Plasma processing apparatus

A plasma processing apparatus comprising:

• a radio-frequency (RF) power supply;
• a pair of plasma electrodes;
• and
• a matching box disposed between the pair of plasma electrodes and the RF power supply,
• wherein the matching box includes:
• an RF feed line through which RF power is supplied from the RF power supply,
• a ground line that is grounded,
• a first load line connected to one of the pair of plasma electrodes,
• a second load line connected to a remaining one of the pair of plasma electrodes;
• an impedance matching circuit connected to the RF feed line, the first load line, the second load line, and the ground line, and including a plurality of variable reactance elements;
• an RF sensor provided in the RF feed line and configured to detect the RF power;
• a voltage sensor including a peak detection circuit and configured to detect a peak value of a potential difference waveform that is a peak value of a potential difference, the peak detection circuit including a plurality of sensors respectively connected to the first load line, the second load line and the ground line, and
• a matching box controller configured to control the plurality of variable reactance elements by inputting detected values from the RF sensor and the voltage sensor.