Study of Gas Phase Chemistry in Chemical Vapor Deposition Microwave Plasma Reactors for Diamond Growth

Chemical vapor deposition (CVD) is used for diamond synthesis with applications spanning electronics and quantum sensing. CH4 diluted in H2 is typically used as feedstock. We have recently applied ab-initio quantum chemistry methods to develop a comprehensive quantitative model of the surface kinetics of diamond growth [1]. This model requires as input data the concentrations of active species involved in the growth, namely, CH3, C2H2, H2 molecules, H atoms, and, in the case of phosphorous doping of diamond, phosphorous-containing species near the substrate surface. The goal of this work is to develop such a model for self-consistent simulations of microwave resonant cavity reactors for the diamond growth. Our self-consistent model includes modules for neutral chemistry and gas flow, electromagnetics, and weakly-ionized nonequilibrium plasma physics and chemistry. The latter is based on non-Maxwellian electron energy distribution function and approximate calculation of vibrational energy balance. It accounts for electron and neutral gas heating. Because this problem is quite complex numerically and there is a strong interdependency between the mentioned modules, these modules were initially validated separately for simpler problems. The modules are coupled together using global iterations. For the model validation, we solve separately for electromagnetic field in an empty cavity, consider pyrolysis of PH₃/CH₄/H₂ mixture, solve for viscous gas flow through a pipe, and calculate electron energy distribution function by BOLSIG+ [2] and compare it with previous simulations [3].

[1] Yu. Barsukov, et al. , Diamond and Related Materials 149, 111577 (2024).

[2] www.bolsig.laplace.univ-tlse.fr

[3] E. J. D. Mahoney et al., J. Phys. Chem. A, 122, 8286−8300 (2018).