An emitter piloting advisory expert system for IC emitter deposition

A description is given of the EPAS (Emitter Piloting Advisory System) expert system, which was set up at Harris Semiconductor to advise fab operators how to adjust piloting cycle time for emitters on the basis of knowledge extracted from the most experienced engineer. EPAS consists of an input filter to validate the input parameter values, a knowledge base containing all the knowledge extracted from the expert, a learning mechanism trying to calculate dynamically for the next lot the estimated initial drive time which is closer to the one actually required, a convergence control mechanism to control the rule inference so that the result of an inference is always closer to the conclusion, a user facility module containing many Lisp-based modules developed to let the expert, engineers, and operators maintain the system by themselves, and a friendly interface to provide pleasant interactions with various kinds of users