surface and thin film analysis ii: solving real problems in … · 2009-05-29 · m.anderle -sims-...

Surface and Thin Film Analysis II:

Solving Real Problems

in Materials, Nano and Bio

Mariano AnderlePromozione e internazionalizzazione del Sistema

Trentino della Ricerca

Dipartimento Innovazione, Ricerca e ICT

Provincia Autonoma di Trento

web: www.marianoanderle.it e-mail: anderle@fbk.eu

Outline I and II

•Vacuum and Surfaces

• Dynamic and static SIMS

• Principle

• Instrumentation

• Applications

• XPS, Auger

• Principle

• Instrumentation

• Applications

• Surface Technique Integrated Use

• Some examples

Università di Torino, Corso di Laurea in Fisica 27 maggio 2009

M.Anderle -SIMS- Università degli Studi di Torino, 26 maggio 2009

Vacuum

Coverage time

t= 3x10-6/pp pressure in mbar

p ~ 10-6 mbar t ~ sec

p ~ 10-9 mbar t ~ h

tmeas < t

Vacuum

p ~ 103 mbar l ~ 2.3*10-7 m

p ~ 10-3 mbar l ~ 2.3*10-1 m

p ~ 10-6 mbar l ~ 2.3*102 m

l 2.3*1041

Mean free path l

With p pressure in mbar and l mean free path in meter and T=300K:

THE CLUSTER LABORATORY

Mass Spectrometry Base Process

Particles Emission (Sputtering)

Particles Emitted Ionization

Dynamic SIMS Static SIMS

• Material removal

• Elemental analysis

• Profiling

• Ultra surface analysis

• Elemental or molecular analysis

• Analysis complete before significant

fraction of molecules destroyed

Analytical Modes of SIMS ISi JPY

M.Anderle -SIMS-

Dynamic/Static ISi JPY

M.Anderle -SIMS-

Dynamic, Static and Imaging SIMS

primary ion

secondary ions and neutrals

(atoms and molecules)

uppermost layer

The Secondary Ion Mass Spectrometry technique (SIMS) is the most sensitive of all the

commonly-employed surface analytical techniques - this is because of the inherent

sensitivity associated with mass spectrometric-based techniques.

There are three different variants of the technique:

Dynamic SIMS

used for obtaining compositional information as a function of depth below the surface

Static SIMS

used for sub-monolayer elemental analysis

Imaging SIMS

used for spatially-resolved elemental analysis

M.Anderle -SIMS-

Magnetic Sector

(Cameca 6f)

Advantages:

- high mass resolution (20000)

- high sensibility

- good depth resolution

- well defined analytical

methodology

Disadvantages:

- related impact energy and angle

- sputtering rate modification for

grazing angle

Quadrupole

(PHI 1010)

Advantages:

- unrelated impact energy and

- low impact energy

- high depth resolution

- well defined analytical

methodology

Disadvantages:

- bad mass resolution (300)

- bad sensibility

ToF-SIMS

(TOF-SIMS IV)

Advantages:- high mass resolution (10000)

- high transmission

- high lateral resolution

- parallel detection

Disadvantages:

- analytical methodology not

well defined

- fixed incidence angle

Platform Comparison

M.Anderle -SIMS-

Dynamic SIMS: Depth Profile

M.Anderle -SIMS-

Normalized at 56Si2 ptp

3keV Implant

0 20 40 601E16

As/Si 2E15 at/cm2 @ 3keV

Depth (nm)

D-SIMS @ 1.0 keV

D-SIMS @ 0.5 keV

D-SIMS @ 0.3 keV

Best detection limit @ 1

keV impact.

At 300 eV altered layer

minimized

Characterization of Temperature Effect

on Film Growth

Extent of reaction increases with surface temperature

thermally activated process 1.6 1.8 2.0 2.2

10-10 G

/Cycle

2*10-10

3*10-10

1000/T (K-1)

0 20 40 60 80 100 120

8.0x10-11

1.6x10-10

2.4x10-10

3.2x10-10

4.0x10-10

Scan Number

Exposure

ExposurePurge Purge

H2 signal SiF4 signal

175 ℃

225 ℃

275 ℃

325 ℃0 20 40 60 80 100

Depth (nm)

SIMS Result

W. Lei, L. Henn-Lecordier, M. Anderle, G. W. Rubloff, M. Barozzi and M. Bersani,

“Real-time observation and optimization of tungsten atomic layer deposition process cycle”,

J. Vac. Sci. Technol. B 24(2) (2006) p780-789.

M.Anderle -SIMS-

Mass Spectrum

20 40 60 80 100 120 140 160 180 200

C CO O

Positive TOF-SIMS Spectrum of PET

Fragments allow the molecular structure of the polymer to be defined.

200 250 300 350 400 450 500 550 600

+H C CO O

2 2HO CH CH M

(2M+H)+

(3M+H)+

Positive TOF-SIMS Spectrum of PET

The repeating peak patterns confirm the polymerization structure.

Low-k for faster interconnects and improved device performances

faster

0.65 0.5 0.35 0.25 0.18 0.13 0.1

Generation (MFS, µm)

device

Al + SiO2

interconnects

Cu + low K

interconnects

circuit speed

slower

time to propagate signal along interconnect

between devices is an RC delay

Al ( 3.0 mW cm) SiO2 (K=4.0)

Cu ( 1.7 mW cm) low-K (K=2.0)

low-k is achieved by

decreasing bond polarizability(using organosilicate, polymers, …)

lowering the density(foamed and porous materials)

metal dielectric

Microelectronics: Low K Materials

PROCESS FLOW SCHEMATIC spin-casting of porous low-K film

low-k matrix resin (PMSSQ)

porogen (PMMA co-DMAEMA)

solvents

spin castinginitial cure

template formationfinal cure

porogen volatilization

annealing

transformations & kinetics

ELECTRICAL PROPERTIESdepend on both:

STRUCTUREpores quality/quantity

MATERIALScharacteristics

mass200 400 600

Compression Fact or : 52

mass200 400 600

curing @ 50 °C x 3’

curing @ 225 °C x 1 h

curing @ 450 °C x 2 h

high mass ions progressively disappear upon annealing

• self-consistent identification of the “key” species

• “key” peaks intensity depends on the annealing T

MSSQ, transformation upon curingSSIMS, negative SI

TOF SIMS

100000

1000000

D OD CN C2N CNO C5 C6 C8 C9

50 °C x 3'

125 °C x 1h

225 °C x 1h

275 °C x 1h

325 °C x 1h

450 °C x 2h

pure, 50 °C x 3'

fragments

DMAEMA

ligand

porogen “backbone”

DMAEMA cleavage and evolution@ 225-275 °C (90%)remaining transforms by > 325 °C

PMMAno apparent trasformation until > 325 °C

SI species selectively related to PMMA and DMAEMA

NO porogen residuals by curing @ 450 °C

POROGEN,transformations upon curingPseudo-DSIMS, negative SI

NO backbone alteration until > 325 °C

OC C O

CD3 CH2

CH3 CH3

DEDUCTIONS:

• a different behavior for the ligand / backbone, PMMA / DMAEMA is observed

• the residual amount of porogen vs curing T can be evaluated

TOF SIMS

Several features of MATERIALS

TRASFORMATIONS and KINETICS in the

FORMATION of porous low-k can be

evaluated by means of ToF-SIMS

MATRIX and POROGEN transformations

are COMPETING upon curing. The

transformation kinetics can influence the

final low-k electrical properties and requires

to be evaluated

50 100 150

tive inte

200 250 300 350 400 450

fading ofprecipitates

appearance of porogen precipitates

annealing T [°C]

different behavior forPMMA and DMAEMAPMMA

DMAEMA

PMSSQ degree of curing

Si 7O 10C7H 21

Si 6O 10C5H 15

(pos. SI)(neg. SI)

porogen transformations:

mechanisms and kinetics are illustrated by the markers related to the PMMA/DMAEMA ligand /backbone

low-k transformations:

the “actual” chemical/compositional state of MSSQ is depicted by SSIMS

polymerization / crosslinking is pointed out by the vanishing of the “key species” (PMSSQs oligomers)

M.Anderle -SIMS-

Imaging SIMS

Images

Spatial resolution Spatial resolution

M.Anderle -SIMS-

Ion sources

as spun / curing < 225 °C

225 °C < curing < 450 °C

POROGEN AGGLOMERATES

agglomerates density dependson curing T

agglomerates composition(PMMA/DMAEMA ligand/backbone)depends on curing T

Field of view: 10.0 x 10.0 mm2

POROGEN,transformations upon curingimaging ToF-SIMS, negative SI

DEDUCTION: porogen transformation includes precipitation and segregation phenomena

lateral inhomogeneities

TOF SIMS

M.Anderle -SIMS-

Images

M.Anderle -SIMS-

Images

AgBr microcrystals

Br red

I yellow

Cl white

Dopant segregation

at grain boundaries

of alumina

M.Anderle -SIMS-

Images

Localization of In and Al in kidney cells

M.Anderle -SIMS-

Images

M.Anderle -SIMS-

Images

Main advantages and drawbacks

ADVANTAGES

Sensitivity 1ppm-1ppb

All elements are detectable

Isotopic detection

Good depth resolution

Lateral resolution

Quantification

Insulators are analyzable

DRAWBACKS

Ion yield up to 6 orders of magnitude

Strong matrix effects

Depth resolution depends on sample morphology

Specific standards are required

Destructive technique

Elastic reflected electrons (BE)

BE which lost

characteristic

energy:

• core level

ionization

• plasmon

excitation

Auger electrons

Secondary electrons (SE)

Differentiated Auger spectrum

Ejected Electrons

Kinetic Energy (eV)

Escape depth l as a function of electron energy

XPS-ESCA

X-ray Photoelectron Spectroscopy

Electron Spectroscopy for Chemical Analysis

electrons (E0, k0, s) electrons (E, k, s)

e.m.radiation (hn0, k0, polarization)

e.m. radiation (hn, k, polarization)

atoms (E0, k0, Z)

ions (E0, k0, Z) ions (E, k, Z)

atoms (E, k, Z)sample

Principle

Base principle of the technique is the photoelectric effect

Principle

• Electrons ejected from the solid surface keep memory

of the chemical element are coming from!

• Beeing able to discriminate photoelectrons with

different energy means to measure the chemical

composition of the solid surface!

Electron

Energy

Analyser

Sample

Chamber

Pumping

System

Source

Load Lock

Detectore-

Apparatus

•To avoid the electron collisions in the path from

surface to analyzer => P<10-3 Pa

• To avoid surface contamination during the

measurements => P<10-6 Pa

=> The electron spectroscopy techniques utilize

Ultra High Vacuum (UHV) conditions

Vacuum

Source

Ek=hn - Eb - Fhn

Analyser

Core level

FVacuum Level

Fermi Level

X Photons => XPS => Core Level

UV Photons => UPS => Valence Bandhn=>

Source

Ek = f ( EB )

EB is specifically related to the chemical element where the

electron is coming from!

• measuring Ek of the ejected electrons we can study the

elemental chemistry of the sample surface.

• the photoelectronic peak width Ek is directly correlated to

the width of source peak hn, beeing the core level peak

negligible and the work function F constant.

Main features:

• hn ~ 1 keV

• FWHM < 1 eV

• Intense beam

• Compatible with UHV

Source

The presence of a background radiation (Bremsstrahlung) limits

the energy resolution. An aluminum foil between the source and

the sample helps to reduce this Bremsstrahlung effects!

Monocromatic source

Source

To focus monocromatic X

ray beam on the sample,

quartz crystal, X ray

source and sample have

to stay on the same circle

(Rowland circle).

• UV Sources

Gas discharge

He I (21.2 eV), He II (40.8 eV)

• Syncrotron radiation

Monocromatic light with high

intensity and variable energy

Other sources

Analyzer

CHA - Concentric Hemisphere Analyzer

V2 - V1 = Uk = Ue (R2/R1 - R1/R2)

26/05/2009 50

OPTIMISATION OF SOFT TISSUE

ADHESION TO DENTAL IMPLANTS

membrane

gingival cell

integrin receptor

titanium alloy

plasma treatment for -NH2 introduction

Peptide adhesion

Implanted titanium screw

polished cervical

margin

abutment of

titanium alloypolished and smooth

transmucosal collar

rough endosseous

part (pure

titanium)

Resistance to transverse force component

Shorter to avoide neurological problems

Deporter, D.A., Todescan, R. et al.

Length

(mm)# Used # Failure % Failure

7 44 1 2.3

9 89 4 4,5

12 16 2 12,5

Overall 5 year failure rate = 4,6%

A Biological Functionalization to Stimulate the Soft Tissue

Adhesion

- Titanium alloy surface coating using a plasma assisted chemical vapor deposition process (PACVD) to reduce ion release from titanium and provide an amine-containing layer with adequate stability;

- PEG molecules immobilization creating a protein-resistant (non-fouling) surface;

- Cell adhesive, RGD-containing peptides immobilization stimulating the formation of the biological seal between the soft tissue and the implant.

Spectrum

800 600 400 200 0

XPS survey spectrum

Binding energy (eV)

UHV Plasma treatmentson Ti Al V alloy surface for

primary amine (NH2) group links

Spectrum

UHV Plasma treatmentson Ti Al V alloy surface for

primary amine (NH2) group links

404 402 400 398

other N species

Counts

Binding energy (eV)

ECM proteins and integrin receptors

GLY-ARG-GLY-ASP-

-SER-TYR-CYS

Adhesion

Peptide

Fibronectin

Titanium alloy functionalization: Overview

Step 1: amide bond through the N-hydroxysuccinimide ester (NHS)

Step 2: thiol chemistry (Vinylsulfone)

Fluorescent derivative PEG: 5.5 · 1013 molecules/cm2

Titanium alloy functionalization: XPS analysis

Ti TiC

TiC+pep

Ti+pep

Titanium alloy functionalization: Human gingival cells (HGF-1) adhesion

Cell images obtained with a laser scan

microscope (a and b) and with a scanning

electron microscope (a1 and b1)

RGD modified titanium alloy

titanium alloy

cells density on different substrates

17.500 cell/cm2

Incubation 24 h in serum free medium plus

cycloheximide (25 ug/ml)

Electron spectroscopy (ESCA) analysis of chitosan films

chitosan is obtained from chitin by deactylation.

Chitin Chitosan

NH2OHn

Nitrogen spectrum

Spectrum

Different energy lines (different values of EB) describing different

core levels characteristic of the specific material (Pd).

Auger line too!

CHEMICAL SHIFT

Quantification

Relative sensitivity factors

Depth Profiling

Increasing the lateral resolution of the technique

Spectromicroscopy

• focusing the X rays on

a small surface area

• detecting the electrons from

a small surface area

Spatial mode

Microelectronics: Oxynitrides

0.10 mm

good masking characteristic against impurity and dopant diffusion

0.25 mm

Oxynitrides advantages with respect to conventional SiO2:

good technological compatibility with new generation materials

better resistance to radiation damage and carrier injection

better resistance to dielectric breakdown

suitable dielectric constant

SiOxNy

Nitrided

region

Thickness

Precursor:

Thermal treatment:

Reoxidation:

Furnace

Sample # Oxidation Precursor Temperature Time

1 Dry N2O T2 t

2 Dry N2O T3 t

3 Dry N2O T3 2t

4 Wet N2O T2 t

5 Wet N2O T3 t

6 Dry NO T1 1.5t

7 Dry NO T1 3t

8 Dry NO T1 6t

9 Dry NO T2 3t

10 Dry NO T2 6t

Useful to obtain:

• Depth Profile

• Mass Spectra

• Bulk Analysis

• Ion Images

Vacuum: <10-7 Torr

Sputtering Rate: 0.1 20 Å/s

Primary Ions Energy: 0.25 15 keV

Primary Beam Current Density: nA/cm2 mA/cm2

Dynamic SIMS

X RADIATION

PHOTOELECTRONS

DETECTOR

• surface chemical composition

• chemical bonds

n BK EhE

= 90 d = 5-6nm

= 165 d = 2 - 3nm

BiomaterialsMicroelectronics: Oxynitrides

XPS (X-ray Photoelectron Spectroscopy)

0 50 100 150 200 250 300 350 40010

Depth (A)

Dynamic SIMS

-10 -8 -6 -4 -2 0 2 4 6 8 10

SiO2/Si interface

sample 1

sample 2

sample 3

sample 4

sample 5

Distance to Interface (nm)

Dynamic SIMS

-10 -8 -6 -4 -2 0 2 4 6 8 10

SiO2/Si interface

sample 6

sample 7

sample 8

sample 9

sample 10

Distance to Interface (nm)

Dynamic SIMS

Nitrogen

Profiles

12 10 8 6 4 2 0 -2

SiO2/Si interface

sample 1

sample 2

sample 3

sample 4

sample 5

sample 8

sample 9

sample 10

Residual thickness (nm)

Sample #N integral

(at/cm2)

SIMS peak

concentration (at/cm3)

Peak position

XPS peak

concentration (%)

1 6.0 x1014 2.2 x1021 -1.3 1.08

2 1.3 x1015 4.1 x1021 -1.8 1.74

3 1.4 x1015 3.6 x1021 -1.4 1.93

4 6.0 x1014 2.3 x1021 -1.4 0.74

5 1.3 x1015 4.1 x1021 -1.8 1.84

6 9.0x1014 3.0x1021 -1.3 -

7 1.1x1015 3.9x1021 -0.9 -

8 1.5x1015 4.8x1021 -1.1 2.76

9 1.7x1015 5.6x1021 -1.2 2.90

10 2.0x1015 6.5x1021 -1.3 3.52

402 400 398 396 394

interface

Binding Energy (eV)

sample 3

sample 10

12 10 8 6 4 2 0 -2

in Si3N

SiO2/Si interface

Residual Thickness (nm)

sample 1

sample 2

sample 3

sample 4

sample 5

sample 8

sample 9

sample 10

TECHNIQUE

XPS AES UPS SIMS TOF-SIMS SNMS XRD

Source X-Ray

(Mg, Al) Electrons

Photons UV (HeI, HeII)

Ions Ions Ions X-Ray (Cu)

Particle Photo-

Electrons Auger

Electrons Photo-

Electrons Secondary

Ions Secondary

Ions Neutrals post-

ionized X-Ray

Lateral Resolution

10 µm 0-2 µm No 0.5 µm 0-1 µm No No

Sensitivity 0.1 % at. 0.1% at. Parameter

without meaning

10-4÷10-6 % at.

10-4÷10-6 %

10-2÷10-4 % at.

0.5 % at.

Sampling Depth 2÷20 atomic-

layers

2÷20 atomic- layers

2÷3 atomic- layers

50 µm

Main Features Information on chemical

High spatial resolution

High sensitivity to valence

High sensitivity

to elements

Information on surface chemistry

Elemental Sensitivity &

Easy quantification

Structural Information

Instrument at ITC-irst

SCIENTA 200

Physical Electronics

PHI 590 PHI 4200

Physical Electronics

PHI 545

CAMECA IMS 4f

CAMECA SC Ultra

CAMECA ION TOF IV

Leybold Heraeus

Ital-structures

Surface and Interface Analysis

AESAuger Electron Spectroscopy

e.m.radiation (hn0, k0, polarization)

e.m. radiation (hn, k, polarization)

atoms (E0, k0, Z)

ions (E0, k0, Z) ions (E, k, Z)

atoms (E, k, Z)sample

electrons (E0, k0, s) electrons (E, k, s)

Principle

Possible de-excitation processes

due to electron bombardment

Auger and fluorescence efficency for a K vacancy as a function of atomic number, Z

Auger (continuos) and fluorescence (dashed) efficiency for K, L, M vacancies as a function of atomic number, Z

AES A E S

Analytical information from:

Peak energy ==> What (qualitative)

Peak shape and energy ==>How (chemistry)

Peak intensity ==> How much (quantitative)

AES Spectrum A E S

Transition elements 3d

M2,3VV L3M2,3V

L3M2,3 M2,3 L3VV

Characteristic features

•LMM triplet:

L3 M2,3 M2,3

L3 M2,3V

• Peak M2,3VV at

lower energy

100 200 300 400 500 600 700 800 900

Kinetic Energy (eV)

100 200 300 400 500 600 700 800 900

Kinetic Energy (eV)

Energy ==> information about the chemical elements

40 50 60 70 80 90 100 110

Elemental Silicon

Kinetic Energy [eV]

40 50 60 70 80 90 100 110

Elemental Silicon

Kinetic Energy [eV]

220 230 240 250 260 270 280 290

diamante

carbonio amorfo

nsity [arb

Kinetic Energy [eV]

grafite policristallina

Example: C KVV

Example: Si LVV

40 50 60 70 80 90 100

Silicon Oxide

Kinetic Energy [eV]

40 50 60 70 80 90 100

Silicon Oxide

Kinetic Energy [eV]

Auger line energy and shape ==> information about element chemistry

Analyzer

CMA Cilindric

Mirror

Analyzer

AES apparatus A E S

AUGER depth profiling A E S

Cr50nm

Ni65nm

0 5 10 15 20 25 30 35 40

tempo di sputtering [min]

surface and thin film analysis ii: solving real problems in … · 2009-05-29 · m.anderle -sims-...

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