Patent ID: 9736921
Date: 2017-08-15
CPC Classifications: H01J,H05H

Claim:
1. A method for impedance matching comprising: providing a plasma processing apparatus which comprises: a processing vessel; a first electrode and a second electrode disposed with a space therebetween within the processing vessel; a first high frequency power supply configured to output a high frequency power for plasma generation; a second high frequency power supply configured to output a high frequency power for ion attraction; a first power feed line configured to connect the first electrode or the second electrode to the first high frequency power supply; a second power feed line configured to connect the second electrode to the second high frequency power supply; a first matching device configured to adjust a load impedance of the first high frequency power supply; and a second matching device configured to adjust a load impedance of the second high frequency power supply; starting an output of a modulated high frequency power, which is set such that a power of the modulated high frequency power in a second period is smaller than a power of the modulated high frequency power in a first period, from one high frequency power supply of the first high frequency power supply and the second high frequency power supply, the first period and the second period being repeated alternately; adjusting, by one matching device of the first matching device and the second matching device which corresponds to the one high frequency power supply, a reactance of a variable reactance element of the one matching device such that the load impedance of the one high frequency power supply approximates to a matching point; acquiring a first moving average value and a second moving average value by a power supply controller corresponding to the one high frequency power supply, the first moving average value being a moving average value of the load impedance of the one high frequency power supply in a first sub-period from a start point to a preset point of each first period after the adjusting of the reactance of the variable reactance element of the one matching device, and the second moving average value being a moving average value of the load impedance of the one high frequency power supply in a second sub-period from the preset point to an end point of each first period after the adjusting of the reactance of the variable reactance element of the one matching device; and setting, by the power supply controller corresponding to the one high frequency power supply, after the first moving average value and the second moving average value are acquired, a frequency of the modulated high frequency power output from the one high frequency power supply, in each of the first sub-period and the second sub-period such that the load impedance of the one high frequency power supply in the first sub-period, which is estimated from the first moving average value, and the load impedance of the one high frequency power supply in the second sub-period, which is estimated from the second moving average value, approximate to the matching point.