MECHANICAL PROPERTIES OF SILICON-BASED FILMS FABRICATED BY PECVD A STUDY OF THE MECHANICAL PROPERTIES OF SILICON-BASED THIN FILMS DEPOSITED BY ECR-PECVD AND ICP-CVD By OWEN TAGGART, B.ENG. A Thesis Submitted to the School of Graduate Studies in Partial Fulfillment of the Requirements for the Degree Master of Applied Science McMaster University © Copyright by Owen Taggart, April 2013 McMaster University MASTER OF APPLIED SCIENCE (2013) Hamilton, Ontario (Engineering Physics) Title: A Study of the Mechanical Properties of Silicon-Based Thin Films Deposited by ECR-PECVD and ICP-CVD AUTHOR: Owen Taggart SUPERVISOR: Professor Peter Mascher Number of pages: xv, 151 ii Abstract Silicon-based dielectric thin films including amorphous hydrogenated aluminium-doped silicon oxides (a-SiAlxOy:H), amorphous hydrogenated silicon nitrides (a-SiNx:H), and amorphous hydrogenated silicon carbides (a-SiCx:H) were deposited by remote plasma chemical vapour deposition (RPECVD) techniques including electron cyclotron resonance plasma enhanced chemical vapour deposition (ECR-PECVD) and inductively-coupled-plasma chemical vapour deposition (ICP-CVD) on silicon (Si) wafers, soda-lime glass microscope slides, and glassy carbon (C) plates. Aluminium (Al) in the SiAlO films was incorporated by way of a metalorganic Al(TMHD)3 precursor. Thickness, refractive index, and growth rate of the films were measured using variable angle spectroscopic ellipsometry (VASE). Film composition was measured using energy dispersive X-ray spectroscopy (EDX) for the SiAlO films and Rutherford backscattering spectrometry (RBS) for the SiCx films. Elastic modulus and hardness of the SiAlO and SiCx films were measured using nanoindentation and their adhesion was characterized via progressive load scratch testing. All films were observed to be optically transparent at near-IR and red wavelengths with many SiNx and SiCx films exhibiting significant optical absorption above 2.25eV. Modification of a previously developed deposition recipe produced doubled growth rates in SiNx and SiCx films. SiAlO films were produced with up to 1.6±0.1at% aluninium (Al) incorporation, while SiCx films with composition ranging from SiC0.25:H to SiC2:H could be produced depending on the growth gas flow ratios. SiAlO films exhibited hardness and reduced modulus (H and E) up to 8.2±0.4 and 75±2GPa, respectively; H and E for the SiCx films reached 11.9±0.2 and 87±3 GPa. Initially, adhesion to Si wafers was extremely poor with films delaminating at loads of 1.5±0.3N when scratched with a 3/16” alumina (Al2O3) sphere; implementation of a rigorous pre-deposition surface cleaning procedure produced films showing only cracking and no delamination up to 30N loads vs. a 200μm radius Rockwell C diamond stylus. iii Acknowledgements This work would not have been possible without the support and guidance of many others. First and foremost I would like to thank my supervisor, Dr. Peter Mascher, for his confidence in my abilities as a researcher, for his insight and suggestions regarding the direction of this work, for making himself constantly available for a quick discussion or email despite an extremely busy schedule, and for delivering the occasional push when it was needed. Without him, this work simply would not exist. Dr. Jacek Wojcik, our research engineer, first suggested to me to the idea of studying the mechanical properties of films produced using our PECVD reactors; without him, this work might have taken an entirely different direction. I am also grateful for his many lessons ranging from Tauc-Lorentz ellipsometric modelling to how to find a vacuum leak with a bottle of methanol, and for his ceaseless labours in the maintenance and improvement of the reactors. Shahram Tavakoli, research engineer, was always willing to help me sort out any “stupid nonsense” I ran into with the reactors (or anything else in the lab). Steve Koprich and Chris Butcher, of the Canadian Centre for Electron Microscopy (CCEM), were very helpful and informative during my time there. Jack Hendriks and Lyudmila Goncharove assisted with the RBS measurements. I must also thank Sjoerd Roorda and Martin Chicoine for their valiant attempts to find aluminium in my films using HIERDA. iv I would like to thank Drs. Ludvik Martinu and Jolanta-Ewa Klemberg Sapieha for making available to me their characterization equipment at the École Polytechnique de Montréal and for providing helpful direction in the mechanical and tribological characterization of my coatings, a field with which I had very little familiarity coming from an Engineering Physics background. Their graduate students Thomas Schmitt and Duanjie Li performed the nanoindentation measurements. Etienne Bousser was very helpful in the interpretation of my scratch and wear test results. Doris Stevanovic provided valuable cleanroom training and lessons in handling chemicals as well as friendly conversation. Zahra Khatami and (soon to be Dr.) Patrick Wilson, of my research group, were a pleasure to bounce ideas off or simply have a nice chat with. Last but not least I would like to thank my parents, William Taggart and Sydne Conover-Taggart, for their support and encouragement when things looked grim as well as my sister Erryl Taggart for her light-hearted conversation and *checking in on me during the writing of this work. Without them, I’m not sure that I ever would have started, let alone finished, the writing of this piece. v Contents Abstract .................................................................................................................. iii Acknowledgements ................................................................................................ iv List of Figures ......................................................................................................... x List of Tables ....................................................................................................... xiv Acronyms .............................................................................................................. xv 1 Introduction ..................................................................................................... 1 1.1 Objective of this Research ........................................................................ 5 1.2 Document Outline .................................................................................... 6 2 Mechanical Properties of Silicon-Based Thin Films ...................................... 7 2.1 Selected Thin Film Mechanical Properties .............................................. 7 2.1.1 Elastic Modulus ................................................................................ 7 2.1.2 Hardness ............................................................................................ 9 2.1.3 Adhesion ......................................................................................... 11 2.1.4 Wear Resistance .............................................................................. 14 2.2 Studies of Silicon-Based PECVD Thin Films ........................................ 16 2.2.1 Silicon Aluminium Oxynitride (SiAlON) Films ............................. 17 2.2.2 Silicon Nitride (SiNx) Films ............................................................ 20 vi 2.2.3 Silicon Carbide (SiCx) Films........................................................... 23 3 Sample Growth and Preparation ................................................................... 27 3.1 Substrates ............................................................................................... 27 3.2 Surface Cleaning .................................................................................... 30 3.3 Plasma Enhanced Chemical Vapour Deposition (PECVD) ................... 34 3.3.1 Induction Coupled Plasma Enhanced Chemical Vapour Deposition (ICP-CVD) .................................................................................................... 39 3.3.2 Electron Cyclotron Resonance Plasma Enhanced Chemical Vapour Deposition (ECR-PECVD) ........................................................................... 42 3.4 Annealing Treatments ............................................................................ 48 4 Characterization Techniques ......................................................................... 49 4.1 Variable Angle Spectroscopic Ellipsometry .......................................... 49 4.2 Ion Beam Analysis ................................................................................. 57 4.2.1 Rutherford Backscattering Spectrometry ........................................ 57 4.2.2 Elastic Recoil Detection .................................................................. 61 4.3 Energy-Dispersive X-ray Spectroscopy ................................................. 63 4.4 Nanoindentation ..................................................................................... 69 4.5 Scratch Testing ....................................................................................... 74 vii 4.6 Pin-on-Disk Testing ............................................................................... 79 5 Silicon Aluminium Oxide (SiAlO) Films ..................................................... 81 5.1 Ellipsometric Characterization ............................................................... 83 5.2 Ion Beam Analysis ................................................................................. 88 5.2.1 Rutherford Backscattering Spectrometry (RBS)............................. 88 5.2.2 Heavy-Ion