Techniques for patterning using a partially dispersed focused ion beam

Abstract

Systems, components, methods, and algorithms encoded as executable instructions for processing a sample using focused ion beams are described. A method includes processing a sample 125 by extracting a beam of ions 310 from a mixture of a first gas and a second gas. The beam can include a composition of relatively heavy ions and relatively light ions. The method can include deflecting 330 the beam of ions in accordance with a deflection pattern and directing the beam through an electromagnetic field 305 that is oblique relative to an axis of the beam. The electromagnetic field can be configured to at least partially disperse 315 the beam in space such that the deflection pattern causes the beam of ions to process a first portion of a sample surface by the relatively light ions and a second portion of the sample surface by the relatively heavy ions.

Description

TECHNIQUES FOR PATTERNING USING A PARTIALLY DISPERSED FOCUSED ION BEAM

[0001] The present application claims priority to the earlier-filed United States Provisional Patent Application number US63 / 712,253, entitled, “ METHOD FOR STUDYING HYDROGEN EMBRITTLEMENT USING HYDROGEN PLASMA FOCUSED ION BEAM INSTRUMENTS ” and filed on October 25. 2024, the contents of which are hereby incorporated by reference, in their entirety.TECHNICAL FIELD

[0002] Embodiments of the present disclosure are directed to charged particle beam systems, as well as algorithms and methods for their operation. In particular, some embodiments are directed toward techniques for processing samples using mixed-ion beams.BACKGROUND

[0003] Charged particle beam systems, including focused ion beam (FIB) and dual-beam FIB-SEM instruments, are widely used for precision material processing, imaging, and sample preparation across semiconductor, materials science, and analytical applications. These systems typically operate by directing a beam of charged particles, such as ions or electrons, toward a surface to remove, deposit, or modify material at micro- or nanoscale dimensions.

[0004] Conventional FIB instruments generally employ a single ion species derived from a single source gas. The characteristics of the ion beam, such as ion mass, charge state, and chemical reactivity, strongly influence the nature of the material interaction. As a result, selecting an ion species often requires trade-offs between sputter rate, surface damage, chemical reactivity, and deposition efficiency. For example, heavy inert ions can efficiently mill materials but may induce subsurface damage, while light reactive ions can promote chemical modification but may exhibit limited sputtering efficiency. Switching between different source gases or ion species to perform complementary processes can require significant time, calibration, and system reconditioning.

[0005] Furthermore, traditional FIB systems lack the capability to spatially control the contribution of multiple ion species within a single beam. The inability to deliver ions of different mass-to-charge ratios or chemical reactivities to distinct regions of a surface limits the precision and throughput of complex patterning, analytical, or material modificationworkflows. In analytical and manufacturing contexts where fine control of surface chemistry, morphology, or subsurface structure is required, such as in semiconductor metrology, nanofabrication, or hydrogen embrittlement studies, these limitations can lead to inefficiencies, reduced accuracy, and restricted process flexibility.

[0006] There is a need, therefore, for improved techniques and systems that enable greater control over the interaction between charged particle beams and sample surfaces. In particular, there is a need for methods and apparatuses that can facilitate selective or concurrent processing of materials by multiple ion species, without requiring physical reconfiguration or interruption of beam operation.BRIEF SUMMARY

[0007] In an aspect, a method includes processing a sample by extracting a beam of ions from a mixture of a first gas and a second gas. The beam can include a composition of relatively heavy ions and relatively light ions. The method can include deflecting the beam of ions in accordance with a deflection pattern and directing the beam through an electromagnetic field that is oblique relative to an axis of the beam. The electromagnetic field can be configured to at least partially disperse the beam in space such that the deflection pattern causes the beam of ions to process a first portion of a sample surface by the relatively light ions and a second portion of the sample surface by the relatively heavy ions.

[0008] In some embodiments, the first portion and the second portion can be partially coextensive. In some embodiments, the first portion and the second portion can be noncontiguous. In some embodiments, the method can further include modulating the electromagnetic field in accordance with the deflection pattern, wherein the magnetic field can be substantially zero for at least a portion of the deflection pattern.

[0009] In some embodiments, the deflection pattern can define a translation of the at least partially dispersed beam over the sample surface such that the second portion is also processed by the relatively light ions. In certain implementations, the relatively heavy ions can irradiate a specific location of the sample surface prior to the relatively light ions, or alternatively, the relatively light ions can irradiate the specific location prior to the relatively heavy ions. In some embodiments, the raster can include a circular raster.

[0010] In some embodiments, the relatively heavy ions can be extracted from the first gas and the relatively light ions can be extracted from the second gas. The first gas can be relativelyinert and can include xenon, krypton, argon, or neon. The second gas can be relatively reactive and can include hydrogen, oxygen, nitrogen, ammonia, or nitrous oxide. In certain embodiments, the relatively heavy ions can be characterized by a first atomic mass of 36 AMU or greater, while the relatively light ions can be characterized by a second atomic mass smaller than 36 AMU.

[0011] In some embodiments, the relatively light ions can include a first ion species and a second ion species that are characterized by different respective mass-to-charge ratios. The deflection pattern can configure the beam of ions to process the first portion of the sample surface by the first ion species and a third portion by the second ion species. The third portion, the second portion, and the first portion can be noncontiguous.

[0012] In some embodiments, the method can further include directing a precursor to a vicinity of the surface of the sample and inducing a reaction of the precursor at the first portion or the second portion. The reaction can result, at least in part, from energy released by interactions of the ions of the beam with the precursor. The reaction can form a deposit on or remove material from the surface of the sample. In some embodiments, the electromagnetic field can be applied to the beam of ions between an exit of a charged particle beam column and the sample surface.

[0013] In a second aspect, a focused ion beam system can include one or more charged particle beam sources and control circuitry in communication with one or more machine-readable media storing executable instructions for performing operations of the methods of the preceding aspect in one or more embodiments.

[0014] In a third aspect, one or more machine-readable media store executable instructions for performing operations of the method of the first aspect in one or more embodiments. The instructions can be configured to cause the system of the second aspect to perform the operations of the method of the first aspect in one or more embodiments.

[0015] The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the claimed subject matter. Thus, it should be understood that although the present claimed subject matter has been specifically disclosed by embodiments and optional features, modification and variation of the concepts herein disclosed can be resorted to by those skilled in the art, and that suchmodifications and variations are considered to be within the scope of this disclosure as defined by the appended claims. For example, the preceding aspects and various embodiments can be combined with one or more other aspects and / or embodiments of the same or other aspects.BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0016] The foregoing aspects and many of the attendant advantages of the present disclosure will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings.

[0017] FIG. 1 is a schematic diagram illustrating an example dual-beam system, in accordance with some embodiments of the present disclosure.

[0018] FIGs. 2A-2B are schematic diagrams illustrating an example plasma focused ion beam (PFIB) system, in accordance with some embodiments of the present disclosure.

[0019] FIGs. 3A-3C are schematic diagrams illustrating an example system for dispersing a beam of ions, in accordance with some embodiments of the present disclosure.

[0020] FIGs. 4A-4F are schematic diagrams illustrating example dispersal and raster patterns, in accordance with some embodiments of the present disclosure.

[0021] FIGs. 5A-5B are schematic diagrams illustrating an example dispersal pattern and the influence of magnetic field strength and polarity on dispersal extent and orientation, in accordance with some embodiments of the present disclosure.

[0022] FIG. 6 is a composite diagram illustrating a sample surface resulting from processing using a partially dispersed beam in a light-to-heavy orientation, in accordance with some embodiments of the present disclosure.

[0023] FIG. 7 is a composite diagram illustrating a sample surface resulting from processing using a partially dispersed beam in a heavy-to-light orientation, in accordance with some embodiments of the present disclosure.

[0024] FIGs. 8A-8C are schematic diagrams illustrating techniques for simultaneous patterning, in accordance with some embodiments of the present disclosure.

[0025] FIGs. 9A-9B are schematic diagrams illustrating details of the simultaneous patterning technique of FIGs. 8A-8C, in accordance with some embodiments of the present disclosure.

[0026] FIG. 10 is a graph illustrating example data generated using a Faraday cup and describing the composition of a mixed-species ion beam, in accordance with some embodiments of the present disclosure.

[0027] FIG. 11 is a composite diagram illustrating an example surface processed using the mixed-species ion beam of FIG. 10 under a simultaneous patterning approach described in FIGs. 8A-9B, in accordance with some embodiments of the present disclosure.

[0028] FIGs. 12-13 are charged particle beam microscope images illustrating a FIB scan pattern and a resulting simultaneously patterned surface prepared using the beam of FIG. 10, respectively, in accordance with some embodiments of the present disclosure.

[0029] FIGs. 14-15 are composite diagrams illustrating a simultaneously patterned surface, prepared using the beam of FIG. 10, in accordance with some embodiments of the present disclosure.

[0030] FIGs. 16-18 are composite diagrams illustrating near-surface regions of the patterned surface of FIGs. 14-15 for different ions of the beam of FIG. 10, in accordance with some embodiments of the present disclosure.

[0031] FIG. 19 is a composite diagram illustrating a titanium surface processed using the mixed-species ion beam of FIG. 10 under a simultaneous patterning approach described in FIGs. 8A-9B, in accordance with some embodiments of the present disclosure.

[0032] FIGs. 20A-D are electron microscope images including the regions processed as shown in FIG. 19, showing formation of titanium-hydrides, in accordance with some embodiments of the present disclosure.

[0033] FIG. 21 is a two-axis plot illustrating dispersal data for a beam of ions as a function of charge-to-mass ratio and for different electromagnetic field strength, in accordance with some embodiments of the present disclosure.

[0034] FIG. 22 is a two-axis plot illustrating dispersal data for a beam of ions as a function of charge-to-mass ratio and for different average beam energy, in accordance with some embodiments of the present disclosure.

[0035] FIGs. 23-24 are two-axis plots illustrating relative dispersal data for paired ions as a function of electromagnetic force for an average beam energy of 8 kV and 30 kV, respectively, in accordance with some embodiments of the present disclosure.

[0036] FIGs. 25A-D illustrate deposition data in an experimental system of a dispersed xenonoxygen FIB and a tetraethyl orthosilicate (TEOS) precursor, in accordance with some embodiments of the present disclosure.

[0037] FIG. 26 is a block diagram illustrating an example process for processing a sample using a beam of ions, in accordance with some embodiments of the present disclosure.

[0038] In the drawings, like reference numerals refer to like parts throughout the various views unless otherwise specified. Not all instances of an element are necessarily labeled to reduce clutter in the drawings where appropriate. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles being described.DETAILED DESCRIPTION

[0039] While specific embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the disclosure. In the forthcoming paragraphs, embodiments of charged particle beam systems, components, and methods for processing samples using a beam of ions are described. In the interest of simplicity of description, embodiments of the present disclosure focus on techniques for at least partially dispersing a beam of ions and processing at least a portion of a sample surface using the beam of ions, as applied in focused ion beam (FIB) instruments. To that end, embodiments are not limited to such systems, but rather are contemplated for analytical instrument systems that employ beams of mixed ions, both in terms of elemental composition and / or in terms of mass-to-charge ratio. In an illustrative example, broad-ion-beam systems can (may?) employ electromagnetic dispersal techniques of the present disclosure. Similarly, aspects of the present disclosure can be integrated into analytical systems that can derive meaningful information from ions of diverse mass-to-charge ratio, such as single-ion-mass-spectroscopy techniques. While embodiments of the present disclosure focus on dual-beam FIB-SEM systems, additional and / or alternative systems are contemplated, including but not limited to single-beam FIB systems, triple-beam laser-SEM-FIB systems, or the like.

[0040] Embodiments of the present disclosure include systems, methods, algorithms, and non-transitory media storing computer-readable instructions for processing a sample using a mixed beam of ions that has been at least partially dispersed in space. Methods for processing a sample can include extracting a beam of ions from a mixture of a first gas and a second gas. The first gas can be a relatively heavy gas and the second gas can be a relatively light gas. Inthis way, the beam of ions can include relatively heavy ions of the first gas and relatively light ions of the second gas. The method can include deflecting the beam of ions in accordance with a deflection pattern. The method can include directing the beam of ions through an electromagnetic field oblique relative to an axis of the beam. The electromagnetic field can be configured to at least partially disperse the beam in space, such that the deflection pattern causes the beam of ions to process a first portion of a sample surface by the relatively light ions and a second portion of the sample surface by the relatively heavy ions. Advantageously, techniques of the present disclosure improve ion beam processing of sample surfaces by: i) spatially selective processing of samples by various ionic species present in a beam; ii) augmenting and / or modulating the populations of various ionic species by controlling plasma composition and / or operating parameters; and iii) controlling and / or modulating diverse surface processing effects by modifying the relative order of exposure to specific ions making up a mixed beam of ions. To that end, the techniques presented here represent a significant advancement in the breadth of application, flexibility, and precision with which ion beam processing can be employed.

[0041] FIG. 1 is a schematic diagram illustrating an example dual-beam system 100, in accordance with some embodiments of the present disclosure. The example 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 illustrated as a scanning electron microscope (SEM) column, such that the example system 100 corresponds to a dual beam FIB-SEM system. The electron beam column 107, the FIB column 111, and the GIS 115 are illustrated as being operably coupled with 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. The axes A and B are illustrated converging onto a region of a sample 130, with the GIS 115 oriented toward the region of the sample 130 and configured to direct a gas stream including a precursor into the vacuum chamber. Advantageously, while axes A and B can also be oriented toward different locations, convergence permits the SEM system to image the region of the sample being processed by the FIB.

[0042] The electron source 105 can include one or more emitters configured to generate free electrons and to direct the electrons into the electron beam column 107. The emitters can include thermionic emitters, Schottky emitters, field-emission source emitters, or combinationsthereof, operably coupled to power systems configured to apply a high-voltage (e.g., on the order of kilovolts to hundreds of kilovolts) to an emission region of the emitter material. For example, the electron source 105 can include a lanthanum hexaboride (LaBe) emitter crystal to which a high electrical potential is applied to elicit the emission of electrons from a tip of the emitter crystal. In this way, a beam of electrons can be directed into the electron beam column 107.

[0043] The electron beam column 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 beam of electrons such that the beam is focused onto the sample 130, in accordance with a set of operating parameters. The operating parameters can include a beam current, a beam energy (e.g., in volts, in electron volts, or the like), a magnification parameter, a scan pattern, a dwell time, and / or one or more pulse parameters. In this way, the example system 100 can function as an SEM to image portions of the sample 130 and / or can be used for e-beam assisted deposition of material onto the sample 130 (e.g., in coordination with the GIS 115) or other sample modifications.

[0044] The ion source 110 can include one or more components configured to generate a beam of ions and to direct the ions into the FIB column 111. In general, the ions can include metal ions and / or nonmetal ions (e.g., noble gas, halogen, oxygen, nitrogen, or the like). To that end, the ion source 110 can include a plasma source (e.g., an inductively coupled plasma source or a microplasma source of the present disclosure) 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 and their mixtures can serve as plasma precursor gases, from which a stream of ions can be extracted. To that end, embodiments of the present disclosure are directed at systems, components, and methods for igniting and sustaining plasma discharges, and can include associated techniques for extracting ions from the plasma discharges, as described in more detail in reference to FIGs. 2A-2B.

[0045] As with the electron beam column 107, the FIB column 111 can include electromagnetic optics (e.g., electrostatic lenses, electromagnetic lenses, monochromators, etc.) and apertures configured to shape, focus, defocus, narrow, and / or direct the beam of ions such that the beam is focused onto the sample 130, in accordance with a set of operating parameters. The operating parameters can include a beam current, a beam energy (e.g., in volts, in electron volts, or the like), a magnification parameter, a scan pattern, a dwell time, and / or one or morepulse parameters. In this way, the example system 100 can function as a FIB to modify portions of the sample 130 and / or to be used for ion-beam assisted removal of material from and / or deposition of material onto the sample 130 (e.g., in coordination with the GIS 115).

[0046] Analogous to the energies described in reference to the electron beam, above, the ion beam energy can be selected (e.g., by a user, by an algorithm initiated by a user, and / or automatically without user intervention). In some embodiments, additional and / or alternative precursor decomposition mechanisms (e.g., surface activation and / or secondary electron reemission) can be used as a mechanism for precursor decomposition, thereby allowing the ion beam energy to be determined based at least in part on a relationship between beam energy, sample material properties, and the energetic characteristics of the precursor deposition reaction mechanism. Advantageously, ion beam-induced deposition can elicit relatively high yields, in comparison to electron beam-induced deposition, based at least in part on the combined effect of multiple energy transfer pathways.

[0047] The GIS 115 includes constituent elements that together permit the GIS 115 to generate a gas stream including the precursor and to direct the gas stream into the vacuum chamber. The components of the GIS 115 can include a carrier gas inlet, a nozzle 119, and a conduit fluidically coupling the nozzle 119 and a precursor reservoir 117. The precursor reservoir 117 can include a substantially non-reactive container (e.g., a ceramic crucible, PTFE enclosure, a non-reactive metal or alloy, or the like) that is at least partially exposed to the conduit. In this way, vapor generated from a precursor disposed in the precursor reservoir 117 can be directed toward the nozzle and into the vacuum chamber (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, fluidically coupled with the nozzle 119 via the conduit. In this way, the precursor can be entrained in a flow of carrier gas and directed toward the nozzle and into the vacuum chamber. Additionally and / or alternatively, the precursor can include a gas at standard conditions and can be introduced to the GIS 115 via a gas inlet provided as part of the GIS 115.

[0048] The operation of one or more components of the example system 100 can be coordinated by control circuitry, in accordance with machine-executable instructions (e.g., software, firmware, etc.) that can be stored in machine-readable storage media and / or received from external systems via wired and / or wireless communication techniques (e.g., over a WiFi or Bluetooth link). To that end, components of the example system 100 can be automated (e.g.,operating without human intervention), pseudo-automated (e.g., operating with limited human intervention to initiate operations, analyze output and confirm, or the like), or manually operated (e.g., where individual operations of the example system 100 are performed and / or coordinated by a human user). In an illustrative example, the sample stage 125 can be mechanically coupled with automated stage controls 127 that permit the sample 130 to be reversibly tilted relative to the beam axes A and B, such that the surface of the sample is oriented at a particular angle relative to a given beam axis during operation of the corresponding charged particle beam source. In this way, the operation of a given beam source can be coordinated with the operation of the stage controls 127. In another example, detectors provided as part of the example system 100 can be integrated into a control system that is configured to manipulate one or more operating parameters of the ion source 110, as part of a control scheme to implement one or more of the processing techniques described in reference to FIGs. 2-26 of the present disclosure.

[0049] Some embodiments of the present disclosure omit one or more components of example system 100. For example, one or more of the sources 105 and 110 and / or columns 107 and 111 can be omitted. In an illustrative example, an single-beam FIB system can be configured to perform operations for generating a beam of ions. Similarly, a multi-beam FIB system other than a dual-beam FIB-SEM (e.g., a FIB-Laser system or a FIB-SEM system for which two or more beam axes are not convergently trained on a given region of the sample 130) can implement the charged particle processing techniques of the present disclosure.

[0050] FIGs. 2A-2B are schematic diagrams illustrating an example plasma focused ion beam (PFIB) system 200, in accordance with some embodiments of the present disclosure. The PFIB system 200 is an example of the focused ion beam source described in reference to system 100 of FIG. 1. PFIB system 200 includes an ion source 205, an ion column 210, a vacuum system 215, and electronic components 220 configured to control the optics of the column 210 and / or the ion source 205. The system 200 further includes power circuitry 225 and gas supply system(s) 230, coupled with the ion source 205 and / or column 210. The system 200 is configured to generate a beam of ions and direct the beam of ions towards a workpiece 235, in substantial alignment with a beam axis “B,” and in accordance with a mill pattern.

[0051] As described in more detail in reference to the forthcoming figures, the ion source 205 can generate the beam of ions by extracting ions from a discharge formed using one or more gases supplied from the gas supply system(s) 230. As illustrated in FIG. 2B, the ion source 205is coupled with the gas supply system(s) 230 via one or more gas conduits 240. The gas conduit(s) 240 introduce gases to a discharge chamber 245 that defines an internal volume within which a discharge 250 can be generated. In the context of FIGs. 2A-2B, the ion source 205 is illustrated as an inductively coupled plasma (ICP) source, for which the discharge chamber 245 can be formed from a dielectric or insulating material around which a helical electrode 255 is disposed. A radio-frequency (RF) power signal can be provided by the power circuitry 225 to at least partially ionize the gas in the discharge chamber 245. Ions 260 from the discharge 250 can be extracted from the discharge chamber, and directed toward the ion column 210, by accelerating fields applied by one or more electrodes 265 (e.g., source electrode and / or extractor electrode).

[0052] Advantageously, the system 200 is configured to generate the discharge 250 from a combination of gases, including a relatively inert gas and a relatively reactive gas. a relatively heavy gas and a relatively light gas, or the like. In some cases, more than two gases are provided to the discharge chamber 245. In this way, the ions 260 extracted from the discharge 250 can include a mixture of ionic species that can be formed from the gases provided by the gas supply system(s) 230. As described in more detail in reference to FIGs. 3A-26, the composition of the ions 260 can include at least a fraction of a relatively reactive ionic species, such as hydrogen, oxygen, nitrogen, combinations thereof, or the like, and a fraction of a relatively inert gas, such as argon, krypton, xenon, or the like.

[0053] FIGs. 3A-3C are schematic diagrams illustrating an example technique for dispersing a beam of ions, in accordance with some embodiments of the present disclosure. FIG. 3A illustrates the interaction of a beam of ions including different ionic species with an electromagnetic field generated by an objective lens assembly of the electron beam column. FIG. 3B illustrates the transit of the beam of ions through the electromagnetic field in more detail, with the dispersal of the beam of ions shown schematically. FIG. 3C illustrates one physical explanation to better understand the operation of the technique of FIGs. 3A-3B.

[0054] FIG. 3 A illustrates a portion of the example system 100 of FIG. 1, enlarging the region of the sample 125, disposed in the vacuum chamber 110, in the interest of highlighting the role of the various components of the example system 100 in processes of the current disclosure, as described in more detail in reference to FIGs. 4A-26. For the technique illustrated in FIG. 3A, components of the electron optical objective 300 in the SEM column 105 are used to generate a magnetic field 305 in a vicinity of the sample 125. This can be referred to as an immersionfield when used for imaging using the electron beam. The schematic diagram in FIG. 3A is not drawn to scale, but reflects that the magnetic field can extend over a portion of the sample 125 or can extend over the entire sample, based at least in part on the operating parameters of the objective 300. In an illustrative example, the lens coil 301 of the objective 300 can be operated to generate a field strength characterized by an operating parameter from about -300 Ampere-Turns to about 300 Ampere-Turns in the vicinity of the sample, including sub-ranges, fractions, and interpolations thereof, as described in reference to the experimental data presented in FIGs.21-24. It is understood that the magnitude of the magnetic field can vary along the length of the beam axis A, such that the magnetic field can be stronger within the objective 300 or can be stronger between the objective 300 and the sample 125.

[0055] As described in more detail in reference to FIGs. 2A-2B, and in reference to forthcoming figures, a method for processing a sample can include extracting a beam of ions 310 from a mixture of a first gas and a second gas (e.g., beam of ions 260 of FIG. 2B). In some cases, the first gas is a relatively heavy gas and the second gas is a relatively light gas, such that the beam 310 includes relatively heavy ions of the first gas and relatively light ions of the second gas. In the examples described in reference to FIGs. 10-20, the relatively heavy gas is an relatively inert gas (e.g., xenon, argon, krypton, etc.) and the relatively light gas is a relatively reactive gas (e.g., hydrogen, oxygen, nitrogen, or the like). The beam of ions 310 extracted from the plasma source (e.g., source 105 of FIG. 1, source 205 of FIGs. 2A-2B) can include a mixture of ions of the first gas and ions of the second gas, but can also include multiple ionic species of one or more of the gases included as ion source gases. In the data described in reference to FIG. 10, for example, monatomic and polyatomic ions of hydrogen are observed.

[0056] Methods of the present disclosure can include deflecting the beam of ions 310 in accordance with a deflection pattern, an example of which is illustrated in FIG. 12. The deflection pattern refers to an encoded set of steering instructions that can be provided as one or more voltage signals to a set of electrostatic deflectors 330 (e.g., deflector coils, plates, or the like). The deflection pattern causes the beam of ions 310 to traverse at least a portion of a surface (e.g., the sample 125 of FIG. 1, the workpiece 235 of FIG. 2A) in accordance with a specified irradiation scheme, including information for the direction of travel of the beam (e.g., a raster pattern, a point-spread pattern, or the like), as well as information for the duration ofirradiation (e.g., dwell time, number of exposures, or the like). Further examples of deflection patterns are described in more detail in reference to FIGs. 4A-4F.

[0057] The beam of ions 310 can be directed through the magnetic field 305, as illustrated in FIGs. 3A-3C. As illustrated in FIG. 3A and FIG. 3B, the magnetic field 305 can be applied to the beam of ions 310 between an exit of the charged particle beam column (e.g., FIB column 110 of FIG. 1) and the sample surface 325. In the vicinity of the sample 125, the magnetic field can be oriented in a direction that is oblique relative to an axis of the beam 310 (labeled B, in — » FIG. 3A, but not referring to the alignment of the magnetic field, which is often denoted “ B ”). In this way, the field 305 can be configured to at least partially disperse the beam in space. As illustrated in FIGs. 3B-3C. dispersal of the beam in space refers to the tendency of a magnetic field to apply a force to a charged particle travelling through it that is a function of the particle's trajectory and the orientation of the field. In this way, ionic species of the beam 310 are deflected by the magnetic field 305 in proportion with the Lorentz force applied to the constituent ions as the beam 310 traverses the field 305. FIGs. 3A-3C focus on magnetic field-induced dispersal, but it is contemplated that electrostatic techniques could produce similar spatial dispersal in some embodiments. For example, an electrostatic field can apply a force that is proportional to the charge of the ions, which can cause a deflection that is a function of both mass and charge, which is the operating principle in electrostatic blanking of charged particle beams.

[0058] The magnetic field 305 through which the beam of ions 310 passes causes ions of the first gas and ions of the second gas to separate in space, attributable at least in part to the differences in mass and charge. For example, through a given magnetic field, an ionic species characterized by a relatively high mass-to-charge ratio (m / z) will be deflected less than an ionic species characterized by a relatively low m / z ratio. This causes the beam of ions 310 to process a first portion of the sample surface 325 by the relatively light ions and a second portion of the sample surface by the relatively heavy ions, as described schematically in reference to FIGs. 8A-9B.

[0059] FIGs. 4A-4F are schematic diagrams illustrating example dispersal and raster patterns, in accordance with some embodiments of the present disclosure. The diagrams in FIGs. 4A-4B are representations of simulation data generated using Monte Carlo methods, by which a representative dispersal pattern for a given set of operating conditions can be predicted. To that end, FIGs. 4A-4B illustrate non-contiguous and concentric dispersal patterns, respectively. Asdescribed in reference to FIGs. 3A-3C, the dispersal patterns are generated by directing a beam of ions (e.g., beam of ions 310 of FIG. 3A) that includes multiple constituent species of varying mass-to-charge (m / z). The dispersal patterns in FIGs. 4A-4B demonstrate the influence of the relative orientation of the magnetic field to that of the beam axis, B. For example, directing a beam of ions through a magnetic field that is substantially normal or at least oriented at an oblique angle relative to the beam axis will produce a spatial dispersal in a manner similar to that shown in FIG. 4A, with relatively light ions (marked in black) being separated from relatively heavy ions (marked in light grey) laterally (e.g., substantially in the x-direction labeled in FIG. 4A). The concentric dispersal pattern shown in FIG. 4B can be produced in various ways, for example, by varying the orientation and / or polarity of the magnetic field, by deflecting and / or rotating the beam using scanning instructions, and / or by motion of the sample.

[0060] Illustrative examples of such manipulations of the beam of ions are given in FIGs. 4C-4F. In FIG. 4C and FIG. 4D, a typical raster pattern is shown, as adapted for a dispersed beam, where the dispersed beam serializes the irradiation of first ions and second ions for a particular place on the sample surface by passing the ions with relatively high m / z before the relatively low m / z ions. In FIG. 4C, the alignment of the magnetic field is maintained, indicated visually as a positive polarity (+) for convenience, resulting in the raster pattern shown. The pattern in FIG. 4C can be advantageous for applications in surface activation, where the relatively high m / z imparts transient energy to the surface (e.g., surface 325 of FIG. 3A) and the relatively low m / z induces a reaction in the energized surface. In contrast, FIG. 4D shows the raster pattern that results from coordinating an alternation between “+” and polarities, corresponding to a substantially 180-degree reorientation, with the rows making up the raster pattern. The resulting pattern shows shuttling deflection of the beam of ions, such that the beam reorients between a forward pass and a return pass in a “serpentine” pattern. The pattern in FIG. 4D can be advantageous for surfaces and / or processes that are dose sensitive, such as deposition, delayering, or the like, where the relatively high m / z dissociates a deposition precursor, dissociates a removal precursor, and / or sputters a portion of the surface, after which the relatively low m / z interacts with the freshly formed or revealed portion of the surface.

[0061] In this way, the combination of the strength and orientation of the magnetic field, the energy of the beam of ions, the alignment of the beam axis, and the scan pattern together contribute to defining the dispersal pattern, via the Lorentz force applied to the ions of thebeam of ions. For example, FIG. 4D describes modulating the electromagnetic field in accordance with the scan pattern. In some embodiments, the various parameters can be modulated such that the Lorentz force applied to the ions of the beam of ions is substantially zero for a portion of the scan pattern. In the examples of FIG. 4C-4E, one or more of the lateral scans can be performed at least partially with an undispersed beam by, for example, removing the magnetic field from the space between the ion column and the sample surface.

[0062] FIGs. 4E-4F illustrate alternative dispersal patterns that enable patterned irradiation whereby one or more regions of the sample surface are selectively exposed to one or the other of the constituent ion species of the beam of ions. For example, FIG. 4E illustrates a scan pattern whereby the raster is substantially normal to the lateral dispersal direction (e.g., the raster is oriented in the “y” direction and the dispersal pattern is oriented in the “x” direction, in a modified “cleaning cross section” raster pattern). Rastering the beam of ions in this way produces an alternating exposure pattern on the surface, where portions of the sample surface are selectively exposed to relatively high m / z ions and other portions are selectively exposed to relatively low m / z ions. This approach is reproduced for a circular raster in FIG. 4F, which results in an exposure pattern substantially as illustrated in FIG. 4B. The pattern shown in FIG.4F can be produced by rotating the beam using electromagnetic optics of the beam column, without disrupting spatial dispersal, by steering the beam in a circular direction and modulating the orientation of the magnetic field.

[0063] FIGs. 5A-5B are schematic diagrams illustrating an example dispersal pattern and the influence of magnetic field strength and polarity on dispersal extent and orientation, in accordance with some embodiments of the present disclosure. In addition to the dispersal patterns described in reference to FIGs. 4A-4F, embodiments of the present disclosure include generating dispersal patterns as illustrated in FIG. 5A, using the techniques described in reference to FIG. 5B.

[0064] FIG. 5A shows a dispersal pattern in which relatively low m / z ions (in black) are spatially separated from relatively high m / z ions (in grey), such that the different constituent ionic species form distinct beam spots, offset from the beam axis B. In the example shown, the relatively low m / z ions form a first beamlet 500, offset from the beam axis B by a first distance 505, and the relatively high m / z ions form a second beamlet 501, offset from the beam axis B by a second distance 510. As described in reference to FIG. 3A-3C, dispersal of an ion beamthat traverses a magnetic field will tend to result in the second distance 510 being shorter than the first distance 505.

[0065] To that end, FIG. 5B shows that the separation of the beamlets 500 and 501 increases with increasing strength of the magnetic field 515, where the magnitude of the field 515 increases in both directions from the vertical axis on the plot. The plot also shows that the polarity of the field can be switched from “positive” to “negative” which refers to an orientation in space relative to the beam axis, B. The effect of the change in polarity is to reverse the dispersal vector, but the relative lengths of the first distance 505 and the second distance 510 are not inverted. As shown, the beamlets 500 and 501 can overlap, at least partially, owing to the relation between the distances 505 and 510 and the respective diameter of the beamlets 500 and 501. The extent of overlap can be modulated, at least in part, by controlling properties of the field 515 (e.g., orientation, field strength, etc.) and / or the beam of ions (e.g., beam energy, relative beam composition, beam angle, etc.).

[0066] In FIG. 5B, the central spot illustrates an undispersed beam, substantially centered about the beam axis, B. With increasing distance from the beam axis, the beamlets are increasingly separate, corresponding to the increasing magnitude of the field 515 effecting an increasing dispersal of the beam by m / z. The illustration includes a third beamlet 503, corresponding to a third ionic species characterized by a m / z between that of the first beamlet 500 and the second beamlet 501, as described in more detail in reference to forthcoming figures. Further, the orientation of the dispersal is reversed on either side of the beam axis, B, corresponding to the inversion of field orientation (denoted with a “+” and ).

[0067] Advantageously, separating the beamlets 500-503 as illustrated enables spatially localized irradiation of sample surfaces with selected ionic species. This ability enables patterned irradiation, as well as for study of ion-surface interaction that is species-specific. Further, the separation of ionic species into beamlets enables spatially localized sequencing of irradiation, as described in reference to FIGs. 4C-4D, and as described further in reference to FIGs. 6-7, below. To that end. embodiments of the present disclosure permit far greater control over surface modification and processing schemes than is conventionally afforded by FIB systems. In particular, the techniques described herein permit spatially localized FIB processing without switching gases between processing operations, with attendant advantages for productivity.

[0068] FIG. 6 is a composite diagram illustrating a sample surface resulting from processing using a partially dispersed beam in a light-to-heavy orientation, in accordance with some embodiments of the present disclosure. FIG. 6 includes a scanning electron microscope (SEM) image of a surface that has been processed by a dispersed FIB, where a first beamlet comprising relatively low m / z ions traverses a portion of the sample surface before that portion is subsequently traversed by a second beamlet comprising relatively high m / z ions. In some cases, as when both beamlets comprise singly-charged ions, the deflection pattern can define the raster such that the relatively light ions are incident on the sample surface prior to the relatively heavy ions. In the example shown, the exposure to relatively low m / z, followed by relatively high m / z, produces a surface that is qualitatively smooth, in comparison to the resultant surface in FIG. 7. Advantageously, controlling surface morphology further improves the flexibility of FIB -based sample processing techniques in a way that is not conventionally available.

[0069] FIG. 7 is a composite diagram illustrating a sample surface resulting from processing using a partially dispersed beam in a heavy-to-light orientation, in accordance with some embodiments of the present disclosure. FIG. 7 includes an SEM image of a surface that has been processed by a dispersed FIB, where a first beamlet comprising relatively high m / z ions traverses a portion of the sample surface before that portion is subsequently traversed by a second beamlet comprising relatively low m / z ions. In some cases, as when both beamlets comprise singly-charged ions, the deflection pattern can define the raster such that the relatively heavy ions are incident on the sample surface prior to the relatively light ions. In contrast to the resultant surface in FIG. 6, the surface that is produced by the treatment of FIG.7 is qualitatively rough, and appears to exhibit increased redeposition of sample material. As with FIG. 6, controlling surface morphology further improves the flexibility of FIB-based sample processing techniques in a way that is not conventionally available.

[0070] FIGs. 8A-8C are schematic diagrams illustrating techniques for simultaneous patterning, in accordance with some embodiments of the present disclosure. To that end, FIGs.8A-8C are not drawn to scale. The diagrams in FIGs. 8A-8C serve to introduce the approaches used to generate example data described in reference to FIGs. 10-20. To that end, FIG. 8A includes a schematic showing two spatially separated portions 800 of a sample surface. A first portion 800-1 is irradiated by a first beamlet 805 and a second portion 800-2 is irradiated by a second beamlet 810. In the example of FIG. 8 A, the first beamlet 805 is characterized by arelatively high m / z, demonstrated by a relatively short first offset 815 from the beam axis B. The second beamlet 810 is characterized by a relatively low m / z, demonstrated by a relatively long second offset 820 from the beam axis B, assuming a spatially isotropic field being used to disperse the beam of ions into the beamlets 805 and 810. The portions 800 are defined by a deflection pattern 825, represented here as a region of the sample surface of commensurate size to those of portions 800-1 and 800-2, which corresponds to the area of the sample surface over which an undispersed beam 830 would travel in the absence of a magnetic dispersal field. In this way. the deflection pattern 825 defines a trajectory 835 for the beamlets 805 and 810 that is substantially reproduced at each respective offset 815 and 820 from the beam axis.

[0071] As described in more detail in reference to FIGs. 8B-9C, spatially separating the portions 800 affords significant flexibility over the order and type of surface processing by ions of the beam of ions. For example. FIG. 8B shows that a beam comprising three different ionic species of different m / z can be separated into three spatially separated portions 800, with a third portion 800-3 interposed between the first portion 800-1 and the deflection pattern 825 at a third offset 840 shorter than the first offset 815. This reflects that the beam of ions can include more than two ionic species, as described in reference to the example of monatomic and polyatomic hydrogen ions in the forthcoming figures. The FIB beam can include polyatomic and / or molecular ions, such as diatomic oxygen, diatomic nitrogen, nitric oxide, or larger polyatomic ions, as well as relatively inert ions (e.g., xenon, argon, etc.). For example, the relatively heavy ions can be characterized by an atomic mass of 36 AMU or greater (e.g., krypton, xenon, N2O, etc.), and the relatively light ions can be characterized by an atomic mass smaller than 36 AMU (e.g., argon, H2O, H3, H2, H, O2, N2, O, N, etc.).

[0072] FIG. 8C illustrates a particular advantage of the techniques of the present disclosure, namely, the spatial localization and chemical control of FIB processing by exposure to multiple dispersed beams, in accordance with different deflection patterns 825. In this way, one or more regions of a sample can be irradiated by at least a subset of the constituent ionic species of the beam of ions, with the dose, spatial localization, and energy of each ionic species being separately controlled. In the example of FIG. 8C, the second portion 800-2 is partially overlaid by the third portion 800-3 by shifting the deflection pattern 825 by a vector 845 projected onto the surface, including an x component and a y component, such that only part of the second portion 800-2 is overlaid by the third portion 800-3. This example illustrates a relatively simple approach, in that the deflection pattern, beam composition, beam energy, and temporal factors(e.g., dose, dwell time, etc.) are not discussed. It is contemplated, however, that techniques of the present disclosure include processing samples by spatially localized treatment using two or more ionic species, with precise control over the dose, energy, chemical composition, of irradiation, without altering the composition of the plasma source gas. Advantageously, these capabilities permit detailed surface studies of diverse materials, of particular relevance in the fields of heterogenous chemistry, nanomaterials, and metallurgy, among others.

[0073] FIGs. 9A-9B are schematic diagrams illustrating details of the simultaneous patterning technique of FIGs. 8A-8C, in accordance with some embodiments of the present disclosure. The two diagrams in FIGs. 9A-9B illustrate additional operating parameters that afford control over the spatial localization of surface processing by multi-species FIB beams. In particular, the magnitude of the dispersal can be modulated by varying the magnitude of the magnetic field (e.g., field 305 of FIG. 3A) in addition to or alternatively to varying the energy of the beam. To that end, the deflection pattern, the magnetic field, and parameters of the beam of ions can be defined such that a dispersal extent of the beam of ions can be a controllable feature of sample processing. The dispersal extent can be expressed as a ratio of overlap in two dimensions, as a ratio of offsets relative to the beam axis, B, in one dimension, and / or as a discrete qualitative scale (e.g., undispersed, partially dispersed, fully dispersed.

[0074] In the example of FIG. 9A, a first portion 900-1 of a sample surface 905 is irradiated by a first beamlet 910-1 and a second portion 900-2 of the sample surface 905 is irradiated by a second beamlet 910-2. The parameters of the system are defined such that the first portion 900-1 and the second portion 900-2 are non-contiguous and non-overlapping, where the first portion 900-1 is separated from the region of the deflection pattern 925 by a first offset 915 and the second portion 900-2 is separated from the deflection pattern 925 by a second offset 920. The fully dispersed configuration illustrated in FIG. 9A is another example of the techniques described in reference to FIGs. 8A-8C. In contrast. FIG. 9B shows an example technique where the beam is fully dispersed, with beamlets being spatially resolved and separate, but where the dimensions of a deflection pattern 935 are defined such that the portions 900 at least partially overlap. In this way, the deflection pattern 935 provides a further source of control over surface treatment. The resulting treatment has three distinct regions, from which the effects of individual ions and combinations of ions on the sample surface 905 can be observed.

[0075] FIG. 10 is a graph illustrating example data generated using a Faraday cup and describing the composition of a mixed-species ion beam, in accordance with someembodiments of the present disclosure. The graph presents “scanned distance” in units of millimeters on the x-axis and current in picoamperes on the y-axis. These are analogous to m / z on the x-axis and for composition on the y-axis, in that the faraday cup is measuring beam composition as a function of offset (e.g., offsets 815 and 820 of FIG. 8 A) by scanning a current detector along a lateral direction relative to a dispersed beam, or by scanning a dispersed beam across a stationary detector. The resulting spectrum reveals that the beam being measured includes five main constituent ions. From the composition of the plasma source gas and / or by spectroscopic examination of the plasma, it is known that in the particular example of FIG. 10, and as described in reference to the forthcoming figures, the constituent ionic species included in the beam include monatomic and polyatomic hydrogen ions, xenon ions, and molecular water ions, dispersed along a given linear dimension in proportion to their m / z ratios. To that end, the beam axis is positioned to the right of the peak identified as xenon, with the offset increasing with decreasing ionic mass, from xenon, to monatomic hydrogen.

[0076] Notably, ionic species are present in the beam at different relative fractions. For example, the data reflect a relatively high fraction of xenon and monatomic hydrogen, relative to polyatomic hydrogen and water. As described in reference to FIGs. 8A-9B, the techniques of the present disclosure permit samples to be processed with precise control of ion dose, compensating for differences in ion fraction. In this way, controlled study of ion-surface interaction is improved significantly, both by modifying the relative fraction of different ions (e.g., by modulating the plasma parameters of the ion source), and by controlling the dispersal extent and deflection pattern(s) employed. In an illustrative example, the relative proportion of monatomic hydrogen ions to polyatomic hydrogen ions can be controlled by varying the plasma power, with higher plasma power being associated with higher dissociation rates (e.g., shifting the fraction of monatomic hydrogen higher).

[0077] FIG. 11 is a composite diagram illustrating an example surface processed using the mixed-species ion beam of FIG. 10 under a simultaneous patterning approach described in FIGs. 8A-9B, in accordance with some embodiments of the present disclosure. The diagram includes a patterned surface, imaged in an SEM micrograph, with the different portions (e.g., portions 800 of FIG. 8A) of the surface labeled with the corresponding ionic species that was directed to each respective portion. Visually reproducing the relative offsets that were quantified in FIG. 10, the surface has been concurrently treated by the five different ionic species in five different and non-contiguous regions of the sample surface. Advantageously,this permits the properties of the treated surface to be analyzed using typical techniques (e.g., x-ray mapping), as well as samples to be extracted from one or more portions for further microanalysis (e.g., by sectioning, lamella prep, etc.) to assess the particular effects of individual constituent ions. These techniques are conventionally possible only with switching the composition of the beam of ions (e.g., by changing the plasma source gas).

[0078] FIGs. 12-13 are electron microscope images illustrating a FIB scan pattern and a resulting simultaneously patterned surface prepared using the beam of FIG. 10, respectively, in accordance with some embodiments of the present disclosure. The diagram in FIG. 12 is an output of a FIB user interface, superimposing a deflection pattern at-scale. The deflection pattern includes both a spatial indication of the dimensions of the deflection pattern, about 5 micrometers wide by about 25 micrometers high. The image also includes parameters of the FIB treatment, including total beam current (about 3.9 nA) and the lens current used to generate the magnetic dispersal field (about 50 Ampere-Turns, or AT). These parameters are examples, with the values in practice being based at least in part on the properties of the sample, the ion source gas. and the intended treatment. For example, beam current can be from about 1 pA to about 1 uA, including sub-ranges, fractions, and interpolations thereof. Beam energy can be from about 0.5 keV to about 30 keV, including sub-ranges, fractions, and interpolations thereof. Lens current can be from about -50 AT to about 300 AT, including sub-ranges, fractions, and interpolations thereof (e.g., about -35 AT to about 100 AT)..

[0079] FIG. 13 is an SEM image of the resulting surface, using a beam of ions comprising six ionic species. Notably, the offset for each non-contiguous treated portion is correlated to the m / z ratio of each respective species, as described in more detail in reference to FIGs. 21-22. The image of FIG. 13 further demonstrates that spatially localizing the treatment of the surface by distinct ionic species reveals details of ion- surface interaction that would be difficult to elucidate without such capability. For example, for hydrogen ions irradiating an aluminum surface, with increasing distance toward the left of the image, the surface exhibits increasingly large blisters. Understood in the context of FIGs. 14-15 and, in particular, from information revealed in sectioning the regions treated by different hydrogen species, the interaction of hydrogen ions and the surface is found to produce different types of porosity and surface blistering. These findings reflect the improvement to specificity and control over surface functional modification that is afforded by FIB -based techniques of the present disclosure.

[0080] FIGs. 14-15 are composite diagrams illustrating a simultaneously patterned surface and a detail of the patterned surface, respectively, the patterning being prepared using the beam of FIG. 10, in accordance with some embodiments of the present disclosure. FIG. 14 includes a secondary electron image of a processed sample surface, taken in a dual-beam FIB-SEM, using the FIB as the source of secondary electrons, as indicated by the system information at the base of the image. The SE image is annotated to identify which of the ionic species of the dispersed beam are associated with which treated regions of the sample surface. As described in reference to FIGs. 8A-8B and FIG. 9A, the sample surface has been simultaneously irradiated in noncontiguous regions by three distinct ionic species of hydrogen (monatomic, diatomic, and triatomic), ionized water, and xenon ions. A scan pattern 1400 is indicated in a lateral (e.g., raster, serpentine, etc.) pattern. The regions corresponding to hydrogen ions are labeled.Advantageously, simultaneous patterning demonstrated in the image of FIG. 14 can deliver a specific dose of one of the constituent ionic species. In the example shown, the treatment was controlled for a specific dose of monatomic hydrogen ions. As reproduced in the image, the FIB treatment used a current of 6.15 nA H+ (as measured using the techniques of FIG. 10), an average beam energy of 30 keV, a treatment region of about 5 um by about 50 um, and for a total treatment time of 5 minutes and 42 seconds. In this way, the region treated by monatomic hydrogen received a total of about 2.1 p , corresponding to a dose of about 3.4xl07ions.

[0081] FIG. 15 includes a secondary electron image of the processed sample surface, taken in the same dual-beam FIB-SEM, using the SEM as the source of secondary electrons, as indicated by the system information at the base of the image. The image includes a higher magnification of the region patterned with ionic hydrogen, in discrete regions labeled with the corresponding ionic species. The image, providing higher resolution as well as higher magnification, relative to the FIB image in FIG. 14, reveals an effect of m / z on the resulting surface. As described in more detail in FIGs. 16-18, increasing m / z of 1 amu for monatomic hydrogen ions, 2 amu for diatomic hydrogen ions, and 3 amu for triatomic hydrogen ions produces different effects on the surface regions being treated. For example, all three patterned regions exhibit surface blistering that is characteristic of hydrogen bubble formation. Increasing m / z is correlated to a decreasing blister size, as well as an increasing average depth of porosity formation. Advantageously, the techniques of the present disclosure permit the elucidation of species-dependent effects on surface chemistry and morphology, not just at the surface, but also within the near-surface region.

[0082] FIGs. 16-18 are composite diagrams illustrating near-surface regions of the patterned surface of FIGs. 14-15, in cross section, for different constituent hydrogen ions of the beam of FIG. 10, in accordance with some embodiments of the present disclosure. Increasing m / z of the hydrogen ion species of the beam is correlated to a progressively shallower depth at which porosity is observed. Without being bound to a particular physical mechanism or phenomenon, it is contemplated that penetration depth and m / z are positively correlated. Advantageously, the techniques of the present disclosure permit porosity induction in near-surface regions of a sample with specific control of ion species, as well as energy, dose, and spatial localization, in a single sample, in a single operation.

[0083] The technique of dispersed patterning described herein enable assessment of the respective contributions of different ionic species extracted from complex gas mixtures. The specific case of blister formation and porosity from energetic hydrogen ion irradiation is illustrated in FIGs. 16-18, but other examples include corrosion in oxygen beams, milling of polymeric materials, among others. Formation of subsurface porosity is of particular interest to the nuclear energy industry, as the hydrogen ion species illustrated in FIGs. 16-18 are all formed in water-cooled reactors under typical operating conditions. Understanding which of the species is responsible for corrosion effects on fuel cladding materials is important from an economic and safety point of view, and insight into the different reactivities of the various hydrogen ion species is difficult to obtain with other techniques. Similarly, understanding the different behaviors of O+, C>2+, H2O+may be important in fundamental studies of corrosion mechanisms of various materials.

[0084] A particular advantage of dispersed patterning studies is that the plasma FIB source conditions can be adjusted to favor the formation of species with desired behaviors. For example, if dispersed milling of a polymer sample with oxygen beams containing a mixture of O+and O2+ions reveals that the removal rate is higher for the C>2+species, then the plasma FIB source conditions can be adjusted to favor that species. For example, the lower RF power settings may result in a higher abundance of O2+relative to O+. In this way. dispersed patterning experiments could serve as a diagnostic tool for optimizing plasma FIB source conditions.FIG. 19 is a composite diagram illustrating a titanium surface processed using the mixed-species ion beam of FIG. 10 under a simultaneous patterning approach described in FIGs. 6A-6B, in accordance with some embodiments of the present disclosure. FIG. 19 includes an SEMimage taken in a dual-beam FIB-SEM, as discussed in reference to FIGs. 1-2B. Irradiation by a dispersed beam of ions including a relatively light gas (hydrogen) and a relatively heavy gas (xenon) produced a concurrently patterned surface including five discrete regions, of which the field of view of the detector in FIG. 19 includes the three hydrogen ion species as-labeled. FIG.19is a magnified image of a portion of the overall irradiation pattern, showing the three patterned regions corresponding to hydrogen ions of the beam and omitting the xenon-patterned region and the other species in-between. The image shown in FIG. 19 was generated using a secondary electron detector (e.g., a “through-the-lens” detector) and does not include significant elemental contrast. In this way, the contrast seen in FIG. 19 reflects adifferent characteristic secondary electron remission fraction of the treated regions, relative to the native titanium surface, and indicates that a change to the treated surface has occurred, attributable to one of several different sources, including but not limited to contamination, hydride formation, or the like.

[0085]

[0086] FIG. 20A is an electron microscope image of the same field of view shown in FIG. 19, showing formation of titanium-hydrides in the surface and near surface regions of the sample, in accordance with some embodiments of the present disclosure. FIGs. 20A-20D include SEM images generated using a backscatter (BSE) detector capable of detecting elemental contrast. FIGs. 20B-20D are higher magnification BSE images of portions of the surface treated by monatomic hydrogen ions, diatomic hydrogen ions, and triatomic hydrogen ions, respectively.

[0087] Elemental and compositional analysis indicates that the structures appearing as dark, substantially parallel slivers in the surface correspond to hydrides that form from the covalent bonding of hydrogen with titanium in the metal surface. Each ionic species produced different hydride formations, with the densest being formed under irradiation by triatomic hydrogen and the sparsest being formed under irradiation by diatomic hydrogen, indicating a role of dose in hydride formation, where the triatomic hydrogen is both most present in the beams of the present disclosure and each ion delivers three hydrogen atoms.

[0088] Morphologically, the shape of the hydride patterns differed between the different ionic species, with polyatomic ions forming relatively broad hydrides and monatomic hydrogen ions forming relatively narrow hydrides, indicating a role of ionic chemical structure on hydride formation. Advantageously, the techniques of the present disclosure permit speciesdependency, spatial localization, as well as energetic and dose control of surface chemicalfunctionalization to be varied as part of sample processing, in a single sample and in a single irradiation operation.

[0089] Without being bound to a particular physical mechanism or phenomenon, the formation of hydrides in titanium with species dependent formation density illustrates that analogous approaches can be applied to form nitrides, oxides, sulfides, fluorides, chlorides, or the like, with the same precise control observed in FIGs. 20A-D, where the number of species and distinct treatment zones can be modulated by the composition of the ion source gas, the operating parameters of the plasma source and / or the beam-forming optics, and the magnitude of the dispersal field.

[0090] FIG. 21 is a two-axis plot illustrating dispersal data for a beam of ions as a function of mass-to-charge ratio and for different electromagnetic field strength, in accordance with some embodiments of the present disclosure. The plot describes results of magnetic dispersal of ions over a range of m / z from about 1 amu / q to about 300 amu / q in magnetic fields having a strength of 25 AT, 50 AT, and 100 AT, at a beam energy of 8keV. As described in reference to FIGs. 3A-3C and in FIG. 9B, the influence of both m / z and field strength exhibit a relatively stronger effect on lighter ions, with the inversely proportional trend in displacement vs. m / z being reproduced for all values of magnetic field strength. Without being bound to a particular physical mechanism of phenomenon, the ratio of mass-to-charge, for a given velocity (e.g., beam energy), at least partly explains the tendency of lighter ions to disperse more than heavier ions.

[0091] This can be understood from the relation provided for the magnetic Lorentz force, which is F = q(E+vxB):F g(E T v x B)

[0092] where “F” is the force applied to an ion travelling through an electric field “E” and / or a magnetic field “B,” having a velocity “v,” and a charge “q.” In an illustrative example of a magnetic field only, the relation becomes simply force, F = q * v x B, which can be related to the mass of a given ion by m * a = q * v x B, showing that the acceleration, in a direction indicated by the cross product of the velocity and the magnetic field vector, is inversely proportional to the mass of the ion and directly proportional to the magnetic field strength and the ion velocity. The situation is further simplified in the case of an electric field, E, for whichthe force is F = m * a = q * E, for which acceleration maintains the inverse proportionality with ion mass, but is independent of ion velocity and therefore beam energy.

[0093] FIG. 22 is a two-axis plot illustrating dispersal data for a beam of ions as a function of mass-to-charge ratio and for different average beam energy, in accordance with some embodiments of the present disclosure. FIG. 22 demonstrates the proportionality discussed in more detail in reference to FIG. 21, whereby ions over a range of m / z from about 1 amu / q to about 300 amu / q are dispersed in a magnetic field having a strength of 50 AT, at beam energies of 8 keV and 30 keV. A similar inverse correlation is found in the dispersal-dependency on beam energy as was observed in the magnetic field data, where m / z and dispersal are inversely proportional. The two data sets differ in that the deflection extent of relatively slower ions (e.g., 8 keV) exceeds that of relatively faster ions (e.g., 30 keV). This difference can be understood mathematically, from the cross-product of velocity and magnetic field vector discussed in reference to FIG. 21, above, but can also be understood conceptually by considering that the residence time of a given ion of the beam in the magnetic field.

[0094] FIGs. 23-24 are two-axis plots illustrating relative dispersal data for paired ions as a function of electromagnetic force for an average beam energy of 8 kV and 30 kV, respectively, in accordance with some embodiments of the present disclosure. These graphs demonstrate the phenomenon described in more detail in reference to FIGs. 9A-9B, namely that the operating parameters of the ion beam and the magnetic field can be tuned to select a relative dispersal between ionic species of the beam, based at least in part on the m / z of the different constituent ions.

[0095] The graphs in FIGs. 23-24 show relative dispersal, measured as a distance between characteristic beamlets, using the technique described in reference to FIG. 10, where the beam comprised ions of nitrogen, oxygen, xenon, carbon, and molecular species including the same. The graphs show that spatial separation between species can be tuned by modifying the magnetic field strength and the beam velocity, with the relative dispersal being larger at lower beam velocity.

[0096] Advantageously, the data presented in FIGs. 23-24 demonstrate that the techniques of the present disclosure extend to larger ionic species, including molecular species, of larger atoms, including but not limited to carbon, nitrogen, and oxygen, as well as hydrogen and oxygen.

[0097] FIGs. 25A-D illustrate deposition data in an experimental system of a dispersed xenonoxygen FIB and a tetraethyl orthosilicate (TEOS) precursor, in accordance with some embodiments of the present disclosure. FIG. 25A is a beam composition spectrum prepared as described in reference to FIG. 10. FIG. 25B is a composite diagram including a secondary electron image depicting a surface processed using the dispersed beam of FIG. 25A in two conditions of precursor flow. FIG. 25C is an energy dispersive spectroscopy (EDS) x-ray elemental map of the surface shown in FIG. 25B, showing local oxygen composition. FIG. 25D is an EDS x-ray elemental map of the surface shown in FIG. 25B, showing local carbon composition.

[0098] The data shown in FIGs. 25A-D demonstrate that the techniques of the present disclosure introduce the ability to precisely control the location, deposition rate, and deposition chemistry of a FIB -deposited material. In FIG. 25 A, the beam composition spectrum reveals that a xenon-oxygen FIB beam includes monatomic oxygen ions, diatomic oxygen ions, and xenon ions. As described in reference to FIG. 10, the species are dispersed in inverse correlation to the m / z ratio, such that an undispersed beam would be measured to the right of the peak labeled Xe+at a scan distance of about 200 mm.

[0099] FIG. 25B shows two sets of irradiation condition, forming an array of six portions of a silicon substrate that has been irradiated by distinct beamlets of the dispersed xenon-oxygen FIB. These reproduce the monatomic, diatomic, rare-gas dispersal pattern shown in FIG. 25 A, with a fist, upper set of three portions being patterned in the absence of the TEOS precursor, and the second, lower set of three portions being patterned in the presence of the TEOS precursor. In the ion beam-induced deposition (IBID) processes of the present disclosure, a precursor (e.g., TEOS) is delivered to a vicinity of the surface of the sample. In this context, the term vicinity refers to a volumetric region bounded on one side by the surface, with at least some of the precursor adsorbing to the surface. Without being bound to a particular physical mechanism or phenomenon, the energy of the beam can be used to decompose the precursor, to provide energy to generate a silica layer, and to provide excess oxygen to remove residual surface carbon. These effects are demonstrated by the different surfaces resulting from irradiation by constituent ion species in the presence of TEOS, the chemical compositions of which are demonstrated in FIGs. 25C-D. In FIG. 25C, the chemical compositions of the patterned portions of the substrate show that a baseline amount of oxygen was implanted in the surface (upper row) in the absence of TEOS and that the amount of oxygen in or on the surfaceincreased significantly in the presence of TEOS for both “reactive” species (oxygen) and for “inert” species (xenon). This result demonstrates that the formation of silica occurs during decomposition of TEOS that is activated by energy delivered by the FIB, but that the presence of excess oxygen accelerates the formation of silica and other silicon oxide species. In FIG. 25D, the role of excess oxygen in removing carbon from the surface is shown. Monatomic oxygen ions and xenon ions left residual carbon in the treated portions of the substrate, while EDS map data showed that treatment with diatomic oxygen ions produced a negligible carbon signal. Advantageously, the data in FIGs. 25A-D demonstrate that the techniques of the present disclosure can also be applied to reactive ion etching (RIE) processes. The RIE process typically involves exposing a surface to an energetic FIB in the presence of an etchant gas or delayering gas. Patterning techniques described in reference to FIGs. 5A-6B can be applied to such systems as an approach to separating the contributions of respective species effects (e.g., energy, species flux, penetration depth, etc.) on important etch parameters (e.g., planarity, removal rate, selectivity, etc.).

[0100] FIG. 26 is a block diagram illustrating an example process 2600 for processing a sample using a beam of ions, in accordance with some embodiments of the present disclosure. FIG. 26 illustrates the example process and the corresponding system context in which such a process can be implemented. The process can be carried out by a charged-particle beam apparatus configured to generate, deflect, and disperse a mixed-gas ion beam to selectively modify the surface of a sample, as described in more detail in reference to FIGs. 1-4F. In some embodiments, the apparatus operates automatically under the control of electronics executing stored instructions. In some embodiments, operator input can initiate, guide, or moderate the operations of the process 2600. Although FIG. 26 depicts the process in a particular order for clarity, the order is not limiting; one or more operations may be rearranged, performed in parallel, repeated, and / or omitted. One or more operations can precede and / or follow the operations of process 2600. For example, operations for sample loading, chamber preparation, sample characterization, plasma source calibration, optical alignment, data fusion, visualization, processing, etc., may be included.

[0101] At operation 2605, the process 2600 includes extracting a beam of ions from a mixture of a first gas and a second gas. The first gas can be relatively heavy (e.g., xenon, krypton, or argon), while the second gas can be relatively light (e.g., oxygen, nitrogen, and / or nitrous oxide). The resulting ion beam includes relatively heavy ions derived from the first gas andrelatively light ions derived from the second gas. In some embodiments, the relatively heavy ions are characterized by an atomic mass of 36 AMU or greater, while the relatively light ions are characterized by an atomic mass less than 36 AMU. In further embodiments, the relatively light ions include multiple ion species having different respective mass-to-charge ratios, allowing the apparatus to direct distinct species to different regions of the surface.

[0102] At operation 2610, the beam of ions is deflected in accordance with a deflection pattern. The deflection may be achieved by deflection electrodes (e.g., deflector 330 of FIG. 3A) applying time-varying control signals to produce a linear raster, circular raster, or other trajectory across the surface of the sample, as described in more detail in reference to FIGs 4A-4F. In some cases, the scan sequence is arranged such that the relatively heavy ions impinge upon a portion of the surface prior to the relatively light ions, or alternatively such that the relatively light ions impinge upon the portion of the surface prior to the relatively heavy ions, As described in more detail in reference to FIGs. 5A-7. The deflection pattern can describe both a region of the surface to be processed and the direction and orientation of the at least partially dispersed beamlets (e.g.. beamlets 805, 810 of FIG. 8A). In some embodiments, operation 2610 is repeated as part of overlaying treatment regions (e.g., portions 800 of FIG. 8C) to control the sequence of surface processing by constituent ions of the beam.

[0103] At operation 2615, the deflected beam is directed through an electromagnetic field oriented obliquely relative to the beam axis. The electromagnetic field, generated for example by coils or magnets, applies a Lorentz force that at least partially disperses the trajectories of the ions in space. Control circuitry can modulate the electromagnetic field in accordance with the scan pattern (e.g.. dispersal that varies with the scan). In some embodiments the Lorentz force is reduced to substantially zero during a portion of the pattern to provide additional control over the manner in which the surface is processed by ions of the beam. As described in more detail in reference to FIGs. 9A-9B, the electromagnetic field can be modulated to control the extent of overlap in the processing regions on the sample surface.

[0104] As the at least partially dispersed beam is directed toward the sample surface, the relatively light ions process a first portion of the surface while the relatively heavy ions process a second portion of the surface. These portions may be partially coextensive, noncontiguous, or otherwise distinct depending on the dispersal configuration. In embodiments where multiple light ion species are present, the dispersal pattern may separate them such that a third portion ofthe surface is processed by a second light ion species, thereby enabling differentiated treatment of multiple regions within the same cycle.

[0105] In certain implementations, the apparatus further includes a gas injection system for introducing a precursor material to the vicinity of the surface. Interaction of the precursor with the ion beam may induce a reaction that either deposits material onto the surface or removes material therefrom, depending on the precursor chemistry and the incident ion species. The combination of controlled deflection, selective dispersion, and optional precursor delivery enables a wide range of additive or subtractive processes, such as milling, etching, or deposition. Advantageously, the example process 2600 provides a flexible technique in which ions of differing m / z ratios are automatically separated and directed to different portions of a sample, allowing highly controlled, multi-species, and multi-region processing.

[0106] In the preceding description, various embodiments have been described. For purposes of explanation, specific configurations and details have been set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to one skilled in the art that the embodiments may be practiced without the specific details. Furthermore, well-known features may have been omitted or simplified in order not to obscure the embodiment being described. While example embodiments described herein center on charged particle beam systems, and dual-beam FIB systems in particular, these are meant as non-limiting, illustrative embodiments. Embodiments of the present disclosure address analytical instruments systems for which a wide array of material samples can be analyzed to determine chemical, biological, physical, structural, or other properties, among other aspects, including but not limited to chemical structure, trace element composition, or the like. Further, embodiments of the present disclosure can be applied in systems configured for automated (e.g., performing one or more processes or operations without human involvement), pseudo-automated (e.g., performing one or more processes or operations with limited human involvement and / or with human initiation), and / or manual processes or operations for sample preparation (e.g., in lamella preparation) workflows, for example, as would be used in metrology of semiconductor samples.

[0107] Some embodiments of the present disclosure include a system including one or more data processors and / or logic circuits. In some embodiments, the system includes a non-transitory computer readable storage medium containing instructions which, when executed on the one or more data processors and / or logic circuits, cause the one or more data processors and / or logic circuits to perform part or all of one or more methods and / or part or all of one ormore processes and workflows disclosed herein. Some embodiments of the present disclosure include a computer-program product tangibly embodied in non-transitory machine-readable storage media, including instructions configured to cause one or more data processors and / or logic circuits to perform part or all of one or more methods and / or part or all of one or more processes disclosed herein.

[0108] The terms and expressions which have been employed are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the claims. Thus, it should be understood that although the present disclosure includes specific embodiments and optional features, modification and variation of the concepts herein disclosed may be resorted to by those skilled in the art. and that such modifications and variations are considered to be within the scope of the appended claims.

[0109] Where terms are used without explicit definition, it is understood that the ordinary meaning of the word is intended, unless a term carries a special and / or specific meaning in the field of charged particle microscopy systems or other relevant fields. The terms “about” or “substantially” are used to indicate a deviation from the stated property within which the deviation has little to no influence of the corresponding function, property, or attribute of the structure being described. In an illustrated example, where a dimensional parameter is described as “substantially equal” to another dimensional parameter, the term “substantially” is intended to reflect that the two parameters being compared can be unequal within a tolerable limit, such as a fabrication tolerance or a confidence interval inherent to the operation of the system. Similarly, where a geometric parameter, such as an alignment or angular orientation, is described as “about” normal, “substantially” normal, or “substantially” parallel, the terms “about” or “substantially” are intended to reflect that the alignment or angular orientation can be different from the exact stated condition (e.g., not exactly normal) within a tolerable limit. For numerical values, such as diameters, lengths, widths, or the like, the term “about” can be understood to describe a deviation from the stated value of up to ±10%. For example, a dimension of “about 10 mm" can describe a dimension from 9 mm to 11 mm.

[0110] The description provides exemplary embodiments, and is not intended to limit the scope, applicability or configuration of the disclosure. Rather, the ensuing description of the exemplary embodiments will provide those skilled in the art with an enabling description forimplementing various embodiments. It is understood that various changes may be made in the function and arrangement of elements without departing from the spirit and scope as set forth in the appended claims. Specific details are given in the description to provide a thorough understanding of the embodiments. However, it will be understood that the embodiments may be practiced without these specific details. For example, specific system components, systems, processes, and other elements of the present disclosure may be shown in schematic diagram form or omitted from illustrations in order 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

CLAIMSWhat is claimed is:

1. A method for processing a sample, the method comprising:extracting a beam of ions from a mixture of a first gas and a second gas, the beam comprising a composition of relatively heavy ions and relatively light ions;deflecting the beam of ions in accordance with a deflection pattern;directing the beam of ions through an electromagnetic field oblique relative to an axis of the beam, the electromagnetic field being configured to at least partially disperse the beam in space, such that the deflection pattern causes the beam of ions to process a first portion of a sample surface by the relatively light ions and a second portion of the sample surface by the relatively heavy ions.

2. The method of claim 1, wherein the first portion and the second portion are partially coextensive.

3. The method of claim 1, wherein the first portion and the second portion are noncontiguous.

4. The method of claim 1, wherein the method further comprises modulating the electromagnetic field in accordance with the deflection pattern.

5. The method of claim 4, wherein the magnetic field is substantially zero for at least a portion of the deflection pattern.

6. The method of claim 1, wherein the deflection pattern defines a translation of the at least partially dispersed beam over the sample surface such that the second portion is also processed by the relatively light ions.

7. The method of claim 6, wherein the relatively heavy ions irradiate a specific location of the sample surface prior to the relatively light ions.

8. The method of claim 6, wherein the relatively light ions irradiate a specific location of the sample surface prior to the relatively heavy ions.

9. The method of claim 6, wherein the raster comprises a circular raster.

10. The method of claim 1, wherein the relatively heavy ions are extracted from the first gas and the relatively light ions are extracted from the second gas.

11. The method of claim 1, wherein the first gas is a relatively inert gas and the second gas is a relatively reactive gas.

12. The method of claim 11, wherein the first gas comprises xenon, krypton, argon, or neon.

13. The method of claim 11, wherein the second gas comprises hydrogen, oxygen, nitrogen, ammonia, or nitrous oxide.

14. The method of claim 1, wherein the relatively heavy ions are characterized by a first atomic mass of 36 AMU or greater, and wherein the relatively light ions are characterized by a second atomic mass smaller than 36 AMU.

15. The method of claim 1, wherein the relatively light ions include a first ion species and a second ion species, characterized by different respective mass / charge (m / Z) ratios.

16. The method of claim 15, wherein the deflection pattern configures the beam of ions to process the first portion by the first ion species and further configures the beam of ions to process a third portion of the sample surface by the second ion species.

17. The method of claim 16, wherein the third portion, the second portion, and the first portion are non-contiguous.

18. The method of claim 1, further comprising:directing a precursor to a vicinity of the surface of the sample; andinducing a reaction of the precursor at the first portion or the second portion, the reaction resulting at least in part due to energy released by interactions of the ions of the beam with the precursor.

19. The method of claim 18, wherein the reaction forms a deposit on the surface of the sample.

20. The method of claim 18, wherein the reaction removes material from the surface of the sample.

21. The method of claim 1, wherein the electromagnetic field is applied to the beam of ions between an exit of a charged particle beam column and the sample surface.

22. A Focused Ion Beam (FIB) system, comprising:one or more ion sources;control circuitry operably coupled with the one or more ion sources; andone or more machine-readable media, storing executable instructions for operating the FIB system that, when executed, cause the control circuitry to perform operations comprising:extracting a beam of ions from a mixture of a first gas and a second gas, the beam comprising a composition of relatively heavy ions and relatively light ions;deflecting the beam of ions in accordance with a deflection pattern;directing the beam of ions through an electromagnetic field oblique relative to an axis of the beam, the electromagnetic field being configured to at least partially disperse the beam in space, such that the deflection pattern causes the beam of ions to process a first portion of a sample surface by the relatively light ions and a second portion of the sample surface by the relatively heavy ions.

23. The FIB system of claim 22, wherein the operations further comprise operations implementing the methods of claims 2-21, alone or in combination.

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