Applications of XPS, AES, and TOF-SIMS Scott R. Bryan Physical Electronics 1
Materials Characterization Techniques Microscopy Optical Microscope SEM TEM STM SPM AFM Spectroscopy Energy Dispersive X-ray Spectroscopy (EDX) X-ray Diffraction (XRD) Electron Energy Loss Spectroscopy (EELS) Auger Electron Sepctroscopy(AES) X-ray Photoelectron Spectroscopy (XPS) Secondary Ion Mass Spectrometry (SIMS) Fourier Transform Infrared Spectroscopy(FTIR) Raman Spectroscopy Photoluminescence (PL) Dynamic Light Scattering (DLS) 2
Materials Characterization Techniques Microscopy Optical Microscope SEM TEM STM SPM AFM Spectroscopy Energy Dispersive X-ray Spectroscopy (EDX) X-ray Diffraction (XRD) Electron Energy Loss Spectroscopy (EELS) Auger Electron Sepctroscopy(AES) X-ray Photoelectron Spectroscopy (XPS) Dynamic Secondary Ion Mass Spectrometry (D-SIMS) Time-of-Flight Secondary SIMS (TOF-SIMS) Fourier Transform Infrared Spectroscopy(FTIR) Raman Spectroscopy Photoluminescence (PL) Dynamic Light Scattering (DLS) Used for surface, thin film, and interface analysis 3
Surface Chemical Analysis Techniques Depth of Analysis Courtesy of EAG Laboratories 4
Auger Electron Spectroscopy (AES) 5
What Information Does Auger Provide? Surface composition at high spatial resolution Secondary Electron Imaging (3 nm) Elemental analysis (spectra) (8 nm) Elemental imaging (mapping) High energy resolution spectra, imaging and depth profiling Sputter depth profiling Reveals thin film and interfacial composition 6
Semiconductor Defect Identification with Auger S C N O F Al Particle Si 200 600 1000 1400 1800 Kinetic Energy (ev) Auger detects Al particle Si SE 5kV Petal Si C Si C O F O "Petal" Off "Petal" Si 500 1000 1500 2000 Kinetic Energy (ev) Auger detects C & F on thin petal Green=C Red=Al Blue=Si F 5kV Off Petal EDX does NOT detect C & F on 10-15 Å thin petal 7
N(E) cps Auger Chemical State Analysis 350 300 Al KLL Spectra of Native Oxide on Al Foil 1386.9 ev (Al oxide) 0.5% 0.1% 250 200 150 100 1393.4 ev (Al metal) 50 0-50 1350 1360 1370 1380 1390 1400 1410 1420 Kinetic Energy (ev) Auger KLL spectrum of native oxide on Al foil measured on PHI CMA at 0.5% (blue) and 0.1% (red) energy resolution, after background subtraction. 8
Intensity Intensity Si Metal Auger Chemical State Analysis High Energy Resolution Imaging of Semiconductor Chemical States Composite Si KLL A Si KLL image with ROI areas B Si4 IC412_256.map: Pad 41 2012 Sep 22 10.0 kv 10 na FRR 0.00 s Si4/-1 RSF 3462175 PHI Silicide 0.1 % high energy resolution spectral windowed mapping 1605 1615 1625 Kinetic Energy (ev) C 20 µm 20 µm Si KLL Basis Spectra 1137329 LLS fitting from the basis spectra extracted from regions of interest Si Oxynitride Silicide Elemental Si 1604 1608 1612 1616 1620 1624 Kinetic Energy (ev) 9
Auger Chemical State Analysis High Energy and Spatial Resolution Imaging of Semiconductor Chemical States IC.401.sem: Pad 41 2012 Sep 21 10.0 kv 10 na FRR SEM/-1 A SEI SEM IC412_256.map: PHI Pad 41 Si4/-1RSF 4094 B IC412_256.map: PHI Pad 41 2012 Sep 22 10.0 kv 10 na FRR Sep 0.00 22 10.0 s 2012 kv 10 na FRR 0.00 s Si KLL Peak Si4 Area Si4/-1RSF C 3462175 Silicide Si4.ls1 RSF 32297 PHI Oxynitride (blue) 20 µm 20 µm 20 µm Elemental Si (green) IC412_256.map: 20 Pad µm 41 IC412_256.map: 892.8 PHI Pad 41 IC412_256.map: PHI Pad 41 PHI 20 µm 1137329 20 µm 7465 2012 Sep 22 10.0 kv 10 na FRR 2012 Sep 0.00 22 s 10.0 kv 10 na FRR 2012 Sep 0.00 22 s10.0 kv 10 na FRR 0.00 s Si4/-1 D Si4/-1 RSF Si4/-1RSF E Si Oxynitride F Si4.ls2 Si4.ls3 Si4.ls1+Si4.ls2+Si4.ls3 32297 32297 Si Chemical States Elemental Si RSF 47.0 Silicide (red) 20 µm 20 µm 20 µm 20 µm 7465 20 µm 200 µm FOV SEI of a semiconductor bond pad 0.1% energy resolution data 7465 20 µm 0.0 Auger Color Overlay 20kV 10nA 256x256 pixels Green: Elemental Si Blue: Si Oxynitride Red: Silicide 10
PHI 710: Nanoscale Depth Profiling Intensity SEI 60 nm Diameter Si Nanowire Surface Spectrum of Nanowire 1 P O F FOV: 2.0 µm 0.5 µm P from the growth gas is detected on the surface of a Si nanowire Si C Atom % Si 97.5 P 2.5 100 300 500 700 Kinetic Energy (ev) 20 kv, 10 na, 12 nm Beam 11
PHI 710: Nanoscale Depth Profiling Phosphorous (atom %) 500 V Ar sputter depth profiling shows a nonhomogeneous radial P distribution The data suggests Vapor- Solid incorporation of P rather than Vapor-Liquid- Solid P incorporation Depth Profile of the Si Nanowire 3 2.5 2 1.5 1 0.5 0 0 2 4 6 Sputter Depth (nm) 12
X-ray Photoelectron Spectroscopy (XPS) 13
What is XPS used for? Metal We have analyzed: Plastic Paint Glass Ceramic Fabric Semiconductors Biomaterials Composites Mirrors, lenses, windshields, integrated circuits, circuit boards, fruit flies, teeth, heart valves, pacemakers, stents, relay contacts, make-up, shampoo residue on hair, moon rocks, space shuttle tiles, mold, hip joints, dental floss, dirty socks, solid rocket fuel, gaskets, brake pads, lipstick, adhesive labels, paper, ink, Mr. Potato Head, etc. 14
XPS: Quantitative Elemental & Chemical Information c/s -O KLL -O1s -C1s -O2s c/s Atom % C 70.9 O 29.1 % of C 1s CH 62.7 C-O 20.2 O=C-O 17.1 O=C-O C-O C 1s CH 1000 800 600 400 200 Binding Energy (ev) XPS survey spectra provide quantitative elemental information 0 300 295 290 285 280 Binding Energy (ev) High resolution XPS spectra provide quantitative chemical state information 15
Argon Gas Cluster Beam (GCIB) cleaning of Polyimide c/s c/s As received CH x contaminated 1800 1800 After GCIB cleaning 1600 1600 1400 1400 1200 1000 C-N C-O C-C (including contaminants) 45.0 (at.%) of C 1s 1200 1000 C-N C-O C-C 37.9 (at.%) of C 1s 800 800 600 400 N-C=O pp* 600 400 N-C=O pp* 200 200 0 298 296 294 292 290 288 286 284 Binding Energy (ev) 282 280 278 0 298 296 294 292 290 288 286 284 Binding Energy (ev) 282 280 278 16
c/s c/s c/s Argon Gas Cluster Ion Beam (GCIB) cleaning of TiO 2 3.5 4 x 104 3 After cleaning Ti 2p O 1s C 1s 4.5 x 104 4 3.5 After cleaning 6000 5000 As received 2.5 3 4000 2 As received 2.5 2 As received 3000 1.5 1.5 2000 1 0.5 0 475 470 465 460 Binding Energy (ev) 455 450 1 0.5 0 540 535 530 Binding Energy (ev) 525 1000 0 295 After cleaning 290 285 Binding Energy (ev) 280 17
Atomic Concentration (%) XPS Depth Profile of Thin Films 70 60 50 Sputter Depth Profile Oxygen Oxygen Titanium Nitrogen Niobium Sputter depth profile of an architectural glass coating 40 Titanium 30 Silicon Silicon 20 Nitrogen 10 Aluminum 0 50 100 150 200 Sputter Depth (nm)
Atomic Concentration (%) GCIB Depth Profile of Organic LED Layers 100% Sputter Depth Profile of a Graded OLED Test Structure 0% 100 nm Si Native Oxide 100 80 N 1s (BPhen) 10X 10 kv Ar 2500+ Sputtering C 1s N 1s (TCTA) 10X N1s (TCTA) N1s (BPhen) 60 O 1s Si 2p TCTA 40 20 80 60 40 20 0 410 405 400 395 Binding Energy (ev) BPhen Sample courtesy of Prof. Russell Holmes, U of MN 0 0 50 100 150 Sputter Depth (nm) 19
Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) 20
Surface Chemical Analysis Techniques Courtesy of EAG Laboratories 21
What is TOF-SIMS used for? Surface Mass Spectra with MS/MS: Identification of all atomic and molecular species on surface High sensitivity and molecular specificity Imaging 2D elemental and molecular distributions Depth Profiling Elemental and molecular depth distributions FIB-TOF Accurate 3D distributions of heterogeneous materials
Schematic of the PHI nanotof II
PHI nanotof II with MS/MS
Counts TOF-SIMS of a Commercial Polypropylene MS 1 Spectrum of Polypropylene surface 1.2E+6 20 1.0E+6 C 3 H 8 N 23 39 304 Na K 58 8.0E+5 C 7 H 7 91 6.0E+5 69 284 4.0E+5 29 C 9 H 12 N 312 481 2.0E+5 134 256 368 212 0 0 100 200 300 400 500 25
Unambiguous Identification of m/z 304 polymer additive Benzalkonium, m/z 304 8 TOF-SIMS MS/MS Spectrum of Unknown 304.000 4 58.000 91.000 212.000 0 4 8 43.000 57.9 71.000 86.000 97.000 114.000 134.000 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 304-MS2 Pos 91.0 136.2 147.000 160.000 173.000 186.000 199.000 178.0 NIST Library MS/MS Spectrum ESI with QQQ Head to Tail MF=692 RMF=971 212.3 218.000 231.000 244.000 257.000 270.000 283.000 241.9 271.9 Benzyldodecyldimethylammonium 304.3 26
TOF-SIMS Imaging Region 1 Spectrum Primary Ion Beam Chemical Map 1 Total Ion Image Total Area Spectrum m/z Region 2 Spectrum m/z Chemical Map 2 m/z Sample Spectra from selected areas of the total ion image or images from selected peaks of the total area spectrum can also be obtained for complete analysis after data acquisition. 27
O 2 + Ion Gun Sputter Depth Profiling Excellent Comparison between TOF-SIMS vs D-SIMS Layer (Depth Resolution) D-SIMS TOF-SIMS 28
Conclusions Auger Electron Spectroscopy (AES)» Use for highest spatial resolution surface analysis X-ray Photoelectron Sepctroscopy (XPS)» Use for quantification of elements and oxidation states Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS)» Use for identification of organic compounds» Use for trace level surface analysis 29