Impedance monitoring system and method

An apparatus for and method of measuring impedance in a capacitively coupled plasma reactor system. The apparatus includes a high-frequency RF source in electrical communication with an upper electrode. A first high-pass filter is arranged between the upper electrode and the high-frequency RF source, to block low-frequency, high-voltage signals from the electrode RF power source from passing through to the impedance measuring circuit A current-voltage probe is arranged between the high-frequency source and the high-pass filter, and is used to measure the current and voltage of the probe signal with and without the plasma present. An amplifier is electrically connected to the current-voltage probe, and a data acquisition unit is electrically connected to the amplifier. A second high-pass filter is electrically connected to a lower electrode and to ground, so as to complete the isolation of the high-frequency circuit of the impedance measurement apparatus from the low-frequency, high-voltage circuit of the capacitively coupled plasma reactor system. A method of measuring the plasma impedance using the apparatus of the present invention is also disclosed.