Patent ID: 8303763
Filing Date: 2012-11-06
Classification: H01J,H01L

Abstract:
1. A method for monitoring and adjusting a pulsed RF bias voltage signal to be applied to a chuck in a plasma chamber for processing a semiconductor wafer, the chuck being configured to mount the semiconductor wafer for processing, the method comprising: detecting voltage values of individual pulses of the pulsed RF bias voltage applied to the chuck; determining a sampling time at which to sample a voltage value of each of the individual detected pulses; at the sampling time for each of the individual detected pulses, sampling a particular voltage value of the respective individual detected pulse and holding the particular voltage value, each particular voltage value representing a characteristic peak-to-peak voltage value of each respective individual detected pulse, wherein the sampling time corresponds to a time when a characteristic peak-to-peak voltage value occurs in each individual detected pulse, the characteristic peak-to-peak voltage representing a maximum peak-to-peak voltage of an envelope of each individual detected pulse; generating a feedback signal representing the characteristic peak-to-peak voltage value for a voltage envelope of one of the individual detected pulses; and adjusting the voltage of the pulsed RF bias voltage signal applied to the chuck according to a difference between the feedback signal and a desired voltage value of the pulsed RF bias voltage signal to hold electrical characteristics of the plasma steady during processing to compensate for a variation of an impedance presented to the chuck.