Plasma processing apparatus and matching method

A plasma processing apparatus comprising:

• a chamber configured to perform a plasma processing on a target substrate;
• an electrode provided in the chamber and configured to supply a radio-frequency power to the chamber for the plasma processing in the chamber;
• a radio-frequency power supply electrically connected to the electrode and configured to generate the radio-frequency power supplied to the electrode;
• and
• a matching box connected between the radio-frequency power supply and the electrode and configured to set a load impedance on a load side of the radio-frequency power supply,
• wherein the radio-frequency power supply is configured to supply one of a modulated wave and a continuous wave of the radio-frequency power to the electrode in a preceding period of two consecutive periods, and supply a remaining one of the modulated wave and the continuous wave to the electrode in a subsequent period of the two consecutive periods, wherein the continuous wave is a wave with a steady unchanged power level and the modulated wave is a wave where two power levels are alternately and periodically repeated,
• the radio-frequency power supply generates the modulated wave so that a power level of the radio-frequency power in a first sub-period of alternating first sub-period and second sub-period is higher than a power level of the radio-frequency power in the second sub-period, and
• the matching box is configured to gradually change the load impedance to a target impedance for the subsequent period by gradually changing the load impedance during a period in which the continuous wave is supplied out of the two consecutive periods,
• wherein the matching box is configured to gradually change the load impedance so that an absolute value of a reflectance coefficient of the radio-frequency power is gradually changed to a set target value for the subsequent period during the period in which the continuous wave is supplied, and
• wherein the matching box is configured to gradually and step-wise change the absolute value of the reflectance coefficient to the set target value for the subsequent period through a plurality of consecutive sub-periods during the period in which the continuous wave is is supplied,
• a time length of each of the plurality of sub-periods is set to 0.2 seconds or more, and a difference between a target value of the absolute value of the reflectance coefficient in one sub-period of any two consecutive sub-periods included in the plurality of consecutive sub-periods, and a target value of the absolute value of the reflectance coefficient in a remaining sub-period is set to or less.