US Patent 7373899 Plasma processing apparatus using active matching

A plasma processing apparatus having a processing chamber connected to a vacuum exhauster so that its inside pressure can be reduced by the vacuum exhauster, a gas feed unit for supplying gas into the processing chamber, a substrate electrode provided in the processing chamber and on which a sample can be placed, an RF power supply connected through a matching circuit to the substrate electrode, plasma generating means for generating plasma within the processing chamber and a voltage waveform control circuit provided within the matching circuit or between the substrate electrode and the matching circuit to flatten the voltage waveform from the RF power supply.