Plasma etching, the selective removal of materials by reaction with chemically active species formed in a glow-discharge, is widely used by the electronics industry because of the advantages over 'wet' processes. The full potential has yet to be realised because chemical processes occuring in the plasma and at the plasma/substrate interface are incompletely understood. In this work attention was focussed on the accumulation of polymers on surfaces during plasma etching in fluorocarbon gases. An apparatus was designed and constructed to explore the conditions which give rise to these deposits by: i) The detection of the excited species such as CF and CF₂ (by optical emission spectroscopy); and ii) The rate of accumulation or removal of deposits (by means of a quartz crystal microbalance). The gases CF₄, C₂F₆, C₃F₈ and CHF₃ were used at pressures between 200-600mT, together with mixtures with H₂ and a few runs with other gases to vary the partial pressures of etching and polymerizing species. Both substrate effect of, viz silicon and thermally oxidised silicon (SiO₂), and electrode materials effects have been examined. Polymer production from C₃F₈ has been found to be more sensitive to electrode composition than that from CHF₃, but the material formed is overall less thermally stable. On the other hand, polymers produced from C₃F₈ accumulate at similar rates on Si and SiO₂, whereas those from CHF3 show a much greater liklihood of building up on Si than SiO2 . XPS and infra-red spectroscopy have been used to demonstrate that polymers arising from these two gases exhibit marked structural differences, which can be minimised by mixing H₂ with C₃F₈. These effects can be correlated with the decomposition products expected in the plasma.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 6, 2008) Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 1995. / Vita. Includes bibliographical references (leaves [189]-196).

The reactions of iodomethane, diiodomethane, and formaldehyde over stoichiometric, O-terminated, and Cl-terminated α-Cr₂O₃ surfaces, were studied by thermal desorption spectroscopy. Adsorbed formaldehyde forms dioxymethylene species on the nearly-stoichiometric surface that react primarily above 600 K. Dioxymethylene decomposes via a Cannizzaro-type process with dehydrogenation to formate, and hydrogenation to methoxide. Methoxide hydrogenation produces methane and methanol near 670 K. Formate decomposition occurs at 720 K, producing acetylene, carbon monoxide, carbon dioxide and formic acid. The site requirements for these reactions are a cation/anion site pair. When the surface cations are capped with Cl, the reactivity associated with dioxymethylene intermediates above 600 K is not observed. At higher coverages, polymerization to paraformaldehyde is observed on both surfaces, and decomposition to formaldehyde is observed at 400 K in thermal desorption. Iodomethane and diiodomethane are used as sources of methyl and methylene surface species, respectively. Methyl fragments on the stoichiometric surface dehydrogenate to surface methylene and hydrogen as a rate limiting step to produce ethylene and methane at 505 K. On the oxygen-terminated surface, the methyl fragments undergo dehydrogenation and coupling to ethylene at 425 K, undergo oxygen insertion to formaldehyde at 425 K, and produce carbon dioxide, formic acid, and water above 700 K from the dehydrogenation of formate. Methylene fragments on the stoichiometric surface undergo diffusion limited coupling to ethylene at 390 to 490 K and produce methane at 520 K from dehydrogenation. On the oxygen-terminated surface, methylene undergoes oxygen insertion to produce formaldehyde at 450 K, produce carbon monoxide, formaldehyde, and water at 695 K from dioxymethylene dehydrogenation, and produce carbon dioxide, formic acid, and water above 700 K from the dehydrogenation of formate. / Ph. D.

No description available.

No description available.

Graduation date: 1995

Thesis (Ph. D.)--Oregon Graduate Center, 1982.

No description available.

Thesis (M.S.) in Biochemistry--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaves 65-72).