Chemical kinetics and energy transfer in moderate pressure H-2 plasmas used in diamond MPACVD processes

A kinetic model for moderate-pressure microwave H-2 plasmas obtained in dia mond deposition reactors is presented. This model involves three groups of reactions which describe the vibrational kinetics of H-2, the chemistry of H-2 and H electronically excited states and the groundstate species kinetic s, respectively. The set of species kinetic equations resulting from this m odel, coupled to the electron Boltzmann equation and the total energy equat ion were solved under a quasi-homogenous plasma assumption. This enables th e estimation of the species densities, the electron distribution function a nd related electron properties, as well as the gas temperature. The results show that the most important ionization channel is that due to the quenchi ng of H (n = 2) excited states by H-2. The production of the H-atom is main ly due to electron impact dissociation at low microwave power density and t o thermal dissociation at high power density. A simplified physical model w hich may be used for describing the non-equilibrium H-2 plasma flow in diam ond deposition microwave plasmas reactors is also proposed.