Measuring and controlling wafer potential in pulsed RF bias processing

摘要

Apparatus and methods are provided for monitoring a pulsed RF bias signal applied to a chuck in a processing chamber. One method includes operations for detecting voltage values of individual pulses of the pulsed RF bias voltage, and for determining the time for sampling the value of each individual detected pulse. At the sampling time for each pulse, a particular voltage value of the respective individual detected pulse is sampled and the particular voltage value is held. Each particular voltage value represents a characteristic peak-to-peak voltage value of each individual detected pulse. A feedback signal representing the characteristic peak-to-peak voltage value for a voltage envelope of one of the individual detected pulses is generated, and the voltage of the pulsed RF bias voltage signal applied to the chuck is adjusted according to a difference between the feedback signal and a desired voltage value of the pulsed RF bias voltage signal.