MS482MaterialsCharacterization(재료분석)

LectureNote8:XRDandXRR

Byungha ShinDept.ofMSE,KAIST

1

2016FallSemester

CourseInformationSyllabus1. Overviewofvariouscharacterizationtechniques (1lecture)2. Chemicalanalysistechniques (8lectures)

2.1. X-rayPhotoelectronSpectroscopy(XPS)2.2. UltravioletPhotoelectronSpectroscopy(UPS)2.3. AugerElectronSpectroscopy(AES)2.4. X-rayFluorescence(XRF)

3. Ionbeambasedtechniques (4lecture)3.1. RutherfordBackscatteringSpectrometry(RBS)3.2. SecondaryIonMassSpectrometry(SIMS)

4. Diffractionandimagingtechniques (7lectures)4.1. Basicdiffractiontheory4.2. X-rayDiffraction(XRD)&X-rayReflectometry(XRR)4.3. ScanningElectronMicroscopy(SEM)&

EnergyDispersiveX-raySpectroscopy(EDS)4.4. TransmissionElectronMicroscopy(TEM)

5. Scanningprobetechniques (1lecture)5.1. ScanningTunnelingMicroscopy(STM)5.2. AtomicForceMicroscopy(AFM)

6. Summary:Examplesofrealmaterialscharacterization (1lecture)*CharacterizationtechniquesinblueareavailableatKARA(KAISTanalysiscenterlocatedinW8-1)

X-rayDiffraction(XRD)

XRDdeterminesphase,orientation,%-crystallinity,andcrystallitesizeforbulkmaterialsandfilms

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XRDsetup

c

2q:scatteringangle

𝑘CD 𝑘EFG

𝑘 or �⃑� �⃑� =?

(0,0,0)

(h,k,l)Ø Non-zerodiffractedintensity,

when�⃑� = �⃑�MNOè 2𝑑MNO sin 𝜃 = 𝜆

Ø Measurementofdiffractedintensityasfunctionof2qà dhkl

Ø MeasurementofdiffractedintensityasfunctionofacombinationofW and2qà shapeofreciprocalpoints

W

Accessibleregioninreciprocalspace:wavelength

�⃑�MNO > 2 ∗ 2𝜋/𝜆:notaccessible

�⃑� = 2 ∗ 2𝜋/𝜆

�⃑�

�⃑�W

c

Maximum �⃑� = 2 ∗ 2𝜋/𝜆,when𝑘𝑖𝑛and𝑘𝑜𝑢𝑡 arealongtheoppositedirection.

𝑘CD whentheincidentangleW =0

𝑘CD whentheincidentangleW <0

Accessibleregioninreciprocalspace:geometry

Wc

�⃑�MNO > 2 ∗ 2𝜋/𝜆:notaccessible

W-2q (q-2q)scan

�⃑�

• Bragg-Brentanogeometry:theincidentangleW isalways½ofthedetectorangle2q (thesamplerotatesatq o/minandthedetectorrotatesat2q o/min;orthesampleisfixedandthetuberotatesataq o/minandthedetectorrotatesatq o/min)

• Inthisgeometry,thescatteringvector,�⃑� isalwaysnormaltothesurfaceofthesample

W

W-2q (q-2q)scan:singlecrystal

2q

[100] [110] [200]�⃑� �⃑� �⃑�

𝑘CD 𝑘EFG

�⃑�

𝑘CD 𝑘EFG

�⃑�

(200)

(100)(110)

𝑘CD 𝑘EFG

�⃑�

OnlyonefamilyofBraggpeaksinthediffractionpattern.

(110)

W-2q scanwithtilt:singlecrystal

[110] �⃑�

𝑘CD 𝑘EFG

�⃑�(110)

2q

W q

W = q

2qq

W

W + tilt = qW ≠ q

𝑘CD 𝑘EFG

�⃑�(110)

symmetricW-2q scanasymmetric

W-2q scan

CoupledScan

symmetricscan asymmetricscan

W-2q (q-2q)scan:polycrystalline(orpowder)

Powderdiffraction

• Foreverysetofplanes,therewillbeasmallpercentageofcrystallitesthatareproperlyorientedtodiffract

15 20 25 30Two-Theta (deg)

0

100

200

300

400

500

600

700

Inte

nsity

(Cou

nts)

PeakPosition determines:•Phase(comparetodatabase)•Stress(relativetootherpeaks)

PeakShape determines:•Crystallitesize•Micro-strain(withincrystallites)

PeakArea determines:•Percentcrystallinity•SimpleTexture

TypicalW-2q scanXRDAnalysis

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12

Phase-ID:Whatisthatmaterial?

PhasesIdentified:•Quartz– SiO2

•Muscovite– KAl3Si3O10(OH)2•Montmorillonite–

Ca0.2(Al,Mg)2Si4O10(OH)24H2O•Kaolinite– Al2Si2O5(OH)4

UnknownGeologicalMaterial

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13

20 30 40 50 60 70 80Two-Theta (deg)

x103

2.0

4.0

6.0

8.0

10.0

Inte

nsity

(CPS

)

00-038-1420> Osbornite - TiN

Peakwidthbroadensascrystallitesizedecreases• Maximummeasurablecrystallitesize~500nm

• Minimummeasurablecrystallitesize~1nm

CrystalliteSizeof:100nm10nm3.0nm1.5nm1.0nm

SimulationofpolycrystallineTiN thinfilmswith5differentcrystallitesizes

EffectofCrystalliteSize

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14

HighResolutionDiffractionEpitaxialSiGe onSi

StrainedFringesrelatetolayerthickness(seeXRR)

Relaxed

Peakshiftcorrelatestostrain

SiGe peakSipeak

SiGe

Si

Relaxed

Relaxed

Strained

Strained

Rockingcurve(W scan)RockingCurve:aplotofX-rayintensityvs wwhilekeeping2q thesame

• Inarockingcurve,thedetectorissetataspecificBraggangleandthesampleistilted.

• Aperfectcrystalwillproduceaverysharppeak,observedonlywhenthecrystalisproperlytiltedsothatthecrystallographicdirectionisparalleltothediffractionvector�⃑�

• Defectslikemosaicity,dislocations,andcurvature createdisruptionsintheperfectparallelismofatomicplanesà broadeningoftherockingcurve

2q

[400]

2q

[400]

2q

[400]�⃑� �⃑� �⃑�

MosaicSpread

Rockingcurve(W scan)

2q

[400]

2q

[400]

2q

[400]�⃑� �⃑� �⃑�

• Magnitudeof�⃑� doesn’tchangebecause2q iskeptthesame.

• Onlythedirectionof�⃑�changes.

�⃑�

Rockingcurve:Arccenteredontheorigin

ScanDirections

Detectorscan(2q scan)Detectorscan:aplotofX-rayintensityvs 2qwithoutchangeW

𝑘CD

𝑘EFG

• Changing2qwithoutWà rotating𝑘EFG whilekeeping 𝑘CD• Magnitudeof�⃑� changesbecause2q changes.

Detectorcurve:ArcalongtheEwaldspherecircumference

ReciprocalSpaceMap(RSM)

a*

b*

a*

b*

• Effectssuchasstrainwillshiftreciprocallatticepoints,preventingthecollectionofdatawithasinglescan

• Thereciprocalspacemapusesmultiplescansinordertoobserveboththefilmandsubstratepeaks:W-scanoverarangeof2q or2q scanoverarangeofW

ExampleofRSM:InAlAs/InP SLs

InPInAlAsInPInAlAsInP

InAlAs

z

x

Verticalsuperlattices

Lateralsuperlattices

Alrich

InrichInrich

DQx =2p /d

d

Shinetal,Appl.Phys.Lett.80,3292(2002)

DiffractionfromMulti-layeredStructure

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EpitaxialCu-Nifilmsgrownalong[111][111]

Cu

Cu

Cu

CuAu

Au

Au

Au

=0

0

0

0Au- Cu

Au- Cu

Au- Cu

Au- Cu

+Cu

= +Cu

0

0

0

01

1

1

1.Au- Cu

d

DiffractionfromMulti-layeredStructure

~

𝐹 multilayer = 𝑓aF b 𝐿deefgh + 𝑓jF − 𝑓aF b 𝐿dee

fgh ∗ 𝐹[]

0

0

0

01

1

1

1

[111]

setofpointsspaced2p/dapart,withintensityofeachpointmodulatedbySinc function.

Reciprocallatticeoffcc(bccwith4p/a)

Sinceisin[111],theFourierTransformof𝐿deefgh looks

likeasetofpointsspaced4𝜋𝑎3�

2 apart.

12

DiffractionfromMulti-layeredStructure

~

𝑓jF − 𝑓aF b 𝐿dee4𝜋𝑎 ∗ 𝐹 =

0

0

0

01

1

1

1

=

2𝜋𝑑

Satellitepeakfromsuperlattices

FI(q)?• I ~ 𝐹(𝑘) 2

• 𝑘 = 4𝜋𝜆 sin 𝜃à 𝜃 = sin−1 𝜆

4𝜋 𝑘

GrazingIncidenceXRD(GIXRD)

~

• Surfacesensitivescatteringtechniqueforultra-thinfilms(oftenwithnanostructures)

• Constantgrazing(<afewdegrees)incidenceanglekeptconstantwithdetectormovingvertically(out-of-plane)orhorizontally(in-plane),orwitha2Dareadetector

• AlsocalledGISAXS(smallangle),GIWAXS(wideangle)dependingonthevalueofq(Å-1)

GIXRDout-of-planescan

Regularq-2q scanBragg-Brentanogeometry

GrazingIncidenceXRD(GIXRD)

out-of-planescan

in-planescan

Shaoetal.ACSAppl.Mater.Interface4,5704(2012)

P3HTchains

P3HT:PCBMfilmsondifferentsurfacesout-of-planescan in-planescan

face-on

edge-onface-on

edge-on

StrengthsandLimitationsofXRD

• Strengths– Samplingdepthfrom~2nmtoasdeepas~10mm– Qualitativephaseidentification(oxidationstates)– Quantitativephaseanalysis– Analyzeanysolidsample– Ambientconditions(novacuumrequired)

• Limitations– Detectionlimitstypically~2%– Smallestanalyticalarea~50mm– Identificationofphaseslimitedtocrystallinematerials

(cannotidentifyamorphousmaterials)

X-rayReflectivity(XRR)

XRR accurately measures the density and thickness of thin films

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XRR:Theory/Background

• Sampleisanalyzedusingabeamofmonochromatic,non-divergentX-rays– TheanglebetweenthesampleandtheincidentX-raysisscannedfrom0° to~3°whilerecordingreflectedX-raysignal

• The“CriticalAngle”dependsonfilmdensity– BelowthecriticalangleallX-raysarereflected– AbovethecriticalangleX-raysbegintopenetratebelowthesurface

• PenetratingX-raysarereflectedfromburiedinterfaces– Constructive/destructiveinterferenceproducesapatternofinterferencefringes

– Periodicityoffringesdependsuponlayerthicknesses– Roughnessofsurfaceandinterfacesaffectssharpnessoffringes

0.00001

0.0001

0.001

0.01

0.1

1

10

0 0.2 0.4 0.6 0.8

IncidentAngle（deg.）

Refle

ctivity

TXRFRegion- datanotusedinXRR

cq

TypicalXRRData

Criticalangle- usedfordensity(films>300Åthk.)

InterferenceFringesusedforThickness

Slopeforroughness

~

XRRDataAnalyzedbyFittingwithTheoreticalCurve

Layer Thickness (nm) Roughness (nm) Density (g/cm3)

Ru 11.64 1.287 11.46

Si Bulk 0.978 3.50

Fit(LogChi-Sq.)=5.152(PoorFit)

1st Iteration ©Copyright EvansAnalyticalGroup®

Layer Thickness (nm) Roughness (nm) Density (g/cm3)

RuO2 4.77 1.091 8.11

Ru 6.51 1.111 12.05

Si Bulk 0.978 2.46

Fit (Log Chi-Sq.) = 2.036 (Good Fit)

XRRDataAnalyzedbyFittingwithTheoreticalCurveFinalIteration ©Copyright EvansAnalyticalGroup®

ExampleofXRR:HfO2 Thickness

39Å Thick50Å Thick

27Å Thick20Å Thick

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ApproachingminimumthicknessforXRR

ExampleofXRR:HfO2 Thickness

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Typical Low-k films analyzed:

• MSQ

• HSQ

• a-CF

• CVD-SiOC

• CVD-SiOF

• FSG Thickness739.8(nm)Density0.89(g/cm3)

ExampleofXRR:Low-κ Thickness&Density

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• Strengths–AbsoluteLayerThickness(nostandardsneeded)–AbsoluteLayerDensity(nostandardsneeded)–FullWaferMapping(inconjunctionwithXRF)

• Limitations–Nocompositionalinformation:onemustassumecompositionoflayers

–Smallestanalyticalarea~1cm–Maynotbeabletoresolvetwolayersofsimilardensity

StrengthsandLimitationsofXRR

ComplementaryTechniquestoXRR

RBS XRR/XRF Auger/XPS SIMS

Mapping aFull Wafer a a aDose a a aProfile a a aFilm Composition

a a

Density a aThickness a a a aHydrogen a a