AMMONIA PLASMA TREATMENT OF PTFE UNDER KNOWN PLASMA CONDITIONS

Ammonia plasmas produced in a helical resonator have been investigated using an energy-selective mass spectrometer and an r.f-compensated La ngmuir probe. The effect of processing parameters on the plasma compos ition and ion energy distributions have been examined. The dominant io n present in the plasma was found to be NH4+, which varied in concentr ation between 95% and 65%, dependent upon operating conditions. Simila rly, by relatively small variations in processing parameters it was po ssible to vary the NH3+ ion concentration between 1.7 and 31%. In addi tion, no radicals (NH2., NH. or N-.) were detected using threshold ion ization mass spectroscopy. Polytetrafluoroethylene (PTFE) samples were treated under a variety of different plasma conditions, and the chemi cal changes induced were studied by in situ XPS. Defluorination was ob served to be greater under conditions that yield low ion energies or h igh concentrations of NH3+ ions. Conditions giving rise to significant concentrations of MH(3)(+) ions result in the production of NH3+F- gr oups. Evidence is provided suggesting that NH3+ ions are much more rea ctive with PTFE surfaces than NH4(+) ions.