Workshop on

TRACE ANALYSISTRACE ANALYSISTXRF

GI XRFGI-XRFSR-TXRF

SR TXRF XANESSR-TXRF-XANES

Ch i ti St liChristina StreliAtominstitut, TU Wien

Austriastreli@ati.ac.at

• TXRF: total reflection X-ray fluorescence analysisanalysis

• GI-XRF: grazing incidence XRF• SR-TXRF: synchrotron radiation induced

TXRF• SR-TXRF-XANES: SR-TXRF X-ray

absorption near edge spectroscopyp g p py

EDXRF

E D X R F

Standard XRF Micro XRF(µ-XRF)

Total Reflection XRF(TXRF)

Absorption Spectroscopyin fluorescence mode (XAS)

Disadvantage

• scattering radiation fromsample & sample carrier

Advantage

high background

• simultaneous qualitative &quantitative determination ofmajor, minor and trace elements(down to ppm level)( pp )

EDXRF at the Atominstitut

E D X R F

Standard XRF Micro XRFµ-XRF

Total Reflection XRFTXRF

Absorption Spectroscopyin fluorescence mode (XAS)

Advantages

• background reduction

double excitation of sample• double excitation of sample

• small distance sample detector (~1mm) large solid angle

angle dependence of fluorescence• angle dependence of fluorescence signal

information about type of sample (bulk, particle, film, implantation)

Fundamentals of TXRF

Total (external) reflection of X Rays Total (external) reflection of X-Rays

ρδ ⋅≈⋅≈ΦEcrit

7.202

3φcrit [mrad], E [keV], ρ [g⋅cm-3]

ϕ critical(Si k ) 0 ° d

βδ in −−=1X-ray range:

)()(

2

1

EfKEfK

⋅=⋅=

βδδ ~ 10-6 … dispersion:

β ~ 10-8 … absorption:

f t i tt i f t

(Si, 17.5 keV) ≈ 0.1° ≈ 1.75 mrad(Si, 500 eV) ≈ 3.7° ≈ 64.6 mrad(Si,12.2 keV) ≈ 0.15° ≈ 2.6 mrad

fi … atomic scattering factorr0 … classical elektron radiusλ … wavelength of incident beamNA … Avogadro‘s constantA … atomic weigth

ρπλ

⋅⋅⋅

=A

NrK A

2

20

gρ … density [g⋅cm-3]

Fundamentals of TXRF

ρδ ⋅≈⋅≈ΦEcrit

7.202

βδ in −−=1φcrit [mrad], E [keV], ρ [g⋅cm-3]

Transmission / Reflection Coefficient17.5 keV, Si-reflector

1

Penetration depth (nm)17.5 keV in Si

10000

m)

0,01

0,1T R 100

1000

netr

atio

n de

pth

(nm

φ

0,0010 0,5 1 1,5 2

φ/φ

1

10

0 0,5 1 1,5 2 2,5 3 3,5 4angle(mrad)

pe φ

crit

φ/φcrit

X i t it i th i it f th f X-ray intensity in the proximity of the surface

)sin(2 ϕλ

=D

λ

I0 IR

)sin(2 ϕ⋅

50

100

ace

[nm

]

φD

0

50

airsilicon e

from

surfa

-50

silicon

dist

ance

ϕ = ϕcrit/2

=

-10001234

ϕ = ϕcrit

ϕ = 2ϕcrit

X-Ray Intensity

Fundamentals of TXRF

4.0

Angle dependence of fluorescence signal information about type of sample:

• bulk

2.5

3.0

3.5

.0

nsity

[a.u

.] residueon surface surface layer

bulk

• particle (residue on surface)

• film, implantation (surface layer)

1.0

1.5

2.0

esce

nce

inte

n0 1 2 3 4 5

0.0

0.5

fluor

eincidence angle [mrad]g [ ]

Fundamentals of TXRF

Analytical features

• only small sample volumes required (ng some µl)• only small sample volumes required (ng some µl)

• detection limits in the pg range (for medium Z elements using X-Ray tubes)

• Simple quantification ( thin film approximation) by adding an internal standard

Environment: I d t i l/T h i l li ti

Applications of TXRF

Environment:

water: rain, river, sea, drinking water,

waste water.

air: aerosols, airborne particles, dust,

Industrial/Technical applications:

surface analysis: Si-wafer surfaces,

GaAs-wafer surfaces

implanted ions depth and profile variationsfly ash.

soil: sediments, sewage sludge.

plant material: algae, hay, leaves, lichen, moss,

needles roots wood

p p p

thin films single layers, multilayers

oil: crude oil, fuel oil, grease.

chemicals: acids, bases, salts, solvents. needles roots, wood.

foodstuff: fish, flour, fruits, crab, mussel,

mushrooms nuts, vegetables, wine,

tea.

fusion/fission research: transmutational elements in

Al + Cu, Iodine in water

Mineralogy:

ores rocks minerals rare earth elements various: coal, peat.

Medicine / Biology / Pharmacology:

body fluids: blood, serum, urine, amniotic fluid.

tissue: hair kidney liver lung nails stomach

ores, rocks, minerals, rare earth elements.

Fine Arts / Archeological / Forensic:

pigments, paintings, varnish.

bronzes, pottery, jewelry. tissue: hair, kidney, liver, lung, nails, stomach,

colon.

various: enzymes, polysaccharides, glucose,

proteins, cosmetics, bio-films.

textile fibers, glass, cognac, dollar bills, gunshot residue,

drugs, tapes, sperm, finger prints.

C.Streli 2003

TXRF

• TXRF for chemical analysis using internal standard for quantification

• TXRF of wafer surface analysis using external calibration and absolute quantification

•GI-XRF (changing angle of incidence) for depth profiling and thin layer analysis

• Synchrotron radiation induced TXRF (SRTXRF) for ultra trace analysisy

• SRTXRF-XANES for speciation at trace levels

Wafer surface analysis with TXRF

Si f t i ti t l i i d b th• Si wafer contamination control is required by thesemiconductor industry to produce high quality products withfast decreasing dimensions and prices. Metalliccontamination have negative effects on gate oxideg gproperties, resulting in quantifiable yield losses.

• Requirements on analytical methods are outlined in theSematech RoadmapSematech Roadmap

• Limit of total surface contamination : 5E9 atoms/cm2

Wafer surface analysis is the main application of TXRF worldwide!

• Straight TXRF – no sample preparationWafer analysis with TXRF

g p p p– Inspected area: 0.5 cm2– Mapping of wafer surface possible

Surface layer response of contamination– Surface layer response of contamination– LLD: E10 atoms/cm2

• VPD ( vapor phase decomposition)- TXRF– Decomposition of native oxide layer with HF vapor and collection

of impurities in one drop – inspected area: wafer size!p– LLD: E8 atoms/cm2

• VPT (vapor phase treatment) –TXRFD iti f ti id l ith HF ll ti– Decomposition of native oxide layer with HF, no collection

– leads to residue response of contamination– Mapping still possible– LLD: 2E9 atoms/cm2

Straight TXRF- VPD- VPT

Shimazaki, A.; Ito, S.; Miyazaki, K.; Matsumura, T.;

Semiconductor Manufacturing, 2005. ISSM 2005, IEEE International Symposium on 13-15 Sept. 2005 Page(s):456 - 459

Digital Object Identifier 10.1109/ISSM.2005.1513404

Wafer mapping

Chemical analysis- no sample prep.Analysis of whole blood sample dilution with UPWAnalysis of whole blood sample, dilution with UPW

Aerosol directly collected on Si wafer

Analysis of tap water

Synchrotron radiation

Synchrotron Radiation

IB3

Influence of radiation source upon S and IB:• Intensity (larger S and IB)

tI

SLLD B

⋅=3

• Spectral distribution(monochromatic excitation smaller IB)

• Linear polarization (smaller IB)

Why Synchrotron Radiation?

• High Intensity• High Intensity

• High collimation vertical to the orbital plane (little angular divergence)

• Continuos energy distribution monochromators can be used over a wide range of energies

• Photons are highly polarized in the orbital plane significant background reduction in EDXRF

Detection Limits in the fg range for medium Z Elements

Advantages of SR- TXRF

• high flux

• wide spectral range - wide range of detectable elements

• linear polarisation in orbital plane - reduction of background

• low detection limits ( fg range)

• small sample mass required

SR-TXRF @ HASYLAB beamline L

Experimental Setup @ HASYLAB beamline L

Detector (SDD)

CCD cameraDORIS-IIIΔθ

MonochromatorCrossSlits DORIS III

Δz

Slits

reflector

collimator

Beamstop Si-111

Multilayer PairSi-113

ΔzreflectorTa-wedge

ML → intensity gain of 80-100

only small increase of scatter peak

Vacuum chamberSi-113

SR-TXRF with sample changer8 stages

L

detector

Ta-wedge

Si-reflector

SR-TXRF:

8 fg detection limits in 1000s at 17keV

i i t d f 1 ² thi l d t 8E7 t / ²assuming an inspected area of 1cm² this value corresponds to 8E7 atoms/cm²

analysis of aerosols: coop Dr. Fittschen

L

Motivation:To understand the effect ofTo understand the effect of aerosols on global climate a detailed understanding of sources, transport, fate and the physical and chemicalthe physical and chemical properties of atmospheric particles is necessary.

The chemical speciation of theThe chemical speciation of the toxic elements is of relevance for the environmental impact.

Aerosol particle sampling device, 12-stage, round nozzle Berner low-pressure impactorfor particle sizes of 0 06-12for particle sizes of 0.06-12 µm (aerodynamic particle size);

TXRF- (& XANES) analysis of aerosols

LAdvantages of SR-TXRF:• only small sample mass required

• sampling time can be diminishedti l d i ti ti f t h i ttime resolved investigation of atmospheric events

• simple sample preparation(aerosols directly collected on reflectors)

• TXRF offers good sensitivity for XANES speciation of tracesg y p

Quantitative resultsL

20 min day time sampling in the city of Hamburg

8 16 8 m 2 8 2 m 0 13 2 0 13 m

Pb high in very small particles <

Seite 26

8: 16 – 8 µm, 2: 8 – 2 µm, 0.13: 2-0.13 µm, particles < 130 nm!

Comparison labTXRF with SRTXRF

Aerosol analysis May impactorKFKI-AEKI, Budapest, Szabina Török, Janos Osan

Size fractioned aerosol sampling

•7-stage May-type cascade impactor

•cut-off diameters: 16, 8, 4, 2, 1, 0.5, 0.25 µm for stages 1-7 at 20 lpm flow rate

•sampling 20-3200 l air depending on stages and aerosol concentration

C t i th Si f tl th iti ti l f th i l•Cr strip on the Si wafers exactly on the same position as particles from the air sample

The deposited aerosol particles form a 200-500 µm wide

strip in the middle of the Si wafer of 20x20 mm2strip in the middle of the Si wafer of 20x20 mm

Detection limits

•Detection limits in the pg/m3 range can be reached for a 20 min sampling

Element Regular Ult imate

Detect ion limit (pg/m3)Conclusions:

can be reached for a 20-min sampling time

•Further potential1 Time resolved trace element

S 451.3 163.96

Cl 282.8 102.72

Ca 70.2 25.491. Time resolved trace element analyses in havaria/emergency situation using portable TXRF

2 Potential to use in industrial/traffic

Ti 48.7 17.68

Cr 23.4 8.51

Fe 12.4 4.51 2. Potential to use in industrial/traffic processes where the time scale of the event is similar to the typical sampling durations

Cu 4.5 1.63

Zn 3.5 1.26

Se 2 6 0 95•Short time collection can allow one to study temporal variation of elemental concentrations in size-fractionated aerosol

Se 2.6 0.95

Br 2.4 0.88

Sr 3.4 1.23aerosolPb 5.3 1.92

Grazing incidence XRF ( GIXRF)

Angle dependence of fluorescence signal information about type of sample:

• bulk

• particle (residue on surface)

• film, implantation (surface layer)

3.0

3.5

4.0

y [a

.u.] residue

on surface surface layer

bulk

The incident angle dependence of the Depth profile

1.0

1.5

2.0

2.5

resc

ence

inte

nsity bulk

fluorescence intensity gives information on the

0 1 2 3 4 50.0

0.5

fluor

incidence angle [mrad]

depth distributionof the element.

Seite 30

Depth profil and thin layer analysis

SiNi

Depth profile

SiNi

Reflecting layer on surface

Ni depth profile (rectangular)Mo-Ka excitation

Si

Ni layers on Si substrateMo-Ka excitation

1000 00Mo-Ka excitation

100.00

1000.00dp 1nmdp 3nmdp 5nmdp 10nmd 25

100.00

1000.00Ni 1nmNi 3 nmNi 5 nmNi 10 nmNi 25 Ni 50

1.00

10.00

0 5 10

dp 25nmdp 50nmdp 100nmdp 250nmdp 500nm 1.00

10.00

0.00 1.00 2.00 3.00 4.00 5.00 6.00

Ni 50Ni 100Ni 500

Determination of:

• thickness

angle(mrad) angle (mrad)

• Composition

• density

C.Streli 2003

Thin layer analysis

Fit of the Angular dependence – Implanted Ion (As)G.Pepponi

Röntgenfluoreszenzanalyse mit Synchrotronstrahlung | | Seite 33

Determination of depth profile

0.20

Sample #3 As implanted@3keV annealed

]

Concentration profiles normalised to int(P)=1

Si 4x105

5x105Sample #3 As implanted@3keV annealed

]

measured Si

0.10

0.15

ntra

tion

[a.

u. Si2 Si2avg

2x105

3x105

4x10

cenc

e [c

ount

s Si Si2 Si2avg

0.00

0.05

conc

en

0

1x105

2x10

fluor

esc

0 10 20 30 40 50 600.00

depth [nm]0 1 2 3 4 5 6 7 8

0

incidence angle [mrad]

TXRF is suitable for the estimation of the total dose in ultra shallow ion implants in Si wafers and the results agree with the ones given by other techniques

• Fundamental parameters, no standards

Moreover, TXRF can be used for the verification of the quality of the profile given by other techniques, and in particular it is complementary to SIMS in the surface region layer.

the Si2 avg normalisation of SIMS signal gives better agreement with TXRF• the Si2-avg normalisation of SIMS signal gives better agreement with TXRF

Quantification results

implanted element As As As

implantation energy 1 keV 3 keV 3 keV

treatment none none annealed

nominal dose 2.00E+15 2.00E+15 2.00E+15

LEXES 2.2E+15 2.0E+15LEXES 2.2E+15 2.0E+15

RBS 2.0E+15 1.8E+15

TXRF result - fund par 2.3 ± 0.2 E15 2.0 ± 0.2 E15 2.1 ± 0.2 E15

Seite 35

New prototype for GI-XRF- ANNA JRA3

X-ray tubeVacuum chamber

MultilayerSi(Li) detector (snout)

CCD chip

slits

Vacuum feedthrough( bl )

Seite 36

Sample stage

(cables)

Specifications:

MultilayerDetector

Specifications:

Vacuum Chamber:300 x 300 x 340 mm3

Maximum wafer size: 150 mm diameterMaximum wafer size: 150 mm diameter

Detector: e2V 30 mm2 Si(Li), with AP 3.3 entrance window,resolution=134eV@40µs

Samplestage

Slit 2Electronics: TX 1255 Amplifier, Amptek 8000A Pocket MCA

X-ray tubes:3kW Mo-anode, 1.9 kW Cr-X ray tubes:3kW Mo anode, 1.9 kW Cranode (optional)0.04 x 12 mm2 focal spot (optical), LFFMonochromator: AXO NiC multilayer, 2d=12nm, N=702d 12nm, N 70

Seite 37

GI-XRF – best fit approach

In these first trials the As intensity curve has been fitted allowing the In these first trials the As intensity curve has been fitted allowing the SIMS profile to change by varying the sputtering rate in the first 5 nm

Sample AnnealingAs implant: 1E15 at/cm2 @3keV

Sample AnnealingEpi550 200’’ @ 550°Epi600 20’’ @ 600°Epi650 10’’ @ 650°

4.00E+021 original SIMS SIMS modified by GI-XRF fit

3000

4000 experimental intensities thoretical curve with original sims fitted theoretical curve no divergence fitted theoretical curve with divergence

l EPI550

Epi650 10 @ 650

2.00E+021

3.00E+021sample EPI550

atio

n [a

t/cm

3 ]

2000

3000 sample EPI550

ensi

ty [c

ount

s]

1.00E+021Con

cent

ra

1000

As

inte

Seite 38

0 5 10 15 20 250.00E+000

depth [nm]

0 1 2 3 4 5 6 70

incident angle [mrad]

X-ray Absorption Spectroscopy

XANES EXAFSThe x-ray absorption spectrum shows a fine structure if itis sampled with a high resolution.

absorption involves electronic transitions

fine structure affected by energy and density of l t i t t d t iti b bilitielectronic states and transition probabilities

influence of the environment:influence of the environment:neighbouring atoms (EXAFS), bond type (XANES)

XANESEXAFS

XANES: X-Ray Absorption Near Edge Structure, ends 50-100 eV above the edge

EXAFS: Extended X-Ray Absorption Fine Structure starts 50 - 100 eV above the edge

Seite 39

EXAFS: Extended X Ray Absorption Fine Structure, starts 50 100 eV above the edge

V i ti f it ti

Introduction - The EXAFS Experiment

Variation of excitation energy EedgeEstart Eend

• Spectrum at each energy• Spectrum evaluation

(peak area; e.g. As-Ka ROI)

• XANES: bond type

• EXAFS: neighboring atoms

XANESEXAFS

EXAFS equation Fingerprint method (XANES)

F.Meirer Seite 40

EXAFS equation, Fingerprint method (XANES)

Speciation of arsenic in xylem of plantsL

Motivation:Arsenic is contained in groundwater in Eastern Hungary (up

Coop: Eötvös Univ. Budapest, Prof. Zaray, Dr. Mihucz

Arsenic is contained in groundwater in Eastern Hungary (up to 2µmol). Speciation of As in xylem is important to:

• understand how plants metabolise and transform As

• assess the health risk caused by As entering the food chainXylem

• assess the health risk caused by As entering the food chain(different As species have different toxicity; e.g. As(III) and

As(V) )

Experimental:Experimental:

•At two leaf stage:transferred in solution with arsenic compounds andreduced phosphate concentrationreduced phosphate concentration

• After 30 days from germination (17 d arsenic):- stem cut 2 mm above root neck- sap collected with micropipettes

Source: www.fairchildgarden.orgsap collected with micropipettes

for 1 hour into PE vials immersed in ice salt bath

Speciation of arsenic in xylem of plantsL

Advantages of XAS in TXRF geometry:• TXRF offers good sensitivity for XANES speciation of traces (ppb range)

• only small sample volumes are required

• simple sample preparation (just pipetting some µl on reflectors)prevents unwanted oxidation of sample during preparation

Speciation of arsenic in xylem of plantsL

Results:• Speciation of As was possible down to the 30ppb levelSpeciation of As was possible down to the 30ppb level

• As(III) in nutrient solutions oxidises easily to As(V)

• Cucumber roots convert As(V) to As(III)

F. Meirer et al., Application of synchrotron-radiation-induced TXRF-XANES for arsenic speciation in cucumber (Cucumis sativus L.) xylem sap, X-Ray Spectrometry 36 (2007) 408-412.

XANES of Fe from various impactor stagesL

16-8µm

FeSO4

Fe K-edge Aerosols

6

•amounts of Fe on the collection plates were very low- around 500-

1000 500nm

2-1µm

4-2µm

6-4µmµ

a 4

very low- around 500-900 pg

•Fe was present in the oxidation state of three

130-60nm250-130nm500-250nm

1000-500nmarb. units

2

oxidation state of three and very likely in form ofFe(III)oxide in all impactor stages.

30-15nm

60-30nm

Fe2O3

0

energy (eV)7100 7120 7140 7160 7180

0

energy (eV)

U. E. A. Fittschen, F. Meirer, C. Streli,P. Wobrauschek, Julian Thiele,G. Falkenberg, G. Pepponi, Characterization of Atmospheric Aerosols using SR-TXRF and Fe K-edge TXRF-XANES Spectrochimica Acta B63(2008)1489–1495

Wafer surface analysis with SR-TXRF XANES

E i t l tL

Experimental setup:

Setup in clean environment at HASYLAB Beamline L

Wafer surface analysis with SR-TXRF XANES

IBM Wafer maps:

SR-TXRF Wafer mapping toSR TXRF Wafer mapping tolocalize Fe-contaminations:

FeCa

SR-TXRF spectra of Fe-contamination found at P7

Advantages of SR-TXRF XANES:

Wafer surface analysis with SR-TXRF XANES

Advantages of SR TXRF XANES:• multielement-analyis of Si-Wafer surface contaminations• wafer surface mapping (time consuming)• determination of contamination type• determination of contamination type(residual, surface layer, bulk)

• analysis of the oxidation state of an element of interest• all analyses can be done nondestructiveley within theall analyses can be done nondestructiveley within thesame setup

compound edge position [eV]FeS Iron(II)-sulfide 7117FeCl2 Iron(II)-chloride 7119( )FeSO4 Iron(II)-sulfate 7119.5Fe3O4 Iron(II,III)-oxide 7119.5FeC2O4 Iron(II)-oxalate 7120.5(NH4)2Fe(SO4)2 Ammonium-Iron(II)-sulfate 7122.5NH4Fe(SO4)2 Ammonium-Iron(III)-sulfate 7123F 2O3 I (III) id 7123 5

LLD1000 = 250 fg!

Fe2O3 Iron(III)-oxide 7123.5Fe(NO3)3 Iron(III)-nitrate 7125Fe2(SO4)3 Iron(III)-sulfate 7126Wafer at P5 Fe(III) 7125Wafer at P7 Fe(II) 7121.5Wafer at P21 Fe(III) 7124.5

F. Meirer, C. Streli, G. Pepponi, P. Wobrauschek, M.A. Zaitz, C. Horntrich, and G. Falkenberg,

Feasibility study of SR-TXRF-XANES analysis for iron contaminations on a silicon wafer surfaceSurf. Interface Anal. 2008, 40, 1571 – 1576

Wafer at P21 Fe(III) 7124.5Table 1: Oxidations states and edge positions of standards and samples

Conclusions

• TXRF is a powerful analytical method for trace analysis specially suitable for small amount samples– For various samples no sample preparation is required

• Chemical analysis - LLD: pg with X-ray tube excitation

• Surface analysis of Si wafer- LLD E9 atoms/cm2

GI XRF ll thi fil l i d d th fili• GI-XRF allows thin film analysis and depth profiling

• SR-TXRF allows analysis at ultra trace level- LLD: fg

• SR-TXRF-XANES: speciation at ppb levels

TXRF spectrometers

• Chemical analysis:– Picofox: www.bruker-axs.de/s2picofox.html?&L=1– TX2000: www.italstructures.com/tx2000.htm– WOBISTRAX: www.ati.ac.at/index.php?id=142&L=1– Nanohunter: www.rigaku.com/xrf/nanohunter-show.htmlg– Handy-type TXRF: int.icc.kyoto-u.ac.jp/?p=924,

www.ourstex.co.jp/product.html – Fisichem-TXRF: www fisichem comFisichem TXRF: www.fisichem.com

• Wafer analysis:Rigaku: www rigaku com/semi/txrf v300 html– Rigaku: www.rigaku.com/semi/txrf-v300.html

– Technos: www.technos-intl.com/index.php

SR-TXRF available at

Hasylab@DESY, Hamburg , Germany- K.Rickers

ANKA Karlsruhe Germany R SimonANKA, Karlsruhe, Germany- R.Simon

PTB lab @BESSY2, Berlin, Germany - B.Beckhoff

SSRL, Stanford, California - Piero Pianetta

NSLS, Campinas, Brazil - Carlos Perez

SPring8, Japan - Kenji Sakurai

Acknowledgement

• Florian Meirer• Giancarlo Pepponi• Giancarlo Pepponi• Dieter Ingerle• Peter Wobrauschek• MaryAnn Zaitzy• Ulla Fittschen & Jose Broekaert• Szabina Török & Janos Osan• Szabina Török & Janos Osan• Gyula Zaray & Victor Mihucz