Pulsed-Laser Deposition of Silicon Dioxide Thin-Films Using the Molecular Flourine Laser
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Pulsed-Laser Deposition of Silicon Dioxide Thin-Films Using the Molecular Flourine Laser Brian Douglas Jackson A thesis submitted in conforrnity with the requirements for the degree of Master of Applied Science Graduate Department of Electrical and Computer Engineering University of Toronto O Copyright by Brian Douglas Jackson 1997 395 Wellington Street 395, rue Wellington Ottawa ON KIA ON4 Ottawa ON K1A ON4 Canada Canada Your fila Votre réference Our file Nolre rdldrence The author has granted a non- L'auteur a accordé une licence non exclusive licence alîowing the exclusive permettant à la National Library of Canada to Bibliothéque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in microforni, vendre des copies de cette thèse sous paper or electronic fonnats. la forme de microfiche/nlm, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts from it Ni la thése ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. Thin-Films Using ;he Molecular Fluorine Laser Brian Douglas Jackson Master of Applied Science Degree, 1997 The Department of Electrical and Computer Engineering The University of Toronto Abstract The short-wavelength extension of pulsed-laser deposition (PLD) to the 157-nm F2 laser may enable low-temperature growth of silica films for electronics and photonics applications. This thesis examines the effects of laser fluence, background gas, and substrate temperature on the properties of SiOz films grown for the first time using the F2-laser. The deposited films were characterized by atomic force microscopy, x-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. The strong absorption of 157-nm radiation in fused silica enabled the growth of virtually particulate-free Si02 films by F2-PLD, in contrast to results with longer wavelength lasers. Stoichiometric films were produced in ambient oxygen (4x10'' Ton), which compensated for oxygen loss due to Siondissociation by the 7.9-eV laser photons. Akhough the process parameters were not fully optimized, F2-PLD produced films with comparable properties to the best-previous PLD-grown SiO2 films, but inferior to films deposited by VUV-assisted CVD. 1 would first like to thank my thesis supervisor, Professor Peter Herman, for his ongoing advice during the coarse of this project. Additionally, 1 would like to recognize the financial contributions of NSERC and the Ontario Laser and Lightwave Research Centre. Several individuals provided assistance through the use of diagnostics instruments: Professor Stefan Zukotynski, of the Department of Electrical and Cornputer Engineering, allowed me the use of his FTIR spectrometer and mechanical profilorneter; Dr. Rana Sohdi, of the Surface Science Lab in the Centre for Biornaterials, provided ongoing advice regarding the use of the x-ray photoelectron spectrometer in his lab; and finally, Prof. Cynthia Goh, of the Department of Chemistry, provided the use of her atomic force microscope. 1 would also like to thank my fellow graduate students in the lab: Keith Beckley, Knsten Coupland, Jianhao Yang, David Moore, and Sola Ness. They helped in a variety of ways. Additionally, a high school CO-opstudent under my supervision, Tony Yoo, was a great help in designing and building Our deposition system. Finally, 1 would like to thank my fiancée, Trish, for her ongoing patience and encouragement in the face of adversity. * * Abstract ........................................................................................................................... ii ... Acknowledgements ............................................................................................................ iii .. List of TabIes ................................................................................................................... vil ... List of Figures .................................................................................................................. viii 1. Introduction .............................................................................................................1 1.1 Project Motivation .............................................................................................1 1.2 Thesis Outline ..................................................................................................2 2. Background Information .............................................................................................. 4 2.1 Pulsed-Laser Deposition ....................................................................................4 2.1.1 Basic Mechanisms ..................................................................................4 2.1.2 Advantages and Disadvantages of PLD .................................................6 2.1.3 Applications of PLD .............................................................................. 8 2.2 Laser Ablation .................................................................................................. 10 2.2.1 Overview ..............................................................................................10 2.2.2 Photothermal Ablation .........................................................................10 2.2.3 Photochernical Ablation ....................................................................... 13 2.2.4 Particul@e Generation During Laser Ablation ..................................... 15 2.2.5 Minimization of Particulate Generation ............................................... 17 2.3 Silicon Dioxide Thin-Films ..............................................................................18 2.3.1 Applications .........................................................................................18 2.3.2 Growth Techniques ..............................................................................20 2.4 Pulsed-Laser Deposition of Silicon Dioxide .................................................... 21 2.4.1 Motivation for PLD of Silicon Dioxide ...............................................21 2.4.2 Past Results of SiOz Growth by PLD ................................................... 22 2.4.3 Vacuum-Ultraviolet F2-Laser Ablation of Silicon Dioxide ................. 25 3 . Experimental Procedures ........................................................................................... 30 3.1 Overview .......................................................................................................... 30 3.2 Film Deposition ................................................................................................ 31 3.2.1 The Molecular Fluorine Laser .............................................................. 31 3.2.1.1 Basic Principles of Operation ................................................ 31 3.2.1.2 Ruorine Operation ................................................................. 33 3.2.1.3 Argon Fluoride Operation ......................................................34 3.2.2 Initial Experimental Configuration ...................................................... 34 3.2.3 Follow-up Experimental Configuration ...............................................37 3.2.3.1 F2-PLD Deposition Chamber Design ..................................... 37 3.2.3.2 Experimental Procedure ......................................................... 39 3.3 Film Characterization .......................................................................................41 3.3.1 Surface Roughness .............................................................................41 3.3.1 .1 Atornic Force Microscopy ................................................... 42 3.3.2 Chernical Composition and Structure ................................................42 3.3.3.1 X-ray Photoelectron Spectroscopy ...................................... 42 3.3.3.2 .Fourier-Transfomi Infrared Spectroscopy .............................47 3.3.3 Film Thickness ..................................................................................... 50 3.3.3.1 Mechanical Profilometry ....................................................... 50 3.3.3.2 Fourier-Transform Infrared Spectroscopy ............................. 50 3.3.3.3 X-ray Photoelectron Spectroscopy ......................................51 3.3.4 Film Density .........................................................................................51 4 . ExperimentalResults ................................................................................................ 52 4.1 Overview ..........................................................................................................52 4.2 Surface Roughness ........................................................................................... 53 4.4 Chernical Structure .......................................................................................... 62 4.4.1 Wide-Range FïIR Transmission Spectra (450-5200 cm-') ................. 62 4.4.2 Si-O-Si Asymmetric Stretching Mode Peak Spectra ........................... 65 4.5 Film Thickness, Deposition Rate. and Density ................................................ 69 5 . Discussion ..................................................................................................................72 5.1 Overview ..........................................................................................................72