Investigation of afterglow produced by a pulsed inductively coupled plasma source

Summary form only given, as follows. Time-resolved Langmuir probe measurements have been made on a repetitively-pulsed, low pressure, planar inductively coupled plasma (ICP) source. Argon (as a model atomic gas) and nitrogen (as a model molecular gas) were used in generating the plasma. The pulsed operation is divided into three distinct regions: the breakdown (or ignition), mid pulse (quasi-steady state), and afterglow (pulse off). In this work, the afterglow region was investigated and the time dependence of typical plasma parameters, such as the electron temperature and plasma density, was studied as a function of the experimental variables. The experimental variables involved are the rf pulse parameters (i.e. pulse period, duty cycle, and frequency), rf power levels, and gas pressure. The Langmuir probe system, operated in boxcar averaging mode, is synchronized with the rf pulse in time and has a time resolution of approximately 7 /spl mu/s. The probe can be spatially scanned along the axial direction in the center of the ICP source from 0 to 25 cm from the alumina rf window. In this way, the time dependence of the plasma parameters can be determined as a function of axial position from the rf window. For given set of experimental variables, each plasma parameter studied was observed to decay differently within, for example, the early part and later part of the afterglow region. The decay rates of the various plasma parameters, seen in the afterglow region, will be presented and interpreted.