MS482 Materials Characterization ( 재료분석 ) Lecture Note 12: Summary. Byungha Shin Dept. of MSE, KAIST

Transcription

1 2015 Fall Semester MS482 Materials Characterization ( 재료분석 ) Lecture Note 12: Summary Byungha Shin Dept. of MSE, KAIST 1

2 Course Information Syllabus 1. Overview of various characterization techniques (1 lecture) 2. Chemical analysis techniques (8 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 (4 lecture) 3.1. Rutherford Backscattering Spectrometry (RBS) 3.2. Secondary Ion Mass Spectrometry (SIMS) 4. Diffraction and imaging techniques (7 lectures) 4.1. Basic diffraction theory 4.2. X-ray Diffraction (XRD) & X-ray Reflectometry (XRR) 4.3. Scanning Electron Microscopy (SEM) & EDS 4.4. Transmission Electron Microscopy (TEM) 5. Scanning probe techniques (1 lectures) 5.1. Scanning Tunneling Microscopy (STM) 5.2. Atomic Force Microscopy (AFM) 6. Summary: Examples of real materials characterization (1 lecture)

3 Technique Selection and Analysis Design Important Factors 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)? 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

4 Technique Selection and Analysis Design Defect/Contamination Analysis 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

5 Information Needed for Analysis 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 1µm depth) Depth resolution Specific detection limits Deadline for results, rush requirements Specific format for results

6 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.

7 Handling and Shipping of Surface Analysis Samples 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.).

8 Comparing Analytical Techniques Depth of Analysis ~ ~ ~ ~ Copyright 2007 Evans Analytical Group

9 Comparing Analytical Techniques Thin Film Analysis Characteristic Film or Layer Thickness Film Stoichiometry & Depth Profile Morphology or Roughness Bulk Impurities (including atmospherics) Surface Composition Surface Impurities Recommended Methods SEM, TEM, AFM, XRR, XRF RBS, AES, XPS, LEXES, XRF, XRD SEM, AFM, XRR >0.5% EDS, AES, XPS, HFS, <0.5% SIMS, GDMS Elemental: XPS, AES Chemical: XPS Organic: TOF-SIMS Metallic: TXRF, TOF-SIMS, SurfaceSIMS, XPS, AES Organic: TOF-SIMS

10 Comparing Analytical Techniques Contaminants Characteristic Particles Residues Recommended Methods <1µm: SEM-EDS, AES, TEM <10µm: also TOF-SIMS, Raman >10µm: also FTIR, XPS Inorganic: SEM-EDS, AES, XPS, TOF-SIMS Organic: FTIR, Raman, XPS, TOF-SIMS Wafer Surface Metals TXRF, SurfaceSIMS, TOF-SIMS Stains, discolorations, or hazes General surface contamination SPM, SEM (physical characterization) XPS, AES, TOF-SIMS, FTIR, SEM-EDS (elemental/chemical characterization) XPS, AES, TOF-SIMS, SEM-EDS, FTIR, Raman, TXRF, SurfaceSIMS, GCMS

11 Comparing Analytical Techniques Depth Profiling Characteristic Dopants Major Constituents Small Areas Cross Section Recommended Methods SIMS, SurfaceSIMS and contaminants AES, XPS, RBS/HFS, SIMS, TOF-SIMS <10µm: AES <100µm: AES, SIMS, XPS FIB/Polishing with SEM/EDS, AES, TEM

12 Comparing Analytical Techniques Bulk Analysis Characteristic Dopants and contaminants Major Constituents Small Areas Cross Section Recommended Methods SIMS, SurfaceSIMS, GDMS, ICPMS, IGA AES, XPS, RBS/HFS, SIMS, TOF-SIMS, XRD, XRF <10µm: AES <100µm: AES, SIMS, XPS, XRD, XRF FIB/Polishing with SEM/EDS, AES, TEM

13 Analytical Techniques Copyright 2007 Evans Analytical Group

14 Practical Applications of Microanalytical Techniques Tungsten Silicide Goal: evaluate information acquired from the same samples by different analytical methods Samples: two WSi x films deposited by CVD and sputtering processes CVD sample (WF 6 & SiH 4 Cl 2 ) WSi x Polysilicon -190 nm SiO nm Si substrate Properties of interest Sputtered sample (composite target in Ar) WSi x SiO 2-80 nm Si substrate Thickness of WSi x layers Film stoichiometry Morphology & roughness Bulk impurities (including atmospherics) Surface composition / Surface impurities

15 Practical Applications of Microanalytical Techniques CVD Sputtered AFM Results 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

16 Practical Applications of Microanalytical Techniques FE-SEM Results - cleaved cross sections 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; no elemental information

17 Practical Applications of Microanalytical Techniques Yield (x 1000) Degree RBS MeV He ++ RBS data O Si Substrate Si in SiO CVD sputtered Si in WSi x Ar* Energy (MeV) W*25 CVD film composition: W-30.5%; Si-69.5% Si/W ratio: 2.28 thickness: 164 nm (assumed density) density: 8.70 g/cm 3 (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/cm 3 (with FE-SEM thickness) Strength: standardless quantitation Weakness: large area

18 Practical Applications of Microanalytical Techniques SIMS Results CVD WSi x Film Sputter WSi x Film Si Si O Cl F O 10 6 Concentration (atoms/cm 3 ) F W H C Secondary Ion Counts Concentration (atoms/cm 3 ) W C H Secondary Ion Counts F Cl Depth (microns) Depth (microns)

19 Practical Applications of Microanalytical Techniques SIMS Results CVD film Cu & Na at WSi x /poly-si O - profile results (units of atoms/cm 3 ) Na Cr Cu CVD 3E15 <3E14* 1E17 Sputtered 1E15 1E15 2E16 Cs + profile results (units of atoms/cm 3 ) C O F Cl CVD 2E17 5E19 3E17 5E19 interface C, F & Cl concentrations higher at WSi x /poly-si interface Sputtered film Na, Cr & Cu at interface, but not in bulk WSi x Only Cr & C at higher concentrations in sputtered film Sputtered 1E19 4E19 <1E16* <1E16* * detection limits for these experiment (not optimized) Strength: sensitivity; bulk/interface contamination Weakness: not a survey tool

20 Practical Applications of Microanalytical Techniques XPS/ESCA Results Surface Concentration (atomic %) C N O Si W CVD Sputtered 14 < CVD film higher surface C; N bound to C majority of Si bound to O higher oxidation states for W (WO 3, WO 4 ) Sputtered film no N detected above 0.1% elemental Si and Si bound to O present equally more elemental & less oxidized W Strength: quantitative survey, chemical state Weakness: sensitivity, large area, won t detect native Ar + in film

21 Practical Applications of Microanalytical Techniques AES and EDS Results 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 EDS Sputtered film Si/W ratio: 2.78 (RBS gives 2.67) ~1% Ar detected (RBS value) Strength: survey; small analysis area Weakness: sensitivity; accuracy of quantitation Strength: sub-surface contaminants, small analysis area; survey Weakness: sensitivity; accuracy of quantitation

22 Practical Applications of Microanalytical Techniques Total Counts TOF-SIMS Results W WO BHT (Butylated Hydroxytoluen) CVD film Higher CN, F concentrations Organic antioxidant (BHT, C 15 H 23 O + ) WO 3, WO 4 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

23 Practical Applications of Microanalytical Techniques TXRF Results Surface Concentration (atoms/cm 2 ) 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 Strength: quick, sensitive, surface survey analysis of metals Weakness: large analysis area; cannot detect low Z elements

24 Practical Applications of Microanalytical Techniques Characteristic Thickness of WSi x layers Film stoichiometry Morphology and roughness Bulk impurities (including atmospherics) Surface composition/ Surface impurities Recommended Methods FE SEM, TEM RBS, AES, XPS FE SEM, AFM >0.5% EDS, AES, XPS, HFS <0.5% SIMS Metallic: TXRF, TOF-SIMS, SurfaceSIMS, XPS, AES Organic: TOF-SIMS, XPS