Time-resolved current and voltage measurements on a pulsed rf inductively coupled plasma

Time resolved current and voltage measurements have been made on a pulsed r adio frequency (rf) inductively coupled plasma (ICP) at 13.56 MHz in argon. Measurements were made on the rf coil using a high-voltage probe, a Rogows ki current probe, and a high-performance digital oscilloscope. Relative pha se information was also obtained so that time resolved rf power measurement s could be made. Due to the inductive nature of the load, measurement of th e phase had to be: better than 0.6 mrad at 13.56 MHz in order that the powe r measurements were accurate to 10%. This accuracy in phase measurement was achieved by careful positioning of the probes and by establishing accurate phase calibration procedures. The power was calculated by three methods: d iscrete Fourier transform, integral of the current voltage product over N p eriods, and least-squares fits of a sine wave to the measured data. Time-re solved measurements of the system complex impedance, power loss in the ICP planar coil, and the actual amount of rf power delivered to the plasma were made, These measurements give details during plasma breakdown and show the transition from capacitive to inductive discharge, The results are compare d with both time-resolved plasma emission and time-resolved Langmuir probe measurements.