U.S. patent application number 15/643271 was filed with the patent office on 2018-12-20 for on-axis illumination and alignment for charge control during charged particle beam inspection.
The applicant listed for this patent is APPLIED MATERIALS ISRAEL LTD., ICT Integrated Circuit Testing Gesellschaft fur Halbleiterpruftechnik mbH. Invention is credited to Alex Goldenshtein, Stefan Lanio.
Application Number | 20180364564 15/643271 |
Document ID | / |
Family ID | 64657381 |
Filed Date | 2018-12-20 |
United States Patent
Application |
20180364564 |
Kind Code |
A1 |
Goldenshtein; Alex ; et
al. |
December 20, 2018 |
ON-AXIS ILLUMINATION AND ALIGNMENT FOR CHARGE CONTROL DURING
CHARGED PARTICLE BEAM INSPECTION
Abstract
A charged particle beam apparatus includes a charged particle
source configured to generate charged particles, an electrode
configured to accelerate the charged particles to form a charged
particle beam, a bender unit configured to adjust a path of the
charged particle beam, and an objective lens configured to focus
the charged particle beam onto a spot on a sample. The charged
particle beam passes through a bore of the objective lens as the
charged particle beam propagates from the charged particle source
to the sample. The apparatus also includes a light source
configured to generate a light beam, and a mirror disposed within
the bender unit and arranged to direct the light beam to the spot
on the sample.
Inventors: |
Goldenshtein; Alex; (Ness
Ziona, IL) ; Lanio; Stefan; (Erding, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
APPLIED MATERIALS ISRAEL LTD.
ICT Integrated Circuit Testing Gesellschaft fur
Halbleiterpruftechnik mbH |
Rehovot
Heimstetten |
|
IL
DE |
|
|
Family ID: |
64657381 |
Appl. No.: |
15/643271 |
Filed: |
July 6, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62519596 |
Jun 14, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J 37/3007 20130101;
H01J 2237/0047 20130101; H01J 37/222 20130101; H01J 37/3045
20130101; G03F 9/7073 20130101; H01J 37/228 20130101; H01J
2237/30433 20130101; G03F 1/86 20130101; H01J 2237/063 20130101;
H01J 37/026 20130101; H01J 37/3174 20130101; H01J 37/28
20130101 |
International
Class: |
G03F 1/86 20060101
G03F001/86; H01J 37/304 20060101 H01J037/304; G03F 9/00 20060101
G03F009/00; H01J 37/30 20060101 H01J037/30; H01J 37/317 20060101
H01J037/317; H01J 37/22 20060101 H01J037/22 |
Claims
1. A charged particle beam apparatus, comprising: a charged
particle source configured to generate charged particles; an
electrode configured to accelerate the charged particles to form a
charged particle beam; a bender unit configured to adjust a path of
the charged particle beam; an objective lens configured to focus
the charged particle beam onto a spot on a sample, the charged
particle beam passing through a bore of the objective lens as the
charged particle beam propagates from the charged particle source
to the sample; a light source configured to generate a light beam;
a mirror disposed within the bender unit and arranged to direct the
light beam to the spot on the sample; a sample support configured
to support the sample, the sample support having a pinhole
extending through a central region; and a light sensor disposed on
an opposite side of the sample support from the objective lens, the
light sensor configured to sense light when the light beam is
aligned with the pinhole.
2. The apparatus of claim 1 wherein a pointing direction of the
light source is adjustable to align the light beam with the spot on
the sample.
3. The apparatus of claim 1 wherein a position of the mirror is
adjustable to align the light beam with the spot on the sample.
4. The apparatus of claim 1 wherein the path of the charged
particle beam is adjustable to scan the charged particle beam on a
surface of the sample, and the light source is adjustable to align
the light beam with the charged particle beam on the surface of the
sample during scanning.
5. The apparatus of claim 1 wherein an axis of the charged particle
beam and an axis of the light beam are separated by an angle of
less than 3.degree. to provide substantially on-axis illumination
of the spot.
6. The apparatus of claim 1 wherein the mirror is arranged to
direct the light beam through the bore of the objective lens and to
the spot on the sample.
7. (canceled)
8. The apparatus of claim 1 wherein the bender unit comprises an
unobstructed path that does not block the light beam as the light
beam passes through the bender unit.
9. The apparatus of claim 1 further comprising a detector
configured to detect charged particles emitted or reflected from
the sample.
10. The apparatus of claim 1 wherein a path of the light beam from
the mirror to the spot on the sample is substantially normal to a
surface of the sample.
11. A method of scanning a sample, the method comprising:
generating charged particles using a charged particle source;
accelerating the charged particles using an electrode to form a
charged particle beam; adjusting a path of the charged particle
beam using a bender unit; focusing the charged particle beam onto a
spot on the sample using an objective lens, the charged particle
beam passing through a bore of the objective lens as the charged
particle beam propagates from the charged particle source to the
sample; generating a light beam using a light source; directing the
light beam through the bore of the objective lens using a mirror
disposed within the bender unit, the light beam directed to the
spot on the sample; and adjusting a position of the mirror to align
the light beam with the spot on the sample.
12. The method of claim 11 further comprising adjusting a pointing
direction of the light source to align the light beam with the spot
on the sample.
13. (canceled)
14. The method of claim 11 further comprising: adjusting the path
of the charged particle beam to scan the charged particle beam on a
surface of the sample; and adjusting an orientation of the light
source to align the light beam with the charged particle beam on
the surface of the sample during scanning.
15. A method of aligning a charged particle beam of a charged
particle apparatus with a light beam, the method comprising:
generating charged particles using a charged particle source;
accelerating the charged particles using an electrode to form the
charged particle beam; adjusting a path of the charged particle
beam using a bender unit; focusing the charged particle beam onto a
sample support using an objective lens, the charged particle beam
passing through a bore of the objective lens as the charged
particle beam propagates from the charged particle source to the
sample support; scanning the charged particle beam across a surface
of the sample support; detecting charged particles emitted or
reflected from the sample support during scanning to identify a
pinhole in the sample support; adjusting the path of the charged
particle beam to be substantially aligned with the pinhole;
generating the light beam using a light source; directing the light
beam toward the surface of the sample using a mirror disposed
within the bender unit; detecting the light beam using a light
sensor when the light beam is aligned with the pinhole; and
adjusting a path of the light beam to be substantially aligned with
the pinhole.
16. The method of claim 15 further comprising: loading a sample
onto the sample support; scanning a surface of the sample with the
charged particle beam; and adjusting the path of the light beam to
align the light beam with the charged particle beam on the surface
of the sample during scanning.
17. The method of claim 15 wherein the path of the light beam is
adjusted by changing a pointing direction of the light source.
18. The method of claim 15 wherein the path of the light beam is
adjusted by changing a position of the mirror.
19. The method of claim 15 wherein the charged particle beam and
the light beam are separated by an angle of less than 2.degree.
when both are aligned with the pinhole.
20. The method of claim 15 wherein the mirror is arranged to direct
the light beam through the bore of the objective lens and to the
surface of the sample.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/519,596, filed Jun. 14, 2017, the entire
contents of which are incorporated herein by reference in their
entirety for all purposes.
BACKGROUND
[0002] Charged particle beam inspection tools scan areas of a
sample with a charged particle beam. An example is an electron beam
inspection (EBI) tool that scans areas of a sample with an electron
beam.
[0003] Scanning with a charged particle beam causes the sample to
emit charged particles such as secondary and backscattered
electrons. The charged particle beam inspection tool may detect
some of the emitted charged particles to generate an image of the
scanned area.
[0004] Scanning also charges the sample (or the scanned area).
Charging can distort an image of the scanned area or distort images
of areas that are electrically coupled to the scanned area.
[0005] Thus, there is a growing need to prevent or reduce charging
during inspection processes and/or to activate or turn on devices
such as diodes within the sample that can facilitate charge
dissipation.
SUMMARY
[0006] In light of the above, apparatuses and methods for charged
particle beam inspection are provided that can reduce or eliminate
sample charging. In an embodiment, for example, a method of
scanning a spot on a sample includes directing a charged particle
beam and a light beam to the spot on the sample. The light beam and
the charged particle beam can be aligned on the spot, and the light
beam can be arranged to impinge on the sample at a substantially
normal incidence. This can improve light absorption and charge
dissipation allowing charge control during inspection.
[0007] In accordance with an embodiment, a charged particle beam
apparatus includes a charged particle source configured to generate
charged particles, an electrode configured to accelerate the
charged particles to form a charged particle beam, a bender unit
configured to adjust a path of the charged particle beam, and an
objective lens configured to focus the charged particle beam onto a
spot on a sample. The charged particle beam passes through a bore
of the objective lens as the charged particle beam propagates from
the charged particle source to the sample. The apparatus also
includes a light source configured to generate a light beam and a
mirror disposed within the bender unit and arranged to direct the
light beam to the spot on the sample.
[0008] In an embodiment, the mirror is arranged to direct the light
beam through the bore of the objective lens and to the spot on the
sample.
[0009] In accordance with another embodiment, a method of scanning
a sample includes generating charged particles using a charged
particle source, accelerating the charged particles using an
electrode to form a charged particle beam, adjusting a path of the
charged particle beam using a bender unit, and focusing the charged
particle beam onto a spot on the sample using an objective lens.
The charged particle beam passes through a bore of the objective
lens as the charged particle beam propagates from the charged
particle source to the sample. The method also includes generating
a light beam using a light source and directing the light beam
through the bore of the objective lens using a mirror disposed
within the bender unit. The light beam is directed to the spot on
the sample.
[0010] In accordance with yet another embodiment, a method of
aligning a charged particle beam of a charged particle apparatus
with a light beam includes generating charged particles using a
charged particle source, accelerating the charged particles using
an electrode to form the charged particle beam, adjusting a path of
the charged particle beam using a bender unit, and focusing the
charged particle beam onto a sample support using an objective
lens. The charged particle beam passing through a bore of the
objective lens as the charged particle beam propagates from the
charged particle source to the sample support. The charged particle
beam is scanned across a surface of the sample support, and charged
particles emitted or reflected from the sample support during
scanning are detected to identify a pinhole in the sample support.
The path of the charged particle beam is adjusted to be
substantially aligned with the pinhole. The method also includes
generating the light beam using a light source and directing the
light beam toward the surface of the sample using a mirror disposed
within the bender unit. The light beam is detected using a light
sensor when the light beam is aligned with the pinhole. A path of
the light beam is adjusted to be substantially aligned with the
pinhole.
[0011] Embodiments are also directed to apparatuses for carrying
out the disclosed methods and include apparatus parts for
performing each described method feature. The method features may
be performed by way of hardware components, a computer programmed
by appropriate software, by any combination of the two, or in any
other manner. Furthermore, embodiments are also directed to methods
of operating the described apparatuses and include method features
for carrying out every function of the apparatuses.
[0012] Further aspects, advantages, and features will be apparent
from the claims, description, and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The various embodiments described herein, both as to
organization and method of operation, together with features and
advantages thereof, can best be understood by reference to the
following detailed description and accompanying drawings, in
which:
[0014] FIGS. 1-4 are simplified cross-sectional views of charged
particle beam apparatuses in accordance with some embodiments;
[0015] FIG. 5 is a plot of light absorption in silicon, and FIG. 6
is a simplified diagram illustrating a relationship between
illumination angle and spot size;
[0016] FIG. 7 is a flowchart that outlines a method of scanning a
sample in accordance with an embodiment; and
[0017] FIG. 8 is a flowchart that outlines a method of aligning a
charged particle beam with a light beam in accordance with an
embodiment.
[0018] It will be appreciated that for simplicity and clarity of
illustration, elements shown in the figures have not necessarily
been drawn to scale. For example, the dimensions of some of the
elements may be exaggerated relative to other elements for clarity.
Further, where considered appropriate, reference numerals may be
repeated among the figures to indicate corresponding or analogous
elements.
DETAILED DESCRIPTION
[0019] In the following detailed description, numerous specific
details are set forth in order to provide a thorough understanding
of the embodiments described herein. However, it should be
understood that the various embodiments can be practiced without
these specific details. In other instances, well-known methods,
procedures, and components have not been described in detail so as
not to obscure the described features.
[0020] Reference will be made in detail to the various embodiments,
one or more examples of which are illustrated in the figures. Each
example is provided by way of explanation and is not meant as a
limitation. Further, features illustrated or described as part of
one embodiment can be used on or in conjunction with other
embodiments to yield yet a further embodiment. The description is
intended to include these modifications and variations.
[0021] A "specimen" or "sample" as referred to herein includes, but
is not limited to, semiconductor wafers, semiconductor workpieces,
photolithographic masks, and other workpieces such as memory disks
and the like. According to some embodiments, which can be combined
with other embodiments described herein, the apparatus and methods
are configured for or are applied for inspection, for critical
dimensioning applications, and defect review applications.
[0022] Any reference in the specification to a method should be
applied mutatis mutandis to a system capable of executing the
method.
[0023] Any reference in the specification to a system should be
applied mutatis mutandis to a method that can be executed by the
system.
[0024] Embodiments described herein relate generally to apparatuses
and methods for reducing charging during charged particle beam
inspections. Some embodiments may also be used to activate or turn
on devices within a sample such as diodes. In accordance with an
embodiment, for example, a charged particle beam and a light beam
can be aligned to a spot on a sample. The light beam may be
directed to the spot by a mirror arranged in a bender unit that is
configured to adjust a path of the charged particle beam. The light
beam may be directed from the mirror through a bore of an objective
lens. The light beam can be arranged to impinge on the spot at a
substantially normal incidence.
[0025] FIG. 1 is a simplified cross-sectional view of a charged
particle beam apparatus in accordance with an embodiment. In this
example, a charged particle source 102 is provided that is
configured to generate charged particles that are accelerated by an
electrode 104 to form a charged particle beam 106. As an example,
the source may generate electrons that are accelerated by the
electrode 104 to generate an electron beam. The apparatus includes
a bender unit 108 that is configured to adjust a path of the
charged particle beam 106 using known deflection techniques. The
bender unit 108 may use magnetic and/or electrostatic fields to
adjust the path. The apparatus also includes an objective lens 110
that is configured to focus the charged particle beam 106 onto a
spot on sample 112 using known focusing techniques. The objective
lens 110 may use magnetic and/or electrostatic fields to focus the
charged particle beam 106. The charged particle beam 106 passes
through a bore 114 of the objective lens 110 as it propagates from
the charged particle source 102 to the sample 112. The bender unit
108 and objective lens 110 align the charged particle beam 106 with
the spot on the sample. Other alignment elements may be included in
some embodiments in accordance with known techniques.
[0026] The apparatus also includes a detector 122 that is
configured to detect charged particles emitted or reflected from
the sample 112. The detector 122 is not limited to the
configuration shown in this example and may be disposed in
accordance with known techniques before the objective lens 110,
within the objective lens 110, and/or after the objective lens 110.
Some embodiments may include multi-detector configurations.
[0027] The apparatus also includes a light source 116 configured to
generate a light beam 118. The light source 116 may be a light
emitting diode or laser light source. A mirror 120 or other
reflector disposed within the bender unit 108 is arranged to direct
the light beam 118 to the spot on the sample 112. In some
embodiments, the light beam 118 can be directed through the bore
114 of the objective lens 110 as it propagates from the mirror 120
to the sample 112. The light beam 118 can be used to control
charging during particle beam inspection. This is particularly
beneficial when scanning samples that include isolated conducting
layers or non-conducting layers such as insulators that cannot
otherwise dissipate charge buildup.
[0028] In some embodiments, a path of the light beam 118 can be
adjusted to align the light beam 118 with the spot on the sample
112 by adjusting a pointing direction or orientation of the light
source 116. In other embodiments, the mirror 120 may be adjustable
to align the light beam 118 with the spot on the sample 112. As an
example, the light source 116 and/or the mirror 120 may be mounted
on an alignment stage that allows orientation adjustment in one or
more axes. As another example, the mirror 120 may comprise one or
more mechanical mirrors whose position can be altered to adjust the
path of the light beam.
[0029] Adjusting the beam path can allow the light beam 118 to be
aligned with the charged particle beam 106 on a surface of the
sample 112 during scanning. The charged particle beam 106 can be
scanned across the surface of the sample 112 using the bender unit
108 and/or other deflectors (not shown) using known scanning
techniques, and the light beam 118 can be aligned with the charged
particle beam 106 during scanning so that they both impinge on the
sample 112 at the same spot.
[0030] The bender unit 108 may provide an unobstructed optical path
for the light beam 118 as it passes through the bender unit 108. In
an embodiment, the optical path includes one or more windows to
isolate the light source 116 from a chamber of the charged particle
beam apparatus without blocking the light beam. In some
embodiments, the mirror may include multiple mirrors or reflectors
that direct the light beam 118 from the light source 116 to the
sample 112. Some of the mirrors or reflectors may be positioned
outside the bender unit.
[0031] By positioning the mirror 120 in the bender unit 108, the
light beam 118 can provide substantially on-axis illumination of
the sample. In some embodiments, a path of the light beam 118 from
the mirror 120 to the sample 112 may be substantially normal to a
surface of the sample. As explained more fully below with regard to
FIG. 5, this can increase light absorption and provide improved
charged control during inspection. An angle 124 between the light
beam 118 and the charged particle beam 106 can be 5.degree. or less
in some embodiments.
[0032] FIG. 2 is a simplified cross-sectional view of a charged
particle beam apparatus in accordance with another embodiment. The
apparatus in this example is similar to the one shown in FIG. 1 and
includes a charged particle source 202 and electrode 204 for
generating a charged particle beam 206. The apparatus also includes
a bender unit 208 and objective lens 210 for directing the charged
particle beam 206 to a spot on sample 212. The apparatus also
includes a detector 222 for detecting charged particles emitted or
reflected from the sample 212. The apparatus also includes a light
source 216 for generating a light beam 218 and a mirror 220 or
other reflector disposed within the bender unit 208 and arranged to
direct the light beam 218 to the spot on the sample 212. The
charged particle beam 206 and the light beam 218 pass through a
bore 214 of the objective lens 210 as they propagate to the sample
212. Most of these components are similar to corresponding
components shown and described with regard to FIG. 1 and may not be
separately described in this section.
[0033] The example shown in FIG. 2 is different from the example
shown in FIG. 1 in that the charged particle beam 206 is generated
slightly off-axis with regard to an axis defined by the objective
lens 210. A path of the charged particle beam 206 is adjusted by an
angle 226 using the bender unit 208 and/or other alignment elements
in accordance with known techniques so that the charged particle
beam 206 is directed to the spot on the sample 212. Generating the
charged particle beam 206 slightly off-axis allows the mirror 220
to be arranged so that the light beam 218 is substantially on-axis
as it propagates to the spot on the sample 212. Alternatively, the
charged particle beam 206 may be generated on-axis, and one or more
bender units may adjust the path of the charged particle beam 206
off-axis to go around the mirror 220 and then back on-axis toward
the spot on the sample. An angle 224 between the charged particle
beam and the light beam is exaggerated in FIGS. 1-2 and may be
about 5.degree. or less in some embodiments.
[0034] FIG. 3 is a simplified cross-sectional view of a charged
particle beam apparatus in accordance with another embodiment. The
apparatus in this example is similar to the ones shown in FIGS. 1-2
and includes a charged particle source 302 and electrode 304 for
generating a charged particle beam 306. The apparatus also includes
a bender unit 308 and objective lens 310 for directing the charged
particle beam 306 to a spot on sample 312. The apparatus also
includes a detector 322 for detecting charged particles emitted or
reflected from the sample 312. The apparatus also includes a light
source 316 for generating a light beam 318 and a mirror 320 or
other reflector disposed within the bender unit 308 and arranged to
direct the light beam 318 to the spot on the sample 312. The
charged particle beam 306 and the light beam 318 pass through a
bore 314 of the objective lens 310 as they propagate to the sample
312. Most of these components are similar to corresponding
components shown and described with regard to FIG. 1 and may not be
separately described in this section.
[0035] The example shown in FIG. 3 is different from the examples
shown in FIGS. 1-2 in that a path of the charged particle beam 306
is adjusted by a first angle 326 and a second angle 328 using the
bender unit 308, the objective lens 310, and/or other alignment
elements. In this example, the charged particle beam 306 impinges
on the sample at a substantially normal incidence. This arrangement
allows the charged particle beam 306 and the light beam 318 to be
separated by an angle 324 of 5.degree. or less so that both are
directed to the sample 312 at a substantially normal incidence.
[0036] FIG. 4 is a simplified cross-sectional view of a charged
particle beam apparatus in accordance with another embodiment. The
apparatus in this example is similar to the one shown in FIGS. 1-3
and includes a charged particle source 402 and electrode 404 for
generating a charged particle beam 406. The apparatus also includes
a bender unit 408 and objective lens 410 for directing the charged
particle beam 406 toward a sample support 452. The apparatus also
includes a light source 416 for generating a light beam 418 and a
mirror 420 or other reflector disposed within the bender unit 408
and arranged to direct the light beam 418 toward the sample support
452. Most of these components are similar to corresponding
components shown and described with regard to FIG. 1 and may not be
separately described in this section.
[0037] The example shown in FIG. 4 is different from the example
shown in FIG. 1 in that the sample support 452 is shown rather than
a sample. It should be appreciated that the samples 112, 212, 312
shown in FIGS. 1-3 are supported by a sample support even though
the sample support is not explicitly shown. Similarly, it should be
appreciated that the example of FIG. 4 includes one or more
detectors even though the detectors are not explicitly shown.
[0038] In some embodiments, the sample support 452 includes a
pinhole 450 extending through a central region and a mirror 454 or
other reflector arranged to direct light passing through the
pinhole 450 to a light sensor 456. The light sensor 456 may be
disposed on an opposite side of the sample support 452 from the
objective lens 410. These features can be used to align the charged
particle beam 406 and light beam 418 at a particular spot on the
sample.
[0039] To align the beams, the charged particle beam 406 is scanned
across a surface of the sample support 452. Charged particles
emitted or reflected from the sample support 452 are detected to
identify the pinhole 450 in the sample support 452. A path of the
charged particle beam 406 is adjusted (if necessary) to be
substantially aligned with the pinhole 450.
[0040] The light sensor 456 is used to detect light when the light
beam 418 is aligned with the pinhole 450. A path of the light beam
418 is adjusted (if necessary) to be substantially aligned with the
pinhole. After aligning the charged particle beam 406 and the light
beam 418 with the pinhole 450, a sample may be loaded on the sample
support 452 and inspected in accordance with the inspection
processes described herein.
[0041] It should be appreciated that not all embodiments include a
sample support with these features, and some embodiments include a
solid sample support that does not include a pinhole. For
embodiments that include a pinhole, a diameter and shape of the
pinhole may be selected based on a desired precision in alignment
between the charged particle beam and the light beam.
[0042] FIG. 5 is a plot of light absorption in silicon. Some
samples may include semiconductor devices or layers that form p-n
junctions or other structures that can be electrically turned on or
made conductive. Depending on the type and depth of the structure,
the wavelength of light provided by the light beam can be selected
to facilitate dissipation of charge that may otherwise buildup on
the sample and/or to activate or turn on devices such as diodes
within the sample. The wavelength may be selected to penetrate
outer layers and be absorbed at the p-n junction or at other layers
that can facilitate charge dissipation and/or charge conduction.
This improves charge control during inspection. Using FIG. 5 as an
example, light with a wavelength of about 400 nm has a broad
absorption length in silicon and can provide improved charge
control in some samples compared to light at other wavelengths.
[0043] In some embodiments, a polarization of the light beam can be
selected based on a structure on the sample to improve light
penetration into the sample. For example, the polarization of the
light beam can be selected to be substantially perpendicular to
lines on the sample to improve penetration compared to polarization
that is substantially parallel to the lines.
[0044] FIG. 6 is a simplified diagram illustrating a relationship
between illumination angle and spot size. The light beam in this
example strikes the sample at a large illumination angle (or angle
of incidence). The large illumination angle increases the spot size
on a surface of the sample by
1 cos ( .theta. ) . ##EQU00001##
As the spot size increases, the light is spread out over a larger
area and radiant flux decreases by cos(.theta.). On the other hand,
as the illumination angle approaches normal incidence (zero
illumination angle), the radiant flux approaches a maximum. This
can improve charge control. Some embodiments described herein allow
the light beam to be directed to the sample at a substantially
normal incidence, thus improving absorption and consequently charge
control for a given light beam.
[0045] FIG. 7 is a flowchart that outlines a method of scanning a
sample in accordance with an embodiment. The method includes
generating charged particles using a charged particle source (702),
accelerating the charged particles using an electrode to form a
charged particle beam (704), adjusting a path of the charged
particle beam using a bender unit (706), and focusing the charged
particle beam onto a spot on the sample using an objective lens
(708). The charged particle beam passes through a bore of the
objective lens as the charged particle beam propagates from the
charged particle source to the sample.
[0046] The method also includes generating a light beam using a
light source (710), and directing the light beam through a bore of
the objective lens using a mirror disposed within the bender unit
(712). The light beam may be directed to the spot on the sample by
adjusting a pointing direction of the light source or by adjusting
a position of the mirror. Adjusting the position may include
adjusting a location and/or an orientation of the mirror.
[0047] In some embodiments, the path of the charged particle beam
may be adjusted to scan a surface of the sample, and the light beam
may be aligned with the charged particle beam on the surface of the
sample during scanning.
[0048] FIG. 8 is a flowchart that outlines a method of aligning a
charged particle beam with a light beam in accordance with an
embodiment. The method includes adjusting a path of a charged
particle beam using a bender unit (802), focusing the charged
particle beam onto a sample support using an objective lens (804),
and scanning the charged particle beam across a surface of the
sample support (806). Charged particles emitted or reflected from
the sample support are detected during scanning to identify a
pinhole in the sample support (808). A path of the charged particle
beam is adjusted to be substantially aligned with the pinhole
(810).
[0049] The method also includes generating a light beam using a
light source (812) and directing the light beam toward the surface
of the sample using a mirror disposed within the bender unit (814).
The light beam is detected using a light sensor when the light beam
is aligned with the pinhole (816). A path of the light beam is
adjusted to be substantially aligned with the pinhole (818).
[0050] In some embodiments, the mirror is arranged to direct the
light beam through the bore of the objective lens and to the
surface of the sample.
[0051] It should be appreciated that the specific steps illustrated
in FIGS. 7-8 provide particular methods according to some
embodiments. Other sequences of steps may also be performed
according to alternative embodiments. For example, alternative
embodiments may perform the steps outlined above in a different
order. Moreover, the individual steps illustrated in FIGS. 7-8 may
include multiple sub-steps that may be performed in various
sequences. Furthermore, additional steps may be added or removed
depending on the particular application.
[0052] While the foregoing is directed to specific embodiments,
other and further embodiments may be devised without departing from
the basic scope thereof, and the scope thereof is determined by the
claims that follow.
* * * * *