Foreseeing and active-suppression of anomalous discharge in plasma processing equipment by in-situ monitoring of plasma state using viewing port probe

We demonstrate for the first time the foreseeing and active suppression of anomalous discharge in a plasma processing equipment. The foreseeing of anomalous discharge is realized by monitoring plasma state using a newly developed viewing-port probe. We have found that a foreseeing signal indicating a slight change in plasma potential appears prior to the occurrence of the anomalous discharge. The time interval between the foreseeing signal and the occurrence of the abnormal discharge is several tens millisecond, which allows to build-up a electric system to control the plasma state. The active suppression of anomalous discharge is demonstrated using a reactive ion-etching system by controlling the applied voltage of electrostatic chuck of wafer stage.