Plasma processing apparatus and end point detection method

A plasma processing apparatus comprising:

• a chamber having a stage inside on which a substrate is placeable,
• an electrode disposed in the chamber,
• a sensor provided on the electrode or on an interconnect connected to the electrode, and configured to measure either a voltage or a current,
• a gas supply configured to supply a gas to be formed into a plasma into the chamber,
• a power supply configured to supply, to the chamber, periodic power for forming the gas supplied into the chamber into the plasma, a power level of the periodic power being changed for each period during one cycle, and
• circuitry configured to:
• detect an end point of a first etching based on at least one of a voltage, a current, or a phase difference between the voltage or the current measured by the sensor at a first timing during the one cycle, and
• detect an end point of a second etching based on at least one of a voltage, a current, or a phase difference between the voltage or the current measured by the sensor at a second timing different from the first timing during the one cycle.