Split ring resonator ion beam source

Abstract

Embodiments of charged particle beam systems, components, and methods for extracting charged particles from a gas are disclosed.SOLUTION: In a first aspect, a charged particle source includes a resonator. The resonator may include a dielectric substrate defining a first side and a second side opposite the first side. The resonator may include a first conductive layer disposed on the first side. The first conductive layer may be disposed according to a pattern that includes a ring portion. The pattern may define a gap in the ring portion of the first conductive layer. The resonator may also include a second conductive layer disposed on the second side. The charged particle source may also include a source electrode. The source electrode may be disposed proximate to the first side. The source electrode may be offset from the dielectric substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to charged particle beam systems and algorithms and methods for their operation. In particular, some embodiments relate to microwave resonator ion sources for focused ion beam systems. [Background technology]

[0002] Miniature plasma sources are used in a variety of applications, including chemical analysis and sterilization. Advantages of miniature plasma sources include relatively low power consumption, simple design and fabrication, mechanical robustness, long life, high non-thermal plasma density, and the ability to operate at atmospheric pressure.

[0003] Compact plasma sources include those based on microstrip split-ring resonators (MSRRs). A conventional MSRR contains a radio frequency transmission line consisting of a dielectric substrate sandwiched between a metal strip and a metal ground plane. The metal strip is a circularly folded dipole, creating a small gap at its two ends across which an electric field can be created. The dipole corresponds to a half-wave microwave resonator, which also finds application in antenna design. The dipole is connected to an additional microstrip transmission line, which is the feedline that provides radio frequency (RF) power.

[0004] At resonance, the potentials at the ends of the dipoles are 180° out of phase, allowing the amplitude of the electric field between them to be amplified by several orders of magnitude. Thus, at relatively low input power, a large potential is generated across the gap, and this potential is used to ignite and sustain the plasma. In a conventional MSRR, the electric field in the microstrip is primarily confined to the dielectric substrate. However, in the gap of a split-ring resonator, the electric field across the folded dipole rises from the substrate and is concentrated in the plane between the ends of the strip. In a conventional MSRR, ion acceleration and average ion velocity within the plasma are at least partially minimized by forcing the average voltage of the RF power signal to approximately 0 V.

[0005] Impedance matching is particularly important in conventional MSRRs because the characteristic impedance of the resonator depends on geometric factors such as the spatial offset of the feedline from the dipole center and the quality factor of the microstrip. Furthermore, the impedance characteristics of conventional MSRRs vary significantly between pre-ignition and post-ignition operating conditions (e.g., in the absence and presence of a microplasma discharge, respectively). Well-matched conditions are typically achieved using dynamic matching circuits with active control systems configured to minimize reflected power received by the power source, resulting in larger size, higher cost, and more complex design and construction. Summary of the Invention

[0006] Embodiments of charged particle beam systems, components, and methods for extracting charged particles from a gas are described. In a first aspect, the charged particle source includes a resonator. The resonator may include a dielectric substrate defining a first side and a second side opposite the first side. The resonator may include a first conductive layer disposed on the first side, the first conductive layer being arranged according to a pattern including a ring portion. The pattern may define a gap in the ring portion of the first conductive layer. The pattern may define a first input point within the ring portion at a first fractional position α on the ring portion. The pattern may also define a second input point within the ring portion at a second fractional position β on the ring portion. The resonator may also include a second conductive layer disposed on the second side. The charged particle source may also include a source electrode. The source electrode may be disposed proximate to the first side. The source electrode may define an aperture. The source electrode may be offset from the first conductive layer. The offset may be defined by a spacer. The spacer may include a dielectric material and / or an insulating material. The spacer may define a conduit. The conduit may form at least a portion of a fluid supply fitting. For a given input point within the ring portion, the fractional position may be a ratio of a first path length between the gap and the given input point in a first direction to a second path length between the gap and the given input point in a second direction different from the first direction.

[0007] In some embodiments, the charged particle source further includes a radio frequency (RF) power source operably coupled to the resonator. A first conductive path from the RF power source through the first input point may be well matched in the absence of a discharge. A second conductive path from the RF power source through the second input point may be well matched in the presence of a discharge. A well matched state may refer to a state in which little or substantially no reflected power is measured at the RF power source during operation. The charged particle source may further include a control circuit configured to supply power from the RF power source to the first input point or the second input point based at least in part on ignition of a discharge between the ring portion and the source electrode. β may be less than α. The source may be configured to supply RF power to the ring portion through the first input point in the absence of a discharge and through the second input point in the presence of a discharge.

[0008] The control circuit may include a first diode electrically coupled to the ring portion via a first conductive path and a second diode electrically coupled to the ring portion via a second conductive path. The control circuit may include a third diode electrically coupled to the first diode and the first inductor via the first conductive path and a fourth diode electrically coupled to the second diode and the second inductor via a second conductive path. The first diode, the second diode, the third diode, and / or the fourth diode may be PIN diodes. The first diode and the third diode may be directionally opposed. The second diode and the fourth diode may be directionally opposed.

[0009] The control circuit may include a DC voltage source electrically coupled to the first conductive path through a first inductor or electrically coupled to the second conductive path through a second inductor. The charged particle source may further include a DC bias tee electrically coupled to the first conductive layer, the DC bias tee having a DC power input and an RF power input and comprising components that configure the DC bias tee to apply a DC bias to the RF power signal, thereby correcting an offset voltage of the RF power signal.

[0010] The pattern may further define a third input point on the ring portion between the first and second input points and at a third fractional position γ relative to the gap.

[0011] In some embodiments, the source electrode is electrically coupled to a common reference voltage with the second conductive layer. The charged particle source can be operably coupled to a focused ion beam (FIB) column. The extraction electrode can be disposed on the optical axis downstream of the source electrode.

[0012] The charged particle source may further include a source assembly. The source assembly may include a fluid supply coupler, a fluid removal coupler, and an electrical coupler. The resonator may be disposed within the source assembly and operably coupled to the electrical coupler. The source electrode may form part of the source assembly. The charged particle source may further include a vacuum enclosure and an isolation support disposed within the vacuum enclosure and mechanically coupled to the vacuum enclosure and the source assembly, the isolation support comprising a material that is electrically insulating below an applied voltage of approximately ±300 kV DC. The source chamber may be fluidly coupled to the FIB chamber via a bypass conduit.

[0013] In a second aspect, a charged particle beam system includes a source section. The source section, in one or more embodiments, can include the resonator of the first aspect. The system can include a focused ion beam (FIB) column operatively coupled to the source section and including a plurality of charged particle optics. The system can also include a vacuum chamber operatively coupled to the FIB column.

[0014] In a third aspect, the charged particle source may include a resonator. The resonator may include a dielectric substrate defining a first side and a second side opposite the first side. The resonator may include a first conductive layer disposed on the first side, the first conductive layer being arranged according to a pattern including a ring portion, the ring portion defining a gap in the first conductive layer. The resonator may include a second conductive layer disposed on the second side. The charged particle source may also include a source electrode disposed proximate to the first side. The source electrode may define an aperture. The source electrode may be offset from the dielectric substrate. The offset may be defined by a spacer. The spacer may include a dielectric material and / or an insulating material. The spacer may define a conduit. The conduit may form at least a portion of a fluid supply fitting.

[0015] In some embodiments, the charged particle source may further include a radio frequency (RF) power source operably coupled to the resonator and calibrated to match the impedance of a radio frequency power signal in the presence of a discharge formed between the ring portion and the source electrode.

[0016] In some embodiments, the gap may be defined between the first and second ends of the ring portion, and the aperture may be substantially centrally located at the first end of the ring portion.

[0017] The ring portion may be a first ring portion. The gap may be a first gap. The pattern may further include a second ring portion defining a second gap. The charged particle source may include an RF power source operably coupled to the resonator via the first ring portion or the second ring portion. The RF power source may be configured to provide a first well-matched impedance condition for the first radio frequency power signal in the presence of a discharge in the first gap. The RF power source may be configured to provide a second well-matched impedance condition for the second radio frequency power signal in the absence of a discharge in the second gap. The first gap and the second gap may be adjacent to each other. The ring portions may define a narrowing taper toward the respective first gap or second gap. The RF power source may be coupled to the resonator via a switching circuit. The switching circuit may be configured to couple the first ring portion to the RF power source in the presence of a discharge and to couple the second ring portion to the RF power source in the absence of a discharge.

[0018] In some embodiments, the first ring portion may define a first power injection point. The second ring portion may define a second power injection point. A first gap may be defined within the first ring portion at a first fractional position α relative to the first power injection point. A second gap may be defined within the second ring portion at a second fractional position β relative to the second power injection point. For a given input point within the ring portion, the fractional position may be a ratio of a first path length between the gap and the given input point in the first direction to a second path length between the gap and the given input point in a second direction different from the first direction. The first fractional position α and the second fractional position β may be substantially equal.

[0019] In some embodiments, the charged particle source can further include a DC bias tee electrically coupled to the first ring portion. The DC bias tee can further include a DC power input and an RF power input. The DC bias tee can include components that configure the DC bias tee to apply a DC bias to the RF power signal, thereby correcting an offset voltage of the RF power signal.

[0020] In some embodiments, the source electrode can be electrically coupled to the second conductive layer and a common reference voltage. The source electrode can include a foil coupled to the support, with an aperture formed in the foil. The aperture can be characterized by a diameter of about 20 μm to about 200 μm (including subranges, fractions, and interpolations) and an aspect ratio of about 0.05 to about 0.5 (including subranges, fractions, and interpolations).

[0021] The charged particle source may be operably coupled to a focused ion beam (FIB) column. The FIB column may include an extraction electrode. The resonator may be oriented relative to the extraction electrode such that the source electrode is between the first side and the extraction electrode. In some embodiments, the charged particle source may further include a source assembly. The source assembly may include a source electrode, a fluid supply coupler, a fluid removal coupler, and an electrical coupler. The resonator may be disposed within the source assembly and operably coupled to the electrical coupler.

[0022] In a fourth aspect, a charged particle beam system includes a source section. The source section, in one or more embodiments, can include the resonator of the third aspect. The system can include a focused ion beam (FIB) column. The FIB column can be operatively coupled to the source section and can include a plurality of charged particle optics. The system can also include a vacuum chamber operatively coupled to the FIB column.

[0023] The source section may further include a source assembly. The source assembly may include a dielectric substrate and a housing coupled to the dielectric substrate. The housing may include a source electrode, a fluid supply coupler, a fluid removal coupler, and an electrical coupler operably coupled to the first conductive layer and / or the second conductive layer through the housing.

[0024] At least a portion of the housing can be coupled to a voltage source. The voltage source can be configured to apply a voltage of about 1 kV to about 350 kV to the portion of the housing. The FIB column can include an extraction electrode. The source section can be oriented relative to the extraction electrode such that the source electrode is between the first side and the extraction electrode.

[0025] In some embodiments, the ring portion may be a first ring portion. The pattern may define a resonant multi-pole structure including the first ring portion. The resonant multi-pole structure may include a second ring portion. The first ring portion and the second ring portion may define four gaps between four ends.

[0026] In a fifth aspect, an optical analysis source may include the charged particle source of the first aspect in one or more embodiments or the third aspect in one or more embodiments. The optical analysis source may be configured to introduce an analyte into a discharge region between the resonator and the source electrode to generate a discharge containing the analyte, and direct a characteristic photon bundle from the analyte from the discharge to a spectrometer. The optical spectrometer may include input optics, diffraction optics, and a detector. The optical spectrometer may be configured to decompose the characteristic photon bundle into one or more constituent beams capable of generating OES spectral data.

[0027] The input optics may include a collimator, one or more lenses, and / or one or more filters. In some embodiments, the input optics may include one or more beam splitters and / or one or more polarizers. The diffractive optics may include a grating, a mirror, a distributed Bragg reflector (DBR), and / or one or more mechanical elements configured to move the diffractive optic relative to one or more other components of the spectrometer. The detector may include one or more sensors, a traversing sensor, and / or electronics configured to generate OES spectral data based at least in part on the characteristic photon flux.

[0028] The analyte may be provided to the discharge region as an atomized vapor, a gaseous vapor, and / or a solid. The source may include a fluid coupler for introducing and / or removing the analyte from the discharge region. The source may be configured to operate at or near atmospheric pressure, under vacuum, and / or at pressures above atmospheric pressure. In some cases, the operating pressure may be based at least in part on the analyte being processed and the corresponding discharge characteristics.

[0029] A gap may be defined in the first conductive layer. The gap may be substantially oriented relative to the source electrode such that a photon flux emanating from the discharge is transmitted from the source to the input optics of the spectrometer. To this end, the source electrode may be or include a material that is substantially transparent to photons in a predetermined spectral range and is conductive. The source electrode may include indium tin oxide (ITO). The source may include a transparent portion.

[0030] In a sixth aspect, an optical analysis source may include the charged particle source of the first aspect in one or more embodiments or the third aspect in one or more embodiments. The optical analysis source may be configured as a sealed light source. The optical analysis source may be configured for use as a light source for optical absorption spectroscopy (OAS) applications and for generating an analyte-containing discharge from which a characteristic bundle of photons may be directed to a spectrometer. The optical spectrometer may include input optics, diffraction optics, and a detector. The OAS system may be configured to pass a test beam of photons through an analysis cell and a reference beam of photons through a reference cell as part of an OAS procedure. The test beam and reference beam may be prepared using optics including a collimator, beam splitter optics, mirrors, and / or partially transmitting mirrors. One or more optics may be coupled to movable components. The movable components may include a motorized turret, a stepper motor, or the like. The characteristic photons may include photons in the ultraviolet energy range and / or the visible energy range. The source may be configured to generate an electric discharge that promotes the emission of photons in the ultraviolet and / or visible spectral ranges.

[0031] In a seventh aspect, a volumetric plasma system may include the charged particle source of the first aspect in one or more embodiments or the third aspect in one or more embodiments. The volumetric plasma system may include a load lock chamber. The load lock chamber may be coupled to a vacuum chamber of a charged particle beam system. The load lock chamber may be reversibly isolated from the vacuum chamber. The load lock chamber may be reversibly isolated from the vacuum chamber by a movable valve. The valve may be a gate valve. The charged particle source may be disposed in the load lock chamber. The charged particle source may be disposed in the vacuum chamber. A sample stage of the charged particle beam system may be configured to have a range of movement extending across the load lock chamber. The sample stage may be configured to have a range of movement extending across the vacuum chamber and across the load lock chamber. The sample stage may be electrically coupled to a voltage source and may function as at least a portion of a source electrode. The source electrode may include a substrate. The substrate may be conductive. The substrate may be electrically coupled to the voltage source via the sample stage. The substrate may be coupled to one or more sample manipulation tools. The sample manipulation tools may be coupled to one or more controllers via vacuum feedthroughs. The sample manipulation tools may be configured to couple the substrate to a sample stage.

[0032] The terms and expressions employed are used as terms of description without limitation, and the use of such terms and expressions is not intended to exclude any equivalents of the illustrated and described features or portions thereof, but it is recognized that various modifications are possible within the scope of the claimed subject matter. Thus, while the subject matter claimed herein has been specifically disclosed by embodiments and optional features, it should be understood that modifications and variations of the concepts disclosed herein may be made by those skilled in the art, and that such modifications and variations are deemed to be within the scope of the present disclosure as defined by the appended claims. For example, the above-described aspects and various embodiments may be combined with one or more other aspects and / or embodiments of the same or other aspects. [Brief explanation of the drawings]

[0033] The foregoing aspects and many of the attendant advantages of the present disclosure will become better understood as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, in which:

[0034] [Figure 1] FIG. 1 is a schematic diagram illustrating an exemplary dual beam system, according to some embodiments of the present disclosure. [Figure 2A] FIG. 1 is a schematic diagram illustrating an exemplary ion source according to some embodiments of the present disclosure. [Figure 2B] FIG. 1 is a schematic diagram illustrating an exemplary source assembly, according to some embodiments of the present disclosure. [Figure 3A] FIG. 1 is a schematic diagram illustrating an exemplary ion source according to some embodiments of the present disclosure. [Figure 3B] FIG. 1 is a schematic diagram illustrating an exemplary ion source according to some embodiments of the present disclosure. [Figure 4A] FIG. 3C is a schematic diagram illustrating an exemplary optical emission spectroscopy system including the ion source of FIGS. 2A-3B, according to some embodiments of the present disclosure. [Figure 4B] FIG. 3C is a schematic diagram illustrating an exemplary optical absorption spectroscopy system including the ion source of FIGS. 2A-3B, according to some embodiments of the present disclosure. [Figure 4C] FIG. 3C is a schematic diagram illustrating an exemplary volumetric plasma system including the ion source of FIGS. 2A-3B, according to some embodiments of the present disclosure. [Figure 4D] FIG. 3C is a schematic diagram illustrating an exemplary volumetric plasma system including the ion source of FIGS. 2A-3B, according to some embodiments of the present disclosure. [Figure 5A] FIG. 3C is a schematic diagram illustrating the exemplary ion source of FIGS. 2A-3B including a single split-ring resonator, according to some embodiments of the present disclosure. [Figure 5B] FIG. 3C is a schematic diagram illustrating the exemplary ion source of FIGS. 2A-3B including a single split-ring resonator, according to some embodiments of the present disclosure. [Figure 5C]FIG. 3C is a schematic diagram illustrating the exemplary ion source of FIGS. 2A-3B including a single split-ring resonator, according to some embodiments of the present disclosure. [Figure 6A] FIG. 5B is a schematic diagram illustrating the exemplary ion source of FIGS. 5A-5C including a bias tee, according to some embodiments of the present disclosure. [Figure 6B] FIG. 5B is a schematic diagram illustrating the exemplary ion source of FIGS. 5A-5C including a bias tee, according to some embodiments of the present disclosure. [Figure 6C] FIG. 5B is a schematic diagram illustrating the exemplary ion source of FIGS. 5A-5C including a bias tee, according to some embodiments of the present disclosure. [Figure 7A] FIG. 3C is a schematic diagram illustrating the exemplary ion source of FIGS. 2A-3B including a double split-ring resonator, according to some embodiments of the present disclosure. [Figure 7B] FIG. 3C is a schematic diagram illustrating the exemplary ion source of FIGS. 2A-3B including a double split-ring resonator, according to some embodiments of the present disclosure. [Figure 7C] FIG. 3C is a schematic diagram illustrating the exemplary ion source of FIGS. 2A-3B including a double split-ring resonator, according to some embodiments of the present disclosure. [Figure 8A] FIG. 7D is a schematic diagram illustrating the exemplary ion source of FIGS. 7A-7C including a bias tee, according to some embodiments of the present disclosure. [Figure 8B] FIG. 7D is a schematic diagram illustrating the exemplary ion source of FIGS. 7A-7C including a bias tee, according to some embodiments of the present disclosure. [Figure 9A] FIG. 3C is a schematic diagram illustrating the example ion source of FIGS. 2A-3B including multiple input points, according to some embodiments of the present disclosure. [Figure 9B] FIG. 3C is a schematic diagram illustrating the example ion source of FIGS. 2A-3B including multiple input points, according to some embodiments of the present disclosure. [Figure 9C] FIG. 3C is a schematic diagram illustrating the example ion source of FIGS. 2A-3B including multiple input points, according to some embodiments of the present disclosure. [Figure 9D]FIG. 3C is a schematic diagram illustrating the example ion source of FIGS. 2A-3B including multiple input points, according to some embodiments of the present disclosure. [Figure 10A] FIG. 3C is a schematic diagram illustrating the exemplary ion source of FIGS. 2A-3B including a multi-pole resonant structure, according to some embodiments of the present disclosure. [Figure 10B] FIG. 3C is a schematic diagram illustrating the exemplary ion source of FIGS. 2A-3B including a multi-pole resonant structure, according to some embodiments of the present disclosure. [Figure 10C] FIG. 3C is a schematic diagram illustrating the exemplary ion source of FIGS. 2A-3B including a multi-pole resonant structure, according to some embodiments of the present disclosure. [Figure 10D] FIG. 3C is a schematic diagram illustrating the exemplary ion source of FIGS. 2A-3B including a multi-pole resonant structure, according to some embodiments of the present disclosure. [Figure 11] FIG. 1 is a block flow diagram illustrating an exemplary process for extracting a beam of ions from a discharge, according to some embodiments of the present disclosure.

[0035] In the drawings, like reference numbers refer to like parts throughout the various views unless otherwise specified. To reduce clutter in the drawings where appropriate, not all elements are necessarily labeled. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles being described. DETAILED DESCRIPTION OF THE INVENTION

[0036] While particular embodiments have been illustrated and described, it will be understood that various modifications can be made without departing from the spirit and scope of the present disclosure. The following paragraphs describe embodiments of charged particle beam systems, components, and methods for extracting ions from a gas. For ease of explanation, the disclosed embodiments focus on techniques for improving alignment and control of different discharge regimes as applied in focused ion beam (FIB) instruments. To that end, the embodiments are not limited to such systems, but rather are discussed in analytical instrument systems where extracting charged particles from relatively small volumes of gas can be a technical challenge. In illustrative examples, FIB sources can benefit from miniaturization and circuit design to improve the transition from pre-ignition mode to discharge mode without the use of dynamic alignment circuits. Similarly, the disclosed compact discharge systems can be integrated into optical delivery systems, sample loading and preparation components (e.g., load lock chambers), and the like. While the disclosed embodiments focus on dual-beam FIB-SEM systems, additional and / or alternative systems are contemplated, including, but not limited to, single-beam FIB systems, portable ion sources, and optical delivery systems in which a micro-discharge can serve as the light source.

[0037] Embodiments of the present disclosure include systems, methods, algorithms, and non-transitory media having computer-readable instructions stored thereon for extracting ions from a discharge using a split-ring resonator plasma source. In an illustrative example, a charged particle source system may include a resonator. The resonator may include a dielectric substrate defining a first side and a second side opposite the first side. The second side may be opposite the first side. The resonator may include a first conductive layer disposed on the first side. The first conductive layer may be arranged according to a pattern including a ring portion. The ring portion may define a gap in the first conductive layer. The resonator may also include a second conductive layer disposed on the second side. The source system may include a source electrode. The source electrode may be disposed proximate to the first side. The source electrode may define an aperture. The source electrode may be offset from the first conductive layer. Embodiments of the present disclosure include multiple power input points on a single ring segment, multiple ring segments providing multiple gaps, a bias circuit that applies an offset voltage to an AC power signal (e.g., an RF power signal), and a multipole structure configured to reduce or substantially eliminate thermalization of ions within the gap(s). In this manner, the split-ring resonator source of the present disclosure can function as a tunable ion source in charged particle beam systems and other analytical instrument systems while providing well-matched impedance conditions in both the presence and absence of a discharge without relying on dynamic impedance matching circuitry.

[0038] 1 is a schematic diagram illustrating an exemplary dual beam system 100 according to some embodiments of the present disclosure. The 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 vacuum chamber 120, and a sample stage 125. The electron beam column 107 is shown as a scanning electron microscope (SEM) column, such 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 operatively coupled to the vacuum 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. Axis A and Axis B are shown converging on a region of sample 130, and GIS 115 is oriented toward the region of sample 130 and configured to direct a gas flow containing precursors into the vacuum chamber. Advantageously, Axis A and Axis B may be oriented toward different locations, but the convergence allows the SEM system to image the region of the sample being processed with the FIB.

[0039] The electron source 105 may include one or more emitters configured to generate free electrons and direct them to the electron beam column 107. The emitters may include thermionic emitters, Schottky emitters, field emission emitters, or combinations thereof, and are operably coupled to a power system configured to apply a high voltage (e.g., on the order of several kilovolts to several hundred kilovolts) to an emitting 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 the emission of electrons from the tip of the emitter crystal. In this manner, an electron beam may be directed to the electron beam column 107.

[0040] The electron beam 107 includes electromagnetic optics (e.g., electrostatic lenses, electromagnetic lenses, monochromators, aberration correctors, etc.) and apertures configured to shape, focus, defocus, narrow, and / or direct the electron beam such that the beam is focused onto the sample 130 according to a set of operating parameters. The operating parameters may include beam current, beam energy (e.g., volts, electron-volts, etc.), a magnification parameter, a scan pattern, a dwell time, and / or one or more pulse parameters. In this manner, the exemplary system 100 may function as an SEM to image a portion of the sample 130 and / or may be used for electron-beam-assisted deposition of material onto the sample 130 (e.g., in conjunction with the GIS 115) or other sample modification.

[0041] The ion source 110 may include one or more components configured to generate an ion beam and direct the ions into the FIB column 111. Generally, the ions may include metal ions and / or non-metal ions (e.g., noble gases, halogens, oxygen, or nitrogen). To that end, the ion source 110 may include a plasma source (e.g., an inductively coupled plasma source or a microplasma source as disclosed herein) and / or a metal ion source (e.g., a liquid metal ion source). In the context of the present disclosure, atomic and / or molecular gases, as well as mixtures thereof, may serve as plasma precursor gases from which an ion stream can be extracted. To that end, embodiments of the present disclosure relate to systems, components, and methods for igniting and sustaining a plasma discharge, and may include related techniques for extracting ions from the plasma discharge. In some embodiments, the ion source 110 includes a microwave resonator circuit configured to provide well-matched conditions for one or more discharge modes in the presence and / or absence of a plasma discharge. Embodiments of the microwave resonator circuits of the present disclosure and their operation are described in more detail with reference to FIGS. 2A-11 .

[0042] Similar to the electron beam column 107, the FIB column 111 may include electromagnetic optics (e.g., electrostatic lenses, electromagnetic lenses, monochromators, aberration correctors, etc.) and apertures configured to shape, focus, defocus, narrow, and / or direct the ion beam such that the beam is focused onto the sample 130 according to a set of operating parameters. The operating parameters may include beam current, beam energy (e.g., volts, electron-volts, etc.), a magnification parameter, a scan pattern, a dwell time, and / or one or more pulse parameters. In this manner, the exemplary system 100 may function as a FIB used to modify a portion of the sample 130 and / or (e.g., in conjunction with the GIS 115) for ion-beam-assisted removal of material from and / or deposition of material onto the sample 130.

[0043] Similar to the energies described for electron beams above, ion beam energies may be selected (e.g., by a user, by a user-initiated algorithm, and / or automatically without user intervention). In some embodiments, additional and / or alternative precursor decomposition mechanisms (e.g., surface activation and / or secondary electron re-emission) may be used as precursor decomposition mechanisms, thereby allowing ion beam energy to be determined based at least in part on the relationship between beam energy, sample material properties, and the energetics of the precursor deposition reaction mechanism. Advantageously, ion beam-induced deposition may result in relatively high yields compared to electron beam-induced deposition, based at least in part on the combined effects of multiple energy transfer pathways.

[0044] The GIS 115 includes components that both enable the GIS 115 to generate a gas flow containing a precursor and direct the gas flow into the vacuum chamber. The components of the GIS 115 may include a carrier gas inlet, a nozzle 119, and a conduit fluidly connecting the nozzle 119 to a precursor reservoir 117. The precursor reservoir 117 may include a substantially non-reactive container (e.g., a ceramic crucible, a PTFE enclosure, a non-reactive metal or alloy, etc.) at least partially exposed to the conduit. In this manner, vapor generated from a precursor disposed in the precursor reservoir 117 may be directed into the vacuum chamber toward the nozzle (e.g., by pressure-driven flow induced by a pressure gradient relative to the vacuum of the vacuum chamber). In some embodiments, the GIS 115 includes a carrier gas inlet fluidly connected to the nozzle 119 via a conduit. In this manner, the precursor may be entrained in the carrier gas flow and directed into the vacuum chamber toward the nozzle. Additionally and / or alternatively, the precursors may comprise gases at standard conditions and may be introduced into the GIS 115 via gas inlets provided as part of the GIS 115 .

[0045] The operation of one or more components of the exemplary system 100 may be coordinated by control circuitry according to machine-executable instructions (e.g., software, firmware, etc.), which may be stored on a machine-readable storage medium and / or received from an external system via wired and / or wireless communication techniques (e.g., via a WiFi or Bluetooth link). To that end, the components of the exemplary system 100 may be automated (e.g., operate without human intervention), pseudo-automated (operate with limited human intervention to initiate operations, analyze outputs, verify, etc.), or manually operated (e.g., where individual operations of the exemplary system 100 are performed and / or coordinated by a human user). In the illustrative example, the sample stage 125 may be mechanically coupled to an automated stage controller 127 that enables the sample 130 to be reversibly tilted relative to beam axes A and B such that the surface of the sample is oriented at a specific angle relative to a given beam axis during operation of a corresponding charged particle beam source. In this manner, operation of a given beam source may be coordinated with operation of the stage controller 127. In another example, a detector provided as part of the exemplary system 100 may be integrated into a control system configured to manipulate one or more operating parameters of the ion source 110 as part of a control scheme to maintain a set point for beam brightness, as described in more detail with reference to FIG. 11 .

[0046] Some embodiments of the present disclosure omit one or more components of the exemplary system 100. For example, one or more of the sources 105 and 110 and / or the columns 107 and 111 may be omitted. In an illustrative example, a single-beam FIB system may be configured to perform the operations for generating an ion beam. Similarly, multi-beam FIB systems other than dual-beam FIB-SEMs (e.g., FIB-laser systems or FIB-SEM systems in which two or more beam axes are not convergently trained on a predetermined region of the sample 130) may include a charged particle source of the present disclosure.

[0047] 2A is a schematic diagram illustrating an exemplary ion source 200 according to some embodiments of the present disclosure. In the following description, the exemplary ion source 200 is also referred to as an “inverted” design, referring to the relative positions of the active components of the ion source and the active components of the FIB column (e.g., the FIB column 111 of FIG. 1 ). To that end, the exemplary ion source 200 may be an example of the ion source(s) 110 of FIG. 1 and may be configured to operate as part of the exemplary system 100 of FIG. 1 . The exemplary ion source 200 includes a source assembly 205, a fluid supply coupler 210, an electrical coupler 215, an optical coupler 220, and a fluid removal coupler 225. The source assembly 205 includes a resonator 230. The exemplary ion source 200 may include a vacuum enclosure 235 configured to maintain a vacuum environment around the source assembly 205, an isolation support 240, and a bypass conduit 237. The exemplary ion source 200 may include a source electrode 231, an extraction electrode 233, and one or more power circuits 217. In some embodiments, the extraction electrode 233 is a component of the FIB column and is introduced into the vacuum environment via a connection between a vacuum enclosure 235 and the FIB column.

[0048] 2A depicts a cross-sectional view of an exemplary ion source 200. To that end, some of the components of the exemplary ion source 200 are at least partially rotationally symmetric about axis B (e.g., second axis B in FIG. 1 ). Other components are not rotationally symmetric. For example, the isolation support 240 may be a solid of revolution having a truncated horn shape. As shown with reference to FIG. 2B , the source assembly 205 may likewise be substantially symmetric about axis B, although other shape factors may be assumed, for example, as may be dictated by the constraints of the vacuum enclosure 235.

[0049] The various couplers 210, 215, 220, and 225 can be configured to supply materials, energy, and diagnostic capabilities to the source assembly 205. For example, the fluid supply coupler 210 and fluid removal coupler 225 can be coupled to fluid processing conduits (e.g., gas vacuum feedthroughs, liquid / vapor coolant feedthroughs, etc.) and can be configured to supply fluids near the resonator 230, as described in more detail with reference to FIGS. 3A-11. In this context, the term "fluid" refers to a gas, liquid, or other phase characterized by a tendency to flow from a region of relatively high pressure to a region of relatively low pressure, or by other mechanisms (e.g., molecular flow regimes). To that end, a fluid can be or include a volatilized precursor entrained in a carrier gas (e.g., vapor) or a vapor stream without a carrier gas. Embodiments of the present disclosure include multiple fluid supply couplers 210 and fluid removal couplers 225 dedicated to different purposes. For example, one pair of couplers may be configured to supply a plasma precursor fluid (e.g., a gas mixture, a vapor mixture, etc.) to the resonator 230, and a second pair may be coupled to one or more cooling loops to remove heat from the resonator 230 (e.g., using a liquid coolant).

[0050] In some embodiments, the fluid supply coupler 210 includes a feedthrough 221 configured to fluidly couple the relatively high-pressure environment near the resonator 230 with a fluid supply system external to the vacuum enclosure 235. By way of example, the feedthrough 221 may be or include a capillary tube or other conduit that allows plasma precursors to be delivered to the relatively high-pressure area near the resonator. Similarly, the fluid removal coupler 225 may be coupled to a vacuum system to allow precursors to be exhausted from the vicinity of the resonator 230 to the relatively high vacuum environment and / or to maintain pressure at the outlet of the source assembly 205. In this manner, fluids delivered to the relatively high-pressure environment near the resonator 230 (e.g., the discharge region) are preferentially drawn into the fluid removal coupler 225 rather than being drawn into the vacuum environment of the FIB system (e.g., via aperture 265 in FIG. 2B ).

[0051] The resonator 230 may be electrically coupled to the power circuit(s) 217 ​​via an electrical coupler 215. As described in more detail with reference to FIGS. 4A-10C, the power circuit(s) may include a radio frequency (RF) alternating current (AC) power source and / or a direct current (DC) power source. In an illustrative example, the source assembly 205 may include a microwave amplifier and a DC bias circuit. The microwave amplifier may draw between about 0.5 watts and about 30 watts (including sub-ranges, fractions, and interpolations). The power drawn by the microwave amplifier may be based at least in part on operating parameters of the plasma source (e.g., power supply to the plasma). In some embodiments, the control circuit (e.g., a microcontroller coupled to the power circuit) and the DC bias power source are configured to draw between about 0.1 watts and about 10 watts (including sub-ranges, fractions, and interpolations).

[0052] To facilitate operation of the resonator 230 as an RF plasma source, one or more forms of RF shielding (e.g., a Faraday shield) may be provided to protect the electrical components of the exemplary ion source 200 from electromagnetic interference (EMI). For example, the electrical coupler 215 and the RF power supply and / or resonator components (e.g., electronic components provided on the resonator substrate shown in FIGS. 7C, 8B, and 9C) may be shielded. Such shielding may also serve to reduce interference between DC components of the exemplary ion source 200, such as the source electrode 231 and / or DC power circuitry, as described in more detail with reference to FIGS. 6A-6C.

[0053] In some embodiments, the source assembly 205 is shaped to receive the isolation support 240 so that the electrically active elements of the exemplary ion source 200 are shielded from the triple junction formed between the isolation support 240, the source assembly 205, and the surrounding vacuum environment. Without being bound to a particular physical mechanism or interpretation, shielding the triple junction in this manner may reduce the likelihood of electronic surface flashover or other electrical breakdown modes that can occur when a grounded surface is separated from an energized surface by an electrical insulator. In the context of the present disclosure, the relatively high voltages applied to the source electrode 231 and / or extraction electrode 233 may be shielded from the isolation support 240 at the point where the isolation support 240 meets the source assembly 205. This shape may include ridges, ribs, baffles, or other shapes to physically shield the energized components of the exemplary ion source 200 from the grounded portion of the exemplary ion source 200.

[0054] The source assembly 205 may include a housing, such as an enclosure, with fittings for various inputs and outputs (e.g., fluid, optical, electrical, etc.), which at least partially isolates a relatively high-pressure environment near the resonator from a vacuum environment surrounding the source assembly 205. To that end, the resonator 230 may be at least partially disposed within the housing of the source assembly 205, but may also function as part of the housing, e.g., a support or substrate for the resonator 230 separating the relatively high-pressure environment from the vacuum environment (e.g., in the "inverted" design shown in FIG. 3B ). As described in more detail with reference to FIGS. 2B-3B , the source assembly 205 may include a spacer disposed between the resonator 230 and the source electrode 231, such that the various conduits and couplers described with reference to FIG. 2A may be disposed within the spacer or within the resonator 230, as opposed to a separate housing in which the resonator 230 is also disposed.

[0055] 2B is a schematic diagram illustrating an exemplary source assembly 250 according to some embodiments of the present disclosure. The exemplary source assembly 250 is one embodiment of the source assembly 205 of FIG. 2A. The exemplary source assembly 250 includes an electrical coupler 215 (e.g., a shielded coaxial coupling), a resonator 230, and a source electrode 231 disposed within an at least partially shielded housing 255. The exemplary source assembly 250 includes a spacer 275 disposed between the resonator 230 and the source electrode 231. The configuration shown in FIG. 2B is referred to as a "suspended" design of the source assembly 205, as opposed to the "inverted" design of FIG. 2A, and is further described with reference to FIG. 3A.

[0056] The extraction electrode 233 is shown substantially aligned with features of the source assembly 250 that together at least partially define an axis (e.g., axis B in FIG. 2A ), as described with reference to FIG. 2A . For example, the resonator 230 may define an aperture 260 that can function as the fluid delivery coupler 210. To that end, embodiments of the present disclosure include a region of relatively high pressure external to the source assembly 250 that drives a flow 280 of plasma precursor gas into a discharge region between the resonator 230 and the source electrode.

[0057] The source electrode 231 may define a charged particle extraction aperture 265 positioned relative to the extraction electrode 233 such that an extraction field emanating from the extraction electrode can draw charged particles (e.g., positive ions, negative ions, etc.) from the plasma generated in the discharge region into the FIB column. The extraction aperture 265 may be defined at least partially in a foil 270 fused to or formed from the bulk material of the source electrode 231. To that end, the source electrode 231 may include one, two, or more materials electrically coupled to each other (e.g., by welding or other techniques).

[0058] The aperture 265 may be characterized by a diameter of about 20 μm to about 200 μm (including subranges, fractions, and interpolations) and an aspect ratio of about 0.05 to about 0.5 (including subranges, fractions, and interpolations). Generally, the diameter of the aperture 265 may depend, at least in part, on the source beam current. Higher beam currents may define larger apertures in the source electrode 231.

[0059] Advantageously, including foil 270 as part of the source electrode allows extraction aperture 265 to have a smaller diameter for a given aspect ratio, which in turn may improve brightness and reduce the flow of neutral particles (e.g., vapor particles, gas particles, etc.) into the vacuum environment through extraction aperture 265. Furthermore, a relatively small aspect ratio may reduce the likelihood of ions recombining on the conductive surface of extraction aperture 265 in situations where the mean free path of ions in the vacuum environment may be larger than the diameter of extraction aperture 265.

[0060] The spacer 275 may be or include a substantially insulating and / or dielectric material configured to offset the resonator 230 from the source electrode 231, thereby defining a discharge volume through which charged particles can be extracted toward the FIB column. In some embodiments, the spacer 275 may be omitted, and the offset between the resonator 230 and one or more components of the source electrode 231 (e.g., foil 270) is defined by one or more retaining elements, such as the housing 255 and the isolation support 240.

[0061] 3A is a schematic diagram illustrating components of an exemplary ion source 300 according to some embodiments of the present disclosure. The illustrated components are arranged as part of the exemplary ion source 300 configured in a "suspension" design, whereby a flow of plasma precursor gas 301 is introduced across a resonator (e.g., resonator 230 of FIGS. 2A-2B ) via, for example, a resonator aperture or other fluid supply coupling (e.g., coupler 210 of FIGS. 2A ) formed in a substrate 305 of the resonator 230. The exemplary ion source 300 includes a resonator 230, a source electrode 330, an extraction electrode 335, a spacer 340, an RF power supply 345, a DC power supply 350, and a reference ground 355. The resonator 230 includes a substrate 305, a first conductive layer 320, and a second conductive layer 325. The resonator 230 defines an aperture 321 (eg, aperture 260 in FIG. 2B) that is substantially aligned with corresponding apertures 331 and 337 in the source electrode 330 and extraction electrode 335, respectively.

[0062] The discussion of the components of the exemplary ion source 300 focuses on the electrical subsystem. To that end, FIG. 3A omits one or more components of the exemplary ion source 300 that are discussed in more detail with reference to FIG. 2A . The substrate 305 may be or include a dielectric material, such as a ceramic material (e.g., quartz, silicon dioxide, titanium dioxide, etc.) or other insulating dielectric material. The substrate 305 may define a first side 310 and a second side 315 opposite the first side 310. The first conductive layer 320 may be configured to carry an alternating current (AC) signal (e.g., an RF signal between about 0.5 GHz and about 6.0 GHz (including sub-ranges, fractions, and interpolations)) and may be disposed on the first side 310 and directed toward the source electrode 330. In some embodiments, the AC signal may include an RF signal having a frequency between about 0.4 GHz and about 2.4 GHz (including sub-ranges, fractions, and interpolations). A second conductive layer 325 may be disposed on the second side 315. The second conductive layer 325 may be configured to be electrically coupled to a reference ground 355. Similarly, the source electrode 330 may be coupled to the reference ground 355 but may be biased with respect to the second conductive layer 325. The extraction electrode 335 may be biased with respect to the source electrode 330 by application of a DC bias voltage, for example, applied by a DC power supply 350.

[0063] In some embodiments, relative ground 355 may be a reference voltage rather than a true ground potential. For example, relative ground 355 may correspond to a voltage referred to as a "common" voltage applied to column components as part of improving the performance of the charged particle beam source (e.g., reducing aberrations, improving spot size, etc.). To that end, relative ground 355 may be a positive or negative voltage having a magnitude between about 0 V and about 100 kV (including fractions, subranges, and interpolations thereof). In an illustrative example, relative ground 355 may have a value in the range of about 0.5 kV to about 30 kV (including subranges, fractions, and interpolations).

[0064] FIG. 3B is a schematic diagram illustrating components of an exemplary ion source 360 ​​according to some embodiments of the present disclosure. As with FIG. 3A, the discussion of the components of the exemplary ion source 360 ​​focuses on the electrical subsystem. To that end, FIG. 3B omits one or more components of the exemplary ion source 360 ​​discussed in more detail with reference to FIG. 2A. The components shown are for an ion source configured with an “inverted” design, whereby a flow of plasma precursor gas 361 is introduced substantially parallel to the resonator (e.g., resonator 230 in FIGS. 2A-2B), for example, via a conduit 365 or other fluid supply coupling of the resonator formed in the spacer 340 (e.g., coupler 210 in FIGS. 2A). The exemplary ion source 360 ​​includes a resonator 230, a source electrode 330, an extraction electrode 335, a spacer 340, an RF power supply 345, a DC power supply 350, and a reference ground 355. The resonator 230 includes a substrate 305, a first conductive layer 320, and a second conductive layer 325. The resonator 230 defines an aperture 321 (e.g., aperture 260 in FIG. 2B) that is substantially aligned with corresponding apertures 331 and 337 in the source electrode 330 and extraction electrode 335, respectively.

[0065] The "inverted" design shown in FIG. 3B features a discharge region formed between the source electrode 330 and the resonator 230, whereby the first conductive layer 320 is disposed on the substrate 305 according to a pattern, as described in more detail with reference to FIGS. 4A-10D. The pattern includes a ring portion (shown and described with reference to subsequent figures) that defines a gap 370 between a first end 322 of the ring portion and a second end 323 of the ring portion. In contrast to the "suspended" design of FIG. 3A, the exemplary ion source 360 ​​omits an aperture formed through the substrate 305 and the second conductive layer 325. In some embodiments, the source electrode 330 is configured such that the extraction aperture 331 is oriented over the first end 322 or the second end 323, thereby offsetting the axis B of the exemplary ion source 360 ​​relative to the geometric center of the gap 370. Advantageously, orienting axis B to be substantially aligned with first end 322 or second end 323 may improve the performance of the exemplary ion source 360 ​​with respect to one or more characteristics of the source. For example, such an arrangement may increase source brightness, source power efficiency, and source operating pressure, among other advantages, compared to a configuration in which extraction aperture 331 is located approximately in the center of gap 370. Without being bound to a particular physical phenomenon or mechanism of action, the described technical advantages may be due, at least in part, to spatial variations in ion density resulting in relatively higher ion densities closer to first end 322 and / or second end 323 compared to the geometric center of gap 370.

[0066] The extraction aperture 331 may be formed in the foil 333 portion of the source electrode 330, as described in more detail with reference to FIGS. 2A-2B. The aperture 331 may be formed in the foil 333 using a variety of techniques, including ion beam patterning. For example, the foil 333 may include multiple apertures 331 and may be formed after the exemplary ion source 360 ​​is at least partially assembled. Advantageously, when one or more components of the exemplary ion source are subject to relatively high manufacturing variability, the extraction aperture 331 and portions of the resonator 230 may be aligned with improved precision.

[0067] 4A is a schematic diagram illustrating the operation of an exemplary optical emission spectroscopy system 400 including the ion source embodiment of FIGS. 2A-3B, according to some embodiments of the present disclosure. The exemplary optical emission spectroscopy (OES) system 400 introduces an analyte into a discharge region between a resonator and a source electrode, generates a plasma discharge 405 containing the analyte, and captures a characteristic photon flux (φ) from the analyte. OES ) from discharge 405 to spectrometer 410. Spectrometer 410 includes input optics 415 (e.g., a collimator, one or more lenses, etc.), diffraction optics 420 (e.g., a grating, a mirror, a distributed Bragg reflector (DBR), etc.), and detector 425 (e.g., a sensor array, a traversing sensor, etc.), which together may decompose composite photon beam 430 into one or more constituent beams 435 from which OES spectral data may be generated.

[0068] In the OES configuration shown in FIG. 4A , the analyte may be provided to the discharge region by one or more techniques, including as an atomized vapor (e.g., for liquid analytes), a gaseous vapor, and / or a solid (e.g., a crystalline solid or other powder form). To that end, the ion source 440 includes a fluid coupler 407 for introducing and / or removing the analyte from the discharge region. Advantageously, for OES operation, the exemplary system 400 may be configured to operate at or near atmospheric pressure, under vacuum, or at pressures above atmospheric pressure. In some cases, the operating pressure may be based, at least in part, on the nature of the analyte being processed and the corresponding discharge characteristics. For example, an analyte that has a relatively high ionization threshold energy and emits characteristic photons at a relatively high plasma pressure may exhibit that characteristic from operating the exemplary system 400 at near or above atmospheric pressure and at a relatively high plasma power. In contrast, if the analyte tends to decompose at high ionization rates (e.g., in a thermal plasma), exemplary systems may benefit from operating at relatively low plasma power, under vacuum, or in the presence of a relatively high proportion of neutral gas.

[0069] In the exemplary system 400, the ion source 440 is an example of the "inverted" design of FIGS. 2A and 3B in that the resonator 445 omits an aperture formed through the first conductive layer 450. The gap 455 defined in the first conductive layer 450 is substantially oriented with respect to the source electrode 460 so that a photon flux emanating from the discharge 405 is transmitted from the ion source 440 to the input optics 415 of the spectrometer 410. To that end, the source electrode 460 may be or include a material that is substantially transparent to photons in a predetermined spectral range (e.g., ultraviolet, visible, infrared, etc.) and is electrically conductive. Examples of such materials include indium tin oxide (ITO), among others. The ion source 440 includes a transparent portion 465 for such purpose.

[0070] 5A-11 , the exemplary system 400 embodiment omits a source electrode that relies on RF energy provided by an RF power supply 470 via an electrical coupler 471 to generate and sustain a discharge 405. The source electrode 460 may improve the performance of the ion source 440 by allowing for control of the discharge volume, for example, by expanding the discharge volume into the space between the source electrode 460 and the first conductive layer 450. Conversely, the source electrode 460 may also compress the discharge volume, thereby increasing plasma density and enhancing photon emission for some analytes.

[0071] FIG. 4B is a schematic diagram illustrating the operation of an exemplary optical absorption spectroscopy (OAS) system 475 including an embodiment of the ion source of FIGS. 2A-3B , in accordance with some embodiments of the present disclosure. The ion source 440 of the exemplary system 475 includes internal components and a power system that are the same as or similar to those described with reference to FIG. 4A . Fluid coupler 407 has been omitted from this description to focus on optical aspects. However, in some embodiments, for example, when the ion source 440 is configured as a sealed light source (e.g., a calibrated light source) for OAS applications, the fluid coupler 407 may be included or omitted entirely. Thus, the exemplary system 475 includes optical elements not present in the exemplary system 400 of FIG. 4A , such as beam splitter optics 480, which may be or include mirrors disposed on a turret or partially transmitting mirrors that configure the exemplary system 475 to pass a test beam of photons through an analysis cell 485 and a reference beam of photons through a reference cell 487, for example, as part of an OAS procedure. Exemplary system 475 is shown with separate cells 485 and 487 for use in a calibrated OAS system that can be used with unknown samples. In embodiments of the present disclosure, one or more of the illustrated elements may be omitted, for example, if the system is configured for a known analyte (e.g., as part of a quality control procedure), so that the reference beam path can be omitted. In some embodiments, exemplary system 475 may be configured as an ultraviolet-visible OAS system, in which case ion source 440 may be configured to generate an electrical discharge 405 that promotes the emission of photons in the UV-visible spectral range (e.g., using mercury vapor for UV photons).

[0072] 4C-4D are schematic diagrams illustrating the operation of an exemplary volumetric plasma system 490 including an embodiment of the ion source of FIGS. 2A-3B , according to some embodiments of the present disclosure. The exemplary system 490 is configured to expose a sample 130 to a discharge 405 as part of one or more procedures (e.g., coupling to a sample stage 125) for preparing the sample for introduction into the vacuum chamber 120 of the exemplary system 100, as described in more detail with reference to FIG. 1 . Examples of such procedures include, but are not limited to, volumetric plasma cleaning, ion etching, electron etching, plasma-based coating, ion sputtering, etc. The exemplary system 490 includes a load lock chamber 491 separated from the vacuum chamber 120 by a valve 493 (e.g., a gate valve) in which an ion source 440 is disposed, and the sample 130 is disposed on a conductive substrate 460 that serves as at least a portion of a source electrode (e.g., a stub or other sample holder) when electrically coupled to a relative ground or a DC voltage source. The sample 130 can be disposed in the ion source 440 using one or more sample manipulation tools 497 via a vacuum feedthrough 499, which allows the sample 130 to be exposed to the discharge 405 and then transferred to the sample stage 125. Alternatively, the sample stage 125 can be configured to have a range of movement that extends across the load lock chamber 491 and / or the vacuum chamber 120. In this manner, the sample 130 can be coupled to the sample stage 125 (e.g., via a substrate 460), which allows the sample stage 125 to be moved to a cleaning position that is different from the imaging position of the charged particle microscope, as shown in FIG. 4D . In this context, the cleaning position can be located within the vacuum chamber 120 or the load lock chamber 491, which allows the cleaning process (e.g., exposure to a plasma generated as described with reference to FIG. 4C ) to occur at a position some distance from the beam axis of the charged particle beam column and the sensitive optics (e.g., axes A and B in FIG. 1 ). In some embodiments, movement of sample 130 is accomplished automatically or semi-automatically, but may also be accomplished manually.

[0073] 5A-5C are schematic diagrams illustrating components of an exemplary resonator 500 representing one embodiment of the ion source of FIGS. 2A-4C including a single split-ring resonator, according to some embodiments of the present disclosure. The discussion of the components of the exemplary resonator 500 focuses on the patterning of the elements of the resonator 500 as well as the electrical subsystem to which the resonator is electrically coupled. To that end, FIGS. 5A-5C omit one or more components of the exemplary ion source discussed in more detail with reference to FIGS. 2A-4C. The exemplary resonator 500 includes a substrate 505. The substrate 505 defines a first side 507 and a second side 509. The exemplary resonator 500 includes a first conductive layer 510 disposed on the first side 507. The first conductive layer 510 is disposed according to a pattern including a ring portion 515. The pattern further defines a gap 520 in the ring portion 515 of the first conductive layer 510. The second side 509 is opposite the first side 507 relative to the two substantially planar surfaces of the substrate 505. The exemplary resonator 500 includes a second conductive layer 525 disposed on the second side 509.

[0074] The exemplary resonator 500 is shown as an embodiment of an “inverted” design in FIGS. 2A and 3B . To that end, the exemplary resonator 500 omits an aperture formed through the substrate 505. However, in some embodiments, the substrate 505 defines an aperture extending from the first side 507 to the second side 509. The aperture may be defined in the substrate 505 at substantially the same location as the gap 520 (e.g., as part of a “suspended” design), but may also be defined elsewhere, such as within the perimeter of the ring portion 515, outside the ring portion 515, etc. In this manner, the aperture may function as a fluid supply coupler (e.g., fluid supply coupler 210 in FIG. 2A ) to supply one or more precursors 530 to the vicinity of the gap 520. In the “inverted” design of FIG. 2A or FIG. 3B , the precursor flow may be substantially parallel to the first side 507. In some embodiments, a fluid supply coupler may be included at a location away from the gap 520 to supply the precursor 530 through the substrate 505 and / or the second conductive layer 525 while maintaining a flow profile that is substantially parallel to the first side 507 near the gap 520.

[0075] 5A is shown as substantially circular, it may take on alternative shapes and / or form factors based at least in part on constraints such as geometric constraints imposed by the enclosure and the interrelationship between the shape of the ring portion and the operating frequency of the AC power signal used to ignite and sustain the discharge. As such, the radius of ring portion 515 may depend at least in part on its angular position θ relative to input point 535. Without being bound to a particular physical mechanism or principle of operation, the pattern in which first conductive layer 510 is disposed on first side 507 may be based at least in part on the operating frequency of example resonator 500.

[0076] For example, the pattern may define an input point 535 within ring portion 515 at a first fractional position α on ring portion 515. As shown in FIG. 5B , fractional position α is a ratio of a first path length S1 between gap 520 and input point 535 in a first direction to a second path length S2 between gap 520 and input point 535 in a second direction different from the first direction. Fractional position α may be related to an angle (e.g., outside of 360 degrees or 2π radians) of ring portion 515 that is substantially circular (although the angular description may be less meaningful for non-circular patterns of ring portion 515, such as a racetrack-shaped ring portion 515 or other configurations where the radius of the shape is a function of angle θ), in which case light rays extending from input point 535 and gap 520 cannot intersect at the geometric center of ring portion 515.

[0077] In the general formula, the fractional position α is

number

[0078] While the value of ∞ has no physical meaning, the above equations reveal that fractional positions having values ​​greater than 1 correspond to positions on ring portion 515 where negative values ​​of θ correspond to functional configurations of input point 535 relative to gap 520. In this manner, a given fractional position may correspond to two well-matched configurations. In some embodiments, values ​​of fractional position α between about −1 and about 1 are effective for providing resonator 500 that is well-matched for a given set of operating parameters and plasma conditions. For example, in the absence of a discharge (e.g., pre-ignition conditions), fractional positions greater than about 0.4 (e.g., closer to or approximately equal to 1) result in two functional configurations corresponding to positive values ​​of θ and corresponding negative values ​​of θ. For at least this reason, values ​​of fractional position α may be expressed as positive values ​​derived using the magnitude (e.g., absolute value) of θ and / or the unsigned values ​​of S1 and S2. In other words, the “direction” of the signed θ may be understood to be defined relative to input point 535 or gap 520. In some embodiments, for example, the fractional position 1, corresponding to θ=π, may result in relatively poor power transfer into the gap 520 when typical 50Ω impedance hardware is used in the power circuit driving the resonator 500, which is associated with the input impedance of the resonator 500 approaching a value of zero.

[0079] In the context of the exemplary resonator 500, the operating frequency refers to a characteristic frequency of an AC power signal that can be provided to the ring portion 515 by the power circuit shown in FIG. 5C , which can include an RF power source 545 coupled to the ring portion 515 via an electrical coupler 540 in electrical contact with the input point 535. In this context, the RF power source 545 is operatively coupled to the resonator 500, configured to generate different power signals based, at least in part, on the presence or absence of a discharge 550. For example, as an approach to reducing and / or substantially eliminating reflected power as conditions within the discharge volume change, a first power signal that is well matched in the absence of a discharge and configured to ignite the discharge 550 can be provided to the first conductive layer 510, followed by one or more changes to the power electronics. The exemplary resonator 500 with a single input point 353 relies on modifying the impedance matching network to accommodate changes in reflected power without damaging the microwave amplifier.

[0080] Advantageously, embodiments of the present disclosure described with reference to subsequent figures are configured to provide a well-matched impedance condition without relying on a dynamic matching network. In this context, the term "well-matched" is used to refer to a condition in which little or substantially no reflected power is measured at the RF power source during operation with a predetermined power signal. The exemplary resonator 500 can be driven by an RF power source 545 as part of an ion beam source, as described in more detail with reference to FIGS. 2A-3B , and includes a source electrode 555 and an extraction electrode 560 for extracting the ion beam toward a FIB column (e.g., FIB column 111 of FIG. 1 ).

[0081] 6A-6C are schematic diagrams illustrating components of an exemplary resonator 600, including a bias tee 640, representing an embodiment of the ion source of FIGS. 2A-5C including a single split-ring resonator, in accordance with some embodiments of the present disclosure. The discussion of the components of the exemplary resonator 600 focuses on the patterning of the elements of the resonator 600, as well as the electrical subsystem to which the resonator is electrically coupled. To that end, FIGS. 6A-6C omit one or more components of the exemplary ion source discussed in more detail with reference to FIGS. 2A-5C. The exemplary resonator 600 includes a substrate 605. The substrate 605 defines a first side 607 and a second side 609. The exemplary resonator 600 includes a first conductive layer 610 disposed on the first side 607. The first conductive layer 610 is disposed according to a pattern including a ring portion 615. The pattern further defines gaps 620 in the ring portion 615 of the first conductive layer 610 that are exposed to precursors provided by one or more flows 630 of precursor fluid (e.g., gas, vapor, etc.). The second side 609 is opposite the first side 607 relative to the two substantially planar surfaces of the substrate 605. The exemplary resonator 600 includes a second conductive layer 625 disposed on the second side 609.

[0082] The bias tee 640 may comprise a portion of the first conductive layer 610, as shown in FIGS. 6A-6B, or may be a separate conductive element electrically coupled to the first conductive layer 610 at input point 635 via an electrical coupler 645, as shown in FIG. 6C. The bias tee 640 may modulate the offset voltage of an RF power signal that an ion source including the exemplary resonator 600 (e.g., whose electrical components are shown in FIG. 6C) provides to the first conductive layer 610. In this context, offset voltage refers to a voltage that modifies the average voltage of the RF power signal and may be measured in various ways (e.g., average voltage, etc.). Advantageously, applying a bias voltage, such as a DC bias voltage generated by a DC power supply 650, to the RF power signal generated by the RF power supply 655 has been shown to improve the performance of the disclosed resonators as ion sources, based at least in part on measurements of an increase in ion flux passing through the source electrode 660 and / or extraction electrode 665, for a given RF power and other parameters that are substantially consistent.

[0083] 7A-7C are schematic diagrams illustrating an exemplary resonator 700 including multiple ring portions 715, representing one embodiment of the ion source of FIGS. 2A-5C , in accordance with some embodiments of the present disclosure. The discussion of the components of the exemplary resonator 700 focuses on the patterning of the elements of the exemplary resonator 700, as well as the electrical subsystem to which the resonator is electrically coupled. To that end, FIGS. 7A-7C omit one or more components of the exemplary ion source discussed in more detail with reference to FIGS. 2A-5C . The exemplary resonator 700 includes a substrate 705. The substrate 705 defines a first side 707 and a second side 709. The exemplary resonator 700 includes a first conductive layer 710 disposed on the first side 707. The first conductive layer 710 is disposed according to a pattern including a first ring portion 715-1 and a second ring portion 715-2. The pattern further defines a first gap 720-1 in the first ring portion 715-1 of the first conductive layer 710 and a second gap 720-2 in the second ring portion 715-2. The second side 709 is opposite the first side 707 with respect to the two substantially flat surfaces of the substrate 705. The exemplary resonator 700 includes a second conductive layer 725 disposed on the second side 709. Referring to the resonator of FIGS. 5A-5C , the first ring portion 715-1 defines the first gap 720-1 at a first fractional position α. ​​The second ring portion 715-2 defines the second gap 720-2 at a second fractional position β. The values ​​of the respective fractional positions α and β can be equal or different. In some embodiments, one or more dimensional characteristics of the first ring portion 715-1 and the second ring portion 715-2, such as the thickness of the first conductive layer 710 in each ring portion 715, may differ. For example, the thickness of the first conductive layer 710 in the first ring portion 715-1 may be greater or less than the thickness of the second ring portion 715-2 as an approach to compensating for the effect of fractional position on the characteristic impedance of each ring portion 715. In some embodiments, one or more of the ring portions 715 may include a tapered portion at a first end 721 and a second end 723 near the respective gap 720, as shown in FIG. 7A for the first gap 720-1.Without being bound by any particular physical mechanism or operating principle, tapering the ring portions 715 may be an approach to improve the transfer of discharge from one ring portion 715 to the other ring portion 715 by localizing the formation of discharge closer to the corresponding gap of the corresponding ring portion 715, thereby maintaining a well-matched impedance condition.

[0084] In operation as part of an ion source of the present disclosure (e.g., ion source 110 of FIG. 1 ), the exemplary resonator may switch between two or more operating modes. The first mode may be characterized by a set of operating parameters (e.g., operating pressure, gas composition, RF power signal, etc.) configured to facilitate ignition of a discharge in the first gap 720-1. The second mode may be characterized by a set of operating parameters configured to sustain a discharge in the second gap 720-2. To that end, the exemplary resonator 700 may be configured to ignite a discharge in the first gap 720-1 by operating in the second mode and maintain and / or sustain a discharge in the second gap 720-2 by operating in the first mode, based at least in part on switching between the first and second modes (e.g., in response to ignition of a discharge), as described in more detail with reference to FIG. 11 .

[0085] The respective fractional positions α and β may be defined so that a single RF power source 655 (shown in FIG. 7C ) can provide well-matched impedance conditions in the presence and / or absence of discharges in the first gap 720-1 and / or the second gap 720-2. In some embodiments, the fractional positions α and β may be defined to space the gaps 720 closely to one another, with the respective input points 735 defined taking into account geometric constraints of the resonator 700 (e.g., packaging constraints, shielding requirements, etc.). As described with reference to FIGS. 5A-5C , the fractional positions α and β may have values ​​ranging from about 0 to about 1 (including fractions, interpolations, and subranges thereof), with values ​​of about 0.4 to about 1 being used in the first operating mode and values ​​of about 0 to about 1 being used in the second operating mode, including fractions, interpolations, and subranges thereof, or corresponding “negative” configurations described with reference to FIGS. 5A-5B . In some embodiments, the fractional position values ​​for the second mode are smaller than the fractional position values ​​for the first mode.

[0086] In some embodiments, the exemplary resonator 700 is electrically coupled to one or more RF power sources 750 via respective electrical couplers 745, as shown in Figures 7B-7C. Using separate RF power sources can reduce the need for dynamic matching circuits, with each respective power source configured to generate a specific power signal used for one of the operating modes. This approach, which provides well-matched impedance conditions for each mode, may increase the cost of the ion source compared to systems that include a switching circuit 755 configured to direct an RF power signal to the first input point 735-1 or the second input point 735-2 by reversibly coupling the power source 750 to the first ring portion 715-1 or the second ring portion 715-2 based at least in part on one or more characteristics of the operating conditions of the exemplary resonator 700, such as the presence or absence of a discharge.

[0087] In the illustrative example, the switching circuit 755 may include electrical components that switch to the second input point 735-2 in response to a change in current and / or reflected power from the first ring portion 715-1 (e.g., indicating the ignition of a discharge). In such a case, the overall configuration of the illustrative resonator 700 (e.g., the design of the pattern in which the first conductive layer 710 is formed) may enable the RF power source 750 to provide a substantially consistent RF power signal to the second ring portion 710-2 via the second input point 735-2, which may ignite a discharge in the first gap 720-1 and travel to the second gap 720-2. In the presence of a discharge, the switching circuit 755 may couple the RF power source 750 to the second ring portion 715-2 via the second input point 735-2. This approach of using switching circuitry 755 and multiple ring segments 715 may reduce the need for dynamic power electronics (e.g., complex RF power supplies, matching circuits, large heat sinks, etc.), providing advantages to embodiments of the present disclosure in terms of at least robustness, reduced complexity, reduced economic cost, and reduced physical size compared to other ion beam source systems. Such advantages are further complemented by significant improvements in power consumption, gas flow rates, cost, and manufacturing complexity, among other improvements, compared to common FIB source technologies (e.g., ICP, etc.).

[0088] 8A-8B are schematic diagrams illustrating an exemplary resonator 800 including multiple ring portions 815, representing an embodiment of the ion source of FIGS. 7A-7C including a bias tee 820, according to some embodiments of the present disclosure. As described in more detail with reference to FIGS. 6A-6C, the bias tee 820 may improve the performance of the exemplary resonator 800 as an ion source for FIB applications. This improvement may be based, at least in part, on modulating and / or controlling the voltage offset of an RF power signal used to ignite and / or sustain the discharge from which ions are extracted, as described in more detail with reference to FIGS. 2A-7C. The discussion of the components of the exemplary resonator 800 focuses on the patterning of the elements of the exemplary resonator 800, as well as the electrical subsystem to which the resonator is electrically coupled. To that end, FIGS. 8A-8B omit one or more components of the exemplary ion source discussed in more detail with reference to FIGS. 2A-7C. Additionally, some elements described with reference to Figures 2A-7C (e.g., second conductive layer 725 in Figure 7A) are not listed to focus on describing the bias tee 820 and the pattern of the multiple ring portions.

[0089] The exemplary resonator 800 includes a substrate 805 having a conductive layer 810 disposed on one side thereof. The conductive layer 810 is arranged according to a pattern defining a first ring portion 815-1 and a second ring portion 815-2. A first gap 817-1 is defined in the first ring portion 815-1, and a second gap 817-2 is defined in the second ring portion 815-2. A bias tee 820 is electrically coupled to the second ring portion 815-2 via a second input point 825-2. The bias tee 820, the second input point 825-2, and the first input point 825-1 are electrically coupled to respective electrical couplers 830, as described in more detail with reference to FIGS. 2A-2B. First ring portion 815-1 assumes a non-circular form factor that is a "racetrack" figure defined by the compound curves of the conductive material of first conductive layer 810. Advantageously, such a non-circular shape may improve the performance of one or more of ring portions 815, for example, by accommodating geometric and fractional position constraints imposed by the physical housing and / or operating frequency constraints for maintaining one or more resonant modes within corresponding gap 817.

[0090] 8B illustrates the power system and switching electronics in a dual ring configuration for the exemplary resonator 800. The electrical components include an RF power supply 835 coupled to the exemplary resonator 800 via a switching circuit 840 and a DC power supply 845 coupled to the exemplary resonator via a bias tee 850. The exemplary resonator 800 is configured to ignite and sustain a discharge in a discharge volume between a substrate 805 and a source electrode 855, from which charged particles may be extracted by an extraction electrode 860, as described in more detail with reference to FIGS.

[0091] 6A-7C, the switching circuit 840 may be configured to direct an RF power signal to the exemplary resonator 800 while switching between the first input point 825-1 and the second input point 825-2 based at least in part on the presence of a discharge within the discharge volume, as described with reference to FIG. 11. To that end, each of the respective ring segments 815 may be configured to perform functions such as igniting a discharge in the absence of a discharge or sustaining a discharge in the presence of a discharge while maintaining well-matched conditions for impedance and reflected power of the discharge circuit based at least in part on the different fractional positions defined for each ring segment 815. The bias tee 850 may then be configured to modulate the voltage offset of the RF power signal as an approach to control and / or increase the operating range of the charged particle flux extracted by the extraction electrode 860.

[0092] 9A-9D are schematic diagrams illustrating components of an exemplary resonator 900 representing one embodiment of the ion source of FIGS. 2A-4C , including a single split-ring resonator and multiple input points 920, in accordance with some embodiments of the present disclosure. The discussion of the components of the exemplary resonator 900 focuses on the patterning of the elements of the resonator 900, as well as the electrical subsystem to which the resonator is electrically coupled. To that end, FIGS. 9A-9C omit one or more components of the exemplary ion source discussed in more detail with reference to FIGS. 2A-4C . The exemplary resonator 900 includes a substrate 905. The substrate 905 defines a first side 907 and a second side 909. The exemplary resonator 900 includes a first conductive layer 910 disposed on the first side 907. The first conductive layer 910 is disposed according to a pattern that includes a ring portion 915. The pattern defines a plurality of input points 920, including a first input point 920-1 and a second input point 920-2. The pattern further defines gaps 925 in the ring portion 915 of the first conductive layer 910. The second side 909 is opposite the first side 907 with respect to the two substantially flat surfaces of the substrate 905. The exemplary resonator 900 includes a second conductive layer 930 disposed on the second side 909.

[0093] Advantageously, the multi-input resonator illustrated in FIGS. 9A-9D can benefit from improved discharge stability and reduced geometric size by combining the functionality of multiple ring segments 915 into a single ring segment 915. As with other embodiments of the present disclosure, the ring segment 915 can be circular or non-circular, based at least in part on the space constraints of the charged particle source system into which the exemplary resonator 900 is integrated. To that end, the discussion regarding fractional positions provided with reference to FIGS. 5A-8B applies to the position of the input point 920 relative to the position of the gap 925 on the ring segment 915. For example, a first input point 920-1 can be formed at a first fractional position α on the ring segment 915. A second input point 920-2 can be formed at a second fractional position β on the ring segment 915. A third input point 920-3 can be formed at a third fractional position γ on the ring segment 915. In some embodiments, β is greater than α. In some embodiments, γ is greater than both β and α.

[0094] In this context, the different fractional positions allow the example resonator 900 to operate under different operating regimes, such as pre-ignition in the absence of a discharge, post-ignition in the presence of a discharge, with a variety of discharge mixtures that can exhibit different electronic characteristics associated with different RF power signals and different input point 920 locations on the ring portion. Additionally, the example resonator 900 can be configured to provide well-matched impedance conditions for each operating mode through the fractional positions of the respective input points 920. In some cases, each mode can be associated with a different RF power signal.

[0095] As described in more detail with reference to FIGS. 5A-8B, the exemplary resonator 900 may be configured to ignite and sustain a discharge (e.g., discharge 550 of FIG. 5C) near the gap 925. As described in more detail with reference to FIGS. 2A-3B, the exemplary resonator 900 may be electrically coupled to one or more power systems, such as an RF power supply 965, a DC power supply 960, etc., via one or more electrical couplers 935. To that end, the exemplary resonator 900 is shown with an input 920 coupled to a control circuit 955. The control circuit 955 is configured to adapt and / or modify the operation of the exemplary resonator based at least in part on the ignition of the discharge as part of maintaining well-matched conditions and / or substantially consistent brightness as a charged particle beam source. To that end, control circuitry 955, an example of which is shown in detail in FIG. 9C , may include one or more sets of electrical components 975 electrically coupled to DC power source 960 and configured to respond to changes in one or more operating parameters of the exemplary resonator, at least in part, by modifying which of input points 920 receive the RF power signal generated by RF power source 965.

[0096] In an illustrative example of a dual-input resonator 970, which is one embodiment of the exemplary resonator 900, the first input point 920-1 and the second input point 920-2 are each coupled to an RF power source 965 via electrical components 975 including diodes (e.g., PIN diodes) and capacitors, and to a DC power source via components 975 including resistor and inductor pairs. In some embodiments, the electrical components 975 may include two or more diodes (e.g., four PIN diodes in the case of the dual-input configuration of FIG. 9C ) coupled to each input point 920. Similarly, each input point may be coupled to the DC power source 960 via one or more inductors, resistors, or other electrical components 975. A control circuit 955 configured in this manner may respond to changes in reflected power caused by ignition of a discharge at or near the gap 925 by redirecting the RF power signal from the first input point 920-1 to the second input point 920-2. To that end, the second input point 920-2, configured as the input point 920 responsive to the presence of a discharge, is equipped with a bias tee, as described in more detail with reference to Figures 6A-6C. In the example of the dual-input resonator 970, three DC power supply 960 units are shown, but the system may include more or fewer (e.g., one DC power supply to bias the resistor and inductor pair and apply a voltage offset to the second input point 920-2). To that end, the DC power supply 960 may include voltage regulation subcircuits that enable it to output different voltages and / or currents to different components 975 and / or input points 920.

[0097] The exemplary resonator 900 may be integrated into a charged particle beam system (e.g., as part of the FIB source 110 of FIG. 1 ) oriented relative to a source electrode 980 and an extraction electrode 985. The resonator 900, source electrode 980, and extraction electrode 985 are electrically coupled to power and control circuitry as described with reference to FIGS. 1-8B. In this manner, the charged particle beam system may generate a beam of charged particles (e.g., ions) that can be focused onto a sample to generate characteristic data for imaging and / or microanalysis.

[0098] 10A-10C are schematic diagrams illustrating components of an exemplary resonator 1000 representing one embodiment of the ion source of FIGS. 2A-4C including a multi-pole resonant structure, according to some embodiments of the present disclosure. The discussion of the components of the exemplary resonator 1000 focuses on the patterning of the elements of the resonator 1000. To that end, FIGS. 10A-10C omit one or more components of the exemplary ion source discussed in more detail with reference to FIGS. 2A-9D . The exemplary resonator 1000 includes a substrate 1005. The substrate 1005 defines a first side 1007 and a second side 1009. The exemplary resonator 1000 includes a first conductive layer 1010 disposed on the first side 1007. The first conductive layer 1010 is arranged according to a pattern including a plurality of ring portions 1015. The pattern defines input points 920 that couple the first conductive layer 1010 to an electrical coupler 1040. The ring segments 1015 are coupled to the input points via respective input traces 1030 at respective ring junctions 1035. The pattern defines a plurality of ring segments 1015 such that there are twice as many gaps 1025 defined as there are ring segments 1015. In the exemplary resonator 1000, the first ring portion 1015-1 and the second ring portion 1015-2 together define a first gap 1025-1 between the first end 1050-1 and the second end 1050-2 of the first ring portion 1015-1 (see FIG. 10B), a second gap 1025-2 between the first ring portion 1015-1 and the second ring portion 1015-2, a third gap 1025-3 between the first end 1055-1 and the second end 1055-2 of the second ring portion 1015-2 (see FIG. 10B), and a fourth gap 1025-4 between the second ring portion 1015-2 and the first ring portion 1015-1. The second side 1009 is opposite the first side 1007 relative to the two substantially planar surfaces of the substrate 1005. The exemplary resonator 1000 includes a second conductive layer 1045 disposed on the second side 1009.

[0099] Without being bound by any particular physical mechanism or principle of operation, the dipole generator structure of a conventional split-ring resonator device, in contrast to the ion source of the present disclosure, may apply a time-varying electric field at the location where ions are extracted (e.g., near the gap in the ring structure). Applying a time-varying electric field may result in energy transfer from electrons in the discharge to ions in the discharge as part of a partial thermalization process, effectively "heating" ions within the discharge region. While this may be considered beneficial in some ways, e.g., by increasing the average energy of ions and potentially increasing ion flux, the increased ion temperature may also degrade the internal structure of the ion source (e.g., through ion bombardment), increase the flux of neutral atoms and / or molecules into the column (e.g., in the form of "entrainment"), and potentially degrade precursors by promoting plasma dissociation mechanisms.

[0100] Advantageously, the multipole resonator embodiments shown in Figures 10A-10D can be configured to generate a substantially electric field-free region within at least a portion of the discharge volume by generating a discharge at least in part between the ring portions 1015 (e.g., near the gaps 1025). Figures 10A-10B show a quadrupole embodiment having four ends 1050-1, 1050-2, 1055-1, and 1055-2 disposed on the first conductive layer 1010. Figures 10C-10D show a hexapole (with three ring portions 1015 and six gaps 1025) and an octupole (with four ring portions 1015 and eight gaps 1025) embodiment having six ends 1050, 1055, 1060, and eight ends 1050, 1055, 1060, and 1065, respectively, disposed on the first conductive layer 1010. The exemplary resonator 1000 can be configured to provide substantially equal voltages at opposite ends of the quadrupole structure (e.g., first end 1050-1 and second end 1055-2) across multiple phases of an AC power signal (e.g., an RF power signal). In this manner, the electric field at a central location between the multipole ends 1050 and 1055 remains substantially zero in the presence of a discharge.

[0101] A plasma generating structure in which the electric field remains substantially zero at one or more locations within the plasma discharge region can produce a nonthermal plasma in which the average ion temperature is significantly lower than the average electron temperature, at least in part by limiting the energy transfer between ions and electrons and by limiting the acceleration of ions within the plasma due to the electric field within the gap. Maintaining a relatively low average ion temperature improves FIB source technology and, at least in part, increases the brightness of the beam extracted from the ion source. In some cases, reducing the ion temperature within the plasma can narrow the energy distribution of the ion beam, narrow the angular distribution downstream of the extraction electrode (e.g., extraction electrode 233 in FIG. 2A or 2B, extraction electrode 335 in FIG. 3A or 3B), and / or limit contamination of the ion beam with material from the ion source itself (e.g., due to degradation of structures within the source due to ion bombardment).

[0102] By carefully adjusting the microwave phase and voltage signals across the high-order multipole, a zero-field node can be created between the ring portions 1015 (e.g., using a microwave drive frequency of about 1.0 GHz to about 1.5 GHz (including fractions, subranges, and interpolations thereof) and a drive power of about 0.1 W to about 10 W (including fractions, subranges, and interpolations thereof). Such conditions can reduce and / or substantially eliminate transverse heating of ions due to electric field acceleration, leaving momentum transfer with electrons and other particles as the primary heating mechanism. Due to the reduced average temperature of ions in the discharge, the resonators of the present disclosure can exhibit improved brightness of FIB sources.

[0103] 11 is a block flow diagram illustrating an exemplary process for extracting a beam of ions from a discharge, according to some embodiments of the present disclosure. One or more operations comprising exemplary process 1100 may be performed by a computer system or other programmable logic machine operatively coupled with components of a charged particle microscope (e.g., charged particle beam system 100 of FIG. 1) and / or additional systems or subsystems, including, but not limited to, a characterization system, a power supply system, a network infrastructure, a database, and / or a user interface device. To that end, the operations of exemplary process 1100 may be stored as machine-executable instructions on one or more machine-readable media.

[0104] One or more operations of the exemplary process 1100 may be repeated, reordered, and / or omitted, for example, as part of extracting an ion beam from a discharge generated using the ion source of the present disclosure. To that end, the operations of the exemplary process 1100 are described as being performed by a system, and it should be understood that the operations may include generating and communicating control signals between a processor or other logic circuitry and electronic or electromechanical elements of a charged particle beam system. The operations of the exemplary process 1100 are described in the context of an electron microscope for clarity. Embodiments of the present disclosure include processes for generating monoenergetic ion beams, as well as other charged particle configurations, such as dual beam systems. The exemplary process 1100 omits one or more operations that may precede and / or follow the operations of the exemplary process 1100. For example, an operation may include drawing and maintaining a vacuum in a vacuum enclosure (e.g., vacuum enclosure 235 of FIG. 2A ) in which the ion source operates. Similarly, operation can include one or more control schemes (eg, feedback, feedforward, etc.) that allow the system of the present disclosure to adjust one or more operating parameters of the ion source.

[0105] In operation 1105, the exemplary process 1100 includes generating a microwave power signal. Generating the power signal may include operating an RF power source (e.g., RF power source 345 of FIG. 3A ) as described with reference to the previous figures. For example, the RF power signal may have a power of about 0.1 W to about 30 W (including fractions, subranges, and interpolations thereof). The RF power signal may have a frequency of about 100 MHz to about 5 GHz (including fractions, subranges, and interpolations thereof). Due at least in part to the highly coupled nature of discharge operation, where multiple physical and electrical phenomena interact to create a highly nonlinear environment, predictive and / or analytical control schemes may be difficult, if not impossible, to formulate. To that end, while it is generally possible to state that higher power can generate a brighter discharge under some circumstances (e.g., one set of operating conditions), higher power can also degrade performance and potentially contaminate the beam due to effects such as thermalization, plasma density, and ionization rate, as described in more detail with reference to FIGS. 10A-10D. Similarly, resonant modes of the electric field within the gap (e.g., gap 370 in FIG. 3B ) are strongly coupled to the geometric pattern defining the first conductive layer (e.g., first conductive layer 320 in FIG. 3B ), which can limit the operating frequency to one or more subranges in which resonant modes capable of igniting and / or sustaining a discharge are generated. In some embodiments, a single RF power signal is generated in the presence and absence of a discharge. In some embodiments, multiple RF power signals are used to distinguish between the presence and absence of a discharge. In some embodiments, the RF power signal is modulated during one or more operations of exemplary process 1100, e.g., as part of a control scheme configured to maintain a substantially constant brightness of the ion source while maintaining well-matched conditions in the presence and / or absence of a discharge.

[0106] In operation 1110, the exemplary process 1100 includes igniting a discharge using an ignition input point (e.g., first input point 735-1 in FIG. 7A , first input point 825-1 in FIG. 8A , first input point 920-1 in FIG. 9A ). Embodiments of the present disclosure include multi-ring, multi-point, and multi-pole resonators, which may include multiple input points at different locations within the first conductive layer. As described in more detail with reference to FIGS. 5A-10D , based at least in part on identifying an ignition input point (e.g., for an RF power signal in the absence of a discharge) and a maintenance input point (e.g., for an RF power signal in the presence of a discharge), a control and / or switching circuit (e.g., switching circuit 755 in FIG. 7C , switching circuit 840 in FIG. 8B , control circuit 955 in FIG. 9C , etc.) may be configured to direct the RF power signal generated in operation 1105 toward the ignition input point, up to until ignition is detected, as described in more detail with reference to FIG. 9C .

[0107] In operation 1115, the exemplary process 1100 includes sustaining the discharge using a maintenance input point (e.g., second input point 735-2 in FIG. 7A , second input point 825-2 in FIG. 8A , second input point 920-2 in FIG. 9A ). Embodiments of the present disclosure include a control circuit configured to respond to the ignition of the discharge in operation 1110 by redirecting the RF power signal generated in operation 1105 toward the maintenance input point. To reduce the risk of damage due at least in part to reflected power resulting from poorly matched discharge conditions, the response time of the control circuit may be improved by using a power circuit including hardwired components, as described with reference to FIG. 9C . In some embodiments, one or more additional or alternative control schemes are implemented using measured parameters of the ion source of the present disclosure, along with concurrent and / or subsequent computational processes. In one example, brightness measurements downstream of the extraction electrode (e.g., extraction electrode 335 in FIGS. 3A-3B ) can be used to modulate the DC offset voltage and / or RF power, but may also be used to identify when a discharge is present. In this manner, measurements and calculations may be used in conjunction with, or instead of, the circuit element-based techniques described with reference to FIG. 9C.

[0108] In operation 1120, the exemplary process 1100 includes generating a beam of charged particles. In some embodiments, extracting the beam of charged particles may include energizing an extraction electrode to extract the charged particles from the discharge (e.g., by electrostatic attraction) through an aperture in a source electrode (e.g., aperture 265 in FIG. 2B , aperture 331 in FIGS. 3A-3B ) that constitutes part of the ion source. These principles are described in more detail with reference to FIGS. 2A-3B . Energizing the extraction electrode may include applying a DC voltage to the electrode, as described with reference to FIGS. 5C-9D , but may also include applying an AC voltage or an intermittent voltage to the extraction electrode (e.g., as part of a pulsed scheme).

[0109] In operation 1125, the exemplary process 1100 includes applying an offset voltage to the RF power signal. The offset voltage may be applied using a bias tee (e.g., bias tee 640 of FIGS. 6A-6C), as described in more detail with reference to FIGS. 6A-6C, 8A-8C, and 9C. The offset voltage may provide an additional control parameter that can modulate the brightness of the ion source of the present disclosure with little or no effect on the matching conditions of the discharge circuit. Embodiments of the present disclosure include applying an offset voltage to the power signal applied as part of operations 1110 and 1115 (e.g., in the presence and absence of a discharge). To that end, the offset voltage can aid in ignition of the discharge as well as be used to modulate the discharge after ignition.

[0110] In the preceding description, various embodiments have been described. For purposes of interpretation, specific configurations and details have been set forth to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that embodiments may be practiced without the specific details. Additionally, well-known features may have been omitted or simplified so as not to obscure the described embodiments. While the exemplary embodiments described herein focus on charged particle beam systems, particularly dual-beam FIB systems, these are intended as non-limiting exemplary embodiments. Embodiments of the present disclosure address analytical instrument systems capable of analyzing a wide range of material samples to determine chemical, biological, physical, structural, or other properties, including, but not limited to, chemical structure, trace element composition, and the like. Furthermore, embodiments of the present disclosure may be applied to systems configured for automation (e.g., performing one or more processes or operations without human involvement) for sample preparation workflows, pseudo-automation (e.g., performing one or more processes or operations with limited human involvement and / or human initiation), and / or manual processes or operations (e.g., lamella preparation), such as those used in measuring semiconductor samples.

[0111] Some embodiments of the present disclosure include a system including one or more data processors and / or logic circuitry. In some embodiments, the system includes a non-transitory computer-readable storage medium including instructions that, when implemented on the one or more data processors and / or logic circuitry, cause the one or more data processors and / or logic circuitry to perform some or all of one or more methods and / or some or all of one or more processes and workflows disclosed herein. Some embodiments of the present disclosure include a computer program product tangibly embodied in a non-transitory machine-readable storage medium including instructions configured to cause one or more data processors and / or logic circuitry to perform some or all of one or more methods and / or some or all of one or more processes disclosed herein.

[0112] The terms and expressions which have been employed are used as terms of description rather than of limitation, and the use of such terms and expressions is not intended to exclude 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. Thus, while the present disclosure includes specific embodiments and optional features, it should be understood that modifications and variations of the concepts disclosed herein may be made by those skilled in the art, and that such modifications and variations are deemed to be within the scope of the appended claims.

[0113] When a term is used without an explicit definition, it should be understood that the ordinary meaning of the term is intended unless it has a special and / or specific meaning in the field of charged particle microscopy systems or other related fields. The terms “about” or “substantially” are used to indicate a deviation from a stated characteristic, where the deviation has little or no effect on the corresponding function, characteristic, or attribute of the described structure. In the illustrated example, when a dimensional parameter is described as “substantially equal” to another dimensional parameter, the term “substantially” is intended to reflect that the two compared parameters may not be equal within tolerance limits, such as manufacturing tolerances or confidence intervals inherent in the operation of the system. Similarly, when a geometric parameter, such as an alignment or angular orientation, is described as “nearly” 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 described state within tolerance limits (e.g., not exactly perpendicular). In the case of numerical values ​​such as diameter, length, width, etc., the term “about” may be understood to account for a deviation of up to ±10% from the stated value. For example, a dimension of "approximately 10 mm" can represent a dimension of 9 mm to 11 mm.

[0114] This specification provides exemplary embodiments and is not intended to limit the scope, applicability, or configuration of the present disclosure. Rather, the following description of exemplary embodiments will provide those skilled in the art with an enabling description for implementing various embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the spirit and scope as set forth in the appended claims. Specific details are described herein to provide a thorough understanding of the embodiments. However, it will be understood that the embodiments may be practiced without these specific details. For example, certain system components, systems, processes, and other elements of the disclosure may be shown in schematic diagram form or omitted from the figures so as not to obscure the embodiments in unnecessary detail. In other instances, well-known circuits, processes, components, structures, and / or techniques may be shown without unnecessary detail.

Claims

1. A resonator comprising: a dielectric substrate defining a first side and a second side opposite the first side; a first conductive layer disposed on the first side and arranged according to a pattern including ring portions, the ring portions defining gaps in the first conductive layer; a resonator including a second conductive layer disposed on the second side; a source electrode disposed proximate the first side, defining an aperture, and offset from the dielectric substrate.

2. 10. The charged particle source of claim 1, further comprising: a radio frequency (RF) power supply operably coupled to the resonator and calibrated to match the impedance of a radio frequency power signal in the presence of a discharge formed between the ring portion and the source electrode.

3. the ring portion is a first ring portion, the gap is a first gap, the pattern further includes a second ring portion defining a second gap, and the system further comprises: further comprising an RF power source operably coupled to the resonator via the first ring portion or the second ring portion; the RF power source is configured to provide a first well-matched impedance condition for a first radio frequency power signal in the presence of a discharge in the first gap; the RF power source is configured to provide a second well-matched impedance condition for a second radio frequency power signal in the absence of a discharge in the second gap; The charged particle source of claim 1 , wherein the first gap and the second gap are adjacent to each other.

4. The charged particle source of claim 3 , wherein the ring portion defines a narrowing taper toward the respective first gap or second gap.

5. 4. The charged particle source of claim 3, wherein the RF power source is coupled to the resonator through a switching circuit, the switching circuit configured to couple the first ring portion to the RF power source in the presence of the discharge and to couple the second ring portion to the RF power source in the absence of the discharge.

6. the first ring portion defining a first power injection point; the second ring portion defining a second power injection point; the first gap is defined within the first ring portion at a first fractional position α relative to the first power injection point; the second gap is defined within the second ring portion at a second fractional position β relative to the second power injection point; 4. The charged particle source of claim 3, wherein for a given input point within the ring portion, a fractional position is a ratio of a first path length between the gap and the given input point in the first direction to a second path length between the gap and the given input point in a second direction different from the first direction.

7. The charged particle source of claim 6 , wherein the first fractional position α and the second fractional position β are substantially equal.

8. 10. The charged particle source of claim 1, further comprising a DC bias tee electrically coupled to the ring portion, the DC bias tee including a DC power input and an RF power input, the DC bias tee comprising components that configure the DC bias tee to apply a DC bias to an RF power signal, thereby modifying an offset voltage of the RF power signal.

9. The charged particle source of claim 1 , wherein the source electrode is electrically coupled to a common reference voltage with the second conductive layer.

10. 10. The charged particle source of claim 1 , operably coupled to a focused ion beam (FIB) column, the FIB column comprising an extraction electrode, the resonator being oriented relative to the extraction electrode such that the source electrode is between the first side and the extraction electrode.

11. Further comprising a source assembly, the source assembly comprising: A source electrode; a fluid supply coupler; a fluid removal coupler; an electrical coupler; The charged particle source of claim 10 , wherein the resonator is disposed within the source assembly and is operatively coupled to the electrical coupler.

12. a vacuum enclosure; an isolation support disposed within the vacuum enclosure and mechanically coupled to the vacuum chamber and the source assembly, together defining a source chamber and an FIB chamber, the isolation support comprising an electrically insulating material that is electrically insulating at a reference voltage of a charged particle source system; The charged particle source of claim 11 , wherein the source chamber is fluidly coupled to the FIB chamber via a bypass conduit.

13. 1. A charged particle beam system comprising: a source section, A resonator comprising: a dielectric substrate defining a first side and a second side opposite the first side; a first conductive layer disposed on the first side and arranged according to a pattern including ring portions, the ring portions defining gaps in the first conductive layer; a second conductive layer disposed on the second side; and a source section including: a source electrode disposed proximate the first side, defining an aperture proximate a first end of the ring portion, and offset from the first conductive layer; a focused ion beam (FIB) column operatively coupled to the source section and comprising a plurality of charged particle optics; a vacuum chamber operatively connected to the FIB column.

14. The system of claim 13 , wherein the source electrode comprises a foil coupled to a support, the aperture being formed in the foil.

15. The system of claim 14, wherein the aperture is characterized by a diameter of about 20 μm to about 200 μm and an aspect ratio of about 0.05 to about 0.

5.

16. 14. The system of claim 13, wherein the gap is defined between a first end and a second end of the ring portion, and the aperture is substantially centered with the first end of the ring portion.

17. The source section further comprises a source assembly, the source assembly comprising: a dielectric substrate; a housing coupled to the dielectric substrate, the housing comprising: A source electrode; a fluid supply coupler; a fluid removal coupler; 14. The system of claim 13, further comprising an electrical coupler operably coupled to the first conductive layer and the second conductive layer through the housing.

18. 20. The system of claim 17, wherein at least a portion of the housing is coupled to a voltage source configured to apply a voltage of about 1 kV to about 350 kV to the at least a portion of the housing.

19. 14. The system of claim 13, wherein the FIB column comprises an extraction electrode, and the source section is oriented relative to the extraction electrode such that the source electrode is between the first side and the extraction electrode.

20. the ring portion is a first ring portion; the pattern defines a resonant multi-pole structure including the first ring portion; the resonant multipole structure includes a second ring portion; 14. The system of claim 13, wherein the first ring portion and the second ring portion define four gaps between four ends.

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