One-point numerical modeling of microwave plasma chemical vapor deposition diamond deposition reactors

Abstract

As a first step to carrying out two-dimensional simulations of microwave reactors we have performed very detailed one-point calculations using a Boltzmann code to determine the distribution of electron energy, detailed time dependent ion chemistry, and detailed neutral time dependent hydrocarbon chemistry. Modeling a microwave chemical vapor deposition reactor requires accurate determination of the electron energy distribution generated by the microwave electromagnetic fields and their interaction with the neutral gas because the distribution is highly nonthermal and the important dissociation and ionization rates are determined by the small fraction of high energy electrons. The electrons lose most of their energy to vibrational excitation of the gas which heats it through vibrational–translational energy exchange. The one-point model takes account in an approximate way of the effects of mass diffusion and thermal conduction to the reactor substrate and walls. We show time dependent calculations of the rise in gas temperature, the evolution of ion species, and the neutral species development in the pressure range of 40–110 Torr characteristic of conditions in an ASTeX reactor. We vary the input power and the input methane and oxygen fractions and compare with experimental measurements in the reactor.