Surface and Thin Film Analysis II: Solving Real Problems in Materials, Nano and Bio

Transcription

1 Surface and Thin Film Analysis II: Solving Real Problems in Materials, Nano and Bio Mariano Anderle Promozione e internazionalizzazione del Sistema Trentino della Ricerca Dipartimento Innovazione, Ricerca e ICT Provincia Autonoma di Trento web: anderle@fbk.eu

2 Vacuum and Surfaces Dynamic and static SIMS Principle Instrumentation Applications Università di Torino, Corso di Laurea in Fisica 27 maggio 2009 Outline I and II XPS, Auger Principle Instrumentation Applications Surface Technique Integrated Use Some examples

3 Vacuum Coverage time t= 3x10-6 /p p pressure in mbar p ~ 10-6 mbar t ~ sec p ~ 10-9 mbar t ~ h t meas < t M.Anderle -SIMS- Università degli Studi di Torino, 26 maggio 2009

4 Vacuum Mean free path l l l 2.3* kt 1 2 d 2 p With p pressure in mbar and l mean free path in meter and T=300K: p ~ 10 3 mbar l ~ 2.3*10-7 m p ~ 10-3 mbar l ~ 2.3*10-1 m p ~ 10-6 mbar l ~ 2.3*10 2 m M.Anderle -SIMS- Università degli Studi di Torino, 26 maggio 2009 p

5 THE CLUSTER LABORATORY

6 Mass Spectrometry Base Process Particles Emission (Sputtering) Particles Emitted Ionization M.Anderle -SIMS- Università degli Studi di Torino, 26 maggio 2009

7 Analytical Modes of SIMS I S i J P Y i i Dynamic SIMS Static SIMS Material removal Elemental analysis Profiling Ultra surface analysis Elemental or molecular analysis Analysis complete before significant fraction of molecules destroyed M.Anderle -SIMS- Università degli Studi di Torino, 26 maggio 2009

8 Dynamic/Static I S i J P Y i i M.Anderle -SIMS-

9 Dynamic, Static and Imaging SIMS The Secondary Ion Mass Spectrometry technique (SIMS) is the most sensitive of all the commonly-employed surface analytical techniques - this is because of the inherent sensitivity associated with mass spectrometric-based techniques. secondary ions and neutrals (atoms and molecules) There are three different variants of the technique: uppermost layer primary ion Dynamic SIMS used for obtaining compositional information as a function of depth below the surface Static SIMS used for sub-monolayer elemental analysis Imaging SIMS used for spatially-resolved elemental analysis M.Anderle -SIMS-

10 Platform Comparison Magnetic Sector (Cameca 6f) Quadrupole (PHI 1010) ToF-SIMS (TOF-SIMS IV) Advantages: - high mass resolution (20000) - high sensibility - good depth resolution - well defined analytical methodology Disadvantages: - related impact energy and angle - sputtering rate modification for grazing angle Advantages: - unrelated impact energy and angle - low impact energy - high depth resolution - well defined analytical methodology Disadvantages: - bad mass resolution (300) - bad sensibility Advantages: - high mass resolution (10000) - high transmission - high lateral resolution - parallel detection Disadvantages: - analytical methodology not well defined - fixed incidence angle M.Anderle -SIMS-

11 M.Anderle -SIMS- Dynamic SIMS: Depth Profile

12 Concentration (at/cm 3 ) 3keV Implant Normalized at 56 Si 2 ptp 1E21 1E20 As/Si 2E15 at/cm 3keV 1.0 kev 0.5 kev 0.3 kev Best detection 1 kev impact. 1E19 1E18 At 300 ev altered layer minimized 1E17 1E Depth (nm) M.Anderle -SIMS-

13 Integrated SiF 4 Signal Per Cycle Growth Rate (A/Cycle) Intensity (A) CsW Counts Characterization of Temperature Effect on Film Growth SIMS Result 4.0x10-10 SiH 4 Exposure H 2 signal Purge WF 6 Exposure SiF 4 signal Purge 4x10 4 3x c 275 c 3.2x x10 4 1x c 175 c 2.4x Depth (nm) 1.6x *10-10 SIMS x * Scan Number Extent of reaction increases with surface temperature thermally activated process MS 1 W. Lei, L. Henn-Lecordier, M. Anderle, G. W. Rubloff, M. Barozzi and M. Bersani, Real-time observation and optimization of tungsten atomic layer deposition process cycle, J. Vac. Sci. Technol. B 24(2) (2006) p /T (K -1 ) 13

14 Mass Spectrum M.Anderle -SIMS-

15 Positive TOF-SIMS Spectrum of PET O O C O C O CH 2 CH Fragments allow the molecular structure of the polymer to be defined. m/z M.Anderle -SIMS- Università degli Studi di Torino, 26 maggio 2009

16 Positive TOF-SIMS Spectrum of PET M O CH CH M H H O C C 341 O (2M+H) O (3M+H) m/z The repeating peak patterns confirm the polymerization structure. M.Anderle -SIMS- Università degli Studi di Torino, 26 maggio 2009

17 Delay [ps] Microelectronics: Low K Materials Low-k for faster interconnects and improved device performances Al + SiO 2 interconnects slower circuit speed time to propagate signal along interconnect between devices is an RC delay metal Al ( 3.0 mw cm) dielectric SiO 2 (K=4.0) Cu ( 1.7 mw cm) low-k (K=2.0) device alone Generation (MFS, µm) Cu + low K interconnects faster low-k is achieved by decreasing bond polarizability (using organosilicate, polymers, ) lowering the density (foamed and porous materials)

18 Microelectronics: Low K Materials low-k matrix resin (PMSSQ) porogen (PMMA co-dmaema) solvents PROCESS FLOW SCHEMATIC spin-casting of porous low-k film spin casting annealing initial cure final cure template formation porogen volatilization MATERIALS characteristics ELECTRICAL PROPERTIES depend on both: STRUCTURE pores quality/quantity transformations & kinetics

19 i nt ensi t y Microelectronics: Low K Materials i nt ensi t y TOF SIMS i nt ensi t y x C x x600 x C x 1 h x600 high mass ions progressively disappear upon annealing Compression Fact or : mass Compression Fact or : mass MSSQ, transformation upon curing SSIMS, negative SI x C x 2 h 0. 6 self-consistent identification of the key species 0. 4 x600 key peaks intensity depends on the annealing T Compression Fact or : mass

20 intensity Microelectronics: Low K Materials C x 3' 125 C x 1h 225 C x 1h 275 C x 1h 325 C x 1h 450 C x 2h pure, 50 C x 3' POROGEN,transformations upon curing Pseudo-DSIMS, negative SI SI species selectively related to PMMA and DMAEMA DMAEMA cleavage and C (90%) remaining transforms by > 325 C PMMA no apparent trasformation until > 325 C 1 D OD CN C2N CNO C5 C6 C8 C9 PMMA fragments DMAEMA ligand porogen backbone NO backbone alteration until > 325 C NO porogen residuals by 450 C CD 2 CD 3 C x CH 2 CH 3 C y C O C O O CD 3 CH 2 N O CH 2 DEDUCTIONS: a different behavior for the ligand / backbone, PMMA / DMAEMA is observed the residual amount of porogen vs curing T can be evaluated CH 3 CH 3 TOF SIMS

21 relative intensity Microelectronics: Low K Materials low-k transformations: the actual chemical/compositional state of MSSQ is depicted by SSIMS polymerization / crosslinking is pointed out by the vanishing of the key species (PMSSQs oligomers) porogen transformations: mechanisms and kinetics are illustrated by the markers related to the PMMA/DMAEMA ligand / backbone appearance of porogen precipitates 10 0 fading of precipitates Several features of MATERIALS TRASFORMATIONS and KINETICS in the FORMATION of porous low-k can be evaluated by means of ToF-SIMS PMSSQ degree of curing Si 7O C 107 H 21 (pos. SI) Si 6O C 105 H 15 (neg. SI) PMMA DMAEMA different behavior for PMMA and DMAEMA MATRIX and POROGEN transformations are COMPETING upon curing. The transformation kinetics can influence the final low-k electrical properties and requires to be evaluated annealing T [ C]

22 M.Anderle -SIMS- Imaging SIMS

23 Images Spatial resolution Spatial resolution

24 M.Anderle -SIMS- Ion sources

25 Microelectronics: Low K Materials TOF SIMS POROGEN,transformations upon curing imaging ToF-SIMS, negative SI POROGEN AGGLOMERATES as spun / curing < 225 C agglomerates density depends on curing T agglomerates composition (PMMA/DMAEMA ligand/backbone) depends on curing T lateral inhomogeneities 225 C < curing < 450 C Field of view: 10.0 x 10.0 mm 2 2 mm DEDUCTION: porogen transformation includes precipitation and segregation phenomena

26 M.Anderle -SIMS- Images

27 Images AgBr microcrystals Br red I yellow Cl white Dopant segregation at grain boundaries of alumina M.Anderle -SIMS-

28 Images Localization of In and Al in kidney cells M.Anderle -SIMS-

29 M.Anderle -SIMS- Images

30 M.Anderle -SIMS- Images

31 Main advantages and drawbacks ADVANTAGES Sensitivity 1ppm-1ppb All elements are detectable Isotopic detection Good depth resolution Lateral resolution Quantification Insulators are analyzable DRAWBACKS Ion yield up to 6 orders of magnitude Strong matrix effects Depth resolution depends on sample morphology Specific standards are required Destructive technique

32 Ejected Electrons Elastic reflected electrons (BE) Secondary electrons (SE) Differentiated Auger spectrum Auger electrons BE which lost characteristic energy: core level ionization plasmon excitation Kinetic Energy (ev)

33 Escape depth l as a function of electron energy

34 XPS-ESCA X-ray Photoelectron Spectroscopy Electron Spectroscopy for Chemical Analysis

35 XPS electrons (E 0, k 0, s) electrons (E, k, s) atoms (E 0, k 0, Z) ions (E 0, k 0, Z) sample atoms (E, k, Z) ions (E, k, Z) e.m.radiation (hn 0, k 0, polarization) e.m. radiation (hn, k, polarization)

36 Principle Base principle of the technique is the photoelectric effect

37 Principle

38 Principle Electrons ejected from the solid surface keep memory of the chemical element are coming from! Beeing able to discriminate photoelectrons with different energy means to measure the chemical composition of the solid surface!

39 Apparatus Electron Energy Analyser e - Detector Source e - hn Sample Chamber Load Lock Pumping System

40 Vacuum To avoid the electron collisions in the path from surface to analyzer => P<10-3 Pa To avoid surface contamination during the measurements => P<10-6 Pa => The electron spectroscopy techniques utilize Ultra High Vacuum (UHV) conditions

41 Source Analyser E k hn F Vacuum Level Fermi Level E k =hn - E b - F Core level hn=> X Photons => XPS => Core Level UV Photons => UPS => Valence Band

42 Source E k = f ( E B ) E B is specifically related to the chemical element where the electron is coming from! measuring E k of the ejected electrons we can study the elemental chemistry of the sample surface. the photoelectronic peak width E k is directly correlated to the width of source peak hn, beeing the core level peak negligible and the work function F constant.

43 Source Main features: hn ~ 1 kev FWHM < 1 ev Intense beam Compatible with UHV

44 Source

45 Source The presence of a background radiation (Bremsstrahlung) limits the energy resolution. An aluminum foil between the source and the sample helps to reduce this Bremsstrahlung effects!

46 Source Monocromatic source

47 Source To focus monocromatic X ray beam on the sample, quartz crystal, X ray source and sample have to stay on the same circle (Rowland circle).

48 Other sources UV Sources Gas discharge He I (21.2 ev), He II (40.8 ev) Syncrotron radiation Monocromatic light with high intensity and variable energy

49 Analyzer CHA - Concentric Hemisphere Analyzer V 2 - V 1 = U k = U e (R 2 /R 1 - R 1 /R 2 )

50 OPTIMISATION OF SOFT TISSUE ADHESION TO DENTAL IMPLANTS Implanted titanium screw polished and smooth transmucosal collar abutment of titanium alloy integrin receptor gingival cell membrane polished cervical margin Peptide adhesion rough endosseous part (pure titanium) titanium alloy plasma treatment for -NH 2 introduction 26/05/

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54 Resistance to transverse force component

55 Shorter to avoide neurological problems

56 Deporter, D.A., Todescan, R. et al. Length (mm) # Used # Failure % Failure , ,5 Overall 5 year failure rate = 4,6%

57 A Biological Functionalization to Stimulate the Soft Tissue Adhesion - Titanium alloy surface coating using a plasma assisted chemical vapor deposition process (PACVD) to reduce ion release from titanium and provide an amine-containing layer with adequate stability; - PEG molecules immobilization creating a protein-resistant (nonfouling) surface; - Cell adhesive, RGD-containing peptides immobilization stimulating the formation of the biological seal between the soft tissue and the implant.

58 Counts Spectrum O XPS survey spectrum Ti N C Binding energy (ev) UHV Plasma treatmentson Ti Al V alloy surface for primary amine (NH 2 ) group links

59 Counts Spectrum 9000 NH other N species 6000 NH Binding energy (ev) UHV Plasma treatmentson Ti Al V alloy surface for primary amine (NH 2 ) group links

60 ECM proteins and integrin receptors Fibronectin GLY-ARG-GLY-ASP- -SER-TYR-CYS b RGD Adhesion Peptide

61 Titanium alloy functionalization: Overview Step 1: amide bond through the N-hydroxysuccinimide ester (NHS) Step 2: thiol chemistry (Vinylsulfone) Fluorescent derivative PEG: molecules/cm 2

62 Titanium alloy functionalization: XPS analysis?

63 Titanium alloy functionalization: Human gingival cells (HGF-1) adhesion titanium alloy a RGD modified titanium alloy b b1 cells density on different substrates a1 TiC+pep Ti Ti+pep TiC Cell images obtained with a laser scan microscope (a and b) and with a scanning electron microscope (a1 and b1) cell/cm 2 Incubation 24 h in serum free medium plus cycloheximide (25 ug/ml)

64 Carbon spectrum Oxygen spectrum Electron spectroscopy (ESCA) analysis of chitosan films chitosan is obtained from chitin by deactylation. Chitin Chitosan Nitrogen spectrum OH OH CH 2 CH 2 CH O CH O O - CH CH + CH CH O + O OH - C O CH CH CH CH CH 3 OH O C NH OH NH 2 n CH 3 n

65 Spectrum Different energy lines (different values of E B ) describing different core levels characteristic of the specific material (Pd). Auger line too!

66 CHEMICAL SHIFT

67 Quantification Relative sensitivity factors

68 Depth Profiling

69 Depth Profiling

70 Spectromicroscopy Increasing the lateral resolution of the technique focusing the X rays on a small surface area detecting the electrons from a small surface area

71 Spatial mode

72 Microelectronics: Oxynitrides 0.25 mm 0.10 mm Oxynitrides advantages with respect to conventional SiO 2 : good masking characteristic against impurity and dopant diffusion better resistance to dielectric breakdown better resistance to radiation damage and carrier injection suitable dielectric constant good technological compatibility with new generation materials

73 Microelectronics: Oxynitrides Precursor: Thermal treatment: Reoxidation: N 2 O NO Dry Wet Furnace RTA Sample # Oxidation Precursor Temperature Time 1 Dry N 2 O T2 t 2 Dry N 2 O T3 t 3 Dry N 2 O T3 2t 4 Wet N 2 O T2 t 5 Wet N 2 O T3 t 6 Dry NO T1 1.5t 7 Dry NO T1 3t 8 Dry NO T1 6t 9 Dry NO T2 3t 10 Dry NO T2 6t Thickness 10 nm SiO 2 SiO x N y Nitrided region Si

74 Microelectronics: Oxynitrides Dynamic SIMS Vacuum: <10-7 Torr Sputtering Rate: Å/s Primary Ions Energy: kev Primary Beam Current Density: na/cm 2 ma/cm 2 Useful to obtain: Depth Profile Mass Spectra Bulk Analysis Ion Images

75 Microelectronics: Oxynitrides Biomaterials surface chemical composition chemical bonds DETECTOR E K h n E B = 90 d = 5-6nm = 165 d = 2-3nm X RADIATION PHOTOELECTRONS XPS (X-ray Photoelectron Spectroscopy)

76 Counts (a.u.) Microelectronics: Oxynitrides Dynamic SIMS CsN + CsO + CsSi + Cs 2 N + Cs 2 O + Cs 2 Si Depth (A)

77 Concentration (at/cm 3 ) Microelectronics: Oxynitrides Dynamic SIMS Counts SiO 2 /Si interface Si sample 1 sample 2 sample 3 sample 4 sample N 2 O Distance to Interface (nm)

78 Concentration (at/cm 3 ) Microelectronics: Oxynitrides Dynamic SIMS Counts SiO 2 /Si interface Si sample 6 sample 7 sample 8 sample 9 sample NO Distance to Interface (nm)

79 Atomic Concentration (%) Microelectronics: Oxynitrides 4 SiO 2 /Si interface Nitrogen Profiles sample 1 sample 2 sample 3 sample 4 sample 5 sample 8 sample 9 sample Residual thickness (nm) XPS (X-ray Photoelectron Spectroscopy)

80 Microelectronics: Oxynitrides Sample # N integral (at/cm 2 ) SIMS peak concentration (at/cm 3 ) Peak position (nm) XPS peak concentration (%) x x x x x x x x x x x x x x x x x x x x

81 Photoemission Intensity (a.u.) E N1s (ev) Microelectronics: Oxynitrides N 1s interface sample 3 sample sample 1 sample 2 sample 3 sample 4 sample 5 sample 8 sample 9 sample 10 SiO 2 /Si interface E N1s in Si 3 N 4 peak bulk Binding Energy (ev) Residual Thickness (nm) XPS (X-ray Photoelectron Spectroscopy)

82 Surface and Interface Analysis TECHNIQUE XPS AES UPS SIMS TOF-SIMS SNMS XRD Source X-Ray (Mg, Al) Electrons Photons UV (HeI, HeII) Ions Ions Ions X-Ray (Cu) Particle Lateral Resolution Photo- Electrons Auger Electrons Photo- Electrons Secondary Ions Secondary Ions Neutrals postionized X-Ray 10 µm 0-2 µm No 0.5 µm 0-1 µm No No Sensitivity 0.1 % at. 0.1% at. Sampling Depth Main Features 2 20 atomiclayers Information on chemical bond 2 20 atomiclayers High spatial resolution Parameter without meaning 2 3 atomiclayers High sensitivity to valence band % at. 2 3 atomiclayers High sensitivity to elements % at. 2 3 atomiclayers Information on surface chemistry % at. 2 3 atomiclayers Elemental Sensitivity & Easy quantification 0.5 % at. 50 µm Structural Information SCIENTA 200 Physical Electronics PHI 590 PHI 4200 Physical Electronics PHI 545 CAMECA IMS 4f CAMECA SC Ultra CAMECA ION TOF IV Leybold Heraeus INA 3 Instrument at ITCirst Italstructures

83 A E S AES Auger Electron Spectroscopy

84 AES electrons (E 0, k 0, s) electrons (E, k, s) atoms (E 0, k 0, Z) ions (E 0, k 0, Z) sample atoms (E, k, Z) ions (E, k, Z) e.m.radiation (hn 0, k 0, polarization) e.m. radiation (hn, k, polarization)

85 Principle A E S Possible de-excitation processes due to electron bombardment

86 Auger and fluorescence efficency for a K vacancy as a function of atomic number, Z

87 Auger (continuos) and fluorescence (dashed) efficiency for K, L, M vacancies as a function of atomic number, Z

88 AES A E S

89 AES A E S

90 AES Analytical information from: Peak energy ==> What (qualitative) Peak shape and energy ==>How (chemistry) Peak intensity ==> How much (quantitative)

91 AES Spectrum A E S

92 Transition elements 3d

93 Transition elements 3d Characteristic features LMM triplet: L 3 M 2,3 M 2,3 L 3 M 2,3 V L 3 VV Peak M 2,3 VV at lower energy M 2,3 VV L 3 M 2,3 M 2,3 L 3 M 2,3 V L3 VV

94 dn(e)/de N(E) Energy ==> information about the chemical elements Ni Ni Ni O Ni S Cl C Kinetic Energy (ev) Ni S Cl C Ni Ni O Ni Kinetic Energy (ev)

95 dn(e)/de N(E)/E dn(e)/de N(E)/E Intensity [arb. units] Auger line energy and shape ==> information about element chemistry Example: Si LVV Silicon Oxide Silicon Oxide diamante carbonio amorfo grafite policristallina Kinetic Energy [ev] Example: C KVV Kinetic Energy [ev] Elemental Silicon Kinetic Energy [ev] Elemental Silicon Kinetic Energy [ev] Kinetic Energy [ev]

96 Analyzer A E S CMA Cilindric Mirror Analyzer

97 AES apparatus A E S

98 AUGER depth profiling A E S

99 concentrazione atomica relativa Ni1 Cr2 O tempo di sputtering [min] Cr 50nm Ni 65nm Cr

100