Fast mode switching for charged particle beam device

Abstract

A method of rapidly switching between a first imaging or data acquisition mode and a second imaging or data acquisition mode within a charged particle beam (CPB) microscope, the method comprising: activating a switchable electrostatic multipole of the CPB microscope to cause the CPB microscope to generate or to enable the CPB microscope to generate a first set of one or more images or data sets comprising information related to a sample according to the first imaging or data acquisition mode; and deactivating the switchable electrostatic multipole to cause the CPB microscope to generate or to enable the CPB microscope to generate a second set of one or more images or data sets comprising information related to the sample according to the second imaging or data acquisition mode.

Description

Technical Field

[0001] This application generally relates to charged particle beam microscopy and charged particle beam microscopy, and more specifically to transmission electron microscopy (TEM) and microscopes used therein, as well as scanning transmission electron microscopy (STEM) and microscopes used therein.

[0002] By incorporating references

[0003] All patents, patent applications, publications, and other articles mentioned herein are incorporated herein by reference in their entirety, as if fully described herein. Background Technology

[0004] Many biological, chemical, and chemical analysis techniques require spatially resolved data relating to the area or volume distribution of various structures, molecules, and / or elements within one or more samples. Electron microscopy, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning transmission electron microscopy (STEM), is considered a highly versatile set of techniques for obtaining a wide range of useful measurements associated with extremely small samples. In many cases, a single electron microscope can be configured to obtain complementary measurements of different properties of a sample by switching between different operating modes, each probing a different property of the sample. For example, a TEM or SEM may routinely operate in both imaging and diffraction modes, where the configuration of sample features (e.g., shape, grain boundaries, etc.) is recorded in imaging mode, and crystallinity, crystal structure, and molecular structure can be determined from diffraction mode. Some specially configured SEM and TEM instruments may additionally be able to operate in one or more spectral modes (e.g., energy dispersive spectroscopy, commonly abbreviated as EDS; electron energy loss spectroscopy, abbreviated as EELS; cathodoluminescence spectroscopy, CL, etc.), in which the elemental composition or other physical properties of a sample can be determined. A less common operating mode for TEM equipment is the alignment mode, in which the laser beam is aligned relative to the electron beam for use with an image contrast enhancement laser phase plate.

[0005] Figure 1A is a schematic diagram of the conventional axial ray paths and field ray paths through the understage assembly 15 (i.e., the image projection system) of a transmission electron beam microscope capable of being configured in either a sample image generation mode or a diffraction pattern generation mode. The specific ray paths shown in Figure 1A are related to diffraction pattern generation. Axial rays 4 are generated by electrons scattered at an angle to the incident axis 10 of the electron beam 9 from the sample (not shown in Figure 1A but positioned on the sample plane 1). These axial rays 4 are focused into a real image at the intermediate image plane 7 by the objective system 2. A projection lens system 3, which may include more than one lens, is positioned on the side of the intermediate image plane 7 opposite to the side from which the electrons are focused onto the image plane. Although each of the objective system 2 and the projection lens system 3 may include several individual lenses, for simplicity, only a single representative lens is shown in each example and in other examples of lenses mentioned herein. As depicted in Figure 1A, the projection lens system 3 is positioned and operated such that the focal length of the projection lens system is greater than the distance between the intermediate image plane 7 and the projection lens system 3.

[0006] Under the operation shown in Figure 1A, axial ray 4 is not focused at detector plane 8 and therefore does not form an image of the sample. Instead, field ray 5, which causes electron beam 9 to be focused at detector plane 9, enters and passes through objective lens 2 along a trajectory substantially parallel to the axis 10 of the electron microscope column. Objective lens system 2 focuses field ray 5 at the back focal plane 6 of objective lens. Without any interaction between the field ray electrons and the sample that alters their trajectory, a single small spot will be produced at the back focal plane 6 of objective lens by focusing, which is an image of the electron source (not shown in the figure). However, the actual image appearing at the back focal plane 6 is highly sensitive to angular deviations of some rays that may occur due to interactions between electrons and the sample. Such interactions include electron scattering and, in the case of crystalline samples, electron diffraction, shown in Figure 1B as scattering beam cone 105, which is an enlarged view of a portion of Figure 1A. Therefore, in the case of a crystal, the real image at the back focal plane 6 comprises multiple focused spots, each of which can be generated by a separate diffraction beam.

[0007] The aforementioned positioning and operation of the projection lens system 3 allows the focused image of the back focal plane 6 to be transferred or imaged onto the detector plane 8, where it can be acquired as a diffraction pattern. During the acquisition of the diffraction pattern, an adjustable aperture can be positioned at the intermediate image plane 7 (also referred to as the “selected aperture” plane) to control the area of ​​the sample from which the diffracted electron beam is collected. Therefore, the intermediate image plane is also commonly referred to as the “selected aperture” plane. It should be remembered that the depiction in Figure 1A is highly schematic. In practice, the understage assembly 15 may include one or more additional lenses that magnify or correct the image projected onto the detector plane 8. To obtain an image of the sample rather than a diffraction pattern, the intensity of the transfer lens system 3 and any additional understage lenses can be routinely adjusted by adjusting the lens current of the magnetic lens, such that a real image of the sample at the intermediate image plane 7 formed by the axial rays 4, 104 is projected onto the detector plane, preferably in a magnified form. Such adjustment simultaneously causes the field ray 5 to defocus at the detector plane.

[0008] For many years, conventional methods for switching between imaging and diffraction modes have been advantageously used in TEM research for the purpose of studying the interatomic structure of various molecular and crystalline materials. However, in recent years, it has been recognized that conventional mode-switching methods are insufficient for studies where both modes may be available simultaneously or where extremely rapid switching between modes is required. For example, U.S. Patent Publication 2021 / 0302333-A1 describes a method for determining phase and intensity information from electrons observed in the diffraction plane by interfering an electron beam with a simultaneously generated second reference electron beam. To implement such a method, the inventors of the aforementioned publication utilize a TEM system including a “dicfocal beamformer” device as described in U.S. Patent Publication 2021 / 0305007-A1. Referring to the same dicfocal beamformer device, U.S. Patent Publication 2021 / 0305010-A1 teaches a method in which two electron beams are simultaneously directed onto a sample during its operation, wherein both diffraction and imaging are performed to identify sample movement during gradual tilting of the sample, while data for three-dimensional molecular or crystallographic reconstruction is collected.

[0009] Figure 2 depicts a bifocal multibeam charged particle transmission microscope system 100 as described in U.S. Pre-Authorization Publication 2021 / 0305010-A1. The depiction in Figure 2 is a schematic cross-section of the microscope system taken parallel to the xz plane (wherein, by convention, it is assumed that...). zThe axis is parallel to the generally vertically oriented principal axis 110 of the optical column (not illustrated) of system 100. Components housed within the optical column are configured to form two charged particle beams with different focal properties. The optical column includes a charged particle source 106 and other optical components such as a bifocal beamformer 112, a focusing element 120, a focusing column 126, a multipole element 124, and a miniature condenser optical system 128. In some examples, one or more lenses are positioned between the charged particle source 106 and the bifocal beamformer, allowing tuning of the current in the two beams. These lenses are preferably electrostatic lenses.

[0010] According to the teachings of U.S. Publication 2021 / 0305010-A1, a charged particle beam 111 generated by a charged particle source 106 is split into a first charged particle beam 101 and a second charged particle beam 102 by a bifocal beamformer positioned downstream of the charged particle source 106. The first charged particle beam 101 is an axial beam traveling along the main axis 110 of an optical column. The main axis 110 may be the emission axis of the charged particle source 106. The second charged particle beam 102 is an off-axis beam traveling along an axis 161 different from the main axis 110. The bifocal beamformer 112 modifies the focal properties of at least one of the first and second charged particle beams such that the first and second charged particle beams have different focal properties. The angle 163 between the main axis 110 of the second charged particle beam leaving the dual-focus beamformer 112 and the beam axis 161 is greater than the angle 162 between the main axis 110 and the beam axis 160 of the portion of the charged particle beam 111 that forms the second charged particle beam.

[0011] According to the teachings in U.S. Publication 2021 / 0305010-A1, a dual-focus beamformer can be a microelectromechanical system (MEMS) or an aperture lens array. To alter the focal properties of at least one charged particle beam in a charged particle beam, the dual-focus beamformer can apply at least a quadrupole lensing effect to at least one charged particle beam in the beam. This quadrupole lensing effect focuses, astigmatizes, and / or otherwise modifies at least one beam in the beam such that the corresponding focal properties of the beams are different. The quadrupole lensing effect can focus a second charged particle beam in the xz plane and extend the second charged particle beam in the yz plane. The dual-focus beamformer can be further configured to generate at least a dipole electromagnetic field that deflects at least one beam in the beam.

[0012] After exiting the bifocal beamformer 112, both the first and second charged particle beams sequentially pass through the focusing element 120, the multipolar element 124, the focusing column 126, the condenser optics system 128, and the sample front objective 130, subsequently illuminating the sample 14. When the sample 14 is not tilted, it is located at the sample plane 154. The sample plane 154 is a plane orthogonal to the principal axis 110. The focusing element 120, positioned downstream of the bifocal beamformer, accelerates / decelerates, focuses, and / or guides the first charged particle beam 101 and the second charged particle beam 102 toward the focusing column 126, which is also positioned downstream of the focusing element 120. The focusing element 120 may include an accelerator 122 that focuses and accelerates the charged particle beams.

[0013] A multipole element 124 is positioned at the focal plane of the first charged particle beam between the focusing component 120 and the focusing column 126 to adjust the beam shape of the second charged particle beam. The multipole element 124 does not affect the first charged particle beam. The multipole element 124 may be an astigmatism reducer used to apply a quadrupole lens effect complementary to the quadrupole lens effect of the bifocal beamformer, so as to make the profile of the second charged particle beam cylindrically symmetrical. The combined action of the bifocal beamformer 112 and the multipole element 124 results in the first and second charged particle beams having different focal planes near the sample plane 154.

[0014] As taught in U.S. Publication 2021 / 0305010-A1, the focusing column 126 and the condenser optics system 128 bring the deflected second charged particle beam close to the main axis 110. The first and second charged particle beams are focused at different planes (152 and 151) upstream of the sample front objective 130. Both the first and second charged particle beams illuminate the region of interest of the sample after passing through the sample front objective 130, which is positioned downstream of the condenser optics system 128. The beam axes of the first and second charged particle beams may intersect at the sample plane 154. Either the first or second charged particle beam may be convergent (e.g., focused) or non-convergent at the sample plane. The second charged particle beam impinges on the sample 14 mounted on the sample holder 13 at a non-zero tilt angle relative to the first charged particle beam.

[0015] Detector 144 is positioned downstream of projection optics 132, where a diffraction pattern is focused onto the detector via a sample rear objective 131 and projection optics 132. Sample front objective 130 and sample rear objective 131 can be combined to form a magnetic immersion lens. Unscattered beams can be blocked by a beam blocker 17 positioned between projection optics 132 and detector 144. Scattered charged particles 103 pass through projection lens 132 and form a diffraction pattern at a first region of detector 144. Collected scattered charged particles (such as scattered electrons) form diffraction patterns, such as selected area electron diffraction (SAED) patterns. A second beam of charged particles forms a sample image at a second region of detector 144. The first and second regions are offset from each other; that is, the center positions of the first and second regions are different. The total magnification of the bifocal image, which may include both the sample image and the diffraction pattern, can be adjusted by the projection system. The sample image may show the 2D outline or shape of the crystal.

[0016] Employing the aforementioned dual-beamformer within a transmission electron microscope requires complex modifications to the existing microscope and incurs associated additional costs. Furthermore, known charged particle beam mode-switching techniques are plagued by hysteresis, which delays the time to acquire reliable data after the switching event. To study samples that have moved (intentionally or unintentionally), degraded, decomposed, reacted, or otherwise changed during microscopy, faster mode switching is required. Therefore, in the field of charged particle beam microscopy, there is a need for methods that allow for faster switching between imaging and diffraction modes using simple components that do not require significant modifications to existing systems. Summary of the Invention

[0017] The inventors have recognized that rapid switching of operating modes can be achieved by activating and deactivating a small number of additional electrostatic multipole components (e.g., a single electrostatic multipole component) and optionally one or more astigmatism-eliminating components (i.e., magnetic multipole components), which are incorporated into the otherwise conventional charged particle beam path of an electron microscope. In particular, the electrostatic multipole components can be rapidly switched between an activated and inactive state. For example, using such switchable electrostatic multipole components, at the time of writing, it is possible to achieve a switching time of less than 50 nanoseconds, resulting in a cycle time of less than 100 nanoseconds. Using such rapidly switchable optics, it is possible to generate pseudo-simultaneously superimposed images of charged particle beams, where each image is obtained using a different operating mode. As used herein, the term "pseudo-simultaneous" means that two or more modes can be generated within a typical camera frame time (e.g., 1 ms to 10 ms) at a certain duty cycle (e.g., using a 1:10 duty cycle of two superimposed modes, to be determined by the user). For example, it is attractive to generate diffraction patterns during beam retraction time using scanning transmission electron microscopy (STEM).

[0018] According to a first aspect of this disclosure, a method for rapidly switching between a first imaging or data acquisition mode and a second imaging or data acquisition mode within a charged particle beam (CPB) microscope is described, the method comprising: Activating a switchable multipole element of the CPB microscope, wherein the switchable multipole element is configured to generate a quadrupole field when activated, so as to enable the CPB microscope to generate a first set of one or more images or datasets, the first set of one or more images or datasets including sample-related information according to the first imaging or data acquisition mode; and Deactivate the switchable multipole element to enable the CPB microscope to generate a second set of one or more images or datasets, or to enable the CPB microscope to generate a second set of one or more images or datasets, the second set of one or more images or datasets including information related to the sample according to the second imaging or data acquisition mode.

[0019] The switchable multipole element can be a switchable electrostatic multipole element. The switching time of the switchable electrostatic multipole element may be no greater than 100 milliseconds, or alternatively no greater than 10 milliseconds, or alternatively no greater than 1 millisecond, or alternatively no greater than 500 microseconds, or alternatively no greater than 10 microseconds, or alternatively no greater than 1 microsecond, or alternatively no greater than 50 nanoseconds, or alternatively no greater than 50 nanoseconds. The switchable multipole element configured to generate a quadrupole field may be positioned at or near the selected aperture plane of the understage assembly of the charged particle beam microscope system. Optionally, an additional multipole element (astigmatism reducer or electrostatic multipole element) may be positioned at or near the back focal plane of the condenser lens of the understage assembly. The additional multipole element may remain active when the switchable multipole element located at or near the selected aperture plane switches from active to deactivated and vice versa.

[0020] According to some implementation schemes, the switching time of the switchable multi-pole element is no more than 100 milliseconds, or alternatively no more than 10 milliseconds, or alternatively no more than 1 millisecond, or alternatively no more than 500 microseconds, or alternatively no more than 10 microseconds, or alternatively no more than 1 microsecond, or alternatively no more than 500 nanoseconds, or alternatively no more than 50 nanoseconds.

[0021] According to some implementations, a switchable electrostatic multipole element is repeatedly activated and deactivated according to a duty cycle within a single detector frame time. Each activation causes the CPB microscope to generate a component image according to a first imaging mode, and each deactivation causes the CPB microscope to generate a component image according to a second imaging mode. The superposition of these component images generates a multi-exposure composite image. In such cases, the switchable electrostatic multipole element can be disposed within the image projection system of the CPB microscope, and if so, the image projection system can further include an active astigmatism reducer disposed at or near the back focal plane of the objective lens. Each activation and deactivation of the switchable electrostatic multipole element includes activating and deactivating the electrostatic multipole element positioned at a selected aperture plane of the objective system of the image projection system, and Each activation corresponds to generating an image of the sample, and each deactivation corresponds to generating an electron diffraction pattern from the sample.

[0022] Alternative implementations may include a pair of active astigmatism reducers instead of a single astigmatism reducer, positioned between the back focal plane and the projection lens. The single astigmatism reducer, or alternatively the pair, may remain active while the switchable electrostatic multipole is repeatedly activated and deactivated.

[0023] According to various other embodiments in which switchable electrostatic multipole elements are arranged within the image projection system of a CPB microscope, the image projection system may include a laser phase plate disposed at or near a diffraction plane conjugated to the back focal plane, and the laser beam is guided onto the laser phase plate. Each activation and deactivation involves activating and deactivating a switchable electrostatic multipole element located at or near the image plane conjugate to the sample plane. Each activation causes the detector to acquire a superimposed image of the sample and the laser interference fringes.

[0024] According to various other embodiments of the first aspect of this disclosure, a switchable electrostatic multipole element may be disposed within a CPB microscope column that guides a beam of charged particles onto a sample. In such embodiments, the switchable electrostatic multipole element may be disposed between the focal point of the beam-condensing lens system of the CPB microscope column and the aberration correction system of the CPB microscope column. The activation of the switchable electrostatic multipole element enables the CPB microscope column to deliver the focusing probe beam onto the sample, thereby achieving scanning transmission microscopy (STEM) operation mode. The deactivation of the switchable electrostatic multipole element enables the CPB microscope column to deliver a parallel (or nearly parallel) beam onto the sample, thereby achieving transmission electron microscopy (TEM) operation mode.

[0025] In some cases, the focusing probe beam can be focused into a sub-angstrom diameter spherical probe beam, which is delivered to a selected point on the sample. The aberration correction system may include a hexapole spherical aberration corrector comprising two active magnetic hexapole elements that generate negative spherical aberration correction.

[0026] According to a second aspect of this disclosure, a charged particle beam (CPB) microscope is provided, the CPB microscope comprising: Charged particle beam source; CPB column, which is configured to transport a charged particle beam from a charged particle beam source to a sample; An optical assembly, including a transport optics device configured to transport charged particles transmitted through or scattered by the sample to a detector; and The CPB pillar or the switchable electrostatic multipole member of the optical assembly, wherein the switchable electrostatic multipole member is configured to generate a quadrupole field when activated, such that: Activating the switchable electrostatic multipole component enables the CPB microscope to generate a first set of one or more images or datasets, which includes sample-related information according to a first imaging or data acquisition mode; and Deactivating the switchable electrostatic multipole component enables the CPB microscope to generate a second set of one or more images or datasets, or enables the CPB microscope to generate a second set of one or more images or datasets, which includes information related to the sample according to the second imaging mode.

[0027] The first type of CPB microscope is provided as a transmission electron microscope (TEM), which includes: An image projection system comprising: An objective lens system configured to receive electron beams from the sample and having a back focal plane; A projection lens system is disposed between the objective lens system and the detector; and A switchable electrostatic multipole element, configured to generate a quadrupole field positioned at or near the intermediate image plane of the objective system (e.g., a selected aperture plane). The activation of the switchable electrostatic multipole element projects an image of the sample onto the detector, while the deactivation of the electrostatic multipole element projects a diffraction pattern from the sample onto the detector.

[0028] The image projection system of the TEM may further include: An astigmatism reducer or a second electrostatic multipole element, configured to generate a quadrupole field positioned at or near the back focal plane of the objective lens system when activated. The diffuser or the second electrostatic multipole element remains active during the activation and deactivation of the switchable electrostatic multipole element.

[0029] According to a third aspect of this disclosure, a charged particle beam column is provided for a transmission electron microscope (TEM) or scanning transmission microscope (STEM) system, the charged particle beam column comprising: A switchable electrostatic multipole element, configured to generate a quadrupole field and further configured to be alternately activated and deactivated, is positioned close to a first lens system of the probe beam delivery system, wherein the first lens system is configured to receive the diverging beam from the condenser lens system of the electron microscope. The activation of the switchable multipole element enables the focused charged particle probe beam to be delivered from the charged particle beam delivery system to the sample, and the deactivation of the quadrupole enables the collimated charged particle beam to be delivered from the charged particle beam delivery system to the sample.

[0030] The charged particle beam column may further include: A hexapole spherical aberration corrector is positioned between a switchable quadrupole and the sample, and includes two magnetic hexapole elements that generate negative spherical aberration correction.

[0031] According to a fourth aspect of this disclosure, an improved understage assembly for transmission electron microscopy (TEM) is provided, the understage assembly comprising: an objective lens system; a first transfer lens system positioned downstream of the rear focal plane of the objective lens system; a second transfer lens system disposed at or near an intermediate image plane established by the objective lens system and the first transfer lens system; a laser phase plate disposed near an intermediate diffraction plane; and a laser that guides a laser beam onto the laser phase plate; the improvement includes: A switchable multipole element is configured to generate a quadrupole field when activated and is positioned close to the intermediate image plane, and is configured to be repeatedly activated and deactivated.

[0032] According to any of the foregoing aspects of this disclosure, a switchable multipole element or component configured to generate a quadrupole field when activated may comprise a simple quadrupole element or component. Similarly, according to any of the foregoing aspects, a switchable electrostatic multipole element or component configured to generate a quadrupole field when activated may comprise a simple electrostatic quadrupole element or component.

[0033] According to any of the foregoing aspects of this disclosure, a switchable electrostatic multipole element or component configured to generate a quadrupole field may have a switching time from a deactivated state to an activated state or from an activated state to a deactivated state, the switching time being no more than 100 milliseconds, or alternatively no more than 10 milliseconds, or alternatively no more than 1 millisecond, or alternatively no more than 500 microseconds, or alternatively no more than 10 microseconds, or alternatively no more than 1 microsecond, or alternatively no more than 500 nanoseconds, or alternatively no more than 50 nanoseconds. Attached Figure Description

[0034] The above description and various other aspects of the invention will become apparent from the following description, given by way of example only and with reference to the accompanying drawings which are not drawn to scale, in which: Figure 1A is a schematic depiction of the understage assembly of a transmission electron microscope (e.g., TEM) through which the axial and field ray paths pass, and which is configured in a conventional manner to display the diffraction pattern of the sample. Figure 1B is an enlarged view of a portion of Figure 1A; Figure 2 is an illustration of a known dual-focus multi-beam charged particle system configured to simultaneously provide a first charged particle beam and a second charged particle beam, which can provide an image of the sample from the first charged particle beam and sample-related diffraction information from the second charged particle beam. Figure 3A is a schematic depiction of the axial ray path through a version of the understage assembly of Figure 1A, which, according to this teaching, is modified by including two switchable electrostatic quadrupole optics that, when activated, allow the electron diffraction pattern to be acquired by the detector and, when deactivated, allow an image of the sample to be projected onto the detector. Figure 3B is a schematic depiction of the field ray path through the modified understage assembly of Figure 3A when both electrostatic quadrupole optical components are activated. Figure 4 is a schematic depiction of the field ray path through a second modified version of the understage assembly of Figure 1A, which, according to this teaching, is modified by including an astigmatism reducer and an electrostatic quadrupole optics component at the back focal plane of the objective lens, wherein the electron diffraction pattern is acquired by the detector when the electrostatic quadrupole is not activated. Figure 5A shows an image of a sample generated by the understage assembly of an electron microscope, in which the optical components are arranged as shown in Figure 4, but with two astigmatism reducers and the quadrupole element is deactivated. Figure 5B shows the diffraction pattern obtained using the same system and sample as that used in Figure 5A, but with the electrostatic quadrupole device activated. Figure 6A shows a portion of a set of optical components within a portion of an electron beam illumination column, which are configured and operated in a known manner to deliver a collimated electron beam onto a sample for achieving a transmission electron microscope (TEM) operating mode. Figure 6B is a modified version of the optical component of Figure 6A. According to this teaching, the optical component is modified by including an additional switchable electrostatic quadrupole component, such that the illustrated rays are converted into converging rays at the sample, thereby focusing the beam to a small spot size (as small as subangloft), thus allowing highly magnified images of the sample to be detected in scanning transmission electron microscopy (STEM) operating mode. Figure 7A is a schematic depiction of a set of understage components of a transmission electron beam microscope, provided in a known configuration including a laser phase plate for image contrast enhancement. Figure 7B is a modified version of the understage component of Figure 7A. According to this teaching, the understage component is modified by including a switchable electrostatic quadrupole element at or near the first image plane behind the objective lens, whereby the activation of the quadrupole causes the two field ray focal points to appear on opposite sides of the laser phase plate, thereby allowing the laser stripes to be imaged for the purpose of sample alignment. Figure 8 shows a collection of fringe patterns obtained using a TEM understage configuration that includes a laser phase plate positioned at the diffraction plane and a quadrupole mode switching device positioned upstream of the laser phase plate. The horizontal and vertical panels illustrate the effect of exciting a quadrupole field at two different orientations. Figure 9A is a composite image acquired during the readout of the STEM detector, in which the electrostatic quadrupole is activated for 50% of the time to focus the field rays (as shown in Figure 7B), and in which the quadrupole is deactivated for the remaining 50% of the time (as shown in Figure 7A). The result was obtained by applying a 50 Hz cyclic on / off square wave voltage curve to the quadrupole. Figure 9B is a composite TEM image, including the diffraction pattern and ronchi diagram of the STEM probe used during image acquisition in Figure 9A; Figure 9C is a schematic depiction of the voltage waveform applied during the acquisition of the composite image of Figure 9A; and Figure 10 is a set of block diagrams for a controller and power supply for a microscope system according to certain aspects of this disclosure.

[0035] Figure 11 illustrates a known microelectromechanical system (MEMS) dual-focus beamforming device that can be modified to be used as a MEMS electrostatic quadrupole in this invention.

[0036] Figure 12 illustrates a top view of another MEMS dual-focus beamforming device.

[0037] Figure 13A illustrates a top view of another known MEMS dual-focus beamforming device, which includes seven electrodes and can be modified to be used as a MEMS electrostatic quadrupole in this invention.

[0038] Figure 13B depicts a modified version of the MEMS device of Figure 13A, which can be used as an electrostatic quadrupole in this invention. Detailed Implementation

[0039] The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of the specific patent application and its claims. Various modifications to the described embodiments will be apparent to those skilled in the art, and the general principles herein can be applied to other embodiments. Therefore, the invention is not intended to be limited to the embodiments and examples shown, but is given the broadest possible scope based on the features and principles shown and described. For a more detailed and full understanding of the features of the invention, please refer to Figures 1 through 13 in conjunction with the following description.

[0040] In the description of the invention herein, it should be understood that, unless otherwise implied or expressly understood or stated, words appearing in the singular form encompass their plural counterparts, and words appearing in the plural form encompass their singular counterparts. Furthermore, it should be understood that, unless otherwise implied or expressly understood or stated, for any given component or embodiment described herein, any possible candidates or alternatives listed for that component may generally be used individually or in combination with each other. Moreover, it should be understood that the drawings shown herein are not necessarily drawn to scale, and only some elements may be drawn for clarity of the invention. And, in the various drawings, corresponding or similar elements may be indicated by repeating reference numerals. Unless otherwise expressly stated or implied in the context, all such enumerations of candidates or alternatives should be understood as exemplary, not exhaustive.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, this specification (including the definitions) shall prevail. It should be understood that any quantitative term mentioned in this description is preceded by the implied word "about," such that minor and non-substantial deviations are within the scope of the invention. Whenever "substantially," "about," "approximately," or similar language is explicitly combined with a particular value, it is intended to include, unless otherwise expressly stated, a variation of up to and including 10%. Furthermore, the use of "comprise," "comprises," "comprising," "contain," "contains," and "include," "includes," and "including" is not intended to be restrictive. As used herein, "a" or "an" may also mean "at least one" or "one or more." Furthermore, the use of "or" is inclusive, such that the phrase "A or B" is true when "A" is true, "B" is true, or both "A" and "B" are true.

[0042] As used herein, the term "astigmatism reducer" is specifically used to refer to a magnetic multipole optical component, and the terms "quadrupole" and "multipole" are specifically used to refer to an electrostatic multipole optical component, but these terms are not intended to refer to a dipole optical component. As used herein, when referring to a component of a charged particle beam microscope at a specific location within the charged particle beam microscope, the terms "activated" and "activated" refer to applying a first set of one or more voltages to the electrodes of that component, which modifies the trajectory of charged particles passing through or through that component relative to the trajectory existing if said component were not present at that location, thereby achieving a first desired operating mode. As used herein, when referring to such a component in its location, the terms "deactivated" and "deactivated" refer to applying a second set of one or more voltages (or no voltage) to the electrodes of that component, which makes the trajectory of charged particles passing through or through the component substantially the same as those trajectories would have been if the component were not actually present at that location, thereby achieving a second desired operating mode. In the preceding text, the phrase "makes the trajectory of a charged particle... the same as those trajectories that would have been if the component were not present at that location" is used. substantially "Same" means that the particle trajectory is sufficiently similar to the trajectory that would be achieved without the component, such that any data collected in the second desired operating mode is similar to the data that would have been collected without the component at or above a threshold of the similarity metric and / or at or above a threshold of the data quality metric. Any suitable similarity metric or quality metric may be used.

[0043] The use of optical terms in this document, such as “optics,” “optical device,” “optical,” “beam,” “multi-beam,” “beam path,” “ray,” “multiple rays,” “lens,” “multiple lenses,” “focus,” “focal point,” and “collimation,” is not intended to imply that such optical devices, optical components, beams, rays, lenses, focal points, collimations, etc., involve or are used for the manipulation of photons (i.e., visible and invisible light). The use of such terms also implies the use of photon-transparent materials, such as silica and fluorite, for the purpose of manipulating various beams, rays, etc. Rather, as used herein, these terms refer to beams and rays of charged particles (typically electrons), and the control of the trajectory of such charged particles by means of electromagnetic lenses, objectives, astigmatism reducers, and other components including electrodes. As used herein, the term “quadrupole” includes multi-pole (e.g., hexapole, octapole, etc.) devices configured to primarily generate a quadrupole field. As used herein, a quadrupole device may include an electrostatic quadrupole or a magnetic quadrupole. Furthermore, as used herein, the term “under-stage optics” refers to optical lenses and / or other optical components used to deflect or otherwise manipulate charged particle beams and their ray paths after they have been transmitted through a sample, regardless of the relative position (i.e., above, below, across, etc.) between the sample and such optical lenses and / or other optical components.

[0044] Figure 3A Figures 3 to 3B are schematic diagrams of the axial ray path and field ray path through a modified version 15a of the understage assembly of Figure 1A, modified according to this teaching. Specifically, compared to a conventional assembly (e.g., Figure 1A), the understage assembly 15a is modified by including a first electrostatic quadrupole optic 13a disposed at the rear focal plane 6 of the objective system 2 and a second electrostatic quadrupole optic 13b disposed at the intermediate image plane 7 (i.e., the selected aperture plane of the objective system 2). The first electrostatic quadrupole 13a is optional and, if present, can remain active during mode switching operations. Alternatively, the first quadrupole 13a can be a magnetic quadrupole (i.e., an astigmatism reducer) that remains active throughout the operation. The second quadrupole 13b is an electrostatic quadrupole that can be operated in a "deactivated" or "activated" state for mode switching purposes.

[0045] Figures 3A and 3B illustrate the beam paths of axial and field beam electrons, respectively, when electrostatic quadrupoles 13a and 13b are simultaneously activated. It should be noted that only a few selected beams are illustrated in these and other figures. Each point on the sample irradiated by electron beam 9 will generate numerous beams emanating from the sample in a conical configuration. Figures 3A and 3B Figure 3BThe rays depicted in the other figures represent only a few selected rays emanating from the same common point on the sample (on sample plane 1). As depicted in Figure 3A, the first electrostatic quadrupole 13a is configured to separate and redirect each axial ray into a first sub-ray 4a in the XZ plane and a second sub-ray 4b in the YZ plane.

[0046] When activated, the second quadrupole causes the trajectory of each ray 4a in the x, z plane to propagate from axis 10 between the second quadrupole and detector 8 at the same distance as the corresponding ray 4b in the y, z plane. Therefore, this diagram shows that the axial rays are circular as they pass through the second electrostatic quadrupole 13b and projection lens 3. (Note: Figures 3A to 3B are not directly related to the diagram.) Figure 3B The vertical axis in the figure involves both the x and y dimensions. After passing through the second electrostatic quadrupole, the projections of the axial rays overlap and are therefore represented as ray 4ab. The axial ray 4ab is then focused onto the detector plane 8 as an image of the sample. Thus, as shown, when both electrostatic quadrupoles 13a and 13b are configured in their active state, the sample plane and the detector plane are conjugate to each other, and therefore an image of the sample is projected onto the detector and recorded by the detector. The inventors have discovered that if the first electrostatic quadrupole 13a is removed, deactivated, or otherwise absent, an aastigmatic image of the sample can be projected onto the detector as a usable overview image. In such cases, the beam deflection intensity of the single quadrupole 13b, controlled by the voltage applied to the quadrupole electrodes, will be different from the intensity used in operation with the configuration shown in Figure 3A.

[0047] It should be noted that, according to the configuration illustrated in Figure 3A, if the quadrupole is subsequently deactivated, the detector plane becomes conjugate to the back focal plane 6 of the objective system 2, as indicated by the dashed reverse extrapolation projection lines 11a, 11b. Therefore, simple activation and deactivation of the electrostatic quadrupoles 13a, 13b without other optical adjustments can respectively enable the detector to record either the sample image or the diffraction pattern. Advantageously, by slightly shifting the incident electron beam 9, the image of the sample can be moved to a corner of the detector's field of view without significantly disrupting the diffraction pattern. This allows the user, if desired, to record a double-exposure composite image by obtaining multiple exposures while the quadrupole is activated and deactivated.

[0048] Figure 3B illustrates the beam path of field rays when both quadrupoles 13a and 13b are activated simultaneously, or equivalently, when only quadrupole 13b is activated. Because the first quadrupole 13a is located at the plane where the field rays are focused, its activation does not affect the trajectory of field ray 5 as it crosses that plane. Therefore, the path of field ray 5 remains the same as the corresponding path depicted in Figure 1A between the two quadrupoles. When field ray 5 encounters the second quadrupole 13b, it is split into sub-rays 5a and 5b as shown. Since the various sub-rays 5a and 5b fail to converge to a single focal point at detector plane 8, the detector does not record a diffraction pattern image. Therefore, in general, Figure 3A shows a focused image of the sample at the detector plane, while Figure 3B provides an indication of the magnification associated with that image. As described above, when both quadrupoles are deactivated, the beam path returns to the path shown in Figure 1A, at which point a diffraction pattern image can be recorded.

[0049] Referring again to Figures 3A and 3B, it should be noted that if only quadrupole 13a is activated while quadrupole 13b remains inactive, then since quadrupole 13a is positioned at the back focal plane (i.e., the "diffraction plane") 6 of lens system 2, detector plane 8 becomes conjugate to diffraction plane 6 (see the ray paths labeled 11a, 11b, and 4ab in Figure 3A). In this case, the detector will record the focused diffraction pattern.

[0050] Figure 4 is a schematic depiction of the field ray path through a second modified version of the understage assembly of Figure 1A. This second modification, relative to the modification shown in Figures 3A and 3B, is achieved by replacing the first electrostatic quadrupole (i.e., quadrupole 13a) with an astigmatism canceller 14a (e.g., an electromagnetic quadrupole), whereby the astigmatism canceller 14a is positioned at the back focal plane of the objective system 2 and remains active at all times. As shown in Figure 4, the operation of the electrostatic quadrupole 13b can be controlled so that the axial ray 4 is ultimately focused onto the detector plane 8, thereby projecting an image of the sample onto the detector plane. Since the basic hardware configuration remains unchanged from that shown in Figures 3A and 3B, except that the first quadrupole is replaced by the astigmatism canceller 14a, the deactivation of the individual electrostatic quadrupole 13b again conjugates the detector plane 8 to the back focal plane 6 of the objective system 2, as indicated by the graphic projection lines 12a, 12b. Therefore, the activation and deactivation of a single electrostatic quadrupole 13b can be used to switch between recording the diffraction pattern and recording the sample image, and vice versa.

[0051] Figure 5A shows a sample image that can be generated by the understage assembly of an electron microscope, where the optical components are arranged as shown in Figure 4, with both the astigmatism reducer 14a and the quadrupole 13b activated. Figure 5B shows a diffraction pattern of a sample obtained using the same system and sample as in Figure 5A, but with 13b activated and the astigmatism reducer remaining active. Therefore, using the configuration shown in Figure 4, it is possible to rapidly switch between diffraction and sample imaging by activating and deactivating only one optical component (i.e., the quadrupole 13b located at the selected aperture plane 7). By switching between the two modes during a single camera exposure of the detector, multiple exposures in which the diffraction pattern and the sample image overlap can be obtained. In an alternative, but less preferred, embodiment, the single astigmatism reducer 14a can be replaced by two astigmatism reducers positioned downstream of the back focal plane 6, such that the combined effect of this pair of astigmatism reducers is the same as and has the same effect as a single astigmatism reducer 14a at the back focal plane. However, this alternative configuration has been found to be less desirable because it has been found to cause some image distortion.

[0052] Figure 6A is a portion of a set of optical components 40 within the beam delivery section of an electron microscope column (not shown) of a transmission electron microscope (TEM) configured and operated in a known manner to deliver a collimated electron beam onto a sample. Figure 6B is a schematic depiction of a modified version of the optical component assembly 40 of Figure 6A, modified in accordance with this teaching. The Z-axis shown in Figures 6A and 6B corresponds to the column axis 10 shown in Figures 1, 3A, 3B, and 4. Figure 2 The axis 110 is shown. The sample plane 49 on which the sample is located is depicted on the right side of each of Figures 6A and 6B.

[0053] An electron source (not shown), along with at least one condenser lens (not shown) and an intermediate lens (not shown), are located to the left of the left side of each of Figures 6A and 6B. The electron source provides an electron stream comprising multiple rays to the optical components of the illumination column. The rays are collimated and subsequently focused by one or more lenses (not shown) located to the left of the leftmost portion of each of Figures 6A and 6B. The leftmost portion of each of these figures is the focal point 59 of the lens (not shown). The path of a single ray 37 is illustrated in Figure 6A. Figure 6B shows the path of the same ray 37 and the paths of individual sub-rays 37a, 37b that can be divided into according to this teaching.

[0054] The known optical assembly 40 includes multiple lenses, the positions of which are labeled L1, L2, L3, ..., L8 in both Figures 6A and 6B. The lenses themselves are not specifically depicted in either Figure 6A or 6B. However, field strength diagrams 41, 42, 43, 44, 45, 46, 47, and 48 graphically indicate the field strength at the corresponding location of each such lens. Four of the lenses, specifically lenses L3, L4, L5, and L6, are included within the known probe aberration corrector 51. The inset in Figure 6A is an enlarged version of the circular region 54 near the sample plane 49, showing the beam manipulation via the various optical components 40, ray 37, and any other rays passing through the focal point 52, with electrons introduced onto the sample as a circularly collimated beam parallel to the Z-axis. As depicted in Figure 6A, the optical components are configured in this way to deliver the collimated beam to the sample for TEM studies.

[0055] The known lens system 51 is a hexapole probe Cs corrector, where Cs is the spherical aberration coefficient. The key components of the probe aberration corrector 51 are magnetic hexapole elements 52 and 53. These hexapole elements generate a strong hexapole field, which is used to generate negative Cs. For parasitic aberration correction (i.e., those caused by mechanical errors), these hexapole elements 52 and 53 also generate relatively weak dipole and quadrupole fields, and these weak fields are deployed in Figures 6A and 6B. For the purposes of the following discussion, these quadrupole fields do not need to be switched; that is, they have the same excitation in both Figures 6A and 6B.

[0056] Figure 6B is a schematic diagram of a modified version of the optical assembly shown in Figure 6A. According to this teaching, the optical assembly 40b is modified relative to the assembly 40 by incorporating an additional quadrupole element 55 in the beam path, adjacent to and directly downstream of the L1 lens. The quadrupole element 55 is configured to split the ray 30 into sub-rays 30a and 30b during operation, which, when acted upon by the existing downstream lenses L2, L3, L4, ..., L8 and quadrupoles 52, 53, refocus into a finely focused sub-angstrom probe beam on the sample plane. Furthermore, the inventors have found that the ray path modification shown in Figure 6B does not interfere with the normal function of the aberration corrector 51. Therefore, by activating a single quadrupole optical element 55, the operating mode of the electron microscope system can be rapidly switched to atomic resolution STEM, STEM-EDS, or STEM-EELS modes. Deactivation of the quadrupole 55 switches the operating mode back to TEM mode. Furthermore, the microscope operation can be rapidly switched between different operating modes as needed.

[0057] Figure 7A is a schematic depiction of a set of understage components for a transmission electron beam microscope, provided in a configuration including a laser phase plate for image contrast enhancement. Figure 7A also shows the ray paths of a representative field ray 79 and a representative axial ray 78. The understage components illustrated in Figure 7A are positioned in the region between the sample plane 71 and the diffraction plane 72. The components of the understage assembly in Figure 7A include an objective lens system 73, a first transfer lens system 74 disposed at or near a first intermediate image plane of the objective lens system, and a second transfer lens system 75 disposed at or near the intermediate diffraction plane where the field ray 79 converges. It should be remembered that this illustration is highly schematic, and each component described as a "lens" may actually comprise a multi-component lens system or lens assembly.

[0058] In addition to the aforementioned components, a laser phase plate 77 is also included under the stage. This laser phase plate is also positioned at or near the intermediate diffraction plane where the second transfer lens 75 is located. Typically, the laser phase plate is a photonic optical cavity placed in the path of the electron beam. The laser beam emitted from the laser (not shown) is further amplified in the laser cavity and forms a tight focal point coinciding with certain selected electron beam paths. The energy of the photonic standing waves generated by the laser beam within the cavity exerts a substantial force on the electrons, causing some electrons to undergo a phase shift. The interference between the phase-shifted and non-phase-shifted electrons is used to enhance the contrast in the TEM image of the sample.

[0059] One of the main difficulties in using a phase plate is aligning it with the electron beam, which requires precise control over the position and orientation of the phase plate. The inventors have discovered, as depicted in FIG7B, that by incorporating a switchable electrostatic quadrupole element 76 adjacent to the first transfer lens system 74 at the first intermediate image plane of the objective lens system, laser interference fringes can become visible at the image plane. Therefore, the pattern of the interference fringes can be detected and displayed simultaneously with the alignment adjustment of the laser beam.

[0060] Referring now to Figures 7A and 7B, it can be observed that regardless of the presence or activation of the quadrupole 76, the axial ray 78 remains focused on the diffraction plane 72. The axial ray path is unaffected by the presence or activation of the quadrupole 76 because the quadrupole is positioned on the plane where the axial ray 78 is focused by the objective system 73. In contrast, if the quadrupole 76 is absent (Figure 7A) or otherwise deactivated, the field ray 79 is focused onto the plane of the laser phase plate 77 at the diffraction plane 75; this configuration is referred to herein as the "on-plane" configuration. In the on-plane configuration, image contrast is optimized if one of the antinodes in the laser focus coincides with the focus of the field ray 79.

[0061] If the quadrupole 76 is present and activated, each field ray 79 is split into a first ray 79a and a second ray 79b. Due to this splitting, field ray 79b (the dotted line in FIG. 7B) is focused at the upper focal plane 82 by the first transfer lens system 74. Simultaneously, field ray 79a (the dashed line) is focused at the lower focal plane 83 by both the first transfer lens system 74 and the second transfer lens system 75. This condition is referred to herein as an “out-of-plane” configuration. If, in the out-of-plane configuration, the switchable electrostatic quadrupoles are configured such that the upper focal plane 82 and the lower focal plane 83 are substantially equidistant from the nominal focal plane 75 depicted in FIG. 7B, the image of the sample will be superimposed with the fringes from the laser as multiple sets of bright and dark bands in the electron microscope image (see, for example, FIG. 8). Under such conditions, it is possible to observe spatial effects of destructive and constructive laser standing wave interference within the optical cavity at the detector plane conjugate to the image plane. Note that since the electrostatic quadrupole 76 is located at or near the image plane 74, the activation and deactivation of the electrostatic quadrupole does not affect the image of the object, but only affects the visibility of the laser stripes superimposed on the image.

[0062] The pattern of interference fringes observed in the out-of-plane configuration provides information related to the relative alignment between the laser beam and the electron beam. The out-of-plane fringe pattern that appears when switching from a well-aligned on-plane configuration to an out-of-plane configuration can be used as a reference image to maintain good alignment between the electron and laser beams. Switching between the on-plane imaging mode and the out-of-plane mode that shows the interference fringes can be performed using a fast-response switching device, such as an electrostatic quadrupole 76. This procedure allows analysts to rapidly alternate between viewing the fringes and viewing the sample image to obtain optimal image contrast and correlate image contrast with the fringe pattern in near real-time.

[0063] Similarly, in microscopic studies of samples that have been moved (intentionally or unintentionally), degraded, decomposed, reacted, sublimated, or otherwise altered during the study, the ability to rapidly switch between imaging and diffraction modes using a fast-response switching device as described herein may be necessary. In such cases, alternating modes at a repetition rate equal to or faster than the frame acquisition rate of the camera detector or the scanning repetition rate of the scanning system may be advantageous or even necessary. By making the switching time relatively short relative to the camera frame time, double or multiple exposures can be performed. For example, Figure 9A is a composite image acquired by scanning a sample using a STEM device, which includes multiple diffraction image bars 92 that are interleaved with sample image bars 91, wherein switching between sample imaging and diffraction imaging is controlled by applying a 50 Hz voltage waveform, as shown in Figure 9C, to an electrostatic quadrupole switching device. Each set of bars 91, 92 can be compared and / or correlated separately to monitor changes in the sample (if any) or microscopic performance (if any) during data acquisition. Figure 9B is a composite image obtained by assembling STEM image strips 91 into a single image 93 of the sample and assembling diffraction image strips 92 into a Renzi diagram 94. The shapes, patterns, and symmetries observed in the Renzi diagram indicate the presence and nature (if any) of lenticular aberrations. By analyzing these patterns, it is possible to detect possible image distortions in the sample image 93 and adjust the microscope as needed to correct any aberrations that cause these distortions.

[0064] Figures 11, 12, and 13A depict exemplary dual-focus beamforming apparatuses as described in pre-authorization publication 2021 / 0302333-A1, which can be modified to serve as (e.g., Figure 13B) electrostatic multipoles in devices according to this teaching. Figure 11 shows a cross-section of an example embodiment of an example dual-focus beamforming apparatus 1100, which can be manufactured using the same methods used to manufacture general microelectromechanical systems (MEMS). Specifically, Figure 11 illustrates a cross-section of a MEMS-like device 1100 configured to split a stream of multiple electrons 1102 into a first electron beam 1104 and a second electron beam 1106, and generate an electromagnetic field pattern that applies at least a quadrupole lensing effect to at least the second electron beam 1106. This at least quadrupole lensing effect causes the first electron beam 1104 and the second electron beam 1106 to have different focal properties. For example, a quadrupole lensing effect can exert a positive lensing effect in a meridional plane (e.g., the yz plane) and a negative lensing effect in a perpendicular meridional plane (e.g., the xz plane), thereby causing different variations in focal properties in each of the two meridional planes. Figure 11 illustrates a cross-section through a MEMS device 1100 including a surface layer 1108, an electrode layer 1110, and an optional shielding layer 1112. In Figure 11, the surface layer 1108 is shown as comprising a thin material (e.g., a foil) to which electrons 1102 are incident. In other embodiments, the surface layer 1108 may not correspond to a separate component layer, but may correspond to the upper surface of one or more components of the MEMS device 1100 onto which electrons 1102 are incident.

[0065] Referring again to FIG. 11, surface layer 1108 defines a first entrance 1114 to the first aperture 1116 and a second entrance 1118 to the second aperture 1120. The first entrance 1114 allows a first portion of electrons 1102 (i.e., a first electron beam 1104) to enter the first aperture 1116 and pass through the MEMS device 1100. Similarly, the second entrance 1118 allows a second portion of electrons 1102 (i.e., a second electron beam 1106) to enter the second aperture 1120 and pass through the MEMS device 1100. Surface layer 1108 inhibits the ability of the remaining portion of electrons 1102 to enter and / or pass through the MEMS device 1100.

[0066] Electrode layer 1110 includes a plurality of microelectrodes shaped, positioned, or otherwise configured such that when a corresponding voltage is applied to one or more electrodes, the one or more electrodes generate an electromagnetic field pattern that applies a lensing effect to one or both of the first electron beam 1104 and the second electron beam 1106. The lensing effect modifies the focal properties of the two beams, giving them different corresponding focal properties. One or more of the amplitude of the voltage applied to the electrodes, the shape of the electrodes, and the thickness (L) of the electrodes can be modified to change the intensity of the generated electromagnetic field pattern. According to this disclosure, the electrodes in electrode layer 1110 are configured such that they generate at least a quadrupole electromagnetic field pattern that applies at least a quadrupole lensing effect (i.e., a dipole field, a tetrapole field, a hexapole field, an octapole field, etc.) to the second electron beam 1106. In some embodiments, the electromagnetic field pattern may also apply a dipole field to one or both of the first electron beam 1104 and the second electron beam 1106. Such a dipole field can cause at least one electron in the electron beam to be non-parallel to the emission axis. z The direction of deflection. Figure 11 also illustrates the MEMS device 1100 as including an optional shielding layer 1112 opposite to the surface layer 1108, which is configured to at least partially insulate the first electron beam 1104 from at least a quadrupole lens effect applied to the second electron beam 1106.

[0067] Figure 12 shows a top-down schematic of an example of a MEMS electrostatic multipolar implementation 1200 including four electrodes. Figures 12 and 13 illustrate the first inlet 1114 and the second inlet 1118 defined by the surface layer 1108 in the solid lines. Additionally, Figures 12 and 13 illustrate components of the electrode layer 1110 with dashed lines. Those skilled in the art will recognize that the dashed lines do not necessarily represent exact shapes, but rather indicate the general outline of the electrodes in the electrode layer 1110. Figure 12 shows the radius R of the first inlet 1114. A1 The radius R is smaller than that of the first aperture 1116, which is at least partially defined by the electrode 1202. E1 In one embodiment of the example MEMS device 1200, the radius R A1 It can be at or near 10µm, and the radius R E1 It can be at or near 14 µm or larger. The radius R of the second inlet 1118 A2 The radius R shown in Figure 12 is smaller than that of the second aperture 1120, which is at least partially defined by electrodes 1202, 1204, 1206, and 1208. E2However, in other implementations, the radius R E1 and radius R A1 and / or radius R E2 and radius R A2 One or both of them can be the same. Example implementation 1200 is further shown as having equal and / or approximately equal radii R. A1 and radius R A2 However, this is not necessary for all implementation schemes. The first entrance 1114 and the second entrance 1118 are separated by a distance D.

[0068] During use of the example MEMS device 1200, a voltage can be applied to one or more of the electrodes 1202-1208, causing the electrodes to generate an electromagnetic field that exerts at least a quadrupole lensing effect on the second electron beam. In some embodiments, one or more of the electrodes can be grounded. For example, when the first voltage... V 1. A second voltage is applied to electrode 1204. V When applied to electrode 1208 and electrodes 1202 and 1206 are grounded, the example MEMS device 1200 can generate an electromagnetic field that applies at least a quadrupole lensing effect to the second electron beam. In various embodiments, V 1 and V 2. Each can be greater than -20V and less than +20V, but larger voltages can also be used.

[0069] Figure 13A shows a top-down schematic diagram of an example embodiment 1300 of a MEMS electrostatic multipolar device including seven electrodes. Figure 13A shows the radius R of the first inlet 1114. A1 Smaller than the radius R of the first aperture defined at least partially by electrodes 1302, 1304, 1306 and 1308 E1 Figure 13A illustrates the first entrance 1114 as an axial aperture through which the emission axes 1310 of multiple electrons pass. The radius R of the second entrance 1118 is... A2 Also shown in Figure 13A is the radius R of the second aperture, which is less than that defined at least in part by electrodes 1306, 1312, 1314, and 1316. E2 However, in other implementations, the radius R E1 and radius R A1 and / or radius R E2 and radius R A2 One or both of them can be the same.

[0070] During use of the example MEMS device 1300, voltages can be applied to one or more of electrodes 1302-1308 and 1312-1316, causing the electrodes to generate an electromagnetic field that exerts at least a quadrupole lensing effect on the second electron beam. In some embodiments, one or more of the electrodes can be grounded. For example, when a first set of voltages between -20V and +20V is applied to electrodes 1304, 1308, 1312, and 1316, a second set of voltages between -5V and +5V is applied to electrodes 1302 and 1314, and electrode 1306 is grounded, the example MEMS device 1300 can generate an electromagnetic field that exerts at least a quadrupole lensing effect on the second electron beam.

[0071] The aforementioned known dual-focus beamforming systems 1100, 1200, and 1300 are designed to split a single charged particle beam into separate charged particle beams and independently focus and / or shape two separate beams. However, many charged particle beam systems described herein do not require such complex beam splitting and beam shaping operations. Nevertheless, the structure of known dual-focus beamforming systems can be simplified for use as electrostatic quadrupole devices as described above. For example, Figure 13B illustrates an exemplary electrostatic quadrupole 1350, which includes a subset of the components of the dual-focus beamforming system 1300. Specifically, since it may not be necessary to split the charged particle beam into two separate beams, the second inlet 1118 and its corresponding second aperture can be eliminated from this structure. Eliminating the second aperture and the second inlet also eliminates the need for electrodes 1312, 1314, and 1316, which are located in... Figure 13A The component shown is the dual-focus beamforming apparatus 1300. The resulting simplified apparatus 1350 (FIG. 13B) consists only of an inlet 1114, the circular shape of which is defined by the shapes of the surrounding four electrodes 1302, 1304, 1306 and 1308.

[0072] Those skilled in the art will understand that the dashed lines in Figures 12, 13A, and 13B represent example configurations of the electrodes, and that experiments will provide a variety of electrode configurations (e.g., electrode size, electrode shape, number of electrodes, electrode layout, combinations of voltages applied to the electrodes, etc.) that enable the electrodes to generate an electromagnetic field that applies at least a quadrupole lensing effect to the charged particle beam. By way of example only, those skilled in the art will recognize that applying a first potential... V 1. Applying a second different potential to the opposing electrodes 1302 and 1306 of the electrostatic quadrupole device 1350. V2. Applying a potential to electrodes 1304 and 1308 may correspond to “activation” of device 1350, which can generate a quadrupole lensing effect on a beam of charged particles passing through the aperture. Furthermore, according to this example, applying substantially the same potential to all four electrodes 1302, 1304, 1306, and 1308 may include “deactivation” of device 1350. It should be noted that, as used herein, “applying” a potential to electrodes may include grounding the electrodes and / or allowing the potential of the electrodes to “float.”

[0073] Figure 10 depicts a block diagram of a controller 1000 and a power supply 1600 for a microscope system according to certain aspects of this disclosure. As shown, the controller 1000 includes a processor 1002 communicatively coupled to a memory 1504. The processor 1002 may include one or more processing devices. Non-limiting examples of the processor 1002 include field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), microprocessors, or any combination thereof. The processor 1002 can execute instructions 1510 stored in the memory 1504 to perform operations such as microscope operation, procedures, scanning, and operations associated with the various methods described herein. In some examples, the instructions 1510 may include processor-specific instructions generated by a compiler or interpreter from code written in any suitable computer programming language, such as C, C++, C#, Python, or Java.

[0074] Memory 1504 may include one or more memory devices. Memory 1504 may be non-volatile and may include any type of memory device that retains stored information when power is lost. Non-limiting examples of memory 1504 include electrically erasable and programmable read-only memory (EEPROM), flash memory, or any other type of non-volatile memory. At least some of the memory in memory 1504 may include a tangibly embodied non-transitory computer-readable medium from which processor 1002 can read instructions 1510 via bus 1006. Bus 1006 may be a communication and / or power bus that enables processor 1002 to communicate with memory 1504. The non-transitory computer-readable medium may include electronic, optical, magnetic, or other storage devices capable of providing instructions 1510 or other program code to processor 1502. Non-limiting examples of non-transitory computer-readable media include disks, memory chips, RAM, ASICs, or any other medium from which a computer processor can read instructions 1510.

[0075] The memory 1504 may further include information about parameters 1512 (e.g., calibration, tuning, stage position, beam intensity, etc.), beam scanning controller 1514 (e.g., scan coordinates, stored images, etc.), detector operation (e.g., detector control, sensitivity, etc.), and image rendering apparatus 1520. The controller 1000 may receive information about operating parameters from a charged particle microscope such as a STEM or TEM. At least some of the information about any controller component may be pre-stored. Parameter 1512 may include operating parameters associated with the electron microscope system, such as the desired / primary energy of the electron beam, energy spread of the energy loss spectrum, locking mechanism, feedback loop, etc.

[0076] Any system described herein may include a controller system 1000 that can automatically cause one or more power supplies 1600 to adjust the voltage applied to one or more beam path switching devices, such as one or more electrostatic quadrupoles and / or one or more astigmatism suppressors, as discussed herein, to switch the operating mode of the charged particle beam microscope apparatus from a first operating mode to a second operating mode and / or from a second operating mode to a first operating mode. The controller system may be electronically connected to a computer-readable storage device 1504 that provides the controller system with program instructions 1510, which, when executed by the controller system, cause the controller system to provide a voltage configuration sequence to one or more beam path switching devices, thereby causing the operating mode of the charged particle beam microscope apparatus to repeatedly switch between the first and second operating modes.

[0077] The controller system can also communicate electronically with one or more other components of the charged particle beam microscope apparatus, such as, for example, a sample stage on which a sample of interest is mounted, which can be moved by one or more actuators. In this case, the controller system can be configured to cause one or more power sources to transmit electronic and / or electrical signals to one or more actuators to move the sample stage in coordination with repeated switching of the aforementioned operating modes. The controller system can be instructed to cause these sample stage movements by executing program instructions received from a computer-readable storage device.

[0078] The controller system can also communicate electronically with one or more detector systems of the charged particle beam microscope apparatus and can operable to control the timing of data acquisition by one or more detector systems under the control of program instructions received from a computer-readable memory. For example, when executed by the processor 1002 of the controller system 1000, program instructions 1510 can operable to cause the controller system to cause one or more detector systems to acquire data at specific times coordinated with the switching of the operating modes of the charged particle beam microscope apparatus, as described herein, from a first operating mode to a second operating mode and / or from a second operating mode to a first operating mode.

[0079] Although the invention has been described with reference to the illustrated embodiments, those skilled in the art will readily recognize that variations of the embodiments may exist, and that such variations will be within the scope of the invention. Therefore, many modifications can be made by those skilled in the art without departing from the scope of the invention as described in the claims. For example, various embodiments of the invention may be described by one or more of the following clauses: Clause 1. A charged particle beam column for a transmission electron microscope (TEM) or scanning transmission microscope (STEM) system, said charged particle beam column comprising: A switchable multipole element, configured to generate a quadrupole field when activated and configured to be alternately activated and deactivated, is positioned close to a first lens system of the probe beam delivery system, wherein the first lens system is configured to receive a diverging beam from the condenser lens system of the electron microscope. The activation of the switchable multipole element enables the focused charged particle probe beam to be delivered from the charged particle beam delivery system to the sample, and the deactivation of the switchable multipole element enables the collimated charged particle beam to be delivered from the charged particle beam delivery system to the sample.

[0080] Clause 2. The charged particle beam column as described in Clause 1, further comprising: A hexapole spherical aberration corrector is disposed between the switchable multipole element and the sample, and includes two magnetic hexapole elements that generate negative spherical aberration correction, whereby, when the switchable multipole element is activated, a sub-angstrom diameter circular probe beam is delivered to a selected point on the sample.

[0081] Clause 3. An improved understage optics system for transmission electron microscopy (TEM) or scanning transmission electron microscopy (STEM), the understage optics system comprising: an objective lens system; a first transfer lens system positioned at the back focal plane of the objective lens system; a second transfer lens system disposed at an intermediate diffraction plane established by the objective lens system and the first transfer lens system; a laser phase plate disposed near the intermediate diffraction plane; and a laser that guides a laser beam onto the laser phase plate; the improvement comprising: A switchable multipole element, which is configured to generate a quadrupole field when activated and is positioned close to the objective image plane, and is configured to be repeatedly activated and deactivated.

[0082] Clause 4. The improved under-stage optics system according to Clause 3, wherein the switchable multipole element is a switchable electrostatic multipole element having a switching time of no more than 100 milliseconds, or alternatively no more than 10 milliseconds, or alternatively no more than 1 millisecond, or alternatively no more than 500 microseconds, or alternatively no more than 10 microseconds, or alternatively no more than 1 microsecond, or alternatively no more than 500 nanoseconds, or alternatively no more than 50 nanoseconds.

[0083] Clause 5. The improved under-stage optical system as described in Clause 3, The switchable multipole element is configured, when activated, to cause the detector to receive an image pattern thereon that reflects the effect of laser phase plate operation on the spatial variation of transmitted electron intensity.

[0084] Clause 6. A charged particle beam (CPB) microscope comprising: Charged particle beam source; CPB column, the CPB column being configured to transport a charged particle beam from the charged particle beam source to the sample; A CPB projection assembly, comprising transfer optics that transfer charged particles transmitted through or emitted or scattered by the sample to a detector; and A switchable multipole element, capable of switching between an active and deactivated state and configured to generate a quadrupole field when activated, is disposed within the CPB column or the CPB projection assembly, thereby: Activating the switchable multi-pole element enables the CPB microscope to generate one or more images according to a first imaging mode, or enables the CPB microscope to generate one or more images according to a first imaging mode; and Deactivate the switchable multipole element to enable the CPB microscope to generate one or more images according to the second imaging mode, or enable the CPB microscope to generate one or more images according to the second imaging mode.

[0085] Clause 7. The CPB microscope as described in Clause 6, wherein the switchable multipole element is a switchable electrostatic multipole element having a switching time of no more than 100 milliseconds, or alternatively no more than 10 milliseconds, or alternatively no more than 1 millisecond, or alternatively no more than 500 microseconds, or alternatively no more than 10 microseconds, or alternatively no more than 1 microsecond, or alternatively no more than 500 nanoseconds, or alternatively no more than 50 nanoseconds.

Claims

1. A method for rapidly switching between a first imaging or data acquisition mode and a second imaging or data acquisition mode within a charged particle beam (CPB) microscope, the method comprising: Activate the switchable multipole element of the CPB microscope, wherein the switchable multipole element is configured to generate a quadrupole field when activated, so as to enable the CPB microscope to generate a first set of one or more images or datasets, the first set of one or more images or datasets including sample-related information according to the first imaging or data acquisition mode. as well as Deactivate the switchable multipole element to enable the CPB microscope to generate a second set of one or more images or datasets, or to enable the CPB microscope to generate a second set of one or more images or datasets, the second set of one or more images or datasets including information related to the sample according to the second imaging or data acquisition mode.

2. The method of claim 1, wherein the switchable multipole element is a switchable electrostatic multipole element.

3. The method as described in claim 2, wherein the switching time of the switchable electrostatic multipole element is no greater than 100 milliseconds, or alternatively no greater than 10 milliseconds, or alternatively no greater than 1 millisecond, or alternatively no greater than 500 microseconds, or alternatively no greater than 10 microseconds, or alternatively no greater than 1 microsecond, or alternatively no greater than 500 nanoseconds, or alternatively no greater than 50 nanoseconds.

4. The method of claim 1, wherein the switchable multipole element is repeatedly activated and deactivated according to the duty cycle within a single detector frame time. Each activation causes the CPB microscope to generate a component image according to a first imaging mode, and each deactivation causes the CPB microscope to generate a component image according to a second imaging mode. The superposition of the component images generates a multi-exposure composite image.

5. The method of claim 4, wherein the switchable multipole element is disposed within the image projection system of the CPB microscope, and the image projection system projects a diffraction pattern onto the detector when the switchable multipole element is deactivated.

6. The method of any one of claims 1 to 5, wherein the image projection system further comprises an active astigmatism reducer disposed at the back focal plane of the objective lens. Each activation and deactivation of the switchable multi-pole element includes respectively activating and deactivating the switchable multi-pole element positioned at a selected aperture plane of the objective system of the image projection system, and Each activation corresponds to generating an image of the sample, and each deactivation corresponds to generating a diffraction pattern from the sample.

7. The method of claim 6, wherein the switchable multipole element is a switchable electrostatic multipole element, and the switching time of the switchable electrostatic multipole element is not greater than 100 milliseconds, or alternatively not greater than 10 milliseconds, or alternatively not greater than 1 millisecond, or alternatively not greater than 500 microseconds, or alternatively not greater than 10 microseconds, or alternatively not greater than 1 microsecond, or alternatively not greater than 500 nanoseconds, or alternatively not greater than 50 nanoseconds.

8. The method of claim 5, wherein the image projection system further comprises a pair of active astigmatism reducers disposed between the back focal plane and the projection lens, the pair of active astigmatism reducers having the same effect on the charged particle beam path within the image projection as a single astigmatism reducer disposed at the back focal plane of the objective lens. Each activation and deactivation of the switchable multi-pole element includes respectively activating and deactivating the switchable multi-pole element located at or near the intermediate image plane of the image projection system; and Each activation corresponds to generating an image of the sample, and each deactivation corresponds to generating an electron diffraction pattern from the sample.

9. The method of claim 5, wherein the image projection system includes a laser phase plate disposed at a diffraction plane conjugate to the back focal plane of the objective lens, and the laser beam is guided onto the diffraction plane. Each activation and deactivation includes activating and deactivating a switchable multi-pole element, which is disposed at or near the image plane of the objective lens of the image projection system. Each activation causes the detector to acquire a superimposed image of the sample and the laser interference fringes.

10. The method of claim 9, wherein the switchable multipole element is a switchable electrostatic multipole element, and the switching time of the electrostatic multipole element is not greater than 100 milliseconds, or alternatively not greater than 10 milliseconds, or alternatively not greater than 1 millisecond, or alternatively not greater than 500 microseconds, or alternatively not greater than 10 microseconds, or alternatively not greater than 1 microsecond, or alternatively not greater than 500 nanoseconds, or alternatively not greater than 50 nanoseconds.

11. The method of any one of claims 1 to 5, wherein the switchable multipole element is disposed within a CPB microscope column that guides a beam of charged particles onto the sample.

12. The method of claim 11, wherein the switchable multipole element is disposed between the focal point of the beam-condensing lens system of the CPB microscope column and the aberration correction system of the CPB microscope column. The activation of the switchable multipole element enables the CPB microscope column to deliver a focusing probe beam onto the sample, thereby achieving a scanning transmission microscopy (STEM) operating mode. The deactivation of the switchable multipole element enables the CPB microscope column to deliver a collimated beam onto the sample, thereby achieving a transmission electron microscope (TEM) operating mode.

13. The method as described in claim 12, The aberration correction system includes a hexapole spherical aberration corrector, which comprises two active magnetic hexapole elements that generate negative spherical aberration correction. When the switchable multipolar element is activated, a focused circular probe beam is delivered to a selected point on the sample.

14. The method of claim 13, wherein the probe beam is focused onto a sub-angstrom diameter spot.

15. The method as described in claim 1, The CPB microscope mentioned above is a scanning transmission electron microscope. The first imaging mode is the sample imaging mode. The second imaging mode is an electron diffraction mode, and The switchable multipole element is repeatedly activated and deactivated during scanning of the electron beam across the surface of the sample.

16. A charged particle beam (CPB) microscope system, comprising: Charged particle beam source; CPB column, the CPB column being configured to transport a charged particle beam from the charged particle beam source to the sample; An optical assembly, the optical assembly including a transport optics device configured to transport charged particles transmitted through or scattered by the sample to a detector. and The CPB pillar or the switchable multipole element component of the optical assembly, wherein the switchable multipole element is configured to generate a quadrupole field when activated, and is configured such that: Activating the switchable multipole element enables the CPB microscope to generate a first set of one or more images or datasets, or enables the CPB microscope to generate a first set of one or more images or datasets, the first set of one or more images or datasets including sample-related information according to a first imaging or data acquisition mode; and Deactivate the switchable multipole element to enable the CPB microscope to generate a second set of one or more images or datasets, or enable the CPB microscope to generate a second set of one or more images or datasets, the second set of one or more images or datasets including information related to the sample according to the second imaging or data acquisition mode.

17. The charged particle beam (CPB) microscope system of claim 16, further comprising an image rendering apparatus configured to render a multiple exposure composite image, the multiple exposure composite image being one or more images from a first set of one or more images or a dataset superimposed on one or more images from a second set of one or more images or a dataset.

18. The CPB microscope of claim 16, wherein the switchable multipole element is a switchable electrostatic multipole element, and wherein the switching time of the switchable electrostatic multipole element is not greater than 100 milliseconds, or alternatively not greater than 10 milliseconds, or alternatively not greater than 1 millisecond, or alternatively not greater than 500 microseconds, or alternatively not greater than 10 microseconds, or alternatively not greater than 1 microsecond, or alternatively not greater than 500 nanoseconds, or alternatively not greater than 50 nanoseconds.

19. A transmission electron microscope (TEM) system, comprising: An image projection system, the image projection system comprising: An objective lens system configured to receive electron beams from a sample and having a back focal plane; A projection lens system, wherein the projection lens system is disposed between the objective lens system and the detector; and A first switchable multipole element, configured to generate a quadrupole field when activated and positioned at a selected aperture plane of the objective system, is configured to be alternately activated and deactivated. Activation of the first switchable multipole element causes the image of the sample to be projected onto the detector, and deactivation of the switchable multipole element causes the diffraction pattern of the sample to be projected onto the detector.

20. The TEM system of claim 19, wherein the switchable multipole element is a switchable electrostatic multipole element, and the switching time of the first switchable electrostatic multipole element is not greater than 100 milliseconds, or alternatively not greater than 10 milliseconds, or alternatively not greater than 1 millisecond, or alternatively not greater than 500 microseconds, or alternatively not greater than 10 microseconds, or alternatively not greater than 1 microsecond, or alternatively not greater than 500 nanoseconds, or alternatively not greater than 50 nanoseconds.

21. The TEM system of claim 19, wherein the image projection system further comprises: A second switchable multipole element, configured to generate a quadrupole field when activated and positioned at or near the intermediate image plane of the objective system, is configured to be alternately activated and deactivated. The simultaneous activation of the first switchable multipolar element and the second switchable multipolar element causes the focused image of the sample to be projected onto the detector, and the simultaneous deactivation of the first switchable multipolar element and the second switchable multipolar element causes the diffraction pattern of the sample to be projected onto the detector.

22. The TEM system of claim 21, wherein the second switchable multipole element is a switchable electrostatic multipole element, the switchable electrostatic multipole element having a switching time of no more than 100 milliseconds, or alternatively no more than 10 milliseconds, or alternatively no more than 1 millisecond, or alternatively no more than 500 microseconds, or alternatively no more than 10 microseconds, or alternatively no more than 1 microsecond, or alternatively no more than 500 nanoseconds, or alternatively no more than 50 nanoseconds.

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