Characterization of plasma-surface contacts in low-pressure rf discharges using ion energy analysis and langmuir probes'

Abstract

The plasma-sruface contact in low-pressure of discharges in noble and reactive gases was studied by a combination of probe measurements and ion energy analysis at the surface. By comparing different methods, as the roost reliable density determination the integral of the second derivative of the probe curve was found. This method turned out to he not very sensitive to incomplete of filtering or compensation and even to coating of the probe. However, it depends strongly on the correct choice of the plasma potential. By comparing space potentials obtained from probes and from ion energy distributions, a most probable value can he attained that is situated between the negative minimum and the closest maximum of the1 ″(U) curve. The ion energy distributions are compared to an analytical sheath model. giving very good agreement in anab initio comparison. In plasmas depositing carbonized polymer filers, reproducible structares due to the influence of the coating air the probe characteristics can he analyzed, yielding nonlinearI (U) characteristics of the film. Using these characteristics, the film growth can be followed.