Time resolved Langmuir probe measurements on a pulsed ICP source

Summary form only given. A commercial Langmuir probe system, which can be operated in a boxcar averaging mode, has been used to measure time resolved electron and ion densities and electron temperatures on a repetitively-pulsed inductively coupled plasma (ICP) in argon. The probe is positioned inside the ICP source region, near the RF window, in order to follow closely the temporal variation of the plasma parameters with time resolution of approximately 7 /spl mu/s. The RF power at 13.56 MHz is pulsed by applying 100% square wave modulation to the output of a RF generator which can supply up to 5 kW cw output. Modulation frequencies can be varied between 100 Hz and 30 kHz with duty cycles between 10% and 90%. Along with the Langmuir probe data, current and voltage measurements at the coil are used to measure time resolved RF power and complex impedance of the coil-plasma system with a time resolution of 0.5 /spl mu/s. A photomultiplier tube (PMT) with narrow band filter is used to monitor the time dependence of the plasma emission. At lower rep rates and/or duty cycles the ICP changes from capacitively coupled to inductively coupled during the RF pulse. During this transition a large transient is observed in the RF power, plasma emission, the electron and ion densities. Results will be presented for a variety of rep rates, duty cycles and RF powers.