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]