Chemical vapor deposition of silicon carbide in a hot wall reactor.

摘要

The chemical vapor deposition (CVD) of silicon carbide (SiC), prepared in a hot wall tubular reactor at atmospheric pressure, has been investigated experimentally and theoretically. The gas mixture of methyltrichlorosilane (MTS), hydrogen and argon was chosen as the precursor gas. In order to explore the behavior of such a CVD process quantitatively, a detailed finite difference model, which describes the coupled hydrodynamics, mass transport and chemical reaction occurring in the reactor during the deposition, has been developed. In the model analysis, the nonisothermal temperature profile within the reactor, based on experimental measurements, was taken into account. The governing equations in the model formulation were developed in the cylindrical coordinate, and solved numerically along with appropriate boundary conditions. The model predicts the profiles of MTS concentration and deposition rate as functions of the processing variables such as reactor temperature profiles, inlet flow rates of the gas mixture, and inlet MTS mole fraction. Experimentally, evaluations of SiC coatings were conducted at 850{dollar}spcirc{dollar}-1200{dollar}spcirc{dollar}C with a laboratory-scale CVD system.; By combining the model calculations with experimental data of the deposition rates, a kinetic rate expression of CVD-SiC from the gas mixture was obtained. The deposition rate has an Arrhenius-type dependence on temperature and is a first-order with respect to the MTS concentration. Estimated activation energy is 254 kJ/mol. Predicted deposition rate profiles by the model incorporated with this developed kinetic mechanism showed excellent agreement with experimental data over a variety of applied deposition conditions.; The flow rate of gas mixture affects the deposition rate and deposition uniformity more at higher temperatures than at lower temperatures. X-ray diffraction analysis indicated that pure {dollar}beta{dollar}-SiC deposits were obtained only when appropriate deposition temperature and the molar ratios of "(H{dollar}sb2{dollar}+Ar)/MTS" were applied.; In addition, parametric analysis showed that the temperature, temperature gradient and the flow rate are important processing parameters in controlling the deposition uniformity. With the model simulation, optimization of the deposition process becomes conceivable.