In-column particle filter

Abstract

Systems, components, and methods for protecting charged particle detectors from damage. [Solution] The filter may include a carbon material frame and a film. The film can define a first surface, a second surface opposite the first surface, and an aperture extending through the film from the first surface to the second surface. The frame may be configured to be coupled with a charged particle detector disposed in a charged particle beam column, the charged particle detector defining an absorbing surface oriented toward the first surface. The filter may be configured to shield the absorbing surface from particles incident on the second surface. The particles may include electrons, ions, or photons.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to charged particle beam systems, as well as algorithms and methods for their operation. In particular, some embodiments relate to techniques for shielding a solid detector from high-energy particles.

Background Art

[0002] In a charged particle microscope, a conventional charged particle detector is constructed around a detector cell. The detector cell absorbs incident charged particles of a given energy and generates proportional charges that are detected as an electric current. Conventional detectors are sensitive to various types of incident particles. Ions, electrons, ultraviolet, visible and / or infrared spectrum photons, and other forms of radiation can generate electron-hole pairs that produce a detector current signal. It is difficult to achieve specificity for a particular type of charged particle (ions, electrons, photons, etc.), which can lead to a significant noise content in the detector data and potentially degrade the performance of the detector. For example, specificity may depend on selecting a filter material that is robust (e.g., does not degrade under operating conditions) and does not introduce artifacts into the detector data.

[0003] Focused-ion beam (FIB) and dual-beam (FIB and EM) systems present significant challenges with respect to detector protection techniques. For example, exposure to sputtered material removed from a sample undergoing FIB processing can increase the dark current of a solid detector, for example, by creating a conductive layer on top. In another example, sputtered material and FIB ions can be implanted into the material of a solid detector, impairing the charge collection efficiency of the detector. In a third example, a thin layer of sputtered material can impair the quantum detection efficiency of a solid detector.

[0004] As a result of the engineering constraints described above, solid-state detectors are typically unsuitable for operating conditions and / or systems that would result in significant sputtered material deposition on the detector surface, at least partially based on their sensitivity to noise generated by irrelevant signals and their sensitivity to degradation by energy species. Therefore, improved solid-state detector systems and charged particle filtration are required. [Overview of the Initiative]

[0005] The terms and expressions used herein are for illustrative purposes only and are not intended to exclude any equivalents of the illustrated and described features or parts thereof, although it should be recognized that various modifications are possible within the scope of the claimed subject matter. Therefore, although the claimed subject matter is specifically disclosed by embodiments and optional features, modifications and variations of the concepts disclosed herein can be made by those skilled in the art, and such modifications and variations should be understood to be within the scope of this disclosure as defined in the appended claims.

[0006] In a first embodiment, the filter is described with reference to Figures 1 to 10B. The filter may include a frame and a film of carbon material coupled to the frame. The film may define a first surface, a second surface opposite the first surface, and an aperture extending through the film from the first surface to the second surface. The frame may be configured to be coupled to a charged particle detector disposed in a charged particle beam column. The charged particle detector may define an absorbing surface oriented toward the first surface. The filter may be configured to shield the absorbing surface from particles incident on the second surface. The particles may include electrons, ions, or photons.

[0007] In some embodiments, the carbon material comprises carbon nanotubes. The carbon material may include a layer of nonwoven carbon nanotube felt. The film may include a plurality of substantially planar layers of the carbon material. The film may be supported by a support material on at least a portion of the film.

[0008] In some embodiments, the charged particle detector is disposed within the pole piece of the charged particle beam column. The charged particle detector may be a mirror detector including a mirror electrode. The frame may be configured to be coupled with the mirror detector. The mirror electrode may have a first end and a second end defined, with the first end being near the absorption surface. The frame may be configured to be disposed near the second end of the mirror electrode and outside the mirror detector. The mirror electrode may have a first end and a second end defined, with the first end being near the absorption surface. The frame may be configured in the pole piece to be disposed near the first end of the mirror electrode and inside the mirror detector. The charged particle detector and the mirror electrode may be arranged along the beam axis, and the frame may be arranged on the beam axis between the charged particle detector and the mirror electrode.

[0009] In some embodiments, the frame is offset from the absorption surface. The frame may include a conductive portion. The conductive portion can be electrically coupled to a voltage source via a film and a bias circuit.

[0010] In a second embodiment described with reference to Figures 1 to 10B, the charged particle beam system includes a chamber configured to receive a sample and maintain a controlled environment in the vicinity of the sample. The system may include a charged particle beam column coupled to the chamber and oriented toward the vicinity of the sample. The system may include a charged particle detector disposed on the charged particle beam column, wherein the charged particle detector defines an absorption surface. The system may include a particle filter according to one or more embodiments of the first embodiment.

[0011] In some embodiments, the charged particle beam system includes a control circuit operably coupled to a bias circuit, and one or more machine-readable media that store instructions causing the control circuit to perform an operation when read by a machine. The operation may include applying a negative bias to the film via a conductive portion, where the negative bias corresponds to a lower energy cutoff of the particle filter, below which electrons directed toward the second surface are repelled. The operation may also include applying a positive bias to the film via a conductive portion, where the positive bias is such that electrons incident on the second surface are characterized by an average energy above a threshold of the film's transmittance to electrons.

[0012] In some embodiments, the charged particle detector includes a conductive material disposed on at least a portion of the absorption surface. The charged particle detector can be electrically coupled to a voltage source via a bias circuit. The charged particle beam system can be configured to apply a bias voltage to the conductive material via a bias circuit. In some embodiments, the charged particle detector is a mirror detector including a mirror electrode, and a frame is configured to be coupled to the mirror electrode or disposed between the mirror electrode and the absorption surface.

[0013] In a third embodiment, a method for active filtering of charged particles is described with reference to Figures 10A and 10B. This method can be implemented in one or more embodiments using a charged particle beam system of the second embodiment and / or a filter of the first embodiment in one or more embodiments. This method may include applying a bias to the filter film. The bias may have a positive polarity. The bias may have a negative polarity. The bias may be applied via a conductive portion of a frame. The frame may be coupled to at least a portion of the filter film. A negative bias may correspond to a lower energy cutoff of the particle filter, below which electrons directed toward the second surface are repelled. A positive bias may increase the energy of the incident electrons so that electrons can pass through the filter film. In some embodiments, the inner surface of the filter film may be electrically insulated. Operation may include electrically grounding the inner surface.

[0014] This disclosure generally relates to the specific context of charged particle microscopy, and more specifically to electron microscopy; however, such descriptions are not intended to be limiting, and it is within the scope of this disclosure that the apparatus and methods disclosed herein may be applied in any suitable context. [Brief explanation of the drawing]

[0015] The prior aspects of this disclosure and the many advantages thereto will be more readily understood by referring to the following detailed description in conjunction with the accompanying drawings.

[0016] [Figure 1] This is a schematic diagram illustrating an exemplary dual-beam system according to some embodiments of the present disclosure.

[0017] [Figure 2] Figure 1 is a schematic diagram of the details of an exemplary system according to some embodiments of the present disclosure.

[0018] [Figure 3A] An electron microscope image of a solid detector surface including an undamaged portion and a damaged portion, according to some embodiments of the present disclosure.

[0019] [Figure 3B] A plot of exemplary detector quantum efficiency data for the undamaged portion of the solid detector of FIG. 3A, according to some embodiments of the present disclosure.

[0020] [Figure 3C] A plot of exemplary detector quantum efficiency data for the damaged portion of the solid detector of FIG. 3A, according to some embodiments of the present disclosure.

[0021] [Figure 4A] A schematic diagram of an exemplary particle filter, according to some embodiments of the present disclosure.

[0022] [Figure 4B] A schematic diagram of an exemplary magnetic pole piece, according to some embodiments of the present disclosure.

[0023] [Figure 4C] A schematic diagram of an exemplary magnetic pole piece, according to some embodiments of the present disclosure.

[0024] [Figure 5] A schematic diagram of an exemplary detector, according to some embodiments of the present disclosure.

[0025] [Figure 6] A plot of exemplary transmittance data for multiple types of detectable signals, according to some embodiments of the present disclosure.

[0026] [Figure 7] A plot of exemplary detection efficiency data as a function of beam energy, according to some embodiments of the present disclosure.

[0027] [Figure 8] This is an exemplary plot of detector current data for multiple particles and a detector according to some embodiments of the present disclosure.

[0028] [Figure 9A] This is a plot of exemplary detector current data from an unfiltered solid-state detector according to some embodiments of the present disclosure.

[0029] [Figure 9B] This is a plot of exemplary detector current data from a filtered solid-state detector according to some embodiments of the present disclosure.

[0030] [Figure 9C] This is a plot of exemplary detector leakage current data for an unfiltered solid-state detector using current technology.

[0031] [Figure 10A] These are block flow diagrams illustrating exemplary processes for active filtering of charged particle signals and acceleration of negatively charged particles, respectively, according to some embodiments of the present disclosure. [Figure 10B] These are block flow diagrams illustrating exemplary processes for active filtering of charged particle signals and acceleration of negatively charged particles, respectively, according to some embodiments of the present disclosure.

[0032] In drawings, similar reference numbers refer to the same part throughout various drawings unless otherwise specified. Not all instances of an element are necessarily labeled to reduce clutter in the drawings where appropriate. Drawings are not necessarily to scale; instead, the focus is on illustrating the principles being described. [Modes for carrying out the invention]

[0033] While exemplary embodiments have been shown and described, it will be understood that various modifications are possible without departing from the spirit and scope of this disclosure. The following paragraphs describe embodiments of charged particle beam systems, components, and techniques for protecting charged detectors. For the sake of simplicity of description, embodiments of this disclosure focus on electron microscopy and microanalysis and related systems. For that purpose, embodiments are not limited to such systems, but rather are intended for charged particle beam systems for samples where conventional techniques for detecting secondary charged particles become complicated by the multiplicity of the primary charged particle beam and / or are unsuitable for approaches involving bias voltages applied to the sample surface. Similarly, embodiments of this disclosure focus on electron microscopes, particularly dual-beam systems, but additional and / or alternative systems, including but not limited to focused ion beam systems and laser ablation systems, are intended.

[0034] Embodiments of the present disclosure include systems, methods, algorithms, and non-transient media for storing machine-readable instructions for protecting a charged particle detector from damage induced by incident particles, including energetic particles and / or charged particles. In exemplary examples, a filter may include a frame and a film of carbon material coupled to the frame. The film may define a first surface, a second surface opposite the first surface, and an aperture extending through the film from the first surface to the second surface. The frame may be configured to be coupled to a charged particle detector disposed in a charged particle beam column, the charged particle detector defining an absorbing surface oriented toward the first surface. The filter may be configured to shield the absorbing surface from particles incident on the second surface. The particles may include electrons, ions, or photons.

[0035] The following detailed description focuses on embodiments of charged beam systems including a focused ion beam source, but it is intended that additional and / or alternative instrumentation systems can be improved through the use of the techniques described. Illustrative examples of instrumentation systems of the present disclosure may include laser systems configured to ablate a sample, systems configured for electron beam-induced removal of sample material, and the like. To that end, embodiments of the present disclosure can improve the performance, stability, and lifetime of particle detectors at least partially by shielding the detector surface from incident particles while also functioning as a variable energy filter and / or charged particle collector, at least in part, based on the application of a bias voltage.

[0036] Figure 1 is a schematic diagram showing an exemplary charged particle light system 100 according to several embodiments of the present disclosure. This exemplary system 100 includes an electron source 105, an electron beam column 107, an ion source 110, a focused ion beam ("FIB") column 111, a gas injection system ("GIS") 115, a chamber 120, and a sample stage 125. The electron beam column 107 is shown as a scanning electron microscope (SEM) column, so that the exemplary system 100 corresponds to a dual-beam FIB-SEM system. The electron beam column 107, the FIB column 111, and the GIS 115 are shown to be operably coupled with the chamber 120, with the electron beam column 107 defining a first beam axis A and the FIB column 111 defining a second beam axis B. Axes A and B are indicated to converge on the region of sample 130, and the GIS 115 is oriented toward the region of sample 130 and configured to guide the gas stream containing the precursor into chamber 120. While axes A and B could also be oriented toward different locations, convergence allows the SEM system to image the region of the sample being processed in the FIB.

[0037] The electron source 105 may include one or more emitters configured to generate electrons and guide those electrons into the electron beam column 107. The emitters may include thermionic emitters, Schottky emitters, field emission source emitters, or a combination thereof, and may be operably coupled to a power system configured to apply a high voltage (e.g., several kilovolts to several hundred kilovolts) to the emission region of the emitter material. For example, the electron source 105 may include a lanthanum hexaboride (LaB6) emitter crystal to which a high potential is applied to induce electron emission from the tip of the emitter crystal. In this way, an electron beam can be guided into the electron beam column.

[0038] The electron beam column 107 includes an aperture configured to shape, focus, defocus, and guide the electron beam so that the beam is focused onto the sample 130, according to an electromagnetic optical system (e.g., electrostatic lens, electromagnetic lens, monochromator, etc.) and a set of operating parameters. The operating parameters may include beam current, beam energy (e.g., volts, electron volts, etc.), magnification parameter, scanning pattern, residence time, and / or one or more pulse parameters. Thus, the exemplary system 100 can function as a SEM to image a portion of the sample 130 and / or can be used for electron beam-assisted deposition of material onto the sample 130 and / or removal of material (e.g., in conjunction with GIS 115).

[0039] In exemplary cases, the beam energy of the electron beam may be about 10 eV to about 70 keV, including its subrange, fractions, or interpolations. Beam energies below about 1 keV can correspond to reduced pattern fidelity, while beam energies above about 50 keV can reduce the secondary electron yield to a level where deposition is significantly impaired or negligible. For this purpose, precursor decomposition and deposition reactions may be mediated by secondary electrons emitted from sample 130, which are characterized by lower energies than the primary electrons of the beam (e.g., below about 50 eV). Thus, the beam energy can be selected at least in part on the secondary electron emission function of the material of sample 130, which can be at least in part dependent on the beam energy to reduce damage to the sample and / or to promote deposition for imaging purposes.

[0040] The ion source 110 may include one or more components configured to generate an ion beam and guide ions into the FIB column 111. The ions may include metal ions and / or non-metal ions (e.g., noble gases, halogens, oxygen, or nitrogen). Thus, the ion source 110 may include a plasma source (e.g., an inductively coupled plasma source) and / or a metal ion source (e.g., a liquid metal ion source). Similar to the electron beam column 107, the FIB column may include an aperture configured to shape, focus, defocus, and guide the ion beam so that the beam is focused onto the sample 130, according to an electromagnetic optics system (e.g., electrostatic lenses, electromagnetic lenses, monochromators, aberration correctors, etc.) and a set of operating parameters. The operating parameters of the FIB components of the exemplary system 100 may include beam current, beam energy (e.g., volts, electron volts, etc.), magnification parameters, scanning pattern, residence time, and / or one or more pulse parameters. Thus, the exemplary system 100 can function as a FIB used to remove a portion of the sample 130 and / or (for example, in conjunction with GIS 115) deposit material onto the sample 130.

[0041] Similar to the energies described with reference to the electron beam above, the ion beam energy can be selected (e.g., by the user, by a user-initiated algorithm, and / or automatically without user intervention) such that the beam delivers enough energy for beam-induced deposition and / or removal to occur, but the beam does not degrade the sample or degrade the precursor (e.g., as part of patterning) without forming a material layer deposited on the sample 130. In some embodiments, additional and / or alternative precursor decomposition mechanisms (e.g., surface activation and / or secondary electron re-emission) can be used as mechanisms for deposition / removal of the sample material, thereby allowing the ion beam energy to be determined at least in part on the relationship between the beam energy, the sample material properties, and the energy properties of the precursor deposition reaction mechanism. Advantageously, ion beam-induced deposition and / or removal can yield relatively higher yields compared to electron beam-induced deposition, at least in part on the combined effect of multiple energy transfer pathways.

[0042] The GIS115 includes components that enable the GIS115 to generate a gas flow containing a precursor and to guide that gas flow into a chamber. The components of the GIS115 may include a carrier gas inlet, a nozzle 119, and a conduit that fluidly couples the nozzle 119 with a precursor reservoir 117. The precursor reservoir 117 may include a substantially non-reactive vessel (e.g., a ceramic crucible, a PTFE enclosure, a non-reactive metal, or an alloy) that is at least partially exposed to the conduit. In this way, vapor generated from the precursor disposed in the precursor reservoir 117 can be guided into the chamber toward the nozzle (e.g., by a pressure-driven flow induced by a pressure gradient relative to the chamber's vacuum). In some embodiments, the GIS115 includes a carrier gas inlet fluidly coupled to the nozzle 119 via a conduit. In this way, the precursor can be entrained in the carrier gas flow and guided into the chamber toward the nozzle. Additionally, and / or alternatively, the precursor may contain a gas under standard conditions and be introduced into the GIS115 via a gas inlet provided as part of the GIS115. In some embodiments, the carrier gas is omitted, and the precursor vapor is directed toward the sample position by a pressure-driven flow induced by the expansion of the vapor within the GIS115.

[0043] In exemplary cases, the precursor may be, or may include, a material that is solid at standard temperature and pressure and at least partially evaporates or sublimes. For this purpose, GIS115 may include a heating circuit configured to be thermally coupled to the precursor reservoir and to heat the precursor to a temperature range that induces at least partial vaporization. The temperature may be selected at least in part on an estimate of the vapor pressure of the precursor, as part of controlling the composition of the gas flow entering the chamber. Such an estimate may be determined using empirically derived heuristics for a given charged particle beam system and / or can be derived using thermodynamic first principles. In some cases, the temperature and flow rate may be selected at least in part on an operating window determined from experimental calibration of a given charged particle beam system (e.g., for a given sample material and precursor material).

[0044] Chamber 120 can be configured to maintain a controlled environment in the vicinity of sample 130. For example, the environment may be a relatively low base pressure with a portion of the precursor introduced via GIS 115 and / or may include a portion of one or more other gases (e.g., in environmental microscopy).

[0045] The operation of one or more components of the exemplary system 100 can be stored in a machine-readable storage medium and / or received from an external system via wired and / or wireless communication technology (e.g., via a WiFi or Bluetooth link) and can be coordinated by a control circuit in accordance with machine-executable instructions (e.g., software, firmware, etc.). To this end, the components of the exemplary system can be automated (e.g., operating without human intervention), pseudo-automated (operating with limited human intervention for purposes such as initiating operation, analyzing and verifying output), or manually operated (e.g., when individual operations of the exemplary system 100 are performed by a human user).

[0046] In an exemplary example, the sample stage 125 can be mechanically coupled with an automatic stage control 127 that allows the sample 130 to be reversibly tilted with respect to beam axes A and B such that the surface of the sample is substantially perpendicular to a given beam axis during the operation of the corresponding charged particle beam source. In this way, the operation of a given beam source can be coordinated with the operation of the stage control unit 127. Similarly, the operation of the GIS 115 can be coordinated with the operation of the stage control 127 and a given beam source (e.g., electron beam source 105 and column 107).

[0047] Embodiments of the present disclosure may omit one or more components of the exemplary system 100. For example, one or more of the sources 105 and 110 and / or columns 107 and 111 may be omitted. In the exemplary example, the SEM system may be configured to perform the operation of the beam-guided deposition process of the present disclosure. Similarly, systems other than dual-beam FIB-SEMs (e.g., FIB systems where two or more beam axes are not convergently trained over a given region of sample 130, such as laser SEMs) may include a GIS 115 oriented to converge with the second beam axis B.

[0048] Figure 2 is a schematic diagram of details of the exemplary system 100 of Figure 1, according to several embodiments of the present disclosure. The exemplary system 200 is simplified compared to the exemplary system 100 of Figure 1. Focusing on the detector components of the SEM system, the optical system, source, vacuum system, and sample handling configuration are omitted. The exemplary system 200 includes detectors, including a pole piece 205, a FIB system 210, a mirror detector (MD) 215, an in-column detector (ICD) 220, and a backscattered electron detector (BSE) 225, and electrodes, including a mirror electrode 217 and an aspiration tube 230. The exemplary system 200 is a focused dual-beam configuration in which the electron beam system is oriented along a first axis A, and the ion beam system is oriented along a second axis B, oriented at an angle α with respect to the first axis A, so that the axes converge at the position of the sample 235. The exemplary system 200 also includes a filter 240.

[0049] As will be explained in more detail with reference to Figures 3A to 3C, charged particle beam treatment of sample 235 (e.g., by electron beam, ion beam, beam-guided chemistry, etc.) can generate secondary particles such as secondary electrons, secondary ions, ablated material, and photons. Some of the incident primary particles (e.g., electrons and / or ions of each beam) may be scattered toward the pole piece 205 and / or toward the FIB 210. In some cases, particles may enter the pole piece and collide with internal components of the pole piece 205, such as MD 215, and the detector. As will be explained in more detail with reference to Figures 9A to 9C, a filter 240 may be placed on the pole piece 205 to protect MD 215 from damage by incident particles.

[0050] The filter 240 can be positioned along the first axis A between the mirror electrode 217 and the MD215, as shown, but additionally and / or alternatively, it can be positioned between the mirror electrode 217 and the suction tube 230. For that purpose, the exemplary system 200 can include the filter 240 in additional and / or alternative locations, such as between the MD215 and the ICD220, and between the sample 235 and the BSE detector 225. As will be described in more detail with reference to Figures 4A to 5, the filter can be positioned close to the absorption surface of the MD215, coupled with the mirror electrode 217, and / or positioned outside the mirror electrode 217. Each configuration offers different advantages, as will be described below with reference to Figures 4A to 5.

[0051] Particle-induced damage, such as ion implantation into a solid-state detector, can modify the detector's band gap, reduce the detector's quantum efficiency, or increase the detector's dark current (also known as detector leakage current), as will be described in more detail with reference to Figures 8–9C. Advantageously, the filter 240 can be configured to absorb, deflect, reflect, or otherwise prevent particles from reaching one or more detectors. In this way, the filter 240 can improve the detector robustness of the system of this disclosure and can further function as an energy-selective filter for secondary electrons and / or an accelerator for secondary electrons while removing ions, as will be described in more detail with reference to Figures 10A–10B.

[0052] Figure 3A is an electron microscope image of the surface of a solid-state detector 300, including an undamaged portion 305 and a damaged portion 310, according to several embodiments of the present disclosure. The illustrated detector 300 is configured to generate a current signal from incident high-energy particles, as will be described in more detail with reference to Figures 4B and 5. In the image, the undamaged portion 305 appears bright, and the damaged portion 310 appears dark. The damaged portion 310 results from exposure to a backscattered reflected ion beam from a sample (e.g., sample 130 in Figure 1 or sample 235 in Figure 2) and sputtered material emitted from the sample. In this context, “damaged” refers to a decrease in the performance of the detector 300 resulting from incident ions and / or other high-energy particles (e.g., the deposition of energy that induces ion implantation and / or dopant transfer into the material) that affect the electronic properties of the detector 300. This can result in a reduced sensitivity of the affected portion to incident particles. This effect is shown in the data plots in Figures 3B–3C. The detector is overlaid with a grid of material that forms a substantially rectangular region 315 on the surface. In the example detector in Figure 3A, region 315 is part of a single active layer, a portion of which is damaged. However, in some embodiments, a pixelated detector can be used so that a subset of pixels within the pixelated detector can be damaged.

[0053] For that purpose, Figure 3B is a plot of exemplary detector quantum efficiency data for an undamaged portion 305 of the solid-state detector of Figure 3A, according to several embodiments of the present disclosure. The horizontal x-axis in Figure 3B represents the average beam energy in kiloelectronvolts (keV), while the vertical y-axis represents the quantum efficiency of the undamaged portion 305 of the exemplary detector 300. The plot includes data for three applied bias voltages, zero volts (long dashed line "---"), 5 volts (short dashed line "---"), and 10 volts (dotted line "---"), as will be described in more detail with reference to Figure 4B, where the bias voltage can be applied to a conductive layer on or near the absorbing surface of the detector. In the context of Figure 3B, the bias voltage can reduce the possibility of electron-hole recombination in the solid-state detector, thereby increasing the detector quantum efficiency, as shown by the trend toward higher efficiency values ​​at average beam energies above approximately 2 keV in Figure 3A.

[0054] In contrast, Figure 3C is a plot of exemplary detector quantum efficiency data for the damaged portion 310 of the solid-state detector in Figure 3A, according to several embodiments of the present disclosure. As shown in Figure 3B, the axis represents the average beam energy (X) plotted against the detector quantum efficiency (Y). However, unlike the data in Figure 3B, the effect of charged particle damage is evident in a significant decrease in efficiency over the average energy range from 0 keV to about 30 keV. For example, at about 5 keV, the quantum efficiency of the damaged detector is about half that of the undamaged detector. Similarly, at 20 keV, the quantum efficiency of the damaged detector is about half that of the undamaged detector at zero applied bias voltage, and about 25% and 16% lower at 5V and 10V applied biases, respectively.

[0055] Figure 4A is a schematic diagram of an exemplary particle filter 400 according to several embodiments of the present disclosure. The exemplary filter 400 is an example of the filter 240 described with reference to Figure 2. Thus, the exemplary filter 400 includes a retaining element 405 and a film 410. The exemplary filter 400 defines an opening 415 through the film 410, which can also be defined at least partially within and / or through the retaining element 405. The exemplary filter 400 can also include a conductive layer 420 disposed on at least a portion of the film 410. The film can define a first surface 417 and a second surface 419 opposite the first surface 417. The film 410 can also have a thickness 430 such that the film 410 also defines an inner surface 421 on which the conductive layer can be disposed at least partially. At least a portion of the film 410 can be supported by a support element 425.

[0056] The retaining element 405 can be configured to be incorporated into a scanning electron microscope (SEM), as will be described in more detail with reference to Figures 2 and 4B-5. The retaining element 405 may include mechanical fittings, couplings, and / or features corresponding to a given SEM system. For example, in a mirror detector (e.g., MD215 in Figure 2), 2) the retaining element 405 may include one or more through holes corresponding to the location of corresponding mounting points in or on the pole piece of the SEM system (e.g., pole piece 109 in Figure 1) to facilitate the mechanical coupling of the retaining element 405 within the SEM. The pole piece may be configured differently in different SEM systems. For example, some manufacturers may omit some features in favor of other features so that the configuration of the retaining element 405 can be based at least partially on a charged particle microscope in which the retaining element 405 is incorporated. Similarly, the retaining element 405 can be configured for mechanical coupling with a support, as will be described in more detail with reference to Figure 5, allowing the exemplary filter 400 to be withdrawn and / or positioned and oriented toward a sample and / or beam target (e.g., sample 130 in Figure 1). In this way, the retaining element 405 can be configured to tilt and / or translate linearly (e.g., having multiple degrees of freedom).

[0057] The film 410 can be mechanically coupled to the retaining element 405 by means of, for example, an adhesive, retaining clip, tensioner, screw, etc. The second surface 419 is shown facing the first surface 417, but can be in a different configuration. The conductive layer 420 can be disposed on top of the first surface 417 or at least a portion of the first surface 417. In some embodiments, the conductive layer 420 is or can 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 having controlled purity and thickness of about tens to hundreds of nanometers. For that purpose, the first conductive layer 420 can be characterized by a substantially uniform thickness (e.g., limited by and within tolerances of the manufacturing method) below a threshold below which the conductive material impairs the performance of the detector beneath it. The first conductive layer 420 can be disposed as a patterned film or layer (in the shape of a grid or other geometric configuration) on top of the acceptor layer, used to distribute an electrostatic field on the surface. In this case, the first surface 417 is not covered by the material of 420 in the grid mesh, which can improve the detection of some of the incident particles. In some embodiments, the film 410 is conductive (e.g., containing at least some content of conductive carbon nanotubes) so that a bias can be applied to the filter 400 (e.g., in the absence of the conductive layer 420) using conductive contact between the film 410 and the retaining element 405.

[0058] In some embodiments, the film 410 and / or retaining element 405 define an aperture 415. The aperture may be contained in an exemplary filter 400 to allow a beam of charged particles to pass through the retaining element 405 and / or film 410. The nominal diameter of the electron beam may be on the order of tens of nanometers, but the electromagnetic interaction between the film and the electron beam and the range of the scanning angle may affect the value of the diameter 440 in which the beam is affected by the presence of the filter 400 (e.g., the beam is deformed, at least partially blocked, or interferes with the film 410). For at least these reasons, the aperture 415 may feature a diameter 440 ranging from about 0.1 mm to about 10 mm, including its partial range, fractions, and interpolations. For example, the diameter can be approximately 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 2.0 mm, 3.0 mm, 4.0 mm, 5.0 mm, 6.0 mm, 7.0 mm, 8.0 mm, 9.0 mm, or 10.0 mm, including their subranges, calibration curves, fractions, and interpolations.

[0059] The angular distribution of particles relative to the sample surface (as illustrated, for example, with reference to Figures 1 and 2) can act as a constraint on the diameter 440 of the aperture 415. For example, in the case of an X-ray detector, the X-ray flux increases closer to the beam axis A, so that the performance of the filter 400 generally improves for smaller values ​​of diameter 440. In contrast, interference between the filter 400 and the electron beam can impair the function of the charged particle microscope system and / or the filter 400. Thus, the diameter 440 can be limited by a lower threshold below which the filter 400 interferes with the operation of the charged particle microscope, and by common design considerations for reducing the diameter 440.

[0060] In some embodiments, a conductive layer 420 (e.g., gold, aluminum, etc.) can be arranged in superimposed on the inner surface 421 of the aperture 415. The conductive film 420 can be electronically coupled to a bias circuit configured to apply a bias voltage (e.g., bias voltage VB shown in Figures 3A and 3B). As described with reference to Figures 10A and 10B, the bias voltage can serve to filter particles by charge and / or energy, thereby improving the performance of the detector by attracting charged particles toward the detector. For example, the bias circuit can be configured to apply a bias voltage having a magnitude of about 0V to about 5kV, including its subrange, fractions, and interpolations, across the acceptor layer film 410. The larger the magnitude of the bias voltage, the more likely the charged particle filter is to interfere with the operation of the charged particle microscope (e.g., by forming local discharges or by deflecting and / or deforming the beam of primary electrons oriented along axis A). In some embodiments, the inner surface 421 includes an isolated conductive surface such that the inner surface 421 can be electrically grounded or held at the potential of another part of the column. In this way, the lens effect of bias on the inner surface 421 can be avoided. To this end, one or more gap layers of nonconductive material can be disposed between the isolated conductive surface and the inner surface 421 (for example, a film 410 is conductive, and a short circuit between the grounded inner surface and the biased first surface is avoided).

[0061] The support element 425 can be bonded to the film 410 over at least a portion of the second surface 419. In some embodiments, the support element 425 is a grid on which the film 410 is disposed. The grid may be or include metals or other materials that can be selected for their material and / or chemical properties (e.g., suitability for charged particle microscopy and microanalysis, suitability for vacuum, tensile and other mechanical properties). The support element 425 may also be a thin foil or other form of material that, when bonded to the film 410, provides structural support to the film 410 or otherwise improves the performance of the film 410 as a filter. For example, the support element 425 may be the same material as the conductive film 420, or include the same material, disposed on the second surface 419 to a thickness that provides structural support to the film 410 without hindering the transmission of high-energy particles (e.g., electrons, X-ray photons, etc., above a given energy) through the film. As will be described in more detail with reference to Figure 5, some embodiments of the present disclosure omit the support element 425 to support the independent membrane 410.

[0062] The exemplary filter 400 is shown in an annular form factor. Embodiments of the present disclosure include, but are not limited to, additional and / or alternative form factors, including a rectangular form factor or other polygonal form factors. Similarly, the schematic diagram in Figure 4A is not intended to limit the geometric arrangement of the components of the exemplary filter 400. The exemplary filter 400 is shown in a concentric configuration, with the aperture 415 substantially centered around axis A. However, in some embodiments, the aperture 415 may be offset with respect to the geometric center of the film 410, for example, in which case the film 410 is shaped to protect the detector surface from particles radiated from a specific angle with respect to the beam axis A and / or over a range of angles that are not rotationally symmetric about the beam axis A.

[0063] The film 410 may include materials that exhibit energy-dependent transmittance to high-energy particles. As will be explained in more detail with reference to Figure 7, selective transmittance refers to a film 410 that allows at least some incident particles of a given energy to pass through the filter 400, while absorbing, reflecting, or otherwise blocking the transmission of other forms of incident particles, such as relatively low-energy photons and relatively large charged particles (e.g., electrons, ions, etc.) below a given energy. The material of the film 410 can block all or substantially all photons and charged particles below their respective threshold energies. For example, the film 410 can absorb, reflect, or otherwise block substantially all electrons having an energy of about 7.8 keV or less, as will be explained in more detail with reference to Figure 7. In another example, a film 410 with a thickness of about 500 nm can block substantially all electrons and substantially all ions with an energy of less than 700 eV, but may be relatively transmittance across the visible spectrum for photons.

[0064] In some embodiments, the threshold energy can be selected based at least partially on the filter thickness and / or filter density as parameters. For example, a filter with a thickness of about 2 μm can block incident electrons having energies below about 2.5 keV, but below 7.8 keV. The thickness dependence of the filter performance allows for tuning of operating conditions, as will be explained in more detail with reference to Figures 4A to 7. As described above, relatively thin films can be characterized by high transmittance of electrons and photons while maintaining low transmittance to ions and sputtered materials. For example, single-walled graphene can transmit electrons with energies of about 20 eV and can be substantially transparent to visible and UV photons. Furthermore, the threshold energy may depend at least partially on the composition of the film 410. For example, a film 410 containing multi-walled carbon nanotubes can be characterized by a higher threshold energy compared to a film 410 containing single-walled carbon nanotubes. Similarly, a film 410 with a relatively high nanotube density per unit surface area can be characterized by a higher threshold energy than a film 410 with a relatively low nanotube density per unit surface area.

[0065] In exemplary embodiments, surface density is defined as the mass of the film 410 material per unit surface area (e.g., square centimeters). The properties of the film 410 can be described and / or related via surface density, at least partially based on characteristic volume properties including the volume density of the carbon material (e.g., mass per unit volume) and / or the porosity of the film (e.g., the average percentage of empty space within the film). In some embodiments, the volume density of the carbon material is about 0.11 g / cm³ to about 1.1 g / cm³, including partial range fractions and interpolations. In some embodiments, transparency and thickness are inversely proportional. For example, for a given surface 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%. Thus, for a given film, both the film thickness and transparency can be expressed in terms of surface density. For example, the surface density can be approximately 0.1 μg / cm² to approximately 330 mg / cm², including its partial range, fractions, and interpolations, allowing the dimensions of the film 410, the number of layers, and the thickness of each layer to be determined at least partially on a balance between transparency and dimensional / spatial constraints.

[0066] In some embodiments, the film 410 comprises a carbonaceous material. The carbonaceous material 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 may include carbon nanofibers, nanobamboo, sp2 hybrid carbon, other forms of sp3 hybrid carbon, and / or mixtures thereof (e.g., a combination of graphite and amorphous carbon). Nanotubes, nanobamboo, and / or nanofibers may be oriented along one or more in-plane directions and / or randomly. For example, the film 410 may include layers in which carbon nanotubes constituting a carbon nanotube felt are substantially aligned in the orientation direction. Different layers may be oriented in the same direction or in different directions. While substantially aligned with the orientation direction on a given layer and / or film 410, individual nanotubes, nanofibers, etc., can exhibit twisting (e.g., curvature, angulation / kinking, looping, and / or helical twisting segments) such that a given segment of nanotubes, nanofibers, etc., can be oriented away from the orientation direction. Nevertheless, a layer containing carbon nanomaterials can be substantially planar over macroscopic length scales (e.g., nonwoven nanotube felt or carbon nanofiber cloth). Film 410 may further include, for example, metals, ceramics, and / or nitride materials, as other forms that do not substantially limit the transmittance of the coating, inclusions, or filter 400. Film 410 can be electrically coupled to potentials (e.g., ground potential, positive bias, negative bias). Advantageously, electrically grounding the membrane 410 can improve the absorption and / or neutralization of charged particles (e.g., ion absorption and / or ion surface recombination) without significantly affecting the performance of other components of the charged particle microscope system in which the filter 400 is installed.

[0067] The film 410 can have a thickness 430 of about 10 nm to about 10 μm (e.g., about 10 nm to about 99 μm), including a partial range (e.g., about 0.5 μm to about 30 μm), fractions, and interpolations. The film 410 can include multiple layers 435 of material. For example, the layers 435 may be or include carbon nanotube material with a thickness of about 3 nm to about 1 μm, including their partial ranges, fractions, and interpolations. In one embodiment, each layer 435 may have a thickness of about 0.4 μm, so that a film 410 having two layers 435 of carbon nanotube material can have a thickness of about 0.8 μm, and a film having 25 layers of carbon nanotube material can have a thickness of about 10 μm. Without being bound by any specific physical phenomenon or mechanism, the filter 400 can have a thickness-dependent transmittance based at least partially on the absorbance of each constituent layer 435. In this way, the film 410 may include several layers 435 that allow the filter 400 to absorb substantially all incident infrared, visible, and ultraviolet photons and / or ions, while enabling the transmission of a substantial portion of X-rays and / or electrons having energies above a given threshold.

[0068] Each layer 435 can have a photon absorption of approximately 1% to 90% (e.g., measured at 525 nm). In an example of 25 layers of carbon nanotube material, where each layer has an absorbance of approximately 40% at 525 nm, the overall absorption coefficient of the film 410 for photons at 525 nm can be approximately 1 × 10⁻⁹. In an example of film 410 with a thickness of approximately 2 μm, the transmittance of Li Kα (55 eV) X-rays 275 may be approximately 23%. In this way, the filter 400 can improve the performance of the detector by protecting the acceptor layer from incident particles that would otherwise reduce the quantum efficiency of the detector, while allowing a substantial portion of the target particles (e.g., X-ray photons, electrons, etc.) to reach the detector.

[0069] Figure 4B is a schematic diagram of an exemplary pole piece 450 according to several embodiments of the present disclosure. The exemplary pole piece 450 includes the exemplary filter 400 of Figure 4, which comprises a film 410 and a retaining element 405, as described with reference to Figure 4A. The exemplary pole piece 450 is an example of the pole pieces of the present disclosure (e.g., pole piece 109 in Figure 1, pole piece 205 in Figure 2). For that purpose, the exemplary pole piece 450 includes a mirror detector 455, a mirror electrode 465, and may include additional and / or alternative detectors, electrodes and other components described with reference to Figures 1 and 2, as well as other components (e.g., lens coils, apertures, etc.).

[0070] Without being constrained by any particular physical mechanism or phenomenon, the particle detectors of this disclosure may be configured to generate an electrical signal in response to the incidence of high-energy particles (e.g., electrons, X-rays, etc.) onto the absorption surface of an acceptor layer, which may include a doped semiconductor layer, for solid-state detectors. As will be described in more detail with reference to Figure 5, the penetration of high-energy particles into the acceptor layer can generate electron-hole pairs that can be separated and driven into each conductive layer by the force of a bias voltage applied across the acceptor layer. A current measurement circuit may be configured to integrate the current drawn out of the acceptor layer and / or returned to ground or relative ground over a period of time (e.g., as part of imaging or in coordination with the scanning pattern of an SEM during a defined exposure time for spot-mode analysis). The magnitude of the bias voltage may be at least partially based on the thickness of the acceptor layer as an approach to improve detector efficiency (e.g., by reducing the probability of electron-hole recombination in the acceptor layer).

[0071] The detector 455, like the exemplary filter 400, may be configured to be incorporated into the exemplary charged particle system 100 of Figures 1 and 2. For that purpose, the detector 455 may define an aperture 460 substantially centered around axis A. In some cases, the aperture 415 of the filter 400 and the aperture 460 of the detector 455 may be aligned and concentric (although at different positions on axis A) and / or co-extended (e.g., having substantially equal diameters). In some embodiments, the filter 400 is coupled to the detector 455 via a mirror electrode 465. The filter 400 may also be coupled to the detector 455 with an offset (e.g., as shown in Figure 4C), to a pole piece 450 (e.g., outside the mirror electrode 465), to be positioned on the pole piece 450 between the detector 455 and the mirror electrode 465 (e.g., as shown in Figure 2), and / or to the inner surface 467 of the mirror detector (e.g., a surface oriented toward axis A). Each of the different configurations described offers different functional advantages. For example, placing the filter 400 between the mirror electrode 465 and the detector 455 allows the lower row portion of the filter 400 to be shielded from the bias potential applied to the filter 400. Furthermore, separating the filter 400, detector 455, and mirror electrode 465 allows different bias potentials to be applied to each component. In another example, coupling the filter 400 with the mirror electrode allows the filter 400 to carry the same bias potential and function as part of the mirror electrode to repel electrons with relatively low energy.

[0072] Figure 4C is a schematic diagram of an exemplary pole piece 450 according to several embodiments of the present disclosure. The pole piece 450 is configured to be incorporated into a charged particle beam instrument (e.g., a scanning electron microscope (SEM)).

[0073] Filter 400 is an example of a filter of the present disclosure (e.g., filter 240 in Figure 2). The filter 400 and detector 455 define their respective apertures, which are shaped to accommodate a beam of charged particles oriented along axis A. The coupling between the retaining element 405 of the filter 400 and the mirror electrode 455 can be facilitated by mechanical fastening such as threading, grooves and tongues, spring fasteners, set screws, or other approaches. In some embodiments, the filter 400 is disposed within the mirror electrode via a friction joint and held in place against a substantially smooth and polished inner surface 467.

[0074] The film 410 of the filter 400 can be substantially self-supporting across the span of the mirror electrode 455. As will be described in more detail below with reference to Figure 6, the retaining element 405 can function as a frame that holds the film 410. The combination of material properties (e.g., Young's modulus, flexural modulus, strength, geometric stiffness, etc.) of the bulk material (e.g., a composite material of various materials that together exhibit overall material properties that can differ from the constituent materials) can enable the film 410 to self-support across the inner distance between the edges of the retaining element 405.

[0075] Figure 5 is a schematic diagram of an exemplary detector 500 according to several embodiments of the present disclosure. The exemplary detector 500 may be an example of a detector of the present disclosure (e.g., detectors 215, 220, or 225 in Figure 2, detector 455 in Figures 4A and 4B). The exemplary detector 500 is positioned near the filter 505 and is electronically coupled to the electronic circuit 550. The detector 500 defines an absorbing surface 535 having one or more patterned contacts 540 on the surface of the detector 500 such that electron-hole pairs generated in the active layer 525 of the detector 500 are separated by a bias voltage applied across the detector 500 and drawn toward the opposing contacts 540.

[0076] The filter 505 includes a film 510 within a frame 515. The frame can be coupled with a holding arm 520 that can position the filter 505 relative to the detector 500. In some embodiments, the filter 505 can be moved relative to the detector 500. As shown, the filter 505 is positioned between the sample 530 and the detector 500. In this way, the filter 505 can selectively absorb, reflect, or otherwise block incident particles 570 (e.g., ions, relatively low-energy electrons, IR / VIS / UV photons, etc.) and allow a subset of incident particles 575 to pass through the film 510 (e.g., relatively high-energy electrons, characteristic X-ray photons, etc.).

[0077] As will be described in more detail with reference to Figure 4A, the membrane 510 may include multiple layers of filter material (e.g., carbon nanotube nonwoven felt). The frame 515 can be coupled to the membrane 510 over at least a portion of its periphery. In this way, the frame 515 mechanically supports the membrane, allowing the membrane 510 to be substantially self-supporting over the region of the filter 505 corresponding to the detector 500. As will be described in more detail with reference to Figure 4A, the membrane 510 may be characterized by one or more material properties that enable the membrane 510 to maintain structural integrity under the operating conditions of a charged particle beam system (e.g., the exemplary system 100 in Figure 1) and under exposure to incident particles 570 emitted from the sample 530, with substantially no mechanical support over the internal portion of the membrane 510 close to axis A and away from the frame 515.

[0078] In some embodiments, one or more portions of the frame 515 and / or the retaining arm 520 may be or may include a conductive material. In this way, the frame 515 can be electrically coupled to the film 510, thereby allowing a bias voltage to be applied to the film 510. As will be described in more detail with reference to Figure 10, the bias voltage applied to the film 510 and / or the frame 515 can be used to accelerate / attract charged particles in opposite directions, as well as to repel or decelerate charged particles, and / or to filter charged particles below a given threshold energy.

[0079] Figure 6 shows exemplary transmittance data plots of several types of detectable signals according to several embodiments of the present disclosure. In the plots, the x and y coordinates plot the transmittance of the filter against X-rays (dashed lines) and electrons (solid lines) against energy in electron volts. Transmittance data for the filters of the present disclosure are provided by white circles (○) for X-ray data and white squares (□) for electron data. Dashed lines (- ● -) provide a simulated X-ray transmittance curve for the filters of the present disclosure, and dashed lines (- - -) provide a simulated X-ray transmittance curve for a conventional pure beryllium window used to shield a solid-state X-ray detector.

[0080] The data in Figure 6 demonstrate that the filters of this disclosure do not impair the performance of an X-ray photon detector (e.g., a silicon drift detector). Furthermore, the detectors of this disclosure may be substantially insensitive to electron flux, as evidenced by the fact that the transmittance of the filters for which data is shown is less than 0 percent, for electrons with energies below approximately 7.8 keV, corresponding to energies nearly two orders of magnitude greater than Mo Lα X-rays. As will be described in more detail with reference to Figures 4A–5, the transmittance of the filter material at a given energy may be at least partially based on the dimensions of the filter film (e.g., film thickness 430 in Figure 4A). Thus, the energy selectivity of the filters of this disclosure is given as a single example of a filter configured to absorb substantially all electrons below approximately 7.8 keV, although the numerical value of the threshold energy can be lowered, for example, to facilitate electron detection (e.g., in a mirror detector). Ion transmittance is not provided, as it is negligible or zero for the energy range shown in the plots in Figure 6.

[0081] For example, the filters of the present disclosure can be configured to transmit at least a portion of electrons over an energy range of about 30 eV. Advantageously, the filters of the present disclosure are substantially opaque to ultraviolet, visible, and / or infrared photons (e.g., photons), ions, and sputtered and / or ablated materials. In this way, the filters of the present disclosure can be used to improve measurements of luminescent and / or heated samples where photon noise in the detector data may be significant in current detector techniques.

[0082] Figure 7 shows exemplary detection efficiency data as a function of beam energy for several embodiments of the present disclosure. The data in Figure 7 shows that the filters of the present disclosure (e.g., filter 240 in Figure 2, filter 400 in Figures 4A-4B, filter 515 in Figure 5, etc.) cause an energy-dependent decay of detector efficiency (e.g., a reduction in detector efficiency compared to an unfiltered detector). Efficiency data for filtered detectors are provided by filled squares (■) and filled circles (●), while control data are provided by filled diamonds. The two sets of data with filtered detectors represent a biased detector and an unbiased detector, respectively.

[0083] These data were collected using a calibrated electron source with a known beam current and a pure boron detector, allowing for a direct comparison of detector currents with and without a filter film placed between the beam source and the detector surface. The data demonstrate that the filter of this disclosure can protect the solid-state detector with improved performance compared to control at relatively low energies below about 2 keV, while also protecting the detector surface from damage described with reference to Figures 3A–3C. For example, between about 1 keV and about 2 keV, the detector of this disclosure exhibits detection efficiencies about 5%–15% higher with the filter and under the applied bias compared to the presented control data. Furthermore, with the applied positive bias, the detector's detection efficiency exceeds 50% even at the minimum energy (e.g., less than 100 eV), demonstrating that the filter did not impose a lower limit on transmittance when a surface bias was applied to the film and / or detector.

[0084] Figure 8 is a plot of exemplary detector current data for multiple particles and a detector according to several embodiments of the present disclosure. The data in Figure 8 shows the unfiltered detector signal over a series of exposures of the detector to ion radiation, resulting in damage to the detector surface, as will be described in more detail with reference to Figures 3A–3C. As shown, the normalized detector signal on the vertical "Y" axis does not return to its initial state (normalized to a value of zero at time T1). During the first exposure period, between time T1 and time T2, the detector signal increases substantially monotonically with exposure time, and thereafter the detector signal does not recover but rather remains elevated. The detector signal increases substantially monotonically again between time T3 and time T4, when the detector surface is again exposed to ion radiation. This is repeated during the third exposure period between time T5 and time T6, after which the detector signal decreases slightly and remains elevated.

[0085] As can be understood, the increased detector signal between time T2 and time T3 represents significant noise, which significantly impairs the detector's performance during the same period. Due to the progressive nature of the effect, the sequence of ion emission events can substantially reduce the detector's sensitivity to the electron signal, and leakage current can contain a large portion of the detector signal, overwhelming the relatively small signal originating from incident electrons. Advantageously, the filters of this disclosure are substantially opaque to ions and can reduce or substantially eliminate the effects shown in the data of Figure 8, as shown in Figures 9A–9C.

[0086] Figure 9A is a plot of exemplary detector current data for an unfiltered solid-state detector according to several embodiments of the present disclosure. The data was collected by exposing a mirror detector (e.g., MD215 in Figure 2) to a composite flux of secondary electrons and ions resulting from the exposure of a sample to a focused ion beam (FIB) in multiple instances, labeled at various time points (T) on the horizontal "X" axis, with the resulting normalized detector current plotted on the vertical "Y" axis. In each instance (Ti), the detector current increases significantly and discontinuously, indicating a sudden result of the flux of ions in the FIB reflected from the sample surface toward the detector. Also, as described with reference to Figures 3A-3B and Figure 8, the detector current does not return to its initial value at time To, but instead exhibits a hysteresis effect at least partially attributable to a change in the band structure of the detector cell. Over the course of 12 exposures to ions in the FIB, the detector current increases progressively, and the asymptotic hysteresis is higher than the value preceding each exposure. The result is an overall increase in the base, or "dark," current of the mirror detector labeled ΔI.

[0087] Figure 9B is a plot of exemplary detector current data for a filtered solid-state detector according to several embodiments of the present disclosure. The data in Figure 9B were collected using a mirror detector protected from incident ion flux using the filters of the present disclosure during the same exposure set as in Figure 9A, as described in more detail with reference to Figures 2–8. A significant difference was observed over the course of 12 exposures, particularly in the relative magnitude of the increase in detector current over time, ΔI, which is significantly smaller than the relative magnitude for the unprotected detector in Figure 9A. On the other hand, the current data in Figure 9B showed semi-regular fluctuations, which were attributed to environmental changes over time, as determined by correlated measurements of system parameters and environmental conditions (e.g., ambient temperature). Advantageously, the data in Figure 9B clearly demonstrate that the filters of the present disclosure avoid the technical challenges described with reference to Figures 3A–3C, in particular reducing "damage" to the detector cell caused by ion flux during FIB processing of the sample.

[0088] Figure 9C is a plot of exemplary detector leakage current data for an unfiltered solid-state detector using the present technique. This data reflects another advantage of the filter of the present disclosure by revealing the effect of ion exposure on the performance of an exemplary mirror detector. In particular, the plot in Figure 9C presents the leakage current on the vertical y-axis against time (relative to reference time To) on the horizontal x-axis. In this context, leakage current refers to the current that flows through the detector circuit when the expected current is zero, when the detector is in an "off" state, or when there is no flux of particles incident on the detector surface.

[0089] The detector was exposed to three consecutive doses of ions reflected from the sample surface under FIB exposure, illustrated using hatched areas bounded by short dashed lines. During each consecutive exposure (e.g., T1-T2, T3-T4, T5-T6), the leakage current increased monotonically both within and between a given exposure. In particular, the leakage current appeared to return to the value at the end of the previous exposure period at the start of the subsequent exposure period. Furthermore, the statistical variance of the detector signal increased monotonically with each consecutive exposure, as shown using cross-hatched areas between dashed lines. Finally, the leakage current exhibited a similar hysteresis effect as described with reference to Figures 8-9A, converging to a leakage current value significantly higher than the initial value at To. Along with this, these data highlight the importance of protecting the detector surface from ion exposure, which results in progressive, persistent, and degrading effects on the detector's signal-to-noise characteristics. Advantageously, the filters of this disclosure reduce or substantially eliminate the influence of ions on the performance of the detector and allow the detector to be positioned in line with the sample for processing by the FIB instrument.

[0090] Figures 10A and 10B are block flow diagrams illustrating exemplary processes 1000 and 1050 for active filtering of charged particle signals and acceleration of load charged particles, respectively, according to some embodiments of the present disclosure. One or more operations of exemplary processes 1000 and 1050 may be performed by a computer system communicating with additional systems, including but not limited to characterization systems, network infrastructure, databases, and user interface devices. In some embodiments, at least a subset of the operations described with reference to Figures 10A–10B are performed automatically (e.g., without human involvement) or quasi-automatically (e.g., by human initiation or limited human intervention). In exemplary examples, an operation to change the bias voltage on the conductive layer of the filter may be initiated by a human user and / or automatically implemented as part of a voltage sweep subprocess, and an operation to generate detector data may be performed automatically while system 100 is configured to operate components of a charged particle beam system (e.g., exemplary system 100 in Figure 1). For example, although exemplary process 1000 is described as a series of operations, it is understood that at least some of the operations can be omitted, repeated, and / or rearranged. In some embodiments, additional operations omitted for clarity of description, such as operations for electron source calibration, electron beam alignment and aberration correction, and probe position initialization, precede and / or follow the operations of exemplary process 1000. Similarly, the operations of process 1000 and / or 1050 may be performed in series and / or in parallel, simultaneously and / or separately in time.

[0091] In operation 1005, exemplary process 1000 includes applying a negative bias to a filter film positioned between a sample position in a charged particle beam system and a detector oriented to collect particles emitted from the sample position. As described in more detail with reference to Figures 1 and 2, the detector may be a mirror detector, but may also be another detector, as described in more detail with reference to Figures 3A–3C and 8–9C, such that the detector is more susceptible to degradation by exposure to the particle flux. In this context, applying a negative bias to the film may include applying a voltage to a conductive portion of the filter frame, as described in more detail with reference to Figure 5. Thus, the negative bias corresponds to the energy cutoff of the particle filter, below which electrons with energy below the corresponding threshold are repelled from the second surface. Electrons with average energy above the threshold can be absorbed and / or scattered by the filter film and / or transmitted through the filter film. For that purpose, the operation of exemplary process 1000 can be repeated for multiple values ​​of the bias voltage as an approach to selecting a specific energy in a manner similar to a high-pass energy filter. Advantageously, this technology enables the filters of this disclosure to add dynamic capabilities to charged particle beam systems that are currently unavailable. Furthermore, the high-pass filter operation allows for the selective removal of secondary electrons that are favorable to backscattered electrons, for example.

[0092] In operation 1010, the exemplary process 1000 includes directing a beam of charged particles toward a sample location (e.g., sample 130 in Figure 1). This operation may include a number of sub-operations for generating, modifying, steering, and controlling the beam according to a set of operating parameters that may be at least partially supplied by the user of the charged particle beam system. In some embodiments, operation 1010 includes directing an electron beam toward a sample, but may also include directing a focused ion beam toward a sample, for example, as part of an ion beam processing workflow. Thus, operation 1010 may include one or more operations that constitute at least a part of a typical charged particle imaging, microanalysis, and / or sample preparation process, although these operations are not expressly described as part of this disclosure.

[0093] In operation 1015, the exemplary process 1000 includes generating detector data. As will be described in more detail with reference to the aforementioned drawings, generating detector data may include generating a detector current signal proportional to the flux of incident particles onto the semiconductor acceptor layer of a solid-state detector. As will be described in more detail with reference to Figures 3A-3C, the current signal may be modulated using a bias voltage applied across the acceptor layer (for example, the current signal may be filtered using a negative bias potential). Furthermore, operation 1015 may be performed concurrently with operation 1010, for example, as part of monitoring the progress of an ion beam milling process or as part of electron beam correction of a sample.

[0094] In contrast to exemplary process 1000, exemplary process 1050 in Figure 10B describes an operation to increase the detector signal for a given set of conditions by accelerating electrons toward a filter, thereby increasing the percentage of electrons transmitted through the filter. As will be described in more detail with reference to Figure 6, the electron transmittance of a filter film can be energy-dependent for a given set of material properties and dimensions of the filter. To that end, increasing the energy of charged particles reaching the filter can increase the effective transmittance of the filter, thereby reducing the attenuation caused by charged particles absorbed, reflected, and / or scattered by the filter.

[0095] In operation 1055, an exemplary process 1050 includes applying a positive bias to a filter film positioned between a sample position in a charged particle beam system and a detector oriented to collect particles emitted from the sample position. Advantageously, the positive bias can serve two simultaneous purposes: accelerating negatively charged particles (e.g., electrons) toward the detector through the filter film, and decelerating positively charged particles (e.g., ions) before impacting the film, thereby reducing the degree of ion-induced damage to the material of the filter film. In this way, operation 1055 can improve the detector efficiency for a given electron flux by increasing the average energy of the incident electrons, and can reduce the ion flux and average energy of the ions striking the filter.

[0096] Exemplary process 1050 includes operations 1060 and 1065 that replicate operations 1010 and 1015 of exemplary process 1000 in Figure 10B. In some embodiments, the operations of exemplary processes 1000 and 1050 can be combined in a single process, for example, when combining electron beam processing and ion beam processing, or when using filters as high-pass thresholding filters for electrons in a subset of processes constituting a larger sample preparation workflow, and for boosting electron signals in another subset of processes in the sample preparation workflow.

[0097] The above description has described various embodiments. For explanatory purposes, specific configurations and details have been given to provide a complete understanding of the embodiments. However, it will be apparent to those skilled in the art that embodiments can be practiced without specific details. Furthermore, well-known features may be omitted or simplified in order not to obscure the embodiments described. The exemplary embodiments described herein focus on charged particle beam systems, particularly dual beam systems, but these are intended as non-limiting exemplary embodiments. Embodiments of this disclosure are not limited to such embodiments, but rather are intended to cover analytical instrument systems in which a wide range of material samples can be processed and / or analyzed to determine chemical, biological, physical, structural, or other properties, among other embodiments, including instruments configured to prepare samples for further analysis (e.g., lamellar preparation).

[0098] Some embodiments of this disclosure include a system comprising one or more data processors and / or logic circuits. In some embodiments, the system includes a non-temporary computer-readable storage medium containing instructions that, when executed by one or more data processors and / or logic circuits, cause one or more data processors and / or logic circuits to perform some or all of one or more methods and / or some or all of one or more processes and workflows disclosed herein. Some embodiments of this disclosure include a computer program product tangibly embodied in a non-temporary machine-readable storage medium, containing instructions configured to cause one or more data processors and / or logic circuits to perform some or all of one or more methods and / or some or all of one or more processes disclosed herein.

[0099] The terms and expressions used are for illustrative purposes only and not limiting, and the use of such terms and expressions is not intended to exclude the illustrated and described features or their equivalents, but it should be recognized that various modifications are possible within the scope of the claims. Accordingly, although this disclosure includes specific embodiments and optional features, modifications and changes to the concepts disclosed herein can be made by those skilled in the art, and such modifications and changes should be understood to be within the scope of the appended claims.

[0100] Where terms are used without a clear definition, they should be understood to be used in their ordinary sense unless they have a special and / or specific meaning in the field of charged particle microscopy systems or other related fields. The terms “approximately” or “substantially” are used to indicate a deviation from a described characteristic, such deviation having little or no effect on the corresponding function, characteristic, or attribute of the described structure. In the given example, 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 tolerances such as manufacturing tolerances or confidence intervals inherent to the operation of the system. Similarly, where geometric parameters such as alignment or angular orientation are described as “approximately” perpendicular, “substantially” perpendicular, or “substantially” parallel, the terms “approximately” or “substantially” are intended to reflect that the alignment or angular orientation may differ from the precisely described state within tolerances (e.g., not exactly perpendicular). For numerical values ​​such as diameter, length, and width, the term “approximately” can be understood to describe a deviation of up to ±10% from the stated value. For example, a dimension of "approximately 10mm" can represent a dimension between 9mm and 11mm.

[0101] This specification provides exemplary embodiments and is not intended to limit the scope, applicability, or configuration of the disclosure. Rather, the following description of exemplary embodiments will provide those skilled in the art with a practical guide for implementing various embodiments. It will be understood that various modifications can be made to the function and arrangement of elements without departing from the spirit and scope set forth in the appended claims. Specific details are given in the description to provide a full understanding of the embodiments. However, it will be understood that it is possible to practice without these specific details. For example, specific system components, systems, processes, and other elements of this disclosure may be shown in schematic form or omitted from the drawings so as not to obscure the embodiments with unnecessary details. In other examples, well-known circuits, processes, components, structures, and / or techniques may be shown without unnecessary details.

Claims

1. It is a filter, Frame and, A film of carbon material bonded to the frame, the film comprising a first surface, a second surface opposite the first surface, and an opening extending through the film from the first surface to the second surface, The frame is configured to be coupled to a charged particle detector disposed in a charged particle beam column, and the charged particle detector defines an absorption surface oriented toward the first surface. A filter configured to shield the absorbing surface from particles incident on the second surface.

2. The filter according to claim 1, wherein the carbon material includes carbon nanotubes.

3. The filter according to claim 1, wherein the carbon material comprises a layer of nonwoven carbon nanotube felt.

4. The filter according to claim 1, wherein the film comprises a plurality of substantially planar layers of carbon material.

5. The filter according to claim 1, wherein the membrane is supported by a support material on at least a portion of the membrane.

6. The filter according to claim 1, wherein the charged particle detector is disposed within the pole piece of the charged particle beam column.

7. The filter according to claim 1, wherein the charged particle detector is a mirror detector including a mirror electrode, and the frame is configured to be coupled with the mirror detector.

8. The filter according to claim 7, wherein the mirror electrode defines a first end and a second end, the first end is located near the absorption surface, and the frame is disposed near the second end of the mirror electrode and outside the mirror detector.

9. The filter according to claim 7, wherein the mirror electrode defines a first end and a second end, the first end is located near the absorption surface, and the frame is disposed in the magnetic pole piece near the first end of the mirror electrode and inside the mirror detector.

10. The filter according to claim 7, wherein the charged particle detector and the mirror electrode are arranged along the beam axis, and the frame is arranged on the beam axis between the charged particle detector and the mirror electrode.

11. The filter according to claim 1, wherein the frame is offset from the absorption surface.

12. The filter according to claim 1, wherein the frame comprises the film and a conductive portion electrically coupled to a voltage source via a bias circuit.

13. A charged particle beam system, A chamber configured to receive a sample and to maintain a controlled environment in the vicinity of the sample, A charged particle beam column coupled to the chamber and oriented toward the vicinity of the sample, A charged particle detector disposed in the charged particle beam column, wherein the charged particle detector defines an absorption surface, Equipped with a particle filter, The aforementioned particle filter is A frame coupled to the charged particle detector, A film of carbon material bonded to the frame, wherein the film defines a first surface oriented toward the absorption surface, a second surface opposite the first surface, and an opening extending through the film from the first surface to the second surface, and the particle filter is configured to shield the absorption surface from particles incident on the second surface, wherein the particles include electrons, ions, or photons. Charged particle beam system.

14. The charged particle beam system according to claim 13, wherein the frame comprises the film and a conductive portion electrically coupled to a voltage source via a bias circuit.

15. A control circuit operably coupled to the bias circuit, One or more machine-readable media, which, when read by a machine, store instructions causing the control circuit to perform an operation including applying a negative bias to the film via the conductive portion, wherein the negative bias corresponds to the lower energy cutoff of the particle filter, and when it falls below this, electrons directed toward the second surface are repelled, The charged particle beam system according to claim 14, further comprising:

16. A control circuit operably coupled to the bias circuit, One or more machine-readable media, which store instructions causing the control circuit to perform an operation including applying a positive bias to the film via the conductive portion when read by a machine, The charged particle beam system according to claim 14, further comprising:

17. The charged particle beam system according to claim 16, wherein the positive bias is such that electrons incident on the second surface are characterized by an average energy that exceeds a threshold for the transmittance of the film to electrons.

18. The charged particle beam system according to claim 13, wherein the charged particle detector includes a conductive material disposed on at least a portion of the absorption surface, the charged particle detector is electrically coupled to a voltage source via a bias circuit, and the charged particle beam system is configured to apply a bias voltage to the conductive material via the bias circuit.

19. The charged particle beam system according to claim 13, wherein the charged particle detector is a mirror detector including a mirror electrode, and the frame is configured to be coupled to the mirror electrode or disposed between the mirror electrode and the absorption surface.

20. The charged particle beam system according to claim 13, wherein the film comprises a plurality of substantially planar layers of carbon nanotube material.

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