Shielded detector for charged particle microscopy

Abstract

To provide systems, components and methods for detecting characteristic signals.SOLUTION: A detector includes a detector cell. The detector cell can be configured to generate an electrical signal in response to a particle incident on an active layer of the detector cell. The active layer can define an absorption surface. The detector can include a filter. The filter can include a membrane of carbon material. The filter can be disposed relative to the detector cell to shield the absorption surface from a subset of the incident particles. The subset of the incident particles can include electrons, ions, and photons. The photons can have energy less than about 40 eV.SELECTED DRAWING: Figure 2A

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Non-provisional Patent Application No. 18 / 456,048, filed August 25, 2023, the disclosure of which is incorporated by reference herein in its entirety.

[0002] SUMMARY OF THE DISCLOSURE

[0002] Embodiments of the present disclosure are directed to charged particle microscope systems, components, and methods for their operation. Some embodiments are directed to components configured for detection of X-rays. [Background technology]

[0003] In charged particle microscopy, characteristic X-rays result from the excitation of inner shell electrons as the beam interacts with atoms in the sample. The X-ray signal is typically used for elemental analysis in a scanning electron microscope (SEM) system. For example, the X-ray signal can be used to generate an energy dispersive X-ray (EDS) spectrum, from which the elemental composition of the sample can be determined.

[0004] Conventional EDS detectors are built around a detector cell, which absorbs incident X-rays of a given energy and produces a proportional charge that is detected. Inner shell excitation and subsequent X-ray emission can occur on various surfaces within the SEM, for example as a result of secondary phenomena other than direct interrogation of the sample. To that end, a typical X-ray EDS detector incorporates a collimator assembly that blocks X-rays originating from outside the area excited by the electron beam. In effect, the collimator reduces the number of stray X-rays from other parts of the microscope chamber that are included in the analysis, but it also significantly limits the stereoscopic collection angle of the EDS detector.

[0005] Conventional detectors are sensitive to various types of incident particles. Ions, electrons, photons in the ultraviolet, visible, and / or infrared spectral ranges, as well as other forms of radiation, can cause noise in the EDS data. Such noise can obscure signals due to low energy X-rays and / or low intensity X-ray lines. To that end, a typical X-ray EDS detector includes a window between the detector and the vacuum chamber. There are two main types of window materials: Beryllium (Be) windows, which strongly absorb low energy X-rays, meaning that only sodium (Na) or heavier elements can be detected, and polymer-based windows, which allow detection of X-rays up to 100 eV but are much less robust and radiation sensitive than Be windows (polymer windows can be degraded by electrons, ions, and photons). Polymer windows are typically supported by grids or other structures for structural reinforcement, but such grids also introduce artifacts into the EDS data.

[0006] In another example, EDS detectors typically include a device to divert electrons away from the detector, which otherwise could cause background noise and overload the detector electronics. The electron diversion device is typically a permanent magnet that strongly deflects passing electrons. Such devices are typically included in detectors that use polymer windows, since thicker beryllium windows absorb electrons with energies below 20 keV. However, permanent magnets interfere with the beam characteristics when in close proximity to the primary beam. For this reason, typical EDS detectors are oriented at a take-off angle of about 35 degrees to about 50 degrees relative to the sample, and at a relatively large distance from the sample compared to polepiece-mounted detectors.

[0007] As a result of the technical constraints described above, EDS detectors are typically limited by their solid angle of collection, relatively low take-off angle, insensitivity to low energy x-ray lines that are difficult to distinguish from background noise, susceptibility to noise generated by extraneous signals, and sensitivity to degradation by energetic species. Thus, there is a need for improved EDS detectors that exhibit improved solid angle of collection for noise sources (e.g., electrons, ions, and photons), improved take-off angle, and improved sensitivity to x-rays. Summary of the Invention

[0008] In a first aspect, the detector includes a detector cell. The detector cell may be configured to generate an electrical signal in response to particles incident on an active layer of the detector cell. The active layer may define an absorbing surface. The detector may include a filter. The filter may include a film of a carbon material. The filter may be disposed relative to the detector cell to shield the absorbing surface from a subset of the incident particles. The subset of incident particles may include electrons, ions, and photons. The photons may have an energy of less than about 40 eV.

[0009] In some embodiments, the carbon material can include carbon nanotubes. The carbon material can include a layer of non-woven carbon nanotube felt. The membrane can include a plurality of substantially planar layers of carbon nanotube felt. The plurality of layers can together define a spatially varying transmittance of the filter. The filter can include a frame in which the layers are disposed. The detector can further include a plurality of frames including the frame. The plurality of frames can be individually addressable and individually moveable relative to the detector cells.

[0010] In some embodiments, the detector defines an aperture substantially parallel to the absorbing surface. The detector cells and the filter may be configured to accommodate the aperture. The detector may include segments disposed about the aperture. The filter may include one or more filter sections arranged to shield one or more of the segments from a subset of the incident particles. The detector may include one or more segments configured to detect x-rays and one or more segments configured to detect charged particles and / or photons. The filter may be configured to shield the segments configured to detect x-rays.

[0011] The detector may further include a shielding, the shielding movable relative to the detector cell and the filter and disposed such that the filter is between the detector and the shielding. The detector may further include a holding element. The holding element may be configured to dispose the detector and filter within a vacuum chamber of the charged particle microscope and to orient the detector relative to a sample stage of the charged particle microscope such that the filter is disposed between the sample stage and the detector. The detector may include a silicon drift detector.

[0012] In a second aspect, a charged particle beam system includes a vacuum chamber. The charged particle beam system can include a charged particle beam column operably coupled to the vacuum chamber and configured to direct a beam of charged particles into the vacuum chamber. The charged particle beam system can include a sample stage disposed within the vacuum chamber. The charged particle beam system can also include a detector of the previous aspect.

[0013] In one embodiment, the carbon material includes carbon nanotubes. The carbon material can include a layer of non-woven carbon nanotube felt. The membrane can include a plurality of substantially planar layers of non-woven carbon nanotube felt. The plurality of layers can together define a spatially varying transmittance of the filter. The charged particle beam column can define a beam axis A. The detector can define an aperture substantially parallel to the absorbing surface and substantially aligned with the beam axis. The detector and filter can be configured to accommodate the aperture. The detector can include segments disposed about the aperture. The filter can include one or more filter sections arranged to shield one or more of the segments from a subset of the incident particles. The system can further include a shield, the shield being moveable relative to the detector and filter and arranged such that the filter is between the detector and the shield relative to the sample stage.

[0014] In a third aspect, a method of detecting x-rays includes directing a beam of charged particles toward a sample in a system of the previous aspect. The method includes generating detector data using the detector of the previous aspect. Generating the detector data can include applying a bias to the detector cell such that energetic particles incident in an active layer of the detector cell can generate an electric charge that is collected at a collector region of the detector cell. In some embodiments, the method of detecting x-rays can be encoded as machine-readable instructions stored on one or more machine-readable storage media. In this manner, the systems and detectors of the previous aspect can be configured to execute the instructions to cause the systems and detectors to perform the operations of the method.

[0015] The terms and expressions employed are used as terms of description and not as terms of limitation, and in using such terms and expressions there is no intention to exclude any equivalents of the features or portions thereof shown and described, but it is understood that various modifications are possible within the scope of the claimed subject matter. Thus, although the subject matter claimed herein has been specifically disclosed by embodiments and optional features, it should be understood that modifications and variations of the concepts disclosed herein may be made by those skilled in the art, and such modifications and variations are deemed to be within the scope of the present disclosure as defined by the appended claims. [Brief description of the drawings]

[0016] The foregoing aspects and many of the attendant advantages of the present disclosure will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, in which: [Figure 1A] 1 is a schematic diagram illustrating an exemplary charged particle microscope system, according to some embodiments of the present disclosure. [Figure 1B] 1B is a schematic diagram illustrating details of the exemplary charged particle microscope system of FIG. 1A, in accordance with some embodiments of the present disclosure. [Figure 2A] 1 is a schematic diagram of an exemplary charged particle detector, according to some embodiments of the present disclosure. [Figure 2B] 1 is a schematic diagram of an exemplary detector according to some embodiments of the present disclosure. [Figure 3A] 1 is a schematic diagram of an exemplary detector including a silicon drift detector according to some embodiments of the present disclosure. [Figure 3B] 1 is a schematic diagram of an exemplary detector including multiple segments in a quadrant arrangement, according to some embodiments of the present disclosure. [Figure 3C] FIG. 2 is a schematic diagram of an exemplary detector including multiple silicon drift detectors in a quadrant arrangement in accordance with some embodiments of the present disclosure. [Figure 4] 1A-1C are schematic diagrams of example filters that define spatially varying transmittance, according to some embodiments of the present disclosure. [Diagram 5] 1 is a plot of example data for normalized transmittance of a filter as a function of position, according to some embodiments of the present disclosure. [Figure 6A] 1 is a schematic diagram of an example filter that is movable relative to an example shield, in accordance with some embodiments of the present disclosure. [Figure 6B] 1 is a schematic diagram of an example filter that is movable relative to an example shield, in accordance with some embodiments of the present disclosure. [Figure 6C] 1 is a schematic diagram of an example filter that is movable relative to an example shield, in accordance with some embodiments of the present disclosure. [Figure 6D] 1 is a schematic diagram of an example filter cassette that is movable relative to an example detector cell and an example shielding, in accordance with some embodiments of the present disclosure. [Figure 7] 1 is a plot of exemplary transmittance data for multiple particles and detectors according to some embodiments of the present disclosure.

[0017] In the drawings, like reference numbers refer to like parts throughout the various views unless otherwise specified. Not every instance of an element is necessarily labeled, so as to reduce clutter in the drawings where appropriate. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles being described. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Although illustrative embodiments have been illustrated and described, it will be understood that various modifications can be made therein without departing from the spirit and scope of the present disclosure. In the following paragraphs, an embodiment of an analytical instrument system is described. For ease of explanation, the embodiments of the present disclosure focus on energy dispersive spectrometry (EDS) implemented in a scanning electron microscope. To that end, the embodiments are not limited to such instruments, but rather are contemplated for analytical instrument systems in which analysis of characteristic X-ray signals may be limited by signal-to-noise constraints or by relatively low signals. In illustrative examples, detectors of the present disclosure can be more broadly deployed as part of charged particle systems such as transmission electron microscopes, dual beam systems, triple beam systems, electron beam microanalysis systems, and the like. Similarly, while the embodiments of the present disclosure focus on X-rays resulting from inner shell excitation, additional and / or alternative X-ray signals are contemplated, including, but not limited to, continuum X-rays and / or fluorescent X-rays.

[0019] The disclosed embodiments include systems, components, and methods for improved X-ray detectors. In an illustrative example, the system can include a detector configured to generate an electrical signal in response to particles incident on an active layer of the detector, the active layer defining an absorbing surface. The system can also include a filter including a film of carbonaceous material, the filter disposed relative to the detector to shield the absorbing surface from a subset of incident particles, the subset including electrons, ions, and photons, the photons having energies less than about 40 eV. The disclosed systems, components, and methods benefit from improved stereo collection angles, higher take-off angles, thereby improving signal-to-noise characteristics, reducing collection times, and reducing electron dose to preserve dose-sensitive samples. Additionally, the disclosed embodiments exhibit improved sensitivity to relatively low energy particles (e.g., X-rays), improved sensitivity to relatively low intensity signals, and improved robustness to degradation by energetic species.

[0020] While the following detailed description focuses on embodiments of a charged particle microscope system, it is contemplated that additional and / or alternative instrument systems may be improved through the use of the described techniques and systems. In an illustrative example, the instrument system may include an analytical instrument configured to generate detector data based at least in part on the interaction of a material sample with a beam of energetic species, such as ions, electrons, and / or photons. Without being bound to a particular physical formulation, in the context of this disclosure, "particles" refers to species generated by such interactions, including, but not limited to, charged particles (e.g., ions and electrons) and photons (e.g., microwave, IR, visible light, UV, X-ray, etc.), whether or not they are in mass.

[0021] 1A is a schematic diagram illustrating an exemplary charged particle microscope 100 system according to some embodiments of the present disclosure. The exemplary charged particle microscope 100 includes multiple sections, including an electron source, a beam column 105, and a vacuum chamber 110. The electron source includes high voltage supply components, vacuum system components, and an electron emitter configured to generate an electron beam that is accelerated into the beam column 105. The beam column 105, in turn, includes electromagnetic lens elements configured to shape and form the electron beam from the electron source into a substantially circular beam having a substantially uniform profile across the beam axis A and adjusted by the objective lens 115 such that the beam is focused onto the sample 125, as described in more detail with reference to FIG. 1B.

[0022] Electron beams are typically characterized by, among other criteria, a beam current and an acceleration voltage applied to generate the beam. The range of beam current and acceleration voltage can vary between instruments and are typically selected based on the material properties of the sample or the type of analysis to be performed. In general, however, electron beams are characterized by energies of about 0.1 keV to about 50 keV (e.g., for an acceleration voltage of 0.1 kV) and beam currents of picoamps to microamps.

[0023] The vacuum chamber 110 and / or the beam column 105 may be configured to collect secondary electrons, backscattered electrons (BSE), forward scattered electrons (FSE), and / or ion beams (IonBSE), which are generated by the interaction of the electron beam with the sample, as will be described in more detail with reference to FIG. 1B. The vacuum chamber 110 may include multiple detectors for various signals, including, but not limited to, scattered electrons (FSE), x-ray photons (e.g., EDAX or EDS), other photons (e.g., visible and / or IR cameras), and / or molecular species (e.g., TOF-SIMS). The vacuum chamber 110 may also include a sample stage 120, which may be operatively coupled to a multi-axis translation / rotation control system such that the sample 125 may be repositioned relative to the beam axis A as a manner of investigating and / or imaging the sample 125. The sample stage 120 may include a window that allows transmission of electrons or other charged particles through the sample and sample stage. In this manner, one or more detectors of the present disclosure may be disposed within the vacuum chamber 110 and / or within the beam column 105 and configured to detect particles (e.g., electrons, ions, photons, etc.) emitted (e.g., reflected and / or transmitted) from the sample, as described in more detail with reference to FIGS. 2A-2B.

[0024] The exemplary charged particle microscope 100 is illustrated as a single-beam SEM instrument to focus the description on the application of the detector of the present disclosure in detecting X-rays. In some embodiments, the charged particle microscope 100 can incorporate an ion beam source (e.g., focused ion beam, or FIB) adapted, for example, to modify a sample and / or for microanalysis. In this manner, the detector of the present disclosure can be configured to generate detector data (e.g., images, line scans, X-ray spectra, etc.) in conjunction with an ion source used for modifying and / or microanalyzing the sample. In an illustrative example, a focused ion source (e.g., FIB, p-FIB, etc.) can be operably coupled to the vacuum chamber 110 and configured to incrementally remove portions of the sample 125 layer by layer. Between increments, X-ray microanalysis of the sample 125 can provide a depth profile of elemental information in the sample 125.

[0025] 1B is a schematic diagram illustrating details of the exemplary charged particle microscope system 100 of FIG. 1A, in accordance with some embodiments of the present disclosure. Detectors include one or more in-column detectors (ID) 155, pole-piece detectors (PMDs) 160, and / or a combination of the ID detectors 162 and ID detectors 164. 1, a charge-mounted detector (PMD) 160, a STEM mode detector (SMD) 165, and other detectors such as a through-the-lens detector (TLD) 170 and an Everhart-Thornley detector 175. Other detectors and sources that may be coupled to the vacuum chamber 110 include a conventional X-ray detector 130 (e.g., a silicon drift detector configured for energy dispersive X-ray spectroscopy). Embodiments of the present disclosure include charged particle microscopes, including X-ray sources, X-ray detectors, ion beam sources, mass spectrometers, light sources (e.g., laser sources), or other sources that would be included in the complement of analytical instruments available for use in SEM microanalysis. At least some of the detectors of the exemplary microscope 100 may be paired with a filter 140 in close proximity to or covering an absorbing surface of the detector, as described in more detail with reference to FIGS. 2A-3C.

[0026] The pole piece mounted detector 160 is mechanically coupled to the pole piece 117 housing the objective lens 115 and can be oriented with the collector surface facing the sample stage 120. As described in more detail with reference to Figures 2A-3C, the PMD 160 can be segmented into multiple detectors such as dipole, tripole, quadrupole, octapole, or other configurations (e.g., combinations of quadrants and other configurations). Instead of being mechanically coupled to the pole piece 117, the PMD 160 can be mounted on a retractable support 195. Advantageously, mounting the PMD 160 on a retractable support 195 allows the PMD 160 to be removed from between the sample stage 120 and the pole piece 117, thereby allowing other probes, sources, or components (e.g., a parabolic mirror used for luminescence measurement / imaging) to be introduced into the same space.

[0027] The STEM mode detector 165 can be mechanically coupled to a retractable support 195 configured to introduce the SMD 165 into a position such that the sample stage 120 is between the objective lens 115 / pole piece 117 and the SMD 165. The SMD 165 can be mechanically coupled to one or more surfaces of the vacuum chamber 110. The SMD 165 can be oriented such that an absorbing surface faces the underside of the sample stage 120. In this manner, X-rays 181 emanating from the sample 125 (e.g., from a region of the interaction volume of the sample where the X-rays are generated) can reach the detector surface and generate a characteristic signal used for imaging and / or microanalysis. The X-rays 181 can include X-rays generated from inner shell excitation of atoms of the sample 125, which are directed through the sample rather than back towards the beam column 105. In the case of the SMD 165, a filter 140 can be disposed between the detector 165 and the sample 125 to selectively detect the X-rays 181 by absorbing charged particles and relatively low energy photons.

[0028] The filter 140 may be movable relative to the detector cell, as described in more detail with reference to Figures 2A-6D. By placing the filter 140 between the absorbing surface of the detector cell and the sample, the detector can generate X-ray data with negligible or no signal due to charged particles and relatively low energy photons (e.g., infrared, visible, and / or ultraviolet photons). In this manner, embodiments of the present disclosure provide improved stereo collection angles and improved take-off angles over conventional X-ray detectors 130, resulting in improved integration times, improved signal-to-noise characteristics, and reduced exposure of sensitive samples to charged particle doses.

[0029] X-ray detector 130 includes detector 131 shielded from charged particles, photons, and other noise sources by window 133 and collimator 135, the collective result of which is a significant reduction in the volumetric collection angle. Additionally, to protect the window material and / or to reduce interactions between magnetic components of X-ray detector 130 and the charged electron beam, X-ray detector 130 may be limited to a relatively low take-off angle, for example, about 30 degrees to about 50 degrees, measured from a plane defined by sample surface 125. The take-off angle may be increased by tilting sample 125, at the expense of reducing the functionality of detectors 155, 160, 165, and 170 during X-ray collection.

[0030] 2A is a schematic diagram of an exemplary particle detector 200, in accordance with some embodiments of the present disclosure. The exemplary detector 200 is an example of the detectors described with reference to FIG. 1B, such as the ID 155, the PMD 160, and / or the SMD 165. As such, the exemplary detector 200 includes a retaining element 205, a detector cell 207, and a filter 210. The detector cell 207 includes an acceptor layer 215, a first conductive layer 220, and a second conductive layer 225.

[0031] The retaining element 205 may be configured to be incorporated into a scanning electron microscope (SEM), as described in more detail with reference to FIGS. 1A-1B. The retaining element 205 may include mechanical fittings, couplings, and / or features that correspond to a given SEM system. For example, in PMD 160, the retaining element 205 may include one or more through holes disposed in the housing corresponding to the location of threaded bore holes in the pole piece 117, which facilitates mechanical coupling between the retaining element 205 and the pole piece 117. The pole piece 117 may be configured differently for different SEM systems. For example, some manufacturers may omit some features in favor of other features, such that the configuration of the retaining element 205 may be based at least in part on the charged particle microscope in which the retaining element 205 is incorporated. Similarly, the retaining element 205 may be configured to mechanically couple with a support (e.g., retractable support 195 of FIG. 1B). As will be described in more detail with reference to Figure 6A, the support can be a retractable arm that allows the exemplary detector 200 to be oriented towards a sample and / or beam target (e.g., sample 125 of Figure 1). In this manner, the holding element 205 can tilt and / or move linearly.

[0032] The detector cell 207 can be mechanically coupled to the retaining element 205, for example, by adhesive, retaining clips, tensioners, screws, etc. The acceptor layer 215 can define a first surface 217 and a second surface 219. The second surface 219 is illustrated as facing the first surface 217, but can be configured differently. The first conductive layer 220 can be disposed over the first surface 217. The second conductive layer 225 can be disposed over the second surface 219. In some embodiments, the first conductive layer 220 and / or the second conductive layer 225 can be or include a metal, a transparent conductive material, a conductive carbon film, and / or other conductive material compatible with chemical vapor deposition, physical vapor deposition, epitaxy, or other techniques used to deposit conductive materials with controlled purity and thickness on the order of tens to hundreds of nanometers. To that end, the first conductive layer 220 can be characterized by a substantially uniform thickness that is below (e.g., limited by and within the tolerances of the manufacturing process) the threshold at which the conductive material interferes with the incident particles. The first conductive layer 220 can be disposed as a patterned film or layer (e.g., in the shape of a grid or other geometric configuration) over the acceptor layer that is used to distribute the electrostatic field over the surface. In this case, the first surface 217 is not covered by the material of 220 in the mesh of the grid, which can improve detection of some of the incident particles.

[0033] The acceptor layer 215 may be characterized by a thickness 230 between the first conductive layer 220 and the second conductive layer 225 of about 10 μm to about 500 μm, including subranges, fractions, and interpolations thereof. As described in more detail with reference to FIG. 1B, space constraints in the region between the sample stage 120 and the pole piece 117 work against larger values ​​of thickness 230. For example, contact between the sample stage and the charged particle detector 200 may damage the first conductive layer 220 and / or the acceptor layer 215. In contrast, smaller values ​​of thickness 230 may increase the likelihood that a particle incident on the first surface 217 of the acceptor layer 215 will pass through the acceptor layer 215 without generating a detectable signal or reduce the efficiency of the detector at higher particle energies.

[0034] In some embodiments, the detector cells 207 and / or retaining element 205 define an aperture 235. An aperture may be included in the exemplary detector 200 to allow an electron beam (e.g., electron beam 190 of FIG. 1B) to pass through the retaining element 205 and / or detector cells 207. Although the nominal diameter of the electron beam may be on the order of tens of nanometers, electromagnetic interactions between the detector cells 207 and the electron beam may affect the value of the diameter 240, below which the beam is affected by the presence of the detector 200 (e.g., the beam is deformed or at least partially blocked or interferes with the detector cells 207). For at least these reasons, the aperture 235 may be characterized by a diameter 240 of about 0.1 mm to about 10 mm, including subranges, fractions, and interpolations thereof. For example, diameter 240 can be about 0.1 mm, about 0.2 mm, about 0.3 mm, about 0.4 mm, about 0.5 mm, about 0.6 mm, about 0.7 mm, about 0.8 mm, about 0.9 mm, about 1.0 mm, about 2.0 mm, about 3.0 mm, about 4.0 mm, about 5.0 mm, about 6.0 mm, about 7.0 mm, about 8.0 mm, about 9.0 mm, or about 10.0 mm, including fractions and interpolations thereof.

[0035] As described in more detail with reference to FIG. 1B, the angular distribution of the particles of interest (e.g., X-rays 181 in FIG. 1B) relative to the sample 125 surface may act as a constraint on the diameter 240 of the aperture 235. For example, in the case of an X-ray detector, the X-ray flux increases closer to the beam axis A, and as a result, detector performance generally improves for smaller values ​​of diameter 240. In contrast, interference between the detector 200 and the electron beam 190 may impair the functionality of the charged particle microscope system and / or the detector 200. In this manner, the diameter 240 may be limited by a lower threshold below which the detector 200 interferes with the operation of the charged particle microscope, and by general design considerations for reducing the diameter 240.

[0036] In some embodiments, a conductive film 245 (e.g., gold, aluminum, etc.) can be disposed over the interior surface of the aperture. The conductive film 245 can be electrically coupled to the first conductive layer 220 or the second conductive layer 225, or can be electrically isolated from both the first conductive layer 220 and the second conductive layer 225. The conductive film 245 can be included as part of incorporating the exemplary detector 200 into the beam column 105, for example, by shielding the acceptor layer from primary electrons, secondary electrons 185, etc.

[0037] The detector cell 207 can be shaped to accommodate the aperture 235. In this context, accommodating the aperture 230 refers to the aperture 235 extending through the detector cell 207 and perforating the first conductive layer 220, the acceptor layer 215, and the second conductive layer 225 such that the beam axis passes through the aperture 235 and the first conductive layer 220 is oriented facing the sample stage 120 to act as an absorbing surface, as described in more detail with reference to FIG. 1B. For example, a charged particle detector 200 configured as a PMD 160 can include the aperture 235 and the detector cell 207 is shaped to accommodate the aperture 235. In contrast, the aperture 235 can be formed in the holding element 205 rather than the detector cell 207 in a configuration in which the signal of interest radiates from the sample 125 at an angle between the beam axis A and the sample surface.

[0038] The exemplary detector 200 is shown in an annular form factor. Embodiments of the present disclosure include additional and / or alternative form factors, including, but not limited to, rectangular or other polygonal form factors. Similarly, the schematic diagram of FIG. 2A is not intended to limit the geometric arrangement of the components of the exemplary detector 200. The exemplary detector 200 is illustrated in a concentric configuration with the aperture 235 located substantially at the center of the detector cell 207. However, in some embodiments, the aperture 235 can be offset relative to the geometric center of the detector cell 207, for example, where the detector cell 207 is shaped to collect particles that emanate from a particular angle relative to the beam axis A and / or over a range of angles that are not rotationally symmetric about the beam axis A.

[0039] 2B is a schematic diagram of an exemplary detector 250 according to some embodiments of the present disclosure. The exemplary detector 250 includes a detector cell 207 having an acceptor layer 215, a first conductive layer 220, and a second conductive layer 225, and is mechanically coupled to a holding element 205, as described with reference to FIG. 2A. The exemplary detector 250 includes a first contact 255, a second contact 260, a bias circuit 265, and a current measurement circuit 270.

[0040] The first contact 255 is electrically coupled to the first conductive layer 220. The second contact 260 is electrically coupled to the second conductive layer 225. In this manner, the exemplary detector 250 may be configured to apply a bias voltage across the acceptor layer 215. For example, the bias circuit 265 may be configured to apply a bias voltage across the acceptor layer 215 having a magnitude between about 0.1 V and about 5 kV, including subranges, fractions, and interpolations thereof. A larger magnitude of the bias voltage increases the likelihood that the charged particle detector will interfere with the operation of the charged particle microscope (e.g., by forming a localized discharge or by deflecting and / or distorting the primary electron beam 190). In contrast, a smaller magnitude of the bias voltage may impair the performance of the charged particle detector of the present disclosure (e.g., by promoting electron-hole recombination).

[0041] Without being bound to a particular physical mechanism or phenomenon, the particle detector of the present disclosure may be configured to generate an electrical signal in response to the incidence of an energetic particle 275 (e.g., X-ray 181 in FIG. 1A ) on an absorbing surface 217 of the acceptor layer 215 (e.g., through an orientation of the first conductive layer 220 toward the sample stage 120). The entry of the energetic particle 275 into the acceptor layer may generate an electron-hole pair, which may be separated and driven into the respective conductive layer by the force of a bias voltage. The current measurement circuitry 270 may be configured to integrate the current drawn from the acceptor layer 215 and / or returned to ground or a relative ground over a period of time (e.g., as part of imaging or in coordination with the scanning pattern of the SEM for a defined exposure time for spot mode analysis). The magnitude of the bias voltage may be based at least in part on the thickness 230 of the acceptor layer 215 as a way to improve detector efficiency (eg, by reducing the probability of electron-hole recombination in the acceptor layer 215).

[0042] The filter 210 can include a membrane 211. The membrane 211 can include a material that exhibits selective transmittance for X-rays 275. Selective transmittance refers to the membrane 211 allowing at least a portion of incident X-rays 275 of a given energy to pass through the filter 210 while absorbing, reflecting, or otherwise blocking the transmission of other forms of incident particles, such as photons 277 and charged particles 279 (e.g., electrons, ions, etc.) of relatively low energy. The material of the membrane 211 can block all or substantially all photons 277 and charged particles 279 below a respective threshold energy. For example, the membrane 211 can absorb, reflect, or otherwise block substantially all electrons having an energy of about 7.8 keV or less, as described in more detail with reference to FIG. 7. In some embodiments, the threshold energy can be selected based at least in part on the thickness of the filter and / or the density of the filter as parameters. For example, a filter having a thickness of about 2 um can block incident electrons having an energy below about 2.5 keV. Although below 7.8 keV, the thickness dependence of the filter performance allows for tuning of operating conditions, as will be described in more detail with reference to FIGS. 4-7. Additionally, the threshold energy may depend at least in part on the composition of the membrane 211. For example, a membrane 211 including multi-walled carbon nanotubes may be characterized by a higher threshold energy as compared to a membrane 211 including single-walled carbon nanotubes. Similarly, a membrane 211 having a relatively high density of nanotubes per unit surface area may be characterized by a higher threshold energy than a membrane 211 having a relatively low density of nanotubes per unit surface area. In an illustrative embodiment, areal density is defined as the mass of membrane 211 material per unit surface area (e.g., square centimeter). Properties of the membrane 211 may be described and / or related via areal density based at least in part on characteristic volumetric properties including the volumetric density (e.g., mass per volume) of the carbon material and / or the porosity of the membrane (e.g., the average percentage of empty space within the membrane). In some embodiments, the volumetric density of the carbon material is about 0.11 g / cm 3 ~Approx. 1.1g / cm 3including subrange fractions and interpolations therein. In some embodiments, transparency and thickness are inversely related. For example, for a given areal density, a film thickness of about 1.32 μm may correspond to a transmittance at 550 nm of about 3.5%, while a film thickness of about 2.64 μm may correspond to a transmittance of about 0.12%. In this way, for a given film, both the film thickness and transparency can be translated into areal density. For example, an areal density of about 0.1 μg / cm 2 ~About 330mg / cm 2 , including subranges, fractions, and interpolations thereof, allowing the dimensions of film 211, the number of layers, and the thicknesses of the individual layers to be determined based at least in part on a balance between transparency and dimensional / spatial constraints.

[0043] In some embodiments, the membrane 211 includes a carbonaceous material 213. The carbonaceous material 213 can include carbon nanotube material. The carbon nanotube material can include single-walled nanotubes, double-walled nanotubes, multi-walled nanotubes, and / or mixtures thereof. The carbonaceous material 213 can include carbon nanofibers, nanotubes, sp 2 Hybridized carbon, sp 3Other forms of hybrid carbon and / or mixtures thereof (e.g., a combination of graphite and amorphous carbon) may be included. The nanotubes, nanotubes, and / or nanofibers may be oriented along one or more in-plane directions and / or may be randomly oriented. For example, the membrane 211 may include a layer in which the carbon nanotubes making up the carbon nanotube felt are substantially aligned with the orientation direction. Different layers may be oriented in the same direction or different directions. While substantially aligned with the orientation direction on a given layer and / or membrane 211, individual nanotubes, nanofibers, etc. may exhibit twisting (e.g., curvature, angulation / kinking, looping, and / or helical twisted segments) such that segments of a given nanotube, nanofiber, etc. may be oriented away from the orientation direction. The membrane 211 may further include metal, ceramic, and / or nitride materials, for example, as coatings, inclusions, or other forms that do not substantially limit the permeability of the filter 210. The membrane 211 may be electrically coupled to an electrical potential (e.g., ground potential, positive bias, negative bias). Advantageously, electrically grounding the membrane 211 can improve absorption and / or neutralization of the charged particles 279 (e.g., absorption of electrons and / or surface recombination of ions) without significantly affecting the performance of other components of the charged particle microscope system in which the exemplary detector 250 is disposed.

[0044] Membrane 211 can have a thickness on the order of about 10 nm to about 10 um (e.g., about 10 nm to about 99 um), including subranges (e.g., about 0.5 um to about 30 um), fractions, and interpolations thereof. Membrane 211 can include multiple layers of carbon nanotube material, individually about 3 nm to about 1 um thick, including subranges, fractions, and interpolations thereof. In one embodiment, each layer can have a thickness of about 0.4 um, such that a membrane having two layers of carbon nanotube material can be about 0.8 um thick, and a membrane having 25 layers of carbon nanotube material can be about 10 um thick. Without being bound to a particular physical phenomenon or mechanism, filter 210 can have a thickness dependent transmittance based at least in part on the absorbance of each constituent layer. In this manner, the film 211 may include several layers that allow the filter 210 to absorb substantially all incident photons 277 and / or charged particles 279 while allowing a significant portion of the X-rays 275 to pass through.

[0045] Each layer can have a photon absorption (measured, for example, at 525 nm) of about 1% to about 90%. In an example of a 25-layer carbon nanotube material, with each layer having an absorbance of about 40% at 525 nm, the overall absorption coefficient of the film 211 for photons at 525 nm is about 1×10 -9 In an embodiment of the membrane 211 having a thickness of about 2 um, the transmission of Li Kα (55 eV) x-rays 275 can be about 23%, which represents about a 5-fold improvement over current detectors (as described with reference to FIG. 7). Furthermore, current technology comparative detectors that include carbon materials as part of the window layer typically include a support grid that introduces artifacts and a light blocking aluminum coating on at least one surface of the window layer, which further reduces the quantum efficiency of the detector. In contrast, detectors of the present disclosure can include an at least partially unsupported membrane 211 held by a frame (e.g., frame 315 of FIG. 3A) around at least a portion of the membrane 211.

[0046] The exemplary detector 250, like the exemplary detector 200, can be configured to be incorporated into the exemplary charged particle microscope 100 of FIGS. 1A-1B. Additionally, components and / or materials of the exemplary detector 250 can be included as part of the exemplary detector 200 and omitted from FIG. 2A and its accompanying description to focus on geometrical aspects. To that end, FIG. 2B is provided to describe electronic and material aspects of the detector of the present disclosure. In an illustrative embodiment, the exemplary detector 250 can include the aperture 235 of the exemplary detector 200. Similarly, the exemplary detector 200 can include the electronic components and materials of the detector 250.

[0047] 3A is a schematic diagram of an example detector 300 including a silicon drift detector cell 305, according to some embodiments of the present disclosure. The example detector 300 further includes a filter 310 and electronic circuitry 350 electrically coupled to the silicon drift detector cell 305. For example, the detector 305 may include an absorbing surface 335 and a set of annular electrical contacts 340 patterned on a surface of the detector 305 such that charges generated within an active layer of the detector 330 (e.g., active layer 215 of FIG. 2A ) are attracted toward a central anode region 345 of the detector cell 305.

[0048] The filter 310 includes a membrane 311 within a frame 315. The frame is coupled to a holding arm 320 that can position the filter 310 relative to the detector cell 305. In some embodiments, the filter 310 can be moved relative to the detector cell 305. As shown, the filter 310 is positioned between the x-ray source 317 and the detector 305. In this manner, the filter can selectively absorb, reflect, or otherwise block incident particles other than x-rays 375.

[0049] 2B , the membrane 311 includes multiple layers 313 of filter material. A frame 315 may be coupled to the membrane 311 over at least a portion of the periphery of the membrane 311. In this manner, the frame 315 mechanically supports the membrane 311, allowing the membrane 311 to be substantially freestanding over the region of the filter 310 corresponding to the detector 305.

[0050] 3B is a schematic diagram of an exemplary detector 330 including multiple filter segments 355 in a quadrant arrangement, according to some embodiments of the present disclosure. The segments 355 can be formed from a single membrane 311 supported by a circular frame 315. In this manner, the filter 310 can accommodate an aperture 370 (e.g., aperture 235 in FIG. 2A) through which, for example, a beam of charged particles can be directed. Additionally or alternatively, the segments 355 can be formed from multiple membranes 311. The segments can have similar or different properties, such as thickness, transmittance, etc. Advantageously, different segments can enable different detector segments to interrogate different energy ranges, for example, by applying different absorption coefficients to X-rays (e.g., X-rays 181 in FIG. 1B) at a given energy of interest for a given sample.

[0051] 3C illustrates a portion of an exemplary detector module 330 obscured by a filter 310 including a detector surface having a quadrant arrangement of multiple silicon drift detectors 305, according to some embodiments of the present disclosure. The exemplary detector module 330 can accommodate the central aperture 370 by including, among other things, multiple silicon drift detectors 305 that are relatively small or otherwise shaped to be arranged in an arrangement around the central aperture 370 that optimizes collection efficiency. The number and arrangement of silicon drift detectors 305 can vary based at least in part on the size of the detector module 330 and the size of the silicon drift detectors 305.

[0052] In some embodiments, one or more charged particle detectors 360 may be included along with the silicon drift detector 305. Advantageously, the filter 310 may be at least partially absent from the vicinity of the charged particle detector 360, for example, by forming an opening in the membrane 311 and / or by omitting one or more segments 355 from the filter 310. In this manner, the exemplary detector module 330 may generate a multi-modal detector data set that simultaneously includes X-ray data (e.g., EDS data) and electron data (e.g., BSE data, SE data, etc.). Such data of different modalities may be stored separately and correlated as part of a data cube, for example, with reference to a position on the sample surface as part of an imaging / mapping process.

[0053] 4 is a schematic diagram of an exemplary filter 400 that defines a spatially varying transmission coefficient or transmittance, according to some embodiments of the present disclosure. The exemplary filter 400 includes multiple layers 405 of filter material. The layers 405 are coupled to a frame 410. As described in more detail with reference to FIG. 3A, the layers 405 and frame 410 can be structured such that the filter is disposed relative to an X-ray detector to shield an absorbing surface (e.g., first surface 217 of FIG. 2A) from incident particles including electrons, ions, relatively low energy photons, etc.

[0054] As described in more detail with reference to FIGS. 2B-3A, the layers 405 can include carbon nanotube material. For example, the carbon nanotube material can include multi-walled carbon nanotubes. Additionally, the carbon nanotube material can be formed of a non-woven felt. In some embodiments, the exemplary filter 400 is configured such that the layers 405 differ from one another by one or more properties and / or parameters, such that the exemplary filter 400 exhibits spatially varying transmittance. In one example, the change in transmittance can be the result of physical modification of the filter by a directed energy tool (e.g., via a laser, electron beam, ion beam, etc.). In this manner, the total thickness of the filter can be spatially varied. The spatial variation can be achieved by including layers 405 having different lateral and / or thickness dimensions. In the illustrated example of FIG. 4, the exemplary filter 400 includes a first layer 405-1 having a first length that is longer than a second length of a second layer 405-2. The result, when reproduced by the multiple layers 405 of the exemplary filter 400, is a substantially linear (e.g., stepped) dependence of the transmittance on lateral position in the exemplary filter 400, as described in more detail with reference to FIG. 5. Similar results can be obtained by spatially thinning the layers 405, in addition to or as an alternative to truncating the layers 405. For example, the first layer 405-1 can be relatively thinner and / or relatively thicker than the second layer 405-2 at different lateral positions within the first layer 405-1. In this way, the exemplary filter 400 can define any spatial transmittance variation (e.g., a Gaussian shape as illustrated in FIG. 5).

[0055] The exemplary filter 400 can define a spatially varying transmittance that provides one or more regions of relatively high transmittance and one or more regions of relatively low transmittance. In some embodiments, the exemplary filter 400 also includes various features 415. The features 415 can include through holes, slits, apertures, and / or other patterns that are transferred onto and / or into the one or more layers 405 by material removal and / or deposition. The features 415 can be at least partially aligned, such as a concentric arrangement of apertures that together define a Gaussian transmittance profile. As described in more detail with reference to FIG. 3C, the features 415 can include apertures that are substantially aligned with the charged particle detector 360, thereby enabling the detector of the present disclosure to simultaneously generate x-ray and electron microscopy (e.g., electron image) data.

[0056] In some embodiments, the layer 405 is coupled to the frame 410 on a single side, but can also be coupled to the frame 410 on multiple sides, as illustrated in FIG. 3A. In some embodiments, each layer 405 is held within a respective frame 410, such that the filter 400 includes multiple frames. As described in more detail with reference to FIGS. 6A-6C, such a configuration can enable the filter 400 and / or individual filter layers 405 to be addressable and / or movable, allowing the transmittance of the filter 400 to be dynamic. Advantageously, dynamically varying the transmittance of the filter allows the properties of the filter to be tuned to the properties of a given sample (e.g., sample 125 of FIG. 1A). In an illustrative example, a sample that emits a relatively high percentage of backscattered electrons (e.g., a relatively heavy element) may benefit from a relatively lower overall transmittance implemented by including more layers 405, while a sample that emits a relatively low percentage of x-rays may benefit from a relatively higher transmittance implemented by removing one or more layers 405. In this manner, a single filter 400 may provide a range of transmittance values.

[0057] FIG. 5 is a plot of example data for normalized transmittance of a filter as a function of position, according to some embodiments of the present disclosure. The plot includes simulated data for positionally varying transmittance for a given energy, normalized to a maximum value at a given position. The distribution may result from spatial modification of the filter (e.g., layer 405 of FIG. 4), as described in more detail with reference to FIG. 4. The positionally varying transmittance may exhibit a "step" distribution 505 corresponding to a series of truncated layers. If the layer is patterned by localized removal of material, for example by ion milling of the filter material (e.g., carbon nanotube felt), the transmittance may exhibit a smooth distribution 510 with respect to position, based at least in part on the extent of the local removal. As described with reference to FIG. 4, the transmittance may follow a nonlinear function, such as a Gaussian 515 distribution centered on a central position.

[0058] 6A is a schematic diagram of an exemplary filter 610 that is movable relative to an exemplary shield 615, according to some embodiments of the present disclosure. The filter 610 includes multiple layers of membrane 605 material and a retaining member 611, as described in more detail with reference to FIGS. 2A-5. The retaining member (e.g., frame 315 and support 320 of FIG. 3A) may be movable relative to the shield 615 such that the shield 615 and / or filter 610 can be moved relative to a detector cell (e.g., detector cell 207 of FIG. 2A).

[0059] The shielding 615 can be or can include a material that is opaque to multiple types of incident particles, such as x-rays 620, other photons 625, electrons 630, and / or ions 635. The shielding 615 can include a conductive material (e.g., metal, etc.) that allows the shielding to absorb, reflect, or otherwise block particles through a combination of physical and dimensional properties. Advantageously, the shielding 615 allows the filter 610 and / or detector to be protected from damaging particles. In an illustrative example where the detector is disposed in a dual beam system, the shielding can be moved into place or the filter and / or detector can be moved behind the shielding during operation of a focused ion beam that generates a relatively high ion flux that would otherwise damage the filter and / or detector.

[0060] FIG. 6B illustrates how an exemplary filter 610 that is movable relative to an exemplary shield 315 can also facilitate variable transmission. In the illustrated embodiment of FIG. 6B, a cassette of filter 610 elements is protected by the shield 615 when retracted and can be rotated into position above the detector when in use. The transmission is then proportional to the number of filter 610 elements in place. The rotational motion is illustrated in FIG. 6C, which shows the rotational motion of multiple filter elements 610. In some embodiments, the motion is linear rather than rotational, and the filter 610 elements are retracted behind the shield 615 via linear translation. The shield 615 can be movable relative to the filter 610 elements and / or the detector. For example, the shield can be moved to a position that protects the filter 610 elements and the detector, such as when a process that creates an environment that is harmful to the detector (e.g., ion beam milling of a sample that creates significant ion and electron flux) is performed.

[0061] 6D is a schematic diagram of an example filter cassette 640 that is movable relative to the example detector cell 305 and the example shield 615, according to some embodiments of the present disclosure. The example filter cassette 640 represents an alternative embodiment in which the membrane material 605 is held in a frame that contains multiple filter 610 elements. The different filter 610 elements can have different transmission characteristics. For example, a first filter element 610-1 can have a relatively higher transmission at a given energy than a second filter element 610-2 in the cassette 640. In this manner, by moving the cassette 640 relative to the detector cell 305, a given energy can be selected by suppressing background signals of lower energies.

[0062] FIG. 7 is a plot of exemplary transmittance data for multiple types of detectable signals according to some embodiments of the present disclosure. The plot of FIG. 7 provides experimental data that demonstrates the improved performance of the detector of the present disclosure compared to a detector including a beryllium filter. The detector of the present disclosure shows improved x-ray transmittance over a beryllium window, as well as reduced electron transmittance and reduced artifact content over a polymer or silicon nitride window. For example, polymer and silicon nitride windows are typically supported by grids or other structures to structurally reinforce the window. These structures can reduce the quantum efficiency of the detector and introduce artifacts due to the material from which the structure is made.

[0063] In the plot, the abscissa and ordinate plot the transmittance of the filter for x-rays (dashed line) and electrons (solid line) versus energy in electron volts. Transmittance data for the filters of the present disclosure are provided as open circles (o) for the x-ray data and open squares (□) for the electron data. The dashed and dotted line (-·-) provides a simulated x-ray transmittance curve for a filter of the present disclosure, and the dashed line (---) provides a simulated x-ray transmittance curve for a conventional x-ray detector with a pure beryllium window (e.g., detector 130 of FIGS. 1A-1B).

[0064] The data in Figure 7 illustrates that the detector of the present disclosure exhibits improved sensitivity to X-rays compared to a beryllium filtered detector. Additionally, the detector of the present disclosure is substantially blind to electron flux as evidenced by the transmission of the filter of the present disclosure being at or near zero percent for electrons having energies below about 7.8 keV, which corresponds to nearly two orders of magnitude greater energy than the Mo La X-ray line. In contrast to typical polymer membrane windows, the detector of the present disclosure provides improved X-ray sensitivity and electron opacity.

[0065] Additionally, the detectors of the present disclosure outperform current technology beryllium filtered detectors over a range of x-ray energies from about 75 eV to about 1150 eV, encompassing numerous characteristic x-ray lines for elements including, but not limited to, beryllium (Kα), boron (Kα), manganese (Lα), fluorine (Kα), iron (Lα), nickel (Lα), copper (Lα), aluminum (Kα), silicon (Kα), and molybdenum (Lα). In an illustrative example drawn from the data of FIG. 7, the detectors of the present disclosure show about a 20% to about a 40% improvement in transmission for the iron, nickel, and copper Lα lines compared to the beryllium filtered detector. Advantageously, the filters of the present disclosure are substantially opaque to visible and infrared photons (e.g., photon 277 of FIG. 2B). In this manner, the detectors of the present disclosure can be used to measure luminescent and / or heated samples where current detector technology may result in significant photon noise in the detector data.

[0066] Various embodiments have been described in the preceding specification. For purposes of explanation, specific configurations and details have been set forth to provide a thorough understanding of the embodiments. However, it will be apparent to one skilled in the art that the embodiments may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified so as not to obscure the described embodiments. Although the exemplary embodiments described herein are centered around spectrometry systems, specifically X-ray spectrometry systems, these are intended to be non-limiting, illustrative embodiments. The embodiments of the present disclosure are not limited to such embodiments, but rather are intended to be directed to analytical instrument systems capable of analyzing a wide range of material samples to determine chemical, elemental, physical, structural or other properties, including, but not limited to, chemical structure, trace element composition, and the like, among other aspects.

[0067] Some embodiments of the present disclosure include a system including one or more data processors and / or logic circuitry. In some embodiments, the system includes a non-transitory machine-readable storage medium including instructions that, when executed on the one or more data processors and / or logic circuitry, cause the one or more data processors and / or logic circuitry to perform some or all of one or more methods and / or some or all of one or more processes or workflows disclosed herein. Some embodiments of the present disclosure include a computer program product tangibly embodied in a non-transitory machine-readable storage medium including instructions configured to cause one or more data processors and / or logic circuitry to perform some or all of one or more methods and / or some or all of one or more processes disclosed herein.

[0068] The terms and expressions used are used as terms of description and not as terms of limitation, and in using such terms and expressions, there is no intention to exclude any equivalents of the features or portions thereof shown and described, but it is understood that various modifications are possible within the scope of the claims. Thus, although the present disclosure includes specific embodiments and optional features, it should be understood that modifications and variations of the concepts disclosed herein can be made by those skilled in the art, and such modifications and variations are considered to be within the scope of the appended claims.

[0069] When a term is used without an explicit definition, it is understood that the ordinary meaning of the word is intended unless the term has a special and / or specific meaning in the field of charged particle microscope systems or other related fields. The term "about" or "substantially" is used to indicate a deviation from a described characteristic, within which there is little or no effect on the corresponding function, characteristic, or attribute of the described structure. In the illustrated examples where a dimensional parameter is described as "substantially equal" to another dimensional parameter, the term "substantially" is intended to reflect that the two parameters being compared may not be equal within acceptable limits, such as manufacturing tolerances or confidence intervals inherent in the operation of the system. Similarly, when a geometric parameter such as alignment or angular orientation is described as "about" perpendicular, "substantially" perpendicular, or "substantially" parallel, the term "about" or "substantially" is intended to reflect that the alignment or angular orientation may vary from the strictly described condition (e.g., not strictly perpendicular), within acceptable limits. For dimensional values ​​such as diameter, length, width, etc., the term "about" can be understood to describe a deviation of up to ±10% from the described value. For example, a dimension of "approximately 10 mm" can describe a dimension between 9 mm and 11 mm.

[0070] This specification provides exemplary embodiments and is not intended to limit the scope, applicability, or configuration of the present disclosure. Rather, the description following the exemplary embodiments provides those skilled in the art with an enabling description for implementing various embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the spirit and scope as set forth in the appended claims. Specific details are given herein to provide a thorough understanding of the embodiments. However, it will be understood that the embodiments may be practiced without these specific details. For example, specific system components, systems, processes, and other elements of the present disclosure may be shown in schematic diagram form or omitted from the illustrated diagrams so as not to obscure the embodiments in unnecessary detail. In other cases, well-known circuits, processes, components, structures, and / or techniques may be shown without unnecessary detail.

Claims

1. A detector comprising: a detector cell configured to generate an electrical signal in response to a particle incident on an active layer of the detector cell, the active layer defining an absorbing surface; a filter comprising a film of a carbon material, the filter disposed relative to the detector cell to shield the absorbing surface from a subset of the incident particles, the subset including electrons, ions, and photons, the photons having energies less than about 40 eV.

2. The detector of claim 1 , wherein the carbon material comprises carbon nanotubes.

3. The detector of claim 1 , wherein the carbon material comprises a layer of non-woven carbon nanotube felt.

4. The detector of claim 3 , wherein the membrane comprises a plurality of substantially planar layers of carbon nanotube felt.

5. The detector of claim 4 , wherein the plurality of substantially planar layers together define a spatially varying transmittance of the filter.

6. The detector of claim 3 , wherein the filter comprises a frame in which the layer is disposed.

7. The detector of claim 6 , further comprising a plurality of frames comprising said frame, said plurality of frames being individually addressable and individually movable relative to said detector cells.

8. The detector of claim 1 , defining an aperture substantially parallel to the absorbing surface, the detector cell and the filter configured to accommodate the aperture.

9. 9. The detector of claim 8, wherein the detector comprises segments arranged about the aperture, and the filter comprises one or more filter sections arranged to shield one or more of the segments from the subset of incident particles.

10. 10. The detector of claim 1, further comprising a shield, the shield being movable relative to the detector cell and the filter and disposed such that the filter is between the detector and the shield.

11. 10. The detector of claim 1, further comprising a holding element configured to dispose the detector and the filter within a vacuum chamber of a charged particle microscope and configured to orient the detector relative to a sample stage of the charged particle microscope such that the filter is disposed between a sample stage and the detector.

12. The detector of claim 1 , wherein the detector comprises a silicon drift detector.

13. 1. A charged particle beam system comprising: A vacuum chamber; a charged particle beam column operatively coupled to the vacuum chamber and configured to direct a beam of charged particles into the vacuum chamber; a sample stage disposed within the vacuum chamber; A detector comprising: a detector cell configured to generate an electrical signal in response to a particle incident on an active layer of the detector cell, the active layer defining an absorbing surface oriented towards the sample stage; a filter comprising a film of a carbon material, the filter being disposed between the sample stage and the detector to shield the absorbing surface from a subset of the incident particles, the subset including electrons, ions, and photons having energies less than about 40 eV; and a detector.

14. The system of claim 13 , wherein the carbon material comprises carbon nanotubes.

15. The system of claim 13 , wherein the carbon material comprises a layer of non-woven carbon nanotube felt.

16. The system of claim 15 , wherein the membrane comprises a plurality of substantially planar layers of non-woven carbon nanotube felt.

17. 17. The system of claim 16, wherein the plurality of substantially planar layers together define a spatially varying transmittance of the filter.

18. 14. The system of claim 13, wherein the charged particle beam column defines a beam axis A, the detector defines an aperture substantially parallel to the absorbing surface and substantially aligned with the beam axis, and the detector and filter are configured to accommodate the aperture.

19. 20. The system of claim 18, wherein the detector comprises segments arranged about the aperture, and the filter comprises one or more filter sections arranged to shield one or more of the segments from the subset of incident particles.

20. 14. The system of claim 13, further comprising a shield, the shield being movable relative to the detector and the filter, and the filter being disposed relative to the sample stage such that the filter is between the detector and the shield.

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