Overview:
In many applications the
combination of optical/structural
and analytical imaging of the same
target at the same time is desirable.
In an electron microscope a
focused electron beam is used for
optical imaging. For nano-scale
surface processing and advanced
structural imaging a primary
focused ion beam (FIB) is used. The
FIB produces a small amount of
secondary ions, which can be used
for spatially resolved mass
spectrometry.
Challenges:
• Limited space
• Low secondary ion beam
currents (typical 1 … 5 pA)
• Broad kinetic energy distribution
of the secondary ions
• Difficult vacuum conditions
Approach:
• Helium cooling section to
minimize energy distribution
width
• Extraction lens configuration [1]
• Axial segmented linear
quadrupole trap made in planar
technology [2] for ion transfer
• Pressure stage incorporating a
quadrupole ion wave guide for
ion transfer between different
pressure regions
• 3D-Ion trap used in Fourier
Transform mode as mass
analyzer
Introduction 3D-Ion TrapPrinciple of Operation
Metrological Characterization of a Sensitive Secondary Ion Mass Spectrometer for
Electron Microscopes to Combine Optical/Structural and Analytical Imaging
Alexander Laue, Albrecht Glasmachers, Albrecht Brockhaus; University of Wuppertal, Germany
Michel Aliman, Hubert Mantz; Carl Zeiss NTS GmbH, Oberkochen, Germany
Cross Section of the SIMS Device
ReferencesPreikszas, D.; Aliman M.; Mantz, H.; Laue, A.; Brockhaus, A.;
Glasmachers, A. Optimization of the collection efficiency of
secondary ions for spartially resolved SIMS in Crossbeam devices, 12th
International seminar on Recent Trends in Charged Particle Optics and Surface Physics Instrumentation, 2010
Glasmachers, A.; Laue, A.; Brockhaus, A.; Puwey, A.; Aliman, M. Planar
technologies for optimized realizations of quadrupole ion guides and
quadrupole ion wave guides, 58th ASMS Conference, 2010
Laue, A.; Glasmachers, A. New Design of a Compact Fourier-Transform
Quadrupole Ion Trap for High Sensitivity Applications, 57th ASMS
Conference, 2009
Patent application EP11152379.1 – 1232: Apparatus for focusing and for
storage of ions and for separation of pressure areas, 2011
Patent application EP11152420.3 – 2208: Apparatus for transmission of
energy and/or for transportation of an ion as well as particle beam
device having an apparatus such as this, 2011
IonGuide
IonGuide
Compact and fully integrated SIMS-device
Methods for Stage-by-Stage Characterization
• System dimensioning of the complete transfer chain using SimIon
• Hard sphere model to simulate collisions and cooling efficiency
I. Secondary ions are continuously generated by the FIB
II. Secondary ions are accelerated into the SIMS orifice [1]
III. Ions are cooled and bunched in the IonGuide
IV. Ions are accumulated and sequentially transferred/pulsed into the
mass analyzer (3D-trap)
V. Ions are analyzed by measuring their influence charge on the cap
electrodes [3]
WaveGuide
Ionization:
electron beam ionization (tungsten
filament) of Argon/Krypton outside
the SIMS device. IonGuide used for
ion transfer to WaveGuide
Ion detection:
Cup electrode of 3D-trap used as
Faraday-Cup
3D-Trap
Ionization:
266nm UV Laser for in-situ ion
generation of vapor phase
converted aromatic hydrocarbons
Ion detection:
Measuring the influence charge of
trapped ions
IonGuide
Ionization:
electron beam ionization (tungsten
filament) of Argon/Krypton outside
the SIMS device
Ion detection:
WaveGuide electrode used as
Faraday-Cup
WaveGuide
WaveGuide
Mass Analyzer
Conclusions
Transient signal and spectrum of in-
situ generated benzene-ions
• WaveGuide: Enables transfer of cooled
and bunched ions between different
pressure regions
• IonGuide: Kinetic energy equilibrium
depends on DC ramp of the IonGuide
• IonGuide: High helium pressure minimizes
kinetic energy distribution of ions
• 3D trap: Compact and highly efficient
wideband mass analyzer
• SIMS: Complete chain tested under
typical lab conditions → proof of concept
adduced
Future work:
• Improve and extend low mass range
• Improve pressure stages to enable high
resolution measurements (longer signal
transients)
• Improve dynamic mass range
mass spectrum of FIB sputtered ions
(complete transfer chain)
HV amplifier
ch
arg
ea
mp
lifie
r
valve
Sequence Control System
UV-Laser
sample gas
bend-voltage:+12 V
WaveGuide control unit
System potentials
extr
ac
t
co
ol
tra
nsf
er
an
aly
ze
FIB
target
microscope
chamberP < 5×10-6 mbar
analysis chamberP < 5×10-6 mbar
cooling stage (Helium)P = 1×10-2 … 5×10-3 mbar
pumppump
pump
University of Wuppertal, Germany
Institute for Pure and Applied Mass Spectrometry
athmosphere
• Ions are shifted and pulsed into the 3D-trap
• High pulse amplitudes → strong signals
• Ions are transferred with different shift frequencies
• Shift frequency does not affect transfer efficiency
• DC ramp affects kinetic
energy equilibrium
• High DC ramps → high
kinetic energy
• Low helium pressure causes
broad kinetic energy
distributions
• Measurements show higher
kinetic energy than
numerical simulations
• Difficult to determine field
distortion- and RF-effects
0 10 20 5030 40 60 70 80 90 100
200
300
100
0
-100
200
300
400
Tra
nsi
en
t si
gn
al [
mV
]
Time [ms]
0 10 20 5030 40 60 70 80 90 100
Frequency [kHz]
Arb
itra
ry u
nit
30 40 50 8060 70 90 100 110
Frequency [kHz]
Arb
itra
ry u
nit
Noise signalIon signal
Charge amplifier
Electrometer
DC-bias(variable)
DC-offset
DC-ramp
IonGuide
WaveGuide
0 50 100 250150 200 300 350
z-axis [mm]
Kin
etic
en
erg
y [
eV
]
-1 V DC ramp<Ekin,z> = 0.12 eV<collisions> = 92
-15 V DC ramp<Ekin,z> = 2.1 eV<collisions> = 48
5 × 10-3 mbar1 × 10-2 mbar
MeasurementSimulation
Kinetic energy at IonGuide outlet [eV] Kinetic energy at IonGuide outlet [eV]
0 5 10
Arb
itra
ry u
nit
0
10
20
30
40
50
60
70
0
10
20
30
40
50
60
70
80
90
Cooling efficiency at constant pressure (PHe = 1 × 10-2 mbar) Kinetic energy distribution at different pressures Comparison of kinetic energy distributions
400 15
100 60
0
10
20
30
40
50
Arb
itra
ry u
nit
-0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
0 0.5 1.0 2.51.5 2.0 3.0 3.5
time [ms]
0 0.5 1.0 2.51.5 2.0 3.0 3.5
time [ms]
-100 -50 500 100 150
time [µs]
-100 -50 500 100 150
time [µs]
Different pulse amplitudes Different shift frequencies
-8 -7 -6 -2-5 -3 -1 2
time [ms]
-4 0 1
-8 -7 -6 -2-5 -3 -1 2
time [ms]
-4 0 1
1
0
-1
-5
-3
-4
-2
-6
Vo
lta
ge
[V
]
200
100
-300
-100
-200
0
-400
Vo
lta
ge
[m
V]
200
100
-300
-100
-200
0
-400
Vo
lta
ge
[m
V]
200
100
-500
-200
-400
-100
-600
Vo
lta
ge
[m
V]
300
0
-300
200
100
-500
-200
-400
-100
-600
Vo
lta
ge
[m
V]
300
0
-300
0
-5
-20
-15
-10
-25
Vo
lta
ge
[V
]
[1]
[2]
[3]
[4]
[5]