US Patent 9099503 Plasma processing apparatus

In a plasma etching apparatus, a first high frequency for plasma generation and a second high frequency for ion attraction are respectively applied from two high frequency supplies to a susceptor. Further, DC voltage is applied from a variable DC power supply to an upper electrode via a filter circuit. An annular DC ground part attached to an upper side surface of the susceptor is connected to a filter circuit. This filter circuit allows a specific frequency component of the intermodulation distortion generated in a plasma by a series resonant to selectively flow to a ground line.