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MS414 Materials Characterization (소재분석)
Lecture Note 12: Summary
Byungha ShinDept. of MSE, KAIST
1
2017 Fall Semester
CourseInformationSyllabus1. Overview of various characterization techniques (1 lecture)2. Chemical analysis techniques (9 lectures)
2.1. X-ray Photoelectron Spectroscopy (XPS)2.2. Ultraviolet Photoelectron Spectroscopy (UPS)2.3. Auger Electron Spectroscopy (AES)2.4. X-ray Fluorescence (XRF)
3. Ion beam based techniques (6 lectures)3.1. Rutherford Backscattering Spectrometry (RBS)3.2. Secondary Ion Mass Spectrometry (SIMS)
4. Diffraction and imaging techniques (7 lectures)4.1. Basic diffraction theory4.2. X-ray Diffraction (XRD) & X-ray Reflectometry (XRR)4.3. Scanning Electron Microscopy (SEM) &
Energy Dispersive X-ray Spectroscopy (EDS)4.4. Transmission Electron Microscopy (TEM)
5. Scanning probe techniques (1 lecture)5.1. Scanning Tunneling Microscopy (STM)5.2. Atomic Force Microscopy (AFM)
6. Summary: Examples of real materials characterization (1 lecture)
* Characterization techniques in blue are available at KARA (KAIST analysis center located in W8-1)
Technique Selection and Analysis Design
• Knowledge of the product and process• In-house analytical capabilities• Characterization of problem
– Can the problem be localized to a specific processing step?– Based on available data, what is known?– What it isn't (information from prior negative results)?
Important Factors
• Sample preparation– destructive vs. non-destructive– sample size, geometry– vacuum stability
• Is the sample or defect one of kind?• Order of analyses if multiple techniques needed• How clean is the surface?
– Is a technique too surface sensitive?• Controls or references
• Is the defect chemical or physical?• Is it on the surface or buried?• How large is the area of interest?
– compare analysis areas of techniques– sampling depth
• What is the substrate?– insulators vs. conductors– possible spectral interferences for species of interest
(technique specific) • Are quantitative (vs. qualitative) results important?• What detection sensitivity is required?• Is it organic or inorganic?
CNT-IN-01-03A
Defect/Contamination Analysis
Technique Selection and Analysis Design
• Purpose of the analysis: what is the goal?– Good/bad comparison, survey for unknown contaminants,
need quantitative results, images of defects, etc.?
• Description of samples– Include photos, maps, etc.– Expected structure, concentrations, depths, etc.– Previous analysis of similar samples
• Analysis requirements– Depth of analysis (i.e., profile to at least 1mm depth)– Depth resolution– Specific detection limits– Deadline for results, rush requirements– Specific format for results
Information Needed for Analysis
Handling and Shipping of Surface Analysis Samples• Many surface analysis techniques analyze only the top few atomic
layers of the sample so try to minimize handling of the samples as much as possible.
• Handle samples only with clean tweezers and gloves and even then, only touch the edges of the sample.
• When cutting samples avoid using lubricants or coolants. Try to avoid creating particles that could fall onto the area of analysis.
• If solvents are used to rinse samples, they may be washing off not only unwanted surface contamination but also the species of interest. Solvents can also add contaminants in some cases.
• Some techniques have special requirements: e.g. wafers for TXRF typically must double bagged in a cleanroom prior to shipping and should not be reopened unless side a cleanroom.
• Clearly label (or identify in some way) the back side of the samples.
• For the most surface sensitive techniques, avoid placing the samples so they are directly touching plastic bags which may outgas organics or transfer material onto the sample surface.
• For transport, samples can be left uncovered, but secure in a container, or they can be wrapped in clean lab wipes, lens tissue or the matte side of Al foil.
• They can then be placed in envelopes, clean glass vials, hard plastic vials or petri dishes. Please avoid vials that have silicone rubber seals or tops.
• Samples can be secured within their containers using small quantities of double-sticky tape, however the tape should not be used too close to the analytical area if possible.
• Most commercial semiconductor-specific shipping and storage products can also be used for small samples (e.g. Fluoroware etc.).
Handling and Shipping of Surface Analysis Samples
© Copyright Evans Analytical Group®
Comparing Analytical Techniques
DepthofAnalysis
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~~
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Characteristic Recommended Methods
Film or Layer Thickness SEM, TEM, AFM, XRR, XRF
Film Stoichiometry & Depth Profile
RBS, AES, XPS, LEXES, XRF, XRD
Morphology or Roughness SEM, AFM, XRR
Bulk Impurities (including atmospherics)
>0.5% EDS, AES, XPS, HFS, <0.5% SIMS, GDMS
Surface Composition
Elemental: XPS, AES Chemical: XPS Organic: TOF-SIMS
Surface Impurities Metallic: TXRF, TOF-SIMS, SurfaceSIMS, XPS, AES
Organic: TOF-SIMS
ThinFilmAnalysis
Comparing Analytical Techniques
Characteristic Recommended Methods
Particles <1µm: SEM-EDS, AES, TEM <10µm: also TOF-SIMS, Raman >10µm: also FTIR, XPS
Residues –Inorganic: SEM-EDS, AES, XPS, TOF-SIMS –Organic: FTIR, Raman, XPS, TOF-SIMS
Wafer Surface Metals –TXRF, SurfaceSIMS, TOF-SIMS
Stains, discolorations, or hazes
–SPM, SEM (physical characterization) –XPS, AES, TOF-SIMS, FTIR, SEM-EDS (elemental/chemical characterization)
General “surface” contamination
XPS, AES, TOF-SIMS, SEM-EDS, FTIR, Raman, TXRF, SurfaceSIMS, GCMS
Contaminants
Comparing Analytical Techniques
Characteristic Recommended Methods
Dopants SIMS, SurfaceSIMS and contaminants
Major Constituents AES, XPS, RBS/HFS, SIMS, TOF-SIMS
Small Areas <10µm: AES
<100µm: AES, SIMS, XPS
Cross Section FIB/Polishing with SEM/EDS, AES, TEM
DepthProfiling
Comparing Analytical Techniques
Characteristic Recommended Methods
Dopants and contaminants
SIMS, SurfaceSIMS, GDMS, ICPMS, IGA
Major Constituents AES, XPS, RBS/HFS, SIMS, TOF-SIMS, XRD,
XRF
Small Areas <10µm: AES
<100µm: AES, SIMS, XPS, XRD, XRF
Cross Section FIB/Polishing with SEM/EDS, AES, TEM
BulkAnalysis
Comparing Analytical Techniques
Analytical Techniques
© Copyright Evans Analytical Group®
Practical Applications of Microanalytical Techniques
• Goal: evaluate information acquired from the same samples by different analytical methods
• Samples: two WSix films deposited by CVD and sputtering processes
Tungsten Silicide
WSix
Polysilicon -190 nm
SiO2 - 200 nm
Si substrate
WSix
SiO2 - 80 nm
Si substrate
CVDsample(WF6 &SiH4Cl2)
Sputteredsample(compositetargetinAr)
• Thickness of WSix layers• Film stoichiometry • Morphology & roughness• Bulk impurities (including atmospherics)• Surface composition / Surface impurities
Properties of interest
• CVD film– RMS roughness: 6 nm– Grain size: 50 nm– Surface area difference: 9.9%
• Sputtered film– RMS roughness: 0.18 nm– Grain size: 10 nm– Surface area difference: 0.02%
• Strength: Quantitative roughness evaluating topography
• Weakness: small analysis area; no elemental information
AFMResults
CVD
Sputtered
Practical Applications of Microanalytical Techniques
• CVD film– Film thickness: 175 nm– Grain size: 50 nm
(columnar grains)• Sputtered film
– Thickness: 170 nm– Grain size: 10 nm
(no columnar structure)
• Strength: thickness, grain size and structure
• Weakness: destructive; noelemental information
FE-SEM Results - cleaved cross sections
CVD
Sputtered
Practical Applications of Microanalytical Techniques
RBS data• CVD film
– composition: W-30.5%; Si-69.5%Si/W ratio: 2.28
– thickness: 164 nm (assumed density)
– density: 8.70 g/cm3 (with FE-SEM thickness)
• Sputtered film– composition: W-27.0%; Si-
72.1%; Ar-0.9% Si/W ratio: 2.67– thickness: 153 nm (assumed
density)– density: 7.53 g/cm3 (with FE-
SEM thickness)
• Strength: standardless quantitation• Weakness: large area
O
1.0
2.0
3.0
4.0
5.0
0.5 1.0 1.5 2.0Energy (MeV)
0
Yie
ld (x
100
0)
160 Degree RBS2.275 MeV He++
Si Substrate
Si in
SiO
2
Si in
WSi
x
Ar*10
W*25
--- CVD__ sputtered
Practical Applications of Microanalytical Techniques
SIMSResults
0.0 0.1 0.2 0.3 0.4 0.5Depth (microns)
1015
1016
1017
1018
1019
1020
1021
1022
Con
cent
ratio
n (a
tom
s/cm
3 )
100
101
102
103
104
105
106
107
108
Seco
ndar
y Io
n C
ount
s
CVD WSix Film
Si
O Cl F
W
H
F C
0.0 0.1 0.2 0.3 0.4 0.5Depth (microns)
1015
1016
1017
1018
1019
1020
1021
1022
Con
cent
ratio
n (a
tom
s/cm
3 )
100
101
102
103
104
105
106
107
108
Seco
ndar
y Io
n C
ount
s
Sputter WSix Film
Si
O
W
H
F
C
Cl
Practical Applications of Microanalytical Techniques
SIMSResults • CVD film– Cu & Na at WSix/poly-Si
interface– C, F & Cl concentrations
higher at WSix/poly-Si interface
• Sputtered film– Na, Cr & Cu at interface,
but not in bulk WSix– Only Cr & C at higher
concentrations in sputtered film
• Strength: sensitivity; bulk/interface contamination
• Weakness: not a survey tool
O- profile results (units of atoms/cm3)
Na Cr Cu
CVD 3E15 <3E14* 1E17
Sputtered 1E15 1E15 2E16
Cs+ profile results (units of atoms/cm3)
C O F Cl
CVD 2E17 5E19 3E17 5E19
Sputtered 1E19 4E19 <1E16* <1E16*
* detection limits for these experiment (not optimized)
Practical Applications of Microanalytical Techniques
XPS/ESCA Results
• Strength: quantitative survey, chemical state• Weakness: sensitivity, large area, won’t detect native Ar+ in film
Surface Concentration (atomic %)
C N O Si W
CVD 29 0.8 38 25 6.7
Sputtered 14 <0.1 39 37 9.5
Practical Applications of Microanalytical Techniques
CVD film• higher surface C; N bound to C• majority of Si bound to O• higher oxidation states for W
(WO3, WO4)
Sputtered film• no N detected above 0.1% • elemental Si and Si bound to O
present equally• more elemental & less oxidized W
Auger• CVD film
– Si/W ratio: 2.28 (based on RBS)– C, O & F detected on film surface– C <0.5%; N, O, F <0.1% below
surface• Sputtered film
– Si/W ratio: 2.58– C & O detected on film surface– C <0.5%; N, O, F <0.1% below
surface
• Strength: survey; small analysis area• Weakness: sensitivity; accuracy of
quantitation
EDS• Sputtered film
– Si/W ratio: 2.78 (RBS gives 2.67)
– ~1% Ar detected (RBS value)
• Strength: sub-surface contaminants, small analysis area; survey
• Weakness: sensitivity; accuracy ofquantitation
AES and EDS Results
Practical Applications of Microanalytical Techniques
• CVD film– Higher CN, F
concentrations– Organic antioxidant (BHT,
C15H23O+)
– WO3, WO4 at higher concentrations
• Sputtered film– Higher surface Na, K
concentrations– Si containing peaks more
intense– More elemental W and WO
• Strength: survey; sensitivity;organic identification
• Weakness: quantitation
TOF-SIMS Results
W
WO BHT(Butylated Hydroxytoluen)
160 180 200 220 2400
200
400
600
800
1000
1200
1400
Tota
l Cou
nts
0
200
400
600
800
1000
1200
1400
160 180 200 220 240
165
182184
186
198200
202
216
219
182
184
186198
200202
PracticalApplicationsofMicroanalytical Techniques
TXRF Results
• Strength: quick, sensitive, surface survey analysis of metals• Weakness: large analysis area; cannot detect low Z elements
Surface Concentration (atoms/cm2)
S Cl Ca Ti Cr Fe Cu Zn
CVD 2E14 4E13 6E12 <5E10 2E11 2E12 <1E10 2E11
Sputtered 9E13 2E13 7E12 1E13 1E12 2E13 5E12 8E11
Practical Applications of Microanalytical Techniques
Characteristic Recommended Methods
Thickness of WSix layers FE SEM, TEM
Film stoichiometry RBS, AES, XPS
Morphology and roughness FE SEM, AFM
Bulk impurities (including atmospherics)
>0.5% EDS, AES, XPS, HFS
<0.5% SIMS
Surface composition/ Surface impurities
Metallic: TXRF, TOF-SIMS, SurfaceSIMS, XPS, AES
Organic: TOF-SIMS, XPS
Practical Applications of Microanalytical Techniques
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