Modeling and Design of Halide Chemical Vapor Deposition for Silicon Carbide Epitaxial Film Growth

Silicon carbide (SiC) is a superior material for electronic and optoelectronic devices functioning under harsh environment because of its excellent properties. Among multiple processes involved in the fabrication of silicon carbide-based devices, one important step is to deposit SiC films on substrates to acquire the desired functionality. Currently, halide chemical vapor deposition emerges as a potent technique for growing silicon carbide epitaxial layers with a high deposition rate in the range of 50-300 μm/hr. Experimental studies of the silicon carbide halide chemical vapor deposition process suggest that the temperature field, gas velocity field, gas-phase and surface chemistry in the reactor has profound influence on the deposition rate, the quality, and the properties of the as-deposited epitaxial films. In this dissertation, a comprehensive mathematical model is developed for silicon carbide halide chemical vapor deposition process including gas dynamics, heat and mass transfer, gas-phase and surface chemical reaction mechanism, and radiofrequency induction heating. The governing equation system of this model is discretized by finite volume method, and solved by iterative solver to predict the thermal and flow field, gas composition and film deposition rate. Two-dimensional axisymmetric simulations of the deposition process in a horizontal hot-wall reactor using silicon tetrachloride, propane, and hydrogen as precursors are performed over a wide range of operational parameters to quantify the effects of deposition temperature, precursor flow rate and reactor configuration. Special attention is directed to the etching of silicon carbide films by hydrogen chloride and its impact on the film deposition rate at different processing conditions. Simplified chemical reaction mechanism is obtained using two-dimensional study, which makes the threedimensional simulation feasible using available computing resource. Threedimensional simulation is performed to address issues such as the film uniformity and the effects of buoyancy flow and deposition pressure on the film growth. Modified reactor design and process parameters are examined for controlling the reactive gas flow in a reactor chamber and enhancing the deposition rate. Our simulation shows that the formation of hydrogen chloride and the associated etching effect can be reduced by employing a modified gas delivery system