 55, which is typically made of materials such as, but not limited to, those comprising: (i) silicon-nitrogen compounds (e.g., Si3N4 or any other suitable compound); or (ii) graphene, a material typically extracted from graphite and composed of pure carbon or SiC. The stiffness of silicon-nitrogen and graphene is determined using Young's modulus (E), which is calculated using equation (i).

[0043] (i)E=σ / ε

[0044] Where σ represents the tensile stress applied to window layer 55,

[0045] And ε represents the tensile strain generated on the window layer 55 in response to the applied tensile stress.

[0046] In this example, the Young's modulus of Si3N4 at about 20°C is between about 100 GPa and 325 GPa, the Young's modulus of SiC at about 20°C is between about 400 GPa and 700 GPa, and the Young's modulus of graphene at about 20°C is between about 1 TPa and 2.5 TPa. In some embodiments, the window layer 55 is made of Si3N4 supplied by Norcada Corporation, 4548-99, Edmonton, Alberta, Canada (Zicode T6E 5H5), and has a thickness 77 of less than about 1 μm (e.g., between about 0.4 μm and 0.7 μm).

[0047] In an alternative embodiment, window layer 55 is made of graphene. Example materials for window layer 55, such as Si3N4, graphene, and SiC, are transparent to beams 23 and 25 and are conductive, as described below. In other embodiments, window layer 55 may comprise any other suitable rigid material (e.g., beryllium) that is transparent to both low-energy and high-energy X-rays. Beryllium has a Young's modulus of approximately 300 GPa at about 20 °C.

[0048] In such embodiments, all materials selected for window layer 55 (e.g., Si3N4, SiC, beryllium, and graphene) are: (i) transparent to X-ray radiation; (ii) stable under X-ray exposure; and (iii) have high stiffness with a Young's modulus greater than 100 GPa. It is important to note that this high stiffness is crucial for preventing significant bending of window layer 55 when operating under vacuum conditions, which is essential for minimizing the air gap and thus reducing the travel of X-rays outside the vacuum and improving the performance of the X-ray analysis system.

[0049] In some embodiments, window assembly 33 further includes a layer 44 made of silicon or any other material. Layer 44 has a thickness 34 (e.g., between about 0.3 mm and 1 mm) and is coupled to window layer 55. In some embodiments, window assembly 33 is fabricated by depositing a layer of silicon-nitrogen, graphene, or SiC on layer 44. Subsequently, an opening 36 is etched in layer 44, in this example, the opening 36 having a length between about 2 mm and 5 mm (typically less than about 3 mm) along the X-axis (and typically also along the Y-axis). It should be noted that chamber 15 has an opening of the same size as opening 36. Since this fabrication process is provided by way of example, and in other embodiments, any other suitable process may be used to fabricate window assembly 33. In some embodiments, window assembly 33 has a circular shape such that opening 36 is the inner diameter of window assembly 33, and the outer diameter 67 of window assembly 33 is between about 4 mm and 6 mm (typically about 5 mm).

[0050] In some embodiments, the stage 30 is configured to place the outer surface 13 of the sample 30 at a distance 66 (also referred to herein as an air gap) from the outer surface 29 of the window layer 55. In this example, the distance 66 has a length along the Z-axis between approximately 100 μm and 500 μm, or any other suitable distance less than approximately 1 mm. It should be noted that in this configuration, respectively, (i) the first portion of the paths of beams 23 and 25 and the detection of beam 25 are performed in a controlled vacuum environment, and (ii) the second portion of beams 23 and 25 (substantially smaller than the first portion) and the excitation of beam 25 from surface 13 occur in a small (approximately 100 μm and 500 μm) air gap between surface 13 of the sample 30 and surface 29 of the window 55.

[0051] In some embodiments, the high stiffness of silicon-nitrogen, graphene, and SiC (determined by the Young's modulus described above) combined with the small size of the opening 36 (e.g., less than about 3 mm) allows the surface 29 of the window layer 55 to be substantially parallel to the surface 13 of the sample 30 in the XY plane of the XYZ coordinate system. Furthermore, improved flatness of the surface 29 in the XY plane can be obtained by increasing the thickness 77 of the window layer 55 by a few nanometers or tens of nanometers.

[0052] In some embodiments, system 11 further includes a distance sensor 18 coupled to chamber 15 and configured to measure distance 66 between surfaces 13 and 29. In one embodiment, distance sensor 18 includes a laser triangulation or confocal white light sensor, wherein the reading time frequency for each measurement site is less than about 1 second, and the resolution and accuracy of the displacement are less than about 1 μm.

[0053] In some embodiments, processor 22 is configured to control the movement of stage 40 approximately in the XY plane (approximately parallel to surface 13 of sample 30) and to maintain the aforementioned air gap (distance 66) of 100 μm to 500 μm during XRF measurements and analysis. In some embodiments, distance sensor 18 (also referred to herein as a proximity sensor) is configured to output a signal indicating the air gap distance 66 to reduce X-ray attenuation in beams 23 and 25 and variations in the energy of beams 23 and 25 that may occur due to small fluctuations in environmental conditions surrounding sample 30. In some embodiments, processor 22 is configured to control the supply of a continuous gas flow such as helium or nitrogen (to remove parasitic peak signals from argon as described above), causing less attenuation of the energy of beam 25 compared to the attenuation of the energy of beam 25 in the presence of air or other gases in the air gap (distance 66).

[0054] In some embodiments, the window assembly 33 is made of a conductive material, such as the graphene layer of the window layer 55 having about 10 6 The conductivity, on the order of Siemens per meter (S / m), and the conductivity of the silicon and SiC layers 44, are determined by the type and concentration of dopants embedded in the silicon and SiC matrices. For example, using a high concentration of boron dopants can achieve sufficiently high conductivity in the silicon layer, such as approximately 8.3 × 10⁻⁶. 4 S / m. In some embodiments, this configuration reduces (and preferably prevents) electrons (and charged particles) emitted from surface 13 of sample 30 from undesirably adhering to the outer surface 29 of window layer 55 and / or entering detector(s)(one or more) and thus interfering with the detection accuracy of beam 25. Additionally or alternatively, system 11 includes a magnetically based charge trap (MT) 88 integrated within vacuum chamber 15, for example, between (i) surface 31 of window layer 55 and (ii) detector 16. In this embodiment, MT 88 includes (e.g., made of copper) a conductive coil arranged in a plane parallel to the surface 39 of one or more of detectors 16 to trap any electrons and / or charged particles directed toward detector 16.

[0055] In some embodiments, after the XRF measurement is completed, the processor 22 is configured to control the stage 40 to unload the sample 30 and upload the next sample 30 intended for XRF measurement by the system 11. The arrangement of the sample 30 in the atmospheric environment (i.e., outside the vacuum chamber 15) eliminates the need to load, lock, and evacuate the vacuum chamber 15 for each new sample 30.

[0056] In some embodiments, the configuration of system 11 can be used as part of a multi-channel system, such as including two or more micro-XRF (μXRF) channels with different X-ray sources, optics, and / or operating conditions (e.g., voltage, current, spot size) to optimize measurements of different materials in sample 30. In such embodiments, system 11 can be used as an XRF measurement channel in combination with systems implementing other measurement techniques, such as, but not limited to, X-ray methods (e.g., high-resolution X-ray diffraction (HR XRD), X-ray reflection (XRR), X-ray photoelectron spectroscopy (XPS), and small-angle X-ray spectroscopy (SAXS)) and optical measurement techniques (e.g., reflectance measurements, optical scattering measurements, and Raman spectroscopy).

[0057] In some embodiments, based on the disclosed techniques and system 11 configuration, a large portion of the path of the XRF emitted from sample 30 travels through a vacuum, thereby allowing the analysis of low-Z elements (e.g., elements with atomic weights less than about 20), such as aluminum, phosphorus, sodium, magnesium, sulfur, and chlorine, using K-shell X-ray emission lines of low-Z elements. Furthermore, the disclosed techniques and system 11 configuration allow for XRF analysis of some materials with atomic weights greater than about 30 using lower-energy emission lines (such as L-shell X-rays) to analyze these materials. In such embodiments, the thickness of the aforementioned material layers is typically between about 5 angstroms and 1 μm.

[0058] This particular configuration of System 11 is shown by way of example to illustrate certain problems solved by embodiments of the present invention and to demonstrate the application of these embodiments in enhancing the performance of such XRF analysis systems. However, embodiments of the present invention are by no means limited to this particular type of example system, and the principles described herein can be similarly applied to other types of X-ray analysis systems known in the art.

[0059] Figure 2 This is a flowchart illustrating a method for generating system 11 according to an embodiment of the present invention.

[0060] The method begins with window assembly fabrication step 100, in which a window assembly 33 having an opening 36 and a window layer 55 is fabricated, the thickness of which is between approximately 0.4 μm and 0.7 μm, as described above. Figure 1 Detailed description is provided.

[0061] In step 102 of setting up the X-ray analysis assembly, the X-ray analysis assembly 10 (including the X-ray source 12, X-ray optics 14, and detector 16) is placed in the X-ray housing (also referred to herein as chamber 15), as described above. Figure 1 Detailed description is provided.

[0062] At sealing step 104, the chamber 15 is sealed by coupling the window assembly 33 to an opening in the chamber 15 having the same dimensions as the aforementioned opening 36, as described above. Figure 1 Detailed description is provided.

[0063] At sensor coupling step 106, distance sensor 18 is coupled to chamber 15. In some embodiments, distance sensor 18 is configured to measure distance 66 between surface 13 of sample 30 and surface 29 of window layer 55, as described above. Figure 1 Detailed description is provided.

[0064] At the connection step 108 at the end of the method, the processor 22 is connected to: (i) a stage 40 and a distance sensor 18 for controlling the distance 66 between the surface 13 of the sample 30 and the surface 29 of the window layer 55; and (ii) an X-ray source 12 and a detector 16 of the X-ray analysis assembly 10 to guide the X-ray beam 23 toward the sample 30 and to receive from the detector 16 a signal indicating the XRF beam 25 emitted from the sample 30 in response to the beam 23 striking the surface 13, as described above. Figure 1 Detailed description is provided.

[0065] Therefore, it should be understood that the above embodiments are cited by way of example, and the invention is not limited to what has been specifically shown and described above. Rather, the scope of the invention includes combinations and sub-combinations of the various features described above, as well as variations and modifications of the invention that would be conceived by one of skill in the art upon reading the above description and that are not disclosed in the prior art. Documents incorporated herein by reference are considered part of this application, and the definitions in this specification should be considered only, unless any terms are defined in these incorporated documents in a manner that conflicts to some extent with the definitions expressly or implicitly made in this specification.

Claims

1. A system for X-ray analysis, the system comprising: X-ray analysis assembly, the X-ray analysis assembly: (i) is disposed in an X-ray housing configured to maintain a controlled first pressure, and (ii) is configured to direct a first X-ray beam toward a sample positioned outside the X-ray housing at a second pressure different from the first pressure, and generate a signal indicating a second X-ray beam emitted from the sample in response to the first X-ray beam striking the sample; as well as A window assembly disposed between the X-ray analysis assembly and the sample, and configured to: (i) seal the X-ray housing to maintain a pressure difference between the first pressure and the second pressure, and (ii) allow the first X-ray beam and the second X-ray beam to pass through, wherein the window assembly includes a window layer made of a material transparent to the first X-ray beam and the second X-ray beam.

2. The system according to claim 1, wherein, The window layer comprises a silicon-nitrogen compound.

3. The system according to claim 1, wherein, The window layer comprises a film of graphene or silicon carbide (SiC).

4. The system according to claim 1, wherein, The X-ray analysis assembly includes one or more detectors configured to generate the signal in response to the detection of the second X-ray beam, wherein the window layer is conductive and configured to prevent electrons and charged particles emitted from the sample from: (i) adhering to the sample-facing window surface of the window layer, and (ii) entering the one or more detectors.

5. The system according to claim 1, wherein, The X-ray analysis assembly includes one or more detectors configured to generate the signal in response to the detection of the second X-ray beam, and includes a charge trap integrated within the X-ray housing and configured to prevent electrons and charged particles from entering the one or more detectors.

6. The system according to any one of claims 1 to 5, wherein, The sample is placed on a stage configured to move the sample along at least one axis, and the system includes a processor configured to control the stage to move the sample relative to the X-ray housing along the axis and to position a first surface of the sample at a distance of less than 0.5 mm from a window surface of the window layer facing the first surface.

7. The system according to claim 6, wherein, The second pressure includes atmospheric pressure, and the processor is configured to control the flow of helium or nitrogen between the first surface and the second surface.

8. The system according to any one of claims 1 to 5, wherein, The window assembly includes the window layer made of the material, the window layer being formed on an additional layer, wherein the additional layer: (i) has lower transparency to the first X-ray beam and the second X-ray beam compared to the window layer; and (ii) has openings for allowing the first X-ray beam and the second X-ray beam to pass through.

9. The system according to claim 8, wherein, The opening is less than 5 mm, and the window layer has a thickness of less than 0.5 μm.

10. The system according to any one of claims 1 to 5, wherein, The X-ray analysis assembly has an X-ray source comprising: (i) an anode having an anode metal film configured to emit a first X-ray beam having a given energy, the anode metal film (a) having a density greater than 8.3 × 10⁻⁶. 4 (i) an electrical conductivity of S / m and (b) formed on a substrate having a thermal conductivity greater than 300 W / (m·K) at 600 °C; and (ii) one or more cathode emitters configured to generate an electron beam directed to the anode to generate the first X-ray beam, wherein the second pressure includes atmospheric pressure, and wherein the second X-ray beam includes X-ray fluorescence (XRF) emitted from the sample at a depth of less than 1000 nm.

11. A method for generating an X-ray analysis system, the method comprising: An X-ray analysis component is disposed within an X-ray housing configured to maintain a controlled first pressure. The X-ray analysis component is configured to direct a first X-ray beam toward a sample positioned outside the X-ray housing at a second pressure different from the first pressure, and to generate a signal indicating a second X-ray beam emitted from the sample in response to the first X-ray beam striking the sample. as well as A window assembly is coupled to the X-ray housing, the window assembly being configured to: (i) seal the X-ray housing to maintain a pressure difference between the first pressure and the second pressure; (ii) allowing the first X-ray beam and the second X-ray beam to pass through, wherein the window assembly includes a window layer made of a material that is transparent to the first X-ray beam and the second X-ray beam.

12. The method according to claim 11, wherein, The window assembly is coupled by coupling the window layer made of a silicon-nitrogen compound.

13. The method according to claim 11, wherein, The window assembly is coupled by coupling the window layer, which is made of a film of graphene or silicon carbide (SiC).

14. The method according to claim 11, wherein, Setting up the X-ray analysis assembly includes setting up one or more detectors configured to generate the signal in response to the detection of the second X-ray beam, and wherein coupling the window assembly includes coupling the window layer, the window layer being conductive and configured to prevent electrons and charged particles emitted from the sample from: (i) adhering to the sample-facing window surface of the window layer, and (ii) entering the one or more detectors.

15. The method according to claim 11, wherein, The X-ray analysis assembly includes providing one or more detectors configured to generate the signal in response to the detection of the second X-ray beam, and integrating a charge trap within the X-ray housing, the charge trap being configured to prevent electrons and charged particles from entering the one or more detectors.

16. The method of any one of claims 11 to 15, further comprising placing the sample on a stage configured to move the sample along at least one axis, and connecting the stage to a processor configured to control the stage to move the sample relative to the X-ray housing along the axis, and positioning a first surface of the sample at a distance of less than 0.5 mm from the window surface of the window layer facing the first surface.

17. The method according to claim 16, wherein, The second pressure includes atmospheric pressure, and the method includes connecting the processor to helium or nitrogen to control the flow of helium or nitrogen between the first surface and the second surface, respectively.

18. The method of any one of claims 11 to 15, further comprising forming the window assembly by forming a window layer over an additional layer, the additional layer having lower transparency to the first X-ray beam and the second X-ray beam compared to the window layer, and forming an opening in the additional layer for allowing the first X-ray beam and the second X-ray beam to pass through.

19. The method according to claim 18, wherein, Forming the opening includes forming the opening less than 5 mm, and wherein forming the window layer includes depositing the window layer having a thickness of less than 0.5 μm.

20. The method according to any one of claims 11 to 15, wherein, Setting up the X-ray analysis assembly includes setting up an X-ray source, the X-ray source comprising: (i) an anode having an anode metal film configured to emit a first X-ray beam having a given energy, the anode metal film (a) having a density greater than 8.3 × 10⁻⁶. 4 (i) an electrical conductivity of S / m and (b) formed on a substrate having a thermal conductivity greater than 300 W / (m·K) at 600 °C; and (ii) one or more cathode emitters configured to generate an electron beam directed to the anode to generate the first X-ray beam, wherein the second pressure includes atmospheric pressure, and wherein the second X-ray beam includes X-ray fluorescence (XRF) emitted from the sample at a depth of less than 1000 nm.

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