A plasma processing method performed in a plasma processing apparatus,
- wherein the plasma processing apparatus comprises:
- a processing vessel;
- a gas supply system configured to supply a gas into the processing vessel;
- a first electrode and a second electrode which are arranged such that a space within the processing vessel is provided therebetween;
- a first high frequency power supply configured to output a first high frequency power for plasma generation;
- a second high frequency power supply configured to output a second high frequency power for ion attraction;
- a first power feed line configured to connect the first high frequency power supply to the first electrode or the second electrode;
- a second power feed line configured to connect the second high frequency power supply to the second electrode;
- a first matching device configured to adjust a load impedance of the first high frequency power supply;
- a second matching device configured to adjust a load impedance of the second high frequency power supply;
- a first device configured to control the gas supply system;
- and
- a second device configured to obtain a parameter which includes at least one of the load impedance, a load resistance and a load reactance of the first high frequency power supply, and a reflection wave coefficient of the first high frequency power,
- wherein the plasma processing method comprises:
- first processes of generating plasma of a first gas within the processing vessel;
- and
- second processes of generating plasma of a second gas which contains a gas different from a gas contained in the first gas within the processing vessel, the second processes being performed alternately with the first processes,
- wherein, in each of the first processes, the first gas is supplied into the processing vessel from the gas supply system, and the first high frequency power is supplied to the first electrode or the second electrode from the first high frequency power supply,
- in each of the second processes, the first high frequency power is supplied to the first electrode or the second electrode from the first high frequency power supply continuously from a first process, which is performed just before the corresponding second process, among the first processes, and
- each of the second processes comprises:
- applying a gas switching signal to the gas supply system from the first device to switch a gas to be supplied into the processing vessel from the first gas to the second gas;
- and
- instructing, by the second device, the second high frequency power supply to start a supply of the second high frequency power to the second electrode when the parameter exceeds a threshold value after the gas switching signal is applied to the gas supply system.