Kinetic and transport characteristics of the processes by electron impact in CH4 plasma

Nonequilibrium low-temperature plasma of CH4 is widely used to produce poly-and nanocrystalline diamond films and nanostructures. Furthermore, the CH4 plasma etching processes are carried out with zinc oxide, indium and tin, and they are used in optoelectronic devices. The development and optimization of plasma technology is impossible without a deep understanding of the mechanisms of physical and chemical processes. One effective tool for obtaining such information is simulation of a plasma.

Simulation of a plasma was carried out in one-component approximation to neutral nonexcited particles. This approach is limited by a range of conditions. Molecular dissociation of CH4 must be less than 20%. The algorithm of plasma modeling was based on the numerical solution of steady-state kinetic Boltzmann equation, without taking into account electron-electron collision and an impact of the second kind.

We have obtained a set of cross sections by electron impact for a methane molecule, which was supplemented by new experimental data on cross sections of dissociative ionization and CH4 dissociation for neutral fragments. We found that a set of cross sections being formed provides a satisfactory agreement between the calculated and experimental literature data on the drift velocity of electrons, their characteristic energy and Townsend ionization coefficient. The calculations of a distribution function of electron energy, the integral characteristics of an electron gas (average energy, reduced mobility and diffusion coefficient) and the rate constant for electron impact were carried out.

Semenova O.A.