Practical Surface Analysis

Transcription

1 Practical Surface Analysis SECOND EDITION Volume 1 Auger and X-ray Photoelectron Spectroscopy Edited by D. BRIGGS ICI PLC, Wilton Materials Research Centre, Wilton, Middlesbrough, Cleveland, UK and M. P. SEAH Division of Materials Metrology, National Physical Laboratory, Teddington, Middlesex, UK JOHN WILEY & SONS Chichester New York Brisbane Toronto Singapore SALLE + SAUERLÄNDER Aarau Frankfurt am Main Salzburg

2 Contents Preface to First Edition Preface to Second Edition 1. A Perspective on the Analysis of Surfaces and Interfaces 1 M. P. Seah and D. Briggs 1.1 Introduction The background to electron beam techniques Auger electron spectroscopy Other techniques The background to photon beam techniques X-ray photoelectron spectroscopy Other techniques The background to ion beam techniques Secondary ion mass spectrometry Secondary neutral mass spectrometry Medium and low energy ion scattering spectroscopies Other techniques Conclusions 13 References Instrumentation 19 J. C. Riviere 2.1 Introduction Vacuum requirements Attaining UHV Sample handling and treatment Sample introduction Sample manipulation Sample treatment Sources X-ray sources Electron sources Ion sources 66 xiii xv

3 vi Contents 2.5 Electron energy analysers Energy resolution Cylindrical mirror analyser (CMA) Concentric hemispherical analyser (CHA) 75 References Spectral Interpretation 85 D. Briggs and J. C. Riviere 3.1 Introduction Nomenclature j-j coupling LS coupling The electron-excited secondary electron spectrum Auger electron spectra The X-ray photoelectron spectrum Primary structure Information from primary structure Secondary structure Time-dependent spectra Angular effects Enhancement of surface sensitivity Single-crystal studies 136 References Depth Profiling in AES and XPS 143 S. Hofmann 4.1 Introduction Non-destructive techniques Destructive techniques Practice of sputter depth profiling with AES and XPS Vacuum requirements Ion gun." Analysing mode: comparison of AES and XPS Quantification of sputtering profiles: principles Calibration of the depth scale (z = f(t)) Calibration of the concentration scale (x =/(/)) Quantitative depth profiles of the chemical State Sputtering profile compared to the original concentration profile: the concept of depth resolution Depth resolution Factors limiting depth resolution and accuracy of profiles Superposition of different contributions to depth resolution Depth dependence of the depth resolution Optimized depth profiling conditions 177

4 Contents 4.5 Special profiling techniques Destructive methods using SAM Non-destructive profiling by Variation of the electron emission angle or the electron energy Deconvolution of sputtering profiles Standard materials for depth profiling Summary and conclusions 193 Acknowledgement 194 References Quantification of AES and XPS 201 M. P. Seah 5.1 Introduction Quantification of AES for homogeneous binary solids Basic formalisms Spectrometer terms The measurement of intensity Quantification of XPS for homogeneous binary solids Basic considerations Spectrometer terms The measurement of intensity and reference data banks Quantification of inhomogeneous samples Imaging and microscopy in AES and XPS Thin or monoatomic overlayers Angle-resolved analysis, inelastic scattering and composition-depth profiles Quantification in sputter-depth profiles and thicker overlayers References Applications of AES in Microelectronics 257 D. W. Harris and R. S. Nowicki 6.1 Introduction Incoming inspection Particle identification Solder preforms and lids Processing Cleaning Passivation Plasma etch residue Layered aluminium alloys Aluminium/gold wire bonds Packaging Gold Solderability 282 vii

5 Vlll Contents Die attach failure Failure analysis Refractory metal silicides Diffusion barriers Bonding problems Aluminium spiking Conclusion: process characterization and quality control 302 Glossary 304 References AES in Metallurgy 311 M. P. Seah 7.1 Introduction Characterization of segregation Measurements on grain boundaries Measurements on free surfaces Theory of segregation The Langmuir-McLean theory for surface and grain boundary segregation in binary Systems The free energy of grain boundary segregation in binary Systems, AG gb The free energy of surface segregation in binary Systems Site competition in simple ternary Systems More complex binary Systems Segregation in ternary Systems Surface segregation in ternary Systems; one species from the gas phase The kinetics of segregation Materials effects of segregation Segregation and basic materials parameters Temper brittleness Stress corrosion cracking; hydrogen and liquid metal embrittlement Stress relief cracking and creep embrittlement Conclusion 351 References Applications of Electron Spectroscopy to Heterogeneous Catalysis T. L. Barr 8.1 Introduction Fundamentals of electron spectroscopy as applied to catalysis Introduction Comparative energy and intensity surveys Novel techniques and topics Chemisorption and basic catalytic studies 372

6 Contents 8.3 Electron spectroscopy and applied catalysis Reviews related to this subject Problems and techniques in the application of electron spectroscopy to catalysis XPS studies of support materials Platinum metal catalysis Zeolites catalytic cracking and other processes Desulphurization and related catalysts Conclusion 428 References Applications of XPS in Polymer Technology 437 D. Briggs 9.1 Introduction Sample handling Instrumentation Spectral Information The information depth Core level binding energies Shake-up satellites Valence band spectra Functional group labelling (derivatization) Application of XPS to polymer surface analysis problems Some general considerations Polymer surface modification Conclusions 477 References 477 Bibliography Uses of Auger Electron and Photoelectron Spectroscopies in Corrosion Science 485 N. S. Mclntyre and T. C. Chan 10.1 Introduction Special aspects of XPS and AES for corrosion studies Surface sensitivity Elemental sensitivities Quantitative analysis Spatial resolution Depth profiling Experimental techniques Chemical effects Review of XPS and AES applications in corrosion science Light metals First-row metals and their alloys Second- and third-row transition metals 515 ix

7 x Contents Protective coatings and inhibitors Conclusion 521 References 521 Appendix 1. Spectrometer Energy Scale Calibration 531 M. P. Seah and G. C. Smith ALI Introduction 531 AI.2 The relation between voltage and energy in electrostatic electron spectrometers 532 AI.3 Calibration in XPS 534 A1.4 Calibration in AES 535 Acknowledgements 539 References 539 Appendix 2. Charge Referencing Techniques for Insulators 541 M. P. Seah, P. Swift and D. Shuttleworth A2.1 Introduction 541 A2.2 XPS 541 A2.2.1 General 541 A2.2.2 Reference via adventitious carbon-based contamination 543 A2.2.3 Deposited surface layers 544 A2.2.4 Implanted noble gas ions 545 A2.2.5 Mixtures 546 A2.2.6 Internal Standards 547 A2.2.7 Low-energy electron flood guns 547 A2.3 AES 550 References 552 Appendix 3. Data Analysis in XPS and AES 555 P. M. A. Sherwood A3.1 Introduction 555 A3.2 Data collection Systems 556 A3.3 Simple data Operations 557 A3.4 Signal-to-noise considerations 558 A3.5 The fitting of data 559 A3.6 Smoothing 561 A3.6.1 Curve fitting 562 A3.6.2 Convolutional algorithms 563 A3.6.3 Fourier transform frequency filtering 565 A3.7 The analysis of overlapping spectral features 565 A3.7.1 Derivative spectra 566 A3.7.2 Deconvolution methods 568 A3.7.3 Maximum entropy methods 569 A3.7.4 Factor analysis method 569 A3.7.5 Pattern recognition method 570

8 Contents A3.7.6 Spectral ratioing method 571 A3.7.7 Difference spectra 571 A3.7.8 Addition spectra 572 A3.7.9 Curve synthesis and curve fitting 572 A Fitting theoretical calculations to valence band spectra 575 A3.8 Background removal 581 A3.8.1 Linear backgrounds 581 A3.8.2 Integral (non-linear) backgrounds 582 A3.8.3 Backgrounds based upon elastic and inelastic loss processes 582 References 583 Appendix 4. Auger Chemical Shifts and the Auger Parameter 587 S. D. Waddington A4.1 Introduction 587 A4.2 The Auger parameter 587 A4.3 Extra-atomic relaxation energies 588 A4.4 Determination of chemical State from the AP 590 A4.4.1 Chemical State plots 590 A4.5 Practical points in the determination of APs and AP shifts 593 References 593 Appendix 5. Photoelectron and Auger Energies and the Auger Parameter: A Data Set 595 C. D. Wagner Data Set 598 Acknowledgement 625 References 625 Appendix 6. Empirically Derived Atomic Sensitivity Factors for XPS Appendix 7. (a) Line Positions from Mg X-rays, by Element 639 (b) Line Positions from AI X-rays, by Element 641 Appendix 8. (a) Line Positions from Mg X-rays, in Numerical Order (b) Line Positions from AI X-rays, in Numerical Order Appendix 9. Kinetic Energies of Auger Electrons: Experimental Data from Spectra Acquired by X-ray Excitation 645 C. D. Wagner Acknowledgement 650 References 650 Index 651 Contents of Volume 2 xi