Dynamical properties of acoustic emission by anomalous discharge in plasma processing system

We applied nonlinear time series analysis to detect the occurrence of anomalous discharge in an RF plasma processing system from observational data of acoustic emission. It was found that anomalous discharge as a local event augments specific acoustic ingredients of finite degrees of freedom, which causes a significant lowering of the degree of complexity in the acoustic signal. On the basis of this observation, a diagnostic method, unaffected by variations in the power spectral structure of acoustic emission, is proposed for detecting anomalous discharge with a single scalar measure. Confident detection of the event permits early cessation of plasma processing with anomalous discharge to avert unnecessary production of plasma-damaged microdevices.