Surface Analysis by

-AES-XPS-SIMS-XRD-SP1

XPS X- 10~100 100 ,

UPS 100 ,

AES Auger 20~60 20nm Auger

SIMS 2 50~300 1 2

ISS 1nm 1mm

SEM 2, X- 100 10 2 X- ,

TEM 50 10 ,

STEM , X- 10 3 X-

RBS He, H 20~200 1mm ,

LEED 2 ,

EPMA X- 1 1 X-

SAM Auger 10~100 0.1 Auger

AES : Auger electron Spectroscopy

SAM : Scanning Auger Microscopy

RBS : Rutherford Backscattering Spectroscopy

XPS : X-ray Photoelectron Spectroscopy (ESCA)

STEM : Scanning Transmission Electron Microscopy

SEM : Scanning Electron Microscopy

( ~ 20), , ( ~ 100)

,

Auger Electron Spectroscopy (AES)

AES (Auger Electron Spectroscopy)

Electron beam Auger electron

.

Surface Sensitivity

(Surface Sensitivity)

x-ray Auger

Schematic diagram of AES

Auger analysisData acquisition 10-8torr UHV chamber .

Electron gun : Primary electron beam

Electron energy analyzer and detector : measurement and collection of emitted electrons.

Sample manipulator : to locate the area of interest at the analyzer focal point.

Ion gun : cleaning of the sample and for depth profiling

Instrument

Physical Electronics Model 25-130 CMA

Electron source & analyzer

Electron sources (beam dia.)- Tungsten filament (3~5)

- LaB6 crystal (

AES

- (Auger peak)

- 2 (SEM)

- Depth profiling(Ion beam)

- line scan

- Image mapping

Line scan & image mapping

+= dzzzNTDrIIM

iMbi )exp()()1(

100)/(

/=

iiAA

A SPiSPX

XA: A atomic%, P: Peck to peck, S:sensitivity factor

AES spectrum

AES spectrum-Noise peak

-Spectrum (S/W) Depth profile data

Chemical shifts in AES profiles- ESCA

(Auger process 3 )

Sputtering rate

Sputtering rate

-sputter angle, ion energy, ion species, sample composition, sample density

-SiO2 sputtering

)(/)()(/)()()(

222 SiONSiOS

AlNNAlNSSiOvAlNv =

V : sputter , S : sputter yield, N: atomic number density

Depth resolution

-Unidirectional Sputtering Surface roughness (depth Z)

AES_PHI660 system

conventional SEM-Lanthanum hexaboride(LaB6) cathode-Secondary electron detector-CMA(cylindrical mirror analyzer)

Very small spot sizes (down 20 nm dia.)Sputtering (ino gun)

- Remove surface contamination- Remove material for depth profiling

Modes of operation- Survey- Line profile- Elemental mapping- Depth profile

Example1

0 10 20 30 40 50 60 70 800

20

40

60

80

100

Si

TiTi AgAg

Ag OO

2 kV Ar+

(3.3 nm SiO2/min)

Sputter Time (min)

Atom

ic %

SAM Image

SEM Image

[air | TiO2 (24 nm)|Ti (1 nm)|Ag (17 nm)|TiO2 (24 nm){TiO2 (24 nm)|Ti (1 nm)|Ag (13 nm)|TiO2 (24 nm) }2 |glass]

Summary

() (depth profiling) (point analysis) (image mapping) line scanning

(~25) ( ~)

(0.1at%) Bulk (Charging effect)

XPS

OverviewX- 100 .

X() (photoelectron) binding energy .

binding energy , .

: , , , , , ,

XPS Uppsala Siegbahn ESCA(ElectronSpectroscopy for Chemical Analysis) .

ESCA (elemental composition) (chemical state) . K, L(Shell) , (Binding Energy) . EX) 1s 531eV 1s 284eV,

2p 99eV . , .

X-ray , (Photoelectric effect) . , .

Chemical shift . . Chemical shift .

XPS(X-ray Photoelectron Spectroscopy)

Ek = hv - EB - W0 Ek : Kinetic energy of photoelectronhv : Photon energyEB : Binding energy of the electronW0 : Work function of the material

Photoelectric effect

X-ray: Mg Al K

target target X Mg K 1253.6eV, Al 1486.6eV

F= qE =m(V/R)

F : Force V : Speed R : trajectory radius E : electrical fields established by U potential m : electron mass q : electron charge

Kinetic energy

Principle of ESCA

Energy level diagram

XX--Ray Photoelectron SpectrometerRay Photoelectron SpectrometerSamples are irradiated with monochromatic X-rays which cause the ejection of photoelectrons from the surface. The electron binding energies, as measured by a high resolution electron spectrometer, are used to identify the elements present and, in many cases, provide information about the valence state(s) or chemical bonding environment(s) of the elements thus detected. The depth of the analysis, typically the outer 3 nm of the sample, is determined by the escape depth of the photoelectrons and the angle of the sample plane relative to the spectrometer.

Busan Branch

XX--ray Beamray Beam

XX--ray penetration ray penetration depth ~1depth ~1mmm.m.Electrons can be Electrons can be excited in this excited in this entire volume.entire volume.

XX--ray excitation area ~1x1 cmray excitation area ~1x1 cm22. Electrons are . Electrons are emitted from this entire areaemitted from this entire area

Electrons are extracted only Electrons are extracted only from a narrow solid angle.from a narrow solid angle.

1 mm1 mm22

10 nm10 nm

top layer

Bulk layer

not attenuated

attenuated by exp[-d/(E, matrix)cos]

d

BusanBranch

Surface sensitiveness

The dependence of electron mean free path on electron energy

Surface sensitiveness

Auger peak shifts

The photoelectron kinetic energy is depending on the source nature. The Auger electron kinetic energy is independent of the source nature. Changing the source will easily distinguish between photoelectrons and Auger el

Auger transition

Ghost peak

+323.9+556.9Cu

+728.7+961.7O

-233--Al

--+233Mg

MgAlContamination

h photons from the X-ray source are produced by electron bombardment on an anticathode .

If anticathode is slightly oxidised, oxygen atom will be excited .

The specimen is then excited by two sets of photons and it will in response generate two superimposed spectra.

Practical approach

Binding energy [counting rate, cps(counts per second)]Survey spectrumHigh resolution spectrum

Fermi energy

0 200 400 600 800 1000 1200

0

7000

14000

Inte

nsity

(cou

nt)

Binding Energy [eV]

Intensity(counts) (slurry) Intensity(counts) (DI) Intensity(counts) (pH2) Intensity(counts) (pH11)

528 530 532 534 536 538 540

0

5000

10000

15000

20000

25000

Inte

nsity

(cou

nt)

Binding Energy [eV]

O1sSurvey

Example of result on SiO2 film

SIMS

What is SIMS (Secondary ion mass spectroscopy) ?

Primary Ion Beam

Samples

Secondary Ions

Extraction Lens

Beam of Secondary Ions to be Analyzed

To mass spectrometer

keV ~ 10keV 2 . Ar+, Ne+, He+, O-, N-2 .

Composition

1. Cesium ion source

2. Duoplasmatron

3. Electrostatic lens

4. Sample

5. Electrostatic sector ion energy analyzer

6. Electromagnet mass analyzer

7. Electron multiplier / Faraday cup

8. Ion image detector

SIMS (primary ion source), (primary column), , (sample chamber), (detector) (secondary column), .

Primary ion source

Primary column

Duoplasmatron , (cesium)

.

SIMS . 133Cs+, 16O- . .

sputtering

Ion beam sputtering

350km/s .

bonding . ( , )

: 10nm

: 1nm

(4.5~10kV) .

Ionization efficiency ( ): sputtering

Sputtering , SIMS , He, Ne, Ar sputtering .

SIMS . , , SIMS ( ) . (magnetic sector) . (double focusing method) .

Ion energy analyzer, mass analyzer

Secondary ion detector

SIMS Faraday cup (Electron multiplier), . ppm(100 1) ppb(10 1) .

SIMS 1ng mg .

Sputtering .

(in-situ analysis) . , SIMS 1:1 .

, . , . .

Mass spectra

(Static SiMS) : 10~20 ,

Static SIMS (surface analysis)

Depth profiling

(Dynamic Sims) : .

Trace metal contamination in SiO2

Dynamic SIMS (depth analysis)

Ion imaging

(Imaging Sims) : , , , , , , , , .

, , , , , , , ,

Image dimensions : from 100um to less than 10um

Imaging SIMS (spatial analysis)

+ higher sensitivity+ More direct identification of organics+ faster imaging & depth information+ differentiation of isotopes

- More complex elemental quantification

SIMS VS XPS

Application Surface coatings Surface treatments Electronic components Semiconductors (GaAs, Si) Electrodes & sensors Catalysts Adhesives Lubricants Packing materials Corrosion studies

Polymer, Ceramic, Lubr