tem fuer web - HTSKOREA 홈페이지에 오신걸 환영합니다!. K öhler, G. Irmer, L. Bishoff, J. Teichert TEM specimen preparation.. mashining of TEM - lamella ion beam region

TEM Specimen Preparation by Focused Ion BeamSputtering - Optimisation of the Process

B. Köhler, G. Irmer, L. Bishoff, J.Teichert

- Außens telle EADQ Dresden -

Forschungszentrum Rossendorf e.V.Institut für Ionenstrahlphysik und MaterialforschungPostfach 510 119, D-01314 Dresden

machining of T EM lamella with Focused Ion Beamsputtering

advantages:

high positioning accuracylittle restriction on samle materials tress free-millingobservation of progress (SE M or S IM)

B . Köhler, G. Irmer, L . B ishoff, J . T eichert T E M specimen preparation..


mashining ofT EM - lamella

region of

interest

initial specimen



region of

interestpre-prepared

specimen

initial specimen



region of

interest

TEM-observation

direction

pre-prepared

specimen

initial specimen



ion beam

region of

interest

TEM-observation

direction

pre-prepared

specimen

initial specimen



ion beam

region of

interest

TEM-observation

direction

pre-prepared

specimen

initial specimen

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Example: lamella in a fracture mechanique specimen

Inclusion, which was thereason for the fracture


inclusion

levelingB . Köhler, G. Irmer, L . B ishoff, J . T eichert T E M specimen preparation..


S i - lamella

(T U DD)


T EM images

S i - lamella

(T U DD)


T EM images

S i - lamella

(T U DD)

2 µm


T EM images

S i - lamella

(T U DD)

2 nm

machining of T EM lamella with Focused Ion Beamsputtering

advantages:high pos itioning accuracylittle res triction on sample materials tress free-millingobservation of progress (S EM or S IM images)


poss ible problems /disadvantages:amorphisationcontamination of the sample by Ga (at leastin the machined area)bending of the lamella due to s tress release


Example for bending:


aim varied parameter

avoidcontamination with Ga

substitute sourceGa Í S i , ...

reduce the thickness of the amorphisation layer

angle of incidenceenergyion mass

speed of machining (sputter efficiency)

sort of ions ,energy, current

reduce bending of lamella additional cuts for s tress relaxation


influence of the ion angle

can the penetration depth ( ==> the thickness of the of the dis turbed layer) reduced?

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influence of the ion angle

can the penetration depth ( ==> the thickness of the of the dis turbed layer) reduced?

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GDPDJHGUDQJH

0 20 40 60 80-50

0

50

100

150

200

250

300

350

400

450

500

Si (30 keV) into Si

cos(α) * depth (0) is a good fit only for small α

dept

h / A

°

α

Monte Carlo s imulation (S R IM J. F . Z iegler, IBM)


0 30 60 90

100

200

300

400

500 Au 30kV Au 10kV Ga 10kV Ga 30kV Si 10kV Au 8kV Si 8kV Si 30kV

proj

ecte

d ra

nge/

°A

incident angele

S imulation:


s imulation results require experimental verification !

R aman Spectroscopy


triple mono-chromator

CCD

mirror

laser

polarisator

analysator

beamsplitter

microskopeobjective

sample

cryostate xy

spatial filter

T64000Jobin-YvonMicro-Raman-Spectrometer

table

sample

cryostate

mirror

macrochamber

microscope


R aman-meas urement of the thickness of the amorphous layer

IL Ic1

αc

200 400 600Raman shift (cm-1)

0

200

400

600

800

x 20c-S i

d

IL

Ia

Ic2

αc

αa

0

40

80

Cts

/s

x 20c-S i

a-S i


200 400 600Raman shift (cm-1)

0

200

400

600

800

0

40

80

Cts

/s

0

1

2

3

c-Si

x 20

x 20

sputtered area

portion of the amorphous layerS i wafer,sputtered with Ga ions(30 keV, 3°)


IL ILIc1

Ia

Ic2

d

αc αc

αa

measured intensities :

Ic1 : crystalline material onlyIa : from the amorphous layerIc2 : from crystalline material below the amorphous layer

a2 da ca

a cc2

I e 1I

α

β α= −α β

a2 dac2

cc1

I (1 r ) eI (1 r )

− α−= −c ar , r

c a,β βc a,α α - absorption cross section

- Raman scattering cross section

- reflection coefficients

Solving for the thickness d:

c a

a c2 a c1

c c2a c c1

c c2

1 r I

1 r I 1 r Id ln

1 r II1

I

− − −

= − β α − β

a c a c1

c c c 2a

a

c2

1 r I1

1 r I

I

I

β α − − β − α =


S i Wafer with machined areas in the light microscope

c-S i

measurement points :

1: 6 ° 2: 0° 3: 3°


Comparison of firs t results : Ga penetration depth by S RIM s imulation

<-> amorphisation thickness by Raman measurements

E nergy: 30 keV

angle of range (S R IM) measured amorphis ation layer

incidence thickness d

0 ° 6.9 (extrapolated) 7.0 nm

3° 7.3 nm 7.5 nm

6° 7.7 nm 7.2 nm

9° 8.2 nm --


for use of other beam ions than Ga

•alloy sources and

•an ion column with a mass filter

must be available


imaging system

Ion source

condenser

blanking plates

extractor

Wien filter (ExB)

(selection of ionsby mass)

lens

X,Y- deflection plates

specimen

secundary electron detector

precursor gas injector

principle of the

F IB 4400

source

control

blanking

control

scan

generator

amplifier

it includes a mass filter

sys tem dual beam

chamber 4 “s tage eucentric (6 axis )imaging detection of secondary electronsF IB : CANION 31Z

ions Ga, Au, S i, Gemass selection m/∆m=35energy 0 ...30 keVcurrent 1 pA ... 20 nAresolution 10 nm

precursor gases W, F -, Cl-

S E M: L E O 440filament W, Lab6

E DX R öntec

special access to software interfaceproxy writer

Parameters of the F IB4400

B . Köhler, G. Irmer, L . B ishoff, J . T eichert T E M specimen preparation.. B . Köhler, G. Irmer, L . B ishoff, J . T eichert T E M specimen preparation..

developed source module


image taken with an Au Ge S i

beam

Cross over mode

I = 1 nA


S ummary:

• lowering the energy reduces the penetration depth (thinner contamination +amorphisation layer),

• reducing the angle between ion beam and surface to small values hasnegligible effect to the penetration depth

• varying the ion specimen gives an additional free parameter for optimisation (highsputter yield for heavy ions, e.g. Au, small penetration depth)

• working with a S i beam should avoid the contamination problem in S i waferapplications

• an AuGeS i alloy source has been ins talled success fully at the F IB 4400

• in the mixed ion vers ion the alloy source works satis factory

What remains to do / next s teps :

• detailed tes t of the alloy AuGeS i source

• experimental (F IB + Raman) verif ication of the S R IM results

Documents

tem fuer web - HTSKOREA 홈페이지에 오신걸 환영합니다!. K öhler, G. Irmer, L. Bishoff, J. Teichert TEM specimen preparation.. mashining of TEM - lamella ion beam region