Sheath dynamics in plasma immersion ion implantation

Time-resolved Langmuir probe measurements of the sheath dynamics and ion flux measurements in static and dynamic modes have been made. In the case of supersonic moving sheaths the experimental data qualitatively shows that the presheath is suppressed. The results of the sheath measurements are compared to a modified model description for the non-stationary sheath during plasma immersion implantation, which includes the suppression of the presheath at supersonic velocity of the plasma boundary. Analytical formulas are given for planar, cylindrical and spherical geometry. Reasonable agreement is obtained for spherical geometry according to a dome-like boundary around a small, flat substrate.