Shielded detector for charged particle microscopy

Abstract

The invention relates to a shielded detector for charged particle microscopy. Systems, components, and methods for detecting a characteristic signal are described. The detector includes a detector unit. The detector cell may be configured to generate an electrical signal in response to particles incident on an active layer of the detector cell, which may define an absorbing surface. The detector may include a filter. The filter may include a film of carbon material. The filter may be disposed relative to the detector unit to shield the absorbing surface from a subset of 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.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. non-provisional application No. 18 / 456,048, filed on August 25, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] Embodiments of the present disclosure relate to charged particle microscopy systems, components, and methods for their operation.Some embodiments relate to components configured for detecting x-rays. Background Art

[0004] In charged particle microscopy, characteristic x-rays are produced by exciting inner shell electrons when the beam interacts with atoms of the sample. The x-ray signal is often used for elemental analysis in a scanning electron microscope (SEM) system. For example, the x-ray signal can be used to produce an energy dispersive x-ray (EDS) spectrum, from which the elemental composition of the sample can be measured.

[0005] Conventional EDS detectors are built around detector cells. The detector cell 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 in the SEM, for example, as a result of secondary phenomena other than direct interrogation of the sample. For this reason, a typical x-ray EDS detector incorporates a collimator assembly that blocks x-rays originating from outside the region excited by the electron beam. In practice, the collimator reduces the number of stray x-rays from other parts of the microscope chamber included in the analysis, but also significantly limits the stereo collection angle of the EDS detector.

[0006] Conventional detectors are sensitive to different types of incident particles. Ions, electrons, photons and other forms of radiation within the ultraviolet, visible and / or infrared spectra can cause noise in EDS data. This noise can mask signals attributable to low-energy x-rays and / or low-intensity x-rays. For this reason, a typical x-ray EDS detector includes a window between the detector and the vacuum chamber. There are two main types of window materials: a beryllium (Be) window that strongly absorbs low-energy X-rays, which means that only sodium (Na) or heavier elements can be detected; and a polymer-based window, which allows detection of X-rays as low as 100 eV, but is far less robust than a Be window and is radiation-sensitive (polymer windows can be degraded by electrons, ions and photons). Polymer windows are typically supported by grids or other structures for structural enhancement, but such grids also introduce artifacts into EDS data.

[0007] In another example, an EDS detector typically includes a device to divert electrons away from the detector that would otherwise cause background noise and overload the detector electronics. The electron diverting device is typically a permanent magnet that strongly deflects any passing electrons. Such a device is typically included in detectors that use polymer windows because thicker beryllium windows absorb electrons with energies below 20 keV. However, permanent magnets interfere with beam properties that are very close to the primary beam. For this reason, a typical EDS detector is 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 a detector mounted on a pole piece.

[0008] As a result of the above-mentioned engineering constraints, EDS detectors are typically limited to stereo collection angles, relatively low take-off angles, insensitivity to low energy x-rays that are difficult to distinguish from background noise, sensitivity to noise generated by extraneous signals, and sensitivity to degradation caused by high energy species. Therefore, there is a need for improved EDS detectors that exhibit improved stereo collection angles, improved take-off angles, and improved sensitivity to x-rays relative to noise sources (e.g., electrons, ions, and photons). Summary of the invention

[0009] In a first aspect, a detector includes a detector unit. The detector unit may be configured to generate an electrical signal in response to particles incident on an active layer of the detector unit, the active layer may define an absorption surface. The detector may include a filter. The filter may include a film of carbon material. The filter may be arranged relative to the detector unit to shield the absorption surface from a subset of incident particles. The subset of incident particles may include electrons, ions, and photons. The photons may have an energy less than about 40 eV.

[0010] In some embodiments, the carbon material may include carbon nanotubes. The carbon material may include a non-woven carbon nanotube felt layer. The membrane may include a plurality of substantially planar carbon nanotube felt layers. The plurality of layers may together define a spatially varying transmittance of the filter. The filter may include a frame in which the layer is disposed. The detector may also include a plurality of frames containing the frame. The plurality of frames may be individually addressable and individually movable relative to the detector unit.

[0011] In some embodiments, the detector defines an aperture substantially parallel to the absorbing surface. The detector unit and the filter may be configured to accommodate the aperture. The detector may include segments arranged around the aperture. The filter may include one or more filter segments, which are configured to shield one or more of the segments from a subset of 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.

[0012] The detector may further comprise a shield, the shield being movable relative to the detector unit and the filter and being arranged so that the filter is located between the detector and the shield. The detector may further comprise a retaining element. The retaining element may be configured to position the detector and the filter in a vacuum chamber of a charged particle microscope and to orient the detector relative to a sample stage of the charged particle microscope so that the filter is arranged between the sample stage and the detector. The detector may comprise a silicon drift detector.

[0013] In a second aspect, a charged particle beam system includes a vacuum chamber. The charged particle system may include a charged particle beam column that is operably coupled to the vacuum chamber and configured to guide the charged particle beam into the vacuum chamber. The charged particle system may include a sample stage disposed in the vacuum chamber. The charged particle system may also include the detector of the aforementioned aspect.

[0014] In one example, the carbon material comprises carbon nanotubes. The carbon material may comprise a nonwoven carbon nanotube felt layer. The membrane may comprise a plurality of substantially planar nonwoven carbon nanotube felt layers. The plurality of layers may together define a spatially varying transmittance of the filter. The charged particle beam column may define a beam axis A. The detector may define an aperture substantially parallel to the absorbing surface and substantially aligned with the beam axis. The detector and the filter may be configured to accommodate the aperture. The detector may comprise segments arranged around the aperture. The filter may comprise one or more filter sections, the one or more filter sections being configured to shield one or more of the sections from a subset of incident particles. The system also comprises a shield, the shield being movable relative to the detector and the filter, and being configured such that the filter is located between the detector and the shield relative to the sample stage.

[0015] In a third aspect, a method for detecting x-rays includes directing a charged particle beam toward a sample in a system of the foregoing aspects. The method includes generating detector data using the detector of the foregoing aspects. Generating detector data may include applying a bias to a detector unit, such that high-energy particles incident on an active layer of the detector unit may generate a charge collected at a collector region of the detector unit. In some embodiments, the method for detecting x-rays may be encoded as machine-readable instructions stored in one or more machine-readable storage media. In this manner, the systems and detectors of the foregoing aspects may be configured to execute these instructions, thereby causing these systems and detectors to perform the operations of the method.

[0016] The terms and expressions that have been adopted are used as terms of description rather than limitation, and when such terms and expressions are used, it is not intended to exclude any equivalents of the features shown and described or portions thereof, but it should be recognized that various modifications are possible within the scope of the subject matter claimed. Therefore, it should be understood that although the subject matter claimed by the present disclosure has been specifically disclosed through embodiments and optional features, those skilled in the art may make modifications and changes to the concepts disclosed herein, and such modifications and changes are considered to be within the scope of the present disclosure as defined by the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The foregoing aspects of the present disclosure and many of the attendant advantages will become more readily appreciated when the following detailed description is taken in conjunction with the accompanying drawings.

[0018] Figure 1A is a schematic diagram illustrating an example charged particle microscope system according to some embodiments of the present disclosure.

[0019] Figure 1B is a diagram showing some embodiments according to the present disclosure Figure 1A Schematic diagram of details of an example charged-particle microscope system.

[0020] Figure 2A is a schematic diagram of an example charged particle detector according to some embodiments of the present disclosure.

[0021] Figure 2B is a schematic diagram of an example detector according to some embodiments of the present disclosure.

[0022] Figure 3A is a schematic diagram of an example detector including a silicon drift detector according to some embodiments of the present disclosure.

[0023] Figure 3B is a schematic diagram of an example detector including multiple segments arranged in quadrants according to some embodiments of the present disclosure.

[0024] Figure 3C is a schematic diagram of an example detector including a plurality of silicon drift detectors arranged in a quadrant, according to some embodiments of the present disclosure.

[0025] Figure 4 is a schematic diagram of an example filter defining spatially varying transmittance according to some embodiments of the present disclosure.

[0026] Figure 5 is a graph of example data of normalized transmittance of filters as a function of position according to some embodiments of the present disclosure.

[0027] Fig. 6A is a schematic diagram of an example filter that is movable relative to an example shield according to some embodiments of the present disclosure.

[0028] Figure 6B is a schematic diagram of an example filter that is movable relative to an example shield according to some embodiments of the present disclosure.

[0029] Figure 6C is a schematic diagram of an example filter that is movable relative to an example shield according to some embodiments of the present disclosure.

[0030] Fig.6D is a schematic diagram of an example filter cassette movable relative to an example detector unit and an example shield according to some embodiments of the present disclosure.

[0031] Figure 7 is a graph of example transmittance data for multiple particles and detectors according to some embodiments of the present disclosure.

[0032] In the drawings, unless otherwise specified, the same reference numerals represent the same components in various views. Where appropriate, not all instances of components need to be labeled to reduce clutter in the drawings. The drawings are not necessarily drawn to scale, with emphasis instead on illustrating the principles being described. DETAILED DESCRIPTION

[0033] Although illustrative embodiments have been described and described, it should be understood that various changes can be made therein without departing from the spirit and scope of the present disclosure. In the following paragraphs, embodiments of analytical instrument systems are described. In order to simplify the description, embodiments of the present disclosure focus on energy dispersive spectroscopy (EDS) implemented in scanning electron microscopes. For this reason, embodiments are not limited to such instruments, but are intended to be used for analytical instrument systems in which the analysis of characteristic x-ray signals can be limited by signal-to-noise ratio constraints or by relatively low signal limitations. In an illustrative example, the detector of the present disclosure can be more widely deployed as a part of a charged particle system, such as a transmission electron microscope, a dual-beam system, a triple-beam system, an electron beam microanalysis system, etc. Similarly, although embodiments of the present disclosure focus on x-rays generated by inner shell excitation, additional and / or alternative x-ray signals are also considered, including but not limited to continuous x-rays and / or fluorescent x-rays.

[0034] Embodiments of the present disclosure include systems, components and methods for improved x-ray detectors. In an illustrative example, the system may 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 absorption surface. The system may also include a filter including a film of a carbonaceous material, the filter being arranged relative to the detector to shield the absorption surface from a subset of incident particles, the subset including electrons, ions and photons, the photons having an energy of less than about 40 eV. The systems, components and methods of the present disclosure benefit from improved stereoscopic collection angles, higher take-off angles, thereby improving signal-to-noise characteristics, reducing collection time and reducing electron dose to preserve dose-sensitive samples. In addition, embodiments of the present disclosure exhibit improved sensitivity to relatively low-energy particles (e.g., x-rays), improved sensitivity to relatively low-intensity signals and improved robustness to degradation caused by high-energy materials.

[0035] The following detailed description focuses on embodiments of charged particle microscope systems, but it is expected that additional and / or alternative instrument systems may be improved by using 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 matter such as ions, electrons and / or photons. Without being limited to a particular physical formulation, in the context of the present disclosure, "particles" refers to species produced by such interactions, whether in large quantities or not, including but not limited to charged particles (e.g., ions and electrons) and photons (e.g., microwaves, IR, visible light, UV, x-rays, etc.).

[0036] Figure 1Ais a schematic diagram illustrating an example charged particle microscope 100 system according to some embodiments of the present disclosure. The example charged particle microscope 100 includes multiple sections, including an electron source, a beam column 105, and a vacuum chamber 110. The electron source includes a high voltage supply component, a vacuum system component, 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 an electromagnetic lens element configured to shape and form the electron beam from the electron source into a generally circular beam having a generally uniform profile transverse to the beam axis A, and to adjust the beam to be focused onto a sample 125 through an objective lens 115, as shown in reference Figure 1B Described in more detail.

[0037] Electron beams are often characterized by the beam current and the accelerating voltage applied to produce the beam, among other criteria. The range of beam current and accelerating voltage can vary between instruments and are often selected based on the material properties of the sample or the type of analysis being performed. However, typically, electron beams are characterized by energies ranging from about 0.1 keV (e.g., for an accelerating voltage of 0.1 kV) to about 50 keV and beam currents ranging from picoamperes to microamperes.

[0038] The vacuum chamber 110 and / or the beam column 105 may include multiple detectors for various signals, including but not limited to secondary electrons generated by the interaction of the electron beam with the sample, backscattered electrons (BSE), forward scattered electrons (FSE), x-ray photons (e.g., EDAX or EDS), other photons (e.g., visible light and / or IR cameras), and / or molecular species (e.g., TOF-SIMS), as described in reference Figure 1B 105. The vacuum chamber 110 may also include a sample stage 120 that may be operably 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 means of investigating and / or imaging the sample 125. The sample stage 120 may include a window that allows electrons or other charged particles to be transmitted through the sample and the sample stage. In this manner, one or more detectors of the present disclosure may be disposed in the vacuum chamber 110 and / or in 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 reference to FIG. 2A to FIG. 2B Described in more detail.

[0039] The example charged particle microscope 100 is shown as a single beam SEM instrument to focus the description on the application of the detector of the present disclosure in x-ray detection. In some embodiments, the charged particle microscope 100 may be combined with an ion beam source (e.g., a focused ion beam or FIB) suitable for, for example, modifying samples and / or for microanalysis. In this way, the detector of the present disclosure can be configured to generate detector data (e.g., images, line scans, x-ray spectra, etc.) in coordination with the ion source for modification and / or microanalysis of samples. 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 in a layer-by-layer manner. Between increments, the x-ray microanalysis of the sample 125 can provide a depth distribution of elemental information in the sample 125.

[0040] Figure 1B is a diagram showing some embodiments according to the present disclosure Figure 1A Schematic diagram of details of an example charged particle microscope system 100. Detectors include one or more in-column detectors (ID) 155, pole piece mounted detectors (PMD) 160, STEM mode detectors (SMD) 165, and other detectors, such as through-the-lens detectors (TLD) 170 and Everhart-Thornley detectors 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 a charged particle microscope that includes an x-ray source, an x-ray detector, an ion beam source, a mass spectrometer, a light source (e.g., a laser source), or other sources that may be included in a complement of analytical instruments that may be used for SEM microanalysis. As described in reference Figures 2A to 3C Described in more detail, at least some of the detectors of the example microscope 100 can be paired with a filter 140 that is proximate to or covers an absorptive surface of the detector.

[0041] The detector 160 with the pole piece mounted thereon can be mechanically coupled to the pole piece 117 housing the objective lens 115 and oriented so that the collector surface faces the sample stage 120. Figures 2A to 3C As described in more detail, PMD 160 may be segmented into multiple detectors, such as dipoles, tripoles, quadrupoles, octopoles, or other configurations (e.g., combinations of quadrants and other configurations). PMD 160 may be mounted on retractable supports 195 rather than being mechanically coupled to pole piece 117. Advantageously, mounting PMD 160 on retractable supports 195 allows PMD 160 to be removed from between sample stage 120 and pole piece 117, thereby allowing other probes, sources, or components to be introduced into the same space (e.g., parabolic reflectors for luminescence measurement / imaging).

[0042] 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 located 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 so that the absorption surface faces the underside of the sample stage 120. In this way, x-rays 181 emitted from the sample 125 (e.g., from a region of the interaction volume of the sample in which the x-rays are generated) can reach the detector surface and generate a characteristic signal for imaging and / or microanalysis. The x-rays 181 can include x-rays generated from inner shell excitations in atoms of the sample 125, which are directed through the sample rather than back toward the beam column 105. For the SMD 165, a filter 140 can be disposed between the detector 165 and the sample 125 so that charged particles and relatively low energy photons can be absorbed to selectively detect the x-rays 181.

[0043] The filter 140 may be movable relative to the detector unit, as shown in FIG. FIG. 2A to FIG. 6D Detailed description. By placing the filter 140 between the absorptive surface of the detector unit and the sample, the detector can generate x-ray data with negligible or no signal attributable to charged particles and relatively low energy photons (e.g., infrared photons, visible photons, and / or ultraviolet photons). In this way, embodiments of the present disclosure provide improved stereoscopic collection angles and improved take-off angles relative to conventional x-ray detectors 130, resulting in improved accumulation time, signal-to-noise properties, and reduced exposure of sensitive samples to charged particle doses.

[0044] The x-ray detector 130 includes a detector 131 that is shielded from charged particles, photons, and other noise sources by a window 133 and a collimator 135, the overall result of which is a significant reduction in the stereoscopic collection angle. In addition, to protect the window material and / or reduce the interaction between the magnetic components of the x-ray detector 130 and the charged particle beam, the x-ray detector 130 may be limited to a relatively low take-off angle, e.g., about 30 degrees to about 50 degrees measured from a plane defined by the sample surface 125. The take-off angle may be increased by tilting the sample 125 at the expense of reduced functionality of the detectors 155, 160, 165, and 170 during x-ray collection.

[0045] Figure 2A is a schematic diagram of an example particle detector 200 according to some embodiments of the present disclosure. The example detector 200 is a reference Figure 1BExamples of detectors are depicted, such as ID 155, PMD 160, and / or SMD 165. Thus, example detector 200 includes a holding element 205, a detector unit 207, and a filter 210. Detector unit 207 includes a receptor layer 215, a first conductive layer 220, and a second conductive layer 225.

[0046] The retaining element 205 may be configured to be incorporated into a scanning electron microscope (SEM), as shown in FIG. Figure 1A to Figure 1B described in more detail. The retaining element 205 may include mechanical accessories, connectors, and / or features corresponding to a given SEM system. For example, in the PMD 160, the retaining element 205 may include one or more through holes disposed in the housing corresponding to the locations of threaded bores in the pole piece 117, thereby facilitating mechanical coupling of the retaining element 205 to the pole piece 117. The pole piece 117 may be configured differently in 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 into which the retaining element 205 is to be incorporated. Similarly, the retaining element 205 may be configured to engage with a support member (e.g., Figure 1B The retractable support member 195) is mechanically coupled. Fig. 6A Described in more detail, the support may be a retractable arm that allows the example detector 200 to be oriented toward a sample and / or beam target (eg, sample 125 of FIG. 1 ). In this manner, the holding element 205 may be tilted and / or linearly translated.

[0047] The detector unit 207 can be mechanically coupled to the retaining element 205, for example, by an adhesive, a retaining clip, a tensioner, a screw, etc. The receptor layer 215 can define a first surface 217 and a second surface 219. The second surface 219 is shown as being opposite to the first surface 217, but can also be a different configuration. The first conductive layer 220 can be configured to cover the first surface 217. The second conductive layer 225 can be configured to cover the second surface 219. In some embodiments, the first conductive layer 220 and / or the second conductive layer 225 can be or include a metallic transparent conductive material, a conductive carbon film, and / or other conductive materials compatible with chemical vapor deposition, physical vapor deposition, epitaxy, or other techniques for depositing conductive materials with controlled purity and thickness on the order of tens of nanometers to hundreds of nanometers. To this end, the first conductive layer 220 can be characterized by a substantially uniform thickness below the threshold at which the conductive material interferes with the incident particles (e.g., limited by and within the tolerances of the manufacturing method). The first conductive layer 220 can be disposed on the receptor layer as a patterned film or patterned layer (e.g., in the shape of a grid or other geometric configuration) to distribute the electrostatic field over the surface. In this case, the first surface 217 will not be covered by the material 220 in the mesh of the grid, which can improve the detection of some incoming particles.

[0048] The receptor layer 215 is 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 interpolated values ​​thereof. Figure 1B As described in more detail, spatial constraints in the region between the sample stage 120 and the pole piece 117 discourage larger values ​​for the 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 receptor layer 215. Conversely, smaller values ​​for the thickness 230 may increase the likelihood that particles incident on the first surface 217 of the receptor layer 215 will pass through the receptor layer 215 without generating a detectable signal or will reduce detector efficiency at higher particle energies.

[0049] In some embodiments, the detector unit 207 and / or the retaining element 205 define an aperture 235. The aperture may be included in the example detector 200 to allow the electron beam (e.g., Figure 1B The electron beam 190) passes through the retaining element 205 and / or the detector unit 207. Although the nominal diameter of the electron beam can be on the order of tens of nanometers, electromagnetic interactions between the detector unit 207 and the electron beam can 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 blocks or interferes with the detector unit 207). For at least these reasons, the aperture 235 can be characterized by a diameter 240 of about 0.1 mm to about 10 mm (including subranges, fractions, and interpolated values ​​thereof). For example, the diameter 240 may 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 interpolated values ​​thereof.

[0050] As reference Figure 1B In more detail, the particle of interest (e.g., Figure 1B The angular distribution of x-rays 181) relative to the surface of the sample 125 can be used 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, so that generally for smaller values ​​of the diameter 240, the detector performance improves. Conversely, interactions between the detector 200 and the electron beam 190 can impair the function of the charged particle microscope system and / or the detector 200. In this way, the diameter 240 can 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 to reduce the diameter 240.

[0051] In some embodiments, a conductive film 245 (e.g., gold, aluminum, etc.) may be provided to cover the inner surface of the hole. The conductive film 245 may be electrically coupled to the first conductive layer 220 or the second conductive layer 225, or may be electrically isolated from both the first conductive layer 220 and the second conductive layer 225. The conductive film 245 may be included as part of incorporating the example detector 200 into the beam column 105, for example by shielding the acceptor layer from the primary electrons, the secondary electrons 185, etc.

[0052] The detector unit 207 can be shaped to accommodate the aperture 235. In this case, accommodating the aperture 230 means that the aperture 235 extends through the detector unit 207 and penetrates the first conductive layer 220, the receptor layer 215, and the second conductive layer 225, so that the beam axis passes through the aperture 235, wherein the first conductive layer 220 is oriented toward the sample stage 120 to serve as an absorption surface, as shown in reference Figure 1B For example, a charged particle detector 200 configured as a PMD 160 may include an aperture 235, wherein the detector unit 207 is shaped to accommodate the aperture 235. Conversely, in a configuration where the signal of interest emanates from the sample 125 at an angle between the beam axis A and the sample surface, the aperture 235 may be formed in the holding element 205 rather than in the detector unit 207.

[0053] The example detector 200 is shown in a toroidal form factor. Embodiments of the present disclosure include additional and / or alternative form factors, including but not limited to rectangular form factors or other polygonal form factors. Similarly, Figure 2A The schematic diagram of is not intended to limit the geometric arrangement of the components of the example detector 200. The example detector 200 is shown in a concentric configuration, wherein the aperture 235 is substantially located at the center of the detector unit 207. However, in some embodiments, the aperture 235 can be offset relative to the geometric center of the detector unit 207, for example, where the detector unit 207 is shaped to collect particles emitted from a specific angle relative to the beam axis A and / or across an angular range that is not rotationally symmetric about the beam axis A.

[0054] Figure 2B 2 is a schematic diagram of an example detector 250 according to some embodiments of the present disclosure. The example detector 250 includes a detector unit 207 having a receptor layer 215, a first conductive layer 220, and a second conductive layer 225, the detector unit being mechanically coupled to a holding element 205, as shown in reference Figure 2A The example detector 250 includes a first contact 255 , a second contact 260 , a bias circuit 265 , and a current measurement circuit 270 .

[0055] 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 example detector 250 can be configured to apply a bias voltage across the receptor layer 215. For example, the bias circuit 265 can be configured to apply a bias voltage having a magnitude of about .1V to about 5kV (including subranges, fractions, and interpolated values ​​thereof) across the receptor layer 215. A larger magnitude 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 partial discharge or by deflecting and / or deforming the primary electron beam 190). Conversely, a smaller magnitude bias voltage can impair the performance of the charged particle detector of the present disclosure (e.g., by favoring electron-hole recombination).

[0056] Without being limited to a particular physical mechanism or phenomenon, the particle detectors of the present disclosure may be configured to respond to energetic particles 275 (e.g., Figure 1A The x-ray 181) is incident on the absorption surface 217 of the acceptor layer 215 (for example, by the orientation of the first conductive layer 220 toward the sample stage 120) to generate an electrical signal. The penetration of the high-energy particles 275 into the acceptor layer can generate electron-hole pairs, which can be separated and driven to the corresponding conductive layer by the force of the bias voltage. The current measurement circuit 270 can be configured to integrate the current drawn from the acceptor layer 215 and / or returned to ground or relative to ground over a period of time (for example, coordinated with the scanning pattern of the SEM as part of imaging or for a defined exposure time for point mode analysis). The magnitude of the bias voltage can be based at least in part on the thickness 230 of the acceptor layer 215 as a method of improving the efficiency of the detector (for example, by reducing the probability of electron-hole recombination in the acceptor layer 215).

[0057] The filter 210 may include a film 211. The film 211 may include a material that exhibits selective transmittance to x-rays 275. Selective transmittance means that the film 211 allows 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 relatively low energy photons 277 and charged particles 279 (e.g., electrons, ions, etc.)). The film 211 material can block all or substantially all photons 277 and charged particles 279 below a corresponding threshold energy. For example, the film 211 can absorb, reflect, or otherwise block substantially all electrons having an energy of about 7.8 keV or less, as shown in reference Figure 7In 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 a parameter. For example, a filter having a thickness of about 2 μm can block incident electrons having energies below about 2.5 keV. Below 7.8 keV, the thickness dependence of the filter performance allows for adjustment of operating conditions, as described in reference to Figures 4 to 7 described in more detail. In addition, the threshold energy may depend at least in part on the composition of the film 211. For example, relative to the film 211 including single-walled carbon nanotubes, the film 211 including multi-walled carbon nanotubes is characterized by a higher threshold energy. Similarly, a film 211 having a relatively high nanotube density per unit surface area may be characterized by a higher threshold energy than a film 211 having a relatively low nanotube density per unit surface area. In an exemplary embodiment, the surface density is defined as the mass of the film 211 material per unit surface area (e.g., square centimeters). The properties of the film 211 can be described and / or related via the surface density, at least in part based on characteristic volume properties, including the volume density of the carbon material (e.g., mass / volume) and / or the void percentage of the film (e.g., the average proportion of empty space in the film). In some embodiments, the volume density of the carbon material is about 0.11 g / cm 3 To about 1.1g / cm 3 , including its subranges, fractions, and interpolated values. 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 of about 3.5% at 550 nm, 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, the thickness and transparency of the film may correspond to the areal density. For example, the areal density may be about 0.1 μg / cm 2 To about 330mg / cm 2 , including its subranges, fractions, and interpolated values, allows the size, number of layers, and individual layer thickness of film 211 to be determined based at least in part on a balance between transparency and size / spatial constraints.

[0058] In some embodiments, the membrane 211 includes a carbonaceous material 213. The carbonaceous material 213 may include a carbon nanotube material. The carbon nanotube material may include single-walled nanotubes, double-walled nanotubes, multi-walled nanotubes, and / or mixtures thereof. The carbonaceous material 213 may include carbon nanofibers, nanobamboo, other forms of sp 2 Hybridized carbon, sp 3Hybridized carbon and / or their mixtures (e.g., a combination of graphite and amorphous carbon). Nanotubes, nanobamboos and / or nanofibers can be oriented along one or more in-plane directions and / or can be randomly oriented. For example, film 211 can include layers in which the carbon nanotubes constituting the carbon nanotube felt are substantially aligned with the orientation direction. Different layers can be oriented in the same direction or in different directions. Although substantially aligned with the orientation direction on a given layer and / or film 211, a single nanotube, nanofiber, etc. can exhibit tortuosity (e.g., bending, angled / kinked, looped and / or spirally twisted segments) so that a given nanotube, nanofiber, etc. segment can be oriented away from the orientation direction. Film 211 can also include metals, ceramics and / or nitride materials, for example, as coatings, inclusions or other forms that do not substantially limit the transmittance of filter 210. Film 211 can be electrically coupled to a potential (e.g., ground potential, positive bias, negative bias). Advantageously, electrically grounding membrane 211 can improve absorption and / or neutralization of 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 microscopy system in which the example detector 250 is disposed.

[0059] The film 211 may have a thickness of the order of about 10 nm to about 10 μm (e.g., about 10 nm to about 99 μm), including its sub-ranges (e.g., about 0.5 μm to about 30 μm), fractions, and interpolations. The film 211 may include a plurality of carbon nanotube material layers from about 3 nm thick to about 1 μm thick, individually including its sub-ranges, fractions, and interpolations. In one example, each layer may have a thickness of about 0.4 μm, so that a film having two carbon nanotube material layers may be about 8 μm thick, and a film having 25 carbon nanotube material layers may be about 10 μm thick. Without being limited to a particular physical phenomenon or mechanism, the filter 210 may have a thickness-dependent transmittance based at least in part on the absorbance of each constituent layer. In this way, the film 211 may include many layers that allow the filter 210 to absorb substantially all incident photons 277 and / or charged particles 279 while allowing transmission of a significant portion of the x-rays 275.

[0060] Each layer may have a photon absorptivity of about 1% to about 90% (e.g., as measured at 525 nm). In the example of 25 layers of carbon nanotube material, where each layer has an absorptivity of about 40% at 525 nm, the total absorption factor of film 211 for photons at 525 nm may be about 1×10 -9 In an example with a film 211 having a thickness of about 2 μm, the transmission of Li Kα (55 eV) x-rays 275 may be about 23%, corresponding to a relative transmittance of 23% relative to current detectors (e.g., reference Figure 7In addition, comparative example detectors of the prior art that include carbon materials as part of the window layer typically include a support grid that introduces artifacts and an opaque aluminum coating on at least one surface of the window layer, which further reduces the quantum efficiency of the detector. In contrast, the detectors of the present disclosure may include a frame (e.g., Figure 3A A frame 315) surrounds at least a portion of the membrane 211 to hold at least a partially unsupported membrane 211.

[0061] Like example detector 200, example detector 250 may be configured to be incorporated into Figure 1A to Figure 1B In addition, components and / or materials of the example detector 250 may be included as part of the example detector 200, from Figure 2A and the accompanying description thereof are omitted to focus on geometric aspects. To this end, a Figure 2B 2. In the illustrative example, example detector 250 may include aperture 235 of example detector 200. Similarly, example detector 200 may include the electronic components and materials of detector 250.

[0062] Figure 3A 3 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 also includes a filter 310 and an electronic circuit 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 the surface of the detector 330 such that an active layer (e.g., Figure 2A The charges generated within the active layer 215 are pulled toward the central anode region 345 of the detector unit 305.

[0063] The filter 310 includes a membrane 311 in a frame 315. The frame is coupled to a holding arm 320 by which the filter 310 can be positioned relative to the detector unit 305. In some embodiments, the filter 310 is movable relative to the detector unit 305. As shown, the filter 310 is located 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.

[0064] The membrane 311 includes a plurality of layers 313 of filter material, as shown in FIG. Figure 2BFrame 315 may be coupled to membrane 311 over at least a portion of the perimeter of membrane 311. In this manner, frame 315 mechanically supports membrane 311, thereby allowing membrane 311 to exist substantially free-standing over the region of filter 310 corresponding to detector 305.

[0065] Figure 3B 3 is a schematic diagram of an example detector 330 including a plurality of filter segments 355 arranged in a quadrant 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 apertures 370 (e.g., Figure 2A The segments 355 may be formed of a plurality of membranes 311. The segments may have similar or different properties, such as thickness, transmittance, etc. Advantageously, different segments may allow different detector segments to interrogate different energy ranges, for example, by focusing x-rays at a given energy of interest for a given sample (e.g., Figure 1B Different absorption coefficients are applied to the x-rays 181).

[0066] Figure 3C A portion of an example detector module 330 is shown obscured by a filter 310 that includes a detector surface having a plurality of silicon drift detectors 305 arranged in a quadrant, according to some embodiments of the present disclosure. The example detector module 330 can accommodate a central aperture 370 by including a plurality of silicon drift detectors 305 that are relatively small or otherwise shaped to be disposed in an arrangement about the central aperture 370 to optimize collection efficiency, among other things. The number and arrangement of the 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.

[0067] In some embodiments, one or more charged particle detectors 360 may be included in the silicon drift detector 305. Advantageously, the filter 310 may be at least partially absent near the charged particle detector 360, for example by forming holes in the membrane 311 and / or by omitting one or more segments 355 from the filter 310. In this manner, the example detector module 330 may simultaneously generate a multi-modal detector data set including x-ray data (e.g., EDS data) and electronic data (e.g., BSE data, SE data, etc.). As part of the imaging / mapping process, such data of different modalities may be stored separately and associated as part of a data cube, for example, with reference to a location on a sample surface.

[0068] Figure 44 is a schematic diagram of an example filter 400 that defines a spatially varying transmission coefficient or transmittance according to some embodiments of the present disclosure. The example filter 400 includes a plurality of layers 405 of filter material. The layers 405 are coupled to a frame 410. As shown in reference Figure 3A As described in more detail, the layer 405 and the frame 410 can be configured such that the filter is positioned relative to the x-ray detector to place the absorbing surface (e.g., Figure 2A The first surface 217) is shielded from incident particles including electrons, ions, relatively low energy photons, etc.

[0069] As reference Figures 2B to 3A Described in detail, layer 405 may include carbon nanotube material. For example, the carbon nanotube material may include multi-walled carbon nanotubes. In addition, the carbon nanotube material may be formed in a non-woven felt. In some embodiments, the example filter 400 is configured so that the layers 405 differ from each other in one or more properties and / or parameters so that the example filter 400 exhibits a spatially varying transmittance. In one example, the transmittance variation may be the result of physically modifying the filter by a directed energy tool (e.g., via a laser, electron beam, ion beam, etc.). In this way, the total thickness of the filter can vary spatially. Spatial variation can be achieved by including layers 405 having different lateral and / or thickness dimensions. In Figure 4 In the example shown, the example 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. When reproduced by multiple layers 405 of the example filter 400, the result is a substantially linear (e.g., step) dependence of transmittance on lateral position in the example filter 400, as shown in reference Figure 5 In addition to or alternatively to truncating layer 405, similar results can be achieved by spatially thinning layer 405. For example, at different lateral locations in first layer 405-1, first layer 405-1 can be relatively thinner and / or relatively thicker than second layer 405-2. In this way, example filter 400 can define arbitrary spatial transmittance variations (e.g., Figure 5 Gaussian shape shown).

[0070] The example 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 example filter 400 also includes various features 415. The features 415 can include vias, slits, holes, and / or other patterns transferred to and / or into the one or more layers 405 by removing and / or depositing material. The features 415 can be at least partially aligned, such as concentric arrangements of holes that together define a Gaussian transmittance profile. As described in reference Figure 3CDescribed in more detail, feature 415 may include an aperture that is substantially aligned with charged particle detector 360, thereby allowing the detector of the present disclosure to simultaneously generate x-ray and electron microscopy (eg, electron image) data.

[0071] In some embodiments, layer 405 is coupled to frame 410 on a single side, but may also be coupled to frame 410 on multiple sides, such as Figure 3A In some embodiments, each layer 405 is held in a corresponding frame 410, so that the filter 400 includes multiple frames. FIG. 6A to FIG. 6C As described in more detail, such a configuration can allow the filter 400 and / or individual filter layers 405 to be addressable and / or movable, thereby allowing the transmittance of the filter 400 to be dynamic. Advantageously, dynamically changing the transmittance of the filter allows the properties of the filter to be tuned to a given sample (e.g., Figure 1A In the illustrative example, a sample that emits a relatively high proportion of backscattered electrons (e.g., relatively heavy elements) can benefit from a relatively lower total transmittance achieved by including more layers 405, while a sample that emits a relatively low proportion of x-rays can benefit from a relatively higher transmittance achieved by removing one or more layers 405. In this way, a single filter 400 can provide a range of transmittance values.

[0072] Figure 5 is a graph of example data of normalized transmittance as a function of position for filters according to some embodiments of the present disclosure. The graph includes simulated data of transmittance varying over position for a given energy, the simulated data being normalized to a maximum value at a given position. The distribution may be obtained by a filter (e.g., Figure 4 The spatial modification of layer 405) is generated, as shown in reference Figure 4 The position-varying transmittance may exhibit a "staircase" distribution 505 corresponding to a series of truncated layers. In the case where the layer is patterned by local removal of material (e.g., by ion milling of a filter material (e.g., carbon nanotube felt)), the transmittance may exhibit a smooth distribution 510 with positions based at least in part on the degree of local removal. As described in reference Figure 4 As described, the transmittance may follow a nonlinear function centered about the central position, such as a Gaussian 515 distribution.

[0073] Fig. 6A 6 is a schematic diagram of an example filter 610 that is movable relative to an example shield 615 according to some embodiments of the present disclosure. The filter 610 includes a plurality of membrane 605 material layers and a retaining member 611, as shown in reference Figures 2A to 5 The retaining member (e.g., Figure 3AThe frame 315 and support 320 of the detector unit may be capable of moving relative to the shield 615 so that the shield 615 and / or the filter 610 can be moved relative to the detector unit (e.g., Figure 2A The detector unit 207) moves.

[0074] The shield 615 may be or include a material that is opaque to a variety of incident particles, such as x-rays 620, other photons 625, electrons 630, and / or ions 635. The shield 615 may include a conductive material (e.g., a metal, etc.) that allows the shield to absorb, reflect, or otherwise block particles through a combination of physical and dimensional properties. Advantageously, the shield 615 allows the filter 610 and / or detector to be protected from destructive particles. In an illustrative example where the detector is disposed in a dual beam system, during operation of a focused ion beam that produces a relatively high ion flux, the shield may be moved into position, or the filter and / or detector may be moved behind the shield, where the relatively high ion flux would otherwise damage the filter and / or detector.

[0075] Figure 6B 315 shows how an example filter 610 that is movable relative to an example shield 315 can also facilitate modifiable transmittance. Figure 6B In the embodiment shown, the box of filter 610 elements is protected by shield 615 when retracted and can be rotated into position over the detector when in use. The transmittance is in turn proportional to the number of filter 610 elements in position. The rotational motion is Figure 6C , showing rotational movement of a plurality of filter elements 610. In some embodiments, the movement is linear, rather than rotational, where the filter 610 elements are retracted behind the shield 615 via linear translation. The shield 615 may be able to move relative to the filter 610 elements and / or the detector. For example, when performing a process that creates a destructive environment for the detector (e.g., ion beam milling of a sample that produces a large amount of ion and electron flux), the shield may be moved to a position that protects the filter 610 elements and the detector.

[0076] Fig.6D 6 is a schematic diagram of an example filter box 640 that can be moved relative to an example detector unit 305 and an example shield 615 according to some embodiments of the present disclosure. The example filter box 640 represents an alternative embodiment in which the membrane material 605 is held in a frame that includes multiple filter 610 elements. Different filter 610 elements can have different transmittance properties. For example, at a given energy, a first filter element 610-1 may have a relatively higher transmittance than a second filter element 610-2 in the box 640. In this way, by moving the box 640 relative to the detector unit 305, a given energy can be selected by suppressing lower energy background signals.

[0077] Figure 7 is a graph of example transmittance data for various types of detectable signals according to some embodiments of the present disclosure. Figure 7 The graphs in provide experimental data demonstrating the improved performance of the detectors of the present disclosure relative to detectors that include beryllium filters. The detectors of the present disclosure exhibit improved x-ray transmittance relative to beryllium windows, and reduced electron transmittance and reduced artifact content relative to polymer or silicon nitride windows. For example, polymer and silicon nitride windows are often supported by grids or other structures to structurally enhance the windows. These structures reduce the quantum efficiency of the detector and may introduce artifacts attributable to the materials from which the structures are made.

[0078] In the graph, the abscissa and ordinate plot the transmittance of the filter to x-rays (dashed line) and to electrons (solid line) versus energy in electron volts. Transmittance data for the disclosed filter are provided as open circles (○) for x-ray data and open squares (□) for electron data. The dot-dash line (-●-) provides a simulated x-ray transmittance curve for the disclosed filter, while the dashed line (---) provides a conventional x-ray detector with a pure beryllium window (e.g., Figure 1A to Figure 1B 130).

[0079] Figure 7 The data in show that the detectors of the present disclosure exhibit improved sensitivity to x-rays relative to beryllium filtered detectors. In addition, the detectors of the present disclosure are substantially blind to electron flux, as evidenced by the transmittance of the filters of the present disclosure being at or near 0% for electrons having energies equal to or below about 7.8 keV, corresponding to energies almost two orders of magnitude greater than Mo Lα x-rays. The detectors of the present disclosure provide improved x-ray sensitivity and electron opacity compared to typical polymer film windows.

[0080] Furthermore, the detectors of the present disclosure outperform prior art beryllium filtered detectors over a wide range of x-ray energies from about 75 eV to about 1150 eV, including many characteristic x-rays 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). Figure 7 In an illustrative example derived from data from , the detectors of the present invention exhibited about 20% to about 40% transmittance improvement for iron, nickel, and copper Lα lines relative to beryllium filtered detectors. Advantageously, the filters of the present disclosure are effective for visible and infrared photons (e.g., Figure 2BThe detector of the present disclosure can be used for the measurement of luminescent samples and / or heated samples, for which the photon noise in the detector data may be significant with current detector technology.

[0081] In the foregoing description, various embodiments have been described. For the purpose of explanation, specific configurations and details have been set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to those skilled in the art that these embodiments may be practiced without these specific details. In addition, in order not to obscure the described embodiments, well-known features may have been omitted or simplified. Although the example embodiments described herein focus on spectrometry systems, and in particular x-ray spectrometry systems, these are meant to be non-limiting exemplary embodiments. The embodiments of the present disclosure are not limited to such embodiments, but are intended to address analytical instrument systems in which a wide array of material samples can be analyzed to determine chemical, elemental, physical, structural or other properties, as well as other aspects, including but not limited to chemical structure, trace element composition, and the like.

[0082] Some embodiments of the present disclosure include a system having one or more data processors and / or logic circuits. In some embodiments, the system includes a non-transitory machine-readable storage medium containing instructions, which, when executed on one or more data processors and / or logic circuits, cause one or more data processors and / or logic circuits to perform part or all of one or more methods disclosed herein and / or part or all of one or more processes and workflows. Some embodiments of the present disclosure include a computer program product tangibly embodied in a non-transitory machine-readable storage medium, the computer program product including instructions, which are configured to cause one or more data processors and / or logic circuits to perform part or all of one or more methods disclosed herein and / or part or all of one or more processes.

[0083] The terms and expressions employed herein are used as terms of description rather than limitation, and when such terms and expressions are used, it is not intended to exclude any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the claims. Therefore, it should be understood that while the present disclosure includes specific embodiments and optional features, modifications and changes to the concepts disclosed herein may be made by those skilled in the art, and such modifications and changes are deemed to be within the scope of the appended claims.

[0084] When a term is used without explicit definition, it is understood that unless the term has a special and / or particular meaning in the field of charged particle microscopy systems or other related fields, the term refers to the ordinary meaning of the word. The term "about" or "substantially" is used to indicate a deviation from the stated property, wherein the deviation has little or no effect on the corresponding function, property or attribute of the described structure. In the illustrated example where one 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 be unequal within permissible limits (such as manufacturing tolerances or confidence intervals inherent to system operation). Similarly, where a geometric parameter (such as alignment or angular orientation) is described as "approximately" perpendicular, "substantially" perpendicular, or "substantially" parallel, the term "about" or "substantially" is intended to reflect that the alignment or angular orientation may differ from the precisely stated condition (e.g., not precisely perpendicular) within permissible limits. For dimensional values ​​(such as diameter, length, width, etc.), the term "about" may be understood to describe a deviation of up to ±10% from the stated value. For example, a size of "about 10 mm" may describe a size from 9 mm to 11 mm.

[0085] This description provides exemplary embodiments, and is not intended to limit the scope, applicability or configuration of the present disclosure. On the contrary, the subsequent description of the exemplary embodiments will provide enabling descriptions for realizing various embodiments to those skilled in the art. It should be understood that, without departing from the spirit and scope set forth in the appended claims, various changes may be made to the functions and arrangements of the elements. Specific details are given in the description to provide a thorough understanding of the embodiments. However, it should be understood that the embodiments may be put into practice without these specific details. For example, the specific system components, systems, processes and other elements of the present disclosure may be shown in schematic form, or omitted from the diagram, so as to avoid obscuring the embodiments due to unnecessary details. In other cases, well-known circuits, processes, components, structures and / or technologies may be shown without unnecessary details.

Claims

1. A detector, comprising: a detector cell configured to generate an electrical signal in response to particles incident on an active layer of the detector cell, the active layer defining an absorptive surface; and A filter comprising a film of carbon material, the filter being disposed relative to the detector unit to shield the absorbing surface from a subset of the incident particles, the subset comprising electrons, ions, and photons having an energy 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 non-woven carbon nanotube felt layer.

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

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

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

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

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

9. A detector according to claim 8, wherein the detector comprises segments arranged around the hole, and wherein the filter comprises one or more filter segments, and the one or more filter segments are configured to shield one or more of the segments from the subset of incident particles.

10. The detector of claim 1, further comprising a shield movable relative to the detector unit and the filter and arranged such that the filter is located between the detector and the shield.

11. The detector according to claim 1 further comprises a holding element, wherein the holding element is configured to place the detector and the filter in a vacuum chamber of a charged particle microscope, and to orient the detector relative to a sample stage of the charged particle microscope so that the filter is placed between the sample stage and the detector.

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

13. A charged particle beam system, comprising: Vacuum chamber; a charged particle beam column operably coupled to the vacuum chamber and configured to direct a charged particle beam into the vacuum chamber; A sample stage, wherein the sample stage is disposed in the vacuum chamber; and A detector, the detector comprising: a detector configured to generate an electrical signal in response to a particle incident on an active layer of the detector, the active layer defining an absorptive surface oriented toward the sample stage; and A filter comprising a film of carbon material is disposed between the sample stage and the detector to shield the absorbing surface from a subset of the incident particles, the subset comprising electrons, ions, and photons having an energy less than about 40 eV.

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 non-woven carbon nanotube felt layer.

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

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

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

19. A system according to claim 18, wherein the detector includes segments arranged around the hole, and wherein the filter includes one or more filter segments, and the one or more filter segments are configured to shield one or more of the segments from the subset of incident particles.

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

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