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Contamination Free

TEM Specimen Preparation

Contamination Free

TEM Specimen Preparation

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TEM Specimen Requirements

Thin

Representative of the bulk

Uniform thickness

Flat

Rugged

Conducting Clean

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Topics

Electropolishing > Model 110 Twin Jet EP

Disk cutting > Model 170 Ultrasonic Disk Cutter

Sample grinding > Model 160 Specimen Grinder

Dimple grinding > Model 150 Dimpling Grinder Ion milling > Model 1010 LAMP Ion Mill

Plasma cleaning > Model 1020 Plasma Cleaner

Mechanical preparation methods

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Cut a slice

Diamond saw

Damage ~ 100 m

Acid saw Wire saw

Cleaving as with silicon wafers

Initial Thinning

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Site specific cutting of specimen disks Fast

Cutting by mechanical grinding removalof material

Rate dependent on abrasive (SiC, CBN) Automatic termination of cutting

Ultrasonic Disk Cutting

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Take cut disk down to

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Dimple GrindingDimple Grinding

Location specific thinning

Selected location

Reduces ion milling time

Creates thin center thick edge

Sample is more robust

Easier to handle

Single or double sided dimpling

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Dimple Grinding

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Cross-Section of a Dimple

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Dimpling rate Abrasive size

Lubricant

Wheel speed Wheel pressure

Dimple geometry Round

Oblong

Important Dimpling Parameters

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Cross-Sectional TEM (XTEM)

Semiconductor industry Study microstructure of each layer in an

integrated circuit

Thin film thickness Computer hard drives

Interface science Multiple sections in one

XTEM specimen

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XTEM Step-by-Step - I

Cleave small section of wafer to work with

Mount to ultrasonic disk cutter specimenplate Face up (blank) or face down (with pattern)

Face up cover surface with thin glass cover sideto protect surface during cutting process

Cut out desired sections

Remove cover slips and discard. Removesections from specimen plate

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Wafer Mounting and Cutting

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XTEM Step-by-Step - II

Remove sections from specimen grinder andsoak and rinse several times

Create stack

Three thick dummy pieces on each endsandwiching sections in between. Innermostdummy pieces can be unthinned real material.

Place dummy pieces and sections into teflonchuck, placing droplet of epoxy on each piece

Clamp stack in vise and place on hot plate to cure

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Create Stack

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XTEM Step-by-Step - III

Core stack

Ultrasonically cut 2.3 mm diameter cylinderfrom stack

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Core Stack

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XTEM Step-by-Step - IV

Place core into 3 mm brass tube, epoxy into

place and cure Slice 3 mm disks from brass tube

Place disks on specimen grinder and polish

away damaged region from both sides ofdisk.

Dimple cross-section Ion mill to electron transparency

Plasma clean in Ar/25%O2 ( 2 5 min.)

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Interface

Place Stack in Tube & Slice

RegionofInterest

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Rough grind with 600 grit SiC paper

Step down grinding/polishing with diamondfilms 30 m, 15 m, 9 m, 6 m, 3 m, 1 m,

0.5 m

Final polish with colloidal silica

Flip over and repeat on secondside, finishing with specimen< 100 m thick

Grind 3mm Disk

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19 Piece Cross Section

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Ion Milling

Non-reactive ions directed at specimen

Thinning by momentum transfer

Thinning rate dependent upon:

Relative mass of thinning ion and specimenatom ion energy

Specimen crystal structure Angle of incidence of ion beam

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Ion MillingIon Milling

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High Angles

Angles >15

Leads to surface topography as a functionof atomic number

Rapid thinning

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Low Angles

Angles < 15 Leads to flat surface but slower thinning

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Energy

Higher energies

Thinning rates decreased for some materials

Implantation

Amorphous layers Point defects

Propagated artifacts

Lower energies Thinning rates more predictable

No / reduced damage to specimen

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Temperature

Without cooling Heat sample to as high as 200C Changes in phase chemistry

Changes in sample chemistry Mobility of defects increases

Structural changes

Differential / preferential milling

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Hollow Anode Discharge Ion Source

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Ion Milled Ca dopedIon Milled Ca dopedYBaCuOYBaCuO (123)(123) BicrystalsBicrystals

Y/BaCu/O

350 400 450 500 550 6000

20

40

60

80

100

energy-loss (eV)

intensity(electrons)x10

00

Ca-LCa-L2,32,3

O-KO-KO-K

at dislocation core

3nm away from grain boundary

at dislocation core

3nm away from grain boundary

Chemical composition

at dislocation core

Ca/O = 0.1atom%

Chemical compositionChemical composition

at dislocation coreat dislocation core

Ca/O = 0.1atom%Ca/O = 0.1atom%

Cour tesy of Dr.Cour tesy of Dr. GerdGerd DuscherDuscher and Jul ia Luck, ONRLand Jul ia Luck, ONRL

ADF STEM Image EELS Spectra

I Mill d XTEM f TiI Mill d XTEM f Ti SiSi O l iO t l t i

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Ion Milled XTEM of TiIon Milled XTEM of Ti--SiSi OptoelectronicOptoelectronic

SiO2(CVD)

TiN (CVD)

/TiSi2

Via

1.0 m

SiO2(Grown)

Si

TiN(CVD)

/ Ti

Court esy of I van Petrov and Young Kim, Universit y of I l l inois

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Ion Milled X-TEM Sample

Polycrystalline copper film onepitaxial Ti0.5W0.5 N/TiN

superlattice on MgO (001)

ll d f /I Mill d XTEM f C /R L i

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Ion Milled XTEM of Co/Ion Milled XTEM of Co/RuRu LatticesLattices

HREM image show ing alt ernat ingmonolayers of Co and Ru w ithin the

Co / Ru ordered superlatt ice

(0002)Rumonolayers(largeratoms)

(0001) Co

Court esy by Kazuhi ro Hono & D. H. Ping, Nat ional Research I nstit ut e for Metals

Imaging of LaTiO3 Multilayers

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Imaging of LaTiO3 Multilayers

2 nm

1

2

3

456

2 nm

Wedge polishing, followed by IBEat low incident angle, low ion energy

and low temperature LaTiO3 multilayers in SrTiO3imaged in a FE TEM

Material (in box) thin enough forADF lattice imaging over 0.4 mfield of view

Courtesy of D. A. Muller, J. Grazul,A. Ohtomo, H. Hwang, Bell Labs,Lucent Technologies, NJ (USA)

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Plasma Cleaning

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Plasma Cleaning

Theory Chemical reaction (oxygen plasma) Plasma disassociates oxygen

Disassociated oxygen reacts with hydrocarbonon specimen holder to form CO, CO2, and H2O

These species are pumped away

D i

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Plasma Chamber

Inductively Coupled HF Plasma

Design

Ion Impingement Energies

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Ion Impingement Energies

50

0

5

10

15

2025

30

35

40

45

5 10 15 20 25 30 35 40 45 50

Chamber Pressure (mTorr)

Ion

Ene

rgy

(eV)

Z = 0 cm

Z = 10 cm

0

EELS for Contamination Thickness Determination

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I0 - Intensity UnderZero Loss Peak

It - Total Intensity in

Spectrum

t=l ln(It/I0)

t/l - Mass Thickness

EELS for Contamination Thickness Determination

C t i ti Thi k Ti S TiO3

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2.1

0.9

1.1

1.3

1.5

1.7

1.9

0 100 200 300 400 500 600

Time (seconds)

MassThickness

No Cleaning

One Minute Plasma Clean

Two Minute Plasma Clean

Contamination Thickness vs. Time SrTiO3

Plasma Cleaning of 304 Stainless Steel

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Plasma Cleaning of 304 Stainless Steel

1 Minute

2 Minutes

3 Minutes

4 Minutes

5 Minutes Arrow

After plasma cleaning

5 minute spot

1 Minute of Plasma Cleaning

Concluding Remarks

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Concluding Remarks

Integrated approach using instrumentsin series

Plan view or XTEM specimens ready for

transfer to and analysis by FE TEM

Resulting electron transparent regions

are free of artifacts and contamination