U.S. patent application number 17/302031 was filed with the patent office on 2022-04-07 for apparatus of charged-particle beam such as electron microscope comprising co-condensers for continuous image resolution tuning.
This patent application is currently assigned to BORRIES PTE. LTD.. The applicant listed for this patent is Xiaoming Chen, Zhongwei Chen, Liang-Fu Fan, Daniel Tang. Invention is credited to Xiaoming Chen, Zhongwei Chen, Liang-Fu Fan, Daniel Tang.
Application Number | 20220108865 17/302031 |
Document ID | / |
Family ID | |
Filed Date | 2022-04-07 |
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United States Patent
Application |
20220108865 |
Kind Code |
A1 |
Chen; Zhongwei ; et
al. |
April 7, 2022 |
APPARATUS OF CHARGED-PARTICLE BEAM SUCH AS ELECTRON MICROSCOPE
COMPRISING CO-CONDENSERS FOR CONTINUOUS IMAGE RESOLUTION TUNING
Abstract
The present invention provides an apparatus of charged-particle
beam such as an electron microscope with co-condensers. A source of
charged particles is configured to emit a beam of charged
particles, and the co-condensers including two or more magnetic
condensers are configured to coherently focus the beam to a single
crossover spot. The invention exhibits numerous technical merits
such as continuous image resolution tuning, and automatic switching
between multiple resolutions, among others.
Inventors: |
Chen; Zhongwei; (Los Altos
Hills, CA) ; Chen; Xiaoming; (Sunnyvale, CA) ;
Tang; Daniel; (Fremont, CA) ; Fan; Liang-Fu;
(Fremont, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Chen; Zhongwei
Chen; Xiaoming
Tang; Daniel
Fan; Liang-Fu |
Los Altos Hills
Sunnyvale
Fremont
Fremont |
CA
CA
CA
CA |
US
US
US
US |
|
|
Assignee: |
BORRIES PTE. LTD.
Singapore
SG
|
Appl. No.: |
17/302031 |
Filed: |
April 21, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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63087238 |
Oct 4, 2020 |
|
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International
Class: |
H01J 37/141 20060101
H01J037/141; H01J 37/147 20060101 H01J037/147; H01J 37/20 20060101
H01J037/20; H01J 37/28 20060101 H01J037/28 |
Claims
1. An apparatus of charged-particle beam comprising: a source of
charged particles configured to emit a beam of charged particles,
and co-condensers, wherein the term "co-condensers" is defined as
two or more magnetic condensers configured to coherently focus the
beam to a single crossover spot F, wherein said two or more
magnetic condensers includes only two magnetic condensers
configured to coherently focus the beam to a single crossover spot
F, wherein said only two magnetic condensers include a distal
magnetic condenser which is distal to the source, and a proximal
magnetic condenser that is located between the source and the
distal magnetic condenser, wherein the proximal magnetic condenser
comprises a magnetic coil driven by a coil current I1, wherein the
distal magnetic condenser comprises a magnetic coil driven by a
coil current I2, wherein a size A of the crossover spot F Is
increased by increasing coil current I1 and/or decreasing coil
current I2, wherein the size A of the crossover spot F is decreased
by decreasing coil current I1 and/or increasing coil current I2,
and wherein the size A of the crossover spot F is minimized when
coil current I1 reaches its minimal value and coil current I2
reaches its maximal value, and the size A is maximized when coil
current I2 reaches its minimal value and I1 reaches its maximal
value.
2. (canceled)
3. The apparatus according to claim 1, wherein the beam does not
have a crossover spot between any two of said two or more magnetic
condensers, or wherein said single crossover spot F remains
stationary relative to the source of charged particles.
4-6. (canceled)
7. The apparatus according to claim 1, wherein I1>0, and
I2>0.
8-9. (canceled)
10. The apparatus according to claim 1, wherein the maximized size
A is bigger than the size of the source.
11. The apparatus according to claim 1, further comprising a
magnetic objective lens and a deflection system, both of which are
downstream with respect to the single crossover spot F.
12. The apparatus according to claim 11, wherein the deflection
system includes a macroscopic deflection sub-system and a
microscopic deflection sub-system.
13. The apparatus according to claim 12, wherein the macroscopic
deflection sub-system causes the beam to scan across a large field
of view (FOV) on a specimen plane, and wherein the microscopic
sub-deflection system causes the beam to scan across a small FOV
within said large FOV.
14. The apparatus according to claim 13, wherein the position of
the small FOV within the large FOV is controlled by the macroscopic
deflection sub-system.
15. The apparatus according to claim 14, wherein, after the
position of the small FOV within the large FOV is fixed by the
macroscopic deflection sub-system, deflecting parameter(s) of the
macroscopic deflection sub-system remain unchanged while deflecting
parameter(s) of the microscopic deflection sub-system is/are varied
to cause the beam to scan across the small FOV.
16. The apparatus according to claim 15, wherein, when the beam
scans across the large FOV, the spot F has a size A1, and wherein,
when the beam scans across the small FOV, the spot F has a size A2,
and A2<A1.
17. The apparatus according to claim 12, wherein the macroscopic
deflection sub-system comprises an upper deflector and a lower
deflector.
18. The apparatus according to claim 17, wherein the microscopic
deflection sub-system is located between the upper deflector and
the lower deflector of the macroscopic deflection system.
19. The apparatus according to claim 17, wherein the microscopic
deflection sub-system includes an upper deflector and a lower
deflector.
20. The apparatus according to claim 18, further comprising a
specimen holder which is downstream with respect to the lower
deflector of the macroscopic deflection sub-system, wherein the
specimen holder remains stationary relative to the source of
charged particles, no matter the beam is scanning across a given
large FOV or scanning across the small FOVs within said given large
FOV.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application expressly claims the benefit under 35
U.S.C. Section 119(e) and Article 4 of the Stockholm Act of the
Paris Convention for the Protection of Industrial Property of U.S.
Provisional Patent Application No. 63/087,238, filed Oct. 4, 2020,
entitled "Several Designs for Apparatus of Charged-Particle Beam
and Methods Thereof," the entire disclosure of which is hereby
incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention generally relates to an apparatus of
charged-particle beam (e.g. electron beam) comprising two or more
co-condensers for continuous image resolution tuning. Although the
invention will be illustrated, explained, and exemplified by
electron microscopes with auto multiple resolution switch, it
should be appreciated that the present invention can also be
applied to other fields, for example, electron beam recorder,
electron beam lithography system, and the like.
BACKGROUND OF THE INVENTION
[0003] Apparatuses of charged-particle beam such as transmission
electron microscope (TEM) or scanning transmission electron
microscope (STEM) are widely used in fields of medical diagnosis,
biological research, material analysis, and semiconductor
inspection etc. With their high-resolution image technique, TEM and
STEM are used as a particularly important diagnostic tool to screen
virus, human tissues at high magnification (the ultrastructural
level) or material analysis, often in conjunction with other
methods, particularly light microscopy, immunofluorescence
techniques and PCR etc.
[0004] For example, TEM/STEM has great potential for diagnostic
purposes when it (1) provides useful (complementary) information in
the context of a carefully considered differential diagnosis; (2)
provides an `improved` diagnosis that results in better treatment
strategies and; (3) is time & cost effective in respect to
alternative techniques. For diagnostic purposes, solid tissues or
virus sample can be prepared for TEM/STEM in the same way as other
biological tissues. The samples are fixed in glutaraldehyde and
osmium tetroxide then dehydrated and embedded in epoxy resin. The
ultrathin sections may be collected on 3 mm copper (mesh) grids and
stained with uranyl acetate and lead citrate to make the contents
of the tissue or virus electron dense (and thus visible in the
electron microscope).
[0005] Current TEM/STEM samples are collected on 3 mm copper (mesh)
grids and are loaded into TEM/STEM system manually. Then operator
needs to manually operate TEM/STEM machine to adjust TEM/STEM
machine to get focused image and manually select interesting
location to take image. After taking the image, the operator must
manually analyze the image content to acquire the result. So
TEM/STEM operation need well trained expert to operate it and it is
also very time-consuming.
[0006] For example, current EMs can acquire a scanning image with
an extremely high resolution (e.g. 1 nm). However, the EMs have
different field of view (FOV) sizes under different resolutions.
For example, a typical big FOV size is about 100 um.times.100 um
under 10 nm resolution, but the FOV size will be reduced to 10
um.times.10 um under 1 nm resolution. Therefore, when a user finds
a pattern of interesting (POI) under 10 nm resolution with the EM,
and he/she wants to zoom into the POI for further examination with
1 nm resolution, the user would have to mechanically move the
sample stage so the sample could be repositioned to the center of a
smaller FOV. However, mechanical repositioning of the sample to
different POIs locations has a drawback of low efficiency, because
it slows down the entire procedure of microscopic examining of the
sample
[0007] Advantageously, the present invention provides a solution to
overcome the drawback in the current electron microscopes.
SUMMARY OF THE INVENTION
[0008] One aspect of the present invention provides an apparatus of
charged-particle beam comprising (1) a source of charged particles
configured to emit a beam of charged particles, and (2)
co-condensers. The term "co-condensers" is defined as two or more
magnetic condensers configured to coherently focus the beam to a
single crossover spot F.
[0009] The above features and advantages and other features and
advantages of the present invention are readily apparent from the
following detailed description of the best modes for carrying out
the invention when taken in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0010] The present invention is illustrated by way of example, and
not by way of limitation, in the figures of the accompanying
drawings and in which like reference numerals refer to similar
elements. All the figures are schematic and generally only show
parts which are necessary in order to elucidate the invention. For
simplicity and clarity of illustration, elements shown in the
figures and discussed below have not necessarily been drawn to
scale. Well-known structures and devices are shown in simplified
form, omitted, or merely suggested, in order to avoid unnecessarily
obscuring the present invention.
[0011] FIG. 1 schematically illustrates how co-condensers are
formed in accordance with an exemplary embodiment of the present
invention.
[0012] FIG. 2 shows two co-condensers with magnetic coils in
accordance with an exemplary embodiment of the present
invention.
[0013] FIG. 3 illustrates an apparatus of charged-particle beam
with a magnetic objective lens and a deflection system in
accordance with an exemplary embodiment of the present
invention.
[0014] FIG. 4 demonstrates a single large FOV on the specimen plane
of the apparatus in accordance with an exemplary embodiment of the
present invention.
[0015] FIG. 5 demonstrates multiple large FOVs on the specimen
plane of the apparatus in accordance with an exemplary embodiment
of the present invention.
[0016] FIG. 6 illustrates a macroscopic deflection sub-system alone
causing the beam to scan across a large FOV in accordance with an
exemplary embodiment of the present invention.
[0017] FIG. 7 illustrates a microscopic deflection sub-system
causing the beam to scan across a small FOV in accordance with an
exemplary embodiment of the present invention.
[0018] FIG. 8 schematically illustrates the configuration of a
macroscopic deflection sub-system in accordance with an exemplary
embodiment of the present invention.
[0019] FIG. 9 schematically illustrates the configuration of a
microscopic deflection sub-system in accordance with an exemplary
embodiment of the present invention.
[0020] FIG. 10 shows an apparatus of charged-particle beam with two
co-condensers in accordance with an exemplary embodiment of the
present invention.
[0021] FIG. 11 shows the image of a biological sample in a large
FOV with low resolution and a small FOV with high resolution in
accordance with an exemplary embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] In the following description, for the purposes of
explanation, numerous specific details are set forth in order to
provide a thorough understanding of the present invention. It is
apparent, however, to one skilled in the art that the present
invention may be practiced without these specific details or with
an equivalent arrangement.
[0023] Where a numerical range is disclosed herein, unless
otherwise specified, such range is continuous, inclusive of both
the minimum and maximum values of the range as well as every value
between such minimum and maximum values. Still further, where a
range refers to integers, only the integers from the minimum value
to and including the maximum value of such range are included. In
addition, where multiple ranges are provided to describe a feature
or characteristic, such ranges can be combined.
[0024] It is also to be understood that the terminology used herein
is for the purpose of describing particular embodiments only, and
it is not intended to limit the scope of the invention. For
example, when an element is referred to as being "on", "connected
to", or "coupled to" another element, it can be directly on,
connected or coupled to the other element or intervening elements
may be present. In contrast, when an element is referred to as
being "directly on", "directly connected to", or "directly coupled
to" another element, there are no intervening elements present.
[0025] In an apparatus of charged-particle beam such as an electron
microscope, the manipulation of an electron beam is performed using
two physical effects. The interaction of electrons with a magnetic
field will cause electrons to move according to the left-hand rule,
thus allowing for electromagnets to manipulate the electron beam.
The use of magnetic fields allows for the formation of a magnetic
lens of variable focusing power, and the lens shape is determined
by the distribution of magnetic flux. Electrostatic fields can
cause the electrons to be deflected through a constant angle.
Coupling of two deflections in opposing directions with a small
intermediate gap allows for the formation of a shift in the beam
path. From these two effects, as well as the use of an electron
imaging system, sufficient control over the beam path is made
possible. The lenses in the beam path can be enabled, tuned, and
disabled entirely and simply via rapid electrical switching, the
speed of which is only limited by effects such as the magnetic
hysteresis.
[0026] In an apparatus 1 of charged-particle beam as shown in FIG.
1, a source 2 of charged particles is configured to emit a beam of
charged particles. The source 2 may be for example an electron gun
with a tungsten filament or a lanthanum hexaboride (LaB.sub.6). In
panel (a), a magnetic condenser 3 alone can focus the beam to a
crossover spot F1. The beam is expanded after a crossover spot. In
panel (b), another magnetic condenser 4 is placed between magnetic
condenser 3 and crossover spot F1, and the beam is now focused to a
new crossover spot F2 that is closer to source 2 than spot F1. In
panel (c), a third magnetic condenser 5 is placed between magnetic
condenser 4 and crossover spot F2, and the beam is again focused to
another new crossover spot F3 that is even closer to source 2 than
spot F2.
[0027] In the present invention, the term "co-condensers" is
defined as two or more magnetic condensers configured to coherently
focus the beam to a single crossover spot F. For example, magnetic
condensers 3 and 4 in panel (b) coherently focus the beam to a
single crossover spot F2, and they may be called a set of
co-condensers. Magnetic condensers 3, 4 and 5 in panel (c)
coherently focus the beam to a single crossover spot F3, and they
may also be called a set of co-condensers. As shown in FIG. 1, the
beam does not have any crossover spot between any two of the two or
more magnetic condensers within a set of co-condensers.
[0028] The crossover spot F may be movable or immovable. In some
embodiments of the invention, the single crossover spot F is so
controlled that it remains stationary or immovable relative to the
source 2 of charged particles. For example, crossover spot F2 may
be kept stationary relative to the source 2, i.e. the distance DO
between spot F2 and source 2 remains unchanged. By the same token,
crossover spot F3 may be kept stationary relative to the source 2,
i.e. the distance DO between spot F3 and source 2 remains
unchanged.
[0029] While the single crossover spot F remains immovable relative
to the source 2 of charged particles, the size A of the beam at
crossover spot F (i.e. the cross-sectional area of the beam at F)
may be so controlled to have a desired value. Preferably, size A
may be tuned/adjusted by concertedly tuning/adjusting the
individual condensing capacity of the two or more magnetic
condensers within a set of co-condensers. For example, the
condensing capacity of condenser 3 and that of condenser 4 may be
individually but concertedly tuned/adjusted so that not only the
single crossover spot F2 is fixed relative to the source 2, but
also the size A of the beam at crossover spot F2 is controlled to
have a value as desired. Likewise, the condensing capacities of two
or more condensers 3, 4 and 5 may be individually but concertedly
tuned/adjusted so that not only the single crossover spot F3 is
fixed relative to the source 2, but also the size A of the beam at
crossover spot F3 is controlled to have a value as desired. The two
or more co-condensers are therefore configured to coherently focus
the beam to the same cross-over point with different magnification
rates.
[0030] Although the apparatus 1 may include one, two or more sets
of co-condensers, in some preferred embodiments of the invention,
the apparatus 1 includes only one set of co-condensers with only
two magnetic condensers configured to coherently focus the beam to
a single crossover spot F. For example, the apparatus 1 may include
only one set of co-condensers as shown in Panel (b) of FIG. 1 with
only two magnetic condensers (3, 4) configured to coherently focus
the beam to a single crossover spot F2.
[0031] Referring to FIG. 2, the only two magnetic condensers (3, 4)
include a distal magnetic condenser 4 which is distal to the source
2, and a proximal magnetic condenser 3 that is located between the
source 2 and the distal magnetic condenser 4. The proximal magnetic
condenser 3 comprises a magnetic coil 3C driven by a coil current
I1; and the distal magnetic condenser 4 comprises a magnetic coil
4C driven by a coil current I2. Generally, both coil currents I1
and I2 are greater than 0 (>0).
[0032] In preferred embodiments of the invention, coil currents I1
and I2 are configured to position single crossover spot F2 at a
fixed position, i.e. maintain a predetermined distance DO from
source 2. With the "Fixed F2" condition being met, the size A of
the crossover spot F2 may be increased by increasing coil current
I1 and/or decreasing coil current I2; and decreased by decreasing
coil current I1 and/or increasing coil current I2. The size A of
the crossover spot F2 will be minimized when coil current I1
reaches its minimal value while coil current I2 reaches its maximal
value. The size A is maximized when coil current I2 reaches its
minimal value while I1 reaches its maximal value. There is no
special limitation on the maximized size A, it may be smaller than,
equal to, or bigger than the size of the source 2.
[0033] In various exemplary embodiments as shown in FIG. 3, the
apparatus of charged-particle beam according to the invention may
include a magnetic objective lens 6 (as shown in FIGS. 8-10) and a
deflection system 7, which are downstream with respect to the
single crossover spot F. (e.g. F2). Although electron lenses may
operate electrostatically or magnetically, most electron lenses use
electromagnetic coils to generate a convex lens. The field produced
for the lens is typically radially symmetrical, as deviation from
the radial symmetry of the magnetic lens causes aberrations such as
astigmatism and worsens spherical and chromatic aberration. For
example, a quadrupole lens is an arrangement of electromagnetic
coils at the vertices of the square, enabling the generation of a
lensing magnetic fields, the hexapole configuration simply enhances
the lens symmetry by using six, rather than four coils. Electron
lenses may be manufactured from iron, iron-cobalt or nickel cobalt
alloys, such as permalloy, due to their good magnetic properties,
such as magnetic saturation, hysteresis and permeability. It should
be appreciated that the objective lens 6 may be an electromagnetic
lens or an electrostatic lens.
[0034] Objective lens 6 allows for electron beam convergence, with
the angle of convergence as a variable parameter. The magnification
may be simply changed by modifying the amount of current that flows
through the coil of lenses. Lens 6 may include yoke, magnetic coil,
poles, pole piece, and external control circuitry. An
electromagnetic lens may include an upper pole piece and a lower
pole piece. The pole piece must be manufactured in a very
symmetrical manner, as this provides the boundary conditions for
the magnetic field that forms the lens. Imperfections in the
manufacture of the pole piece can induce severe distortions in the
magnetic field symmetry, which induce distortions that will
ultimately limit the lenses' ability to reproduce the object plane.
The exact dimensions of the gap, pole piece internal diameter and
taper, as well as the overall design of the lens is often performed
by finite element analysis of the magnetic field, taking into
account of the thermal and electrical constraints of the design.
The coils which produce the magnetic field are located within the
lens yoke. The coils can contain a variable current, but typically
utilize high voltages, and therefore require significant insulation
in order to prevent short-circuiting the lens components. Thermal
distributors are placed to ensure the extraction of the heat
generated by the energy lost to resistance of the coil windings.
The windings may be water-cooled, using a chilled water supply in
order to facilitate the removal of the high thermal duty.
[0035] For the deflection system 7, it may include a macroscopic
deflection sub-system 71 and a microscopic deflection sub-system
72. The deflection system 7 causes the beam to scan across a large
field of view (FOV) on a specimen plane 8 of a specimen holder 9
and one or more small FOVs within the large FOV.
[0036] As shown in FIGS. 4 and 5, the macroscopic deflection
sub-system 71 causes the beam to scan across a large field of view
(FOV) 10 on the specimen plane 8 of the specimen holder 9, and the
microscopic sub-deflection system 72 causes the beam to scan across
one or more small FOVs 11 within a large FOV. As shown in FIG. 4,
the specimen plane 8 may contain only one large FOV 10, which may
contain zero, one, two, three or more small FOVs 11. In FIG. 5, the
specimen plane 8 may contain two, three or more large FOVs 10, each
of which may contain zero, one, two, three or more small FOVs
11.
[0037] In the first step of an examination process as shown in FIG.
6, a user may turn off or inactivate the microscopic sub-deflection
system 72. Then, the macroscopic deflection sub-system 71 causes
the beam to scan across a large FOV 10 on the specimen plane 8 of
the specimen holder 9 under a lower resolution (e.g. 10 nm). After
the large FOV scanning is completed, the user finds a pattern of
interesting (POI) in one or more small FOVs 11 within that large
FOV 10, and the user will then zoom into the POI for further
examination with a higher resolution (e.g. 1 nm). As an advantage
of the present invention, the user will not need to mechanically
move the specimen holder 9 to reposition or align the specimen
plane 8 to the center of a target small FOV 11. In other words, the
specimen holder 9 remains stationary relative to the source 2 of
charged particles, no matter the beam is scanning across a given
large FOV 10 or subsequently scanning across one, two or more small
FOVs 11 within that large FOV 10.
[0038] Instead, the user may run the second step by simply
retrieving stored deflecting parameter(s) of the macroscopic
deflection sub-system 71 which previously directed the beam to the
center of the target small FOV 11. The retrieved deflecting
parameter(s) of the macroscopic deflection sub-system 71 will then
be re-applied to the subsystem 71, to direct the beam to the center
of the target small FOV 11. Generally, the position of any small
FOV within a large FOV may be controlled as desired by the
macroscopic deflection sub-system 71 by retrieving and re-applying
stored deflecting parameters (e.g. voltage). As shown in FIG. 7,
after the position of the small FOV within the large FOV is fixed
by the macroscopic deflection sub-system 71, the retrieved and
re-applied deflecting parameter(s) of the macroscopic deflection
sub-system 71 will remain unchanged. Then, the deflecting
parameter(s) of the microscopic deflection sub-system 72 is/are
varied to cause the beam to scan across the small FOV with a higher
resolution.
[0039] In various embodiments of the invention, when the beam scans
across the large FOV 10 in the first step, the spot F2 has a size
A1. When the beam scans across the small FOV 11 within the large
FOV 10 in the second step, the spot F2 has a size A2, and A2<A1.
The in equation of A2<A1 will result in the resolution for
scanning a small FOV is higher than that for a large FOV.
[0040] Typically, the size of the large FOV 10 is adjustable, and
its image may range from 50 um.times.50 um to 200 um.times.200 um
in size with a resolution of 0.5-20 nm. For example, the large FOV
10 may have a size of 100 um.times.100 um with a resolution of 8
nm. The small FOV 11 (e.g. POI, or area of interest) is also
adjustable, and it may range from 0.5 um.times.0.5 um to 5
um.times.5 um in size with a resolution of 0.5-2 nm. For example,
the small FOV may have a size of 5 um.times.5 um with a resolution
of 0.5 nm.
[0041] As shown in FIG. 8, the macroscopic deflection sub-system 71
may include an upper deflector 71a and a lower deflector 71b. The
microscopic deflection sub-system 72 may be located between the
upper deflector 71a and the lower deflector 71b of the macroscopic
deflection system 71. The specimen holder 9 may be downstream with
respect to the lower deflector 71b of the macroscopic deflection
sub-system 71. As shown in FIG. 9, the microscopic deflection
sub-system 72 may also include an upper deflector 72a and a lower
deflector 72b.
[0042] Any other components known in any apparatus of
charged-particle beam or their proper combination may be
incorporated in the present invention. For a skilled person in the
art, many of the components not shown in FIG. 1 are well-known, for
example, suppressor electrode, beam extractor, anode, gun aperture,
condenser lens that is responsible for primary beam formation, beam
blanker, stigmator for the correction of asymmetrical beam
distortions, objective aperture, SEM up detector, deflector, bright
field (BF) detector, dark field (DF) detector. A system for the
insertion into, motion within, and removal of specimens from the
beam path is also needed. The system may include load lock, chamber
interlock, lock port, loading and unloading mechanism, and transfer
table. Other parts in the microscope may be omitted or merely
suggested. In a specific yet exemplary electron microscope 1 as
shown in FIG. 10, the source of charged particles may be an
electron gun 2 configured to emit an electron beam through gun
aperture 12. Along the beam trajectory, co-condenser 3 with
magnetic coil 3C is placed between gun aperture 12 and co-condenser
4 with a magnetic coil 4C. The electron beam is focused to
crossover spot F2 before it passes through beam blanking 13. After
the beam passes through objective aperture 14, it is deflected by
an upper deflector 71a and a lower deflector 71b in the macroscopic
deflection sub-system 71. It can also be deflected by an upper
deflector 72a and a lower deflector 72b in the microscopic
deflection sub-system 72. In the meanwhile, the beam is focused by
the magnetic objective lens 6 onto a specimen within the specimen
holder 9. Electrons scattered from and penetrated through the
specimen are detected by the BSE detector 15, BF detector 16 and DF
detector 17 for generating specimen images.
[0043] The multiple deflection system (71a, 71b, 72a and 72b) is
designed to control electron deflection with different FOV size.
For example, deflectors or deflection nodes 71a and 71b control
electron beam to be incident on a large FOV, while deflectors 72a
and 72b on a small FOV size.
[0044] The novel EM column system as shown in FIG. 10 can scan
larger FOV with low resolution (like 5, 10 or 20 nm) for the full
FOV size. Then, the EM column can switch to high resolution (like 1
nm) automatically without any position and focus change and start
immediately to scan high resolution image on any special location.
A specific software algorithm can be used to control EM scanning of
a larger FOV image with two deflectors (71a, 71b) and co-condensers
(3, 4) in a lower resolution mode (i.e. a higher contribution from
co-condenser 3 or lower contribution from co-condenser 4). The
algorithm will detect related POI (pattern of interesting) and
record related location(s). As shown in FIG. 11, the algorithm can
detect related POI (pattern of interesting) such as the
morphological features of Covid-19 virus (SARS-CoV-2) in a
biological sample and record their location(s). Then the software
will switch co-condensers (3, 4) to a higher resolution mode (i.e.
a lower contribution from co-condenser 3 or a higher contribution
from co-condenser 4). The two deflection nodes (71a and 71b) are
set to or fixed to a controlled voltage. Other two deflection nodes
(72a and 72b) are then used to scan a small FOV 11 with the higher
resolution. As shown in the lower panel of FIG. 11, an image of
Covid-19 virus (SARS-CoV-2) with a high resolution is acquired. A
software system can combine BSE, DF, BF's images from TEM/STEM
system and use a machine learning (ML) algorithm to generate an
enhanced image with differenced image resolution. Such operations,
tasks, and functions are sometimes referred to as being
computer-executed, computerized, processor-executed,
software-implemented, or computer-implemented. They may be realized
by any number of hardware, software, and/or firmware components
configured to perform the specified functions. For example, an
embodiment of a system or a component may employ various integrated
circuit components, e.g., memory elements, digital signal
processing elements, logic elements, look-up tables, or the like,
which may carry out a variety of functions under the control of one
or more microprocessors or other control devices.
[0045] When implemented in software or firmware, various elements
of the systems described herein are essentially the code segments
or executable instructions that, when executed by one or more
processor devices, cause the host computing system to perform the
various tasks. In certain embodiments, the program or code segments
are stored in a tangible processor-readable medium, which may
include any medium that can store or transfer information. Examples
of suitable forms of non-transitory and processor-readable media
include an electronic circuit, a semiconductor memory device, a
ROM, a flash memory, an erasable ROM (EROM), a floppy diskette, a
CD-ROM, an optical disk, a hard disk, or the like.
[0046] Through the above description of the embodiments, those
skilled in the art can understand clearly that the present
application may be implemented by means of software plus necessary
hardware platforms, or of course, may also be implemented all by
software or hardware. Based on such understanding, the entirety of
or a portion of that the technical solutions of the present
application contribute over the background art may be embodied in
the form of a software product. The computer software product may
be stored in storage medium, such as ROM/RAM, disk, optical disk,
etc., and comprise several instructions for enabling one computer
apparatus (which may be a personal computer, a server, or a network
equipment, etc.) to execute the methods described in the respective
embodiments or described in certain parts of the embodiments of the
present application.
[0047] In the foregoing specification, embodiments of the present
invention have been described with reference to numerous specific
details that may vary from implementation to implementation. The
specification and drawings are, accordingly, to be regarded in an
illustrative rather than a restrictive sense. The sole and
exclusive indicator of the scope of the invention, and what is
intended by the applicant to be the scope of the invention, is the
literal and equivalent scope of the set of claims that issue from
this application, in the specific form in which such claims issue,
including any subsequent correction.
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