Influence of the excitation frequency on CH 4 /H/H 2 plasmas for diamond film deposition: electron energy distribution function and atomic hydrogen concentration

The influence of the excitation frequency f = ω/2π of the applied electric field on the period average electron energy distribution function (EEDF) and on the atomic hydrogen concentration found near the deposited diamond films (substrate) and in the bulk of CH4(5%)/H/H2 plasmas produced in RF and MW discharges is estimated. This is done through the solution, as a function of the reduced effective electric field, of a stationary homogeneous electron Boltzmann equation (EBE) and the solution, in terms of the atomic hydrogen mole fraction, of a simple kinetic model for the plasma mechanisms underlying the production and loss of atomic hydrogen. The physical basics underlying the approach followed to solve the EBE, including discussion of EEDF time-modulation effects, are discussed in the light of recent results by Loureiro (1993 Phys. Rev. E 47 1262) on time-dependent kinetics of pure H2 plasmas. Correlations are established between the results, obtained under various discharge conditions, from plasma-enhanced chemical vapour deposition (PECVD) experiments of diamond-like carbon (DLC) and diamond thin films, and the calculated EEDF, atomic hydrogen concentrations (in the plasma and near the substrate) and mechanisms underlying the production and loss of atomic hydrogen in the plasma.

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