| The chemical vapor deposition of silicon carbide in the {dollar}rm CHsb3SiClsb3{dollar}-H{dollar}sb2{dollar} system was investigated. First, a thermodynamic analysis was made, to develop CVD SiC stability diagrams, and to determine the most prevalent gas species. Second, a mathematical model was developed which can predict the relevant transport phenomena, and resultant SiC deposition profiles, on either fibrous or disc shaped substrates. Finally, experiments were carried out to determine the relationship between process controllable parameters and the coating morphology.; Thermodynamic equilibrium calculations were carried out on the Si-C-H-Cl system over a wide range of system temperature, pressure, and composition. The most prevalent gas species were H{dollar}sb2{dollar} and HCl, indicating that the net decomposition of CH{dollar}sb3{dollar}SiCl{dollar}sb3{dollar} to form SiC and HCl adequately describes the system. CVD stability diagrams were calculated, indicating the composition of the condensed phase as a function of T, P, and gas composition. Increased temperatures or H{dollar}sb2{dollar}:CH{dollar}sb3{dollar}SiCl{dollar}sb3{dollar} ratios result in decreased amounts of C co-deposition.; A mathematical model was developed to predict the transport of mass, momentum, heat, and gas species within a vertically-oriented hot-walled CVD reactor. Deposition profiles were predicted along the surfaces of substrates, and compared to experimentally determined deposition profiles. Good agreement was obtained between the experimental and predicted deposition profiles.; Experiments were conducted to determine the relation between the morphology of the deposited SiC and the experimentally controllable parameters of temperature and H{dollar}sb2{dollar}:CH{dollar}sb3{dollar}SiCl{dollar}sb3{dollar} ratio. The morphology of the SiC was independent of temperature over the examined range. A strong dependence of SiC morphology on H{dollar}sb2{dollar}:CH{dollar}sb3{dollar}SiCl{dollar}sb3{dollar} ratio was observed. Nodular SiC formed under intermediate gas compositions, while contorted whiskers grew at high and low gas ratios. The growth of whiskers in the enriched and dilute MTS gas trials is explained according to a diffusion-controlled growth mechanism. |
