Thermodynamics of the production of condensed phases in the CVD of methyltrichlorosilane pyrolysis

Production conditions of the condensed phases (β-SiC, silicon, and graphite) in the CVD of methyltrichlorosilane (MTS) pyrolysis are investigated in detail with thermodynamic analyses based on a relatively complete and refined database. Production of the condensed phases is examined as a function of temperature, pressure, and the initial gas ratio of H₂/MTS. The results show that the composition of the condensed phase is quite sensitive to both temperature and the molar ratio of H₂/MTS, whereas it is less sensitive to pressure. The ideal conditions for the deposition of β-SiC are temperatures between 1300 and 1500K, H₂/MTS ratios between 10 and 10₅, and with pressures as low as convenient. The co-deposition of C or Si with β-SiC is mainly controlled by the ratio of H₂/MTS. The co-deposition of C with β-SiC should be in low H₂/MTS ratios (<10) and the codeposition of Si with β-SiC needs high H ₂/MTS ratios (>10₄). The results are in very good agreement with experimental findings and previous theoretical investigations. The present work is also instructive as to the experimental conditions relating to continuous regions of temperatures, pressures, and the H₂/MTS ratios.