Monitoring and diagnosis of plasma etch processes

Plasma etching removes material from a silicon wafer by applying power and gases in a chamber. As material is removed from a wafer, the amount of particular chemicals given off can be measured; this technique is called emission spectroscopy and the measurements are called endpoint traces. An expert system that automatically interprets the traces has been designed and built. The system combines signal-to-symbol transformations for data abstraction and rule-based reasoning for diagnosis. The system detects problems as soon as they occur and also determines their causes