System and method for X-ray fluorescence detection of light elements

Abstract

This invention provides an X-ray fluorescence (XRF) inspection system and method for improving the detection of light elements in a sample. [Solution] The method comprises at least one X-ray source configured to emit radiation within a selected energy range, an optical device having one or more reflective surfaces for filtering a specific energy band and focusing it at the inspection position, and a sample stage for holding the sample. It is also configured to maintain at least one of a vacuum environment or a helium-rich environment along the X-ray path to reduce the absorption of low-energy X-rays. In some embodiments, the detector device includes a segmented detector formed from two or more detection units arranged around the path of focused radiation, positioned close to the inspection position. The method includes generating, filtering, and focusing X-rays, providing a controlled environment, and detecting fluorescence emission for the analysis of light elements.

Description

Technical Field

[0001] The present disclosure relates to a system and corresponding method for use in XRF inspection, and particularly to inspection of a sample containing light elements.

Background Art

[0002] X-ray fluorescence (XRF) inspection is a widely used analytical technique for determining the composition of a material by measuring characteristic secondary (or fluorescent) X-rays emitted from a sample when exposed to primary X-rays. Conventional XRF systems typically operate in an ambient air environment and focus on detecting medium to heavy atomic mass elements due to limitations in detecting lower energy fluorescent signals. Low-energy X-ray fluorescence signals, particularly those corresponding to elements with an atomic number less than 14, tend to be strongly absorbed by air molecules, making accurate detection of these elements difficult in conventional systems.

[0003] Various techniques have been developed directed to the detection of light elements and / or X-ray inspection using low-energy X-rays. For example, certain portable X-ray fluorescence (XRF) technologies have been developed that improve the detection limits for light elements such as magnesium and sodium. However, detection of these elements is still difficult due to low-energy fluorescence absorption by air and sample reabsorption, requiring higher element concentrations for reliable analysis. To address this, researchers have introduced a helium environment into portable XRF systems such as the Bruker TRACER 5g to reduce air absorption and improve sodium detection. While these improvements assist with field applications, benchtop systems such as the Bruker M4 TORNADO μ-XRF use vacuum conditions to eliminate air interference, enabling detection of even lighter elements such as carbon. These advances continue to improve XRF technology for more precise light element analysis.

Summary of Invention

[0004] To enable the detection of light elements and improve detection sensitivity, this disclosure provides optimized system configurations and operating methods. For this purpose, the systems of this disclosure utilize a vacuum chamber or a helium-rich environment to significantly reduce low-energy X-ray absorption and improve signal clarity and measurement accuracy. In addition, in some embodiments, the techniques of this disclosure may utilize advanced optical devices that incorporate monochromators and other filtering mechanisms to enable precise selection of the X-ray energy band and focus specific wavelengths onto the sample for the desired analysis. These enhancements improve the signal-to-noise ratio and overall system performance.

[0005] Furthermore, in some embodiments, the inspection system may utilize a detector device positioned close to the inspection location. This position of the detector device allows for reduced absorption of X-rays by air when present in the system, and also enables the collection of fluorescent X-rays at an increased solid angle. The detector device may include a selected number of detector units (e.g., silicon drift detectors (SDDs)) arranged around the path of radiation directed towards the inspection area. For example, the detector device may be positioned at a distance of 2 centimeters or less than 1 centimeter from the inspection location.

[0006] Therefore, according to a broader aspect, this disclosure provides an X-ray fluorescence inspection system, said X-ray fluorescence inspection system, At least one X-ray source configured to emit X-rays within a selected energy range, An optical device comprising one or more reflective surfaces and configured to filter a specific energy band from emitted X-rays and focus radiation of that specific energy band onto the inspection position, A sample stage configured to hold a sample for inspection, The specific energy band includes energies from 0.2 keV to 2 keV, and the system is configured to maintain at least one of either a vacuum environment or a helium-rich environment within at least a portion of the system related to the X-ray path.

[0007] According to some embodiments, the system A sealed enclosure, The system may further include at least one vacuum pump configured to maintain the sealed enclosure at an operating pressure of 20 mbar or less.

[0008] According to some embodiments, the vacuum pump is further configured to maintain the sealed housing at an operating pressure of 2 mbar or less.

[0009] According to some embodiments, the system may further include a helium source configured to provide a controlled flow of helium gas within the system.

[0010] According to some embodiments, the helium source includes an output nozzle located at a selected position within the system.

[0011] According to some embodiments, the system may further include a helium source equipped with an output nozzle and configured to provide a controlled flow of helium gas within the system at a selected location within the system.

[0012] According to some embodiments, the optical device comprises at least one multilayer monochromator configured to filter a specific energy band.

[0013] According to some embodiments, the optical device further comprises an adjustable aperture that allows control over the size of the illumination spot at the inspection position.

[0014] According to some embodiments, the system may further include a detector device configured to detect fluorescent radiation emitted from the inspection site.

[0015] According to some embodiments, the detector device comprises a selected number of detectors arranged around an X-ray source.

[0016] According to some embodiments, the detector device comprises a segmented detector formed from two or more detection units arranged around a transmission path of radiation focused to the inspection position, the segmented detector being positioned at a distance of 1 centimeter or less from the inspection position.

[0017] According to some embodiments, the segmented detector comprises one or more detectors having a selected angle between the detection surface and the connection to each detection circuit, wherein the selected angle is 10° to 80°. According to some embodiments, the selected angle may be 45° ± 15°.

[0018] According to some embodiments, the sample stage includes a sample translation stage configured to move the sample relative to a focused X-ray beam.

[0019] According to some embodiments, the system may be configured to inspect and detect the presence and density of light elements in a sample, wherein the light elements include elements having an atomic number of 14 or less.

[0020] In another broad aspect, the present disclosure provides a method for X-ray fluorescence inspection, the method is Using at least one X-ray source, generate X-rays within a selected energy range, Filtering a specific energy band from emitted X-rays using an optical device with one or more reflective surfaces, The sample is placed on the sample stage at the testing location, Focusing filtered radiation on the inspection site, The method includes providing at least one of a vacuum environment or a helium-rich environment in at least a portion of the X-ray path, and performing an X-ray fluorescence inspection, wherein the selected energy band includes energies from 0.2 keV to 2 keV.

[0021] According to some embodiments, the method may further comprise maintaining the inspection environment at a pressure of 20 mbar or less using a sealed housing and at least one vacuum pump.

[0022] According to some embodiments, the inspection environment is at a pressure of 2 mbar or less.

[0023] According to some embodiments, the method may further comprise providing a controlled flow of helium gas into the system using a helium source.

[0024] According to some embodiments, the method may further comprise providing an output nozzle that discharges a helium flow at one or more selected positions within the X-ray path.

[0025] In some embodiments, the method may further comprise providing a controlled flow of helium gas through an output nozzle that discharges the helium flow to one or more selected positions in the system within the X-ray path using a helium source.

[0026] According to some embodiments, the method may further comprise detecting fluorescence emission from the sample using a detector assembly.

[0027] According to some embodiments, detecting fluorescence emission from the sample using a detector assembly may comprise using an assembly of two or more detectors arranged around at least one X-ray source.

[0028] According to some embodiments, detecting fluorescence emission from the sample using a detector assembly may comprise using a split detector formed from two or more detection units arranged around a transmission path of radiation focused to an inspection position, wherein the split detector is arranged at a distance of 1 centimeter or less from the inspection position.

[0029] According to some embodiments, the method may be configured to examine and detect the presence and density of light elements in a sample, wherein the light elements include elements having an atomic number of 14 or less.

[0030] In yet another broader aspect, the present disclosure provides an X-ray fluorescence inspection system, said X-ray fluorescence inspection system, At least one X-ray source configured to emit X-rays within a selected energy range, An optical device comprising one or more reflective surfaces and configured to filter a specific energy band from emitted X-rays and focus radiation of that specific energy band onto the inspection position, A sample stage configured to hold a sample for testing, A detector device is provided, The detector device comprises a segmented detector formed from two or more detection units arranged around a radiation transmission path focused to the inspection position, with the segmented detector positioned at a distance of 1 centimeter or less from the inspection position.

[0031] According to some embodiments, the segmented detector comprises one or more detectors having a selected angle between the detection surface and the connection to each detection circuit, wherein the selected angle is 10° to 80°. According to some embodiments, the selected angle may be 45° ± 15°.

[0032] In general, various embodiments of this disclosure may utilize any elements or features described herein, including elements or features described in relation to other embodiments of this disclosure. [Brief explanation of the drawing]

[0033] To better understand the subject matter disclosed herein and to illustrate how it can actually be carried out, embodiments are described below, as non-limiting examples, with reference to the accompanying drawings.

[0034] [Figure 1]This shows the absorption of X-rays emitted from light elements in environments with different pressures and gas compositions. [Figure 2] This disclosure illustrates XRF inspection systems according to several embodiments. [Figure 3A] To illustrate spectral filtering by reflection, Figure 3A shows reflection from a thin film, and Figure 3B shows reflection from a multilayer monochromator. [Figure 3B] To illustrate spectral filtering by reflection, Figure 3A shows reflection from a thin film, and Figure 3B shows reflection from a multilayer monochromator. [Figure 4A] Figure 4A illustrates a reflective surface array used to focus a beam, showing two consecutive ellipsoidal reflective surfaces, Figure 4B illustrates two perpendicular ellipsoidal surfaces, and Figure 4C illustrates focusing to a selected focal point. [Figure 4B] Figure 4A illustrates a reflective surface array used to focus a beam, showing two consecutive ellipsoidal reflective surfaces, Figure 4B illustrates two perpendicular ellipsoidal surfaces, and Figure 4C illustrates focusing to a selected focal point. [Figure 4C] Figure 4A illustrates a reflective surface array used to focus a beam, showing two consecutive ellipsoidal reflective surfaces, Figure 4B illustrates two perpendicular ellipsoidal surfaces, and Figure 4C illustrates focusing to a selected focal point. [Figure 5A] An optical device utilizing a reflecting mirror is schematically illustrated, with Figure 5A illustrating the structure of the optical device and Figure 5B illustrating the orientation of a mirror with a beam stopper. [Figure 5B] An optical device utilizing a reflecting mirror is schematically illustrated, with Figure 5A illustrating the structure of the optical device and Figure 5B illustrating the orientation of a mirror with a beam stopper. [Figure 6] This disclosure illustrates an XRF inspection system that utilizes segmented detectors located very close to the inspection site, according to several embodiments of this disclosure. [Figure 7A] Two arrays of detection regions in a segmented detector are illustrated according to several embodiments of this disclosure. [Figure 7B]Two arrays of detection regions in a segmented detector are illustrated according to several embodiments of this disclosure. [Figure 8] Schematic diagrams of segmented detector systems according to several embodiments of this disclosure are illustrated below. [Modes for carrying out the invention]

[0035] As described above, this disclosure provides a system and corresponding method that enables XRF testing of samples, and in particular targets the testing of samples containing light elements (LEs). Generally, XRF testing of light elements is limited due to the absorption of low-energy X-rays by the ambient air surrounding the testing area. Figure 1, originally reported in "Detecting light elements with portable XRF" (Portaspecs.com), illustrates the effect of atmospheric conditions and composition on the detection of LEs with atomic numbers (z) of 13 (aluminum) or less. Figure 1 shows four curves G1-G4 for normal atmospheric conditions (G1), reduced pressure to 20 mbar (G2), reduced pressure to 2 mbar (G3), and a helium environment (G4). As shown, X-rays with energies below 1.2 keV are almost completely absorbed by the atmospheric air environment, hindering the detection of LEs lighter than aluminum (Al). Operating under vacuum conditions at a pressure of 20 mbar allows for the transmission of low-energy X-rays while exhibiting high absorption around 0.4 keV, associated with nitrogen (N2). Further enhancing the vacuum conditions at a pressure of 2 mbar reduces absorption and increases detection sensitivity. In addition, operation in a helium-rich environment (G4) exhibits comparable transmittance to operation at 2 mbar (G3) for energies above 0.7 keV, while avoiding the absorption peak associated with the presence of atmospheric nitrogen.

[0036] Various semiconductor devices often contain light elements such as aluminum (Al), carbon (C), nitrogen (N), and boron (B). These elements may be used during certain stages of the semiconductor wafer lifecycle and / or for selected doping within the sample. Furthermore, monitoring of oxygen (O) may be important because O is present in the insulating SiO2 layer, and the presence of O can affect electrical conductivity through various regions of the semiconductor structure / circuit.

[0037] For this purpose, the disclosure provides an X-ray fluorescence inspection system configured to scan a sample and determine fluorescence radiation having an energy range of 0.1KeV to 2KeV in at least one of a vacuum environment and a helium-rich environment. Refer to Figure 2, which schematically illustrates the inspection system 100. The system 100 includes at least one X-ray source 110 configured to emit X-rays in a selected energy range, typically including one or more emission lines in the range of 0.2KeV to 2KeV; an optical device 120 configured to filter a specific energy band from the emitted X-rays and focus the emitted radiation ER in the specific energy band to the inspection position 50; and a sample stage 140 configured to hold the sample 60 for inspection.

[0038] The inspection system also typically includes a detection device 130 which includes one or more (typically four) detectors, exemplified by detectors 130a and 130b. The detectors are configured to detect secondary X-rays or fluorescence radiation FR emitted from the sample 60 in response to X-ray ER impacting the sample 60.

[0039] To provide desired conditions that enable inspection within the energy range of 0.2KeV to 2KeV, the inspection system 100 is configured to operate by providing at least one of a vacuum environment or a helium-rich environment for fluorescence radiation. Generally, a selected vacuum under helium-rich conditions may be used in a selected region between the sample 60 and the detector device 130. For this purpose, the system includes an operable environmental condition module 150 configured to provide desired operating conditions selected to reduce X-ray absorption by the inspection environment, thereby enhancing the detection of LE in the sample 60.

[0040] Generally, the X-ray source 110 may be any X-ray source that is a tungsten (W) anode X-ray tube, or any other X-ray source that can emit X-rays including an energy range of 0.2 keV to 2 keV. The X-ray source 110 and / or optical device 120 may provide filtering of the emitted X-rays to provide radiation ER within a selected energy range directed to the inspection position 50 on the sample 60.

[0041] Tungsten (W) anode X-ray tubes generally possess characteristic radiation containing K-rays and L-rays associated with relatively high energies. Such X-ray tubes also offer emission characteristics of Ma-rays with an energy of 1.776 KeV. Due to its relatively low energy, this energy ray is typically suitable for the detection and measurement of light elements. Furthermore, this energy ray is generally close to the energy levels of various light element materials and therefore can optimally excite them.

[0042] For example, in the measurement of aluminum, the use of W-Ma energy lines can offer a special advantage: the energy of 1.557 KeV is relatively close to, and slightly above, the K-edge energy level of aluminum. The proximity between the excitation energy and the excitation energy level allows for efficient excitation of aluminum in the sample 60. Furthermore, the energy of 1.776 KeV is slightly lower than the K-edge energy level of silicon, which is 1.839 KeV. Therefore, using X-rays of this energy generally does not excite silicon, or results in very low excitation of silicon. This makes it possible to detect other elements on top of the silicon background that is typically abundant in semiconductor wafers / circuits.

[0043] While the use of tungsten anode X-ray tubes may offer various advantages for detecting LE in semiconductor samples, it should be noted that the techniques of this disclosure are not limited to this particular X-ray source and can be used with any X-ray source having one or more emission lines or continuous radiation in the range of 0.2KeV to 2KeV. Such X-ray sources include, for example, microfocus X-ray tubes, transmission X-ray tubes operating on thin targets (often beryllium or other light materials), windowless (vacuum) X-ray tubes, molybdenum anode X-ray tubes, chromium, copper, or silver anode X-ray tubes, electron impact X-ray sources, and / or plasma-based soft X-ray sources. Certain sources require filtering of emitted X-rays, but the emitted spectrum includes the desired energy range.

[0044] In some embodiments of this disclosure, the inspection system 100 may include or be housed within a sealed enclosure 160. The sealed enclosure 160 may be configured to withstand vacuum conditions of 2 mbar or less. The environmental conditions module 150 may be one or more vacuum pumps that can operate to evacuate air from the sealed enclosure 160 and enable the maintenance of working conditions associated with pressures of 2 mbar or less. As described above, under such reduced pressure, atmospheric absorption of low-energy X-rays is sufficiently low to enable the detection of LE-related fluorescence emission from the sample 60. Thus, the sample 60 may be inserted into the inspection system 100 and placed on the sample stage 140. Following the insertion of the sample 60, the sealed enclosure 160 is closed and sealed, and the vacuum pumps of the environmental conditions module 150 are activated to evacuate air from the sealed enclosure 160. To provide monitoring of the conditions inside the enclosure, the system 100 may also include a pressure gauge (not shown), and when the conditions reach a desired pressure of 2 mbar or less, the inspection can be operated for inspection of the sample.

[0045] In some other embodiments, the environmental conditions module 150 may be a helium source configured and operable to provide a helium flow toward the inspection area and / or the X-ray source 110. Thus, the helium source may include a helium tank and corresponding piping / channels operable to provide a predetermined helium flow toward the inspection area. The helium flow is selected to be sufficient to substantially replace the atmosphere between the X-ray source 110, the sample 60, and the detector device 130 with helium, thereby eliminating or at least significantly reducing the absorption of low-energy X-rays by the atmosphere.

[0046] To maintain the desired helium-rich conditions, the system 100 may include a housing 160 that does not need to be completely sealed in this embodiment. The housing 160 generally has at least one opening to allow air to exit the housing and give room for helium gas to occupy its place. Furthermore, to ensure a helium-rich environment around the inspection area, any piping or channels providing helium flow into the helium source 150 and the system 100 may include output nozzles located at selected positions near the inspection area 50. For example, the output nozzles may be located at a selected distance from the inspection position 50. One or more additional output nozzles may be located and used at different positions within the system.

[0047] As described above, the inspection system includes an optical device 120. The optical device 120 provides focus for the emitted X-ray ER into the inspection area 50. Furthermore, as shown, in some embodiments, the optical device may provide selective filtering of X-rays to filter out X-ray components having energies beyond a desired range, for example, above 2 keV. Furthermore, in some embodiments, the optical device 120 may be configured to filter the X-rays to provide radiation in a selected energy range within the range of 0.2 keV to 2 keV, enabling the precise detection of one or more specific elements in the sample 60. In this regard, see Figures 3A and 3B illustrating the use of reflective surfaces for filtering radiation based on energy (or wavelength). Figure 3A illustrates a thin-film filter, and Figure 3B illustrates a multilayer reflective filter structure.

[0048] As shown in Figure 3A, the input radiation IL strikes the thin film at an angle θ1. Part of the radiation is reflected from the interface, while another portion propagates within the thin film and is reflected at an angle θ2 from the opposite surface of the film. As a result, the reflected radiation consists of a first portion reflected from the first interface and a second portion reflected from the second interface, with the two radiation portions having a phase shift between them related to the film thickness and its refractive index n2. High reflectivity is achieved when the environmental refractive index n1=1, i.e., under the assumption that the environment is air, the condition n2λ=2dsin(θ1) is met. For other environments, the calculation is slightly modified using n1. Thus, with respect to a selected reflection angle θ, the thin film provides high reflectivity at wavelengths under the condition λ=2dsin(θ1) / n2, while reflection is reduced for other wavelengths. In this case, n2 is the refractive index of the layer, d is the thickness of the layer, and λ is the wavelength of the radiation.

[0049] As illustrated in Figure 3B, improved filtering can be achieved using a multilayer configuration. Figure 3B illustrates a multilayer monochromator configured to filter selected energies and reflect radiation of specific selected energies. The multilayer monochromator is formed from multiple thin layers having selected refractive indices and thicknesses such that portions of reflected radiation reflected from different interfaces of the multilayer structure interfere constructively with respect to selected wavelengths and destructively with respect to other wavelengths. This configuration results in improved filtering with respect to thin-film monochromators under similar wavelength conditions. To provide filtering of radiation and to provide a desired energy of radiation impacting the inspection position 50, the disclosure may use a thin-film or multilayer filtering device at a selected angle and utilize one or more reflective surfaces configured to have selected material and thickness characteristics to filter out undesirable energies and reflect radiation components of selected energies toward the sample.

[0050] The use of reflective surfaces, including thin-film and / or multilayer filtering devices, may further enable focusing the emitted X-rays to the inspection position 50 on the sample. Figures 4A–4C illustrate three reflective optics configured to focus radiation ER emitted from the radiation source 110 and reflected (and optionally filtered) using reflective surfaces 122 and 124. The reflective surfaces are configured with selected curvatures and are arranged to reflect the radiating portion and provide focus of radiation ER to the inspection position 50.

[0051] Reflective surfaces 122 and 124 are x 2 / a 2 +y 2 / b 2 It may consist of elliptic curvature along a portion of the ellipse defined by = 1, where a and b define the semi-major and semi-minor axes of the ellipse. Typically, reflectors 122 and 124 correspond to only a small portion of the ellipse, maintaining an open area for input and output radiation.

[0052] Referring to Figures 5A and 5B, which illustrate further configurations of the optical device 122 according to some embodiments of the present disclosure, following the examples in Figures 4A to 4C, Figure 5A illustrates a cross-sectional view of the optical device and the radiation path through it, and Figure 5B illustrates a view of the optical device along its optical axis. The optical device 120 may consist of an array of reflective surfaces 122a, 122b, 124a, and 124b arranged in a square array, providing a path for radiation to pass through openings between the reflective surfaces. Generally, various configurations can be used for the optical device 120, and in the use of X-rays, the use of reflective and / or diffractive optical systems is typically required. According to the present disclosure, one or more of the reflective surfaces are coated with a multilayer monochromator coating, as illustrated in Figure 3B, to provide efficient reflection of radiation in a selected energy range and to filter out undesirable energy bands, e.g., radiation in the energy band above 2 keV. The optical device 120 may further include one or more apertures, such as a spot size aperture 125, an input aperture 126, and a mechanical collimator 127, and may also include a central radiation blocking element 128 configured to prevent radiation from propagating in a path that does not include reflections from the reflective surfaces 122 and 124. In some embodiments, the optical device may also include an anti-ghosting surface 129 located at the output of the optical device 120 and configured to prevent the formation of ghost images due to scattering of radiation components. The apertures 125, 126, and 127 may be adjustable to allow control of the size of the illumination spot, the intensity of radiation impacting the sample, and / or the level of radiation collimation. The optical device 120 thus provides focusing of radiation emitted from the X-ray source 110 and filtering of radiation to provide illumination having a selected energy range. Furthermore, the optical device 120 may consist of one or more adjustable apertures that allow control of the illumination spot size, enabling a choice between high-speed inspection and high-resolution inspection.

[0053] As described above, this disclosure relates to X-ray fluorescence inspection of a sample, for the detection and measurement of light elements in the sample. To enable the detection and measurement of LE in the sample, the technique utilizes a vacuum and / or helium-rich environment during inspection to reduce the absorption of relatively low-energy X-rays by the air surrounding the inspection area. Additional configurations that enable the reduction of X-ray absorption by air relate to reducing the path of X-rays through the air. This approach can be carried out independently or in addition to the use of a vacuum and / or helium-rich inspection environment. For this purpose, this disclosure further provides an inspection system 100 that utilizes a segmented detector device configured to detect X-rays emitted from an inspection position on the sample. The detector device may include a segmented detector formed from two or more detectors and configured to be positioned at a selected reduced distance from the inspection position.

[0054] In this regard, refer to Figure 6 illustrating an X-ray fluorescence inspection system 100 according to several embodiments of the present disclosure. The system 100 is generally configured according to the system 100 illustrated in Figure 2 above, but includes a segmented detector 1300. The segmented detector 1300 is formed from two or more detectors 1300a and 1300b, as illustrated in Figure 6. The two or more detectors are arranged around the path of an X-ray ER directed to strike the inspection position 50 and are configured to detect the fluorescence radiation emitted from the inspection position.

[0055] Generally, detectors 1300a and 1300b (and additional detectors, if used) may be silicon drift detectors (SDDs) or SDD-type detectors, or other detectors compatible with standard SDD detectors. Figures 7A and 7B illustrate two configurations of the detector device 1300 according to some embodiments of the present disclosure. Figure 7A illustrates a radial arrangement of sensor units 1300a to 1300d around a central aperture 1320, and Figure 7B illustrates an arrangement utilizing sensor units 1300a to 1300d configured to provide a circular sensor arrangement around the central aperture 1320. As shown in Figures 7A and 7B, the detector device may be configured as a ring-shaped structure 1340 divided into four independent segments 1300a to 1300d. Note that the number of segments may be any selected number, which may be two detector segments, three detector segments, four detector segments, five detector segments, or any other appropriate number of detector segments.

[0056] Each detector segment may contain one or more detection elements and may be able to operate independently for X-ray detection without relying on other segments. Furthermore, the detector device 1300 may generally include a central opening 1320 or hole that allows the passage of X-rays emitted from the X-ray source 110 and propagating toward the inspection position 50 on the sample 60.

[0057] The detector apparatus 1300 described herein may have a planar ring shape or other configurations including several detector segments arranged around a path of X-rays directed to the inspection position 50, and may be configured to allow close proximity to the sample. More specifically, the detector apparatus may be configured to be positioned at a selected distance of 0.01 to 2 centimeters from the sample, or at a distance of 2 centimeters or less, or at a distance of 1 centimeter or less. Thus, the detector apparatus 1300 is configured to offer several advantages over conventional configurations of detectors arranged around an X-ray source. Such advantages may include reduced absorption of X-rays by air and an increased solid angle for the collection of fluorescent radiation. These advantages, combined, may improve the detection of fluorescent radiation and increase the signal-to-noise ratio.

[0058] To further minimize the distance between the detector and the inspection position, the systems and techniques of this disclosure may utilize an angled detector unit. Figure 8 illustrates an angled detector unit 1310, which includes a detection region 1300i, a collection circuit 1360, and a mechanism 1380 connecting the circuit 1360 to the detection region 1300i. The angled detector unit 1310 is configured with a selected angle Φ between the mechanism 1380 and the surface of the detection region 1300i. The selected angle Φ may be selected in the range of 10° to 80°. In some embodiments, the selected angle Φ may be selected to be 45° ± 15°. Providing a non-zero distance between the surface of the detector and the connector to the corresponding circuit 1360 allows for improved packaging and enables the detection region 1300i to be positioned closer to the inspection position. More specifically, the detection region 1300i may be positioned at a distance of 2 centimeters or less, or 1 centimeter or less, from the inspection position. Furthermore, the selected angle Φ can reduce spatial interference of elements within the system.

[0059] Accordingly, this disclosure provides a system and corresponding method for X-ray fluorescence inspection of semiconductor samples, which are intended for measuring light elements in the sample. The system of this disclosure is operable in a vacuum and / or a helium-rich environment and can reduce the absorption of low-energy X-rays by the ambient air. In some embodiments, the system may utilize a segmented detector formed from two or more detection units arranged around a radiation transmission path directed towards the inspection position and positioned close to the inspection position.

[0060] It should be noted that the various features described in the various embodiments can be combined according to all possible technical combinations.

[0061] It should be understood that the present invention is not limited in its application to the details shown in the description contained herein or illustrated in the drawings. Other embodiments of the present invention are possible and can be implemented and carried out in various ways. Therefore, it should be understood that the expressions and terms used herein are for illustrative purposes only and should not be considered limiting. Accordingly, those skilled in the art will understand that the concepts underlying this disclosure can be readily used as a basis for designing other structures, methods, and systems to accomplish some of the objectives of the subject matter of this disclosure.

[0062] Those skilled in the art will readily understand that various modifications and changes can be applied to the embodiments of the invention described herein without departing from the scope of the appended claims and the scope defined herein.

Claims

1. X-ray fluorescence inspection system, At least one X-ray source configured to emit X-rays within a selected energy range, An optical device comprising one or more reflective surfaces, configured to filter a specific energy band from the emitted X-rays and focus the radiation in the specific energy band onto the inspection position, A sample stage configured to hold a sample for inspection, The aforementioned specific energy band includes energies from 0.2 keV to 2 keV, and the X-ray fluorescence inspection system is configured to maintain at least one of a vacuum environment or a helium-rich environment within at least a portion of the X-ray fluorescence inspection system related to the X-ray path.

2. A sealed enclosure, The system according to claim 1, further comprising at least one vacuum pump configured to maintain the sealed enclosure at an operating pressure of 20 mbar or less.

3. The system according to claim 1, further comprising a helium source equipped with an output nozzle and configured to provide a controlled flow of helium gas within the system at a selected location within the system.

4. The system according to claim 1, wherein the optical device comprises at least one multilayer monochromator configured to filter the specific energy band.

5. The system according to claim 1, wherein the optical device further comprises an adjustable aperture that enables control of the size of the illumination spot at the inspection position.

6. The system according to claim 1, further comprising a detector device having a selected number of detectors configured to detect fluorescent radiation emitted from the inspection position.

7. The system according to claim 6, wherein the detector device comprises a segmented detector formed from two or more detection units arranged around a transmission path of the radiation focused to the inspection position, and the segmented detector is positioned at a distance of 1 centimeter or less from the inspection position.

8. The system according to claim 7, wherein the segmented detector comprises one or more detectors having a selected angle between the detection surface and the connection portion to each detection circuit, and the selected angle is between 10° and 80°.

9. The system according to any one of claims 1 to 8, wherein the sample stage comprises a sample translation stage configured to move the sample relative to the focused X-ray beam.

10. A system according to any one of claims 1 to 8, configured to inspect and detect the presence and density of light elements in a sample, wherein the light elements include elements having an atomic number of 14 or less.

11. A method for X-ray fluorescence examination, wherein the method is Using at least one X-ray source, generate X-rays within a selected energy band, Filtering a specific energy band from emitted X-rays using an optical device with one or more reflective surfaces, The sample is placed on the sample stage at the testing location, The filtered radiation is focused at the inspection location, A method comprising providing at least one of a vacuum environment or a helium-rich environment in at least a portion of the X-ray path, and performing the X-ray fluorescence inspection, wherein the selected energy band includes energies from 0.2 keV to 2 keV.

12. The method according to claim 11, further comprising using a sealed enclosure and at least one vacuum pump to maintain the inspection environment at a pressure of 20 mbar or less.

13. The method according to claim 11, further comprising using a helium source to provide a controlled flow of helium gas through an output nozzle that emits a helium flow at one or more selected locations in the system within the X-ray path.

14. The method according to any one of claims 11 to 13, further comprising using a detector assembly, which includes using an assembly of two or more detectors arranged around the at least one X-ray source, and using the detector assembly to detect fluorescence emission from the sample.

15. The method according to claim 14, wherein detecting fluorescence emission from the sample using a detector assembly involves using a segmented detector formed of two or more detection units arranged around a transmission path of the radiation focused to the inspection position, the segmented detector being positioned at a distance of 1 centimeter or less from the inspection position.

16. X-ray fluorescence inspection system, At least one X-ray source configured to emit X-rays within a selected energy range, An optical device comprising one or more reflective surfaces, configured to filter a specific energy band from the emitted X-rays and focus the radiation in the specific energy band onto the inspection position, A sample stage configured to hold a sample for testing, A detector device is provided, The detector system comprises a segmented detector formed from two or more detection units arranged around a transmission path of the radiation focused to the inspection position, wherein the segmented detector is positioned at a distance of 1 centimeter or less from the inspection position.

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