align="char" char="." colname="5" colwidth="56pt" />

Baseline
FIG. 1
16
−2319
8.9

First
FIG. 2
30
−3067
19

Second
FIG. 3
28
−1616
12

Third
FIG. 4
25
−1388
10

Fourth
FIG. 5
27
−244
11

Fifth
FIG. 6
26
−123
8.7

A baseline proximity-electrode design without an enlarged aperture and without protrusions, as indicated by FIG. 1 and the associated entry in Table 1, is used in the following for comparing the proximity-electrode designs with different extents of aperture enlargement and different extents and designs of protrusions.

The proximity-electrode shown in FIG. 1 is referred to herein as a baseline design. As shown, the proximity-electrode 140 has a body 300 having an aperture 340 within the body 300. The proximity-electrode 140 according to the baseline design includes a (non-enlarged) aperture 340, approximately 2.3 mm in radius and absent protrusions.

The proximity-electrode in FIG. 2 is referred to herein as a first design, which is provided as an example for illustrating features which can be provided singly/separately or combined with other features, as illustrated by aspects and embodiments described herein.

As shown in FIG. 2, the proximity-electrode 140 has a body 300 having an aperture 340 within the body 300. The proximity-electrode 140 according to the first design includes an (enlarged) aperture 340, approximately 3.2 mm in radius, with protrusions 310. As shown, the protrusions 310 cantilever radially into the aperture 340.

As shown in FIG. 2, the protrusions 310 are about 1 mm long, which may be understood as less than halfway towards the center of the aperture or as having a cantilever length less than half of the radius of the aperture.

In comparison to the baseline design, a proximity-electrode according to the first design has a substantially improved clear aperture size (almost doubled), whilst the proximity-electrode voltage is within the same order of magnitude, although peak surface electric field is increased.

Thus, the comparison of the first design to the baseline design shows that by the provision of protrusions 310, clear aperture size can be markedly improved without substantial effect on proximity-electrode voltage, since the increase in field penetration from the enlarged aperture is mitigated by the protrusions.

The proximity-electrode in FIG. 3 is referred to herein as a second design, which is provided as an example for illustrating features which can be provided singly/separately or combined with other features, as illustrated by aspects and embodiments described herein.

As shown in FIG. 3, the proximity-electrode 140 has a body 300 having an aperture 340 within the body 300. The proximity-electrode 140 according to the second design includes an (enlarged) aperture 340, approximately 3.2 mm in radius, with protrusions 310. As shown, the protrusions 310 cantilever radially into the aperture 340.

As shown in FIG. 3, the protrusions 310 are about 1.6 mm long, which may be understood as cantilevering less than halfway towards the center of the aperture 340 or as having a cantilever length less than half of the radius of the aperture 340. The protrusions 310 have bulbous ends 330, which may be understood as ends with enlarged radius, in this example by about 50%, relative to the radius at the middle or stem 320 of the respective protrusion 310.

In comparison to the baseline design, a proximity-electrode according to the second design has a substantially improved clear aperture size (similarly improved as the first design) and a beneficially reduced proximity-electrode voltage (relative to the first design, the second design is almost doubly improved), whilst peak surface electric field is within the same order of magnitude (relative to the first design, is much improved).

Thus, the comparison of the second design to the baseline design shows that by the provision of protrusions 310 with bulbous ends 330 (a bulbous end may be understood as an end having a radius that is enlarged relative to a radius at the middle or stem 320 of the respective protrusion 310), clear aperture size and proximity-electrode voltage can be simultaneously improved, without substantial increase in peak surface electric field.

The proximity-electrode in FIG. 4 is referred to herein as a third design, which is provided as an example for illustrating features which can be provided singly/separately or combined with other features, as illustrated by aspects and embodiments described herein.

As shown in FIG. 4, the proximity-electrode 140 has a body 300 having an aperture 340 within the body 300. The proximity-electrode 140 according to the third design includes an (enlarged) aperture 340, approximately 3.2 mm in radius, with protrusions 310. As shown, the protrusions 310 cantilever radially into the aperture 340.

As shown in FIG. 4, the protrusions 310 are about 1.6 mm long, which may be understood as cantilevering about halfway towards the center of the aperture 340 or as having a cantilever length about half of the radius of the aperture 340. The protrusions 310 have doubly bulbous ends 330, which may be understood as having ends with doubly enlarged radius, in this example by about 100%, relative to the radius at the middle or stem 320 of the respective protrusion.

In comparison to the baseline design, a proximity-electrode according to the third design has a substantially improved clear aperture size (similarly improved as the first and second designs), a beneficially reduced proximity-electrode voltage (relative to the second design, is improved), whilst peak surface electric field is within the same order of magnitude (relative to the first and second designs, is improved).

Thus, the comparison of the third design to the baseline design shows that by the provision of protrusions 310 with doubly bulbous ends (ends having radius at least double of a radius at the middle or stem 320 of the respective protrusion 310), clear aperture size and proximity-electrode voltage can be simultaneously improved, whilst peak surface electric field remains relatively unchanged.

The proximity-electrode in FIG. 5 is referred to herein as a fourth design, which is provided as an example for illustrating features which can be provided singly/separately or combined with other features, as illustrated by aspects and embodiments described herein.

As shown in FIG. 5, the proximity-electrode 140 has a body 300 having an aperture 340 within the body 300. The proximity-electrode 140 according to the third design includes an (enlarged) aperture 340, approximately 3.2 mm in radius, with protrusions 310. As shown, the protrusions 310 cantilever radially into the aperture 340.

As shown in FIG. 5, the protrusions 310 are about 2.2 mm long, which may be understood as cantilevering more than halfway towards the center of the aperture 340 or as having a cantilever length more than half of the radius of the aperture 340.

In comparison to the baseline design, a proximity-electrode according to the fourth design has a substantially improved clear aperture size (similarly improved as the first, second and third designs), substantially improved proximity-electrode voltage (relative to the first, second and third designs, is an order of magnitude better), whilst peak surface electric field is within the same order of magnitude (similar to the second and third designs).

Thus, the comparison of the fourth design to the baseline design shows that by the provision of protrusions cantilevering more than halfway towards the center of the aperture, or having a cantilever length more than half of a radius of the aperture, clear aperture size and proximity-electrode voltage can be tremendously improved without much change in peak surface electric field.

The proximity-electrode in FIG. 6 is referred to herein as a fifth design, which is provided as an example for illustrating features which can be provided singly/separately or combined with other features, as illustrated by aspects and embodiments described herein.

As shown in FIG. 6, the proximity-electrode 140 has a body 300 having an aperture 340 within the body 300. The proximity-electrode 140 according to the fifth design includes an (enlarged) aperture 340, approximately 3.2 mm in radius, with protrusions 310. As shown, the protrusions 310 cantilever radially into the aperture 340.

As shown in FIG. 6, the protrusions 310 are about 2.2 mm long, which may be understood as cantilevering more than halfway towards the center of the aperture 340 or as having a cantilever length more than half of the radius of the aperture 340. The protrusions 310 have bulbous ends 330, which may be understood as having ends with enlarged radius, in this example by about 50%, relative to the radius at the middle or stem 320 of the respective protrusion.

In comparison to the baseline design, a proximity-electrode according to the fifth design has not only a substantially improved clear aperture size (similarly improved as the first, second, third and fourth designs) and a substantially improved proximity-electrode voltage (similarly improved as the fourth design), but even an improved peak surface electric field.

Thus, the comparison of the fifth design to the baseline design shows that by the provision of protrusions cantilevering more than halfway towards the center of the aperture, or having a cantilever length more than half of a radius of the aperture, and having bulbous ends 330 (ends having radius enlarged relative to a radius at the middle or stem 320 of the respective protrusion 310), all of clear aperture size, proximity-electrode voltage and peak surface electric field can be improved, in particular clear aperture size and proximity-electrode voltage.

Further aspects, embodiments and examples of the proximity-electrode are described in the following.

FIG. 7 showing a proximity-electrode according to aspects and embodiments described herein.

According to an aspect, a proximity-electrode 140 for a charged particle beam device includes a body 300 having an aperture 340 within the body 300; and the body having a plurality of protrusions 310 cantilevering radially into the aperture 340, the aperture 340 and the protrusions 310 having an n-fold rotational symmetry, n being an integer.

Beneficially, a proximity-electrode with a large clear aperture size, low field penetration through the proximity-electrode thus low proximity-electrode voltage and minimal shadowing is provided.

According to an embodiment, which can be combined with other embodiments, the protrusions 310 have a minimum radius of curvature such that a maximum magnitude of a surface electric field on the protrusions 310 is less than 3 times a maximum magnitude of a surface electric field on a body 300 of the proximity-electrode 140.

According to an embodiment, which can be combined with other embodiments, each protrusion 310 has a minimum radius of curvature that is at least half of a width of the protrusion 310.

Beneficially, edges are rounded and a proximity-electrode with low field penetration through the proximity-electrode thus low proximity-electrode voltage and reduced peak surface electric field can be attained.

According to an embodiment, which can be combined with other embodiments, a tip or end 330 of each protrusion 310 has a minimum radius of curvature at least equal to, preferably larger than, a minimum radius of curvature at a middle or stem 320 of the respective protrusion 310.

Beneficially, protrusion tips are especially rounded and a proximity-electrode with reduced peak surface electric field is provided, and further, low field penetration through the proximity-electrode thus low proximity-electrode voltage is provided.

According to an embodiment, which can be combined with other embodiments, a length of each protrusion 310 is at least 5% of a radius of the aperture 340 and at most 80% of a radius of the aperture 340.

According to an embodiment, which can be combined with other embodiments described herein, a length of each protrusion 310 is at least 5% of a radius of the aperture 340 and/or at most 80% of a radius of the aperture (in a plane of the aperture or perpendicular to an axis of the proximity-electrode 140, to an optical axis of the charged particle beam device, and/or to an axis of the primary charged particle beam).

According to an embodiment, which can be combined with other embodiments described herein, a length of each protrusion 310 is more than 50% and/or less than 80% of a radius of the aperture 340 (in a plane of the aperture 340 or perpendicular to an axis of the proximity-electrode 140, to an optical axis of the charged particle beam device, and/or to an axis of the primary charged particle beam).

Beneficially, low field penetration is provided, which is particularly beneficial when provided in combination with a large aperture. Furthermore, the provision of protrusion lengths extending substantially into the aperture, without contacting each other and without distorting the primary charged particle beam, beneficially enables a proximity-electrode with a large clear aperture size with minimal field penetrating through the proximity-electrode, minimal proximity-electrode voltage and minimal peak surface electric field.

It may be understood that the tip or end 330 of each protrusion 310 is unsupported, free and/or does not contact or connect with a body 300 of the proximity-electrode 140, or (any part of) another protrusion 310 of the proximity-electrode 140.

It may be understood that a length of each protrusion 310 is a length in a direction of an axis of the protrusion 310, in a plane of the aperture 340, in a direction perpendicular to an axis of the proximity-electrode 140, and/or in a direction perpendicular to an optical axis of the charged particle beam device.

According to an embodiment, which can be combined with other embodiments, a radius of the aperture 340 is at least 1.5 mm and/or at most 5.5 mm, preferably at least 2 mm and/or at most 5 mm, more preferably at least 2.5 mm and/or at most 4.5 mm, or most preferably at least 3 mm and/or at most 4 mm.

According to an embodiment, which can be combined with other embodiments, an aperture size, a clear aperture size or a clear area of the aperture 340 in a plane of the aperture 340 is at least 10 mm²and/or at most 95 mm², preferably at least 15 mm²and/or at most 80 mm², more preferably at least 20 mm²and/or at most 65 mm², or most preferably at least 25 mm²and/or at most 50 mm².

Beneficially, the aperture has a large clear aperture size, which is particularly beneficial, when provided in combination with the protrusions and embodiments thereof.

According to an embodiment, which can be combined with other embodiments, the proximity-electrode 140 is aligned with at least one detector (in particular a backscattered electron detector, i.e. BSE detector 134, and/or energy-dispersive X-ray spectroscopy detector, i.e. EDX detector) configured to detect signal charged particles emanating from the sample and traversing through the aperture 340 including through an outside of a central circle of the aperture 340.

In an example, backscattered charged particles, such as backscattered electrons, are typically fast and therefore less susceptible to an accelerating field, such as an accelerating field of a proximity-electrode. Accordingly, backscattered charged particles, including backscattered electrons, spread or emanate across a wide angle, far away from the optical axis. Therefore, a proximity-electrode with a larger opening is particularly beneficial for working with a backscattered charged particle detector (e.g. backscattered electron detector) arranged for detecting the signal charged particles (e.g. backscattered charged particles/backscattered electrons).

According to an embodiment, which can be combined with other embodiments, one, or in particular both, of the proximity-electrode and the detector is/are arranged such that signal charged particles traversing through the aperture of the proximity-electrode including through an outside of a central circle of the aperture impinge on the detector, in particular, impinge directly on the detector and/or impinge on the detector without an electrode therebetween and/or impinge on the detector without an electrode between the proximity-electrode and the detector. In a particular example, the detector is a backscattered charged particle detector or a backscattered electron detector.

It may be understood that the central circle is within a plane of the aperture 340. It may be understood that a center of the central circle is aligned with a center of the aperture 340 or a central axis of the proximity-electrode 140. It may be understood that the central circle is clear of the protrusions 310 or absent of the protrusions 310. It may be understood that the central circle extends up to an end or a tip of one, preferably all, of the protrusions 310.

Beneficially, more signal charged particles and wider-angle signal charged particles can traverse the proximity-electrode and be collected/detected without undesirably increasing field penetration from the column above.

According to an embodiment, which can be combined with other aspects and embodiments (for example, the protrusions 310 extending radially into the aperture 340), all areas of the aperture 340 are contiguous with each other in a plane of the aperture 340. Beneficially, shadowing is minimized for a large aperture area, allowing improved signal charged particle detection and/or imaging.

According to an embodiment, which can be combined with other embodiments, an unsupported tip or end 330 of each protrusion 310 has a bulbous shape (which may be understood as having ends with enlarged radius relative to the radius at the middle or stem 320 of the respective protrusion), and/or is adapted to decrease a surface electric field at the unsupported tip or end 330.

According to an embodiment, which can be combined with other embodiments described herein, a radius or width of the tip or end 330 of (each of) the protrusions is at least as large, preferably larger, than a radius or width of a middle or stem 320 of the respective protrusion 310.

According to an embodiment, which can be combined with other embodiments described herein, a radius or width of the tip or end 330 of (each of) the protrusions is at most twice of a radius or width of a middle or stem 320 of the respective protrusion 310.

According to some embodiments, which can be combined with other embodiments described herein, the (unsupported and/or free) tip or end 330 of one or more, preferably all, protrusions 310 has respectively a bulbous shape or a radius larger than a radius at a middle or stem 320 of the respective protrusion 310.

According to some embodiments, which can be combined with other embodiments described herein, the (unsupported and/or free) tip or end 330 of one or more, preferably all, protrusions 310 is respectively adapted to have a reduced/low surface electric field, in particular at the (free and/or unsupported) tip or end 330.

Beneficially, protrusion ends are rounded, and a proximity-electrode with reduced peak surface electric field and low field penetrating through the proximity-electrode thus low proximity-electrode voltage is attained.

It may be understood that a protrusion 310 has (only) one (unsupported and/or free) tip or end 330. It may be understood that an unsupported and/or free tip or end 330 of a protrusion 310 is arranged at an opposite end to a base or supported end of the protrusion 310. It may be understood that a protrusion 310 is supported or cantilevered at a base of the protrusion 310. It may be understood that each of the one or more protrusions is supported by or cantilevered from the body 300 of the proximity-electrode 140.

Aspects, embodiments and examples of the retarding field device are described as follows.

FIG. 8 shows a retarding field device including a proximity-electrode according to aspects and embodiments described herein.

According to an aspect, a retarding field device, for retarding the primary charged particle beam before the primary charged particle beam impinges on a sample 150, includes an objective lens 120 and a proximity-electrode 140 arranged downstream of (a principal plane of) the objective lens 120.

It may be understood that the retarding field device is configured to reduce energy of the primary charged particle beam in the column to a landing energy for landing on the sample 150. The retarding field device may be configured to decelerate the primary charged particle beam and accelerate signal charged particles. In an example, the objective lens 120 and the proximity-electrode 140 may be configured, in combination, to focus the primary charged particle beam.

According to an embodiment, which can be combined with other aspects and embodiments, the proximity-electrode 140 is arranged proximate to the objective lens 120 or within an effective field of the objective lens 120.

According to an embodiment, which can be combined with other aspects and embodiments, the proximity-electrode 140 is adjacent to or proximate to the sample 150 and/or sample stage. According to an embodiment, the proximity-electrode 140 is configured to control or provide control of an extraction field, in particular in a space between the proximity-electrode 140 and the sample 150 or sample stage.

The extraction field may be understood as a field for extracting signal charged particles from the sample 150 and/or to accelerate signal charged particles from the sample 150. The extraction field may be controlled or provided by the proximity-electrode 140. It may be understood that collection of signal charged particles can be controlled by controlling the extraction field.

The proximity-electrode 140 may be configured to control the extraction field strength for extracting signal charged particles. It may be understood that the extraction field in the extraction region between the sample and the proximity-electrode can be controlled by applying a predetermined electric potential U_prox, 230, to the proximity-electrode 140.

According to an embodiment, which can be combined with other aspects and embodiments, the proximity-electrode 140 is arranged or configured to be a last element of a retarding field device or of a charged particle beam device in a direction of a primary charged particle beam before the primary charged particle beam impinges on a sample 150.

The proximity-electrode 140 may be arranged adjacent to the sample 150 and/or without electrodes and/or elements between the proximity-electrode 140 and the sample 150. It may be understood that a distance between the proximity-electrode 140 and the sample 150 or the sample stage is smaller than a distance between the objective lens 120 and the sample 150 or the sample stage.

In an example, a distance between the proximity-electrode 140 and the sample 150 or sample stage, in particular operative distance or working distance or distance during operation, is 10 mm or less, preferably 6 mm or less, more preferably 4 mm or less, and most preferably 2 mm or less.

Beneficially, a small distance between the proximity-electrode 140 and the sample 150 allows large-angle signal charged particles to be collected through the aperture of the proximity-electrode 140.

According to an embodiment, which can be combined with other aspects and embodiments, the proximity-electrode 140 may be configured to decelerate the primary charged particle beam, in particular as a (most downstream) component or electrode of the retarding field device.

According to an embodiment, which can be combined with other aspects and embodiments, the proximity-electrode 140 is adapted to be at a more negative potential than a column potential, U_col210.

In an example, the proximity-electrode 140 is at a potential, U_prox, 230 such that a potential difference between the potential of the proximity-electrode, U_prox, 230 and a potential of the column of the charged particle beam device, U_col210, a potential of the first detector, U_det, and/or a potential the objective lens, U_objis adapted to decelerate the primary charged particle beam before impingement on the sample.

Beneficially, a retarding field device is provided.

In an example, the proximity-electrode 140 is at a potential, U_prox, 230 such that the proximity-electrode is at a more negative potential than a potential of a column of the charged particle beam device, U_col210 (e.g. a potential of the first detector, U_det, or the objective lens, U_obj).

In an example, a retarding field device provides a potential difference between the sample 150 (sample potential, U_sample240) and a column of the charged particle beam device (column potential, U_col210), for example, of 5 keV or more, 15 keV or more, or 30 keV or more, and/or 100 keV or less, 80 keV or less, or 60 keV or less.

It may be understood that (the aperture of) the proximity-electrode is adapted for passage of both a primary charged particle beam and signal charged particles. It may be understood that the primary charged particle beam and signal particles propagate, in different, for example (substantially) opposite directions, through the proximity-electrode, in particular through the aperture.

It may be understood that the proximity-electrode 140 is configured to allow the primary charged particle beam to traverse the proximity-electrode through an aperture of the proximity-electrode 140 to impinge on a sample 150.

It may be understood that the proximity-electrode 140 is adapted to allow signal particles emanating from the sample to traverse the proximity-electrode 140 (through the aperture of the proximity-electrode 140).

According to embodiments, the size of the aperture (clear aperture size) of the proximity-electrode 140 is 5 mm²or more, preferably 10 mm²or more, more preferably 15 mm²or more and most preferably 20 mm²or more.

According to embodiments, a diameter or (in-plane) width of the aperture of the proximity-electrode 140 is at least 5 times a distance between the proximity-electrode 140 and the sample 150 or sample stage, or at least 5 times a height of a space between the proximity-electrode 140 and the sample 150 or sample stage.

Beneficially, it is provided a proximity-electrode with a large aperture which allows more signal charged particles through to be collected.

The proximity-electrode 140 may be configured to enable traversal of signal charged particles emitted at an angle of 5 degrees or more, preferably 10 degrees or more, or most preferably 15 degrees or more. The angle of the signal charged particle emitted may be understood as being with respect to the optical axis of the charged particle beam device and/or to the axis of the proximity-electrode 140.

According to embodiments, the size of the aperture of the proximity-electrode 140 and the distance between the proximity-electrode 140 are such that signal charged particles from the sample 150, emitted at an angle of 5 degrees or more, preferably 10 degrees or more, or more preferably 15 degrees or more, passes through the aperture of the proximity-electrode 140.

Aspects, embodiments and examples of a charged particle beam device are described as follows.

FIG. 9 shows a charged particle beam device according to aspects and embodiments described herein.

According to an aspect, a charged particle beam device 100, for at least one of imaging and inspecting a sample, includes a beam emitter 110 for emitting a primary charged particle beam; and a retarding field device for retarding the primary charged particle beam before the primary charged particle beam impinges on the sample 150, the retarding field device including an objective lens 120 and a proximity-electrode 140 arranged downstream of (a principal plane of) the objective lens 120; wherein the charged particle beam device 100 is adapted for guiding the primary charged particle beam along an optical axis 160 to the sample 150 for generating signal charged particles from the sample 150.

The beam emitter 110 for emitting a primary charged particle beam may be a charged particle source, such as a cold field emitter (CFE) or a thermal field emitter (TFE) (e.g. a Schottky emitter). The beam emitter 110 may be a high current and/or high brightness source. A high current source may be understood as a source configured to produce at least 5 μA in 100 mrad.

The charged particle beam device may include a charged particle suppressor (not shown), a condenser lens 112, and/or deflectors 114 (which may be beam alignment deflectors and/or configured for aligning the primary charged particle beam to a beam limiting aperture 116. The beam limiting aperture 116 may be arranged between the beam emitter 110 and the objective lens 120. The beam limiting aperture 116 may be arranged to separate a first chamber that includes the beam emitter 110 from a further chamber or further chambers, e.g. a second chamber or a second chamber including the objective lens 120.

It may be understood that the objective lens 120 is configured to focus the primary charged particle beam on the sample 150. In an example, the objective lens 120 includes an upper pole piece and a lower pole piece and a coil forming a magnetic lens component of the objective lens 120 (shown in FIG. 8). The objective lens 120 may include one or more electrodes forming an electrostatic lens component of the objective lens. The magnetic lens component and the electrostatic lens component may overlap to form a compound objective lens.

In an example, the charged particle beam device includes a column. The column may be at ground potential. In an example, when the column is at ground potential, detection with the first and/or second detector, in particular with one or more semiconductor detectors, such as pin diodes, can be practicable, since both the detector and detector electronics can be set at ground potential.

It may be understood that the charged particle beam device 100 is configured to guide the primary charged particle beam through a column of the charged particle beam device 100. The interior of the column may be understood to be evacuated and/or at sub-atmospheric pressure, for example at a pressure of 1 mbar or less, 10⁻⁵mbar or less, or even 10⁻⁸mbar or less (ultra-high vacuum). In an embodiment, the charged particle beam device includes a vacuum housing. The beam emitter and the objective lens may be arranged inside the vacuum housing of the charged particle beam device.

In an example, the charged particle beam device 100 may include a scan deflector 122 (shown in FIG. 8). The scan deflector 122 may be configured for scanning the primary charged particle beam over (a surface of) the sample 150.

It may be understood that an axis of the proximity-electrode 140, in particular of the aperture of the proximity-electrode 140, is aligned with an optical axis 160 of the charged particle beam device 100, with the primary charged particle beam and/or with an axis of the objective lens 120. In an example, the optical axis 160 of the charged particle beam device 100 and the axis of the proximity-electrode 140, in particular of the aperture of the proximity-electrode 140, is collinear and/or coincident.

In an example, the charged particle beam device 100 includes one or more detectors configured to detect signal charged particles emanating from the sample 150 and traversing through (the aperture of) the proximity-electrode 140, preferably including through the outside of the central circle of the aperture of the proximity-electrode 140, the central circle being clear of protrusions and extending up to an end of a protrusion of the proximity-electrode 140.

In an example, the proximity-electrode 140 is aligned with at least one of the one or more detectors, e.g. with a BSE detector 134 (shown in FIG. 8).

According to an embodiment, which can be combined with other aspects and embodiments, the proximity-electrode 140 is arranged to be a last element of a charged particle beam device 100 in a direction of a primary charged particle beam before the primary charged particle beam impinges on a sample 150. Beneficially, the proximity-electrode is adjacent or proximate to the sample, and facilitates suitable impingement energy of the primary charged particle beam and extraction of signal charged particles.

In an example, the proximity-electrode 140 is arranged adjacent to or at a front end of the vacuum housing of the charged particle beam device 100 and/or protrudes into a sample chamber where a sample 150 and/or a sample stage 152 is arranged. In an example, the sample chamber may be configured for a sub-atmospheric pressure, e.g., a high vacuum. In an example, the vacuum housing of the charged particle beam device 100 may be configured for an ultra-high vacuum and/or for a higher vacuum or lower pressure than the sample chamber.

The charged particle beam device 100 may include a sample stage 152 configured for supporting a sample 150. The sample stage 152 may have a support surface, in particular extending in an x-y-plane. The sample 150 may be placed on a sample stage 152 of the charged particle beam device 100.

It may be understood that on impingement of the primary charged particle beam on the sample 150, signal charged particles, for example, secondary (SE) and/or backscattered charged particles (BSE), which may be understood to be detectable by at least one of the one or more detectors (e.g. BSE detector 134, SE detector 132), are emitted or emanate from the sample 150.

According to an embodiment, which can be combined with other aspects and embodiments, the charged particle beam device 100 includes a first detector, preferably configured to detect backscattered signal charged particles, i.e. a BSE detector 134. The first detector may be arranged between the objective lens 120 and a sample 150 or sample stage 152. The first detector may be preferably arranged between the proximity-electrode 140 and the objective lens 120. In an example, the first detector is a semiconductor detector, for example a PIN diode.

It may be understood that signal charged particles, for example backscattered electrons, traversing the proximity-electrode 140 can be accelerated towards a first detector, e.g. a BSE detector 134, such that detection is efficient. In an example, by setting the first detector at a respective potential, the first detector may function as an acceleration electrode to accelerate signal charged particles.

It may be understood that accelerating signal charged particles, in particular backscattered charged particles, is particularly beneficial for detecting signal charged particles at low landing energy settings. This is beneficial at landing energies below 10 keV, below 3 keV or even below 1 keV, and for detecting backscattered electrons that lose energy travelling through the sample, for example when being backscattered from deeper within the sample or from a deep trench or features with a high-aspect ratio.

The first detector may be a multi-channel backscattered electron detector, preferably including a plurality of detection segments, the signals of which can be individually processed, e.g., individually mixed and/or combined. The signal(s) from the first detector, in particular from the plurality of detection segments, may be combined for compositional imaging and/or individually processed for improving the topographic contrast.

The first detector may be an in-lens detector. The first detector may have an annular detection surface. An axis of the first detector may be collinear or coincident with the optical axis of the charged particle beam device and/or with the axis of the proximity-electrode 140. In some embodiments, the first detector is an in-lens detector with a hole that allows a passage of the primary charged particle beam and with an annular detection surface surrounding the hole.

According to an embodiment, which can be combined with other aspects and embodiments, the charged particle beam device 100 includes one or more of at least one of electrodes, deflectors 114, and/or lenses (e.g. condenser lens 112 and/or objective lens 120), for guiding the primary charged particle beam along an optical axis to the sample for generating signal charged particles from the sample 150. The charged particle beam device 100 may be configured to image and/or inspect a sample 150 based on signal charged particles emanating from the sample 150.

The charged particle beam device 100 may include a beam separator 130 configured to separate the primary charged particle beam from signal charged particles, preferably arranged between the beam emitter 110 and the objective lens 120. The beam separator 130 may include at least one magnetic deflector, such that the signal charged particles are deflected away from the optical axis 160 of the charged particle beam device 100. In an example, the beam separator is a Wien filter.

The charged particle beam device 100 may include a second detector (e.g. SE detector 132) configured for detecting signal charged particles, preferably secondary signal charged particles (e.g. secondary electrons). The second detector may be configured to detect signal charged particles separated from the primary charged particle beam by the beam separator 130. The second detector may be arranged between the objective lens 120 and the beam emitter 110. In an example, the second detector is a secondary electron detector.

FIG. 10 shows the relative primary beam spot sizes for various beam currents for a charged particle beam device with a proximity-electrode according to the first design 1010 and with a proximity-electrode according to the baseline design 1020. As shown, a charged particle beam device having a proximity-electrode having protrusions has substantially similar primary charged particle beam spot size to a primary charged particle beam device having a proximity-electrode without protrusions. Accordingly, a proximity-electrode according to embodiments and examples as described herein may provide corresponding benefits without distorting the primary charged particle beam.

Aspects, embodiments and examples of a method for imaging and/or inspection of a sample are described in the following.

FIG. 11 illustrates a method for imaging and/or inspection of a sample using a charged particle beam device having a proximity-electrode according to aspects and embodiments described herein.

According to an aspect, a method for imaging and/or inspection of a sample 150 using a charged particle beam device 100 having the proximity-electrode 140 may include emitting a primary charged particle beam 1110; guiding the primary charged particle beam through a column of the charged particle beam device 1120; and focusing 1130 and retarding the primary charged particle beam with the retarding field device 1140.

According to embodiments, which can be combined with other embodiments describe herein, the proximity-electrode 140 includes a central circle within a plane of the aperture of the proximity-electrode 140 that is clear of the protrusions, and the method includes guiding the primary charged particle beam through the aperture, in particular, (substantially or wholly) through the central circle.

According to some embodiments, the proximity-electrode 140 includes a central circle within a plane of the aperture of the proximity-electrode 140 that is clear of the protrusions, and the method includes detecting signal charged particles traversing through (the aperture of) the proximity-electrode 140, preferably including through the outside of the central circle of the aperture of the proximity-electrode 140.

According to some embodiments, the proximity-electrode 140 is arranged to be a last element of a charged particle beam device in a direction of a primary charged particle beam before the primary charged particle beam impinges on a sample, and the method includes setting the proximity-electrode including/having the protrusions, at a potential adapted to reduce a penetration of a column field through the proximity-electrode and onto the sample.

In an example, the phrase ‘at a potential adapted to reduce a penetration of a column field’ may be understood as meaning: wherein the penetration of the column field through the proximity-electrode, when the proximity-electrode is set at said potential, is less in comparison to a penetration of the column field, when the proximity-electrode is set at a potential equal to a potential of the column.

The charged particle beam device may be for imaging and/or inspecting a sample, for example for at least one of critical dimension measurement, defect review, charged particle beam mask inspection, and metrology and inspection processes such as charged particle beam metrology and hotspot inspection, and charged particle beam wafer inspection.

Further, imaging and/or inspection of a sample may be understood as the imaging and/or inspection of 3D structures, for example semiconductor samples such as wafers, and/or features such as FinFETs and NANDs.

In the present disclosure, proximity-electrode, charged particle beam device, components thereof and methods in connection therewith exemplarily refer to electrons without limitation. The term electrons particularly encompass secondary electrons and/or backscattered electrons, specifically both secondary and backscattered electrons (SEs and BSEs). However, it is to be understood that aspects, embodiments and examples described herein can be applied to other corpuscles such as secondary and/or backscattered charged particles in the form of positive or negative ions in order to obtain a sample image or inspection result. Accordingly, in aspects, embodiments and examples described herein, proximity-electrode, charged particle beam device, components thereof and methods in connection therewith are not limited to electrons and may refer to charged particles.