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

Abstract

To provide a system for X-ray analysis.SOLUTION: A system for X-ray analysis includes (a) an X-ray analysis assembly, which is (i) disposed in an X-ray enclosure configured to maintain a controlled first pressure, and (ii) configured to direct a first X-ray beam toward a sample positioned out of the X-ray enclosure at a second pressure different from the first pressure, and to produce a signal indicative of a second X-ray beam emitted from the sample in response to the first X-ray beam impinging on the sample, and (b) a window assembly, which is disposed between the X-ray analysis assembly and the sample and is configured to (i) seal the X-ray enclosure to maintain a pressure difference between the first and second pressures, and (ii) pass the first and second X-ray beams, and the window assembly includes a window layer made from a material transparent to the first and second X-ray beams.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 649,378, filed May 19, 2024, the disclosure of which is incorporated herein by reference.

[0002] The present invention relates generally to X-ray analysis, and more particularly to a method and system for analyzing low energy X-ray fluorescence emitted from a sample located in an atmospheric environment. [Background technology]

[0003] Various techniques have been developed to measure the X-ray fluorescence emitted from samples placed in an atmospheric environment.

[0004] For example, Japanese Patent Application No. 2001-105636 describes an X-ray fluorescence analyzer that includes a measurement unit and a movable unit, where the measurement unit includes a first opening, a measurement chamber, an X-ray source that irradiates primary X-rays toward the first opening, an X-ray detector that detects secondary X-rays, an intake / exhaust means that intake / exhaust the measurement chamber, and a gas introduction means that introduces gas into the measurement chamber. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Application No. 2001-105636 Summary of the Invention

[0006] Embodiments of the invention described herein provide a system for X-ray analysis, including: (a) an X-ray analysis assembly configured to (i) be disposed within an X-ray enclosure configured to maintain a controlled first pressure; and (ii) direct a first X-ray beam toward a sample disposed outside the X-ray enclosure 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 impinging on the sample; and (b) a window assembly disposed between the X-ray analysis assembly and the sample; (i) seal the X-ray enclosure to maintain a pressure differential between the first pressure and the second pressure; and (ii) transmit the first and second X-ray beams, the window assembly including a window layer formed from a material transparent to the first and second X-ray beams.

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

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

[0009] In some embodiments, the window assembly includes a window layer formed from the above material, the window layer formed on an additional layer, the additional layer (i) being less transparent to the first and second X-ray beams than the window layer, and (ii) having an opening for the passage of the first and second X-ray beams. In other embodiments, the opening is 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 comprises: (i) an anode metal membrane configured to emit a first X-ray beam having a predetermined energy, (a) 8.3×10 4 an X-ray source including: (a) an anode having an anode metal film formed on a base layer having a thermal conductivity greater than 300 W / (m·K) at 600°C; and (b) one or more cathode emitters configured to generate an electron beam directed at the anode to generate a first X-ray beam, wherein the second pressure comprises atmospheric pressure, and the second X-ray beam comprises X-ray fluorescence (XRF) emitted from the sample at a depth of less than 1000 nm.

[0011] According to an embodiment of the present invention, a method for manufacturing an X-ray analysis system includes disposing, within an X-ray enclosure configured to maintain a controlled first pressure, an X-ray analysis assembly configured to direct a first X-ray beam toward a sample disposed outside the X-ray enclosure at a second pressure different from the first pressure, and to generate a signal indicative of a second X-ray beam emitted from the sample in response to the first X-ray beam impinging on the sample, wherein the X-ray enclosure is coupled to a window assembly configured to seal the X-ray enclosure and maintain a pressure differential between the first pressure and the second pressure, and (ii) to transmit the first and second X-ray beams, the window assembly including a window layer formed from a material transparent to the first and second X-ray beams.

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

[0013] [Figure 1] 1 is a schematic side view of an X-ray analysis system according to an embodiment of the present invention. [Figure 2] 2 is a flow chart that schematically illustrates a method for manufacturing the system of FIG. 1, in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] overview Measurement and analysis of semiconductor devices using X-ray analytical systems, such as X-ray fluorescence (XRF) systems, typically require strict control of X-ray beam characteristics, including but not limited to X-ray beam energy. In some cases, X-ray applications require the sample to be placed in an atmospheric environment, which typically reduces the intensity of the X-ray beam compared to a vacuum environment.

[0015] DETAILED DESCRIPTION OF THE INVENTION The embodiments of the present invention described herein provide methods and systems that enable accurate and precise measurements of low energy X-ray fluorescence while the sample is located in an air environment.

[0016] In some embodiments, a system for X-ray analysis (also referred to herein as a system for brevity) includes an X-ray analysis assembly having at least (i) an X-ray source configured to direct and impinge an X-ray beam on a surface of a sample (in this example, a semiconductor wafer with layers and structures formed thereon), (ii) X-ray optics configured to control the properties and direction of the X-ray beam, and (iii) a detector subassembly configured to receive excited fluorescent radiation from the sample in response to the impinging X-ray beam. The system further includes a chuck configured to hold the sample and a stage configured to move the sample relative to the X-ray analysis assembly.

[0017] In some embodiments, the static components of the X-ray fluorescence analysis system (e.g., the X-ray source, X-ray optics, and X-ray detector) are placed in a low X-ray absorption environment, such as a vacuum or a helium-filled tank. In certain embodiments, in either case (e.g., vacuum or helium), the (vacuum) chamber of the system has an opening and includes a rigid window that is transparent to (low-energy) X-rays and configured to seal the chamber opening and thereby maintain the vacuum within the vacuum chamber (i.e., maintain a pressure difference between the vacuum within the chamber and the atmospheric environment outside the chamber, as described below). In some embodiments, the window is typically formed from a ceramic material, such as, but not limited to, (i) a silicon nitride compound such as Si3N4 or any other suitable compound, or (ii) graphene, which is composed of pure carbon and is typically formed from carbon extracted from graphite (a non-ceramic material), or (iii) a silicon and carbide compound (e.g., SiC). In this example, the window has a thickness of less than about 1 μm (e.g., about 0.5 μm or less), and the graphene has the shape of a film. In other embodiments, the window can comprise any other suitable rigid material that is transparent to low energy x-rays without significant degradation upon x-ray exposure and that provides sufficient mechanical strength to withstand and maintain a pressure differential of about 1 atmosphere across the window. The window material is selected to be free of small amounts of contaminating elements, such as chlorine, that can introduce undesirable x-ray emissions and interfere with the measurement of the element of interest.

[0018] In some embodiments, the sample is placed in an atmospheric environment in close proximity to the window. In this example, the distance between (i) the exterior surface of the window and (ii) the exterior surface of the sample facing the window (also referred to herein as the air gap) is between about 100 μm and 500 μm, or any other suitable distance less than about 1 mm. In this configuration, the majority of the x-ray path, excitation, and detection occurs in a controlled vacuum environment with only a small air gap between the sample and the x-ray window, as described above.

[0019] 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 stage movement is controlled to move laterally (e.g., in the XY plane) approximately parallel to the surface of the sample, maintaining the aforementioned 100 μm to 500 μm air gap while performing XRF measurements and analysis. In some embodiments, the system includes a proximity sensor configured to output a signal indicative of the air gap distance to reduce variations in X-ray attenuation and X-ray energy that may occur due to slight variations in ambient conditions of the sample. In some embodiments, depending on application requirements, the 100 μm to 500 μm air gap can be flooded with a continuous flow of gas, such as helium or nitrogen, to reduce X-ray energy attenuation compared to that of air or other gases or to eliminate X-ray lines that may interfere with measurements, such as argon (Ar), among others.

[0020] In some embodiments, the window is formed from a conductive material, such as SiC and graphene, as described above, to reduce (and preferably prevent) electrons (and charged particles) emitted from the sample from entering the detector(s) of the system. Additionally or alternatively, the system also includes a magnetic-based charge trap, such as integrated between the sample and the detector in the vacuum chamber, configured to prevent electrons and charged particles from entering the detector. The configuration of the window and charge trap is described in more detail in FIG. 1 below.

[0021] System Description FIG. 1 is a schematic side view of an X-ray analysis system 11 according to an embodiment of the present invention.

[0022] In some embodiments, system 11 comprises an X-ray fluorescence (XRF) analysis system, although at least some of the embodiments described in this disclosure are applicable mutatis mutandis to other types of X-ray analysis systems and other types of systems used to analyze and / or process semiconductor-based samples during very large scale integration (VLSI) processes for manufacturing integrated circuit (IC) devices.

[0023] 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 a sample 30. In this example, sample 30 includes a silicon wafer having layers and structures patterned using any suitable VLSI process.

[0024] In some embodiments, the x-ray source 12 may include a conventional wire filament source of electrons, or a more advanced system such as a cold (dispenser) cathode or LaB6 (also referred to herein as Lab6) emitter (not shown) supplied by (i) Incotec GmbH, Max-Planck-Str. 2, 21502 Geesthacht, Germany, or (ii) Excillum AB, Jan Stenbecks Torg 17, 164 40 Kista, Sweden.

[0025] In some embodiments, tubes with cold (dispenser) and lanthanum hexaboride (LaB6) cathode emitters are configured to emit low-energy X-rays that can be operated at lower voltages (e.g., about 35 kV) and higher currents (e.g., about 1.8 mA) than conventional X-ray tubes, such as the wire filament sources described above. The anode (not shown) of the source 12 can include the elemental metals rhodium (Rh) or copper (Cu), or alloys, which have X-ray emission lines particularly suitable for exciting low-energy X-rays (e.g., Rh Lα emission at about 2.7 keV) in the sample 30. The anode metal can be deposited as a film on a base layer with high thermal conductivity, such as thick copper, diamond, or silicon carbide (SiC). In this example, the thermal conductivity of the base layer is greater than 300 W / (m·K) at a temperature of about 600°C.

[0026] In other embodiments, the anode can comprise pure (metal-free) SiC configured to emit the silicon Ka line and some continuum radiation. This line has the advantage of not efficiently exciting fluorescence from the thick silicon substrate of the sample, thereby facilitating measurement of emissions from thin films deposited on the surface 13 of the 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 the sample 30, the silicon Ka line can be used to excite fluorescence radiation from the thin aluminum layer without exciting fluorescence radiation from the silicon substrate, thereby providing fluorescence radiation from the thin aluminum layer with low background radiation from the silicon substrate. This can make XRF analysis of thin aluminum layers more effective than using anode materials other than SiC. For example, at depths of less than about 100 nm or less than about 1000 nm, the XRF Rh Lα emission from the sample 30 can be attenuated by about 25%, depending on the sample material. In another embodiment, system 11 can be used to measure light elements down to the fluorine K-line, thus enabling measurement of thin films of aluminum (K-line) and germanium (L-line).

[0027] In some embodiments, the system 11 includes X-ray optics 14 positioned between the light source 12 and the sample 30 and configured to shape the beam 23, for example, to form a shaped spot 32 at a predetermined measurement site on the surface 13 of the sample 30. In some embodiments, the X-ray optics 14 can be selected to further optimize the settings for a particular application. For example, for polychromatic excitation, mono- or polycapillary optics can be used to provide a high incident flux directed at the sample 30 over a wide range of energies (e.g., on the order of a few keV). 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 energies near characteristic emission lines from tubes such as Cu Ka.

[0028] In some embodiments, the system 11 includes one or more X-ray detectors 16 configured to receive fluorescent radiation, referred to herein as beam 25, excited from the sample 30 in response to an interaction between the sample 30 and an X-ray beam 23 impinging on the sample 30.

[0029] In some embodiments, system 11 may include about four or five or more detectors 16 that may be arranged in an annular array around optics 14 to increase the efficiency of detecting the x-rays in 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-dispersive detector, that simultaneously measures intensities across a wide range of energies and outputs signals to processor 22.

[0030] Additionally or alternatively, at least one detector 16 may be configured with a wavelength-dispersive setup including a moving crystal element for selecting one or more discrete energies and a proportional counter for determining the intensities of the selected lines. Wavelength-dispersive setups typically have higher energy resolution than energy-dispersive setups and are advantageous for low-energy analysis.

[0031] In some embodiments, the X-ray source 12, X-ray optics 14, and detector 16 reside within an X-ray enclosure, in this example a vacuum chamber 15, which for brevity is 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 as the X-ray analysis assembly 10. In other embodiments, the components of the X-ray analysis assembly 10 are located in a low X-ray absorption environment (other than a vacuum), such as within a tank filled with helium. In this configuration, the vacuum chamber 15 is replaced with a chamber configured to contain helium gas. In some embodiments, a mixture of the energy-dispersive and wavelength-dispersive detectors described above can reside within the vacuum chamber 15.

[0032] In some embodiments, system 11 includes a computer 20 including a processor 22, an interface 24, and a display (not shown). Processor 22 is configured to control the various components and assemblies 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 each component and assembly of system 11.

[0033] In some embodiments, processor 22 includes a general-purpose computer programmed with software to perform the functions described herein. The software can be downloaded to the computer in electronic form, for example, over a network, or can additionally or alternatively be provided and / or stored on a non-transitory tangible medium, such as magnetic, optical, or electronic memory. Additionally or alternatively, computer 20 can include any suitable type of central processing unit (CPU), or a graphical processing unit (GPU), or a tensor processing unit (TPU), a digital signal processor (DSP), or any other suitable type of application-specific integrated circuit (ASIC). All of the above processing units are configured to, among other things, accelerate deep learning workloads in neural networks that can be used to analyze signals received from detector 16.

[0034] In some embodiments, system 11 includes a mount, such as a motorized stage 40 configured to move in one or more of the X, Y, and Z directions and to rotate and tilt about rotation and tilt axes (not shown). System 11 further includes a chuck 21 attached to stage 40 and configured to hold sample 30. Movement of stage 40 is controlled in the X, Y, and Z coordinate system of system 11 by processor 22, as described below, and stage 40 and chuck 21 are designed to allow incident beam 23 to impinge directly on surface 13 of sample 30.

[0035] In some embodiments, the stage 40, chuck 21, and sample 30 (and optionally further moving components) are located in an atmospheric environment. As noted above, the static components of the X-ray analysis assembly 10 are located in a vacuum (in the vacuum chamber 15) or another environment with low X-ray absorption, such as helium gas, or in which argon gas (typically present in atmospheric air at about 1%) has been removed with nearly pure nitrogen gas to remove parasitic peak signals from argon.

[0036] In some embodiments, the system 11 includes a rigid window assembly 33 that is transparent to X-rays (having high or low energy, as described below) and configured to seal an opening (described below) in the chamber 15 to maintain a vacuum (or helium gas pressure) within the chamber 15. In other words, the window assembly 33 is configured to seal the chamber 15 to maintain the pressure (vacuum or helium gas) and prevent gas leakage into or out of the chamber 15. Additionally, the window assembly 33 is configured to allow (i) the passage of the X-ray beam 23 from within the chamber 15 to the outside, and (ii) the passage of the low-energy fluorescent beam 25 into the chamber 15. As described above, the beam 25 is excited from the sample 30 in response to interaction of the sample 30 with the X-ray beam 23. The spectral intensity of the fluorescent X-rays indicates the elemental composition of one or more layers within the sample 30 at the shaped spot 32. Note that the beam 25 propagates in an atmospheric environment, which absorbs a portion of its energy and thereby reduces the energy of the beam 25. System 11 is configured to operate with a low energy beam 25, with a typical low energy range being between about 0.6 keV and 3 keV.

[0037] In some embodiments, the system 11 includes a cable 52 configured to connect (via the interface 24) between the processor 22 and (i) the PSU 26 and / or X-ray source 12 for controlling the size, shape, intensity, and direction of the beam 23, (ii) the detector 16 for receiving signals indicative of the beam 25 emitted from the sample 30 and detected by the detector 16, (iii) a distance sensor 18 for measuring the distance between the window assembly 33 and the sample 30 (described in more detail below), and (iv) a stage 40 for controlling the movement and position of the sample 30 relative to the X-ray analysis assembly 10 via closed-loop control.

[0038] In some embodiments, additional sensors, such as, but not limited to, pressure sensor(s), temperature sensor(s), and humidity sensor(s), may be incorporated into the system 11 to monitor environmental conditions in the gap (having a distance 66, described below) between the surface 29 of the window layer 55 (described in more detail below) and the surface 13 of the sample 30. In some embodiments, readings from these sensors may be included in the measurement data analysis to account for changes over time in the environment surrounding the sample 30.

[0039] Reference is now made to inset 19, which shows a window assembly 33 and a portion of sample 30 having surface 13. In some embodiments, window assembly 33 includes a window layer 55 formed from a material such as, but not limited to, (i) a silicon nitride compound (e.g., Si3N4 or any other suitable compound), or (ii) graphene, a material usually derived from graphite and composed of pure carbon or SiC. The stiffness of silicon nitride and graphene is determined using Young's modulus (E), which is calculated using equation (i) below: (i) E = σ / ε where σ represents the tensile stress applied to the window layer 55, ε denotes the tensile strain that occurs in the window layer 55 in response to an applied tensile stress.

[0040] In this example, the Young's modulus of Si3N4 at about 20° C. is about 100 GPa to 325 GPa, the Young's modulus of SiC at about 20° C. is about 400 GPa to 700 GPa, and the Young's modulus of graphene at about 20° C. is about 1 TPa to 2.5 TPa. In some embodiments, the window layer 55 is formed from Si3N4 supplied by Norcada, Inc., 4548-99 Edmonton, AB T6E 5H5, Canada, and has a thickness 77 of less than about 1 μm (e.g., about 0.4 μm to 0.7 μm).

[0041] In another embodiment, window layer 55 is formed from graphene. Exemplary materials for window layer 55, Si3N4, graphene, and SiC, are transparent to beams 23 and 25 and are electrically conductive, as described below. In other embodiments, window layer 55 can comprise any other suitable rigid material that is transparent to low-energy and high-energy x-rays, such as beryllium. Beryllium has a Young's modulus of about 300 GPa at about 20°C.

[0042] In such an embodiment, the materials selected for the window layer 55, such as Si3N4, SiC, beryllium, and graphene, are all (i) transparent to X-ray radiation, (ii) stable under X-ray exposure, and (iii) highly stiff with a Young's modulus greater than 100 GPa. Note that high stiffness is important to prevent significant warping of the window layer 55 when operating under vacuum conditions, which is crucial for minimizing air gaps and thereby reducing non-vacuum X-ray transport and improving the performance of the X-ray analysis system.

[0043] In some embodiments, the window assembly 33 further includes a layer 44 formed from silicon or any other material. The layer 44 has a thickness 34 (e.g., about 0.3 mm to 1 mm) and is bonded to the window layer 55. In some embodiments, the window assembly 33 is fabricated by depositing a layer of silicon nitride, graphene, or SiC on the layer 44. An opening 36 is then etched into the layer 44, in this example, having a length along the X-axis (and typically also along the Y-axis) of about 2 mm to 5 mm (typically less than about 3 mm). Note that the chamber 15 has an opening of the same size as the opening 36. This manufacturing process is provided by way of example; in other embodiments, any other suitable process can be used to manufacture the window assembly 33. In some embodiments, the window assembly 33 has a circular shape, such that the opening 36 is the inner diameter of the window assembly 33 and the outer diameter 67 of the window assembly 33 is about 4 mm to 6 mm (typically about 5 mm).

[0044] In some embodiments, stage 40 is configured to position outer surface 13 of sample 30 at a distance 66 (also referred to herein as an air gap) from outer surface 29 of window layer 55. In this example, distance 66 has a length along the Z axis of approximately 100 μm to 500 μm, or other suitable distance less than approximately 1 mm. Note that in this configuration, (i) the first portion of the paths of beams 23 and 25 and 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 excitation of beam 25 from surface 13 occur within the narrow air gap (approximately 100 μm and 500 μm) between surfaces 13 and 29 of sample 30 and window 55, respectively.

[0045] In some embodiments, the high stiffness of silicon nitride, graphene, and SiC (determined by Young's modulus as described above) combined with the small size of opening 36 (e.g., less than about 3 mm) can make surface 29 of window layer 55 substantially parallel to surface 13 of sample 30 in the XY plane of the XYZ coordinate system. Furthermore, increasing thickness 77 of window layer 55 by a few nanometers or tens of nanometers can increase the flatness of surface 29 in the XY plane.

[0046] 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 gauge or a confocal white light sensor with a reading time frequency per measurement site of less than about 1 second and a displacement resolution and accuracy of less than about 1 μm.

[0047] In some embodiments, processor 22 is configured to generally control the movement of stage 40 in the XY plane (generally parallel to surface 13 of sample 30) and maintain the air gap (distance 66) of 100 μm to 500 μm described above while performing XRF measurements and analyses. In some embodiments, distance sensor 18, also referred to herein as a proximity sensor, is configured to output a signal indicative of 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 variations in the ambient 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), to reduce attenuation of the energy of beam 25 compared to the attenuation of the energy of beam 25 when air or other gases are present in air gap (distance 66).

[0048] In some embodiments, the window assembly 33 is 6 The graphene layer(s) of window layer 55 have electrical conductivity on the order of Siemens per meter (S / m), and are formed from conductive materials such as silicon in layer 44 and SiC, whose conductivity is determined by the type and concentration of dopants embedded in the silicon and SiC matrix. For example, using a high concentration of boron dopant can result in a conductivity of, for example, about 8.3×10 4A sufficiently high conductivity of the silicon layer, such as .S / m, can be obtained. In some embodiments, this configuration reduces (and preferably prevents) electrons (and charged particles) emitted from the surface 13 of the sample 30 from adhering to the outer surface 29 of the window layer 55 and / or from penetrating the detector(s) 16 and thereby interfering with the detection accuracy of the beam 25. Additionally or alternatively, the system 11 includes a magnetic-based charge trap (MT) 88 integrated within the vacuum chamber 15, such as between (i) the surface 31 of the window layer 55 and (ii) the detector(s) 16. In this implementation, the MT 88 includes a conductive coil (e.g., made of copper) positioned in a plane parallel to the surface 39 of one or more of the detectors 16 to trap electrons and / or charged particles directed toward the detector(s) 16.

[0049] In some embodiments, processor 22 is configured to control stage 40 to remove sample 30 after the X-ray fluorescence measurement is completed and to load the next sample 30 to be subjected to X-ray fluorescence measurement by system 11. Placing sample 30 in an atmospheric environment (i.e., outside vacuum chamber 15) eliminates the need to load, lock, and evacuate vacuum chamber 15 for each new sample 30.

[0050] In some embodiments, the configuration of system 11 can be used as part of a multi-channel system including, for example, 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 the measurement of different materials within sample 30. In such embodiments, system 11 can be used as an XRF measurement channel in combination with systems implementing other measurement techniques, including, but not limited to, X-ray methods such as high-resolution X-ray diffraction (HR XRD), X-ray reflection (XRR), X-ray photoelectron spectroscopy (XPS), and small-angle X-ray spectroscopy (SAXS), as well as optical measurements such as reflectometry, optical scatterometry, and Raman spectroscopy.

[0051] In some embodiments, the disclosed method and system 11 configuration allows for 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 their K-shell X-ray emission lines, by guiding the XRF emitted from sample 30 through a vacuum. Furthermore, the disclosed method and system 11 configuration also allows for X-ray fluorescence analysis of some materials with atomic weights greater than about 30 (e.g., germanium (Ge), silver (Ag), and tin (Sn)) by analyzing low-energy emission lines, such as L-shell X-rays. In such embodiments, the layers of the aforementioned materials typically have thicknesses between about 5 Angstroms and 1 μm.

[0052] This particular configuration of system 11 is provided as an example to illustrate some of the problems addressed by embodiments of the present invention and to demonstrate the application of these embodiments in improving the performance of such X-ray fluorescence analysis systems. However, embodiments of the present invention are in no way limited to this particular type of example system, and the principles described herein may be applied to other types of X-ray analysis systems known in the art as well.

[0053] FIG. 2 is a flow chart that outlines a method for manufacturing system 11 according to an embodiment of the present invention.

[0054] The method begins with a window assembly fabrication step 100, which fabricates a window assembly 33 having an opening 36 and a window layer 55 having a thickness of approximately 0.4 μm to 0.7 μm, as detailed in FIG. 1 above.

[0055] In an X-ray analysis assembly placement step 102, the X-ray analysis assembly 10 (including the X-ray source 12, the X-ray optics 14, and the detector 16) is placed within an X-ray enclosure, also referred to herein as a chamber 15, as described in detail in FIG. 1 above.

[0056] In a sealing step 104, the chamber 15 is sealed by coupling a window assembly 33 to an opening in the chamber 15 having the same size as the opening 36 described above, as detailed in FIG. 1 above.

[0057] In a sensor coupling step 106, a distance sensor 18 is coupled to the chamber 15. In some embodiments, the distance sensor 18 is configured to measure the distance 66 between the surface 13 of the sample 30 and the surface 29 of the window layer 55, as described in detail in FIG. 1 above.

[0058] Completing the method, in a connecting step 108, the processor 22 is connected to (i) the stage 40 and the 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) the X-ray source 12 and the detector 16 of the X-ray analysis assembly 10, so as to direct the X-ray beam 23 toward the sample 30 and receive from the detector(s) a signal indicative of the fluorescent X-ray beam 25 emitted from the sample 30 in response to the beam 23 impinging on the surface 13, as described in detail in FIG. 1 above.

[0059] Accordingly, it will be understood that the above-described embodiments are presented by way of example, and that the present invention is not limited to what has been specifically shown and described herein. Rather, the scope of the present invention includes combinations and subcombinations of the various features described herein, as well as variations and modifications thereof not disclosed in the prior art that would occur to one skilled in the art upon reading the above description. Documents incorporated by reference into this patent application are to be considered integral parts of this application, except that to the extent that any term in these incorporated documents is defined in a manner that contradicts a definition expressly or implicitly given herein, only the definition in this specification shall be considered.

Claims

1. 1. A system for X-ray analysis, comprising: an x-ray analysis assembly (i) disposed within an x-ray enclosure configured to maintain a controlled first pressure; and (ii) configured to direct a first x-ray beam toward a sample disposed outside the x-ray enclosure at a second pressure different from the first pressure, and to generate a signal indicative of a second x-ray beam emitted from the sample in response to the first x-ray beam impinging on the sample; a window assembly disposed between the X-ray analysis assembly and the sample, the window assembly configured to (i) seal the X-ray enclosure to maintain a pressure differential between the first pressure and the second pressure, and (ii) transmit the first and second X-ray beams, the window assembly including a window layer formed from a material transparent to the first and second X-ray beams; A system comprising:

2. the window layer comprises a silicon nitride compound; The system of claim 1 .

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

4. the X-ray analysis assembly includes one or more detectors configured to generate the signal in response to detecting the second X-ray beam, and the window layer is electrically conductive and configured to prevent electrons and charged particles emitted from the sample from at least one of (i) adhering to a window surface of the window layer facing the sample and (ii) penetrating into the one or more detectors. The system of claim 1 .

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

6. the sample is disposed on a stage configured to move the sample along at least an axis, the system comprising a processor configured to control the stage to move the sample along the axis relative to the X-ray enclosure 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. A system according to any one of claims 1 to 5.

7. the second pressure comprises atmospheric pressure, and the processor is configured to control a flow of helium gas or nitrogen gas between the first and second surfaces. The system of claim 6.

8. the window assembly includes the window layer formed from the material, the window layer formed on an additional layer, the additional layer (i) having a reduced transparency to the first and second X-ray beams compared to the window layer, and (ii) having openings for the passage of the first and second X-ray beams; A system according to any one of claims 1 to 5.

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

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

11. 1. A method for manufacturing an X-ray analysis system, comprising: disposing an x-ray analysis assembly within an x-ray enclosure configured to maintain a controlled first pressure, the x-ray analysis assembly configured to direct a first x-ray beam toward a sample disposed outside the x-ray enclosure at a second pressure different from the first pressure, and to generate a signal indicative of a second x-ray beam emitted from the sample in response to the first x-ray beam impinging on the sample; (i) sealing the x-ray enclosure to maintain a pressure differential between the first pressure and the second pressure; and (ii) coupling to the x-ray enclosure a window assembly configured to transmit the first and second x-ray beams, the window assembly including a window layer formed from a material transparent to the first and second x-ray beams; A method comprising:

12. bonding the window assembly includes bonding the window layer formed from a silicon nitride compound. The method of claim 11.

13. bonding the window assembly includes bonding the window layer formed from a film of graphene or silicon carbide (SiC). The method of claim 11.

14. wherein positioning the X-ray analysis assembly includes positioning one or more detectors configured to generate a signal in response to detecting the second X-ray beam, and wherein coupling the window assembly includes coupling the window layer to be conductive and configured to prevent electrons and charged particles emitted from the sample from at least one of (i) adhering to a window surface of the window layer facing the sample and (ii) penetrating into the one or more detectors. The method of claim 11.

15. disposing the X-ray analysis assembly includes disposing one or more detectors configured to generate the signal in response to detecting the second X-ray beam; and integrating a charge trap within the X-ray enclosure configured to prevent electrons and charged particles from entering the one or more detectors. The method of claim 11.

16. placing the sample on a stage configured to move the sample along at least an axis; and connecting the stage to a processor configured to control the stage to move the sample along the axis relative to the x-ray enclosure 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.

16. The method according to any one of claims 11 to 15.

17. the second pressure comprises atmospheric pressure, and the method comprises connecting the processor to helium gas or nitrogen gas and controlling a flow of helium gas or nitrogen gas, respectively, between the first and second surfaces.

17. The method of claim 16.

18. forming the window assembly by forming the window layer on an additional layer that is less transmissive to the first and second X-ray beams than the window layer and forming openings in the additional layer for passing the first and second X-ray beams.

16. The method according to any one of claims 11 to 15.

19. forming the opening includes forming the opening smaller than 5 mm, and forming the window layer includes depositing the window layer having a thickness of less than 0.5 μm.

20. The method of claim 18.

20. The positioning of the X-ray analysis assembly includes (i) an anode metal film configured to emit a first X-ray beam having a predetermined energy, the first X-ray beam having a predetermined energy of (a) 8.3×10 4 (b) an anode having an anode metal film formed on a base layer 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 at the anode to generate the first X-ray beam, wherein the second pressure comprises atmospheric pressure, and the second X-ray beam comprises X-ray fluorescence (XRF) emitted from the sample at a depth of less than 1000 nm.

16. The method according to any one of claims 11 to 15.

Images