Patent ID: 9663858
Date: 2017-05-30
CPC Classifications: C23C,H01J

Claim:
1. A plasma processing apparatus of generating plasma by high frequency discharge of a processing gas within a decompression processing vessel that accommodates therein a processing target object, which is loaded into and unloaded from the processing vessel, and performing a process on the processing target object within the processing vessel under the plasma, the plasma processing apparatus comprising: a first high frequency power supply configured to output a first high frequency power; a first high frequency transmission line configured to transmit the first high frequency power outputted from the first high frequency power supply to a first electrode provided within or in the vicinity of the processing vessel; a first matching device, having a first variable reactance element and a first impedance sensor provided on the first high frequency transmission line, configured to control a reactance of the first variable reactance element such that a first load impedance measurement value outputted from the first impedance sensor is equal to or approximate to a first matching point corresponding to an output impedance of the first high frequency power supply; a first high frequency power modulation unit configured to pulse-modulate an output of the first high frequency power supply with a first pulse such that a first period during which the first high frequency power is turned on or has a first level and a second period during which the first high frequency power is turned off or has a second level lower than the first level are alternately repeated at a regular frequency; a second high frequency power supply configured to output a second high frequency power; a second high frequency transmission line configured to transmit the second high frequency power outputted from the second high frequency power supply to the first electrode or a second electrode provided within or in the vicinity of the processing vessel; a second matching device, having a second variable reactance element and a second impedance sensor provided on the second high frequency transmission line, configured to control a reactance of the second variable reactance element such that a second load impedance measurement value outputted from the second impedance sensor is equal to or approximate to a second matching point corresponding to an output impedance of the second high frequency power supply; and a second high frequency power modulation unit configured to pulse-modulate an output of the second high frequency power supply with a second pulse by alternately repeating a third period during which the second high frequency power is turned on or has a third level and a fourth period during which the second high frequency power is turned off or has a fourth level lower than the third level at a regular frequency lower than a frequency of the first pulse, wherein the first impedance sensor calculates an average value of the load impedance by using a single cycle of the second pulse as a basic cycle, and outputs the first load impedance measurement value based on the average value of the load impedance, and the second impedance sensor calculates an average value of the load impedance by using the single cycle of the second pulse as a basic cycle, and outputs the second load impedance measurement value based on the average value of the load impedance, and wherein the first impedance sensor comprises: a first cycle-average-value calculating circuit configured to sample voltage detection signals and electric current detection signals corresponding to the first high frequency power on the first high frequency transmission line with a preset sampling frequency during a first monitoring time set in either one of the first period and the second period in a single cycle of the first pulse and calculate an average value of the voltage detection signals and the electric current detection signals for the single cycle; a preposition-moving-average-value calculating circuit configured to calculate, by setting the single cycle of the second pulse as a moving range, a primary moving average value of multiple consecutive average values of the voltage detection signals for the single cycle and multiple consecutive average values of the electric current detection signals for the single cycle obtained from the first cycle-average-value calculating circuit; a first main-moving-average-value calculating circuit configured to calculate, by setting an AN a first load impedance calculating circuit configured to calculate the first load impedance measurement value based on the secondary moving average values of the voltage detection signals and the electric detection signals obtained from the first moving-average-value calculating circuit, wherein the AN