Patent ID: 7822565

Claim:
A method for monitoring electrical characteristics of RF power applied to a plasma load in a plasma chamber comprising: sensing electrical characteristics of RF power that is generated by an RF generator to obtain RF signals, the RF signals including information indicative of electrical characteristics at a plurality of particular ones of frequencies that fall within a frequency range, wherein the plurality of particular ones of frequencies include at least: a fundamental frequency of the RF power; a second harmonic of the fundamental frequency of the RF power; and a third harmonic of the fundamental frequency of the RF power; digitally sampling the RF signals to obtain a stream of digital RF signals, the digital RF signals including the information indicative of electrical characteristics at the plurality of particular ones of frequencies; and successively performing, for each of the plurality of particular ones of frequencies, a single-frequency transform on the information indicative of electrical characteristics, from a time domain into a frequency domain so as to obtain a quantity of information that enables an association to be made between the electrical characteristics at the particular ones of frequencies and plasma parameters that are indicative of characteristics of material that is being processed in the plasma chamber.