Plasma processing apparatus and operational method thereof
A plasma processing apparatus includes: a detector configured to detect a change in an intensity of light emission from plasma formed inside a processing chamber; and a unit configured to adjust conditions for forming the plasma or processing a wafer arranged inside the processing chamber using an output from the detector, wherein the detector detects a signal of the intensity of light emission at plural time instants before an arbitrary time instant during processing, and wherein the adjusting unit removes the component of a temporal change of a long cycle of the intensity of light emission from this detected signal and detects the component of a short temporal change of the intensity of light emission, and adjusts the conditions for forming the plasma or processing a wafer arranged inside the processing chamber based on the short temporal change of the detected intensity of light emission.
1. A method for operating a plasma processing apparatus comprising a processing chamber arranged inside a vacuum vessel; a detector configured to detect a change in an intensity of light emission from the processing chamber during processing of a wafer arranged inside the processing chamber by using plasma generated inside the processing chamber, the method comprising the steps of:
detecting, by the detector, a first signal of the intensity of light emission at a plurality of time instants before an arbitrary time instant during processing of the wafer;
reducing noise components by using a Kalman filter from the first signal indicating the intensity of light emission from the inside of the processing chamber which is detected by the detector at the plurality of time instants before the arbitrary time instant during processing;
correcting said first signal indicating the intensity of light emission at the plurality of time instants before the arbitrary time instant during processing from which is reduced the noise components, by using a Kalman smoother to correct the first signal of one of the plurality of time instants using another first signal of time instants which is delayed from said one time instant;
detecting a baseline component of the first signal by using a Kalman filter on the first signal from which is reduced the noise components and is corrected by using the Kalman smoother, the baseline component of the first signal indicating changes of the intensity of light at the plurality of time instants before the arbitrary time instant during processing of the wafer which occurs with a cycle longer than a predetermined term in the first signal;
detecting a second signal by reducing a baseline component of the first signal from the first signal from which is reduced the noise components and is corrected, the baseline component indicating changes of an intensity of light occurring with a cycle which is longer than a predetermined term in the first signal; and
adjusting the conditions for generating the plasma or processing the wafer arranged inside the processing chamber based on the second signal.