Magnetic lens, charged particle microscope system including same, and related methods

Abstract

Magnetic lenses, charged particle microscope systems including magnetic lenses, and related methods are disclosed. In one example, a magnetic lens is configured to direct a charged particle beam to a sample location, and includes a plurality of pole pieces and at least two independent coils. The magnetic lens operates as an objective lens with a variable main objective lens plane without immersing the sample in the magnetic field. The variable main objective plane allows for selective adjustment of the magnification of the charged particle beam at the focal plane without immersing the sample position in the magnetic field generated by the coil of the magnetic lens. In one example, a charged particle microscope system includes a charged particle source, a sample holder, and a magnetic objective. In one example, a method includes positioning a sample relative to a magnetic lens, and operating the magnetic lens to focus a charged particle beam to a focus position.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. non-provisional application No. 18 / 342,643, filed on June 27, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure generally relates to magnetic lenses for charged particle microscopy systems and charged particle microscopy systems including such magnetic lenses. Background Art

[0004] Charged particle microscopy is a well-known and increasingly important technique for imaging microscopic objects, particularly in the form of electron microscopy. The basic class of electron microscopes finds practical use in the form of various device classes such as transmission electron microscopes (TEM), scanning electron microscopes (SEM) and scanning transmission electron microscopes (STEM), as well as various subclasses.

[0005] In a SEM, illumination of the sample by a scanning electron beam promotes the emission of "auxiliary" radiation from the sample, for example in the form of secondary electrons, backscattered electrons, X-rays, and cathodoluminescence (infrared, visible, and / or ultraviolet photons). One or more components of this emitted radiation are then detected and used for image accumulation purposes.

[0006] As an alternative to using electrons as the irradiation beam, charged particle microscopy can also be performed using other kinds of charged particles. In this regard, the phrase "charged particles" can be understood to cover, for example, electrons, positive ions (e.g., Ga or He ions), negative ions, protons and positrons. In addition to imaging and performing (local) surface modifications (e.g., milling, etching, deposition, etc.), charged particle microscopy can also have other functionalities, such as performing spectroscopy, examining diffraction patterns, etc.

[0007] In all cases, a charged particle microscope (CPM) will typically include at least a radiation source (eg, an electron source or an ion gun), a beam guidance system, a sample holder, and a detector.

[0008] Depending on the radiation being detected, the detector may take many different forms. Examples include photodiodes, CMOS detectors, CCD detectors, photovoltaic cells, X-ray detectors (such as silicon drift detectors and Si(Li) detectors), etc. In general, a CPM may include several different types of detectors, the selection of which may be called for in different situations. It is generally desirable that the detector exhibit a sufficiently wide dynamic range to represent a wide range of incident charged particle signal magnitudes.

[0009] While the present disclosure as a whole relates to the specific context of charged particle microscopy, and more specifically to electron microscopy, such description is not intended to be limiting, and the apparatus and methods disclosed herein may be applied in any suitable context within the scope of the present disclosure. Summary of the invention

[0010] Disclosed herein are a magnetic lens, a charged particle microscope system including the magnetic lens, and related methods.

[0011] In a representative example, an apparatus includes a magnetic lens configured to direct a charged particle beam to a sample position in a focal plane. The magnetic lens includes a plurality of pole pieces defining at least two axial gaps and at least two independent coils respectively connected to the at least two axial gaps, and the at least two independent coils are configured to generate a magnetic field so that the magnetic lens operates as a single objective lens with a variable main objective lens plane. The variable main objective lens plane allows the magnification of the charged particle beam at the focal plane to be selectively adjusted without immersing the sample position in the magnetic field generated by the coils of the magnetic lens.

[0012] In another representative example, the magnetic lens includes a lens body, a first coil supported by the lens body, and a second coil supported by the lens body. The first coil is configured to generate a first magnetic field, and the second coil is configured to generate a second magnetic field. The lens body includes a central hole configured to receive a charged particle beam passing through the magnetic lens, a first pole piece, a second pole piece, and a third pole piece. The first pole piece extends circumferentially around the central hole. The second pole piece extends circumferentially around the central hole and is at least partially disposed radially outside the first pole piece. The third pole piece extends circumferentially around the central hole and is at least partially disposed radially outside the second pole piece.

[0013] In another representative example, a charged particle microscope system includes: a charged particle source configured to emit a charged particle beam along an optical axis and toward a sample; a sample holder configured to support the sample; and a magnetic objective lens configured to focus the charged particle beam to a focus position corresponding to the position of the sample. The magnetic objective lens includes a lens body having a central hole through which the charged particle beam extends, a first coil and a second coil. The first coil is supported by the lens body and is configured to generate a first magnetic field having a first field size. The second coil is supported by the lens body and is configured to generate a second magnetic field having a second field size. The magnetic objective lens is configured so that the ratio between the first field size and the second field size is adjusted to adjust the magnification of the magnetic objective lens. The focus position is located outside the lens body, and each of the first magnetic field and the second magnetic field is confined to an area away from the focus position.

[0014] In another representative example, a method includes positioning a sample relative to a magnetic lens and operating the magnetic lens to focus a charged particle beam to a focus position. The magnetic lens includes a plurality of pole pieces defining at least two axial gaps and at least two independent coils respectively communicating with the at least two axial gaps, so that the magnetic lens operates as a single objective lens with a variable main objective plane.

[0015] The foregoing and other objects, features and advantages of the disclosed technology will become more apparent from the following detailed description made with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic representation of a CPM system that may utilize the magnetic lenses disclosed herein, according to an example.

[0017] Figure 2 is a schematic representation of a charged particle beam incident on a sample according to an example.

[0018] Figure 3 is a schematic representation of a magnetic lens according to an example.

[0019] Figure 4 is a schematic representation of the magnitudes of the first magnetic field, the second magnetic field and the total magnetic field generated by the magnetic lens according to the first example.

[0020] Figure 5 is a schematic representation of the magnitudes of the first magnetic field, the second magnetic field and the total magnetic field generated by the magnetic lens according to the second example.

[0021] Figure 6 is a schematic representation of the magnitudes of the first magnetic field, the second magnetic field, and the total magnetic field generated by the magnetic lens according to the third example.

[0022] Figure 7 is a schematic representation of the magnitudes of the first magnetic field, the second magnetic field, and the total magnetic field generated by the magnetic lens according to the fourth example.

[0023] Figure 8 is a flow chart depicting a method of making and / or using a magnetic lens according to an example. DETAILED DESCRIPTION

[0024] The present disclosure generally relates to magnetic lenses configured to be used in conjunction with a charged particle microscope (CPM) system to focus one or more charged particle beams on a sample. As discussed in more detail below, such magnetic lenses can enable selective adjustment of the main objective plane and / or magnification of the charged particle beam without immersing the sample in a magnetic field. Examples can allow a fixed working distance or focal plane position while providing adjustable magnification and focusing angle.

[0025] Figure 1 1 is a schematic representation of an example of a charged particle microscope (CPM) system 100. The CPM system 100 may include a charged particle source 120, a sample holder 150 configured to support a sample 152, and a beam guidance system 130. The charged particle source 120 may generate and / or emit a charged particle beam 122 along an optical axis 112 toward the sample 152, while the beam guidance system 130 may shape, modulate, focus, and / or guide the charged particle beam 122 to the sample 152.

[0026] The beam guidance system 130 may include any of a variety of components and / or elements for manipulating the charged particle beam 122. For example, and as Figure 1 As shown, the beam guidance system 130 may include an aperture 132 configured to limit the angular range of the charged particle beam 122, a focusing lens 134 configured to focus the charged particle beam 122 toward the sample 154, and / or one or more scanning coils 136 configured to deflect the charged particle beam 122. As discussed in more detail below, the beam guidance system 130 also includes a magnetic objective lens 138 that operates to guide (e.g., focus and / or focus) the charged particle beam 122 to a focus position 124 on the sample 152. Figure 1 As shown, magnetic objective 138 includes a central hole 106 through which charged particle beam 122 can travel. In various examples, beam guidance system 130 can additionally or alternatively include an illuminator, an objective, a projection lens, a condenser lens, an electrostatic / magnetic lens, a deflector (e.g., a scanning coil), a corrector (such as an astigmatism correction device), etc. in any suitable combination.

[0027] The focusing position 124 may include, may be, and / or correspond to any position (e.g., a point, area, line, plane, volume, etc.) at which the charged particle beam is sufficiently focused to serve as a probe of the sample 152 as described herein. For example, the focusing position 124 may include and / or may be a focal point and / or focal plane associated with the magnetic objective lens 138. Therefore, as used herein, the focusing position 124 may additionally or alternatively be referred to as a focal point 124 and / or a focal plane 124. In examples where the focal position 124 is at least a portion of a focal plane, it should be understood that such a focal plane is not necessarily perfectly planar. For example, the focal plane may be affected by the field curvature associated with the magnetic objective lens 138.

[0028] As discussed in more detail below, magnetic objective 138 is operable to focus charged particle beam 122 by generating one or more magnetic fields that deflect rays of charged particle beam 122 toward a common focal location (e.g., focal location 124). Figure 1As shown, the magnetic objective lens 138 includes a first coil 140 configured to generate a first magnetic field and a second coil 142 configured to generate a second magnetic field. For example, each of the first coil 140 and / or the second coil 142 may include and / or may be a coil of conductive material (e.g., a wire) configured so that passing an electric current through each coil operates to generate a corresponding magnetic field.

[0029] The magnetic objective 138 is typically configured such that the sample 152 is substantially shielded and / or isolated from each of the first magnetic field and the second magnetic field during operational use of the CPM system 100. Figure 1 As shown, the CPM system 100 is configured such that the sample holder 150 and the sample 152 are positioned completely outside of the magnetic objective 138 during operational use of the CPM system 100. Additionally, and as described in more detail below, the magnetic objective 138 has a plurality of pole pieces that are configured to direct and / or position the first magnetic field and the second magnetic field toward the central aperture 106 and / or away from the sample 152.

[0030] The CPM system 100 may represent an example of any of a variety of CPM systems. In particular, the present disclosure generally relates to examples in which the CPM system 100 includes and / or is a scanning electron microscope (SEM) system, in which the charged particle beam 122 is an electron beam 122 guided by a beam guidance system 130 and focused onto a sample 152. In such examples, the (focused) electron beam 122 may interact with the sample 152 in such a manner that various types of stimulated radiation are emitted from the sample 152, including (for example) secondary electrons, backscattered electrons, X-rays, and / or optical radiation (cathodoluminescence).

[0031] Although the present disclosure generally relates to examples in which the CPM system 100 is a SEM system, this is not required in all examples, and additionally, within the scope of the present disclosure, the systems and devices disclosed herein (e.g., the magnetic objective 138) may be used in conjunction with any suitable CPM configuration, examples of which include a transmission electron microscope (TEM), a scanning transmission electron microscope (STEM), a focused ion beam (FIB) system, and the like.

[0032] like Figure 1 As shown, the CPM system 100 may include an electron detector 160 configured to detect electrons emitted from the sample 152. In particular, Figure 1The electron detector 160 shown in the figure can represent a detector for detecting secondary electrons (SE) emitted from the sample 152. It is also within the scope of the present disclosure that the CPM system may additionally or alternatively include an electron detector configured to detect other emissions from the sample 152, such as backscattered electrons (BSE). In this way, measurements characterizing the electrons incident on the electron detector (e.g., characterizing the intensity and / or energy of such detected electrons) can provide an indication of various physical properties of the sample 152, such as the geometry of the sample 152 and / or the chemical composition of the sample 152 at the location where the electron beam 122 is incident on the sample 152 (e.g., at the focal position 124). Therefore, the spatial resolution of the CPM system 100 can characterize the sample 152 based at least in part on the minimum dimension (e.g., minimum diameter) of the electron beam 122 in a plane corresponding to the location where the sample 152 is located.

[0033] Thus, scanning the electron beam 122 across the surface of the sample 152 can produce an image and / or other representation of the sample 152 in the scanned area. Such scanning can be accomplished in any suitable manner. For example, the scanning coils 136 can be operated to deflect the electron beam 122 to move the focus position 124 relative to the sample 152. Additionally or alternatively, the sample holder 150 can be configured to rotate and / or translate the sample 152 by one or more dimensions to move the sample 152 relative to the focus position 124. Such translation of the sample 152 and / or scanning of the electron beam 122 can therefore allow a selected portion of the sample 152 to be irradiated / imaged / inspected by the electron beam 122 traveling along the optical axis 112.

[0034] like Figure 1 As shown, the CPM system 100 may also include a controller 180 that is programmed and / or otherwise configured to at least partially control the operation of the CPM system 100. For example, the controller 180 may at least partially control the operation of the charged particle source 120 to generate the charged particle beam 122 and / or may at least partially control the operation of at least a portion of the beam guidance system 130. Additionally or alternatively, the controller 180 may receive a signal from the electron detector 160 that is representative of electrons emitted from the surface of the sample 152, which may be used to generate an image and / or other representation of the sample 152.

[0035] In some examples, the controller 180 may also at least partially control the operation of the magnetic objective lens 138, such as by selectively and dynamically changing the first magnetic field and / or the second magnetic field. This may be accomplished by adjusting one or more currents delivered to the magnetic objective lens 138 to generate the magnetic field. For example, and as Figure 1As shown, the controller 180 may include a first current source 182 configured to deliver a first current 184 to the first coil 140 and a second current source 186 configured to deliver a second current 188 to the second coil 142. In such an example, the controller 180 may be configured to selectively change the first current 184 and / or the second current 188 to adjust the focal plane of the magnetic objective lens 138.

[0036] In various examples, the first coil 140 and the second coil 142 are configured to operate independently of each other to generate corresponding magnetic fields. For example, the first current 184 can be supplied to the first coil 140 alone and the second current 188 can be supplied to the second coil 142 alone, wherein the first current 184 and the second current 188 are independently and / or separately controlled. In this way, in the present invention, the first coil 140 and the second coil 142 can be described as independent coils and / or as separated coils.

[0037] like Figure 1 As shown, the controller 180 may include a user interface 190 for receiving input from a human user and / or for recording and / or displaying information. In particular, the user interface 190 may include one or more input devices 192 and / or one or more output devices 194. The one or more input devices 192 may include and / or may be any suitable device for receiving input from a human user to at least partially direct the operation of the CPM system 100, such as a keyboard, a mouse, a display, a touch screen, etc. The one or more output devices 194 may include and / or may be any suitable device for transmitting information to a human user, such as a display, a touch screen, a physical storage drive, etc.

[0038] The controller 180 may include any of a variety of modules (e.g., hardware and / or software) for performing these and other functions. In some examples, the controller 180 is a single device that includes each of the component parts described herein. In other examples, the controller 80 may refer to and / or encompass a collection of components that may be at least partially spatially separated. The controller 180 may be connected to any other suitable component of the CPM system 100 in any suitable manner, such as via one or more control lines and / or via a wireless connection. As an example, such control lines may include and / or may be physical signal conduits, such as wires, electrical buses, optical fibers, etc.

[0039] Figure 2 An example of a charged particle beam 226 focused to a focus location 248 on a surface of a sample 252 is illustrated. The charged particle beam 226 may represent Figure 1 An example of a charged particle beam 122 and a sample 252 may represent Figure 1 Example of sample 152. Figure 2 As shown, the charged particle beam 226 can be focused onto the sample 252 by the objective lens 138, and the objective lens 240 can represent Figure 1 A portion of the beam guidance system 130 (e.g., magnetic objective lens 138). Figure 2 In the example of FIG. 2 , sample 252 is spaced apart from objective lens 240 by a working distance 270 .

[0040] like Figure 2 As shown in FIG. 2 , charged particle beam 226 is emitted by charged particle beam source 220 and is limited by aperture 232. Charged particle beam source 220 and aperture 232 may represent Figure 1 1 and 132. The charged particle beam 226 may be characterized by a first beam diameter 224 upstream of and / or at the objective lens 240. The charged particle beam 226 may additionally be characterized by a focused beam diameter 246 at a focusing position 248.

[0041] Other optical elements before the charged particle beam source 220 and the objective lens 240 ( Figure 2 2 (not shown), objective lens 240 can be operated to define the optical magnification of the optical lens barrel, that is, the magnification of charged particle beam 226 from charged particle beam source diameter 222 at charged particle beam source 220 to focused beam diameter 246 at focusing position 248. For example, the ratio of focused beam diameter 246 to charged particle beam source diameter 222 can correspond to the magnification.

[0042] The charged particle beam 226 may also be characterized by a beam spot angle 244 (or "aperture angle"), which may be measured between the optical axis 212 and the outer extent of the beam envelope, and / or by a focal length 260 representing the distance between a primary objective plane 242 of the objective 240 and a focus position 248 along the optical axis 212. Specifically, as used herein, the primary objective plane 242 of the objective 240 refers to a plane spatially associated with the objective 240 (e.g., at least partially within the objective 240) from which the focal length 260 is measured. In general, the optical magnification of the optical lens barrel determines the spot angle 244, which may also be associated with the focal length 260. In this manner, adjusting the objective 240 to change the position of the primary objective plane 242 also operates to adjust the focal length 260, the spot angle 244, and the optical magnification of the optical lens barrel. Such adjustments may also be made while maintaining a fixed working distance 270 between the structure of objective 240 and sample 252 .

[0043] As described above, it is generally desirable that the focused beam diameter 246 be as small as possible to maximize the spatial resolution of the associated CPM system. However, in practice, optical phenomena such as spherical aberration, chromatic aberration, astigmatism, diffraction, etc. contribute to an undesirable increase in the ideally obtainable beam width of the charged particle beam 226 downstream of the objective lens 240 (including at the focal position 248). Therefore, the focal position 248 may refer to and / or correspond to a position (e.g., a plane perpendicular to the optical axis 212) where the spatial density of the light rays of the charged particle beam 226 reaches a maximum value and / or where the charged particle beam 226 has a minimum diameter (e.g., a focused beam diameter 246) and / or represents a position where the spatial density of the light rays of the charged particle beam 226 reaches a maximum value. The sum of various contributions to the undesirable increase in beam width at the focus may be minimized by selecting an optimized value of the focus angle 244. Therefore, because the optical tube magnification determines the focus angle 244, a selective change in the optical tube magnification may allow the focus angle 244 that provides the minimum focused beam diameter 246 to be selected.

[0044] In practice, objective lens 240 is operable to adjust focal length 260, which in turn can adjust optical barrel magnification and focused beam diameter 246. In this way, adjusting focal length 260 is operable to adjust the defined magnification of the optical barrel between the charged particle beam source and sample 252. In some examples, focused beam diameter 246 can be dependent on focal length 260, such that focused beam diameter 246 reaches a minimum value at a particular corresponding focal length 260, which in some examples can be referred to as an optimized value of focal length 260.

[0045] In some examples, the SEM system can be configured to focus each of the multiple charged particle beams onto the sample. For example, and with reference to Figure 1 , the charged particle beam 122 may be a first charged particle beam 122, the focal position 124 may be a first focal position 124, and the beam guidance system 130 may also be configured to guide the second charged particle beam 126 to a second focal position 128 on the sample 152 adjacent to the first focal position 124. In some examples, the first focal position 124 and the second focal position 128 are located in a common focal plane extending perpendicular to the optical axis 112. In such examples, a distance separating the first focal position 124 and the second focal position 128 (e.g., along a direction perpendicular to the optical axis 112 and / or parallel to the surface of the sample 152) may be described as a beam spacing of the CPM system 100. In such examples, the CPM system 100 may also be referred to as a multi-beam CPM system 100 and / or a multi-beam SEM system 100.

[0046] In some conventional examples of CPM systems, adjusting the magnification of the beam guidance system may be important because it may also operate to adjust the beam spacing of a multi-probe pattern of a charged particle beam (or "beamlet") incident on a sample. Thus, in some examples, one or more condenser lenses (e.g., Figure 1 The condenser lens 134) can be used to adjust the aperture angle and / or the total magnification of the charged particle beam. However, in some examples, such as in a multi-beam SEM system, the trajectory of the charged particle beam can be constrained to mitigate and / or minimize the effects of the aberrations of the condenser lens. In such examples, it may be impractical to adjust the aperture angle and / or the total magnification of the charged particle beam using a condenser lens in this manner.

[0047] As another example, in some conventional examples of CPM systems, the focal length of the objective lens may also be adjusted, but such focal length may be measured relative to a generally fixed position of the primary objective plane of the objective lens. When the focal length changes, this results in a change in the position of the focal plane along the optical axis 212 (e.g., relative to the objective lens). In some such examples, a platform (e.g., Figure 1 The sample holder 150 of the embodiment of the present invention can be used to adjust the working distance by moving the sample to the newly positioned focal plane. However, such adjustment may undesirably affect the quality of the signal. For example, moving the sample to a larger working distance may result in only a few signal electrons being detectable by the in-barrel detector. Alternatively, moving the sample to a smaller working distance may block the in-barrel detector. In addition, in some examples, transmission detection of a multi-beam SEM requires a fixed working distance.

[0048] In order to allow for a change in focal length at a constant working distance, the objective of the CPM system may include and / or may be a composite magnetic lens having a high-resolution lens and an immersion objective that can be adjusted independently of each other to move the focal plane of the charged particle beam. In particular, in such examples, changing the ratio between the respective magnitudes of the magnetic fields generated by the high-resolution lens and the immersion objective can move the position of the main objective plane of the objective, and thus the magnification of the beam guidance system can be adjusted. Such examples typically require that the sample be exposed to (e.g., immersed in) the magnetic field generated by the immersion objective, which may be undesirable. For example, using an immersion magnetic field in this manner may not be suitable for magnetically sensitive samples, and such a configuration may limit the range of working distances that can be used. Additionally, in some examples, the respective magnetic fields generated by the high-resolution lens and the immersion objective may overlap only in a complex manner that introduces undesirable aberrations, thereby limiting the resolution of the CPM system.

[0049] In contrast, the magnetic objective lens of the present disclosure may enable adjustment of the main objective lens plane in a manner similar to a conventional compound magnetic lens without exposing the sample to a significant magnetic field generated by the lens. In this manner, the magnetic objective lens of the present disclosure may be particularly suitable for use with magnetically sensitive samples and / or in CPM systems such as multi-beam SEM systems with significant geometric and / or optical constraints.

[0050] In the present disclosure, an object and / or location (e.g., a sample and / or location thereof) may be described as being "immersed" in a magnetic field when the magnetic field extends to, through, and / or around the object and / or location, such as having a magnetic field amplitude of at least 75% of the maximum amplitude of the magnetic field, at least 50% of the maximum amplitude of the magnetic field, at least 30% of the maximum amplitude of the magnetic field, at least 20% of the maximum amplitude of the magnetic field, at least 10% of the maximum amplitude of the magnetic field, at least 5% of the maximum amplitude of the magnetic field, at least 2% of the maximum amplitude of the magnetic field, at least 1% of the maximum amplitude of the magnetic field, at least 0.5% of the maximum amplitude of the magnetic field, at least 0.1% of the maximum amplitude of the magnetic field, and / or at least 0.01% of the maximum amplitude of the magnetic field. For example, a conventional immersion objective may generate a magnetic field at the sample location that is approximately 30%-100% of the maximum amplitude of the magnetic field.

[0051] Similarly, in the present disclosure, an object and / or location may be described as being at least substantially isolated from, at least substantially shielded from, and / or not immersed in a magnetic field when the magnetic field extends to, through, and / or around the object and / or location only at a magnetic field amplitude of less than 50% of the maximum amplitude of the magnetic field, less than 40% of the maximum amplitude of the magnetic field, less than 30% of the maximum amplitude of the magnetic field, less than 20% of the maximum amplitude of the magnetic field, less than 10% of the maximum amplitude of the magnetic field, less than 5% of the maximum amplitude of the magnetic field, less than 2% of the maximum amplitude of the magnetic field, less than 1% of the maximum amplitude of the magnetic field, less than 0.5% of the maximum amplitude of the magnetic field, less than 0.1% of the maximum amplitude of the magnetic field, and / or less than 0.01% of the maximum amplitude of the magnetic field. For example, a magnetic lens according to the present disclosure may be configured to generate a magnetic field at a sample location at approximately 0.07%-5% of the maximum amplitude of the magnetic field when the sample location is positioned at a working distance of approximately 6 millimeters (mm). When the working distance is shortened, the magnetic field at the sample location may be approximately 0.6%-40% of the maximum field amplitude. When the working distance is extended to about 10 mm, the magnetic field at the sample location can be about 0.02%-3% of the maximum field amplitude. In all such examples, the sample positioned at the sample location can be described as being at least substantially isolated from the magnetic field, at least substantially shielded from the magnetic field, and / or not immersed in the magnetic field.

[0052] In some examples, the maximum amplitude of the magnetic field may correspond to the maximum amplitude of the field in free space (e.g., outside of the magnet component, coil, pole piece, etc., associated with the magnet). Additionally or alternatively, in some examples, the maximum amplitude of the magnetic field may correspond to the maximum amplitude of the field in an interior region of the component that generates the magnetic field, such as within the central aperture 106 of the magnetic objective lens 138 discussed above.

[0053] Figure 3 An example of a magnetic lens 300 is shown, which may be Figure 1 The magnetic objective lens 138 and / or Figure 2 An example of an objective lens 240. Figure 3 As shown, the magnetic lens 300 includes a lens body 330 that defines a central hole 304 of the magnetic lens 300. The central hole 304 can be described as defining and / or extending along a central axis 302 of the magnetic lens 300. For example, the lens body 330 can be at least substantially axially symmetric about the central axis 302 and can define the central hole 304 so that a charged particle beam (e.g., Figure 1 The charged particle beam 122) can travel through the central aperture 304. In particular, in some examples, the charged particle beam can be directed along an optical axis that is parallel and / or co-linear with the central axis 302 (e.g., Figure 1 The optical axis 112 and / or Figure 2 The optical axis 212 of the lens travels through the lens body 330. In some examples, the charged particle beam can include multiple beamlets.

[0054] Reference Figure 3 , the magnetic lens 300 is generally configured to focus the charged particle beam onto a sample 382, ​​which may be supported by a sample holder 380 of the CPM system. The sample 382 may represent Figure 1 Sample 152 and / or Figure 2 Similarly, the sample holder 380 may represent Figure 1 382 and / or a sample position 384 at which the sample 382 is located. In particular, the magnetic lens 300 is configured to generate one or more magnetic fields that deflect the charged particles of the charged particle beam to direct and / or focus the charged particle beam to a local area of ​​the sample 382 and / or a sample position 384 at which the sample 382 is located. In an example where the charged particle beam includes a plurality of beamlets, the magnetic lens 300 can be configured to direct the beamlets to corresponding spaced-apart focus positions on the sample 382 and / or at the sample position 384.

[0055] In some examples, sample position 384 may correspond to the focal position of a charged particle beam (eg, Figure 1 The focus position 124 and / or Figure 2 In this manner, as used herein, sample position 384 can represent a location (e.g., a point and / or a plane) at which sample 382 and / or a portion thereof (e.g., an exposed surface of sample 382) can be positioned during operational use of magnetic lens 300, regardless of whether sample 382 is positioned at sample position 384.

[0056] like Figure 3As shown, the magnetic lens 300 is configured such that the sampling position 384 and / or the focal position of the magnetic lens 300 is completely outside the lens body 330. Therefore, the magnetic lens 300 is configured such that the sample 382 can be completely positioned outside the magnetic lens 300 during operational use of the magnetic lens 300.

[0057] In the present disclosure, the sample position 384 and / or the focal position of the charged particle beam may be represented and / or quantified in any suitable manner. Figure 3 As shown, the configuration of the magnetic lens 300 and / or a CPM system including the magnetic lens 300 can be characterized with reference to a working distance 370 separating the lens body 330 and the sample location 384 .

[0058] like Figure 3 As shown, the working distance 370 may represent the minimum distance between a portion of the lens body 330 and the sample position 384 measured along a direction parallel to the central axis 302. More specifically, the working distance 370 may be defined as the minimum distance between a first plane and a second plane, the first plane being perpendicular to the central axis 302 tangential to the lens body 330, and the second plane being perpendicular to the central axis 302 tangential to (or including) the sample position 384. In this way, the working distance 370 of the magnetic lens 300 may be defined even when the sample 382 is not present.

[0059] The working distance 370 may take any of a variety of values, such as may be associated with the overall size of the associated CPM system and / or with the magnification of the magnetic lens 300. As an example, the working distance 370 may be at least 1 millimeter (mm), at least 5 mm, at least 10 mm, at least 15 mm, at least 20 mm, at most 25 mm, at most 17 mm, at most 12 mm, at most 7 mm, and / or at most 2 mm. The working distance 370 may additionally or alternatively be adjustable by any suitable range of values, such as a range of values ​​encompassing and / or including one or more of the foregoing values.

[0060] Additionally or alternatively, the configuration of the magnetic lens 300 and / or a CPM system including the magnetic lens 300 can be characterized with reference to the focal length of the magnetic lens 300. In particular, and as Figure 3 As shown in , the magnetic lens 300 can define a main objective plane 390 and can therefore be characterized by a focal length 392 separating the main objective plane 390 and the sample position 384 , as measured along a direction parallel to the central axis 302 .

[0061] The focal length 392 may also take any of a variety of values, such as may be determined at least in part by the desired magnification of the magnetic lens 300. As an example, the focal length 392 may be at least 1 mm, at least 5 mm, at least 10 mm, at least 15 mm, at least 20 mm, at most 25 mm, at most 17 mm, at most 12 mm, at most 7 mm, and / or at most 2 mm. The focal length 392 may additionally or alternatively be adjustable by any suitable range of values, such as a range of values ​​covering and / or including one or more of the foregoing values.

[0062] like Figure 3 As shown, the magnetic lens 300 includes a first coil 310 and a second coil 320, each of which is supported by a lens body 330. The first coil 310 is configured to generate a first magnetic field and the second coil 320 is configured to generate a second magnetic field, each of which can act on (e.g., exert a Lorentz force on) particles of a charged particle beam traveling through the magnetic lens 300 to focus the charged particle beam on a sample 382. Figure 3 The first coil 310 and the second coil 320 may respectively represent Figure 1 An example of a first coil 140 and a second coil 142 .

[0063] In various examples, the magnetic lens 300 is configured so that when the magnetic lens 300 generates each of the first magnetic field and the second magnetic field, the first magnetic field and the second magnetic field overlap (e.g., spatially) to form a total magnetic field that is the sum of the first magnetic field and the second magnetic field. In particular, the first magnetic field can be characterized by the first field magnitude at each point in the space around the first coil 310, and the second magnetic field can be characterized by the second field magnitude at each point in the space around the second coil 320. Therefore, the total magnetic field can be characterized by the total field magnitude at each point in the space around the first coil 310 and the second coil 320, which is the sum of the first field magnitude and the second field magnitude at the point. The first magnetic field and the second magnetic field can at least partially overlap within the central hole 304 of the magnetic lens 300, so that the charged particle beam passing through the central hole 304 is focused by the total magnetic field.

[0064] In various examples, the characteristics and / or operation of the magnetic lens 300 can be described based on a single first magnetic field, a single second magnetic field, a first magnetic field and a second magnetic field, and / or a total magnetic field. Unless otherwise specified, descriptions with reference to the first magnetic field, the second magnetic field, and / or the total magnetic field generally relate to examples in which the reference magnetic field has a non-zero magnitude.

[0065] Similar to a conventional magnetic lens, magnetic lens 300 may be configured to selectively adjust focal length 392 and / or the position of a focal point of a charged particle beam via adjusting a ratio of a first field magnitude of a first magnetic field to a second field magnitude of a second magnetic field.

[0066] As described in more detail below, the lens body 330 is generally configured to position the total magnetic field away from the sample location 384. In particular, the lens body 330 can be configured so that when the magnetic lens 300 operates to generate the total magnetic field, the charged particle beam passing through the lens body 330 is subjected to each of the first magnetic field and the second magnetic field, and each of the first magnetic field and the second magnetic field is limited and / or positioned to a region away from the sample location 384. In this way, the magnetic lens 300 can be configured to adjust the position of the main objective plane 390 by adjusting the ratio of the first field size to the second field size. Therefore, this can make it possible to adjust the magnification of the optical system including the magnetic lens 300, while allowing the working distance 370 to remain unchanged (or change a small amount) and at the same time shielding and / or isolating the sample 382 from the total magnetic field. In other words, the magnetic lens 300 can be configured so that the sample 382 is at least substantially isolated from each of the first magnetic field and the second magnetic field during operational use, while maintaining the ability to selectively adjust the aperture angle and the optical tube magnification without using an immersion lens. Thus, magnetic lens 300 may be used in conjunction with magnetically sensitive samples and / or samples that are not otherwise suitable for use with an immersion magnetic lens.

[0067] The magnetic lens 300 can be configured to localize the total magnetic field to any suitable extent to produce a relatively small and / or negligible magnetic field at the sample location 384. In some examples, the localization of the total magnetic field can be characterized and / or quantified via a comparison of the respective magnitudes of the magnetic field within the central aperture 304 and at the sample location 384. For example, the total magnetic field can be characterized by a maximum focus field magnitude representing the maximum magnitude of the total magnetic field at any point within the central aperture 304, and the magnitude of the total magnetic field as measured at the sample location 384 can be at most 5% of the maximum focus field magnitude, at most 2% of the maximum focus field magnitude, at most 1% of the maximum focus field magnitude, at most 0.5% of the maximum focus field magnitude, and / or at most 0.1% of the maximum focus field magnitude.

[0068] The lens body 330 can have any suitable structure and / or configuration for positioning the total magnetic field as described herein. Figure 3 As shown, the lens body 330 may include a first pole piece 332, a second pole piece 336, and a third pole piece 344, each of which extends circumferentially at least partially around the central hole 304. The second pole piece 336 may be at least partially disposed radially outside the first pole piece 332, and the third pole piece 344 may be at least partially disposed radially outside the second pole piece 336.

[0069] exist Figure 3In the example of , the first coil 310 is disposed between the first pole piece 332 and the second pole piece 336, while the second coil 320 is disposed between the second pole piece 336 and the third pole piece 344. Therefore, in this example, the second pole piece 336 is positioned between the first pole piece 332 and the third pole piece 344 (e.g., radially between the first pole piece and the third pole piece). Therefore, in the present disclosure, the first pole piece 332 may also be referred to as the inner pole piece 332, the second pole piece 336 may also be referred to as the middle pole piece 336, and / or the third pole piece 344 may also be referred to as the outer pole piece 344.

[0070] The first pole piece 332, the second pole piece 336 and / or the third pole piece 344 can be configured to shape and / or guide the first magnetic field and / or the second magnetic field in any suitable manner. In particular, the first pole piece 332 and the second pole piece 336 can be configured to guide the first magnetic field toward the central hole 304, and the second pole piece 336 and the third pole piece 344 can be configured to guide the second magnetic field toward the central hole 304.

[0071] In various examples, each of the first pole piece 332, the second pole piece 336, and / or the third pole piece 344 may be formed of a magnetic material (e.g., a ferromagnetic material such as iron) that operates to concentrate and / or direct each of the first magnetic field and / or the second magnetic field. For example, relative to the spatial distribution of the first magnetic field and / or the second magnetic field in the absence of such pole pieces, the first pole piece 332, the second pole piece 336, and / or the third pole piece 344 may operate to concentrate the magnetic field lines associated with the first magnetic field and / or the second magnetic field therein, thereby reducing the spatial extent of such magnetic fields outside the lens body 330.

[0072] As described above, the magnetic lens 300 can be configured so that the first magnetic field and the second magnetic field overlap at least partially in space. In particular, the magnetic lens 300 can be configured so that the first pole piece 332, the second pole piece 336, and the third pole piece 344 together form a portion of a common magnetic circuit associated with each of the first magnetic field and the second magnetic field. In other words, when the first magnetic field and the second magnetic field are each non-zero, the total magnetic field can be characterized by magnetic field lines extending through each of the first pole piece 332, the second pole piece 336, and the third pole piece 344.

[0073] The common magnetic path (e.g., represented by magnetic field lines of the total magnetic field) may also extend between the pole pieces and / or into the central hole 304. For example, and as Figure 3 As shown, the first pole piece 332 and the second pole piece 336 may define a first field region 360 therebetween, which may represent a region in which the first magnetic field is primarily located. Similarly, the second pole piece 336 and the third pole piece 344 may define a second field region 362 therebetween, which may represent a region in which the second magnetic field is primarily located.

[0074] In such examples, the common magnetic path extending through first pole piece 332, second pole piece 336, and third pole piece 344 may further extend through each of first field region 360 and second field region 362. Additionally or alternatively, first pole piece 332 and second pole piece 336 may be configured to direct the first magnetic field through first field region 360 to central hole 304, and / or second pole piece 336 and third pole piece 344 may be configured to direct the second magnetic field through second field region 362 to central hole 304.

[0075] As described above, the total magnetic field generated by magnetic lens 300 represents the sum of the first magnetic field generated by first coil 310 and the second magnetic field generated by second coil 320, each of which is in turn shaped at least in part by first pole piece 332, second pole piece 336, and / or third pole piece 344. Therefore, when magnetic lens 300 operates to generate each of the first magnetic field and the second magnetic field, the magnetic field at any given location within or around magnetic lens 300 generally does not represent the first magnetic field alone or the second magnetic field alone, but rather represents the sum of these magnetic fields.

[0076] Therefore, in the present disclosure, although the description of a component or region that shapes or contains a first (or second) magnetic field may be understood as primarily pertaining to the first (or second) magnetic field, it should be recognized that such a description may also relate to the second (or first) magnetic field at such a location. In other words, although the present disclosure includes descriptions that refer to components or regions only with reference to the first magnetic field or the second magnetic field, it should be understood that such a description more generally relates to the corresponding component of the total magnetic field and / or the total magnetic field itself.

[0077] The first field 360 and / or the second field 362 may have any of a variety of forms, shapes, and / or configurations. Figure 3 As shown, the first field 360 and / or the second field 362 may be open to the central hole 304 and / or extend coextensively with the central hole 310. Additionally or alternatively, the second field 362 may be separated from the first field 360, for example, such that the first field 360 and the second field 362 are connected to each other only via the central hole 304. Figure 3 In the example, the first field region 360 extends between and / or is defined by the first coil 310 and the central hole 304, and the second field region 362 extends between and / or is defined by the second coil 320 and the central hole 304.

[0078] Figure 3An example is shown in which each of first coil 310, second coil 320, first pole piece 332, second pole piece 336, and third pole piece 344 extends completely circumferentially around central axis 302. However, this is not required in all examples, and additionally within the scope of the present invention, first pole piece 332, second pole piece 336, and / or third pole piece 344 may extend only partially around central axis 302.

[0079] exist Figure 3 In the example of , each of the first pole piece 332, the second pole piece 336, and the third pole piece 344 at least partially defines the central hole 304. In particular, in this example, the first pole piece 332 terminates at the first terminal edge region 334, the second pole piece 336 terminates at the second terminal edge region 338, and the third pole piece 344 terminates at the third terminal edge region 346.

[0080] In this example, each of first terminal edge region 334, second terminal edge region 338, and third terminal edge region 346 includes and / or is a generally annular surface that partially defines central hole 304. In such examples, each of first terminal edge region 334, second terminal edge region 338, and third terminal edge region 346 may additionally or alternatively be described as including, being, and / or defining a central aperture of a respective pole piece.

[0081] like Figure 3 As shown, central hole 304 is characterized by a hole diameter 306 measured in a direction perpendicular to central axis 302. In some examples, hole diameter 306 may correspond to a diameter (e.g., a minimum diameter) of first terminal edge region 334, second terminal edge region 338, and / or third terminal edge region 346.

[0082] exist Figure 3 In the example of FIG. 3 , the respective diameters of first terminal edge region 334, second terminal edge region 338, and third terminal edge region 346 are substantially equal to one another, and hole diameter 306 is shown relative to first terminal edge region 334. However, this is not required in all examples, and additionally it is within the scope of the present disclosure that two or more of first terminal edge region 334, second terminal edge region 338, and third terminal edge region 346 have different respective diameters. In such examples, hole diameter 306 may correspond to the smallest diameter among the respective diameters of first terminal edge region 334, second terminal edge region 338, and third terminal edge region 346. In some examples, the respective diameters of first terminal edge region 334, second terminal edge region 338, and third terminal edge region 346 differ from one another by at most 20%.

[0083] The hole diameter 306 may take any suitable value, such as a value that is large enough to allow the charged particle beam to pass through the central hole 304 and / or small enough to not significantly attenuate the total magnetic field along the central axis 302. For example, the hole diameter 306 may be at least 0.1 mm, at least 0.5 mm, at least 1 mm, at least 5 mm, at most 10 mm, at most 2 mm, at most 0.7 mm, and / or at most 0.2 mm.

[0084] Lens body 330 may also be characterized with reference to the axial offset of first pole piece 332, second pole piece 336, and / or third pole piece 344 relative to one another along the direction of central axis 302. For example, and as Figure 3 As shown, the first terminal edge region 334 and the second terminal edge region 338 may be separated by a first pole piece gap 350 , while the second terminal edge region 338 and the third terminal edge region 346 may be separated by a second pole piece gap 354 .

[0085] The first pole piece gap 350 may be described as being in communication with the first coil 310, such as via the first field region 360. In other words, the first field region 360 may extend continuously between the first coil 310 and the first pole piece gap 350. Similarly, the second pole piece gap may be described as being in communication with the second coil 320, such as via the second field region 362. In other words, the second field region 362 may extend continuously between the second coil 320 and the second pole piece gap 354.

[0086] like Figure 3 As shown, the first pole piece gap 350 has a first gap width 352 and the second pole piece gap has a second gap width 356. In this example, each of the first gap width 352 and the second gap width 356 is measured along a direction parallel to the central axis 302.

[0087] The first pole piece gap 350 and the second pole piece gap 354 can have any suitable configuration and / or relative size. As an example, the ratio of the first gap width 352 to the second gap width 356 can be at least 1:10, at least 1:5, at least 1:2, at least 1:1, at least 2:1, at least 5:1, at most 10:1, at most 5:1, at most 2:1, at most 1:1, at most 1:2, at most 1:5, and / or at most 1:10.

[0088] Additionally or alternatively, and as Figure 3As shown, each of the first pole piece gap 350 and the second pole piece gap 354 can face the central axis 302. In such examples, each of the first pole piece gap 350 and the second pole piece gap 354 can be described as an axial gap. In other words, in such examples, the first terminal edge region 334 and the second terminal edge region 338 can be spaced apart from each other primarily along a direction parallel to the central axis 302, and the second terminal edge region 338 and the third terminal edge region 346 can similarly be spaced apart from each other primarily along a direction parallel to the central axis 302. Such a configuration can therefore be described in contrast to an alternative example in which the second terminal edge region and the third terminal edge region are approximately equidistant from the plane of the sample position measured along the central axis, in which case the gap between the terminal edge regions of the second pole piece and the third pole piece can be described as facing the sample. However, it should be understood that such alternative configurations are also within the scope of the present disclosure. In particular, while such a configuration is operable to direct an immersion magnetic field toward and / or to a sample, such a configuration may produce improved characteristics (eg, stronger lensing with less coil current) relative to a conventional immersion lens lacking a third pole piece.

[0089] like Figure 3 As shown, during operational use of magnetic lens 300, third pole piece 344 may be positioned between sample 382 and each of first pole piece 332 and second pole piece 336. In other words, lens body 330 may be configured such that third pole piece 344 is proximate to sample 382 and / or sample position 384 relative to each of first pole piece 332 and second pole piece 336. In this manner, third pole piece 344 may operate to shield and / or isolate sample 382 from magnetic fields that would otherwise reach sample 382 if third pole piece 344 were omitted.

[0090] In some examples, and as Figure 3 As shown in , the third pole piece 344 may be characterized by a taper angle 348, as measured between a surface (e.g., an outer surface) of the third pole piece 344 proximate the central hole 304 and / or the third terminal edge region 346 and a direction perpendicular to the central axis 302. Such a taper angle 348 may take any of a variety of values, examples of which include 0 degrees, at least 1 degree, at least 5 degrees, at least 10 degrees, at least 20 degrees, at least 30 degrees, at most 45 degrees, at most 25 degrees, at most 15 degrees, at most 7 degrees, and / or at most 3 degrees.

[0091] In various examples, and as Figure 3As shown, second pole piece 336 is a single piece extending continuously between first field region 360 and second field region 362. In this manner, for example, magnetic field lines extending through second pole piece 336 between first field region 360 and second field region 362 may be retained within the material of second pole piece 336 at all points between first field region 360 and second field region 362.

[0092] However, this is not required in all examples, and additionally within the scope of the present disclosure, the second pole piece 336 may include a plurality of spaced-apart pole piece segments. Figure 3 As shown by the dashed line in , the second pole piece 336 may include a first intermediate pole piece segment 340 and a second intermediate pole piece segment 342 at least partially spaced apart from the first intermediate pole piece segment 340. In such examples, the first pole piece 332 and the first intermediate pole piece segment 340 may be configured to direct the first magnetic field toward the central hole 304, while the second intermediate pole piece segment 342 and the third pole piece 344 may be configured to direct the second magnetic field toward the central hole 304.

[0093] In some examples, magnetic lens 300 may be configured such that each of first intermediate pole piece segment 340 and second intermediate pole piece segment 342 forms part of a common magnetic circuit that additionally includes each of first pole piece 332 and third pole piece 344 .

[0094] As discussed above, lens body 330 is generally configured such that first pole piece 332, second pole piece 336, and third pole piece 344 are at least partially spaced apart from one another, such as by first pole piece gap 350, second pole piece gap 354, first field region 36, and / or second field region 362. However, it is additionally within the scope of the present disclosure that two or more of first pole piece 332, second pole piece 336, and third pole piece 344 are connected to one another in various ways.

[0095] For example, in some examples, two or more of the first pole piece 332, the second pole piece 336, and the third pole piece 344 can be formed integrally with each other. As an example, the lens body 330 can include and / or be an integral unit that includes two or more of the first pole piece 332, the second pole piece 336, and the third pole piece 344 as respective parts thereof.

[0096] Additionally or alternatively, in some examples, two or more of the first pole piece 332, the second pole piece 336, and the third pole piece 344 may be formed separately and operably connected and / or attached to each other. Figure 3As shown by the dashed lines in , the lens body 330 may include a pole piece connection base 331 to which two or more of the first pole piece 332, the second pole piece 336, and the third pole piece 344 may be operably coupled, such as via bonding, welding, fasteners, etc. In other examples, such as when two or more of the first pole piece 332, the second pole piece 336, and the third pole piece 344 may be integrally formed with each other, the pole piece connection base 331 may represent a portion of the lens body 330 that extends between such pole pieces and interconnects such pole pieces.

[0097] Furthermore, in some examples, two or more of first pole piece 332, second pole piece 336, and third pole piece 344 may be completely spaced apart and / or disconnected from one another. For example, in some such examples, two or more such pole pieces may be spaced apart from one another such that each magnetic field line of a common magnetic circuit comprising the pole pieces must pass through free space (e.g., vacuum, air, or another ambient environment) to extend between the pole pieces in question.

[0098] Figure 4-7 The distribution and magnitude of the total magnetic field generated by the magnetic lens according to the present disclosure at respective magnitudes of the first magnetic field and the second magnetic field are shown. In particular, Figure 4-7 Each of may be understood to represent the magnetic field generated for a given value of the first current delivered to the first coil and a given value of the second current delivered to the second coil.

[0099] exist Figure 4-7 In each of the embodiments, the various components of the magnetic lens are similar to Figure 3 In particular, Figure 4-7 Various parts marked with numbers of the form "NXX" (where N represents the figure number) may be understood to represent Figure 3 Examples of corresponding parts marked with "3XX" in FIG. Thus, for example, Figure 4 A magnetic lens 400 is shown having a first pole piece 432, a second pole piece 436, and a third pole piece 444, which may be considered similar to and / or as Figure 3 332, the second pole piece 336 and the third pole piece 344. Therefore, it should be understood that Figure 4-7 Such components can be shared Figure 3 any suitable features, characteristics, configurations, etc. of corresponding parts, even when these parts are not referenced Figure 4-7 When discussing specifically.

[0100] Additionally, Figure 4-7Magnetic field lines corresponding to (e.g., primarily corresponding to) the first magnetic field (412 / 512 / 612) and the second magnetic field (522 / 622 / 722) are shown, as well as the magnitude of the total magnetic field (424 / 524 / 624 / 724) plotted as a function of axial position within and around the magnetic lens 400 / 500 / 600 / 700.

[0101] Figure 4 An example is shown in which a first current supplied to the first coil is 457 ampere-turns (At) and a second current supplied to the second coil is 0.

[0102] Figure 5 An example is shown in which the first current supplied to the first coil is 400At and the second current supplied to the second coil is 680At.

[0103] Figure 6 An example is shown in which the first current supplied to the first coil is 200At and the second current supplied to the second coil is 1167At.

[0104] Figure 7 An example is shown in which the first current supplied to the first coil is 0 and the second current supplied to the second coil is 1277At.

[0105] exist Figure 4-7 In each of the embodiments, the magnitude of the total magnetic field 424 / 524 / 624 / 724 can be seen to decay rapidly outside of the lens body 430 / 530 / 630 / 730, and particularly at the axial position corresponding to the central hole 404 / 504 / 604 / 704. Specifically, Figure 4-7 It is shown that the magnitude of the total magnetic field 424 / 524 / 624 / 724 at the sample position 484 / 584 / 684 / 784 is a smaller proportion of the maximum magnitude of the total magnetic field 424 / 524 / 624 / 724 within and / or immediately adjacent to the central aperture 404 / 504 / 604 / 704. In this manner, the magnetic lens disclosed herein can operate to substantially shield and / or isolate a sample positioned at the sample position 484 / 584 / 684 / 784 from the total magnetic field, thereby enabling the use of the composite magnetic lens in conjunction with magnetically sensitive samples.

[0106] Figure 8 8 is a flow chart depicting an example of a method 800 for making and / or using a magnetic lens (such as magnetic objective lens 138 and / or magnetic lens 300). Figure 8 As shown in , method 800 may include positioning a sample (e.g., sample 152 and / or sample 382) relative to a magnetic lens at 822 and operating the magnetic lens at 840 to focus a charged particle beam (e.g., charged particle beam 122) to a focus position (e.g., focus position 124 and / or sample position 384).

[0107] In some examples, positioning the sample at 822 includes positioning such that at least a portion of the sample is positioned at a focus position.

[0108] In some examples, positioning the sample at 822 includes positioning such that the sample and the magnetic lens are separated by a working distance, and operating the magnetic lens at 840 includes adjusting a magnification of the magnetic lens while the working distance remains constant.

[0109] In some examples, positioning the sample at 822 includes positioning the sample completely outside of the magnetic lens.

[0110] In some examples, operating the magnetic lens at 840 includes generating a magnetic field to focus the charged particle beam without immersing the sample in the magnetic field. For example, positioning the sample at 822 can include positioning such that the sample is at least substantially isolated from the magnetic field. In this manner, a sample that is at least substantially isolated from the magnetic field (e.g., spaced apart from and / or positioned away from the magnetic field) can be described as not immersed in the magnetic field.

[0111] In some examples, and as Figure 8 As shown, operating the magnetic lens at 840 includes generating a first magnetic field using a first coil of the magnetic lens at 842 and generating a second magnetic field using a second coil of the magnetic lens at 844. In some such examples, generating the first magnetic field at 842 and generating the second magnetic field at 844 are performed such that the first magnetic field and the second magnetic field form a common magnetic path. Additionally or alternatively, generating the first magnetic field at 842 and generating the second magnetic field at 844 can be performed such that the common magnetic path extends through each of a plurality of pole pieces of the magnetic lens.

[0112] In some examples, and as Figure 3 As shown, operating the magnetic lens includes adjusting one or both of the first magnetic field and the second magnetic field at 846 to change the magnification of the magnetic lens. In some such examples, adjusting one or both of the first magnetic field and the second magnetic field at 846 includes adjusting a ratio of a first field magnitude of the first magnetic field to a second field magnitude of the second magnetic field.

[0113] In some examples, the charged particle beam includes a plurality of charged particle beamlets. In such examples, operating the magnetic lens at 840 may include focusing the plurality of charged particle beamlets to respective focus positions in the focal plane. In such examples, operating the magnetic lens at 840 may also include adjusting one or both of the first magnetic field and the second magnetic field at 846 to change a pitch of the focused charged particle beamlets at the focal plane without shifting the position of the focal plane.

[0114] In some examples, and as Figure 8As shown, method 800 also includes, before operating the magnetic lens, assembling a charged particle microscope system (e.g., charged particle microscope system 100) including the magnetic lens at 820. In some such examples, the charged particle microscope system includes a charged particle source (e.g., charged particle source 120) configured to emit a charged particle beam along an optical axis (e.g., optical axis 112), and assembling the charged particle microscope system at 820 includes positioning the magnetic lens so that the optical axis extends through a central hole of the magnetic lens.

[0115] In some examples, and as Figure 8 As shown, method 800 includes manufacturing a magnetic lens at 810, the magnetic lens including a plurality of pole pieces defining at least two axial gaps and at least two independent coils respectively connected to the at least two axial gaps. For example, the plurality of pole pieces may include and / or serve as a first pole piece 332, a second pole piece 336, and a third pole piece 344, and the at least two axial gaps may include and / or serve as a first pole piece gap 350 and a second pole piece gap 354.

[0116] In some examples, manufacturing the magnetic lens at 810 includes integrally forming two or more of the first pole piece, the second pole piece, and the third pole piece as a single unit.

[0117] Additionally or alternatively, in some examples, manufacturing the magnetic lens at 810 may include separately forming two or more of the first pole piece, the second pole piece, and the third pole piece, and operably coupling two or more of the first pole piece, the second pole piece, and the third pole piece to each other.

[0118] In some examples, where fabricating the magnetic lens includes positioning at least two independent coils such that each coil of the at least two independent coils is positioned between a corresponding pair of pole pieces of the plurality of pole pieces.

[0119] General considerations

[0120] As used in this application and in the claims, the singular forms "a", "an", and "the" include plural forms unless the context clearly dictates otherwise. In addition, the term "comprising" means "including". Furthermore, the term "coupled" does not exclude the presence of intervening elements between the coupled items.

[0121] Unless otherwise indicated, the term "substantially" as used herein refers to the listed values ​​and / or properties and any values ​​and / or properties that are at least 75% of the listed values ​​and / or properties. Equivalently, the term "substantially" refers to the listed values ​​and / or properties and any values ​​and / or properties that differ from the listed values ​​and / or properties by at most 25%. For example, "substantially equal" refers to completely equal amounts, as well as amounts that differ from each other by at most 25%.

[0122] The systems, devices, and methods described herein should not be construed as limiting in any way. Rather, the present disclosure relates to all novel and non-obvious features and aspects of the various disclosed examples, either individually or in various combinations and sub-combinations formed with each other. The disclosed systems, methods, and devices are not limited to any particular aspect or feature or combination thereof, nor do the disclosed systems, methods, and devices require the presence of any one or more specific advantages or solutions to problems. Any theory of operation is for ease of explanation, but the disclosed systems, methods, and devices are not limited to such theory of operation.

[0123] Although the operations of some of the disclosed methods are described in a particular sequential order for ease of presentation, it should be understood that this manner of description includes rearrangement unless a particular order is required by the specific language described below. For example, the operations described in sequence may be rearranged or performed simultaneously in some cases. In addition, for simplicity, the accompanying drawings may not show the various ways in which the disclosed systems, methods, and devices can be used in conjunction with other systems, methods, and devices. In addition, the specification sometimes uses terms like "produce" and "provide" to describe the disclosed methods. These terms are high-level abstractions of the actual operations performed. The actual operations corresponding to these terms will vary depending on the specific implementation and can be easily discerned by those skilled in the art.

[0124] Innovations may be described in the general context of computer executable instructions, such as those included in program modules and executed in a computing system on a target real or virtual processor. In general, program modules or components include routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The functions of program modules may be combined or split between program modules as needed in various examples. Computer executable instructions for program modules may be executed in a local or distributed computing system. In general, a computing system or computing device may be local or distributed and may include any combination of special-purpose hardware and / or general-purpose hardware with software that implements the functions described herein.

[0125] In various examples described herein, a module (e.g., a component or an engine) may be "programmed" and / or "coded" to perform certain operations or provide certain functionality, indicating that computer executable instructions for the module may be executed to perform such operations, cause such operations to be performed, or otherwise provide such functionality. Although functionality described with respect to a software component, module, or engine may be performed as a discrete software unit (e.g., a procedure, function, class method), it need not be implemented as a discrete unit. That is, functionality may be incorporated into a larger or more general program, such as one or more lines of code in a larger or general program.

[0126] The algorithm described may be embodied, for example, as software or firmware instructions executed by a digital computer. For example, any of the disclosed methods may be performed by one or more of a computer or other computing hardware that is part of a microscopy tool. A computer may be a computer system comprising one or more processors (processing devices) and a tangible, non-transient computer-readable medium (e.g., one or more optical media disks, volatile memory devices (such as DRAM or SRAM), or non-volatile memory or storage devices (such as hard disk drives, NVRAM, and solid-state drives (e.g., flash drives)). The one or more processors may execute computer-executable instructions stored on one or more tangible, non-transient computer-readable media, and thereby perform any of the disclosed techniques. For example, software for executing any of the disclosed examples may be stored as computer-executable instructions on the one or more volatile, non-transient computer-readable media, which, when executed by the one or more processors, cause the one or more processors to perform any of the disclosed techniques or subsets of techniques.

[0127] The principles of the disclosed technology have been described and illustrated with reference to the examples illustrated, and it will be appreciated that the examples illustrated may be modified in arrangement and detail without departing from such principles. For example, the example elements executed in software may be implemented in hardware, and vice versa. In addition, the technology from any example may be combined with the technology described in any one or more examples in other examples. It will be understood that processes and functions such as those described with reference to the illustrated examples may be implemented in a single hardware or software module, or separate modules may be provided. The above specific arrangements are provided for ease of description, and other arrangements may be used.

[0128] Additional Embodiments of the Disclosed Technology

[0129] In view of the above specific implementation of the disclosed subject matter, the present application discloses the additional embodiments listed below. It should be noted that one feature of a separate example or one or more features of an example adopted in combination and optionally in combination with one or more features of one or more additional examples are also additional examples belonging to the disclosure of the present application.

[0130] Embodiment 1. A device comprising a magnetic lens configured to guide a charged particle beam to a sample position in a focal plane, wherein the magnetic lens comprises: a plurality of pole pieces defining at least two axial gaps; and at least two independent coils, which are respectively connected to the at least two axial gaps and are configured to generate a magnetic field so that the magnetic lens operates as a single objective lens with a variable main objective lens plane, wherein the variable main objective lens plane allows the magnification of the charged particle beam at the focal plane to be selectively adjusted without immersing the sample position in the magnetic field generated by the coils of the magnetic lens.

[0131] Embodiment 2. According to any embodiment herein, in particular the device described in Embodiment 1, wherein the magnetic lens includes a central hole, and wherein the plurality of pole pieces include: a first pole piece, which extends circumferentially around the central hole; a second pole piece, which extends circumferentially around the central hole and is at least partially arranged radially outside the first pole piece; and a third pole piece, which extends circumferentially around the central hole and is at least partially arranged radially outside the second pole piece.

[0132] Embodiment 3. A device according to any embodiment herein, in particular any one of embodiments 1 to 2, wherein at least two independent coils are configured to generate a total magnetic field, wherein the total magnetic field has a maximum focusing field amplitude representing the maximum amplitude of the total magnetic field within the magnetic lens, and wherein the amplitude of the total magnetic field measured at the sample position is at most 5% of the maximum focusing field amplitude.

[0133] Embodiment 4. A magnetic lens comprises: a lens body having a central hole; a first coil, which is supported by the lens body and configured to generate a first magnetic field having a first field size; a second coil, which is supported by the lens body and configured to generate a second magnetic field having a second field size; wherein the first magnetic field and the second magnetic field at least partially overlap spatially within the central hole, wherein the magnetic lens is configured to guide a charged particle beam to a sample position outside the lens body, and wherein the lens body includes a plurality of pole pieces, which confine the first magnetic field and the second magnetic field to an area away from the sample position.

[0134] Embodiment 5. A magnetic lens according to any embodiment herein, in particular Embodiment 4, wherein the plurality of pole pieces include: a first pole piece extending circumferentially around a center hole; a second pole piece extending circumferentially around the center hole and at least partially disposed radially outside the first pole piece; and a third pole piece extending circumferentially around the center hole and at least partially disposed radially outside the second pole piece.

[0135] Embodiment 6. A magnetic lens according to any embodiment herein, in particular any one of embodiments 4-5, wherein the magnetic lens is configured so that the first magnetic field and the second magnetic field overlap to form a total magnetic field, which is the sum of the first magnetic field and the second magnetic field, wherein the total magnetic field has a maximum focusing field amplitude representing the maximum amplitude of the total magnetic field within the central hole, and wherein the magnitude of the total magnetic field measured at the sample position is one or more of at most 5% of the maximum focusing field amplitude, at most 2% of the maximum focusing field amplitude, at most 1% of the maximum focusing field amplitude, at most 0.5% of the maximum focusing field amplitude, and at most 0.1% of the maximum focusing field amplitude.

[0136] Embodiment 7. A magnetic lens, comprising: a lens body having a central hole; a first coil, which is supported by the lens body and configured to generate a first magnetic field having a first field size; a second coil, which is supported by the lens body and configured to generate a second magnetic field having a second field size; wherein the magnetic lens is configured so that adjusting the ratio between the first field size and the second field size operates to adjust the position of the focal position of a charged particle beam passing through the central hole, wherein the focal position is positioned outside the lens body, and wherein each of the first magnetic field and the second magnetic field is positioned to a region away from the focal position.

[0137] Embodiment 8. A magnetic lens according to any embodiment herein, in particular Embodiment 7, wherein the magnetic lens is configured such that the first magnetic field and the second magnetic field overlap to form a total magnetic field, the total magnetic field being the sum of the first magnetic field and the second magnetic field, wherein the total magnetic field has a maximum focusing field amplitude representing the maximum amplitude of the total magnetic field within the central hole, and wherein the magnitude of the total magnetic field measured at the focal position is one or more of at most 5% of the maximum focusing field amplitude, at most 2% of the maximum focusing field amplitude, at most 1% of the maximum focusing field amplitude, at most 0.5% of the maximum focusing field amplitude, and at most 0.1% of the maximum focusing field amplitude.

[0138] Embodiment 9. A magnetic lens comprises: a lens body; a first coil, which is supported by the lens body and configured to generate a first magnetic field; and a second coil, which is supported by the lens body and configured to generate a second magnetic field; wherein the lens body comprises: a central hole, which is configured to receive a charged particle beam passing through the magnetic lens; a first pole piece, which extends circumferentially around the central hole; a second pole piece, which extends circumferentially around the central hole and is at least partially arranged radially outside the first pole piece; and a third pole piece, which extends circumferentially around the central hole and is at least partially arranged radially outside the second pole piece.

[0139] Embodiment 10. A magnetic lens according to any embodiment herein, in particular embodiment 9, wherein the first coil is at least partially disposed between the first pole piece and the second pole piece, and wherein the second coil is at least partially disposed between the second pole piece and the third pole piece.

[0140] Embodiment 11. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-10, wherein the first pole piece and the second pole piece are configured to guide the first magnetic field toward the center hole, and wherein the second pole piece and the third pole piece are configured to guide the second magnetic field toward the center hole.

[0141] Embodiment 12. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-11, wherein the magnetic lens is configured such that when the first coil generates a first magnetic field and the second coil generates a second magnetic field, the first pole piece, the second pole piece and the third pole piece together form a part of a common magnetic circuit.

[0142] Embodiment 13. A magnetic lens according to any embodiment herein, in particular embodiment 12, wherein the common magnetic circuit extends into the central hole.

[0143] Embodiment 14. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-13, wherein the magnetic lens is configured so that selectively changing one or both of the first magnetic field and the second magnetic field adjusts one or more of the following: (i) the position of the main objective plane of the magnetic lens; (ii) the magnification of the magnetic lens; and (iii) the focusing angle of the charged particle beam leaving the magnetic lens.

[0144] Embodiment 15. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-15, wherein the magnetic lens is configured to focus a charged particle beam onto a sample at one or both of a focusing position and a focal plane.

[0145] Embodiment 16. A magnetic lens according to any embodiment herein, in particular Embodiment 15, wherein the magnetic lens is configured so that selectively changing one or both of the first magnetic field and the second magnetic field adjusts the position of the main objective plane of the magnetic lens so that the focal plane of the charged particle beam remains unchanged.

[0146] Embodiment 17. A magnetic lens according to any embodiment herein, in particular any one of embodiments 15-16, wherein the magnetic lens is configured such that the sample can be positioned completely outside the magnetic lens during operational use of the magnetic lens.

[0147] Embodiment 18. A magnetic lens according to any embodiment herein, in particular any one of embodiments 15-17, wherein the magnetic lens is configured so that during operational use of the magnetic lens, the lens body and the sample are separated by a working distance, which is measured along a direction parallel to the central axis of the magnetic lens, and the working distance is one or more of at least 1 millimeter (mm), at least 5 mm, at least 10 mm, at least 15 mm, at least 20 mm, at most 25 mm, at most 17 mm, at most 12 mm, at most 7 mm and at most 2 mm.

[0148] Embodiment 19. A magnetic lens according to any embodiment herein, in particular any one of embodiments 15-18, wherein the magnetic lens is configured such that during operational use of the magnetic lens, the lens body and the sample are separated by a working distance, the working distance being measured along a direction parallel to the central axis of the magnetic lens, and wherein the magnetic lens is configured such that the magnification of the magnetic lens is adjustable while the working distance remains constant.

[0149] Embodiment 20. A magnetic lens according to any embodiment herein, in particular any one of embodiments 15-18, wherein the magnetic lens is configured such that the sample is at least substantially isolated from the first magnetic field and the second magnetic field during operational use of the magnetic lens.

[0150] Embodiment 21. A magnetic lens according to any embodiment herein, in particular any one of embodiments 15-20, wherein the magnetic lens is configured such that the first magnetic field and the second magnetic field overlap to form a total magnetic field, which is the sum of the first magnetic field and the second magnetic field.

[0151] Embodiment 22. A magnetic lens according to any embodiment herein, in particular Embodiment 21, wherein the total magnetic field has a maximum focusing field amplitude representing the maximum amplitude of the total magnetic field within the central hole, and wherein the magnitude of the total magnetic field measured at the sample is one or more of at most 40% of the maximum focusing field amplitude, at most 30% of the maximum focusing field amplitude, at most 20% of the maximum focusing field amplitude, at most 10% of the maximum focusing field amplitude, at most 5% of the maximum focusing field amplitude, at most 2% of the maximum focusing field amplitude, at most 1% of the maximum focusing field amplitude, at most 0.5% of the maximum focusing field amplitude, at most 0.1% of the maximum focusing field amplitude, and at most 0.01% of the maximum focusing field amplitude.

[0152] Embodiment 23. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-22, wherein a first magnetic field is generated with a first field size, wherein a second magnetic field is generated with a second field size, and wherein the magnetic lens is configured such that adjusting the ratio between the first field size and the second field size operates to adjust one or more of: (i) a main objective plane of the magnetic lens; (ii) a magnification of the magnetic lens; and (iii) a focusing angle of a charged particle beam leaving the magnetic lens.

[0153] Embodiment 24. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-23, wherein the charged particle beam comprises a plurality of charged particle beamlets, wherein the magnetic lens is configured to focus the plurality of charged particle beamlets to corresponding focusing positions in a focal plane, and.

[0154] Embodiment 25. A magnetic lens according to any embodiment herein, in particular embodiment 24, wherein the magnetic lens is configured to change the spacing of the focused charged particle beamlets at the focal plane.

[0155] Embodiment 26. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-25, wherein the charged particle beam travels along an optical axis parallel to a central axis of the magnetic lens extending through the central hole.

[0156] Embodiment 27. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-26, wherein the magnetic lens defines a central axis and wherein the lens body is at least substantially axially symmetric about the central axis.

[0157] Embodiment 28. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-27, wherein the magnetic lens defines a central axis and wherein each of the first pole piece, the second pole piece and the third pole piece extends completely circumferentially around the central axis.

[0158] Embodiment 29. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-28, wherein one or more of the first pole piece, the second pole piece and the third pole piece at least partially defines a central hole.

[0159] Embodiment 30. A magnetic lens according to any embodiment herein, in particular embodiment 29, wherein the central hole has a hole diameter measured in a direction perpendicular to the central axis of the magnetic lens, and the hole diameter is one or more of at least 0.1 mm, at least 0.5 mm, at least 1 mm, at least 5 mm, at most 10 mm, at most 2 mm, at most 0.7 mm and at most 0.2 mm.

[0160] Embodiment 31. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-30, wherein the second pole piece is positioned between the first pole piece and the third pole piece.

[0161] Embodiment 32. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-31, wherein the first pole piece terminates at a first terminal edge region, wherein the second pole piece terminates at a second terminal edge region, and wherein the third pole piece terminates at a third terminal edge region.

[0162] Embodiment 33. A magnetic lens according to any embodiment herein, in particular Embodiment 32, wherein each of the first terminal edge region, the second terminal edge region, and the third terminal edge region comprises a substantially annular surface.

[0163] Embodiment 34. A magnetic lens according to any embodiment herein, in particular any one of embodiments 32-33, wherein each of the first terminal edge region, the second terminal edge region and the third terminal edge region is characterized by their respective diameters as measured along a direction perpendicular to the central axis of the magnetic lens, and wherein the respective diameters of the first terminal edge region, the second terminal edge region and the third terminal edge region differ from each other by at most 20%.

[0164] Embodiment 35. A magnetic lens according to any embodiment herein, in particular any one of embodiments 32-34, wherein the first terminal edge region and the second terminal edge region are separated by a first pole piece gap having a first gap width, and wherein the second terminal edge region and the third terminal edge region are separated by a second pole piece gap having a second gap width.

[0165] Embodiment 36. A magnetic lens according to any embodiment herein, in particular embodiment 35, wherein the ratio of the first gap width to the second gap width is one or more of at least 1:10, at least 1:5, at least 1:2, at least 1:1, at least 2:1, at least 5:1, at most 10:1, at most 5:1, at most 2:1, at most 1:1, at most 1:2, at most 1:5 and / or at most 1:10.

[0166] Embodiment 37. A magnetic lens according to any embodiment herein, in particular any one of embodiments 35-36, wherein one or both of the first pole piece gap and the second pole piece gap face the central axis of the magnetic lens.

[0167] Embodiment 38. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-37, wherein two or more of the first pole piece, the second pole piece and the third pole piece are formed integrally with each other.

[0168] Embodiment 39. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-38, wherein two or more of the first pole piece, the second pole piece and the third pole piece are formed separately and are operably connected to each other.

[0169] Example 40. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-39, wherein the lens body further comprises a pole piece connection base, and wherein two or more of the first pole piece, the second pole piece and the third pole piece are connected to each other via the pole piece connection base.

[0170] Embodiment 41. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-40, wherein during operational use of the magnetic lens, the third pole piece is close to the sample relative to each of the first pole piece and the second pole piece.

[0171] Embodiment 42. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-41, wherein the third pole piece is characterized by a cone angle as measured between a surface of the third pole piece close to the center hole and a direction perpendicular to the center axis of the magnetic lens, the cone angle being one or more of 0 degrees, at least 1 degree, at least 5 degrees, at least 10 degrees, at least 20 degrees, at least 30 degrees, at most 45 degrees, at most 25 degrees, at most 15 degrees, at most 7 degrees and at most 3 degrees.

[0172] Embodiment 43. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-42, wherein the second pole piece comprises a plurality of spaced-apart pole piece segments.

[0173] Embodiment 44. A magnetic lens according to any embodiment herein, in particular Embodiment 43, wherein the plurality of spaced-apart pole piece segments include a first intermediate pole piece segment and a second intermediate pole piece segment at least partially spaced apart from the first intermediate pole piece segment.

[0174] Embodiment 45. A magnetic lens according to any embodiment herein, in particular embodiment 44, wherein the first pole piece and the first intermediate pole piece segment are configured to guide the first magnetic field toward the center hole, and wherein the second intermediate pole piece segment and the third pole piece are configured to guide the second magnetic field toward the center hole.

[0175] Embodiment 46. A magnetic lens according to any embodiment herein, in particular any one of embodiments 44-45, wherein, during operational use of the magnetic lens, each of the first intermediate pole piece segment and the second intermediate pole piece segment forms part of a common magnetic circuit, which additionally includes each of the first pole piece and the third pole piece.

[0176] Embodiment 47. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-46, wherein the second pole piece is a monolithic pole piece.

[0177] Embodiment 48. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-47, wherein the first pole piece and the second pole piece define a first field region therebetween, wherein the second pole piece and the third pole piece define a second field region therebetween that is separated from the first field region, and wherein the second pole piece extends continuously between the first field region and the second field region.

[0178] Embodiment 49. A magnetic lens according to any embodiment herein, in particular any one of embodiments 9-48, wherein the first pole piece and the second pole piece define a first field region therebetween, wherein the second pole piece and the third pole piece define a second field region therebetween that is separated from the first field region, and wherein the first field region is open to the center hole.

[0179] Embodiment 50. A magnetic lens according to any embodiment herein, in particular embodiment 49, wherein the second field region is open to the central hole.

[0180] Embodiment 51. A magnetic lens according to any embodiment herein, in particular any one of embodiments 49-50, wherein the magnetic lens is configured so that the first pole piece, the second pole piece and the third pole piece together form a portion of a common magnetic circuit extending through each of the first field region and the second field region.

[0181] Embodiment 52. A magnetic lens according to any embodiment herein, in particular any one of embodiments 49-51, wherein the first field region extends between the first coil and the central hole, and wherein the second field region extends between the second coil and the central hole.

[0182] Example 53. A magnetic lens according to any embodiment herein, in particular any one of embodiments 49-52, wherein the first pole piece and the second pole piece are configured to guide the first magnetic field through the first field region to the central hole, and wherein the second pole piece and the third pole piece are configured to guide the second magnetic field through the second field region to the central hole.

[0183] Embodiment 54. A charged particle microscope system, comprising: a charged particle source, which emits a charged particle beam along an optical axis and toward a sample; a sample holder, which is configured to support the sample; and a magnetic objective lens, which is configured to focus the charged particle beam to a focusing position corresponding to the position of the sample, wherein the magnetic objective lens comprises any embodiment described herein, in particular the magnetic lens described in any one of Embodiments 1-52.

[0184] Embodiment 55. A charged particle microscope system according to any embodiment herein, in particular Embodiment 54, wherein the charged particle beam comprises an electron beam, and wherein the charged particle microscope system is configured to operate as a scanning electron microscope (SEM).

[0185] Embodiment 56. According to any embodiment herein, in particular the charged particle microscope system described in Embodiment 55, further comprising an electron detector configured to detect electrons emitted from the sample.

[0186] Embodiment 57. A charged particle microscope system according to any embodiment herein, in particular Embodiment 56, wherein the electron detector is configured to detect secondary electrons generated via interaction between the charged particle beam and the sample.

[0187] Embodiment 58. According to any embodiment herein, in particular any one of embodiments 54-57, the charged particle microscope system further includes one or more scanning coils configured to deflect the charged particle beam to scan the charged particle beam across the sample.

[0188] Embodiment 59. According to any embodiment of the present invention, in particular any one of embodiments 54-58, the charged particle microscope system further includes a focusing lens configured to focus the charged particle beam toward the sample.

[0189] Example 60. According to any embodiment herein, in particular any one of embodiments 54-59, the charged particle microscope system further includes a controller configured to at least partially control the operation of the charged particle microscope system.

[0190] Embodiment 61. A charged particle microscope system according to any embodiment herein, in particular Embodiment 60, wherein the controller is configured to at least partially control the operation of the magnetic objective lens.

[0191] Example 62. A charged particle microscope system according to any embodiment herein, in particular any one of embodiments 60-61, wherein the magnetic objective comprises a first coil configured to generate a first magnetic field and a second coil configured to generate a second magnetic field, and wherein the controller is configured to selectively and dynamically change one or both of the first magnetic field and the second magnetic field.

[0192] Example 63. A charged particle microscope system according to any embodiment herein, in particular any one of embodiments 60-62, wherein the controller includes a first current source configured to transmit a first current to the first coil and a second current source configured to transmit a second current to the second coil, and wherein the controller is configured to selectively change one or both of the first current and the second current to adjust the focal plane of the magnetic objective lens.

[0193] Example 64. A charged particle microscope system according to any embodiment herein, in particular any one of embodiments 60-63, wherein the controller includes one or more input devices for receiving input from a human user to at least partially guide the operation of the charged particle microscope system.

[0194] Embodiment 65. A charged particle microscope system according to any embodiment herein, in particular any one of embodiments 60-64, wherein the controller includes one or more output devices for conveying information to a human user.

[0195] Embodiment 66. A charged particle microscope system according to any embodiment herein, in particular any one of embodiments 54-65, wherein the sample holder is positioned completely outside the magnetic objective lens.

[0196] Example 67. A charged particle microscope system according to any embodiment herein, in particular any one of embodiments 54-66, wherein the charged particle microscope system is configured such that the sample is completely positioned outside the magnetic objective lens during operational use of the charged particle microscope system.

[0197] Embodiment 68. A method, comprising: positioning a sample relative to a magnetic lens; and operating the magnetic lens to focus a charged particle beam to a focusing position, wherein the magnetic lens is any one of the embodiments described herein, in particular any one of embodiments 1-53.

[0198] Embodiment 69. A method according to any embodiment herein, in particular embodiment 68, wherein positioning the sample comprises positioning such that at least a portion of the sample is positioned at a focus position.

[0199] Embodiment 70. A method according to any embodiment herein, in particular any one of embodiments 68-69, wherein positioning the sample includes positioning so that the sample and the magnetic lens are separated by a working distance, and wherein operating the magnetic lens includes adjusting the magnification of the magnetic lens while the working distance remains constant.

[0200] Embodiment 71. A method according to any embodiment herein, in particular embodiment 70, wherein positioning the sample includes positioning such that the working distance is one or more of at least 1 millimeter (mm), at least 5 mm, at least 10 mm, at least 15 mm, at least 20 mm, at most 25 mm, at most 17 mm, at most 12 mm, at most 7 mm, and at most 2 mm.

[0201] Embodiment 72. A method according to any embodiment herein, in particular any one of embodiments 68-71, wherein positioning the sample includes positioning the sample completely outside the magnetic lens.

[0202] Embodiment 73. A method according to any embodiment herein, in particular any one of embodiments 68-72, wherein operating the magnetic lens comprises generating a magnetic field to focus the charged particle beam without immersing the sample in the magnetic field.

[0203] Embodiment 74. A method according to any embodiment herein, in particular any one of embodiments 68-73, wherein operating the magnetic lens includes generating a magnetic field to focus the charged particle beam, and wherein positioning the sample includes positioning the sample so that the sample is at least substantially isolated from the magnetic field.

[0204] Example 75. A method according to any embodiment herein, in particular any one of embodiments 68-74, wherein operating the magnetic lens includes: generating a first magnetic field using a first coil of the magnetic lens; and generating a second magnetic field using a second coil of the magnetic lens, and wherein generating the first magnetic field and generating the second magnetic field are performed so that the first magnetic field and the second magnetic field form a common magnetic circuit.

[0205] Embodiment 76. The method according to any embodiment herein, in particular embodiment 75, wherein generating the first magnetic field and generating the second magnetic field are performed so that a common magnetic path extends through each of the plurality of pole pieces.

[0206] Embodiment 77. A method according to any embodiment herein, in particular any one of embodiments 75-76, wherein operating the magnetic lens includes adjusting one or both of the first magnetic field and the second magnetic field to move the position of the main objective plane of the magnetic lens.

[0207] Embodiment 78. A method according to any embodiment herein, in particular embodiment 77, wherein adjusting one or both of the first magnetic field and the second magnetic field comprises adjusting a ratio of a first field magnitude of the first magnetic field to a second field magnitude of the second magnetic field.

[0208] Example 79. A method according to any embodiment herein, in particular any one of embodiments 75-78, wherein the charged particle beam includes a plurality of charged particle sub-beams, wherein operating the magnetic lens includes: focusing the plurality of charged particle sub-beams to corresponding focusing positions in a focal plane; and adjusting one or both of the first magnetic field and the second magnetic field to change the spacing of the focused charged particle sub-beams at the focal plane without moving the position of the focal plane.

[0209] Embodiment 80. The method according to any embodiment herein, in particular any one of embodiments 68-79, further comprises assembling a charged particle microscope system including a magnetic lens before operating the magnetic lens.

[0210] Example 81. A method according to any embodiment herein, in particular Example 80, wherein the charged particle microscope system includes a charged particle source configured to emit a charged particle beam along an optical axis, and wherein assembling the charged particle microscope system includes positioning the magnetic lens so that the optical axis extends through a central hole of the magnetic lens.

[0211] Embodiment 82. A method comprising: manufacturing a magnetic lens, the magnetic lens comprising a plurality of pole pieces defining at least two axial gaps and at least two independent coils respectively connected to the at least two axial gaps.

[0212] Example 83. A method according to any embodiment herein, in particular Example 82, wherein the plurality of pole pieces include a first pole piece, a second pole piece and a third pole piece, and wherein manufacturing the magnetic lens includes integrally forming two or more of the first pole piece, the second pole piece and the third pole piece into a single unit.

[0213] Example 84. A method according to any embodiment herein, in particular any one of embodiments 82-83, wherein the plurality of pole pieces include a first pole piece, a second pole piece and a third pole piece, and wherein manufacturing the magnetic lens includes: forming two or more of the first pole piece, the second pole piece and the third pole piece respectively; and operably connecting two or more of the first pole piece, the second pole piece and the third pole piece to each other.

[0214] Embodiment 85. A method according to any embodiment herein, in particular any one of embodiments 82-84, wherein manufacturing a magnetic lens includes positioning at least two independent coils such that each of the at least two independent coils is positioned between a corresponding pair of pole pieces among a plurality of pole pieces.

[0215] Unless otherwise stated, the features described herein with respect to any embodiment may be combined with other features described in any one or more other embodiments. For example, any one or more features of a magnetic lens may be combined with any one or more features of another magnetic lens.

[0216] In view of the many possible ways in which the principles of the present disclosure may be applied, it should be recognized that the illustrated configurations depict examples of the disclosed technology and should not be taken as limiting the scope of the disclosure or the claims. Rather, the scope of the claimed subject matter is defined by the following claims and their equivalents.

Claims

1. A device comprising: A magnetic lens configured to direct a charged particle beam to a sample position in a focal plane, wherein the magnetic lens comprises: a plurality of pole pieces defining at least two axial gaps; and at least two independent coils, the at least two independent coils being respectively in communication with the at least two axial gaps and being configured to generate a magnetic field such that the magnetic lens operates as a single objective lens with a variable main objective lens plane, Wherein the variable main objective plane allows selective adjustment of the magnification of the charged particle beam at the focal plane without immersing the sample position in the magnetic field generated by the coils of the magnetic lens.

2. The device according to claim 1, wherein: The magnetic lens comprises a central hole, and wherein the plurality of pole pieces comprises: a first pole piece extending circumferentially around the central hole; a second pole piece extending circumferentially around the central hole and disposed at least partially radially outward of the first pole piece; and A third pole piece extends circumferentially around the central hole and is at least partially disposed radially outside the second pole piece.

3. The device according to claim 1, wherein: The at least two independent coils are configured to generate a total magnetic field, wherein the total magnetic field has a maximum focus field amplitude representing a maximum amplitude of the total magnetic field within the magnetic lens, and wherein the amplitude of the total magnetic field measured at the sample position is at most 5% of the maximum focus field amplitude.

4. A magnetic lens, comprising: Lens body; a first coil supported by the lens body and configured to generate a first magnetic field; and a second coil supported by the lens body and configured to generate a second magnetic field; The lens body comprises: a central aperture configured to receive a charged particle beam passing through the magnetic lens; a first pole piece extending circumferentially around the central hole; a second pole piece extending circumferentially around the central hole and disposed at least partially radially outward of the first pole piece; and A third pole piece extends circumferentially around the central hole and is at least partially disposed radially outside the second pole piece.

5. The magnetic lens according to claim 4, wherein: The magnetic lens is configured such that when the first coil generates the first magnetic field and the second coil generates the second magnetic field, the first pole piece, the second pole piece, and the third pole piece together form a portion of a common magnetic circuit.

6. The magnetic lens according to claim 4, wherein: The magnetic lens is configured to focus the charged particle beam onto a sample at a focal plane, and wherein the magnetic lens is configured so that selectively changing one or both of the first magnetic field and the second magnetic field adjusts the position of the main objective plane of the magnetic lens so that the focal plane of the charged particle beam remains unchanged.

7. The magnetic lens according to claim 6, wherein: The magnetic lens is configured such that the first magnetic field and the second magnetic field overlap to form a total magnetic field, the total magnetic field being the sum of the first magnetic field and the second magnetic field, wherein the total magnetic field has a maximum focusing field amplitude representing a maximum amplitude of the total magnetic field within the central aperture, and wherein a magnitude of the total magnetic field measured at the sample is at most 2% of the maximum focusing field amplitude.

8. The magnetic lens according to claim 4, wherein: The first coil is at least partially disposed between the first pole piece and the second pole piece, and wherein the second coil is at least partially disposed between the second pole piece and the third pole piece.

9. The magnetic lens according to claim 4, wherein: The magnetic lens defines a central axis extending through the central hole, wherein each of the first pole piece, the second pole piece, and the third pole piece extends completely circumferentially around the central axis, and wherein one or more of the first pole piece, the second pole piece, and the third pole piece at least partially defines the central hole.

10. The magnetic lens according to claim 4, wherein: The first pole piece terminates at a first terminal edge region, wherein the second pole piece terminates at a second terminal edge region, wherein the third pole piece terminates at a third terminal edge region, wherein the first terminal edge region and the second terminal edge region are separated by a first pole piece gap, wherein the second terminal edge region and the third terminal edge region are separated by a second pole piece gap, and wherein each of the first pole piece gap and the second pole piece gap faces the central axis of the magnetic lens.

11. The magnetic lens according to claim 4, wherein: The first pole piece and the second pole piece define a first field region therebetween, wherein the second pole piece and the third pole piece define a second field region therebetween that is separate from the first field region, wherein each of the first field region and the second field region is open to the center hole, and wherein the magnetic lens is configured such that the first pole piece, the second pole piece, and the third pole piece together form a portion of a common magnetic circuit extending through each of the first field region and the second field region.

12. The magnetic lens according to claim 11, wherein: The first field region extends between the first coil and the central aperture, and wherein the second field region extends between the second coil and the central aperture.

13. A charged particle microscope system comprising: a charged particle source configured to emit a charged particle beam along an optical axis and toward the sample; a sample holder configured to support the sample; and a magnetic objective lens configured to focus the charged particle beam to a focus position corresponding to a position of the sample; The magnetic objective lens comprises: a lens body having a central aperture through which the charged particle beam extends; a first coil supported by the lens body and configured to generate a first magnetic field having a first field magnitude; and a second coil supported by the lens body and configured to generate a second magnetic field having a second field magnitude, wherein the magnetic objective lens is configured such that adjusting the ratio between the first field size and the second field size operates to adjust the magnification of the magnetic objective lens, wherein the focus position is positioned outside the lens body, and wherein each of the first magnetic field and the second magnetic field is positioned to a region away from the focus position.

14. The charged particle microscope system according to claim 13, wherein: The magnetic objective is configured such that the sample is at least substantially isolated from the first magnetic field and the second magnetic field during operational use of the charged-particle microscopy system.

15. The charged particle microscope system according to claim 13, wherein: The lens body comprises: a first pole piece extending circumferentially around the central hole; a second pole piece extending circumferentially around the central hole and disposed at least partially radially outward of the first pole piece; and a third pole piece extending circumferentially around the central hole and at least partially disposed radially outside the second pole piece, The magnetic objective lens is configured such that when the first coil generates the first magnetic field and the second coil generates the second magnetic field, the first pole piece, the second pole piece and the third pole piece together form a part of a common magnetic circuit.

16. The charged particle microscope system according to claim 13, wherein: The charged particle beam comprises an electron beam, and wherein the charged particle microscope system is configured to operate as a scanning electron microscope (SEM).

17. A method comprising: Positioning the sample relative to the magnetic lens; as well as operating the magnetic lens to focus the charged particle beam to a focusing position, The magnetic lens comprises: a plurality of pole pieces, the plurality of pole pieces defining at least two axial gaps; and At least two independent coils are respectively connected to the at least two axial gaps, so that the magnetic lens operates as a single objective lens with a variable main objective plane.

18. The method according to claim 17, wherein: Positioning the sample includes positioning the sample completely outside the magnetic lens, and wherein operating the magnetic lens includes generating a magnetic field to focus the charged particle beam without immersing the sample in the magnetic field.

19. The method according to claim 17, wherein: Operating the magnetic lens comprises: generating a first magnetic field using a first coil of the magnetic lens; and generating a second magnetic field using a second coil of the magnetic lens, Wherein operating the magnetic lens includes adjusting one or both of the first magnetic field and the second magnetic field to change the magnification of the magnetic lens without changing the working distance between the magnetic lens and the focus position.

20. The method according to claim 17, wherein: The at least two independent coils include a first coil configured to generate a first magnetic field and a second coil configured to generate a second magnetic field, wherein the charged particle beam includes a plurality of charged particle beamlets, and wherein operating the magnetic lens includes: focusing the plurality of charged particle beamlets to respective focus positions in a focal plane; and One or both of the first magnetic field and the second magnetic field are adjusted to change the spacing of the focused charged particle beamlets at the focal plane without moving the position of the focal plane.

Images