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thin film analysis using rigaku
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Comprehensive Thin Film Analysis:XRD vs Ellipsometry and Raman
Welcome
Uwe PreckwinkelWebinar Host
Today’s TopicsIntroduction to X-ray Diffraction (XRD)Comparison of XRD with other Metrology MethodsSemiconductor Application Examples
Guest SpeakersMike Lyubchenko – Applications Scientist, XRD, Madison, WIDr. Assunta Vigliante – Head of Business Development, Semiconductor Industry, Karlsruhe, Germany
IntroductionWhat Can XRD “See”?
When x-rays are scattered from nanoscale structures –such as atoms, molecules, films, grains or pores –a diffraction pattern will appear that carries information about the structure and morphology of the illuminated sample volume
X-ray Applications for Materials in the Semiconductor Field
XRD Thickness, Profiling
Phase, Composition, Crystallinity
Orientation, Texture, Mis-cut
Stress, Strain,
RelaxationDensity
Grain Size, Porosity,
RoughnessMetal layers
Diffusion stop layers
Low-k layers
Substrate
Silicides
High-k materials
Channel materials
D8 DISCOVER
Advanced Technology Platform
X-ray Source
4-bounce Monochromator Ge 022 asym.D8 Goniometer
Detector
SecondaryOptics
Göbel Mirror
KECEulerianCradle
D8 DISCOVER for Thin Film Analysis
Detectors for XRDD
imen
sion
CapabilitiesGain factor 3
GF >150 GF >500
GF >1000 GF >1500
XRD3 – Diffraction Space Viewer
LEPTOSMaterial Database
IntroductionXRD in the Semiconductor Field
Advanced sources, optics and detectors, as well as goniometers and software, allow straightforward analysis of:
small sample features and thin films
in high, medium and low resolution
for high-end research and fully integrated metrology
During this webinar, we will compare XRD to other analytical techniques and show application examples related to thin films
Semiconductor MetrologyMethods & Applications
Mike Lyubchenko
Semiconductor Applications
Metal layers: Cu, Al-Cu, WThickness, phase, orientation, stress
Barrier layers: Ta/TaN, Ti/TiN, W/WNThickness, density, phase
Low-k layers: Black Diamond, SiLKThickness, porosity
Silicide: WSi, TiSi, CoSi, NiSiThickness, phase
Gate oxide / High-k: SiO2, SiNO, Ta2O5, HfO2Thickness, phase, crystallinity
Channel: epi-SiGe, strained SiThickness, composition, relaxation
Substrate: Si, SOI, sSOIOxide thickness / depth, Ge profile, mis-cut angle
Metrology Techniques for Thin Films
Film Thickness MeasurementTransmission Electron Microscopy (TEM)Spectroscopic Ellipsometry (SE)X-ray Reflectivity (XRR)X-ray Fluorescence (XRF)X-ray Diffraction (XRD)Secondary Ion Mass Spectrometry (SIMS)Auger Electron Spectrometry (AES)Rutherford Backscattering Spectrometry (RBS)
Elemental CompositionX-ray Fluorescence (XRF)X-ray Diffraction (XRD)Auger Electron SpectrometrySpectroscopic Ellipsometry (SE)Secondary Ion Mass Spectrometry (SIMS)Rutherford Backscattering Spectrometry (RBS)Energy Dispersive Spectroscopy (EDS/TEM)
Metrology Techniques for Thin Films
Lattice Strain CharacterizationX-ray Diffraction (XRD)UV Raman SpectroscopyHigh Resolution Lattice Image (HRTEM)
Surface/Interface RoughnessX-ray Reflectivity (XRR)Atomic Force Microscopy (AFM)Transmission Electron Microscopy (TEM)
Use your mouse to answer the question on the right of your screen:
What methods do you currently use for thin films analysis? (Check all that apply):
Transmission Electron MicroscopySpectroscopic EllipsometryRaman SpectroscopyX-ray Reflectivity X-ray FluorescenceX-ray DiffractionOther
And the results are...
Your Turn…
Metrology Techniques - TEM
Capabilities
Multi-layer thickness capabilityExcellent defect detectionElemental composition (with EDS)
Advantages
Provides accurate film thicknessExcellent contrast between filmsProvides film interface informationProvides information on crystallinityHigh resolution (higher than SEM)
Disadvantages
Destructive; samples need thinning, down to <50 μmSpecimen preparation is time and labor intensive (2-3 hrs typical)Image artifacts require expert interpretation of micrographsSamples may be sensitive to electron beam damageSample may not be representative
Spectroscopic Ellipsometry
Ellipsometry is an optical technique used to analyze thin transparent layers. As the light shining on the sample passes through and bounces out, it undergoes some changes in its amplitude and phase. These two parameters are analyzed to derive information about the layers, such as their refractive indices and thicknesses.
Metrology Techniques - SE
CapabilitiesUses polarized light for stacked film optical thickness (refractive index)Elemental composition, roughness, thickness, optical constants
AdvantagesRapidNon-destructiveInsensitive to light intensity fluctuations & lossesMany in-line systems availableSmall spot size (25 μm) for features
DisadvantagesRequires transparent filmsDoes not measure quantities directlyQuantifiable only with standardsAnalysis can be difficultDifficult for thin conformal Si layer on rough relaxed SiGeProblems with fits when substrate stress is different from model stress
Optical constants change as a function of strain.
Raman – Principles
When a photon strikes a molecule, it can interact with it in many different ways. The two main ones are:
1. Rayleigh scattering - The photon bounces off of the molecule without any energy exchange
2. Raman scattering - The photon strikes the molecule, gets absorbed exciting the molecule. The molecule then relaxes to one of the lower energy states by emitting another photon of energy different from the incident one. The energy of the re-emitted photon can be either higher or lower than the original depending on a chemical state of he molecule.
Metrology Techniques – UV Raman
CapabilitiesComposition, crystallinity, strain/stressPhonon frequency shift in Si used todetermine strain in Si channelPeak broadening related to defects:dislocations, disorder, Ge out-diffusion, strain, nonuniformity
AdvantagesNon-destructive, no sample preparationRapid (364 nm Ar-ion laser resonance Raman 10X faster than 325 nm He-Cd laser non-resonance Raman)Small spot size (0.4 μm)Not affected much by roughnessControl of penetration depth (325nm <10 nm)
DisadvantagesNo in-line monitoring tools available for patterned wafersRequires complex data interpretationGe composition variation (out-diffusion) affects accuracy of derived strain value.
Metrology Techniques - XRFCapabilities
Multi-element compositionGood precisionFluorescence intensity is proportional to atomic densityThickness measurements
AdvantagesSpot size (40-50μm)ppm capability in a few cases; more commonly, 0.01% detection limitsSimple spectra – No fitting or models requiredHigh Throughput (~10 sec per site)Whole wafer analysisNon-destructive
DisadvantagesCalibration standards requiredSome elements (e.g. Ge) have low fluorescence yield (long acquisition times)Matrix effects (fluorescence absorption and enhancement) must be compensatedOnly elements beyond O detectableInterference (different element, same peak)Diffraction background depends on substrate type
Metrology Techniques –High Resolution X-ray Diffraction
Capabilities
Strain/stressFilm thicknessComposition
Advantages
In-line monitoring tools availableNon-destructiveRapidHigh-accuracy
Disadvantages
Strain measurement straight-forward only on bulk Si wafersStrain measurement on SOI wafers is time-consumingRequires triple-axis reciprocal space maps
What Can Be Measured with X-rays?Thin Film Real Structure
Analytical TasksX-ray Reflectometry
RoughnessLayer thickness
A C
A B
A BxC1-x
Chemical Composition
Lateral structure
X-ray ReflectometryGeneral Remarks
Based on reflection of X-rays at interfaces – no crystal lattices needed
Non-destructive method for the investigation of the near surface region of different sample systems
• single crystalline, polycrystalline and amorphous samples
• polymers, organic samples (Langmuir Blodgett, etc.), fluids
Specular reflection of X-rays
• film thickness of single- and multilayer systems (0.1nm → 1000nm)
• density profiles of near surface regions (~1%)
• roughness of surfaces and interfaces (0.1nm → 5nm)
Diffuse scattering of X-rays
• roughness structure of surfaces and interfaces
• morphology, correlation length, fractal parameters
XRR – X-ray Reflectometry
thickness
density
Slope = roughness
A technique which utilizes the effect of total external reflection of X-rays. The measurements are done around a “critical angle” (an angle of total reflection). Below the critical angle, the X-rays don’t penetrate the sample surface. Above it, the penetration rises quickly with an angle. At every interface, a portion of X-rays is reflected. Interference of these partially reflected X-ray beams creates a reflectometry pattern.
XRR – X-ray Reflectometry
CapabilitiesStacked film thickness, density, surface/interface roughnessMost accurate in-line thin film metrology
AdvantagesCan accurately determine thickness, roughness, density of layersAny type of material can be analyzed (amorphous, crystalline, opaque) Complex multilayer structures can be measuredDoesn’t require a prior knowledge of material composition
DisadvantagesModeling can be difficultFairly slowSpot size, 80μm x ~3mm Ge diffusion reduces density contrastDoesn’t work well with very rough interfacesThere is an upper limit on thickness (<0.5 μm)
XRR – X-ray ReflectometryTypical Experimental Setup
Comparison of X-ray and Optical Analytical Techniques
ThicknessXRR is a direct methodXRR is material independentCan resolve complex layer stacks
CrystallinityXRD is the ideal technique to probe crystal structure
StrainHRXRD can determine strain and concentration independently with precision <1%HRXRD analysis is simple and can be automated
Semiconductor Industrial Applications
Assunta Vigliante
Bruker AXSD8 FABLINE with UMC300 STAGE
Industrial ApplicationsMeasurement Schemes
High-Resolution X-ray Diffraction (HRXRD)
• Single-crystal / epitaxial layer structure
• Composition, thickness, relaxation
X-ray Reflectivity (XRR)
• Polycrystalline, amorphous, single-crystal film structure
• Thickness, density, surface / interface roughness
Grazing Incidence Diffraction (GID)
• Polycrystalline thin film
• Crystallinity phase, grain size
Use your mouse to answer the question on the right of your screen:
What is your biggest challenge in analyzing semiconductor or thin film samples? Choose one:
Integrating analysis instruments into my fabrication processesDetermining the best measurement method for my applicationBeing able to apply multiple analytical methods with one instrumentLogistical and environmental constraints of placing an instrument in my facility
Please Tell Us…
And the results are…
Limits of X-ray Reflectometry Thick LayersExample: SiO2 on Si
Int. [a
u]
5
10
100
1000
1e4
2θ [°]
0.11 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1
Si
1014 nm SiO2:H
Limits of X-ray Reflectometry Thin LayersExample: LaZrO on Si
2θ [°]1412108642
Inte
nsity
[au]
-81*10
-71*10
-61*10
-51*10
-41*10
-31*10
-21*10
-11*10
01*10
Si (111)
6.7 nm LaZrO
X-ray ReflectometryExample of Sensitivity to Layer Thickness
0,0 0,5 1,0 1,5 2,0 2,5 3,010-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
5x10x
InPInPInGaAsInPInP50nm
5nm3,5nm4,5nm
InPInPInGaAsInPInP
4nm4nm5nm50nm
10x 5x
Refle
ctiv
ity
Incidence angle [o]
Metal / Barrier Layers (Cu Process)30 nm Cu/10 nm Ta/Si
2θ (degrees)1 2 3 4 5
Rel
ativ
e in
tens
ity
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
experimental simulation
Material Thickness(nm)
Roughness(nm)
Density(g cm-3)
Cu2O 2.20 ± 0.57 0.80 ± 0.47 2.38 ± 1.70
Cu 29.14 ± 0.56 1.91 ± 0.93 9.00 ± 0.55
Ta 8.23 ± 0.05 0.35 ± 0.09 16.62 ± 0.55
Si --- 0.48 ± 0.04 2.33
Silicide LayersTiSi / TiN / Si
Detected Phases: TiSi2, Ti5Si3, TiN
VLR40077.05
00-038-1420 (*) - Osbornite, syn - TiN - Y: 50.00 % - d x by00-029-1362 (*) - Titanium Silicon - Ti5Si3 - Y: 18.75 % - d
00-035-0785 (*) - Titanium Silicon - alpha-TiSi2 - Y: 12.50 Operations: Background 0.000,1.000 | ImportFile: VLR40077-05.raw - Type: 2Th alone - Start: 20.000 ° -Operations: ImportFile: VLR40077-05.raw - Type: 2Th alone - Start: 20.000 ° -
Lin
(Cou
nts)
0
1000
2000
3000
4000
5000
6000
2-Theta - Scale20 30 40 50 60 70 80 90
Θ=0.3°
Pattern or Product Wafers
HeterostructuresRelaxation Degree RExample: Si1-xGex - Si structure
R = 0R = 1
SL ad ≠||
partially relaxed layer completely relaxed layerpseudomorphic layer
0||
≠Δdd
LLL add ==⊥ ||
aa
dd
dd Δ
=Δ
=Δ
⊥||
relaadd
Δ
Δ
= ||R
Measurement Scheme (I)High-Resolution X-ray Diffractometry (HRXRD)
Applicable semiconductor processes
• SiGe and SiCepitaxial thin film
• Strained Si film
• SOI and sSOI
Analysis parameters
• Composition
• Thickness
• RelaxationSim Curve Raw Curve
2theta / omega (degree)69.869.669.469.26968.868.668.468.26867.867.667.467.2
Inte
nsity
-51*10
-41*10
-31*10
-21*10
-11*10
01*10
Pattern Recognition
Cognex Pattern Recognition
Autofocus function
7 zoom factors
Laser video system
SiGe on Si
Operations: ImportFile: PatternedSiGe_VS0i1_HS0i2_SiGe004_06.raw - Type: Rocking curve - Start: 33.600 ° - End: 34.600 ° - Step: 0.002 ° - Step time: 2.1 s - Temp.: 25 °C (Room) - Time Started: 1074 s - 2-Theta: 68.
Log
(Cps
)
1
2
10
3456
100
1000
1e4
2e4
Theta - Scale33.6 33.7 33.8 33.9 34.0 34.1 34.2 34.3 34.4 34.5 34
Counts
1 10 100 1000 1e41 10 100 1000 1e4
[001] - File: m224+ [001].raw - Type: General Scan - Start: 1.
l [00
1]
3.915
3.92
3.93
3.94
3.95
3.96
3.97
3.98
3.99
4.00
4.01
4.02
4.03
h [110]1.986 1.99 2.00 2.0
Cps
1 10 100 1000 1e41 10 100 1000 1e4
[001] - File: m004 [001].raw - Type: General Scan - Start: -0
l [00
1]
3.915
3.92
3.93
3.94
3.95
3.96
3.97
3.98
3.99
4.00
4.01
4.02
4.03
h [110]0
(-0,0018; 3,9436) (1,9975; 3,9457)(0; 3,9436)
(1,9994; 3,9437)
Miscut=0,038 deg)
SiGe on SOI
SOI
200μm collimeter, about 400 seconds per point
DIFFRACplus LEPTOS 3Automatic FittingExtended Genetic Algorithm
Measurement tasks automated using Visual Basic scriptsAutomatic alignment for reflectometry and Bragg reflectionsFirst task - analytic profile fitting - TOPAS BBQ • Choice of profile shape function: Pseudo-Voigt and
Pearson VII• Crystallite size determination by Scherrer method
Second task - simulation & fitting- LEPTOS • unified program for XRR &HRXRD• script automation
D8 FABLINEAutomated Operation and Analysis
Texture Measurements on Cu Lines
Beam spot 100μmTexture measurement can be done in 15 min(111) and (200) Cu reflections are collected simultaneously
Stress Measurements on Cu Lines
Beam spot 100 μmStress measurement can be done in 2 hrs(331) and (420) Cu reflections are collected simultaneously
Stress Measurements on Cu Lines
Industrial Applications
High-Resolution X-ray Diffraction (HRXRD)
X-ray Reflectivity (XRR)
Grazing Incidence Diffraction (GID)
Grazing Incidence Small Angle Scattering (GI-SAXS)
In-Plane Grazing Incidence Diffraction (IP-GID)
Texture
Stress
All in one instrument!
Thank you for attending!
Please provide feedback bycompleting our brief survey.
Also, please type any questions you may have in the Q&A panel to the
right of your screen and click Send.
Links to a recording of this webinar and resources on thin films will be
emailed to you.
www.bruker-axs.com
See us at:International Conference on Crystal Growth (ICCG-15)
August 12-17, 2007Salt Lake City, UT