Macroscopic investigation of reaction rates yielding plasma polymer deposition

Plasma polymers cover a broad range from organic to hard coatings. In order to investigate the influencing factors yielding plasma polymer deposition, a macroscopic relation between the deposition rate R-m and the energy input W/F is derived based on reaction rates following a quasi-Arrhenius approach. An activation barrier for a specific plasma chemical reaction pathway is thus assumed. As an important finding, it can be shown that the pre-factor in the quasi-Arrhenius equation is independent of the energy input for the generation of film-forming species and their flux towards a substrate. For a constant sticking probability, it follows that also the mass deposition rate solely varies with the exponential term of the quasi-Arrhenius equation. The influencing factors in plasma polymerization enclosed in the pre-factor are found to be (i) the reaction rate for the plasma chemical reaction pathway following Arrhenius behaviour, (ii) the power coupling to the plasma governed by the electron energy distribution function, (iii) the monomer gas flow rate, (iv) the deposition area, (v) the molecular mass of the film-forming species and (vi) their sticking probability, which also includes their transport to the substrate. Different plasma polymerization processes are discussed in order to examine the derived influencing factors.