A computational model for the hot-filament chemical vapour deposition process to produce diamond films

A two-dimensional computational model for the hot-filament chemical vapour deposition (HFCVD) process to produce diamond films is presented. The model solves the overall continuity, momentum, energy and species continuity equations inside the reaction chamber of a HFCVD reactor. The gas-phase homogeneous reactions are represented by a simplified reaction mechanism. The model incorporates the catalytic production of H radical at the filament surface. Expressions representing the recombination of the H radical at surfaces and the growth rate of diamond film on the substrate were coupled to the gas-phase transport equations. The computational model was solved numerically by means of a commercial software. The model predictions showed good agreement with the experimental data reported in the literature in terms of both gas temperature and CH₃ concentration profiles along the filament-to-substrate centre distance and with experimental data of the growth rate of diamond films obtained in a laboratory HFCVD reactor. Numerical simulations considering one, three and five filaments were conducted. The results showed that as the number of filaments increases, the concentration of CH₃ in the reaction chamber increases as well as the rate of growth of the diamond film being produced. The shape and dimensions of the reaction chamber, filaments and substrate were found to significantly affect the model predictions. Therefore, the use of computational fluid dynamics techniques in the analysis of HFCVD reactors must be exercised with caution.