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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

~

~~

~

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



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



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



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


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


• 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


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


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


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)


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


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


• 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



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


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