Comparison of microwave and lower frequency discharges for plasma polymerization

Abstract

A plasma sustained by electromagnetic surface waves (SW’s) has been used to study the deposition rate R of hydrocarbon and fluorocarbon plasma polymer films as a function of the applied field frequency f 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 P in the plasma. A plot of R/P at a total pressure of 200 mTorr (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 and microwave frequencies, for the gas pressure range considered.