PLASMA PROCESSING APPARATUS AND METHOD FOR CONTROLLING SOURCE FREQUENCY OF SOURCE RADIO-FREQUENCY POWER

A plasma processing apparatus includes a chamber, a substrate support, a radio-frequency power supply, and a bias power supply. The radio-frequency power supply generates source radio-frequency power to generate plasma in the chamber. The bias power supply provides a pulse of bias energy to a bias electrode in each of a plurality of pulse periods. The radio-frequency power supply sets, based on a change in a degree of reflection of the source radio-frequency power, a source frequency of the source radio-frequency power in each of a plurality of phase periods in each of a plurality of overlap periods. Each of the plurality of overlap periods overlaps a corresponding pulse period of the plurality of pulse periods. The degree of reflection is identified with the source frequency being set differently in identical phase periods in two or more preceding overlap periods.