U.S. patent application number 12/658476 was filed with the patent office on 2010-08-12 for particle beam system.
Invention is credited to Michael Albiez, Rainer Arnold, Hubert Mantz.
Application Number | 20100200750 12/658476 |
Document ID | / |
Family ID | 42077310 |
Filed Date | 2010-08-12 |
United States Patent
Application |
20100200750 |
Kind Code |
A1 |
Mantz; Hubert ; et
al. |
August 12, 2010 |
Particle beam system
Abstract
A particle beam system comprises a particle beam source 5 for
generating a primary particle beam 13, an objective lens 19 for
focusing the primary particle beam 13 in an object plane 23; a
particle detector 17; and an X-ray detector 47 arranged between the
objective lens and the object plane. The X-ray detector comprises
plural semiconductor detectors, each having a detection surface 51
oriented towards the object plane. A membrane is disposed between
the object plane and the detection surface of the semiconductor
detector, wherein different semiconductor detectors have different
membranes located in front, the different membranes differing with
respect to a secondary electron transmittance.
Inventors: |
Mantz; Hubert; (Aalen,
DE) ; Arnold; Rainer; (Ulm, DE) ; Albiez;
Michael; (Aalen, DE) |
Correspondence
Address: |
Bruce D Riter
101 First Street PMB 208
Los Altos
CA
94022-2778
US
|
Family ID: |
42077310 |
Appl. No.: |
12/658476 |
Filed: |
February 8, 2010 |
Current U.S.
Class: |
250/310 |
Current CPC
Class: |
H01J 37/05 20130101;
H01J 37/256 20130101; H01J 37/28 20130101; H01J 37/222 20130101;
H01J 37/244 20130101 |
Class at
Publication: |
250/310 |
International
Class: |
H01J 37/26 20060101
H01J037/26; H01J 37/28 20060101 H01J037/28; H01J 37/244 20060101
H01J037/244; H01J 37/10 20060101 H01J037/10 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 9, 2009 |
DE |
10 2009 008 063.5 |
Claims
1. Particle beam system comprising: a particle beam source
configured to generate a primary particle beam; an objective lens
configured to focus the primary particle beam in an object plane; a
particle detector; and an X-ray detector arranged between the
objective lens and the object plane; wherein the X-ray detector
comprises: first and second semiconductor detectors, each having a
detection surface oriented towards the object plane; a first
membrane disposed between the object plane and the detection
surface of the first semiconductor detector, and a second membrane
disposed between the object plane and the detection surface of the
second semiconductor detector, wherein a transmittance for
electrons of the first membrane is greater than a transmittance for
electrons of the second membrane.
2. The particle system according to claim 1, wherein the
transmittance of the first membrane is greater than 0.5 for
electrons having a kinetic energy of 12 keV, and wherein the
transmittance of the second membrane is less than 0.3 for electrons
having the kinetic energy of 12 keV.
3. The particle beam system according to claim 1, wherein the
transmittance of the first membrane is greater than 0.5 for
electrons having a kinetic energy of 8 keV, and wherein the
transmittance of the second membrane is less than 0.3 for electrons
having the kinetic energy of 8 keV.
4. The particle beam system according to claim 1, wherein a
transmittance for X-rays of the first membrane is greater than 0.2
for X-rays having an energy of 0.5 keV, and wherein a transmittance
for X-rays of the second membrane is less than 0.1 for X-rays
having the energy of 0.5 keV.
5. The particle beam system according to claim 1, further
comprising a controller having a signal processing module
configured to determine measurement data based on detection signals
generated by the first semiconductor detector and on detection
signals generated by the second semiconductor detector.
6. The particle system according to claim 1, further comprising a
deflector configured to direct the primary particle beam to
different locations on the object plane.
7. The particle beam system according to claim 6, further
comprising a controller having a control module configured to
control the deflector such that the primary beam is scanned across
a portion of the object plane and such that an image of an object
is generated based on detection signals generated by the first and
second semiconductor detectors.
8. The particle beam system according to claim 1, wherein the first
and second semiconductor detectors are mounted on a ring structure
surrounding a beam path of the primary particle beam.
9. The particle beam system according to claim 8, wherein three or
more semiconductor detectors are mounted on the ring structure, and
wherein two or more of the semiconductor detectors include a
membrane located between the object plane and the respective
semiconductor detector.
10. A particle beam system comprising: a particle beam source
configured to generate a primary particle beam; an objective lens
configured to focus the primary particle beam in an objective
plane; an electron detector; and an X-ray detector arranged between
the objective lens and the object plane, wherein the X-ray detector
comprises a first semiconductor detector having a detection surface
oriented towards the object plane, wherein the particle beam system
further comprises an actuator and a first membrane connected to the
actuator, wherein the actuator is configured to reciprocate the
first membrane between a first position in which a first membrane
is located between the semiconductor detector and the object plane,
and a second position in which the first membrane is not positioned
between the semiconductor detector and the object plane.
11. The particle beam system according to claim 10, further
comprising a second membrane coupled to the actuator such that the
second membrane is not positioned between the semiconductor
detector and the object plane when the first membrane is in its
first position, and such that the second membrane is positioned
between the semiconductor detector and the object plane when the
first membrane is in the second position, and wherein a
transmittance for electrons of the first membrane is greater than a
transmittance for electrons of the second membrane.
12. The particle system according to claim 11, wherein the
transmittance of the first membrane is greater than 0.5 for
electrons having a kinetic energy of 12 keV, and wherein the
transmittance of the second membrane is less than 0.3 for electrons
having the kinetic energy of 12 keV.
13. The particle beam system according to claim 12, wherein the
transmittance of the first membrane is greater than 0.5 for
electrons having a kinetic energy of 8 keV, and wherein the
transmittance of the second membrane is less than 0.3 for electrons
having the kinetic energy of 8 keV.
14. The particle beam system according to claim 12, wherein a
transmittance for X-rays of the first membrane is greater than 0.2
for X-rays having an energy of 0.5 keV, and wherein a transmittance
for X-rays of the second membrane is less than 0.1 for X-rays
having the energy of 0.5 keV.
15. The particle beam system according to one of claims 12 to 9,
wherein the semiconductor detector carries a third membrane located
between the detection surface of the semiconductor detector and the
object plane.
16. The particle beam system according to claim 10, further
comprising a controller having a signal processing module
configured to determine measurement data based on detection signals
generated by the first semiconductor detector and on detection
signals generated by the second semiconductor detector.
17. The particle system according to claim 10, further comprising a
deflector configured to direct the primary particle beam to
different locations on the object plane.
18. The particle beam system according to claim 17, further
comprising a controller having a control module configured to
control the deflector such that the primary beam is scanned across
a portion of the object plane and such that an image of an object
is generated based on detection signals generated by the first and
second semiconductor detectors.
19. The particle beam system according to claim 10, wherein the
first and second semiconductor detectors are mounted on a ring
structure surrounding a beam path of the primary particle beam.
20. The particle beam system according to claim 19, wherein three
or more semiconductor detectors are mounted on the ring structure,
and wherein two or more of the semiconductor detectors include a
membrane located between the object plane and the respective
semiconductor detector.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present application claims priority of German Patent
Application No. 10 2009 008 063.5, filed Feb. 9, 2009, entitled
"PARTICLE OPTICAL SYSTEM", the contents of which are hereby
incorporated by reference in their entirety.
FIELD OF THE INVENTION
[0002] The invention relates to a particle beam system having a
particle beam source for generating a primary particle beam and an
electron detector and an X-ray detector.
BACKGROUND OF THE INVENTION
[0003] A conventional particle microscope comprises a particle beam
source for generating a primary particle beam and an electron
detector. The particle microscope can be an electron microscope
having an electron beam source as its particle source, and the
particle microscope can be an ion microscope having an ion source
as its particle source. Some conventional electron microscopes
include an X-ray detector for detecting X-rays generated by the
primary electron beam at an inspected object. An energy spectrum of
such X-rays may comprise characteristic lines indicative of
elements included in the object. An analysis of the X-rays may
comprise an analysis with respect to energy of detected X-rays. One
example of such analysis is an analysis commonly referred to as
Energy Dispersive X-ray Spectroscopy (EDX).
[0004] A conventional electron microscope including an X-ray
detector is known from US 2006/0138325 A1. The X-ray detector of
this microscope receives X-rays originating from an object and
generated at the object by a primary electron beam focused onto the
object. Since the primary electron beam also generates secondary
electrons, which should not be detected by the X-ray detector, the
X-ray detector comprises an electron trap to prevent secondary
electrons from generating detection signals in the X-ray detectors.
Such detection signals generated by secondary electrons could be
erroneously interpreted as X-ray signals in a subsequent analysis.
The electron trap may comprise a magnetic electron trap.
[0005] A detection efficiency for X-rays has been perceived as
being too low in conventional electron microscopes including an
X-ray detector. This perceived lack of efficiency applies in
particular in a situation where the primary electron beam has a low
energy.
SUMMARY OF THE INVENTION
[0006] The invention has been accomplished taking the above
problems into consideration.
[0007] Embodiments of the invention provide a particle beam system
comprising a particle beam source, an electron detector and an
X-ray detector having a relatively simple configuration. Other
embodiments of the invention provide a particle beam system
comprising a particle beam source, an electron detector and an
X-ray detector having an improved performance with respect to X-ray
detection.
[0008] According to embodiments, a particle beam system comprises a
particle beam source configured to generate a primary particle
beam, an objective lens configured to focus the primary particle
beam in an object plane, an X-ray detector having at least two
semiconductor detectors, wherein each of the semiconductor
detectors has a detection surface oriented towards an object
disposed in the object plane for inspection, and wherein a membrane
or window is located between the object and the detection surface
of the respective detector. The membranes located in front of the
at least two semiconductor detectors differ with respect to a
transmittance for secondary electrons.
[0009] The X-ray detector does not comprise any magnetic electron
traps. The inventors found that magnetic electron traps of an X-ray
detector located close to an objective lens of an electron
microscope may disturb electromagnetic fields generated by the
objective lens for focusing the primary electron beam. Such
disturbance of the electromagnetic fields generated by the
objective lens may affect the focusing of the primary electron
beam, which may finally reduce a performance of the system.
[0010] In the X-ray detector according to the embodiment, secondary
electrons may penetrate the membrane provided in front of the
semiconductor detector such that they generate detection signals in
the semiconductor detector and are detected accordingly. However,
since two different membranes are provided which differ with
respect to their transmittance for secondary electrons, different
amounts of secondary electrons will penetrate the membranes such
that different amounts of detection signals will be generated which
originate from detection events triggered by electrons. It is thus
possible to determine an amount of detection events caused by
electrons for at least one of the semiconductor detectors. A
remaining amount of detection events not caused by electrons will
then represent an amount of detected X-ray events. It is thus
possible to obtain a relatively accurate detection of X-ray amounts
without having to use a magnetic electron trap, for example.
[0011] According to a further embodiment, the X-ray detector
comprises a ring structure surrounding a beam path of the primary
particle beam, wherein the ring structure carries at least two
semiconductor detectors such that detection surfaces of the
semiconductor detectors are oriented towards an object plane of the
objective lens. According to exemplary embodiments herein, the
X-ray detector comprises more than two semiconductor detectors,
such as, for example, three, four, eight or more semiconductor
detectors. According to some embodiments, the detection surfaces of
the plural semiconductor detectors may be arranged in a common
plane. According to other embodiments, the semiconductor detectors
and the detection surfaces thereof may be shaped as sectors, such
that the plural detection surfaces together substantially fill a
circular surface having a central aperture allowing the primary
particle beam to traverse the X-ray detector.
[0012] According to further embodiments, a particle beam system
comprises a particle source for generating a primary particle beam,
an objective lens for focusing the primary particle beam in an
objective plane, an electron detector for detecting electrons
originating' from an inspected object, and an X-ray detector
including a first semiconductor detector having a detection surface
oriented towards the object plane. The particle beam system may
further comprise an actuator and a first membrane, wherein the
actuator is configured to move the first membrane back and forth
between a first position and a second position, wherein the
membrane is disposed between the semiconductor detector and the
object plane when it is located in the first position, and wherein
the first membrane is not located between the semiconductor
detector and the object plane. When the first membrane is not
located between the semiconductor detector and the object plane,
X-rays generated by the primary particle beam at the object can be
incident on the detection surface of the semiconductor detector
without having to traverse the membrane. On the other hand, when
the first membrane is located between the semiconductor detector
and the object plane, X-rays generated by the primary particle beam
at the object have to traverse the membrane to reach the detection
surface of the semiconductor.
[0013] The first membrane which can be selectively disposed between
the first semiconductor detector and the object plane has a
transmittance for electrons which is smaller than 1. It is both
possible to vary a detection sensitivity for secondary electrons of
the semiconductor detector by placing the first membrane in front
of the semiconductor detector and by removing the membrane from its
position in front of the semiconductor detector. Similar to the
embodiment having two different membranes located in front of two
different semiconductor detectors, it is thus possible to perform
two subsequent measurements of detection events, wherein the two
measurements differ with respect to the transmittance for
electrons. From these two measurements it is possible to determine
an amount of detection events caused by X-rays with a relatively
high accuracy.
[0014] According to an exemplary embodiment herein, a second
membrane is provided which is also coupled to the actuator, wherein
the second membrane is positioned in front of the semiconductor
detector when the first membrane is not positioned in front of the
semiconductor detector, and vice versa.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The forgoing as well as other advantageous features of the
invention will be more apparent from the following detailed
description of exemplary embodiments of the invention with
reference to the accompanying drawings. It is noted that not all
possible embodiments of the present invention necessarily exhibit
each and every, or any, of the advantages identified herein.
[0016] FIG. 1 is a schematic illustration of a particle beam
system;
[0017] FIG. 2 is a sectional view along a line II-II in FIG. 3 of
an X-ray detector of the particle beam system shown in FIG. 1;
[0018] FIG. 3 is an elevational view of a bottom of the X-ray
detector shown in FIG. 2;
[0019] FIG. 4 is a graph illustrating a transmittance for electrons
of membranes of the X-ray detector shown in FIGS. 2 and 3;
[0020] FIG. 5 shows a graph illustrating a transmittance for X-ray
radiation of the membranes of the X-ray detector shown in FIGS. 2
and 3;
[0021] FIG. 6 shows a graph illustrating count rates detected by
the X-ray detector shown in FIGS. 2 and 3;
[0022] FIG. 7 is a schematic illustration of a portion of a
particle beam system; and
[0023] FIG. 8 is an elevational view from the bottom of a particle
beam system.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0024] In the exemplary embodiments described below, components
that are alike in function and structure are designated as far as
possible by alike reference numerals. Therefore, to understand the
features of the individual components of a specific embodiment, the
descriptions of other embodiments and of the summary of the
invention should be referred to.
[0025] FIG. 1 is a schematic illustration of an exemplary
embodiment of a particle beam system 1. The particle beam system 1
comprises an electron beam source 5 having a cathode 7 and
extractor and suppressor electrodes 9 for generating a primary
particle beam 13. The primary particle beam 13 traverses a
condenser lens 11, an aperture 15 provided in an electron detector
17, and an objective lens 19 for focusing the primary particle beam
13 at a location 21 in an object plane 23. A surface of an object
25 to be inspected is disposed in the object plane 25.
[0026] The objective lens 19 comprises a ring coil 27 provided in a
ring-shaped yoke having a ring-shaped upper pole piece 31 and a
ring-shaped lower pole piece 32 such that a ring-shaped gap is
formed between the upper and lower pole pieces 31, 32. A magnetic
field for generating the electron beam 13 is generated in this
gap.
[0027] The particle beam system 1 further includes a beam tube 35
which enters and partially traverses the objective lens 19.
[0028] An end electrode 37 is provided at a bottom end of the beam
tube 35. A terminal electrode 36 is disposed between the end
electrode 37 and the object plane, wherein an electrostatic field
generated between the end electrode 37 and terminal electrode 36
provides a focusing power on the primary electron beam 13. The
focusing power provided by the electrostatic field between the
electrodes 36 and 37 and the focusing power provided by the
magnetic field between the pole pieces 31 and 32 commonly provide
the focusing power of the objective lens 19 of the particle beam
system 1.
[0029] A controller 39 is provided for supplying suitable voltages
to the terminal electrode 36, the end electrode 37, the cathode 7
and the extractor and suppressor electrodes 9 such that an electron
beam focus is formed in the object plane.
[0030] These voltages can be selected such that the electrons of
the primary electron beam have a predetermined kinetic energy when
they are incident on the object 25 at location 21. It is in
particular possible that the controller 39 supplies a voltage
corresponding to ground potential or a voltage differing from
ground potential to the terminal electrode 36.
[0031] The objective lens 19 further includes deflectors 41 which
are also controlled by the controller 39 for deflecting the
electron beam 13 and for varying the location 21 at which the
primary electron beam 13 is incident on the object 25 in the object
plane 23. By deflecting the primary electron beam it is in
particular possible to systematically scan the primary particle
beam across a portion of the surface of the object 25.
[0032] The primary particle beam incident on the object 25 results
in that secondary electrons emerge from the object 25. A portion of
such secondary electrons may enter into the beam tube 35 such that
they are detected by the electron detector 17. In the context of
the present application, the term secondary electrons comprises all
types of electrons which are caused to emerge from the object by
directing the primary particle beam onto the object and which can
be detected by the electron detector 17. The term secondary
electrons in particular includes backscattered electrons having a
kinetic energy which corresponds to or is somewhat smaller than the
kinetic energy of the primary particles incident on the object. The
term further includes secondary electrons having, when they emerge
from the surface of the object, a kinetic energy which is
substantially smaller than the kinetic energy of the primary
particles upon their incidence onto the object. FIG. 1
schematically shows an exemplary trajectory of a secondary electron
which is incident on the electron detector 17 at reference numeral
43.
[0033] The particle beam system 1 further comprises an X-ray
detector 47 disposed in between of the objective lens 19 and the
object plane 23. The X-ray detector 47 comprises a central aperture
49 allowing the primary particle beam 13 and secondary electrons 43
to traverse the X-ray detector 47. The X-ray detector 47 comprises
plural detection surfaces 51 for X-ray detection, wherein the
plural detection surfaces 51 are located at a radial distance from
a main axis 12 of the objective lens. The X-ray detector 47 is
provided for detecting X-rays generated by the primary particle
beam 13 incident on the object. An exemplary trajectory of an X-ray
generated by the primary electron beam 13 at location 21 and
incident on the X-ray detector 47 is indicated in FIG. 1 at
reference numeral 53.
[0034] A configuration of the X-ray detector 47 is illustrated as a
sectional view in FIG. 2 and as an elevational view in FIG. 3. The
X-ray detector 47 comprises a ring-shaped carrier including an
upper plate 55 having a central bore for providing the aperture 49
allowing the primary particle beam 13 and the secondary electrons
43 to pass through. Four semiconductor detectors are attached to a
bottom surface of plate 55 such that a detection surface 59 of each
semiconductor detector 57 is oriented towards the object plane 23.
A membrane or window 61 is mounted in front of the detection
surface 59 of each semiconductor detector 57. The membranes 61 have
a function to at least partially prevent incidence of secondary
electrons on the detection surfaces 59 of the semiconductor
detectors 57. In the exemplary embodiment shown in FIG. 2, the
membrane 61 is disposed at a small distance from the detection
surface 59. It is, however, also possible that the membrane
contacts or is directly attached as a membrane layer to the
detection surface of the semiconductor detector and such that the
membrane is carried by the semiconductor detector.
[0035] The membranes 61 can be configured such that they are not
fixedly attached to the semiconductor detector or the ring
structure such that they can be readily removed and replaced by
other membranes. The exemplary embodiment shown in FIGS. 2 and 3
has axial projections 63 provided on the plate 55. The projections
63 include radially extending portions 65 adapted to carry the
membranes 61 such that they are mounted on the X-ray detector 47.
For example, the membranes 61 can be clamped between the radial
projections 65 and an outer axial ring-shaped projection 66
provided on the plate 55.
[0036] In the embodiment shown in FIGS. 2 and 3, the X-ray detector
57 comprises four separate semiconductor detectors arranged in a
configuration of four quadrants distributed around the aperture 49.
The four semiconductor detectors 57 each have a same configuration
and same properties, and detection signals of the four
semiconductor detectors 57 are separately received by the
controller 39.
[0037] The four membranes 61 arranged in front of the detection
surfaces 59 of the four semiconductor detectors have different
properties. Two different types of membranes are provided. Two
membranes which are indicated by reference numeral 61 in FIG. 3
have a transmittance for secondary electrons which is greater than
a transmittance for secondary electrons of the two other membranes
which are indicated in FIG. 3 with reference numeral 61'.
[0038] The two different types of membranes having different
transmittances for secondary electrons are provided to reduce a
detection efficiency for secondary electrons of the X-ray detector,
while a detection efficiency for X-rays is not substantially
reduced. The membranes having the differing transmittances for
secondary electrons can be in particular used for determining an
amount of detected secondary electrons and to determine a remaining
amount of detected X-rays. This may improve an accuracy of X-ray
detection.
[0039] The membranes 61 are made from a material including elements
having a low atomic number such that a transmittance for X-rays is
high. All membranes can be made from the same material and have
different thicknesses for providing the different transmittances
for secondary electrons. The membranes can be made of polyester,
for example. Examples of suitable polyesters include
terephtalat-polyester, such as polyethylenterephtalat-polyester.
Suitable membranes can be obtained from the company DuPont,
Wilmington, USA under the product name Mylar. Suitable thicknesses
of the membranes can be, for example, within a range from 0.1 .mu.l
to 50 and in particular from 1.0 .mu.m to 10 .mu.m. Other suitable
membranes can be obtained from the company MoxTek, Orem, USA under
the product name AP3.3. Still further membranes can be made of
beryllium, for example.
[0040] In an exemplary embodiment illustrated with reference to
FIGS. 4 and 5 below, a membrane having the greater transmittance
for electrons is provided by a foil having a thickness of 1 .mu.m
made of the material AP3.3, and a membrane having a lower
transmittance for electrons is made of a foil of a thickness of 6
.mu.m of the material Mylar.
[0041] FIG. 4 shows a graph representing transmittances for
electrons in dependence on kinetic energy of the electrons for the
two membranes obtained by numerical simulation.
[0042] FIG. 5 shows a graph representing transmittances for X-rays
in dependence on kinetic energy of the electrons for the two
membranes obtained by numerical simulation.
[0043] In the example illustrated with reference to FIG. 6 below, a
membrane having the greater transmittance for electrons is provided
by a foil of a thickness of 1 .mu.m of Mylar material, and a
membrane having the smaller transmittance for electrons is provided
by a foil having a thickness of 6 .mu.m of the same Mylar
material.
[0044] FIG. 6 shows graphs representing count rates measured in an
experiment using the semiconductor detectors 47 of the particle
beam system 1 shown in FIG. 1. In this experiment, the primary
particle beam is directed onto a sample made of manganese (Mn). The
graphs shown in FIG. 6 illustrate a number of detection events
recorded in a given time by the semiconductor detector having the
thin foil located in front of it and a number of detection events
recorded at the given time by the semiconductor detector having the
thick foil located in front of it. Each graph is plotted in
dependence on a kinetic energy of primary particles incident on the
sample. From FIG. 6 it appears that the count rates for the thin
membrane and for the thick membrane differ with respect to their
dependency on energy such that it is possible by a further analysis
to derive additional information from the detection signals. It is
in particular possible to determine an amount of detection signals
caused by detected X-rays.
[0045] In the example illustrated above, the X-ray detector
comprises four separate semiconductor detectors. It is, however,
also possible to use a number of semiconductor detectors which
differs from four. Two, three, five, six or more semiconductor
detectors can be used, for example. Two different types of
membranes having different transmittances for secondary electrons
are used in the exemplary embodiment illustrated above. It is,
however, also possible to use a higher number of membranes having
different transmittances for secondary electrons. For example,
three or more membranes having different transmittances for
secondary electrons can be used.
[0046] Detection signals generated by the semiconductor detectors
57 and detection signals generated by the electron detectors 17 are
supplied to the controller 39. Electron microscopic images can be
generated from the detection signals of the semiconductor detectors
and from the detection signal of the electron detector. This can be
achieved by controlling the deflectors 41 such that the primary
particle beam 13 is scanned to different locations 21 on the sample
25 and by recording detected intensities in correspondence with the
respective locations. The obtained images can be displayed on a
monitor 81, and a controller 39, which may comprise a computer, can
be controlled by a suitable input device, such as a keyboard 82.
The controller may include a module to analyze the varying
detection signals. In particular, the detection signals obtained
from the semiconductor detector having the membrane 61 located in
front of it and the detection signals from the semiconductor
detector having the membrane 61' located in front of it, and the
detection signals obtained from the electron detector 17 can be
compared and analyzed relative to each other for obtaining derived
measurement values from the detection signals. Such derived
measurement values can also be displayed in dependence on the
respective locations 21 as images.
[0047] FIG. 7 shows a further example of a particle beam system.
The particle beam system 1a shown in FIG. 7 has a similar
configuration as the particle beam system illustrated above with
reference to FIGS. 1 and 6. The particle beam system 1a again
comprises an objective lens 19a having an X-ray detector 47a
located in front of it. The X-ray detector 47a comprises a
semiconductor detector 57 having a detection surface, wherein a
membrane 61a is located in front of the detection surface and
between the detection surface and an object plane of the objective
lens 19a. A membrane 73 is mounted on a ring-shaped carrier 71
provided between the X-ray detector 47a and the object plane 23a.
The carrier 71 is mounted on a rod 75 extending through a wall 77
defining a vacuum space in which the objective lens 19a is
arranged. A motor 81 is provided as an actuator which is controlled
by a controller not shown in FIG. 7 and corresponding to controller
39 shown in FIG. 1. The rod 75 can be displaced back and forth in a
longitudinal direction of the rod 75 by operating the actuator 81,
as indicated by a double arrow 83 in FIG. 7. It is thus possible to
arrange the membrane 73 in a first position in front of the
detector 47a, and to arrange the membrane in a second position in
which it is not disposed between the detector 47a and the object
plane 23. In the first and second positions, the membrane 73
provides different transmittances for electrons such that it is
possible to change a detection characteristic of the semiconductor
detector for X-ray radiation by controlling the actuator 81.
[0048] The membrane 61a, which is carried by the X-ray detector 47a
in the exemplary embodiment illustrated in FIG. 7 can be omitted,
while the detection efficiency of the semiconductor detector for
electrons can still be changed by displacing the membrane 73 under
the control of the actuator 81.
[0049] FIG. 8 is a partial view of a further exemplary embodiment
of a particle beam system, wherein the particle beam system 1b
shown in FIG. 8 is similar to the particle system illustrated with
reference to FIG. 7 above. FIG. 8 is an elevational view from the
bottom of an X-ray detector 47b as it can be seen from an object
plane (see reference numeral 23a in FIG. 7) of an objective lens of
the particle beam system 1b. Membranes 73b and 73b' mounted on a
carrier 71b can be selectively positioned in front of an X-ray
detector 47b. The carrier 71b is mounted on a rod 75b which can be
displaced by an actuator (not shown in FIG. 8) as indicated by a
double arrow 83b in FIG. 8. The membranes 73b and 73b' differ with
respect to a transmittance for secondary electrons. In the example
shown in FIG. 8, the X-ray detector 47b includes four semiconductor
detectors, wherein each of the semiconductor detectors has a
detection surface 59b. An additional membrane can be provided in
front of some or more of the detection surfaces. If two or more
membranes are provided in front of the detection surfaces, they can
also differ with respect to their transmittance for secondary
electrons. It is also possible to provide a number of semiconductor
detectors which is different than four. It is in particular
possible, to provide only one single semiconductor detector while
still providing the possibility of obtaining measurements at
different transmittances for secondary electrons since different
membranes 73b and 73b' are mounted on the carrier 71b. The
membranes 73b and 73b' differ with respect to their secondary
electron transmittances and can be selectively positioned in front
of the X-ray detector.
[0050] In the embodiment shown in FIG. 8, it is also possible that
only the membrane 73b is mounted on the carrier 71b while the
membrane 73b' is omitted. With such configuration it is still
possible to obtain two measurements differing with respect to the
secondary electron transmittance, if the carrier 71b is
reciprocated between its two positions.
[0051] The one or more membranes mounted on the carrier in the
embodiments illustrated with reference to FIGS. 7 and 8 above can
be made of materials and thicknesses as illustrated with respect to
the membranes 61 in the embodiments illustrated with reference to
FIGS. 1 to 6 above.
[0052] It is further possible to arrange the motor providing the
actuator within the wall 77 and inside the vacuum space.
[0053] It is further possible that the actuator is a manually
operated actuator rather than an actuator operated by a motor.
[0054] In the embodiments illustrated above, the particle beam
system is an electron beam system in which an electron beam is used
as the primary particle beam for releasing electrons and X-rays
from a sample. It is, however, also possible that an ion beam
rather than the electron beam is used as the primary electron beam
to release electrons and X-rays from the sample. Examples of
suitable systems for generating an ion beam as the primary particle
beam are known from US 2007/0228287 A1 and US 2007/0215802 A1,
wherein the full disclosure of these documents is incorporated
herein by reference.
[0055] According to embodiments, there is provided a particle beam
system comprising a particle beam source for generating a primary
particle beam, an objective lens for focusing the primary particle
beam, an electron detector and an X-ray detector. The X-ray
detector comprises one or more semiconductor detectors having
detection surfaces oriented towards a sample. One or more membranes
can be selectively provided between the one or more detection
surfaces and the sample. If two or more membranes are provided,
they may differ with respect to a transmittance for secondary
electrons.
[0056] While the invention has been described with respect to
certain exemplary embodiments thereof, it is evident that many
alternatives, modifications and variations will be apparent to
those skilled in the art. Accordingly, the exemplary embodiments of
the invention set forth herein are intended to be illustrative and
not limiting in any way. Various changes may be made without
departing from the spirit and scope of the present invention as
defined in the following claims.
* * * * *