ms482 materials characterization -...
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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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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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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
~
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.
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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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28
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
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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