Simulation-based Design, Optimization, and Control of Silicon Carbide and Gallium Nitride Thin Film Chemical Vapor Deposition Reactor Systems
Parikh, Rinku Pankaj
Adomaitis, Raymond A
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Computer models are routinely used for the design and analysis of chemical vapor deposition reactors. Accurate prediction of epitaxial thin film properties requires complete knowledge of the chemical reaction kinetics that occurs in the gas phase and at the deposition surface. The choice of reactor operating conditions and physical designs has a significant influence on the selectivity among different reaction pathways. The extent to which each pathway participates in the total deposition scheme is a function of reactor geometry, operating parameters, and the degree of precursor mixing as determined by the design of gas delivery systems. The first part of this thesis research aims to validate gallium nitride growth kinetics. A detailed chemistry model is developed to study the interplay between the transport of reactants, adduct formation chemistry, and deposition kinetics within a MOVPE reactor showerhead system. Furthermore, the role of reactor geometry in controlling the selectivity among competing reaction pathways is explored in the context of a planetary gallium nitride radial-flow CVD system. The second part of this thesis research is to demonstrate the use of a novel approach to film uniformity control in planetary reactor systems based purely on the geometry of radial flow reactors with the mode of wafer rotation. In this multi-wafer reactor system, individual wafers rotate on a rotating susceptor in a planetary motion to reduce the effects of reactant depletion on deposition uniformity. The uniformity criterion developed for this system gives an unambiguous criterion for minimizing non-uniformity of any film property and gives physical insight into the reactor operating conditions that most influence uniformity. This technique is applied to a theoretical gallium nitride reactor system and a real industrial silicon carbide reactor system.