US Patent 11990318 Filter circuit

There is provided a filter circuit provided in a plasma processing device for processing a substrate using plasma generated using power of a first frequency of 4 MHz or more and power of a second frequency of 100 Hz or more and less than 4 MHz. The filter circuit comprises: a first filter provided in a wiring between a conductive member provided in the plasma processing device and a power supply configured to supply power of a third frequency of less than 100 Hz or control power which is direct-current (DC) power, to the conductive member; and a second filter provided in a wiring between the first filter and the power supply.