Comparison of microwave and lower-frequency discharges for plasma polymerization

Abstract

A plasma sustained by surface waves (SW) has been used to study the deposition rate R of hydrocarbon and fluorocarbon plasma polymer films as a function of excitation frequency f=ω/2π in the range 12–400 MHz. The SW technique allows one to vary only f while keeping constant all other parameters known to influence R, for example, power density in the plasma P. A plot of R/P at a total pressure of 200 m Torr (27 Pa) displays two plateaus, that at f<30 MHz being about five times lower than that at f≥100 MHz. This is attributed to the fact that electron energy distribution functions differ fundamentally at radio- (f≤50 MHz) and “microwave” (f≥100 MHz) frequencies, for the gas pressure range considered.