Process parameter-driven regulation of non-uniform plasma discharge behavior for optimizing heat transfer in MPCVD

Microwave plasma chemical vapor deposition (MPCVD) is widely employed for diamond growth. The surface temperature of the diamond seed is a key focus in practical engineering. A significant temperature gradient between the center and the edge, caused by non-uniform plasma discharge, has been considered as a critical factor contributing to defect formation. Regulating the operating parameters of the MPCVD reactor can effectively improve the radial uniformity of the growth surface temperature, which requires detailed modeling of fluid heat conduction and plasma radiative heat transfer. In this work, we propose a novel multiphysics-reacting flow model, which accounts for the process of plasma from transient excitation to stationary heat transfer and solves the heat conduction and radiation equations fully coupled with the Helmholtz equation, laminar flow equations, electron drift-diffusion equations, and heavy species transport equations. The simulation results and the experimental results show excellent agreement under both pure hydrogen and hydrogen-methane plasma discharges, with the surface temperature error is within 40°C. The spatial distributions of electrons, hydrogen atoms and methyl radicals are successfully predicted, which also helps validate the effectiveness of the model. Furthermore, this work provides valuable guidance on process parameters, especially power and pressure, for optimizing the uniformity of surface temperature to meet the stringent requirements for high-quality diamond growth. The model, with its general applicability, can be applied to any MPCVD reactor.