Diamond Film Deposition in a Radio-Frequency Thermal Plasma

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Among the processes which have been demonstrated for chemical vapor deposition (CVD) of diamond films, the radio-frequency thermal plasmas approach is one of the most promising in terms of high deposition rates, lack of contamination, and good film uniformity over large substrate areas. The present work is directed at development of a fundamental understanding of the mechanisms of diamond-film CVD in an rf thermal plasma reactor and use of that understanding for definition of process conditions which will enable high-rate deposition of high- quality diamond films on various substrates of industrial interest. Experiments will be conducted to characterize the effects of controllable process parameters on film properties and deposition rates. On-line measurements of temperatures and chemical species concentrations in the boundary layer adjacent to the substrate and at the substrate surface itself will be obtained using optical pyrometry, laser-induced fluorescence, and gas chromatography of samples gathered with probes. Analyses of the deposited films will be obtained from optical microscopy, scanning electron microscopy, Raman spectroscopy, and X-ray diffraction. A numerical model which specifically corresponds to the experimental reactor and conditions and which predicts film growth rates as a function of process variables will be developed in parallel with the experimental studies. Diamond is a superlative material with respect to mechanical, thermal, optical, electrical, and acoustic properties. Deposition of diamond films on various substrates (various materials and shapes) is a rapidly growing field with a potentially huge market in such areas as machine cutting tools, abrasives, bearings, lasers, lenses/mirrors, and microelectronic devices. The ability to produce uniform pure diamond coatings at high deposition rates is critical to future developments in this area. This program represents an important step in exploration of the rf thermal plasma approach to such production, and will additionally advance the knowledge and technology base for other potential applications of rf thermal plasma CVD processes.